import 'dart:io';

const _commonPath = 'tool/lua_runtime_defs_common.lua';
const _runtimeMarker = 'runtime = runtime';
const _gamesRoot = 'assets/games';

void main(List<String> args) {
  final checkOnly = args.contains('--check');
  final commonFile = File(_commonPath);
  if (!commonFile.existsSync()) {
    stderr.writeln('Missing common Lua runtime defs template: $_commonPath');
    exitCode = 1;
    return;
  }

  final common = _normalizeCommon(commonFile.readAsStringSync());
  var changed = false;
  final targets = _runtimeDefTargets();
  if (targets.isEmpty) {
    stderr.writeln('No Lua runtime defs targets found under $_gamesRoot');
    exitCode = 1;
    return;
  }

  for (final target in targets) {
    final targetPath = target.path;
    final current = target.existsSync() ? target.readAsStringSync() : '';
    final suffix = current.isEmpty
        ? ''
        : _gameSpecificSuffix(current, targetPath);
    final generated = suffix.isEmpty ? common : '$common\n$suffix';

    if (current == generated) {
      stdout.writeln('up to date: $targetPath');
      continue;
    }

    changed = true;
    if (checkOnly) {
      stderr.writeln('out of date: $targetPath');
    } else {
      target.writeAsStringSync(generated);
      stdout.writeln('generated: $targetPath');
    }
  }

  if (checkOnly && changed) {
    stderr.writeln(
      'Lua runtime defs are out of date. Run: dart run tool/generate_lua_runtime_defs.dart',
    );
    exitCode = 1;
  }
}

List<File> _runtimeDefTargets() {
  final root = Directory(_gamesRoot);
  if (!root.existsSync()) {
    return const [];
  }
  final targets = <File>[];
  for (final entity in root.listSync()) {
    if (entity is! Directory) {
      continue;
    }
    final scripts = Directory('${entity.path}/scripts');
    if (!scripts.existsSync()) {
      continue;
    }
    targets.add(File('${scripts.path}/runtime_defs.lua'));
  }
  targets.sort((a, b) => a.path.compareTo(b.path));
  return targets;
}

String _normalizeCommon(String source) {
  final text = source.replaceAll('\r\n', '\n').trimRight();
  if (!text.contains(_runtimeMarker)) {
    throw const FormatException(
      'Common template must contain runtime = runtime',
    );
  }
  return '$text\n';
}

String _gameSpecificSuffix(String source, String targetPath) {
  final text = source.replaceAll('\r\n', '\n');
  final index = text.indexOf(_runtimeMarker);
  if (index < 0) {
    throw FormatException('$targetPath must contain $_runtimeMarker');
  }
  final suffixStart = index + _runtimeMarker.length;
  return text.substring(suffixStart).trimLeft();
}