/*
 * AgentMail 鸿蒙客户端 — SSE 多账号实时推送服务
 * 每个账号各建一条 SSE 连接（各带自己的 user_key）
 * AccountManager 维护连接集合，按 accountId 分发事件
 */
import { http } from '@kit.NetworkKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
/* UTF-8 解码用（见 `arrayBufferToString` 的注释：逐字节 fromCharCode 会把中文解成乱码） */
import { util } from '@kit.ArkTS';
import { AccountManager, AccountInfo } from './AccountManager';
import { normalizeApiBase } from '../model/ApiBase';

const DOMAIN = 0x0001;
const TAG = 'SseService';

/** SSE 事件数据 */
export class SseEvent {
  type: string = '';
  data: string = '';
  accountId: string = '';
}

/** SSE 回调 */
export type SseListener = (event: SseEvent) => void;

/** SSE 连接状态 */
export type SseStatus = 'disconnected' | 'connecting' | 'connected';

/** SSE 状态回调 */
export type SseStatusListener = (status: SseStatus) => void;

/** 单个账号的 SSE 连接状态（纯数据） */
export class SseConnection {
  accountId: string = '';
  server: string = '';
  token: string = '';
  httpRequest: http.HttpRequest | null = null;
  listeners: SseListener[] = [];
  status: SseStatus = 'disconnected';
  reconnectTimer: number = 0;
  buffer: string = '';
  connected: boolean = false;
  /*
   * ★★ 2026-09-24：**每连接一个** 解码器（不要共享）。
   * `decodeToString(..., {stream:true})` 会把「被 TCP 分片切断的半个汉字」
   * 存在**该解码器实例内部**，等下一片到了再拼。多个连接共用同一个实例
   * 就会把一个账号的半个字与另一个账号的半截拼在一起 ⇒ 乱码。
   */
  decoder: util.TextDecoder | null = null;
}

export class SseService {
  private static instance: SseService | null = null;
  private connections: Map<string, SseConnection> = new Map();
  private globalListeners: SseListener[] = [];
  private globalStatusListeners: SseStatusListener[] = [];

  static getInstance(): SseService {
    if (SseService.instance === null) {
      SseService.instance = new SseService();
    }
    return SseService.instance;
  }

  private constructor() {}

  /** 添加全局事件监听（所有账号的事件都会收到） */
  addListener(listener: SseListener): void {
    this.globalListeners.push(listener);
  }

  /** 移除全局事件监听 */
  removeListener(listener: SseListener): void {
    const idx: number = this.globalListeners.indexOf(listener);
    if (idx >= 0) {
      this.globalListeners.splice(idx, 1);
    }
  }

  /** 添加全局状态监听 */
  addStatusListener(listener: SseStatusListener): void {
    this.globalStatusListeners.push(listener);
  }

  /** 移除全局状态监听 */
  removeStatusListener(listener: SseStatusListener): void {
    const idx: number = this.globalStatusListeners.indexOf(listener);
    if (idx >= 0) {
      this.globalStatusListeners.splice(idx, 1);
    }
  }

  /** 为指定账号建立 SSE 连接 */
  connectForAccount(accountId: string, server: string, token: string): void {
    let conn: SseConnection | undefined = this.connections.get(accountId);
    if (conn !== undefined && conn.connected) {
      hilog.info(DOMAIN, TAG, 'account %{public}s already connected', accountId);
      return;
    }

    if (conn === undefined) {
      conn = new SseConnection();
      conn.accountId = accountId;
      this.connections.set(accountId, conn);
    }

    conn.server = normalizeApiBase(server);
    conn.token = token;
    conn.connected = true;
    this.setConnStatus(conn, 'connecting');
    this.doConnect(conn);
  }

  /** 断开指定账号的 SSE 连接 */
  disconnectAccount(accountId: string): void {
    const conn: SseConnection | undefined = this.connections.get(accountId);
    if (conn === undefined) {
      return;
    }
    conn.connected = false;
    if (conn.reconnectTimer !== 0) {
      clearTimeout(conn.reconnectTimer);
      conn.reconnectTimer = 0;
    }
    if (conn.httpRequest !== null) {
      conn.httpRequest.destroy();
      conn.httpRequest = null;
    }
    this.setConnStatus(conn, 'disconnected');
    this.connections.delete(accountId);
  }

  /** 断开所有连接 */
  disconnectAll(): void {
    const keys: string[] = [];
    this.connections.forEach((_conn: SseConnection, key: string) => {
      keys.push(key);
    });
    for (let i = 0; i < keys.length; i++) {
      this.disconnectAccount(keys[i]);
    }
  }

  /** 根据 AccountManager 连接所有账号 */
  async connectAll(acctMgr: AccountManager): Promise<void> {
    await acctMgr.load();
    const accounts: AccountInfo[] = acctMgr.getAccounts();
    for (let i = 0; i < accounts.length; i++) {
      const acct: AccountInfo = accounts[i];
      this.connectForAccount(acct.id, acct.server, acct.token);
    }
  }

  /** 获取指定账号的连接状态 */
  getStatusForAccount(accountId: string): SseStatus {
    const conn: SseConnection | undefined = this.connections.get(accountId);
    if (conn === undefined) {
      return 'disconnected';
    }
    return conn.status;
  }

  /** 给指定账号添加事件监听 */
  addListenerForAccount(accountId: string, listener: SseListener): void {
    let conn: SseConnection | undefined = this.connections.get(accountId);
    if (conn === undefined) {
      conn = new SseConnection();
      conn.accountId = accountId;
      this.connections.set(accountId, conn);
    }
    conn.listeners.push(listener);
  }

  /** 移除指定账号的事件监听 */
  removeListenerForAccount(accountId: string, listener: SseListener): void {
    const conn: SseConnection | undefined = this.connections.get(accountId);
    if (conn !== undefined) {
      const idx: number = conn.listeners.indexOf(listener);
      if (idx >= 0) {
        conn.listeners.splice(idx, 1);
      }
    }
  }

  private setConnStatus(conn: SseConnection, status: SseStatus): void {
    if (conn.status !== status) {
      conn.status = status;
      hilog.info(DOMAIN, TAG, 'status[%{public}s]: %{public}s', conn.accountId, status);
      for (let i = 0; i < this.globalStatusListeners.length; i++) {
        this.globalStatusListeners[i](status);
      }
    }
  }

  private doConnect(conn: SseConnection): void {
    if (!conn.connected) {
      return;
    }

    const httpRequest = http.createHttp();
    conn.httpRequest = httpRequest;
    /* 重连要换新的：旧解码器里可能还卡着上次断线时那半个字 */
    conn.decoder = util.TextDecoder.create('utf-8', { ignoreBOM: true });

    const url: string = conn.server + '/events/stream';
    const header: Record<string, string> = {};
    if (conn.token.length > 0) {
      header['Authorization'] = 'Bearer ' + conn.token;
    }

    hilog.info(DOMAIN, TAG, 'connecting account %{public}s to %{public}s', conn.accountId, url);

    httpRequest.on('dataReceive', (data: ArrayBuffer) => {
      const text: string = this.arrayBufferToString(conn, data);
      conn.buffer += text;
      this.processBuffer(conn);
    });

    httpRequest.on('dataEnd', () => {
      hilog.info(DOMAIN, TAG, 'dataEnd for account %{public}s', conn.accountId);
      this.setConnStatus(conn, 'disconnected');
      this.scheduleReconnect(conn);
    });

    httpRequest.on('headersReceive', (_headers: Object) => {
      hilog.info(DOMAIN, TAG, 'headers received for account %{public}s', conn.accountId);
    });

    const options: http.HttpRequestOptions = {
      method: http.RequestMethod.GET,
      header: header,
      connectTimeout: 10000,
      readTimeout: 0
    };

    httpRequest.requestInStream(url, options, (err: BusinessError, code: number) => {
      if (err !== undefined && err !== null) {
        hilog.error(DOMAIN, TAG, 'requestInStream error account %{public}s: %{public}s', conn.accountId, err.message);
        this.setConnStatus(conn, 'disconnected');
        this.scheduleReconnect(conn);
        return;
      }
      hilog.info(DOMAIN, TAG, 'requestInStream code=%{public}d account=%{public}s', code, conn.accountId);
      if (code === 200) {
        this.setConnStatus(conn, 'connected');
      } else {
        hilog.error(DOMAIN, TAG, 'SSE failed code=%{public}d account=%{public}s', code, conn.accountId);
        this.setConnStatus(conn, 'disconnected');
        this.scheduleReconnect(conn);
      }
    });
  }

  private processBuffer(conn: SseConnection): void {
    const lines: string[] = conn.buffer.split('\n');
    conn.buffer = lines.pop() ?? '';

    let eventType: string = '';
    let eventData: string = '';

    for (let i = 0; i < lines.length; i++) {
      const line: string = lines[i];

      if (line.length === 0) {
        if (eventType.length > 0 || eventData.length > 0) {
          const event: SseEvent = new SseEvent();
          event.type = eventType.length > 0 ? eventType : 'message';
          event.data = eventData;
          event.accountId = conn.accountId;
          this.dispatchEvent(conn, event);
        }
        eventType = '';
        eventData = '';
      } else if (line.startsWith('event:')) {
        eventType = line.substring(6).trim();
      } else if (line.startsWith('data:')) {
        const newData: string = line.substring(5).trim();
        if (eventData.length > 0) {
          eventData += '\n' + newData;
        } else {
          eventData = newData;
        }
      }
    }
  }

  private dispatchEvent(conn: SseConnection, event: SseEvent): void {
    hilog.info(DOMAIN, TAG, 'event[%{public}s]: %{public}s data: %{public}s', conn.accountId, event.type,
      event.data.substring(0, 100));
    // 分发给账号级监听
    for (let i = 0; i < conn.listeners.length; i++) {
      conn.listeners[i](event);
    }
    // 分发给全局监听
    for (let i = 0; i < this.globalListeners.length; i++) {
      this.globalListeners[i](event);
    }
  }

  private scheduleReconnect(conn: SseConnection): void {
    if (!conn.connected) {
      return;
    }
    const timer: number | undefined = setTimeout(() => {
      conn.reconnectTimer = 0;
      this.doConnect(conn);
    }, 3000);
    conn.reconnectTimer = timer ?? 0;
  }

  private arrayBufferToString(conn: SseConnection, buffer: ArrayBuffer): string {
    /*
     * ★★ 2026-09-24 修：**UTF-8 解码**（用户：「鸿蒙 app 接收邮件的能力也有点不正常」）。
     *
     * 原来这里是逐字节 `String.fromCharCode(uint8Array[i])` —— 那是
     * **Latin-1 语义**：字节 ≥ 0x80 各自变成一个独立字符。
     * SSE 流里一个汉字是 3 个 UTF-8 字节（如 「新」 = E6 96 B0）
     * ⇒ 解出来是 `æ\x96°` 这种乱码。
     *
     * WebUI 没这个问题：它用浏览器原生 `EventSource`，规范本身按 UTF-8
     * 解码（`client/electron/src/api/sse.ts:59`）。
     * ⇒ 两端差在**解码这一步**，不是差在有没有 SSE。
     *
     * ★ 为什么不用 `util.TextDecoder`：HarmonyOS 有 `@kit.ArkTS` 的
     *   `util.TextDecoder`（标准 API），比自己手写 UTF-8 状态机可靠得多
     *   —— 手写容易在「3 字节序列被 TCP 分片切成两段」时错（SSE 常见）。
     *   `stream: true` 正是为这种分段场景准备的：不完整的尾字节会
     *   留在内部缓冲里，等下一片到了再拼。
     */
    const decoder: util.TextDecoder = conn.decoder !== null
      ? conn.decoder
      : util.TextDecoder.create('utf-8', { ignoreBOM: true });
    conn.decoder = decoder;
    return decoder.decodeToString(new Uint8Array(buffer), { stream: true });
  }
}