import type { IncomingMessage, ServerResponse } from 'node:http';
import type { HostApiContext } from '../context';
import { parseJsonBody, sendJson } from '../route-utils';
import { WORKS_SQUARE_CONFIG } from '../works-config';
import { getValidWorksSquareAccessToken } from '../../services/works-square-session';
import { proxyAwareFetch } from '../../utils/proxy-fetch';

const LOCAL_ROOT = '/api/works/learning';
const UPSTREAM_ROOT = '/api/learning';

type Dependencies = {
  fetchImpl?: typeof fetch;
  getAccessToken?: typeof getValidWorksSquareAccessToken;
  apiBaseUrl?: string;
};

function isLearningPath(pathname: string): boolean {
  return pathname === `${LOCAL_ROOT}/courses`
    || pathname === `${LOCAL_ROOT}/courses/mine`
    || pathname === `${LOCAL_ROOT}/progress`
    || /^\/api\/works\/learning\/courses\/[^/]+$/.test(pathname)
    || /^\/api\/works\/learning\/courses\/[^/]+\/progress$/.test(pathname)
    || pathname === `${LOCAL_ROOT}/generations`
    || /^\/api\/works\/learning\/generations\/[^/]+$/.test(pathname)
    || /^\/api\/works\/learning\/generations\/[^/]+\/(?:cancel|resume|finalize)$/.test(pathname);
}

function upstreamPath(pathname: string): string {
  return `${UPSTREAM_ROOT}${pathname.slice(LOCAL_ROOT.length)}`;
}

function allowedQuery(url: URL): string {
  const query = new URLSearchParams();
  for (const key of ['limit', 'offset']) {
    const value = url.searchParams.get(key);
    if (value && /^\d{1,3}$/.test(value)) query.set(key, value);
  }
  const encoded = query.toString();
  return encoded ? `?${encoded}` : '';
}

function errorFields(payload: unknown, status: number): { code: string; error: string } {
  const record = payload && typeof payload === 'object' && !Array.isArray(payload)
    ? payload as Record<string, unknown>
    : {};
  const detail = record.detail && typeof record.detail === 'object' && !Array.isArray(record.detail)
    ? record.detail as Record<string, unknown>
    : {};
  return {
    code: typeof detail.code === 'string' ? detail.code : `LEARNING_HTTP_${status}`,
    error: typeof detail.message === 'string'
      ? detail.message
      : typeof record.detail === 'string'
        ? record.detail
        : typeof record.error === 'string'
          ? record.error
          : '学习服务暂时不可用',
  };
}

export function createLearningRouteHandler(dependencies: Dependencies = {}) {
  const fetchImpl = dependencies.fetchImpl ?? proxyAwareFetch;
  const getAccessToken = dependencies.getAccessToken ?? getValidWorksSquareAccessToken;
  const apiBaseUrl = (dependencies.apiBaseUrl ?? WORKS_SQUARE_CONFIG.apiBaseUrl).replace(/\/+$/, '');

  return async function handleLearningRoutes(
    req: IncomingMessage,
    res: ServerResponse,
    url: URL,
    _ctx: HostApiContext,
  ): Promise<boolean> {
    if (!isLearningPath(url.pathname)) return false;
    const isProgressWrite = req.method === 'PUT'
      && /^\/api\/works\/learning\/courses\/[^/]+\/progress$/.test(url.pathname);
    const isGenerationStart = req.method === 'POST' && url.pathname === `${LOCAL_ROOT}/generations`;
    const isGenerationFinalize = req.method === 'POST'
      && /^\/api\/works\/learning\/generations\/[^/]+\/finalize$/.test(url.pathname);
    const isGenerationControl = req.method === 'POST'
      && /^\/api\/works\/learning\/generations\/[^/]+\/(?:cancel|resume)$/.test(url.pathname);
    if (req.method !== 'GET' && !isProgressWrite && !isGenerationStart && !isGenerationFinalize && !isGenerationControl) {
      sendJson(res, 405, { success: false, code: 'LEARNING_METHOD_NOT_ALLOWED', error: '不支持的学习请求' });
      return true;
    }

    try {
      const token = await getAccessToken({ fetchImpl });
      if (!token) {
        sendJson(res, 401, { success: false, code: 'LEARNING_AUTH_REQUIRED', error: '请先登录' });
        return true;
      }
      const body = isProgressWrite || isGenerationStart
        ? await parseJsonBody<unknown>(req)
        : undefined;
      const request = (accessToken: string) => fetchImpl(
        `${apiBaseUrl}${upstreamPath(url.pathname)}${allowedQuery(url)}`,
        {
          method: req.method,
          headers: {
            Accept: 'application/json',
            Authorization: `Bearer ${accessToken}`,
            ...(body === undefined ? {} : { 'Content-Type': 'application/json' }),
          },
          ...(body === undefined ? {} : { body: JSON.stringify(body) }),
          redirect: 'manual',
        },
      );

      let response = await request(token);
      if (response.status === 401) {
        await response.body?.cancel().catch(() => undefined);
        const refreshed = await getAccessToken({ fetchImpl, forceRefresh: true });
        if (refreshed) response = await request(refreshed);
      }
      const payload = await response.json().catch(() => null);
      if (!response.ok || payload === null) {
        const fields = errorFields(payload, response.status || 502);
        sendJson(res, response.status || 502, { success: false, status: response.status, ...fields });
        return true;
      }
      sendJson(res, response.status, { success: true, data: payload });
      return true;
    } catch (error) {
      sendJson(res, 502, {
        success: false,
        status: 502,
        code: 'LEARNING_UNAVAILABLE',
        error: error instanceof Error ? error.message : '学习服务暂时不可用',
      });
      return true;
    }
  };
}

export const handleLearningRoutes = createLearningRouteHandler();