/**
 * 平台服务入口（架构设计第 2 节）。
 *
 * 组装：应用服务 + HTTP / SSE 入口。控制面（core）与引擎适配（agent）在后续阶段接入。
 */
import { randomUUID } from 'node:crypto';
import type { Server } from 'node:http';
import type { AddressInfo } from 'node:net';

import type { AgentRuntime } from './agent/runtime.js';
import { loadConfig } from './config.js';
import { openDatabase, type Database } from './core/storage/db.js';
import { SessionRepository } from './core/storage/sessions.js';
import { ApplicationService } from './app/service.js';
import { createHttpServer } from './entry/http.js';

export { ApplicationService } from './app/service.js';
export type { Subject } from './app/subject.js';
export { createHttpServer } from './entry/http.js';

export interface StartOptions {
  host?: string;
  port?: number;
  version?: string;
  /** 引擎实现：默认假引擎；A3.3 起可换成 Pi 子进程，测试也可注入脚本化假引擎 */
  runtime?: AgentRuntime;
  /** 数据库路径：默认取配置；测试传 ':memory:' 以隔离 */
  databasePath?: string;
}

export interface RunningServer {
  url: string;
  port: number;
  service: ApplicationService;
  /** 引擎工具回调的内部令牌：由平台生成，启动引擎子进程时注入（A3.11） */
  internalToken: string;
  close(): Promise<void>;
}

export async function startServer(options: StartOptions = {}): Promise<RunningServer> {
  const config = loadConfig();
  const host = options.host ?? config.server.host;
  const port = options.port ?? config.server.port;
  const runtime = options.runtime ?? (await selectRuntime(config));
  const database: Database = openDatabase(options.databasePath ?? config.database.path);
  const service = new ApplicationService({
    ...(options.version === undefined ? {} : { version: options.version }),
    runtime,
    sessionRepository: new SessionRepository(database),
  });
  // 开发期可选：APS_DEV_PROVIDER=1 时注册假 Provider，用于本地联调与演示（默认不注册，能力清单为空）
  if (process.env.APS_DEV_PROVIDER === '1') {
    const { createFakeProvider } = await import('@aps/provider-sdk/testing');
    await service.registerProvider(createFakeProvider());
  }

  const internalToken = randomUUID();
  const server: Server = createHttpServer(service, internalToken);

  await new Promise<void>((resolve, reject) => {
    server.once('error', reject);
    server.listen(port, host, () => resolve());
  });

  const address = server.address() as AddressInfo | null;
  const actualPort = address ? address.port : port;

  return {
    url: `http://${host}:${actualPort}`,
    port: actualPort,
    service,
    internalToken,
    close: () =>
      new Promise<void>((resolve, reject) => {
        server.close((error) => (error ? reject(error) : resolve()));
        // 事件流是长连接，关停时必须主动断开，否则 close 会一直等它们
        // 客户端断线后按 Last-Event-ID 重连，不会丢事件（协议文档第 5 节）
        server.closeAllConnections();
        database.close();
      }),
  };
}
/** 引擎选择：显式注入 > 配置里的 engine.kind；选 pi 但没密钥时明确回退到假引擎 */
async function selectRuntime(config: ReturnType<typeof loadConfig>): Promise<AgentRuntime> {
  if (config.engine.kind !== 'pi') {
    const { createFakeRuntime } = await import('./agent/fake-runtime.js');
    const { createRulePlanner, plannerToFakeTurn } = await import('./agent/rule-planner.js');
    return createFakeRuntime({ name: 'fake', planner: plannerToFakeTurn(createRulePlanner()) });
  }
  if (config.llm.apiKey.trim() === '') {
    console.error('警告：配置要求 Pi 引擎但没有模型密钥，已回退到假引擎（ADR-0011 允许未配置时降级）');
    const { createFakeRuntime } = await import('./agent/fake-runtime.js');
    const { createRulePlanner, plannerToFakeTurn } = await import('./agent/rule-planner.js');
    return createFakeRuntime({ name: 'fake', planner: plannerToFakeTurn(createRulePlanner()) });
  }
  const { createPiRuntime } = await import('./agent/pi/runtime.js');
  return createPiRuntime({ provider: config.llm.provider, model: config.llm.model, apiKey: config.llm.apiKey });
}