#!/usr/bin/env bash
# quick-diff.sh — compare skill file mtimes against results.json evaluated_at
# Usage: quick-diff.sh RESULTS_JSON [CWD_SKILLS_DIR]
# Output: JSON array of changed/new files to stdout (empty [] if no changes)
#
# When CWD_SKILLS_DIR is omitted, defaults to $PWD/.claude/skills so the
# script always picks up project-level skills without relying on the caller.
#
# Environment:
#   SKILL_STOCKTAKE_GLOBAL_DIR   Override ~/.claude/skills (for testing only;
#                                do not set in production — intended for bats tests)
#   SKILL_STOCKTAKE_PROJECT_DIR  Override project dir detection (for testing only)

set -euo pipefail

sort_nul_file() {
  local input_file="$1"
  local sorted_file="${input_file}.sorted"
  node -e '
    const fs = require("fs");
    const input = fs.readFileSync(0);
    const records = [];
    let start = 0;
    for (let index = 0; index < input.length; index += 1) {
      if (input[index] === 0) {
        records.push(input.subarray(start, index + 1));
        start = index + 1;
      }
    }
    if (start < input.length) records.push(input.subarray(start));
    records.sort(Buffer.compare);
    process.stdout.write(Buffer.concat(records));
  ' <"$input_file" >"$sorted_file"
  mv "$sorted_file" "$input_file"
}

RESULTS_JSON="${1:-}"
CWD_SKILLS_DIR="${SKILL_STOCKTAKE_PROJECT_DIR:-${2:-$PWD/.claude/skills}}"
GLOBAL_DIR="${SKILL_STOCKTAKE_GLOBAL_DIR:-$HOME/.claude/skills}"

if [[ -z "$RESULTS_JSON" || ! -f "$RESULTS_JSON" ]]; then
  echo "Error: RESULTS_JSON not found: ${RESULTS_JSON:-<empty>}" >&2
  exit 1
fi

# Validate CWD_SKILLS_DIR looks like a .claude/skills path (defense-in-depth).
# Only warn when the path exists — a nonexistent path poses no traversal risk.
if [[ -n "$CWD_SKILLS_DIR" && -d "$CWD_SKILLS_DIR" && "$CWD_SKILLS_DIR" != */.claude/skills* ]]; then
  echo "Warning: CWD_SKILLS_DIR does not look like a .claude/skills path: $CWD_SKILLS_DIR" >&2
fi

evaluated_at=$(jq -r '.evaluated_at' "$RESULTS_JSON")

# Fail fast on a missing or malformed evaluated_at rather than producing
# unpredictable results from ISO 8601 string comparison against "null".
if [[ ! "$evaluated_at" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}Z$ ]]; then
  echo "Error: invalid or missing evaluated_at in $RESULTS_JSON: $evaluated_at" >&2
  exit 1
fi

tmpdir=$(mktemp -d)
# Use a function to avoid embedding $tmpdir in a quoted string (prevents injection
# if TMPDIR were crafted to contain shell metacharacters).
_cleanup() { rm -rf "$tmpdir"; }
trap _cleanup EXIT

# Shared counter across process_dir calls — intentionally NOT local
i=0

process_dir() {
  local dir="$1"
  local find_out="$tmpdir/.find-stdout"
  local find_err="$tmpdir/.find-stderr"
  # Capture find's exit status and stderr instead of discarding them: with -L,
  # a broken symlink or unreadable directory makes find skip that entry AND
  # exit non-zero, which would otherwise silently under-count skills.
  # NUL-delimited (-print0 / sort_nul_file / read -d '') so a path containing a
  # literal newline can't desync record boundaries — paths here are untrusted.
  if ! find -L "$dir" -name "SKILL.md" -type f -print0 >"$find_out" 2>"$find_err"; then
    echo "Warning: find encountered errors while scanning $dir (broken symlinks or permission issues may cause skills to be missed):" >&2
    cat "$find_err" >&2
  fi
  sort_nul_file "$find_out"

  while IFS= read -r -d '' file; do
    local mtime dp is_new
    mtime=$(date -u -r "$file" +%Y-%m-%dT%H:%M:%SZ)
    dp="${file/#$HOME/~}"

    # Keep path comparison structured so literal newlines remain part of one
    # JSON string instead of becoming ambiguous line-delimited records.
    if jq -e --arg path "$dp" '.skills | any(.path == $path)' "$RESULTS_JSON" >/dev/null 2>&1; then
      is_new="false"
      # Known file: only emit if mtime changed (ISO 8601 string comparison is safe)
      [[ "$mtime" > "$evaluated_at" ]] || continue
    else
      is_new="true"
      # New file: always emit regardless of mtime
    fi

    jq -n \
      --arg path "$dp" \
      --arg mtime "$mtime" \
      --argjson is_new "$is_new" \
      '{path:$path,mtime:$mtime,is_new:$is_new}' \
      > "$tmpdir/$i.json"
    i=$((i+1))
  done < "$find_out"
}

[[ -d "$GLOBAL_DIR" ]] && process_dir "$GLOBAL_DIR"
[[ -n "$CWD_SKILLS_DIR" && -d "$CWD_SKILLS_DIR" ]] && process_dir "$CWD_SKILLS_DIR"

if [[ $i -eq 0 ]]; then
  echo "[]"
else
  jq -s '.' "$tmpdir"/*.json
fi