import type { IncomingMessage, ServerResponse } from 'node:http';
import type { HostApiContext } from '../context';
import {
  flushStreamingHeaders,
  parseJsonBody,
  sendJson,
  writeStreamingChunk,
} from '../route-utils';
import { TeacherError } from '../../coding-teacher/config-client';
import type { TeacherScope } from '../../coding-teacher/service';
import type { TeacherSend } from '../../../shared/coding-teacher';
import { takeTeacherPreviewRevision } from '../../main/app-deep-link';

export async function handleCodingTeacherRoutes(
  req: IncomingMessage,
  res: ServerResponse,
  url: URL,
  ctx: HostApiContext
): Promise<boolean> {
  const source = url.pathname.match(
    /^\/api\/coding\/projects\/([^/]+)\/conversations\/([^/]+)\/teacher-topics(?:\/([^/]+))?(?:\/(messages|events|save|requests\/([^/]+)\/cancel))?$/
  );
  const preview = url.pathname.match(
    /^\/api\/coding\/teacher-preview\/topics(?:\/([^/]+))?(?:\/(messages|events|save|requests\/([^/]+)\/cancel))?$/
  );
  const config = url.pathname === '/api/coding/teacher/config';
  const draft = url.pathname === '/api/coding/teacher-preview';
  const pending = url.pathname === '/api/coding/teacher-preview/pending-link';
  if (!source && !preview && !config && !draft && !pending) return false;
  if ((config || draft || pending) && req.method !== 'GET') {
    sendJson(res, 405, { error: '不支持此操作。' });
    return true;
  }
  if (pending && req.method === 'GET') {
    sendJson(res, 200, { draftRevision: takeTeacherPreviewRevision() });
    return true;
  }
  const service = ctx.codingProducts?.teacher;
  if (!service) {
    sendJson(res, 503, { error: '老师服务暂不可用。', code: 'teacher_unavailable' });
    return true;
  }
  try {
    if (config && req.method === 'GET') {
      sendJson(res, 200, await service.definition());
      return true;
    }
    if (draft && req.method === 'GET') {
      const revision = Number(url.searchParams.get('draftRevision'));
      if (!Number.isSafeInteger(revision) || revision < 1)
        throw new TeacherError(400, 'teacher_preview_invalid', '草稿版本无效。');
      sendJson(res, 200, await service.previewDefinition(revision));
      return true;
    }
    const scope: TeacherScope = source
      ? { projectId: decodeURIComponent(source[1]), sourceId: decodeURIComponent(source[2]) }
      : { projectId: 'preview', sourceId: 'preview' };
    const id = source?.[3] ?? preview?.[1],
      action = source?.[4] ?? preview?.[2],
      requestId = source?.[5] ?? preview?.[3];
    if (!id && req.method === 'GET') {
      sendJson(res, 200, await service.list(scope));
      return true;
    }
    if (!id && req.method === 'POST') {
      const body = await parseJsonBody<{ draftRevision?: number; sampleContext?: string }>(req);
      sendJson(res, 201, await service.create(scope, body.draftRevision, body.sampleContext));
      return true;
    }
    if (id && !action && req.method === 'GET') {
      sendJson(res, 200, await service.read(scope, id));
      return true;
    }
    if (id && action === 'messages' && req.method === 'POST') {
      sendJson(res, 202, await service.send(scope, id, await parseJsonBody<TeacherSend>(req)));
      return true;
    }
    if (id && action === 'save' && req.method === 'POST') {
      sendJson(res, 200, await service.save(scope, id));
      return true;
    }
    if (id && requestId && req.method === 'POST') {
      sendJson(res, 200, await service.cancel(scope, id, requestId));
      return true;
    }
    if (id && action === 'events' && req.method === 'GET') {
      let closed = false;
      const buffered: unknown[] = [];
      let started = false;
      const close = await service.subscribe(scope, id, (topic) => {
        if (!started) {
          buffered.push(topic);
          return;
        }
        if (!closed)
          void writeStreamingChunk(
            res,
            'event: snapshot\ndata: ' + JSON.stringify(topic) + '\n\n'
          ).catch(() => {
            closed = true;
          });
      });
      let timer: ReturnType<typeof setInterval> | undefined;
      const cleanup = () => {
        closed = true;
        if (timer) clearInterval(timer);
        close();
      };
      req.once('close', cleanup);
      res.once('close', cleanup);
      try {
        res.statusCode = 200;
        res.setHeader('Content-Type', 'text/event-stream; charset=utf-8');
        res.setHeader('Cache-Control', 'private, no-store');
        res.setHeader('Connection', 'keep-alive');
        flushStreamingHeaders(res);
        started = true;
        for (const topic of buffered) {
          if (!await writeStreamingChunk(res, 'event: snapshot\ndata: ' + JSON.stringify(topic) + '\n\n')) {
            cleanup(); return true;
          }
        }
        timer = setInterval(() => {
          if (!closed) void writeStreamingChunk(res, ': keepalive\n\n').then(written => {
            if (!written) cleanup();
          }).catch(cleanup);
        }, 15000);
      } catch {
        cleanup();
        res.end();
      }
      return true;
    }
    sendJson(res, 405, { error: '不支持此操作。' });
  } catch (error) {
    if (error instanceof TeacherError)
      sendJson(res, error.status, { error: error.message, code: error.code });
    else
      sendJson(res, 500, {
        error: '老师操作失败，请保留当前内容后重试。',
        code: 'teacher_operation_failed',
      });
  }
  return true;
}