#后端不符合约定时

import {
  createOpenAiAdapter,
  type OpenAiHistory,
  type OpenAiHistoryMessage,
} from '@volcengine/chatkit/adapters/openai';

/** 后端现有的历史接口返回的格式：字段名和约定的不一样。 */
interface LegacyHistory {
  items: { msgId: string; turn: string; role: 'user' | 'assistant'; text: string; ts: number }[];
  next?: string;
}

const toMessage = (item: LegacyHistory['items'][number]): OpenAiHistoryMessage => ({
  id: item.msgId,
  run_id: item.turn,
  created_at: item.ts,
  role: item.role,
  content: item.text,
});

export const adapter = createOpenAiAdapter({
  run: ({ sessionId, runId, body }) =>
    fetch(`/api/chat/sessions/${sessionId}/runs`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ run_id: runId, ...body }),
    }),
  history: async ({ sessionId, cursor }) => {
    const query = cursor ? `?next=${encodeURIComponent(cursor)}` : '';
    const response = await fetch(`/api/legacy/${sessionId}/messages${query}`, {});
    // 失败的响应原样返回，适配器按状态码处理
    if (!response.ok) return response;
    const legacy = (await response.json()) as LegacyHistory;
    const history: OpenAiHistory = {
      messages: legacy.items.map(toMessage),
      ...(legacy.next ? { cursor: legacy.next, has_more: true } : {}),
    };
    // 转成约定的格式，再包成响应返回
    return new Response(JSON.stringify(history), { headers: { 'Content-Type': 'application/json' } });
  },
});

import { createOpenAiAdapter } from '@volcengine/chatkit/adapters/openai';

/** 后端不管成功失败都返回 200，结果包在一层里：code 不是 0 表示失败。 */
interface Wrapped {
  code: number;
  msg: string;
  data: unknown;
}

const unwrap = async (response: Response): Promise<Response> => {
  if (!response.ok) return response;
  const wrapped = (await response.json()) as Wrapped;
  // 失败：换成非成功状态，错误文字放在约定的位置
  if (wrapped.code !== 0) {
    const error = { code: String(wrapped.code), message: wrapped.msg };
    return new Response(JSON.stringify({ error }), { status: 502 });
  }
  // 成功：去掉外面包的那一层
  return new Response(JSON.stringify(wrapped.data));
};

export const adapter = createOpenAiAdapter({
  run: ({ body }) =>
    fetch('/api/chat/completions', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(body),
    }),
});

/**
 * 服务层的代码（运行在自己的服务端，不在浏览器里）：上游的流没有事件编号，转发时给每个事件加上 `id:`。
 * 加上之后还要把事件按轮次存下来，续接请求到来时从指定的编号之后接着发。
 */
export const withEventIds = (upstream: Response, onEvent: (eventId: string, frame: string) => void): Response => {
  if (!upstream.body) return upstream;
  let buffer = '';
  let sequence = 0;
  const encoder = new TextEncoder();
  const numbered = new TransformStream<string, Uint8Array>({
    transform(chunk, controller) {
      buffer += chunk;
      // SSE 的事件之间用空行隔开
      const frames = buffer.split('\n\n');
      buffer = frames.pop() ?? '';
      for (const frame of frames) {
        const eventId = `e${++sequence}`;
        onEvent(eventId, frame);
        controller.enqueue(encoder.encode(`id: ${eventId}\n${frame}\n\n`));
      }
    },
  });
  return new Response(upstream.body.pipeThrough(new TextDecoderStream()).pipeThrough(numbered), {
    status: upstream.status,
    headers: { 'Content-Type': 'text/event-stream', 'Cache-Control': 'no-cache' },
  });
};

import { createHermesAdapter } from '@volcengine/chatkit/adapters/hermes';

const send = (method: string, path: string, body?: unknown) =>
  fetch(`/api/hermes${path}`, {
    method,
    headers: { 'Content-Type': 'application/json' },
    ...(body === undefined ? {} : { body: JSON.stringify(body) }),
  });
const session = (sessionId: string) => `/api/sessions/${encodeURIComponent(sessionId)}`;

// 后端不能按事件编号续接，也不能作废旧的一轮：resume、regenerate、edit 都不给。
// 界面上没有重新生成和编辑；连接中途断开时这一轮显示为失败，可以重试
export const adapter = createHermesAdapter({
  run: ({ sessionId, body }) => send('POST', `${session(sessionId)}/chat/stream`, body),
  history: ({ sessionId }) => send('GET', `${session(sessionId)}/messages`),
});