import 'dart:io';

import 'package:mustache_template/mustache_template.dart';
import 'package:path/path.dart' as p;
import 'package:swagger_generator_flutter/core/config_repository.dart';
import 'package:swagger_generator_flutter/utils/path_resolver.dart';

part 'template/template_loader.dart';

/// 模板渲染器
/// 负责加载和渲染 Mustache 模板，支持文件覆盖与内置模板
class TemplateRenderer {
  TemplateRenderer({
    String? templateRoot,
    List<String>? extraTemplateRoots,
  })  : _loader = TemplateLoader(
          customRoot: templateRoot,
          extraRoots: extraTemplateRoots,
        ),
        _baseContext = _buildBaseContext();

  final TemplateLoader _loader;
  final Map<String, Template> _templateCache = {};
  final Map<String, dynamic> _baseContext;

  /// 渲染模板
  ///
  /// [templateName] 模板名称（不含 .mustache 扩展名）
  /// [data] 模板数据
  String render(
    String templateName,
    Map<String, dynamic> data, {
    Map<String, String>? partials,
  }) {
    final template = _getTemplate(templateName);
    final context = {..._baseContext, ...data};
    return template.renderString(context);
  }

  /// 部分模板解析器
  Template? _partialResolver(String name) {
    try {
      return _getTemplate(name);
    } on Exception {
      return null;
    }
  }

  /// 获取模板（带缓存）
  Template _getTemplate(String templateName) {
    if (_templateCache.containsKey(templateName)) {
      return _templateCache[templateName]!;
    }

    final source = _getTemplateSource(templateName);
    final template = Template(
      source,
      name: templateName,
      lenient: true,
      htmlEscapeValues: false,
      partialResolver: _partialResolver,
    );
    _templateCache[templateName] = template;
    return template;
  }

  /// 获取模板源码：优先文件，其次内嵌
  String _getTemplateSource(String templateName) {
    final fileTemplate = _loader.load(templateName);
    if (fileTemplate != null) {
      return fileTemplate;
    }

    throw Exception('Template not found in file system: $templateName');
  }

  /// 清除模板缓存
  void clearCache() {
    _templateCache.clear();
    _loader.clearCache();
  }

  static Map<String, dynamic> _buildBaseContext() {
    // Load once synchronously to avoid repeated disk IO
    final config = ConfigRepository.loadSync();
    return {
      'generatorName': config.generatorName,
      'author': config.author,
      'copyright': config.copyright,
    };
  }
}