import { Readable } from 'node:stream';

import { type Request, type Response, Router } from 'express';

import type { AppContext } from '../context.js';
import { badRequest, upstreamError } from '../errors.js';
import {
  API_RESPONSE_ENVELOPE_HEADER,
  API_VERSION_HEADER,
  asyncHandler,
  prepareApiResponse,
  RESPONSE_TIME_HEADER,
  ROUTE_VERSION_HEADER,
} from '../http.js';
import { requireJwtAuth } from '../middleware/auth.js';
import { routeMeta } from '../middleware/routeMeta.js';

const PUZZLE_ROUTE_VERSION = '2026-04-22';
const DEFAULT_RUST_API_TARGET = 'http://127.0.0.1:3100';
const DEFAULT_INTERNAL_API_SECRET = 'genarrative-dev-internal-bridge';
const INTERNAL_USER_HEADER = 'x-genarrative-authenticated-user-id';
const INTERNAL_SECRET_HEADER = 'x-genarrative-internal-api-secret';

function resolveRustApiTarget(context: AppContext) {
  const configured =
    context.config.rawEnv.GENARRATIVE_API_TARGET?.trim() ||
    context.config.rawEnv.RUST_API_SERVER_TARGET?.trim() ||
    '';
  return configured || DEFAULT_RUST_API_TARGET;
}

function resolveInternalApiSecret(context: AppContext) {
  return (
    context.config.rawEnv.GENARRATIVE_INTERNAL_API_SECRET?.trim() ||
    DEFAULT_INTERNAL_API_SECRET
  );
}

function normalizeRouteSuffix(path: string) {
  const normalized = path.startsWith('/') ? path : `/${path}`;
  return normalized.replace(/\/+$/u, '');
}

function buildUpstreamUrl(context: AppContext, pathSuffix: string) {
  const baseUrl = resolveRustApiTarget(context).replace(/\/+$/u, '');
  return `${baseUrl}${normalizeRouteSuffix(pathSuffix)}`;
}

function pickForwardHeaders(
  request: Request,
  context: AppContext,
  userId: string,
) {
  const forwardedHeaders = new Headers();

  const contentType = request.header('content-type')?.trim();
  if (contentType) {
    forwardedHeaders.set('content-type', contentType);
  }

  const accept = request.header('accept')?.trim();
  if (accept) {
    forwardedHeaders.set('accept', accept);
  }

  const requestId = request.requestId?.trim();
  if (requestId) {
    forwardedHeaders.set('x-request-id', requestId);
  }

  const envelope = request.header(API_RESPONSE_ENVELOPE_HEADER)?.trim();
  if (envelope) {
    forwardedHeaders.set(API_RESPONSE_ENVELOPE_HEADER, envelope);
  }

  forwardedHeaders.set(INTERNAL_USER_HEADER, userId);
  const internalSecret = resolveInternalApiSecret(context);
  if (internalSecret) {
    forwardedHeaders.set(INTERNAL_SECRET_HEADER, internalSecret);
  }
  return forwardedHeaders;
}

function readBodyAllowed(method: string) {
  return !['GET', 'HEAD'].includes(method.toUpperCase());
}

async function proxyPuzzleRequest(params: {
  context: AppContext;
  request: Request;
  response: Response;
  pathSuffix: string;
  streamBody?: boolean;
}) {
  const { context, request, response, pathSuffix, streamBody = false } = params;
  const userId = request.userId?.trim();
  if (!userId) {
    throw badRequest('缺少已认证用户上下文');
  }

  const upstreamUrl = buildUpstreamUrl(context, pathSuffix);
  const method = request.method.toUpperCase();
  const body =
    readBodyAllowed(method) && request.body !== undefined
      ? JSON.stringify(request.body)
      : undefined;

  let upstreamResponse: globalThis.Response;
  try {
    upstreamResponse = await fetch(upstreamUrl, {
      method,
      headers: pickForwardHeaders(request, context, userId),
      body,
    });
  } catch (error) {
    request.log?.error(
      {
        err: error,
        user_id: userId,
        upstream_url: upstreamUrl,
      },
      'puzzle upstream request failed',
    );
    throw upstreamError('拼图后端暂时不可用');
  }

  prepareApiResponse(request, response, {
    statusCode: upstreamResponse.status,
    headers: {
      'Content-Type':
        upstreamResponse.headers.get('content-type') ||
        'application/json; charset=utf-8',
      'Cache-Control':
        upstreamResponse.headers.get('cache-control') || 'no-cache',
    },
    routeMeta: {
      routeVersion: PUZZLE_ROUTE_VERSION,
    },
  });

  const upstreamRequestId = upstreamResponse.headers.get('x-request-id');
  if (upstreamRequestId) {
    response.setHeader('x-upstream-request-id', upstreamRequestId);
  }

  const upstreamRouteVersion = upstreamResponse.headers.get(ROUTE_VERSION_HEADER);
  if (upstreamRouteVersion) {
    response.setHeader('x-upstream-route-version', upstreamRouteVersion);
  }

  const upstreamApiVersion = upstreamResponse.headers.get(API_VERSION_HEADER);
  if (upstreamApiVersion) {
    response.setHeader('x-upstream-api-version', upstreamApiVersion);
  }

  const upstreamLatency = upstreamResponse.headers.get(RESPONSE_TIME_HEADER);
  if (upstreamLatency) {
    response.setHeader('x-upstream-response-time-ms', upstreamLatency);
  }

  if (streamBody) {
    if (!upstreamResponse.body) {
      throw upstreamError('拼图流式响应不可用');
    }

    response.flushHeaders?.();
    await Readable.fromWeb(upstreamResponse.body as never).pipe(response);
    return;
  }

  response.end(await upstreamResponse.text());
}

function readParam(value: string | string[] | undefined) {
  return Array.isArray(value) ? value[0]?.trim() || '' : value?.trim() || '';
}

export function createPuzzleProxyRoutes(context: AppContext) {
  const router = Router();
  const requireAuth = requireJwtAuth(context.config, context.userRepository);

  router.use(requireAuth);

  router.post(
    '/agent/sessions',
    routeMeta({ operation: 'runtime.puzzle.createSession', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: '/api/runtime/puzzle/agent/sessions',
      });
    }),
  );

  router.get(
    '/agent/sessions/:sessionId',
    routeMeta({ operation: 'runtime.puzzle.getSession', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const sessionId = readParam(request.params.sessionId);
      if (!sessionId) {
        throw badRequest('sessionId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/agent/sessions/${encodeURIComponent(sessionId)}`,
      });
    }),
  );

  router.post(
    '/agent/sessions/:sessionId/messages',
    routeMeta({ operation: 'runtime.puzzle.sendMessage', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const sessionId = readParam(request.params.sessionId);
      if (!sessionId) {
        throw badRequest('sessionId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/agent/sessions/${encodeURIComponent(sessionId)}/messages`,
      });
    }),
  );

  router.post(
    '/agent/sessions/:sessionId/messages/stream',
    routeMeta({
      operation: 'runtime.puzzle.streamMessage',
      routeVersion: PUZZLE_ROUTE_VERSION,
    }),
    asyncHandler(async (request, response) => {
      const sessionId = readParam(request.params.sessionId);
      if (!sessionId) {
        throw badRequest('sessionId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/agent/sessions/${encodeURIComponent(sessionId)}/messages/stream`,
        streamBody: true,
      });
    }),
  );

  router.post(
    '/agent/sessions/:sessionId/actions',
    routeMeta({ operation: 'runtime.puzzle.executeAction', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const sessionId = readParam(request.params.sessionId);
      if (!sessionId) {
        throw badRequest('sessionId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/agent/sessions/${encodeURIComponent(sessionId)}/actions`,
      });
    }),
  );

  router.get(
    '/works',
    routeMeta({ operation: 'runtime.puzzle.listWorks', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: '/api/runtime/puzzle/works',
      });
    }),
  );

  router.get(
    '/works/:profileId',
    routeMeta({ operation: 'runtime.puzzle.getWorkDetail', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const profileId = readParam(request.params.profileId);
      if (!profileId) {
        throw badRequest('profileId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/works/${encodeURIComponent(profileId)}`,
      });
    }),
  );

  router.put(
    '/works/:profileId',
    routeMeta({ operation: 'runtime.puzzle.updateWork', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const profileId = readParam(request.params.profileId);
      if (!profileId) {
        throw badRequest('profileId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/works/${encodeURIComponent(profileId)}`,
      });
    }),
  );

  router.get(
    '/gallery',
    routeMeta({ operation: 'runtime.puzzle.listGallery', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: '/api/runtime/puzzle/gallery',
      });
    }),
  );

  router.get(
    '/gallery/:profileId',
    routeMeta({ operation: 'runtime.puzzle.getGalleryDetail', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const profileId = readParam(request.params.profileId);
      if (!profileId) {
        throw badRequest('profileId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/gallery/${encodeURIComponent(profileId)}`,
      });
    }),
  );

  router.post(
    '/runs',
    routeMeta({ operation: 'runtime.puzzle.startRun', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: '/api/runtime/puzzle/runs',
      });
    }),
  );

  router.get(
    '/runs/:runId',
    routeMeta({ operation: 'runtime.puzzle.getRun', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const runId = readParam(request.params.runId);
      if (!runId) {
        throw badRequest('runId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/runs/${encodeURIComponent(runId)}`,
      });
    }),
  );

  router.post(
    '/runs/:runId/swap',
    routeMeta({ operation: 'runtime.puzzle.swapPieces', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const runId = readParam(request.params.runId);
      if (!runId) {
        throw badRequest('runId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/runs/${encodeURIComponent(runId)}/swap`,
      });
    }),
  );

  router.post(
    '/runs/:runId/drag',
    routeMeta({ operation: 'runtime.puzzle.dragPiece', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const runId = readParam(request.params.runId);
      if (!runId) {
        throw badRequest('runId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/runs/${encodeURIComponent(runId)}/drag`,
      });
    }),
  );

  router.post(
    '/runs/:runId/next-level',
    routeMeta({ operation: 'runtime.puzzle.nextLevel', routeVersion: PUZZLE_ROUTE_VERSION }),
    asyncHandler(async (request, response) => {
      const runId = readParam(request.params.runId);
      if (!runId) {
        throw badRequest('runId is required');
      }

      await proxyPuzzleRequest({
        context,
        request,
        response,
        pathSuffix: `/api/runtime/puzzle/runs/${encodeURIComponent(runId)}/next-level`,
      });
    }),
  );

  return router;
}