import json
import subprocess
import sys
from pathlib import Path


SOURCE_SUFFIXES = {".cs"}
TEST_SUFFIXES = {".cs"}


def _repo_root(cwd: Path) -> Path:
    try:
        root = subprocess.check_output(
            ["git", "rev-parse", "--show-toplevel"],
            cwd=cwd,
            text=True,
            stderr=subprocess.DEVNULL,
        ).strip()
    except (subprocess.CalledProcessError, FileNotFoundError):
        return cwd
    return Path(root)


def _extract_patch_paths(command: str) -> list[str]:
    prefixes = (
        "*** Add File: ",
        "*** Update File: ",
        "*** Delete File: ",
        "*** Move to: ",
    )
    paths: list[str] = []
    for raw_line in command.splitlines():
        line = raw_line.strip()
        for prefix in prefixes:
            if line.startswith(prefix):
                paths.append(line[len(prefix) :].strip())
                break
    return paths


def _touched_paths(payload: dict) -> list[str]:
    tool_input = payload.get("tool_input", {})
    if not isinstance(tool_input, dict):
        return []

    file_path = tool_input.get("file_path")
    if isinstance(file_path, str) and file_path:
        return [file_path]

    command = tool_input.get("command")
    if isinstance(command, str):
        return _extract_patch_paths(command)

    return []


def _normalize(path_text: str) -> str:
    return path_text.replace("\\", "/").lower()


def _path_segments(path_text: str) -> list[str]:
    return [segment for segment in _normalize(path_text).split("/") if segment]


def _is_ignored_path(path_text: str) -> bool:
    return any(segment in {"bin", "obj"} for segment in _path_segments(path_text))


def _is_test_path(path_text: str) -> bool:
    path = Path(path_text)
    if path.suffix.lower() not in TEST_SUFFIXES:
        return False

    segments = _path_segments(path_text)
    name = segments[-1] if segments else ""
    directories = segments[:-1]
    return (
        any(
            segment in {"test", "tests"}
            or segment.endswith(".test")
            or segment.endswith(".tests")
            for segment in directories
        )
        or name.endswith("test.cs")
        or name.endswith("tests.cs")
    )


def _token(text: str) -> str:
    return "".join(ch for ch in text.lower() if ch.isalnum())


def _candidate_test_paths(paths: list[str], cwd: Path, root: Path) -> list[Path]:
    candidates: list[Path] = []
    for path_text in paths:
        resolved = _resolve_path(path_text, cwd)
        if _is_test_path(str(resolved)) and not _is_ignored_path(str(resolved)):
            candidates.append(resolved)

    for candidate in root.rglob("*"):
        if (
            candidate.is_file()
            and candidate.suffix.lower() in TEST_SUFFIXES
            and _is_test_path(str(candidate))
            and not _is_ignored_path(str(candidate))
        ):
            candidates.append(candidate)

    return candidates


def _has_related_test(path: Path, candidate_tests: list[Path]) -> bool:
    source_token = _token(path.stem)
    for test_path in candidate_tests:
        test_token = _token(test_path.stem)
        if source_token and source_token in test_token:
            return True
    return False


def _is_exempt(path_text: str) -> bool:
    return _is_test_path(path_text)


def _resolve_path(path_text: str, cwd: Path) -> Path:
    path = Path(path_text)
    if path.is_absolute():
        return path
    return (cwd / path).resolve()


def _base_name(path: Path) -> str:
    return path.stem


def _guarded_paths(paths: list[str], cwd: Path, root: Path) -> list[str]:
    missing_tests: list[str] = []
    candidate_tests = _candidate_test_paths(paths, cwd, root)
    for path_text in paths:
        if _is_exempt(path_text):
            continue

        path = _resolve_path(path_text, cwd)
        if path.suffix.lower() not in SOURCE_SUFFIXES:
            continue
        if not _has_related_test(path, candidate_tests):
            missing_tests.append(_base_name(path))

    return missing_tests


def main() -> int:
    try:
        payload = json.load(sys.stdin)
    except json.JSONDecodeError:
        return 0

    cwd = Path(payload.get("cwd") or Path.cwd())
    root = _repo_root(cwd)
    missing_tests = _guarded_paths(_touched_paths(payload), cwd, root)
    if not missing_tests:
        return 0

    names = ", ".join(sorted(set(missing_tests)))
    print(
        json.dumps(
            {
                "hookSpecificOutput": {
                    "hookEventName": "PreToolUse",
                    "permissionDecision": "deny",
                    "permissionDecisionReason": (
                        "TDD GUARD: missing C# test file for "
                        f"{names}. Write or add the test first."
                    ),
                }
            }
        )
    )
    return 0


if __name__ == "__main__":
    raise SystemExit(main())