// ============================================================================
// sync_deps.dart
//
// Single source of truth for external dependency versions.
// Reads dependencies.yaml and propagates versions to all pubspec.yaml files.
//
// Usage:
//   dart run tool/sync_deps.dart sync   - Update all pubspec.yaml from dependencies.yaml
//   dart run tool/sync_deps.dart check  - Verify all pubspec.yaml are in sync (CI-friendly)
// ============================================================================

import 'dart:io';

const _depsFileName = 'dependencies.yaml';

void main(List<String> args) async {
  if (args.isEmpty) {
    _printUsage();
    exit(1);
  }

  final command = args.first;
  final repoRoot = _findRepoRoot();
  final depsFile = File('${repoRoot.path}/$_depsFileName');

  if (!depsFile.existsSync()) {
    stderr.writeln('error: $_depsFileName not found at ${depsFile.path}');
    exit(1);
  }

  final catalog = _parseDependenciesYaml(depsFile.readAsStringSync());
  final pubspecs = _findPubspecs(repoRoot);

  switch (command) {
    case 'sync':
      _syncCommand(pubspecs, catalog);
    case 'check':
      _checkCommand(pubspecs, catalog);
    default:
      _printUsage();
      exit(1);
  }
}

void _printUsage() {
  stderr.writeln('Usage: dart run tool/sync_deps.dart <sync|check>');
  stderr.writeln('  sync   - Propagate versions from $_depsFileName to all pubspec.yaml');
  stderr.writeln('  check  - Verify all pubspec.yaml are in sync (exit 1 if drift detected)');
}

Directory _findRepoRoot() {
  var dir = Directory.current;
  while (dir.parent.path != dir.path) {
    if (File('${dir.path}/$_depsFileName').existsSync() &&
        File('${dir.path}/melos.yaml').existsSync() == false &&
        File('${dir.path}/pubspec.yaml').existsSync()) {
      return dir;
    }
    if (File('${dir.path}/$_depsFileName').existsSync()) return dir;
    dir = dir.parent;
  }
  return Directory.current;
}

class _Catalog {
  final Map<String, String> dependencies;
  final Map<String, String> devDependencies;
  _Catalog(this.dependencies, this.devDependencies);

  String? versionFor(String depName, {required bool isDev}) {
    // Dev deps may also be looked up in regular deps as fallback
    return (isDev ? devDependencies[depName] : dependencies[depName]) ??
        dependencies[depName] ??
        devDependencies[depName];
  }
}

_Catalog _parseDependenciesYaml(String content) {
  final lines = content.split('\n');
  final deps = <String, String>{};
  final devDeps = <String, String>{};
  String? section;
  for (final raw in lines) {
    final line = raw.replaceAll('\r', '');
    final trimmed = line.trim();
    if (trimmed.isEmpty || trimmed.startsWith('#')) continue;

    // Section headers (no leading space)
    if (line == 'dependencies:') {
      section = 'deps';
      continue;
    }
    if (line == 'dev_dependencies:') {
      section = 'dev_deps';
      continue;
    }
    // Top-level key resets section
    if (RegExp(r'^[a-zA-Z]').hasMatch(line)) {
      section = null;
      continue;
    }

    // Match `  pkg: version` (allow comments at end)
    final match = RegExp(r'^\s\s+([a-zA-Z_][a-zA-Z0-9_]*)\s*:\s*(\S+)').firstMatch(line);
    if (match == null) continue;
    final pkg = match.group(1)!;
    final ver = match.group(2)!;

    if (section == 'deps') {
      deps[pkg] = ver;
    } else if (section == 'dev_deps') {
      devDeps[pkg] = ver;
    }
  }
  return _Catalog(deps, devDeps);
}

List<File> _findPubspecs(Directory root) {
  final result = <File>[];
  void scan(Directory dir) {
    final name = dir.path.split('/').last;
    if (const {'.git', '.dart_tool', 'build', 'node_modules', '.fvm', 'Pods', 'example'}
        .contains(name)) {
      return;
    }
    for (final entity in dir.listSync(followLinks: false)) {
      if (entity is File && entity.path.endsWith('/pubspec.yaml')) {
        // Skip root pubspec
        if (entity.path == '${root.path}/pubspec.yaml') continue;
        result.add(entity);
      } else if (entity is Directory) {
        scan(entity);
      }
    }
  }
  scan(root);
  return result;
}

void _syncCommand(List<File> pubspecs, _Catalog catalog) {
  var totalReplacements = 0;
  var filesChanged = 0;
  for (final file in pubspecs) {
    final content = file.readAsStringSync();
    final result = _processPubspec(content, catalog);
    if (result.replacements > 0) {
      file.writeAsStringSync(result.content);
      filesChanged++;
      totalReplacements += result.replacements;
      print('  updated: ${file.path} (${result.replacements} deps)');
    }
  }
  print('');
  print('Synced $totalReplacements dependencies across $filesChanged files.');
  if (totalReplacements == 0) {
    print('All packages already in sync.');
  }
}

void _checkCommand(List<File> pubspecs, _Catalog catalog) {
  final drifts = <String>[];
  for (final file in pubspecs) {
    final content = file.readAsStringSync();
    final result = _processPubspec(content, catalog);
    if (result.drifts.isNotEmpty) {
      for (final drift in result.drifts) {
        drifts.add('${file.path}: ${drift}');
      }
    }
  }
  if (drifts.isEmpty) {
    print('OK: All pubspec.yaml files are in sync with $_depsFileName');
    exit(0);
  } else {
    stderr.writeln('FAIL: Found ${drifts.length} dependency drifts:');
    stderr.writeln('');
    for (final drift in drifts) {
      stderr.writeln('  $drift');
    }
    stderr.writeln('');
    stderr.writeln('Run `melos run sync-deps` to fix.');
    exit(1);
  }
}

class _ProcessResult {
  final String content;
  final int replacements;
  final List<String> drifts;
  _ProcessResult(this.content, this.replacements, this.drifts);
}

_ProcessResult _processPubspec(String content, _Catalog catalog) {
  final lines = content.split('\n');
  final newLines = <String>[];
  String? section;
  var replacements = 0;
  final drifts = <String>[];

  for (final line in lines) {
    final stripped = line.replaceAll('\r', '');

    // Section detection
    if (stripped == 'dependencies:') {
      section = 'deps';
      newLines.add(stripped);
      continue;
    }
    if (stripped == 'dev_dependencies:') {
      section = 'dev_deps';
      newLines.add(stripped);
      continue;
    }
    if (stripped == 'dependency_overrides:') {
      section = 'overrides';
      newLines.add(stripped);
      continue;
    }
    // Top-level resets section
    if (RegExp(r'^[a-zA-Z]').hasMatch(stripped)) {
      section = null;
      newLines.add(stripped);
      continue;
    }

    if (section == 'deps' || section == 'dev_deps') {
      // Match `  pkg_name: version` where version is ^x.y.z, x.y.z, etc.
      final match = RegExp(r'^(\s+)([a-zA-Z_][a-zA-Z0-9_]*)\s*:\s*(\^?[\d.]+(?:[+\-]\S+)?)\s*$')
          .firstMatch(stripped);
      if (match != null) {
        final indent = match.group(1)!;
        final depName = match.group(2)!;
        final currentVer = match.group(3)!;

        // Don't touch SDK declarations or special keys
        if (depName == 'sdk' || depName == 'flutter') {
          newLines.add(stripped);
          continue;
        }

        final targetVer = catalog.versionFor(depName, isDev: section == 'dev_deps');
        if (targetVer != null && targetVer != currentVer) {
          newLines.add('$indent$depName: $targetVer');
          replacements++;
          drifts.add('$depName: $currentVer (expected $targetVer)');
          continue;
        }
      }
    }
    newLines.add(stripped);
  }

  return _ProcessResult(newLines.join('\n'), replacements, drifts);
}