// Large-course mode API — confirm the framework and start module generation.
//
//   POST /api/courses/:courseId/start
//
// The two-layer flow is deliberately gated: creating a course only generates
// the framework (status `framework_ready`). This endpoint is the operator's
// explicit confirmation after reviewing the framework — only then does the
// Layer-2 single-courseware agent start generating each module one by one.

import { after, type NextRequest } from 'next/server';
import { apiError, apiSuccess, API_ERROR_CODES } from '@/lib/server/api-response';
import { buildRequestOrigin } from '@/lib/server/classroom-storage';
import { createLogger } from '@/lib/logger';
import { isValidCourseId, readCourseRecordReconciled } from '@/lib/course-framework/store';
import {
  isCourseGenerationRunning,
  runCourseModuleGeneration,
} from '@/lib/course-framework/runner';
import { requireOpsAccess } from '@/lib/server/ops-access';
import {
  CourseMutationInProgressError,
  isCoursePublishing,
} from '@/lib/course-framework/publish-state';
import { proxyLargeCourseControlToEngine } from '@/lib/makelore-runtime/ops-engine-control';
import {
  assertLearningCourseMutable,
  FrozenLearningCourseMutationError,
} from '@/lib/makelore-course/immutability';

const log = createLogger('Course Start API');

export async function POST(
  req: NextRequest,
  { params }: { params: Promise<{ courseId: string }> },
) {
  const denied = await requireOpsAccess(req);
  if (denied) return denied;

  try {
    const { courseId } = await params;
    if (!isValidCourseId(courseId)) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 400, `Invalid course id: ${courseId}`);
    }
    const record = await readCourseRecordReconciled(courseId);
    if (!record) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 404, `Course not found: ${courseId}`);
    }
    const proxied = await proxyLargeCourseControlToEngine({
      request: req,
      course: record,
      action: 'start',
    });
    if (proxied) return proxied;
    await assertLearningCourseMutable(courseId, record);
    if (!record.framework) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 409, '课程框架尚未生成，请等待框架生成完成');
    }
    if (record.status !== 'framework_ready') {
      return apiError(
        API_ERROR_CODES.INVALID_REQUEST,
        409,
        `当前状态（${record.status}）不允许启动模块生成`,
      );
    }
    if (
      isCourseGenerationRunning(courseId) ||
      isCoursePublishing(courseId) ||
      record.modules.some((m) => m.status === 'generating')
    ) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 409, '该课程已有生成任务正在运行');
    }

    const baseUrl = buildRequestOrigin(req);
    const run = runCourseModuleGeneration(courseId, baseUrl);
    after(() => run);

    log.info(`Course ${courseId}: framework confirmed by operator — starting module generation`);
    return apiSuccess({
      courseId,
      status: 'generating',
      message: '模块生成已开始',
      detailUrl: `${baseUrl}/api/courses/${courseId}`,
    });
  } catch (error) {
    if (error instanceof FrozenLearningCourseMutationError) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 409, error.message);
    }
    if (error instanceof CourseMutationInProgressError) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 409, error.message);
    }
    log.error('Course start failed:', error);
    return apiError(API_ERROR_CODES.INTERNAL_ERROR, 500, 'Failed to start module generation');
  }
}