#!/usr/bin/env bash
# allocate-address.sh — atomic creation-order address allocation for the vault.
#
# Reserves the next address of the form c-NNNNNN and increments the counter
# under an exclusive flock. On missing counter file, recovers by scanning the
# vault for the highest existing c-NNNNNN in page frontmatter and resuming from
# max+1. Never silently resets to 1 in a non-empty vault.
#
# Usage:
#   ./scripts/allocate-address.sh           # prints the reserved address (e.g. c-000042) to stdout
#   ./scripts/allocate-address.sh --peek    # prints the next value without incrementing
#   ./scripts/allocate-address.sh --rebuild # recomputes counter from max observed and exits
#
# Exit codes:
#   0 — success
#   1 — lock acquisition failed (another writer is holding the lock)
#   2 — vault-meta directory missing and cannot be created
#   3 — counter value corrupt or non-numeric

set -euo pipefail

VAULT_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
COUNTER_FILE="${VAULT_ROOT}/.vault-meta/address-counter.txt"
LOCK_FILE="${VAULT_ROOT}/.vault-meta/.address.lock"
WIKI_DIR="${VAULT_ROOT}/wiki"

MODE="${1:-allocate}"

mkdir -p "$(dirname "$COUNTER_FILE")" || {
  echo "ERR: cannot create .vault-meta/" >&2
  exit 2
}

# Acquire exclusive lock with 5-second timeout. Release automatically on scope exit.
exec 9>"$LOCK_FILE"
if ! flock -x -w 5 9; then
  echo "ERR: could not acquire address allocator lock within 5s" >&2
  exit 1
fi

scan_max_c_address() {
  # Emit the largest NNNNNN from "address: c-NNNNNN" lines that appear inside
  # the FIRST YAML frontmatter block of each wiki .md file. Code-block examples
  # and body prose are excluded. Returns 0 if none found.
  if [ ! -d "$WIKI_DIR" ]; then
    echo 0
    return
  fi
  find "$WIKI_DIR" -type f -name '*.md' -print0 2>/dev/null \
    | xargs -0 awk '
        FNR == 1 { state = "pre"; next_is_fm = ($0 == "---") ? 1 : 0 }
        FNR == 1 && $0 == "---" { state = "fm"; next }
        state == "fm" && $0 == "---" { state = "body"; nextfile }
        state == "fm" && match($0, /^address:[[:space:]]+c-[0-9]{6}[[:space:]]*$/) {
          if (match($0, /c-[0-9]{6}/)) {
            print substr($0, RSTART, RLENGTH)
          }
        }
      ' 2>/dev/null \
    | sed 's/^c-0*//;s/^$/0/' \
    | sort -n \
    | tail -1 \
    | awk 'BEGIN{n=0} {n=$0} END{print (n+0)}'
}

read_or_recover_counter() {
  if [ ! -f "$COUNTER_FILE" ]; then
    local max_c
    max_c="$(scan_max_c_address)"
    echo $((max_c + 1)) > "$COUNTER_FILE"
    echo "INFO: counter file missing; recovered from vault scan, set to $((max_c + 1))" >&2
  fi
  local raw
  raw="$(cat "$COUNTER_FILE")"
  if ! [[ "$raw" =~ ^[0-9]+$ ]]; then
    echo "ERR: counter file content is not a positive integer: $raw" >&2
    exit 3
  fi
  echo "$raw"
}

case "$MODE" in
  --peek)
    read_or_recover_counter
    ;;
  --rebuild)
    max_c="$(scan_max_c_address)"
    echo $((max_c + 1)) > "$COUNTER_FILE"
    echo "Counter rebuilt: next = $((max_c + 1))"
    ;;
  allocate|"")
    current="$(read_or_recover_counter)"
    next=$((current + 1))
    echo "$next" > "$COUNTER_FILE"
    printf 'c-%06d\n' "$current"
    ;;
  *)
    echo "ERR: unknown mode: $MODE" >&2
    echo "Usage: $0 [allocate|--peek|--rebuild]" >&2
    exit 3
    ;;
esac