#include "fesa/io/abaqus/domain_mapper.h"

#include <algorithm>
#include <array>
#include <cerrno>
#include <cmath>
#include <cstdlib>
#include <limits>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include "fesa/core/ascii.h"
#include "fesa/math/vector3.h"
#include "fesa/model/shell_geometry.h"
#include "fesa/model/source_target_resolver.h"

namespace fesa {
namespace {

std::vector<std::string> WithoutTrailingEmpty(std::vector<std::string> fields) {
  while (!fields.empty() && fields.back().empty()) {
    fields.pop_back();
  }
  return fields;
}

struct RawNode {
  std::int64_t label;
  std::string label_text;
  std::array<double, 3> coordinates;
  SourceLocation location;
};

struct RawElement {
  enum class Type { kB33, kS4, kS4r };

  std::int64_t label;
  std::string label_text;
  Type type;
  std::vector<std::int64_t> node_labels;
  SourceLocation location;
};

enum class ElementFamily { kBeam, kShell };

struct RawSet {
  std::string name;
  std::vector<std::int64_t> members;
  SourceLocation location;
};

struct RawSection {
  std::string element_set_name;
  std::string material_name;
  std::array<double, 5> properties;
  std::array<double, 3> first_axis;
  std::vector<std::array<double, 2>> section_points;
  SourceLocation location;
};

struct RawShellSection {
  std::string element_set_name;
  std::string material_name;
  double thickness;
  SourceLocation location;
};

struct RawPart {
  std::string name;
  SourceLocation location;
  std::vector<RawNode> nodes;
  std::vector<RawElement> elements;
  std::vector<RawSet> node_sets;
  std::vector<RawSet> element_sets;
  std::vector<RawSection> sections;
  std::vector<RawShellSection> shell_sections;
};

struct RawInstance {
  std::string name;
  std::string part_name;
  SourceLocation location;
};

struct RawAssemblySet {
  bool is_node_set;
  std::string name;
  std::string instance_name;
  std::vector<std::int64_t> members;
  SourceLocation location;
};

struct RawMaterial {
  std::string name;
  double youngs_modulus{0.0};
  double poisson_ratio{0.0};
  bool has_elastic{false};
  SourceLocation location;
  SourceLocation elastic_location;
};

struct RawStep {
  SourceLocation location;
  bool has_static{false};
  std::array<double, 4> static_values{};
  std::vector<BoundaryCondition> boundaries;
  std::vector<NodalLoad> loads;
};

struct MappingFailure {
  FailureCategory category;
  Diagnostic diagnostic;
};

/// @brief Builds one complete Domain candidate while retaining source identity.
/// @note The candidate is committed only after all blocks and cross-references
/// have been validated.
class MappingContext {
 public:
  explicit MappingContext(const ParsedInput& input) : input_{input} {}

  Result<Domain> Run() {
    ParseBlocks();
    if (!failure_) {
      FinalizeModel();
    }
    if (failure_) {
      return Result<Domain>::Failure(Status::Failure(
          failure_->category, {std::move(failure_->diagnostic)}));
    }
    SortDiagnostics(definition_.warnings);
    return Domain::Create(std::move(definition_));
  }

 private:
  const KeywordParameter* Parameter(const KeywordBlock& block,
                                    std::string_view name) const {
    const auto found =
        std::find_if(block.parameters.begin(), block.parameters.end(),
                     [name](const KeywordParameter& candidate) {
                       return candidate.name == name;
                     });
    return found == block.parameters.end() ? nullptr : &*found;
  }

  bool Fail(FailureCategory category, std::string code,
            const SourceLocation& location, std::string keyword,
            std::string entity_identity, std::string message) {
    if (!failure_) {
      failure_ = MappingFailure{
          category,
          {Severity::kError, std::move(code), location, std::move(keyword),
           std::move(entity_identity), std::move(message)}};
    }
    return false;
  }

  bool InputFailure(std::string code, const SourceLocation& location,
                    std::string keyword, std::string entity_identity,
                    std::string message) {
    return Fail(FailureCategory::kInput, std::move(code), location,
                std::move(keyword), std::move(entity_identity),
                std::move(message));
  }

  bool ModelFailure(std::string code, const SourceLocation& location,
                    std::string keyword, std::string entity_identity,
                    std::string message) {
    return Fail(FailureCategory::kModel, std::move(code), location,
                std::move(keyword), std::move(entity_identity),
                std::move(message));
  }

  bool InvalidKeywordLocation(const KeywordBlock& block, std::string message) {
    return InputFailure("invalid-keyword-location", block.location,
                        block.canonical_name, "", std::move(message));
  }

  bool ValidateParameters(const KeywordBlock& block,
                          const std::vector<std::string_view>& allowed) {
    std::set<std::string> seen;
    for (const auto& candidate : block.parameters) {
      if (!seen.insert(candidate.name).second) {
        return InputFailure("duplicate-entity", block.location,
                            block.canonical_name, candidate.name,
                            "A keyword parameter may be declared only once.");
      }
      if (std::find(allowed.begin(), allowed.end(), candidate.name) ==
          allowed.end()) {
        return InputFailure(
            "invalid-keyword-parameter", block.location, block.canonical_name,
            candidate.name,
            "The keyword parameter is outside the approved subset.");
      }
    }
    return true;
  }

  const std::string* RequiredParameterValue(const KeywordBlock& block,
                                            std::string_view name) {
    const auto* found = Parameter(block, name);
    if (found == nullptr || !found->value || found->value->empty()) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, std::string{name},
                   "The keyword requires a non-empty parameter value.");
      return nullptr;
    }
    return &*found->value;
  }

  bool RequireNoData(const KeywordBlock& block) {
    if (!block.data.empty()) {
      return InputFailure("invalid-data-arity", block.data.front().location,
                          block.canonical_name, "",
                          "This keyword does not accept data rows.");
    }
    return true;
  }

  bool ParseInteger(const std::string& text, std::int64_t& value,
                    const SourceLocation& location, const std::string& keyword,
                    bool positive) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const long long parsed = std::strtoll(text.c_str(), &end, 10);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        (positive && parsed <= 0)) {
      return InputFailure(
          "invalid-numeric-value", location, keyword, text,
          "The field must be a valid positive base-10 integer.");
    }
    value = static_cast<std::int64_t>(parsed);
    return true;
  }

  bool ParseDouble(const std::string& text, double& value,
                   const SourceLocation& location, const std::string& keyword) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        !std::isfinite(parsed)) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "The field must be a finite floating-point value.");
    }
    value = parsed;
    return true;
  }

  bool ParseModelDouble(const std::string& text, double& value,
                        const SourceLocation& location,
                        const std::string& keyword,
                        const std::string& diagnostic_code,
                        const std::string& message) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (end != text.c_str() + text.size()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "The field must use floating-point syntax.");
    }
    if (errno == ERANGE || !std::isfinite(parsed)) {
      return ModelFailure(diagnostic_code, location, keyword, text, message);
    }
    value = parsed;
    return true;
  }

  bool ContainsName(const std::vector<RawPart>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawPart& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsName(const std::vector<RawInstance>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawInstance& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsName(const std::vector<RawMaterial>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawMaterial& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsSetName(const std::vector<RawSet>& sets,
                       const std::string& name) const {
    const auto matches = [&name](const RawSet& set) {
      return AsciiCaseInsensitiveEquals(set.name, name);
    };
    return std::any_of(sets.begin(), sets.end(), matches);
  }

  bool ContainsAssemblySetName(bool node_set, const std::string& name) const {
    return std::any_of(assembly_sets_.begin(), assembly_sets_.end(),
                       [node_set, &name](const RawAssemblySet& set) {
                         return set.is_node_set == node_set &&
                                AsciiCaseInsensitiveEquals(set.name, name);
                       });
  }

  void ParseBlocks() {
    definition_.source_path = input_.source_path;
    definition_.source_content_identity = input_.source_content_identity;

    for (std::size_t index = 0U; index < input_.blocks.size() && !failure_;
         ++index) {
      const auto& block = input_.blocks[index];
      if (in_instance_) {
        ParseInstanceBlock(block);
      } else if (current_part_) {
        ParsePartBlock(block);
      } else if (in_assembly_) {
        ParseAssemblyBlock(block);
      } else if (in_step_) {
        ParseStepBlock(block);
      } else {
        ParseTopLevelBlock(block, index);
      }
    }

    if (!failure_ &&
        (current_part_ || in_assembly_ || in_instance_ || in_step_)) {
      const auto location = input_.blocks.empty()
                                ? SourceLocation{input_.source_path, 0U}
                                : input_.blocks.back().location;
      InputFailure("unclosed-keyword-block", location, "", "",
                   "A part, assembly, instance, or step block was not closed.");
    }
  }

  void ParseTopLevelBlock(const KeywordBlock& block, std::size_t index) {
    if (step_seen_) {
      if (block.canonical_name == "STEP") {
        ParseStepStart(block);
      } else {
        InvalidKeywordLocation(
            block, "The sole analysis step must be the final top-level block.");
      }
      return;
    }

    if (block.canonical_name != "ELASTIC") {
      material_eligible_.reset();
    }
    pending_section_.reset();
    active_output_ = false;

    if (block.canonical_name == "HEADING") {
      if (index != 0U || heading_seen_ || !ValidateParameters(block, {})) {
        if (!failure_) {
          InputFailure("invalid-keyword-location", block.location,
                       block.canonical_name, "",
                       "HEADING is optional only as the first keyword.");
        }
        return;
      }
      heading_seen_ = true;
      for (std::size_t row = 0U; row < block.data.size(); ++row) {
        if (row != 0U) {
          definition_.heading.push_back('\n');
        }
        for (std::size_t field = 0U; field < block.data[row].fields.size();
             ++field) {
          if (field != 0U) {
            definition_.heading.push_back(',');
          }
          definition_.heading += block.data[row].fields[field];
        }
      }
      return;
    }
    if (block.canonical_name == "PREPRINT") {
      if (!RequireNoData(block)) {
        return;
      }
      AddIgnoredWarning(block);
      return;
    }
    if (block.canonical_name == "PART") {
      ParsePartStart(block);
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      ParseAssemblyStart(block);
      return;
    }
    if (block.canonical_name == "MATERIAL") {
      ParseMaterial(block);
      return;
    }
    if (block.canonical_name == "ELASTIC") {
      ParseElastic(block);
      return;
    }
    if (block.canonical_name == "BOUNDARY") {
      if (!assembly_seen_ || materials_.empty()) {
        InvalidKeywordLocation(
            block, "Model boundary data follows the assembly and materials.");
        return;
      }
      model_boundary_seen_ = true;
      ParseBoundary(block, model_boundaries_);
      return;
    }
    if (block.canonical_name == "STEP") {
      ParseStepStart(block);
      return;
    }
    if (block.canonical_name == "END PART" ||
        block.canonical_name == "END ASSEMBLY" ||
        block.canonical_name == "END INSTANCE" ||
        block.canonical_name == "END STEP") {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "The closing keyword has no matching open block.");
      return;
    }
    RejectUnknown(block);
  }

  void ParsePartStart(const KeywordBlock& block) {
    if (assembly_seen_ || !materials_.empty() || model_boundary_seen_) {
      InvalidKeywordLocation(
          block, "All part blocks must precede the sole assembly block.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    if (name == nullptr) {
      return;
    }
    if (ContainsName(parts_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Part names are unique under case-insensitive lookup.");
      return;
    }
    parts_.push_back({*name, block.location, {}, {}, {}, {}, {}, {}});
    current_part_ = parts_.size() - 1U;
    part_elements_seen_ = false;
    part_sets_seen_ = false;
    part_sections_seen_ = false;
    beam_section_context_active_ = false;
  }

  void ParsePartBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END PART") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      const RawPart& part = parts_[*current_part_];
      const bool shell_part = model_element_family_ == ElementFamily::kShell;
      if (part.nodes.empty() || part.elements.empty() ||
          (!shell_part && part.sections.empty())) {
        InvalidKeywordLocation(block,
                               "A part closes only after node, element, "
                               "and matching section blocks.");
        return;
      }
      current_part_.reset();
      pending_section_.reset();
      beam_section_context_active_ = false;
      return;
    }
    if (block.canonical_name == "PART") {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "Nested part blocks are not supported.");
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "An assembly cannot be nested in a part.");
      return;
    }

    RawPart& part = parts_[*current_part_];
    if (block.canonical_name == "NODE") {
      beam_section_context_active_ = false;
      if (part_elements_seen_ || part_sets_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "NODE blocks must precede element, set, and section blocks.");
        return;
      }
      pending_section_.reset();
      ParseNodes(block, part);
    } else if (block.canonical_name == "ELEMENT") {
      beam_section_context_active_ = false;
      if (part.nodes.empty() || part_sets_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(block,
                               "ELEMENT blocks follow at least one NODE block "
                               "and precede sets and sections.");
        return;
      }
      pending_section_.reset();
      ParseElements(block, part);
      part_elements_seen_ = !failure_;
    } else if (block.canonical_name == "NSET") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "Part sets follow element blocks and precede beam sections.");
        return;
      }
      pending_section_.reset();
      ParseSet(block, true, part);
      part_sets_seen_ = !failure_;
    } else if (block.canonical_name == "ELSET") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "Part sets follow element blocks and precede beam sections.");
        return;
      }
      pending_section_.reset();
      ParseSet(block, false, part);
      part_sets_seen_ = !failure_;
    } else if (block.canonical_name == "BEAM GENERAL SECTION") {
      if (!part_elements_seen_) {
        InvalidKeywordLocation(
            block,
            "BEAM GENERAL SECTION follows the part mesh and optional sets.");
        return;
      }
      if (model_element_family_ == ElementFamily::kShell) {
        InputFailure(
            "unsupported-mixed-element-model", block.location,
            block.canonical_name, "",
            "Beam-section semantics cannot be mixed with shell elements.");
        return;
      }
      ParseBeamSection(block, part);
      part_sections_seen_ = !failure_;
      beam_section_context_active_ = !failure_;
    } else if (block.canonical_name == "SHELL SECTION") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_) {
        InvalidKeywordLocation(
            block, "SHELL SECTION follows the part mesh and optional sets.");
        return;
      }
      if (model_element_family_ == ElementFamily::kBeam) {
        InputFailure(
            "unsupported-mixed-element-model", block.location,
            block.canonical_name, "",
            "Shell-section semantics cannot be mixed with beam elements.");
        return;
      }
      ParseShellSection(block, part);
      part_sections_seen_ = !failure_;
    } else if (block.canonical_name == "SECTION POINTS") {
      ParseSectionPoints(block, part);
    } else if (block.canonical_name == "TRANSVERSE SHEAR STIFFNESS") {
      pending_section_.reset();
      if (!beam_section_context_active_) {
        InputFailure(
            "invalid-keyword-location", block.location, block.canonical_name,
            "",
            "The ignored shear keyword still requires beam-section context.");
        return;
      }
      AddIgnoredWarning(block);
    } else {
      pending_section_.reset();
      beam_section_context_active_ = false;
      RejectUnknown(block);
    }
  }

  void ParseNodes(const KeywordBlock& block, RawPart& part) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "NODE requires at least one four-field data row.");
      }
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 4U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "NODE rows require label, x, y, z.");
        return;
      }
      RawNode node{};
      node.label_text = row.fields[0];
      node.location = row.location;
      if (!ParseInteger(row.fields[0], node.label, row.location,
                        block.canonical_name, true)) {
        return;
      }
      if (std::any_of(part.nodes.begin(), part.nodes.end(),
                      [&node](const RawNode& existing) {
                        return existing.label == node.label;
                      })) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     node.label_text, "Node labels are unique within a part.");
        return;
      }
      for (std::size_t coordinate = 0U; coordinate < 3U; ++coordinate) {
        if (!ParseDouble(row.fields[coordinate + 1U],
                         node.coordinates[coordinate], row.location,
                         block.canonical_name)) {
          return;
        }
      }
      part.nodes.push_back(std::move(node));
    }
  }

  void ParseElements(const KeywordBlock& block, RawPart& part) {
    if (!ValidateParameters(block, {"TYPE"})) {
      return;
    }
    const auto* type = RequiredParameterValue(block, "TYPE");
    if (type == nullptr) {
      return;
    }
    RawElement::Type element_type{};
    ElementFamily element_family{};
    std::size_t expected_field_count = 0U;
    if (AsciiCaseInsensitiveEquals(*type, "B33")) {
      element_type = RawElement::Type::kB33;
      element_family = ElementFamily::kBeam;
      expected_field_count = 3U;
    } else if (AsciiCaseInsensitiveEquals(*type, "S4")) {
      element_type = RawElement::Type::kS4;
      element_family = ElementFamily::kShell;
      expected_field_count = 5U;
    } else if (AsciiCaseInsensitiveEquals(*type, "S4R")) {
      element_type = RawElement::Type::kS4r;
      element_family = ElementFamily::kShell;
      expected_field_count = 5U;
    } else {
      InputFailure(
          "unsupported-element-formulation", block.location,
          block.canonical_name, *type,
          "Only TYPE=B33, TYPE=S4, and TYPE=S4R belong to the approved "
          "element subsets.");
      return;
    }
    if (model_element_family_ && *model_element_family_ != element_family) {
      InputFailure("unsupported-mixed-element-model", block.location,
                   block.canonical_name, *type,
                   "Beam and shell elements cannot be mixed in one model.");
      return;
    }
    model_element_family_ = element_family;
    if (block.data.empty()) {
      InputFailure(element_family == ElementFamily::kShell
                       ? "invalid-shell-connectivity"
                       : "invalid-data-arity",
                   block.location, block.canonical_name, "",
                   "ELEMENT requires at least one row with the approved "
                   "connectivity arity.");
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != expected_field_count) {
        InputFailure(
            element_family == ElementFamily::kShell
                ? "invalid-shell-connectivity"
                : "invalid-data-arity",
            row.location, block.canonical_name, "",
            element_family == ElementFamily::kShell
                ? "S4 and S4R rows require a label and exactly four nodes."
                : "B33 rows require label, node 1, node 2.");
        return;
      }
      RawElement element{};
      element.label_text = row.fields[0];
      element.type = element_type;
      element.location = row.location;
      if (!ParseInteger(row.fields[0], element.label, row.location,
                        block.canonical_name, true)) {
        return;
      }
      element.node_labels.reserve(expected_field_count - 1U);
      for (std::size_t field = 1U; field < expected_field_count; ++field) {
        std::int64_t node_label = 0;
        if (!ParseInteger(row.fields[field], node_label, row.location,
                          block.canonical_name, true)) {
          return;
        }
        element.node_labels.push_back(node_label);
      }
      if (element_family == ElementFamily::kShell) {
        const std::set<std::int64_t> distinct_nodes{element.node_labels.begin(),
                                                    element.node_labels.end()};
        if (distinct_nodes.size() != element.node_labels.size()) {
          InputFailure(
              "invalid-shell-connectivity", row.location, block.canonical_name,
              element.label_text,
              "Shell connectivity requires four distinct source nodes.");
          return;
        }
      }
      if (std::any_of(part.elements.begin(), part.elements.end(),
                      [&element](const RawElement& existing) {
                        return existing.label == element.label;
                      })) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     element.label_text,
                     "Element labels are unique within a part.");
        return;
      }
      part.elements.push_back(std::move(element));
    }
  }

  void ParseShellSection(const KeywordBlock& block, RawPart& part) {
    for (const auto& candidate : block.parameters) {
      if (candidate.name != "ELSET" && candidate.name != "MATERIAL") {
        InputFailure("unsupported-shell-section-option", block.location,
                     block.canonical_name, candidate.name,
                     "The shell-section option is outside the centered "
                     "single-layer subset.");
        return;
      }
    }
    if (!ValidateParameters(block, {"ELSET", "MATERIAL"})) {
      return;
    }
    const auto* element_set = RequiredParameterValue(block, "ELSET");
    const auto* material = RequiredParameterValue(block, "MATERIAL");
    if (element_set == nullptr || material == nullptr) {
      return;
    }
    if (block.data.size() != 1U || block.data[0].fields.empty() ||
        block.data[0].fields.size() > 2U) {
      InputFailure("unsupported-shell-section-option", block.location,
                   block.canonical_name, *element_set,
                   "SHELL SECTION requires one thickness row with one optional "
                   "integration-point field.");
      return;
    }
    double thickness = 0.0;
    if (!ParseModelDouble(block.data[0].fields[0], thickness,
                          block.data[0].location, block.canonical_name,
                          "invalid-shell-thickness",
                          "Shell thickness must be finite and positive.")) {
      return;
    }
    if (!(thickness > 0.0)) {
      ModelFailure("invalid-shell-thickness", block.data[0].location,
                   block.canonical_name, *element_set,
                   "Shell thickness must be finite and positive.");
      return;
    }
    if (block.data[0].fields.size() == 2U) {
      if (!ParsePositiveSourceLabel(block.data[0].fields[1]).HasValue()) {
        InputFailure("unsupported-shell-section-option", block.data[0].location,
                     block.canonical_name, block.data[0].fields[1],
                     "The optional shell integration-point field must be a "
                     "positive integer.");
        return;
      }
    }
    part.shell_sections.push_back(
        {*element_set, *material, thickness, block.location});
  }

  bool ParseSetMembers(const KeywordBlock& block, bool generate,
                       std::vector<std::int64_t>& members) {
    if (block.data.empty()) {
      return InputFailure("invalid-data-arity", block.location,
                          block.canonical_name, "",
                          "A set requires at least one member row.");
    }
    for (const auto& data : block.data) {
      auto fields = WithoutTrailingEmpty(data.fields);
      if (generate) {
        if (fields.size() != 3U) {
          return InputFailure("invalid-data-arity", data.location,
                              block.canonical_name, "",
                              "GENERATE rows require first, last, increment.");
        }
        std::int64_t first = 0;
        std::int64_t last = 0;
        std::int64_t increment = 0;
        if (!ParseInteger(fields[0], first, data.location, block.canonical_name,
                          true) ||
            !ParseInteger(fields[1], last, data.location, block.canonical_name,
                          true)) {
          return false;
        }
        if (!ParseInteger(fields[2], increment, data.location,
                          block.canonical_name, false) ||
            increment <= 0 || first > last || (last - first) % increment != 0) {
          return InputFailure("invalid-set-range", data.location,
                              block.canonical_name, "",
                              "GENERATE requires an inclusive range reached by "
                              "a positive increment.");
        }
        for (std::int64_t label = first; label <= last;) {
          members.push_back(label);
          if (label > last - increment) {
            break;
          }
          label += increment;
        }
      } else {
        if (fields.empty() || std::any_of(fields.begin(), fields.end(),
                                          [](const std::string& field) {
                                            return field.empty();
                                          })) {
          return InputFailure(
              "invalid-data-arity", data.location, block.canonical_name, "",
              "Explicit set rows require non-empty member labels.");
        }
        for (const auto& field : fields) {
          std::int64_t label = 0;
          if (!ParseInteger(field, label, data.location, block.canonical_name,
                            true)) {
            return false;
          }
          members.push_back(label);
        }
      }
    }
    std::set<std::int64_t> unique;
    for (const auto member : members) {
      if (!unique.insert(member).second) {
        return InputFailure("duplicate-entity", block.location,
                            block.canonical_name, std::to_string(member),
                            "A set cannot repeat the same source member.");
      }
    }
    return true;
  }

  void ParseSet(const KeywordBlock& block, bool node_set, RawPart& part) {
    const std::string_view name_parameter = node_set ? "NSET" : "ELSET";
    if (!ValidateParameters(block, {name_parameter, "GENERATE"})) {
      return;
    }
    const auto* name = RequiredParameterValue(block, name_parameter);
    if (name == nullptr) {
      return;
    }
    const auto* generate_parameter = Parameter(block, "GENERATE");
    if (generate_parameter != nullptr && generate_parameter->value) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "GENERATE",
                   "GENERATE is a valueless flag.");
      return;
    }
    const auto& sets = node_set ? part.node_sets : part.element_sets;
    if (ContainsSetName(sets, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Set names are unique within their node-set or element-set "
                   "namespace.");
      return;
    }
    RawSet set{*name, {}, block.location};
    if (!ParseSetMembers(block, generate_parameter != nullptr, set.members)) {
      return;
    }
    if (node_set) {
      part.node_sets.push_back(std::move(set));
    } else {
      part.element_sets.push_back(std::move(set));
    }
  }

  void ParseBeamSection(const KeywordBlock& block, RawPart& part) {
    pending_section_.reset();
    if (!ValidateParameters(block, {"ELSET", "MATERIAL", "SECTION"})) {
      return;
    }
    const auto* element_set = RequiredParameterValue(block, "ELSET");
    const auto* material = RequiredParameterValue(block, "MATERIAL");
    const auto* section = RequiredParameterValue(block, "SECTION");
    if (element_set == nullptr || material == nullptr || section == nullptr) {
      return;
    }
    if (!AsciiCaseInsensitiveEquals(*section, "GENERAL")) {
      InputFailure("unsupported-section-formulation", block.location,
                   block.canonical_name, *section,
                   "Only SECTION=GENERAL belongs to the approved subset.");
      return;
    }
    if (std::any_of(part.sections.begin(), part.sections.end(),
                    [element_set](const RawSection& existing) {
                      return AsciiCaseInsensitiveEquals(
                          existing.element_set_name, *element_set);
                    })) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *element_set,
                   "An element set can receive only one beam section.");
      return;
    }
    if (block.data.size() != 2U || block.data[0].fields.size() != 5U ||
        block.data[1].fields.size() != 3U) {
      InputFailure("invalid-data-arity", block.location, block.canonical_name,
                   *element_set,
                   "A general section requires one five-field property row and "
                   "one three-field axis row.");
      return;
    }
    RawSection raw{*element_set, *material, {}, {}, {}, block.location};
    for (std::size_t property = 0U; property < 5U; ++property) {
      if (!ParseModelDouble(block.data[0].fields[property],
                            raw.properties[property], block.data[0].location,
                            block.canonical_name, "invalid-beam-property",
                            "Beam section properties must be finite.")) {
        return;
      }
    }
    for (std::size_t coordinate = 0U; coordinate < 3U; ++coordinate) {
      if (!ParseModelDouble(block.data[1].fields[coordinate],
                            raw.first_axis[coordinate], block.data[1].location,
                            block.canonical_name, "invalid-beam-guide-vector",
                            "The beam guide vector must be finite.")) {
        return;
      }
    }
    part.sections.push_back(std::move(raw));
    pending_section_ = part.sections.size() - 1U;
  }

  void ParseSectionPoints(const KeywordBlock& block, RawPart& part) {
    if (!pending_section_ || !ValidateParameters(block, {}) ||
        block.data.empty()) {
      if (!failure_) {
        InputFailure(
            "invalid-keyword-location", block.location, block.canonical_name,
            "", "SECTION POINTS must immediately follow a general section.");
      }
      return;
    }
    RawSection& section = part.sections[*pending_section_];
    for (const auto& row : block.data) {
      if (row.fields.size() != 2U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     section.element_set_name,
                     "Section-point rows require x1 and x2.");
        return;
      }
      std::array<double, 2> point{};
      if (!ParseDouble(row.fields[0], point[0], row.location,
                       block.canonical_name) ||
          !ParseDouble(row.fields[1], point[1], row.location,
                       block.canonical_name)) {
        return;
      }
      if (std::find(section.section_points.begin(),
                    section.section_points.end(),
                    point) != section.section_points.end()) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     section.element_set_name,
                     "Section points must be unique within a section.");
        return;
      }
      section.section_points.push_back(point);
    }
    pending_section_.reset();
  }

  void ParseAssemblyStart(const KeywordBlock& block) {
    if (assembly_seen_) {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "V0 accepts exactly one non-nested assembly.");
      return;
    }
    if (parts_.empty() || !materials_.empty() || model_boundary_seen_) {
      InvalidKeywordLocation(
          block,
          "The sole assembly follows all part blocks and precedes model data.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    if (RequiredParameterValue(block, "NAME") == nullptr) {
      return;
    }
    assembly_seen_ = true;
    in_assembly_ = true;
    assembly_set_seen_ = false;
  }

  void ParseAssemblyBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END ASSEMBLY") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "The assembly requires at least one identity instance.");
        return;
      }
      in_assembly_ = false;
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "Nested or duplicate assembly blocks are unsupported.");
    } else if (block.canonical_name == "INSTANCE") {
      if (assembly_set_seen_) {
        InvalidKeywordLocation(
            block, "All identity instances must precede assembly-level sets.");
        return;
      }
      ParseInstanceStart(block);
    } else if (block.canonical_name == "NSET") {
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "Assembly sets follow at least one identity instance.");
        return;
      }
      assembly_set_seen_ = true;
      ParseAssemblySet(block, true);
    } else if (block.canonical_name == "ELSET") {
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "Assembly sets follow at least one identity instance.");
        return;
      }
      assembly_set_seen_ = true;
      ParseAssemblySet(block, false);
    } else {
      RejectUnknown(block);
    }
  }

  void ParseInstanceStart(const KeywordBlock& block) {
    if (Parameter(block, "DEPENDENT") != nullptr ||
        Parameter(block, "INDEPENDENT") != nullptr) {
      InputFailure(
          "unsupported-instance-mesh-semantics", block.location,
          block.canonical_name, "",
          "Dependent and independent instance mesh semantics are unsupported.");
      return;
    }
    if (!ValidateParameters(block, {"NAME", "PART"})) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    const auto* part = RequiredParameterValue(block, "PART");
    if (name == nullptr || part == nullptr) {
      return;
    }
    if (!block.data.empty()) {
      InputFailure("unsupported-instance-transform",
                   block.data.front().location, block.canonical_name, *name,
                   "Instance translation or rotation data is unsupported.");
      return;
    }
    if (ContainsName(instances_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name, "Instance names are globally unique.");
      return;
    }
    instances_.push_back({*name, *part, block.location});
    in_instance_ = true;
  }

  void ParseInstanceBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END INSTANCE") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      in_instance_ = false;
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "An assembly cannot be nested in an instance.");
      return;
    }
    InputFailure("unsupported-instance-mesh-semantics", block.location,
                 block.canonical_name, instances_.back().name,
                 "Instance-local mesh definitions are unsupported.");
  }

  void ParseAssemblySet(const KeywordBlock& block, bool node_set) {
    const std::string_view name_parameter = node_set ? "NSET" : "ELSET";
    if (!ValidateParameters(block, {name_parameter, "INSTANCE", "GENERATE"})) {
      return;
    }
    const auto* name = RequiredParameterValue(block, name_parameter);
    const auto* instance = RequiredParameterValue(block, "INSTANCE");
    if (name == nullptr || instance == nullptr) {
      return;
    }
    const auto* generate_parameter = Parameter(block, "GENERATE");
    if (generate_parameter != nullptr && generate_parameter->value) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "GENERATE",
                   "GENERATE is a valueless flag.");
      return;
    }
    if (ContainsAssemblySetName(node_set, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Assembly set names are unique within their node-set or "
                   "element-set namespace.");
      return;
    }
    RawAssemblySet set{node_set, *name, *instance, {}, block.location};
    if (!ParseSetMembers(block, generate_parameter != nullptr, set.members)) {
      return;
    }
    assembly_sets_.push_back(std::move(set));
  }

  void ParseMaterial(const KeywordBlock& block) {
    if (!assembly_seen_ || model_boundary_seen_) {
      InvalidKeywordLocation(block,
                             "Material definitions follow the assembly and "
                             "precede model boundaries.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    if (name == nullptr) {
      return;
    }
    if (ContainsName(materials_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name, "Material names are globally unique.");
      return;
    }
    materials_.push_back({*name, 0.0, 0.0, false, block.location, {}});
    material_eligible_ = materials_.size() - 1U;
  }

  void ParseElastic(const KeywordBlock& block) {
    if (!material_eligible_) {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "ELASTIC must immediately follow MATERIAL.");
      return;
    }
    if (!ValidateParameters(block, {}) || block.data.size() != 1U ||
        block.data[0].fields.size() != 2U) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     materials_[*material_eligible_].name,
                     "ELASTIC requires exactly one E, nu row.");
      }
      return;
    }
    RawMaterial& material = materials_[*material_eligible_];
    if (material.has_elastic) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   material.name, "A material accepts one ELASTIC definition.");
      return;
    }
    if (!ParseModelDouble(block.data[0].fields[0], material.youngs_modulus,
                          block.data[0].location, block.canonical_name,
                          model_element_family_ == ElementFamily::kShell
                              ? "invalid-shell-material"
                              : "invalid-beam-property",
                          "Elastic material values must be finite.") ||
        !ParseModelDouble(block.data[0].fields[1], material.poisson_ratio,
                          block.data[0].location, block.canonical_name,
                          model_element_family_ == ElementFamily::kShell
                              ? "invalid-shell-material"
                              : "invalid-beam-property",
                          "Elastic material values must be finite.")) {
      return;
    }
    material.has_elastic = true;
    material.elastic_location = block.data[0].location;
  }

  void ParseBoundary(const KeywordBlock& block,
                     std::vector<BoundaryCondition>& destination) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "BOUNDARY requires one or more data rows.");
      }
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 3U && row.fields.size() != 4U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "",
                     "BOUNDARY rows require target, first DOF, last DOF, and "
                     "optional value.");
        return;
      }
      if (row.fields[0].empty()) {
        InputFailure("unresolved-reference", row.location, block.canonical_name,
                     "", "A boundary target cannot be empty.");
        return;
      }
      std::int64_t first = 0;
      std::int64_t last = 0;
      if (!ParseInteger(row.fields[1], first, row.location,
                        block.canonical_name, true) ||
          !ParseInteger(row.fields[2], last, row.location, block.canonical_name,
                        true)) {
        return;
      }
      if (first < 1 || first > 6 || last < first || last > 6) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0],
                     "Boundary DOFs must be an ordered range in 1..6.");
        return;
      }
      double value = 0.0;
      if (row.fields.size() == 4U &&
          !ParseDouble(row.fields[3], value, row.location,
                       block.canonical_name)) {
        return;
      }
      destination.push_back({row.fields[0], static_cast<int>(first),
                             static_cast<int>(last), value, row.location});
    }
  }

  void ParseCload(const KeywordBlock& block, std::vector<NodalLoad>& loads) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "CLOAD requires one or more rows.");
      }
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 3U || row.fields[0].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "CLOAD rows require target, DOF, magnitude.");
        return;
      }
      std::int64_t dof = 0;
      double magnitude = 0.0;
      if (!ParseInteger(row.fields[1], dof, row.location, block.canonical_name,
                        true) ||
          !ParseDouble(row.fields[2], magnitude, row.location,
                       block.canonical_name)) {
        return;
      }
      if (dof < 1 || dof > 6) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0], "CLOAD DOF must be in 1..6.");
        return;
      }
      loads.push_back(
          {row.fields[0], static_cast<int>(dof), magnitude, row.location});
    }
  }

  void ParseStepStart(const KeywordBlock& block) {
    if (step_seen_) {
      InputFailure("unsupported-multiple-step", block.location,
                   block.canonical_name, "",
                   "V0 accepts exactly one analysis step.");
      return;
    }
    if (!assembly_seen_ || materials_.empty()) {
      InvalidKeywordLocation(block,
                             "The sole step follows the complete assembly and "
                             "material definitions.");
      return;
    }
    if (!ValidateParameters(block, {"NAME", "NLGEOM"}) ||
        !RequireNoData(block)) {
      return;
    }
    const auto* nlgeom = Parameter(block, "NLGEOM");
    if (nlgeom != nullptr) {
      if (!nlgeom->value || nlgeom->value->empty()) {
        InputFailure("invalid-keyword-parameter", block.location,
                     block.canonical_name, "NLGEOM",
                     "NLGEOM requires NO in the approved subset.");
        return;
      }
      if (!AsciiCaseInsensitiveEquals(*nlgeom->value, "NO")) {
        if (model_element_family_ == ElementFamily::kShell) {
          InputFailure("unsupported-nonlinear-geometry", block.location,
                       block.canonical_name, *nlgeom->value,
                       "Only absent NLGEOM or NLGEOM=NO is supported.");
        } else {
          ModelFailure("unsupported-nonlinear-geometry", block.location,
                       block.canonical_name, *nlgeom->value,
                       "Only absent NLGEOM or NLGEOM=NO is supported.");
        }
        return;
      }
    }
    step_seen_ = true;
    in_step_ = true;
    step_ = RawStep{block.location, false, {}, {}, {}};
    step_load_seen_ = false;
    step_no_op_seen_ = false;
  }

  void ParseStepBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END STEP") {
      active_output_ = false;
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      if (!step_.has_static) {
        InvalidKeywordLocation(
            block,
            "The sole step requires exactly one leading STATIC procedure.");
        return;
      }
      in_step_ = false;
      return;
    }
    if (block.canonical_name == "STEP") {
      InputFailure("unsupported-multiple-step", block.location,
                   block.canonical_name, "",
                   "A second or nested step is unsupported.");
      return;
    }
    if (block.canonical_name == "STATIC") {
      active_output_ = false;
      if (!step_.boundaries.empty() || !step_.loads.empty() ||
          step_no_op_seen_) {
        InvalidKeywordLocation(
            block, "STATIC must be the first keyword in the sole step.");
        return;
      }
      ParseStatic(block);
    } else if (block.canonical_name == "BOUNDARY") {
      active_output_ = false;
      if (!step_.has_static || step_load_seen_ || step_no_op_seen_) {
        InvalidKeywordLocation(
            block,
            "Step boundaries follow STATIC and precede loads "
            "and no-op requests.");
        return;
      }
      ParseBoundary(block, step_.boundaries);
    } else if (block.canonical_name == "CLOAD") {
      active_output_ = false;
      if (!step_.has_static || step_no_op_seen_) {
        InvalidKeywordLocation(
            block,
            "CLOAD follows STATIC and boundaries and precedes no-op requests.");
        return;
      }
      ParseCload(block, step_.loads);
      step_load_seen_ = !failure_;
    } else if (block.canonical_name == "RESTART") {
      active_output_ = false;
      if (!step_.has_static) {
        InvalidKeywordLocation(
            block, "Step no-op requests follow STATIC, boundaries, and loads.");
        return;
      }
      step_no_op_seen_ = true;
      if (RequireNoData(block)) {
        AddIgnoredWarning(block);
      }
    } else if (block.canonical_name == "OUTPUT") {
      if (!step_.has_static) {
        InvalidKeywordLocation(
            block, "Step no-op requests follow STATIC, boundaries, and loads.");
        return;
      }
      step_no_op_seen_ = true;
      ParseOutputRoot(block);
    } else if (block.canonical_name == "NODE OUTPUT" ||
               block.canonical_name == "ELEMENT OUTPUT" ||
               block.canonical_name == "CONTACT OUTPUT") {
      ParseOutputChild(block);
    } else {
      active_output_ = false;
      RejectUnknown(block);
    }
  }

  void ParseStatic(const KeywordBlock& block) {
    if (step_.has_static || !ValidateParameters(block, {}) ||
        block.data.size() != 1U || block.data[0].fields.size() != 4U) {
      if (!failure_) {
        InputFailure("invalid-static-data", block.location,
                     block.canonical_name, "",
                     "STATIC requires exactly one row of four values.");
      }
      return;
    }
    for (std::size_t field = 0U; field < 4U; ++field) {
      if (!ParseDouble(block.data[0].fields[field], step_.static_values[field],
                       block.data[0].location, block.canonical_name)) {
        return;
      }
      if (step_.static_values[field] <= 0.0) {
        InputFailure("invalid-static-data", block.data[0].location,
                     block.canonical_name, "",
                     "All four STATIC fields must be positive.");
        return;
      }
    }
    if (step_.static_values[2] > step_.static_values[3]) {
      InputFailure("invalid-static-data", block.data[0].location,
                   block.canonical_name, "",
                   "STATIC minimum increment cannot exceed maximum increment.");
      return;
    }
    step_.has_static = true;
  }

  void ParseOutputRoot(const KeywordBlock& block) {
    const auto* field = Parameter(block, "FIELD");
    const auto* history = Parameter(block, "HISTORY");
    if ((field == nullptr) == (history == nullptr) ||
        (field != nullptr && field->value) ||
        (history != nullptr && history->value)) {
      InputFailure("unsupported-keyword", block.location, block.canonical_name,
                   "", "OUTPUT must select exactly FIELD or HISTORY.");
      return;
    }
    active_output_ = true;
    AddIgnoredWarning(block);
  }

  void ParseOutputChild(const KeywordBlock& block) {
    if (!active_output_) {
      InputFailure(
          "invalid-keyword-location", block.location, block.canonical_name, "",
          "Output variable keywords require an active OUTPUT request.");
      return;
    }
    AddIgnoredWarning(block);
  }

  void AddIgnoredWarning(const KeywordBlock& block) {
    // One warning per allowlisted keyword keeps no-op provenance stable;
    // subordinate variable rows remain attached to that keyword record.
    definition_.warnings.push_back(
        {Severity::kWarning, "ignored-input-keyword", block.location,
         block.canonical_name, "",
         "The allowlisted Abaqus keyword is ignored without semantic effect."});
  }

  void RejectUnknown(const KeywordBlock& block) {
    if (block.canonical_name == "DLOAD" &&
        model_element_family_ == ElementFamily::kShell) {
      InputFailure("unsupported-distributed-load", block.location,
                   block.canonical_name, "",
                   "Distributed, pressure, gravity, body, edge, and follower "
                   "loads are unsupported.");
      return;
    }
    InputFailure("unsupported-keyword", block.location, block.canonical_name,
                 "", "The keyword is outside the approved Abaqus subset.");
  }

  const RawPart* FindPart(const std::string& name) const {
    const auto found = std::find_if(
        parts_.begin(), parts_.end(), [&name](const RawPart& part) {
          return AsciiCaseInsensitiveEquals(part.name, name);
        });
    return found == parts_.end() ? nullptr : &*found;
  }

  const RawInstance* FindInstance(const std::string& name) const {
    const auto found =
        std::find_if(instances_.begin(), instances_.end(),
                     [&name](const RawInstance& instance) {
                       return AsciiCaseInsensitiveEquals(instance.name, name);
                     });
    return found == instances_.end() ? nullptr : &*found;
  }

  std::optional<EntityIndex> FindMaterialIndex(const std::string& name) const {
    for (std::size_t index = 0U; index < materials_.size(); ++index) {
      if (AsciiCaseInsensitiveEquals(materials_[index].name, name)) {
        return static_cast<EntityIndex>(index);
      }
    }
    return std::nullopt;
  }

  const RawSet* FindSet(const std::vector<RawSet>& sets,
                        const std::string& name) const {
    const auto found =
        std::find_if(sets.begin(), sets.end(), [&name](const RawSet& set) {
          return AsciiCaseInsensitiveEquals(set.name, name);
        });
    return found == sets.end() ? nullptr : &*found;
  }

  const RawNode* FindNode(const RawPart& part, std::int64_t label) const {
    const auto found = std::find_if(
        part.nodes.begin(), part.nodes.end(),
        [label](const RawNode& node) { return node.label == label; });
    return found == part.nodes.end() ? nullptr : &*found;
  }

  const RawElement* FindElement(const RawPart& part, std::int64_t label) const {
    const auto found = std::find_if(
        part.elements.begin(), part.elements.end(),
        [label](const RawElement& element) { return element.label == label; });
    return found == part.elements.end() ? nullptr : &*found;
  }

  void FinalizeModel() {
    if (parts_.empty() || !assembly_seen_ || instances_.empty() ||
        materials_.empty() || !step_seen_ || !step_.has_static) {
      const auto location = input_.blocks.empty()
                                ? SourceLocation{input_.source_path, 0U}
                                : input_.blocks.back().location;
      InputFailure("invalid-model-cardinality", location, "", "",
                   "The model requires part, assembly, identity instance, "
                   "material, and one STATIC step.");
      return;
    }

    FinalizeMaterials();
    if (failure_) {
      return;
    }
    FinalizePartsAndSections();
    if (failure_) {
      return;
    }
    ExpandInstances();
    if (failure_) {
      return;
    }
    if (!definition_.shell_elements.empty()) {
      auto geometry =
          PreprocessShellGeometry(definition_.nodes, definition_.shell_elements,
                                  definition_.shell_sections);
      if (!geometry.HasValue()) {
        const auto& status = geometry.GetStatus();
        failure_ =
            MappingFailure{status.Category().value_or(FailureCategory::kModel),
                           status.Diagnostics().front()};
        return;
      }
      definition_.shell_node_initial_frames =
          std::move(geometry.Value().nodal_frames);
    }
    ExpandAssemblySets();
    if (failure_) {
      return;
    }
    FinalizeStep();
  }

  void FinalizeMaterials() {
    for (const auto& material : materials_) {
      if (!material.has_elastic) {
        InputFailure("unresolved-reference", material.location, "MATERIAL",
                     material.name,
                     "A material must own exactly one ELASTIC row.");
        return;
      }
      if (model_element_family_ == ElementFamily::kShell) {
        if (!(material.youngs_modulus > 0.0) ||
            !(material.poisson_ratio > -1.0) ||
            !(material.poisson_ratio < 0.5)) {
          ModelFailure(
              "invalid-shell-material", material.elastic_location, "ELASTIC",
              material.name,
              "Shell isotropic elasticity requires E>0 and -1<nu<0.5.");
          return;
        }
        definition_.materials.push_back({material.name, material.youngs_modulus,
                                         material.poisson_ratio,
                                         material.location});
        continue;
      }
      const double denominator = 2.0 * (1.0 + material.poisson_ratio);
      const double shear_modulus = material.youngs_modulus / denominator;
      // The approved ledger deliberately validates derived G, not an
      // independent upper bound on Poisson's ratio.
      if (!(material.youngs_modulus > 0.0) || !std::isfinite(shear_modulus) ||
          !(shear_modulus > 0.0)) {
        ModelFailure("invalid-beam-property", material.elastic_location,
                     "ELASTIC", material.name,
                     "E and the derived G=E/(2*(1+nu)) must be positive.");
        return;
      }
      definition_.materials.push_back({material.name, material.youngs_modulus,
                                       material.poisson_ratio,
                                       material.location});
    }
  }

  void FinalizePartsAndSections() {
    part_section_assignments_.resize(parts_.size());
    part_shell_section_assignments_.resize(parts_.size());
    const bool shell_model = model_element_family_ == ElementFamily::kShell;
    for (std::size_t part_index = 0U; part_index < parts_.size();
         ++part_index) {
      const RawPart& part = parts_[part_index];
      if (part.nodes.empty() || part.elements.empty() ||
          (!shell_model && part.sections.empty())) {
        InputFailure("invalid-model-cardinality", part.location, "PART",
                     part.name,
                     "A part requires nodes, elements, and its approved "
                     "section form.");
        return;
      }

      PartDefinition part_definition{};
      part_definition.name = part.name;
      part_definition.location = part.location;
      for (const auto& node : part.nodes) {
        part_definition.node_source_labels.push_back(node.label);
      }
      for (const auto& element : part.elements) {
        part_definition.element_source_labels.push_back(element.label);
        for (const auto node_label : element.node_labels) {
          if (FindNode(part, node_label) == nullptr) {
            InputFailure(shell_model ? "invalid-shell-connectivity"
                                     : "unresolved-reference",
                         element.location, "ELEMENT", element.label_text,
                         "Element connectivity must resolve within its part.");
            return;
          }
        }
      }
      for (const auto& set : part.node_sets) {
        part_definition.node_set_names.push_back(set.name);
        for (const auto label : set.members) {
          if (FindNode(part, label) == nullptr) {
            InputFailure("unresolved-reference", set.location, "NSET", set.name,
                         "Every node-set member must resolve within its part.");
            return;
          }
        }
      }
      for (const auto& set : part.element_sets) {
        part_definition.element_set_names.push_back(set.name);
        for (const auto label : set.members) {
          if (FindElement(part, label) == nullptr) {
            InputFailure(
                "unresolved-reference", set.location, "ELSET", set.name,
                "Every element-set member must resolve within its part.");
            return;
          }
        }
      }
      definition_.parts.push_back(std::move(part_definition));

      if (shell_model) {
        auto& assignments = part_shell_section_assignments_[part_index];
        for (const auto& section : part.shell_sections) {
          const auto* element_set =
              FindSet(part.element_sets, section.element_set_name);
          const auto material_index = FindMaterialIndex(section.material_name);
          if (element_set == nullptr || !material_index) {
            InputFailure("unresolved-shell-section", section.location,
                         "SHELL SECTION", section.element_set_name,
                         "Shell section ELSET and MATERIAL references "
                         "must resolve.");
            return;
          }
          const EntityIndex section_index =
              static_cast<EntityIndex>(definition_.shell_sections.size());
          definition_.shell_sections.push_back(
              {section.element_set_name, section.thickness, *material_index,
               section.location});
          for (const auto element_label : element_set->members) {
            if (!assignments
                     .emplace(element_label,
                              std::make_pair(section_index, *material_index))
                     .second) {
              InputFailure("invalid-shell-section-assignment", section.location,
                           "SHELL SECTION", std::to_string(element_label),
                           "A shell element cannot receive multiple "
                           "section assignments.");
              return;
            }
          }
        }
        for (const auto& element : part.elements) {
          if (assignments.find(element.label) == assignments.end()) {
            InputFailure("invalid-shell-section-assignment", element.location,
                         "ELEMENT", element.label_text,
                         "Every shell element requires exactly one "
                         "resolved section assignment.");
            return;
          }
        }
        continue;
      }

      auto& assignments = part_section_assignments_[part_index];
      for (const auto& section : part.sections) {
        const auto* element_set =
            FindSet(part.element_sets, section.element_set_name);
        const auto material_index = FindMaterialIndex(section.material_name);
        if (element_set == nullptr || !material_index) {
          InputFailure("unresolved-reference", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "Section ELSET and MATERIAL references must resolve.");
          return;
        }
        if (section.properties[2] != 0.0) {
          ModelFailure("unsupported-coupled-section", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "V0 requires exact I12=0.");
          return;
        }
        if (!(section.properties[0] > 0.0) || !(section.properties[1] > 0.0) ||
            !(section.properties[3] > 0.0) || !(section.properties[4] > 0.0)) {
          ModelFailure("invalid-beam-property", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "A, I11, I22, and J must be positive.");
          return;
        }
        const EntityIndex section_index =
            static_cast<EntityIndex>(definition_.sections.size());
        definition_.sections.push_back(
            {section.element_set_name, section.properties[0],
             section.properties[1], section.properties[2],
             section.properties[3], section.properties[4], section.first_axis,
             section.section_points, section.location});
        for (const auto element_label : element_set->members) {
          if (!assignments
                   .emplace(element_label,
                            std::make_pair(section_index, *material_index))
                   .second) {
            InputFailure("duplicate-entity", section.location,
                         "BEAM GENERAL SECTION", std::to_string(element_label),
                         "An element cannot receive multiple section "
                         "assignments.");
            return;
          }
        }
      }
      for (const auto& element : part.elements) {
        if (assignments.find(element.label) == assignments.end()) {
          InputFailure(
              "unresolved-reference", element.location, "ELEMENT",
              element.label_text,
              "Every B33 element requires a resolved section assignment.");
          return;
        }
      }
    }
  }

  std::size_t PartIndex(const RawPart& part) const {
    return static_cast<std::size_t>(&part - parts_.data());
  }

  bool ValidateGeometry(const RawElement& raw, const Node& first,
                        const Node& second, const GeneralBeamSection& section) {
    const auto maximum_absolute = [](const Vector3& vector) {
      return std::max(
          {std::abs(vector[0]), std::abs(vector[1]), std::abs(vector[2])});
    };
    const Vector3 first_position{first.coordinates};
    const Vector3 second_position{second.coordinates};

    // Compare both approved inequalities after a common scaling. This
    // preserves the exact ratios while avoiding overflow in x*x and in
    // subtraction between large finite coordinates.
    const double global_coordinate_scale =
        std::max({1.0, maximum_absolute(first_position),
                  maximum_absolute(second_position)});
    const Vector3 first_scaled = first_position / global_coordinate_scale;
    const Vector3 second_scaled = second_position / global_coordinate_scale;
    const Vector3 delta_scaled = second_scaled - first_scaled;
    const double length_ratio = delta_scaled.Norm();
    const double coordinate_norm_ratio =
        std::max({1.0 / global_coordinate_scale, first_scaled.Norm(),
                  second_scaled.Norm()});
    if (!(length_ratio > 1.0e-12 * coordinate_norm_ratio)) {
      return ModelFailure(
          "invalid-beam-length", raw.location, "ELEMENT", raw.label_text,
          "Beam length fails the approved scale-aware threshold.");
    }
    const Vector3 tangent = delta_scaled / length_ratio;

    const Vector3 guide{section.first_axis};
    const double global_guide_scale = std::max(1.0, maximum_absolute(guide));
    const Vector3 guide_scaled = guide / global_guide_scale;
    const double projection = guide_scaled.Dot(tangent);
    const Vector3 perpendicular = guide_scaled - projection * tangent;
    const double guide_norm_ratio =
        std::max(1.0 / global_guide_scale, guide_scaled.Norm());
    if (!(perpendicular.Norm() > 1.0e-12 * guide_norm_ratio)) {
      return ModelFailure(
          "invalid-beam-guide-vector", section.location, "BEAM GENERAL SECTION",
          raw.label_text,
          "The first section axis cannot be zero or tangent-parallel.");
    }
    return true;
  }

  void ExpandInstances() {
    for (const auto& raw_instance : instances_) {
      const RawPart* part = FindPart(raw_instance.part_name);
      if (part == nullptr) {
        InputFailure("unresolved-reference", raw_instance.location, "INSTANCE",
                     raw_instance.name,
                     "INSTANCE PART must resolve case-insensitively.");
        return;
      }
      InstanceDefinition instance{
          raw_instance.name, part->name, {}, {}, raw_instance.location};
      std::map<std::int64_t, EntityIndex> node_indices;
      std::map<std::int64_t, EntityIndex> element_indices;

      // Instance order, followed by part-local declaration order, is the
      // sole source of stable expanded internal IDs.
      for (const auto& raw_node : part->nodes) {
        if (definition_.nodes.size() >
            std::numeric_limits<EntityIndex>::max()) {
          InputFailure("entity-index-overflow", raw_node.location, "NODE",
                       raw_node.label_text,
                       "Expanded node count exceeds EntityIndex capacity.");
          return;
        }
        const EntityIndex index =
            static_cast<EntityIndex>(definition_.nodes.size());
        definition_.nodes.push_back(
            {{raw_instance.name, raw_node.label, raw_node.label_text},
             raw_node.coordinates,
             raw_node.location});
        node_indices.emplace(raw_node.label, index);
        instance.node_mappings.push_back({raw_node.label, index});
      }

      for (const auto& raw_element : part->elements) {
        EntityIndex index = 0U;
        if (raw_element.type == RawElement::Type::kB33) {
          const auto first = node_indices.find(raw_element.node_labels[0]);
          const auto second = node_indices.find(raw_element.node_labels[1]);
          const auto& assignments = part_section_assignments_[PartIndex(*part)];
          const auto assignment = assignments.find(raw_element.label);
          if (first == node_indices.end() || second == node_indices.end() ||
              assignment == assignments.end()) {
            InputFailure(
                "unresolved-reference", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded connectivity and section assignment must resolve.");
            return;
          }
          if (definition_.elements.size() >
              std::numeric_limits<EntityIndex>::max()) {
            InputFailure(
                "entity-index-overflow", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded element count exceeds EntityIndex capacity.");
            return;
          }
          index = static_cast<EntityIndex>(definition_.elements.size());
          const auto& section = definition_.sections[assignment->second.first];
          if (!ValidateGeometry(raw_element, definition_.nodes[first->second],
                                definition_.nodes[second->second], section)) {
            return;
          }
          definition_.elements.push_back(
              {{raw_instance.name, raw_element.label, raw_element.label_text},
               {first->second, second->second},
               assignment->second.second,
               assignment->second.first,
               raw_element.location});
        } else {
          std::array<EntityIndex, 4> connected_nodes{};
          for (std::size_t node = 0U; node < connected_nodes.size(); ++node) {
            const auto found = node_indices.find(raw_element.node_labels[node]);
            if (found == node_indices.end()) {
              InputFailure("invalid-shell-connectivity", raw_element.location,
                           "ELEMENT", raw_element.label_text,
                           "Expanded shell connectivity must resolve.");
              return;
            }
            connected_nodes[node] = found->second;
          }
          const auto& assignments =
              part_shell_section_assignments_[PartIndex(*part)];
          const auto assignment = assignments.find(raw_element.label);
          if (assignment == assignments.end()) {
            InputFailure(
                "invalid-shell-section-assignment", raw_element.location,
                "ELEMENT", raw_element.label_text,
                "Expanded shell section assignment must resolve exactly once.");
            return;
          }
          if (definition_.shell_elements.size() >
              std::numeric_limits<EntityIndex>::max()) {
            InputFailure(
                "entity-index-overflow", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded shell element count exceeds EntityIndex capacity.");
            return;
          }
          index = static_cast<EntityIndex>(definition_.shell_elements.size());
          definition_.shell_elements.push_back(
              {{raw_instance.name, raw_element.label, raw_element.label_text},
               raw_element.type == RawElement::Type::kS4
                   ? ShellSourceElementType::kS4
                   : ShellSourceElementType::kS4r,
               connected_nodes,
               assignment->second.second,
               assignment->second.first,
               raw_element.location});
        }
        element_indices.emplace(raw_element.label, index);
        instance.element_mappings.push_back({raw_element.label, index});
      }

      for (const auto& raw_set : part->node_sets) {
        NodeSet set{raw_set.name, raw_instance.name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto found = node_indices.find(member);
          if (found == node_indices.end()) {
            InputFailure("unresolved-reference", raw_set.location, "NSET",
                         raw_set.name, "Part node-set expansion failed.");
            return;
          }
          set.node_indices.push_back(found->second);
        }
        definition_.node_sets.push_back(std::move(set));
      }
      for (const auto& raw_set : part->element_sets) {
        ElementSet set{raw_set.name, raw_instance.name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto found = element_indices.find(member);
          if (found == element_indices.end()) {
            InputFailure("unresolved-reference", raw_set.location, "ELSET",
                         raw_set.name, "Part element-set expansion failed.");
            return;
          }
          set.element_indices.push_back(found->second);
        }
        definition_.element_sets.push_back(std::move(set));
      }
      definition_.instances.push_back(std::move(instance));
    }
  }

  void ExpandAssemblySets() {
    for (const auto& raw_set : assembly_sets_) {
      const RawInstance* raw_instance = FindInstance(raw_set.instance_name);
      if (raw_instance == nullptr) {
        InputFailure("unresolved-reference", raw_set.location,
                     raw_set.is_node_set ? "NSET" : "ELSET", raw_set.name,
                     "Assembly set INSTANCE must resolve.");
        return;
      }
      const auto definition_instance = std::find_if(
          definition_.instances.begin(), definition_.instances.end(),
          [&raw_instance](const InstanceDefinition& instance) {
            return AsciiCaseInsensitiveEquals(instance.name,
                                              raw_instance->name);
          });
      if (definition_instance == definition_.instances.end()) {
        InputFailure("unresolved-reference", raw_set.location,
                     raw_set.is_node_set ? "NSET" : "ELSET", raw_set.name,
                     "Assembly set instance expansion is unavailable.");
        return;
      }
      if (raw_set.is_node_set) {
        definition_.node_sets.erase(
            std::remove_if(
                definition_.node_sets.begin(), definition_.node_sets.end(),
                [&raw_set](const NodeSet& set) {
                  return AsciiCaseInsensitiveEquals(set.name, raw_set.name);
                }),
            definition_.node_sets.end());
        NodeSet set{
            raw_set.name, definition_instance->name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto mapping =
              std::find_if(definition_instance->node_mappings.begin(),
                           definition_instance->node_mappings.end(),
                           [member](const SourceIndexMapping& value) {
                             return value.source_label == member;
                           });
          if (mapping == definition_instance->node_mappings.end()) {
            InputFailure("unresolved-reference", raw_set.location, "NSET",
                         raw_set.name,
                         "Assembly node-set member must resolve in its "
                         "instance.");
            return;
          }
          set.node_indices.push_back(mapping->internal_index);
        }
        definition_.node_sets.push_back(std::move(set));
      } else {
        definition_.element_sets.erase(
            std::remove_if(definition_.element_sets.begin(),
                           definition_.element_sets.end(),
                           [&raw_set](const ElementSet& set) {
                             return AsciiCaseInsensitiveEquals(set.name,
                                                               raw_set.name);
                           }),
            definition_.element_sets.end());
        ElementSet set{
            raw_set.name, definition_instance->name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto mapping =
              std::find_if(definition_instance->element_mappings.begin(),
                           definition_instance->element_mappings.end(),
                           [member](const SourceIndexMapping& value) {
                             return value.source_label == member;
                           });
          if (mapping == definition_instance->element_mappings.end()) {
            InputFailure("unresolved-reference", raw_set.location, "ELSET",
                         raw_set.name,
                         "Assembly element-set member must resolve in "
                         "its instance.");
            return;
          }
          set.element_indices.push_back(mapping->internal_index);
        }
        definition_.element_sets.push_back(std::move(set));
      }
    }
  }

  /// @brief Builds one stable node-target index from the completed candidate.
  SourceTargetIndex BuildSourceTargetIndex() const {
    std::vector<SourceTargetIndexEntry> entries;
    std::size_t declaration_order = 0U;
    for (std::size_t node = 0U; node < definition_.nodes.size(); ++node) {
      const auto& source_id = definition_.nodes[node].source_id;
      entries.push_back({SourceEntityKind::kNode, source_id.instance_name, "",
                         source_id, static_cast<EntityIndex>(node),
                         declaration_order++});
    }
    for (const auto& set : definition_.node_sets) {
      for (const EntityIndex node : set.node_indices) {
        const auto& source_id = definition_.nodes[node].source_id;
        entries.push_back({SourceEntityKind::kNode,
                           set.instance_name.value_or(source_id.instance_name),
                           set.name, source_id, node, declaration_order++});
      }
    }
    return SourceTargetIndex{std::move(entries)};
  }

  std::optional<std::vector<EntityIndex>> ResolveNodeTarget(
      const SourceTargetResolver& resolver, const std::string& target,
      const SourceLocation& location, const std::string& keyword) {
    auto resolved = resolver.Resolve({SourceEntityKind::kNode, "", target});
    if (!resolved.HasValue()) {
      InputFailure(
          "unresolved-reference", location, keyword, target,
          "The boundary or load target must resolve unambiguously to one "
          "node or one node set.");
      return std::nullopt;
    }
    std::vector<EntityIndex> indices;
    indices.reserve(resolved.Value().size());
    for (const auto& entry : resolved.Value()) {
      indices.push_back(entry.entity_index);
    }
    return indices;
  }

  void FinalizeStep() {
    std::vector<BoundaryCondition> boundaries = model_boundaries_;
    boundaries.insert(boundaries.end(), step_.boundaries.begin(),
                      step_.boundaries.end());
    const SourceTargetIndex target_index = BuildSourceTargetIndex();
    const SourceTargetResolver target_resolver{target_index};

    std::map<std::pair<EntityIndex, int>, double> prescribed_values;
    for (const auto& boundary : boundaries) {
      auto target = ResolveNodeTarget(target_resolver, boundary.target,
                                      boundary.location, "BOUNDARY");
      if (!target) {
        return;
      }
      for (const auto node : *target) {
        for (int dof = boundary.first_dof; dof <= boundary.last_dof; ++dof) {
          const auto key = std::make_pair(node, dof);
          const auto existing = prescribed_values.find(key);
          if (existing != prescribed_values.end() &&
              existing->second != boundary.value) {
            InputFailure("conflicting-boundary-condition", boundary.location,
                         "BOUNDARY", boundary.target,
                         "Expanded boundary rows prescribe different values to "
                         "one node/DOF.");
            return;
          }
          prescribed_values[key] = boundary.value;
        }
      }
    }
    for (const auto& load : step_.loads) {
      if (!ResolveNodeTarget(target_resolver, load.target, load.location,
                             "CLOAD")) {
        return;
      }
    }

    // Static time-control values are provenance only: V0 creates exactly
    // the canonical final frame 0 and performs no increment loop here.
    definition_.steps.push_back({"Step-1", std::move(boundaries), step_.loads,
                                 step_.static_values[0], step_.static_values[1],
                                 step_.static_values[2], step_.static_values[3],
                                 step_.location});
  }

  const ParsedInput& input_;
  ModelDefinition definition_{};
  std::optional<MappingFailure> failure_;

  std::vector<RawPart> parts_;
  std::vector<RawInstance> instances_;
  std::vector<RawAssemblySet> assembly_sets_;
  std::vector<RawMaterial> materials_;
  std::vector<BoundaryCondition> model_boundaries_;
  RawStep step_{};
  std::vector<std::map<std::int64_t, std::pair<EntityIndex, EntityIndex>>>
      part_section_assignments_;
  std::vector<std::map<std::int64_t, std::pair<EntityIndex, EntityIndex>>>
      part_shell_section_assignments_;

  std::optional<std::size_t> current_part_;
  std::optional<std::size_t> pending_section_;
  std::optional<std::size_t> material_eligible_;
  std::optional<ElementFamily> model_element_family_;
  bool heading_seen_{false};
  bool part_elements_seen_{false};
  bool part_sets_seen_{false};
  bool part_sections_seen_{false};
  bool beam_section_context_active_{false};
  bool assembly_seen_{false};
  bool assembly_set_seen_{false};
  bool model_boundary_seen_{false};
  bool in_assembly_{false};
  bool in_instance_{false};
  bool step_seen_{false};
  bool in_step_{false};
  bool step_load_seen_{false};
  bool step_no_op_seen_{false};
  bool active_output_{false};
};

}  // namespace

Result<Domain> AbaqusDomainMapper::Map(const ParsedInput& input) const {
  return MappingContext{input}.Run();
}

}  // namespace fesa