import { WORKS_SQUARE_CONFIG } from '../api/works-config';
import { proxyAwareFetch } from '../utils/proxy-fetch';
import { getValidWorksSquareAccessToken } from './works-square-session';
import type {
  LearningRuntimeBridgeEvent,
  LearningRuntimeBridgeRequest,
  LearningRuntimeCapability,
} from '../../shared/learning';

const COURSE_ID_PATTERN = /^[A-Za-z0-9_-]{1,64}$/;
const MODULE_ID_PATTERN = /^(?!\.{1,2}$)[A-Za-z0-9._-]{1,128}$/;
const SHA256_PATTERN = /^[0-9a-f]{64}$/;
const REQUEST_ID_PATTERN = /^[A-Za-z0-9_.:-]{1,128}$/;
const MAX_REQUEST_BYTES = 2 * 1024 * 1024;
const MAX_RESPONSE_BYTES = 64 * 1024 * 1024;
const CAPABILITIES = new Set<LearningRuntimeCapability>([
  'quiz-grade',
  'pbl/v2/task/update',
  'pbl/v2/open-task',
  'pbl/v2/simulator',
  'pbl/v2/instructor',
  'pbl/v2/evaluate',
]);

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

function capabilityPath(capability: LearningRuntimeCapability): string {
  return capability.split('/').map(encodeURIComponent).join('/');
}

function sanitizeAnchor(value: unknown): { sceneId?: string; sceneOrder?: number } | undefined {
  if (!value || typeof value !== 'object' || Array.isArray(value)) return undefined;
  const candidate = value as Record<string, unknown>;
  const anchor = {
    ...(typeof candidate.sceneId === 'string' && candidate.sceneId.length > 0 && candidate.sceneId.length <= 256
      ? { sceneId: candidate.sceneId }
      : {}),
    ...(Number.isSafeInteger(candidate.sceneOrder) && Number(candidate.sceneOrder) >= 0
      ? { sceneOrder: Number(candidate.sceneOrder) }
      : {}),
  };
  return Object.keys(anchor).length > 0 ? anchor : undefined;
}

function validateRequest(request: LearningRuntimeBridgeRequest): string {
  const anchor = sanitizeAnchor(request.context.anchor);
  if (!REQUEST_ID_PATTERN.test(request.requestId)
    || !COURSE_ID_PATTERN.test(request.courseId)
    || !SHA256_PATTERN.test(request.contentHash)
    || (request.context.moduleId !== null && !MODULE_ID_PATTERN.test(request.context.moduleId))
    || !SHA256_PATTERN.test(request.context.moduleContentHash)
    || !anchor?.sceneId
    || request.method !== 'POST'
    || !CAPABILITIES.has(request.capability)) {
    throw new Error('课堂联网能力请求无效');
  }
  const body = JSON.stringify({
    context: {
      moduleId: request.context.moduleId,
      moduleContentHash: request.context.moduleContentHash,
      anchor: { sceneId: anchor.sceneId, ...(anchor.sceneOrder !== undefined ? { sceneOrder: anchor.sceneOrder } : {}) },
    },
    body: request.body ?? {},
  });
  if (Buffer.byteLength(body) > MAX_REQUEST_BYTES) throw new Error('课堂联网请求过大');
  return body;
}

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

  async function request(
    input: LearningRuntimeBridgeRequest,
    emit: (event: LearningRuntimeBridgeEvent) => void,
  ): Promise<void> {
    try {
      const body = validateRequest(input);
      const token = await getAccessToken({ fetchImpl });
      if (!token) {
        emit({ requestId: input.requestId, type: 'error', code: 'LEARNING_AUTH_REQUIRED', message: '请先登录后使用联网课堂能力' });
        return;
      }
      const fetchRequest = (accessToken: string) => fetchImpl(
        `${apiBaseUrl}/api/learning/courses/${encodeURIComponent(input.courseId)}/runtime/${capabilityPath(input.capability)}`,
        {
          method: 'POST',
          headers: {
            Accept: '*/*',
            Authorization: `Bearer ${accessToken}`,
            'Content-Type': 'application/json',
            'X-Course-Content-Hash': input.contentHash,
            'X-Content-Hash': input.contentHash,
          },
          body,
          redirect: 'manual',
        },
      );
      let response = await fetchRequest(token);
      if (response.status === 401) {
        await response.body?.cancel().catch(() => undefined);
        const refreshed = await getAccessToken({ fetchImpl, forceRefresh: true });
        if (refreshed) response = await fetchRequest(refreshed);
      }
      emit({
        requestId: input.requestId,
        type: 'start',
        status: response.status,
        contentType: response.headers.get('content-type') || 'application/octet-stream',
      });
      if (response.body) {
        const reader = response.body.getReader();
        let bytesRead = 0;
        try {
          while (true) {
            const chunk = await reader.read();
            if (chunk.done) break;
            bytesRead += chunk.value.byteLength;
            if (bytesRead > MAX_RESPONSE_BYTES) throw new Error('课堂联网响应过大');
            emit({ requestId: input.requestId, type: 'chunk', chunk: new Uint8Array(chunk.value) });
          }
        } finally {
          reader.releaseLock();
        }
      }
      emit({ requestId: input.requestId, type: 'end' });
    } catch (error) {
      emit({
        requestId: input.requestId,
        type: 'error',
        code: 'LEARNING_RUNTIME_UNAVAILABLE',
        message: error instanceof Error ? error.message : '课堂联网能力暂时不可用',
      });
    }
  }

  return { request };
}