/**
 * Provider Registry
 *
 * 管理所有注册的提供商（内置 + 自定义）
 */

import type { LanguageModel } from 'ai';
import type {
  ProviderInfo,
  ProviderConfig,
  CustomProviderDefinition,
  RegisteredProvider,
  ConnectionTestResult,
  ProviderFactory,
  ModelInfo,
  ProviderListItem,
  ProviderDetail,
} from './types.js';
import { builtinProviders, isBuiltinProvider } from './builtin/index.js';
import {
  loadProvidersConfig,
  saveProvidersConfig,
  resolveApiKey,
} from './config.js';
import {
  testOpenAICompatibleConnection,
  createOpenAICompatibleFactory,
  isValidProviderId,
  isValidUrl,
} from './utils.js';

/**
 * Provider Registry
 * 管理所有提供商的单例类
 */
export class ProviderRegistry {
  /** 已注册的提供商 */
  private providers: Map<string, RegisteredProvider> = new Map();

  /** 提供商配置 */
  private configs: Map<string, ProviderConfig> = new Map();

  /** 自定义提供商定义 */
  private customDefinitions: Map<string, CustomProviderDefinition> = new Map();

  /** 是否已完全初始化（包括用户配置） */
  private fullyInitialized = false;

  constructor() {
    // 同步初始化内置提供商（不需要异步加载）
    this.initBuiltinProviders();
  }

  /**
   * 同步初始化内置提供商
   */
  private initBuiltinProviders(): void {
    for (const [id, builtin] of Object.entries(builtinProviders)) {
      this.providers.set(id, {
        info: builtin.info,
        factory: builtin.factory,
      });
    }
  }

  /**
   * 完整初始化 Registry
   * 加载用户配置（自定义提供商和配置）
   */
  async init(): Promise<void> {
    if (this.fullyInitialized) return;

    // 加载用户配置（从 ~/.ai-terminal-assistant/providers.json）
    const config = await loadProvidersConfig();

    // 加载自定义提供商
    if (config.providers) {
      for (const [id, definition] of Object.entries(config.providers)) {
        this.registerCustomInternal(definition);
      }
    }

    // 加载提供商配置
    if (config.configs) {
      for (const [id, providerConfig] of Object.entries(config.configs)) {
        this.configs.set(id, providerConfig);
      }
    }

    this.fullyInitialized = true;
  }

  /**
   * 检查是否已完全初始化
   */
  isInitialized(): boolean {
    return this.fullyInitialized;
  }

  /**
   * 确保内置提供商已加载（总是true，因为构造函数中已初始化）
   * 保留此方法以便未来可能需要的检查
   */
  private ensureInitialized(): void {
    // 内置提供商在构造函数中同步初始化，总是可用
    // 用户配置需要调用 init() 异步加载
  }

  /**
   * 列出所有提供商
   */
  list(): ProviderInfo[] {
    this.ensureInitialized();
    return Array.from(this.providers.values()).map((p) => p.info);
  }

  /**
   * 列出所有提供商（API 响应格式）
   */
  listForApi(): ProviderListItem[] {
    this.ensureInitialized();
    return Array.from(this.providers.entries()).map(([id, provider]) => {
      const config = this.configs.get(id);
      const apiKey = resolveApiKey(config);
      const customModels = config?.customModels ?? [];

      return {
        id,
        name: provider.info.name,
        description: provider.info.description,
        builtin: provider.info.builtin,
        enabled: config?.enabled ?? true,
        hasApiKey: !!apiKey,
        modelCount: provider.info.models.length + customModels.length,
      };
    });
  }

  /**
   * 获取提供商
   */
  get(id: string): RegisteredProvider | undefined {
    this.ensureInitialized();
    return this.providers.get(id);
  }

  /**
   * 获取提供商信息
   */
  getInfo(id: string): ProviderInfo | undefined {
    return this.get(id)?.info;
  }

  /**
   * 获取提供商详情（API 响应格式）
   */
  getDetail(id: string): ProviderDetail | undefined {
    this.ensureInitialized();
    const provider = this.providers.get(id);
    if (!provider) return undefined;

    const config = this.configs.get(id);
    const apiKey = resolveApiKey(config);

    return {
      id,
      name: provider.info.name,
      description: provider.info.description,
      builtin: provider.info.builtin,
      baseUrl: config?.baseUrl ?? provider.info.baseUrl,
      models: provider.info.models,
      allowCustomModels: provider.info.allowCustomModels ?? false,
      config: {
        enabled: config?.enabled ?? true,
        hasApiKey: !!apiKey,
        baseUrl: config?.baseUrl,
        customModels: config?.customModels ?? [],
      },
    };
  }

  /**
   * 检查提供商是否存在
   */
  has(id: string): boolean {
    this.ensureInitialized();
    return this.providers.has(id);
  }

  /**
   * 内部注册自定义提供商
   */
  private registerCustomInternal(definition: CustomProviderDefinition): void {
    const factory = createOpenAICompatibleFactory(definition.baseUrl);

    const info: ProviderInfo = {
      id: definition.id,
      name: definition.name,
      description: definition.description,
      builtin: false,
      baseUrl: definition.baseUrl,
      models: definition.models ?? [],
      allowCustomModels: definition.allowCustomModels ?? true,
    };

    this.providers.set(definition.id, { info, factory });
    this.customDefinitions.set(definition.id, definition);
  }

  /**
   * 注册自定义提供商
   */
  registerCustom(definition: CustomProviderDefinition): void {
    this.ensureInitialized();

    // 验证 ID
    if (!isValidProviderId(definition.id)) {
      throw new Error(`Invalid provider ID: ${definition.id}`);
    }

    // 不能覆盖内置提供商
    if (isBuiltinProvider(definition.id)) {
      throw new Error(`Cannot override builtin provider: ${definition.id}`);
    }

    // 验证 URL
    if (!isValidUrl(definition.baseUrl)) {
      throw new Error(`Invalid base URL: ${definition.baseUrl}`);
    }

    this.registerCustomInternal(definition);
  }

  /**
   * 移除自定义提供商
   */
  removeCustom(id: string): boolean {
    this.ensureInitialized();

    // 不能删除内置提供商
    if (isBuiltinProvider(id)) {
      throw new Error(`Cannot remove builtin provider: ${id}`);
    }

    const removed = this.providers.delete(id);
    this.customDefinitions.delete(id);
    this.configs.delete(id);

    return removed;
  }

  /**
   * 设置提供商配置
   */
  setConfig(id: string, config: ProviderConfig): void {
    this.ensureInitialized();

    if (!this.providers.has(id)) {
      throw new Error(`Provider not found: ${id}`);
    }

    this.configs.set(id, { ...config, id });
  }

  /**
   * 获取提供商配置
   */
  getConfig(id: string): ProviderConfig | undefined {
    this.ensureInitialized();
    return this.configs.get(id);
  }

  /**
   * 获取所有配置
   */
  getAllConfigs(): Record<string, ProviderConfig> {
    this.ensureInitialized();
    return Object.fromEntries(this.configs);
  }

  /**
   * 获取提供商的模型列表
   */
  getModels(providerId: string): ModelInfo[] {
    this.ensureInitialized();

    const provider = this.providers.get(providerId);
    if (!provider) return [];

    const config = this.configs.get(providerId);
    const customModels = config?.customModels ?? [];

    return [...provider.info.models, ...customModels];
  }

  /**
   * 获取指定模型的详细信息
   * @param providerId 提供商 ID
   * @param modelId 模型 ID
   * @returns 模型信息，未找到时返回 undefined
   */
  getModelInfo(providerId: string, modelId: string): ModelInfo | undefined {
    const models = this.getModels(providerId);
    return models.find((m) => m.id === modelId);
  }

  /**
   * 添加自定义模型
   */
  addCustomModel(providerId: string, model: ModelInfo): void {
    this.ensureInitialized();

    if (!this.providers.has(providerId)) {
      throw new Error(`Provider not found: ${providerId}`);
    }

    const config = this.configs.get(providerId) ?? { id: providerId };
    const customModels = config.customModels ?? [];

    // 检查是否已存在
    if (customModels.some((m) => m.id === model.id)) {
      throw new Error(`Model already exists: ${model.id}`);
    }

    customModels.push(model);
    this.configs.set(providerId, { ...config, customModels });
  }

  /**
   * 移除自定义模型
   */
  removeCustomModel(providerId: string, modelId: string): boolean {
    this.ensureInitialized();

    const config = this.configs.get(providerId);
    if (!config?.customModels) return false;

    const index = config.customModels.findIndex((m) => m.id === modelId);
    if (index === -1) return false;

    config.customModels.splice(index, 1);
    this.configs.set(providerId, config);

    return true;
  }

  /**
   * 测试提供商连接
   */
  async testConnection(
    providerId: string,
    apiKey?: string
  ): Promise<ConnectionTestResult> {
    this.ensureInitialized();

    const provider = this.providers.get(providerId);
    if (!provider) {
      return { success: false, error: `Provider not found: ${providerId}` };
    }

    const config = this.configs.get(providerId);
    const resolvedApiKey = apiKey ?? resolveApiKey(config);

    if (!resolvedApiKey && !provider.info.baseUrl?.includes('localhost')) {
      return { success: false, error: 'API key not configured' };
    }

    const baseUrl = config?.baseUrl ?? provider.info.baseUrl;

    // 对于自定义提供商，使用 OpenAI 兼容测试
    if (!provider.info.builtin && baseUrl) {
      return testOpenAICompatibleConnection(resolvedApiKey ?? '', baseUrl);
    }

    // 对于内置提供商，简单验证 API key 存在
    return {
      success: !!resolvedApiKey,
      error: resolvedApiKey ? undefined : 'API key not configured',
    };
  }

  /**
   * 获取模型工厂函数
   */
  getModelFactory(
    providerId: string,
    options?: { apiKey?: string; baseUrl?: string }
  ): (model: string) => LanguageModel {
    this.ensureInitialized();

    const provider = this.providers.get(providerId);
    if (!provider) {
      throw new Error(`Provider not found: ${providerId}`);
    }

    const config = this.configs.get(providerId);
    const apiKey = options?.apiKey ?? resolveApiKey(config);
    const baseUrl = options?.baseUrl ?? config?.baseUrl ?? provider.info.baseUrl;

    if (!apiKey) {
      throw new Error(`API key not configured for provider: ${providerId}`);
    }

    return provider.factory({ apiKey, baseUrl });
  }

  /**
   * 保存配置到文件
   */
  async saveConfig(): Promise<void> {
    this.ensureInitialized();

    const config = {
      providers: Object.fromEntries(this.customDefinitions),
      configs: Object.fromEntries(this.configs),
    };

    await saveProvidersConfig(config);
  }

  /**
   * 重新加载配置
   */
  async reloadConfig(): Promise<void> {
    this.fullyInitialized = false;
    this.configs.clear();
    this.customDefinitions.clear();

    // 清除自定义提供商，保留内置提供商
    for (const [id, provider] of this.providers.entries()) {
      if (!provider.info.builtin) {
        this.providers.delete(id);
      }
    }

    await this.init();
  }
}

/** 单例实例 */
export const providerRegistry = new ProviderRegistry();

/** 获取 ProviderRegistry 实例 */
export function getProviderRegistry(): ProviderRegistry {
  return providerRegistry;
}