// Large-course mode API — learner-facing course manifest (L2, public read).
//
//   GET /api/learn/courses/:courseId
//
// Static data: the published course framework + per-module courseware ids.
// Zero LLM — the learner course page uses this to render the module list and
// link each module into the existing /learn/:coursewareId player.

import { type NextRequest } from 'next/server';
import { apiError, apiSuccess, API_ERROR_CODES } from '@/lib/server/api-response';
import { createLogger } from '@/lib/logger';
import { courseManifestRepo } from '@/lib/course-manifest-repo/store';
import { isValidCourseManifestId } from '@/lib/course-manifest-repo/store';
import { isPinnedCourseManifestModule } from '@/lib/course-manifest-repo/types';

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

export async function GET(
  request: NextRequest,
  { params }: { params: Promise<{ courseId: string }> },
) {
  try {
    const { courseId } = await params;
    if (!isValidCourseManifestId(courseId)) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 400, `Invalid course id: ${courseId}`);
    }
    const versionParam = new URL(request.url).searchParams.get('version');
    let record;
    if (versionParam !== null) {
      const version = Number(versionParam);
      if (!Number.isInteger(version) || version < 1) {
        return apiError(API_ERROR_CODES.INVALID_REQUEST, 400, 'Invalid course manifest version');
      }
      record = await courseManifestRepo.getRecord(courseId, version);
    } else {
      record = await courseManifestRepo.getLatestRecord(courseId);
    }
    if (!record) {
      return apiError(API_ERROR_CODES.INVALID_REQUEST, 404, `Course not found: ${courseId}`);
    }
    if (record.schemaVersion !== 2 || !record.modules.every(isPinnedCourseManifestModule)) {
      return apiError(
        API_ERROR_CODES.INVALID_REQUEST,
        409,
        'This legacy course manifest must be republished before learners can open it',
      );
    }
    return apiSuccess({
      course: {
        courseId: record.courseId,
        version: record.version,
        title: record.title,
        summary: record.summary,
        language: record.language,
        publishedAt: record.publishedAt,
        modules: record.modules.map((m) => ({
          index: m.index,
          title: m.title,
          description: m.description,
          coursewareId: m.coursewareId,
          coursewareVersion: m.coursewareVersion,
          contentHash: m.contentHash,
        })),
      },
    });
  } catch (error) {
    log.error('Learner course manifest failed:', error);
    return apiError(API_ERROR_CODES.INTERNAL_ERROR, 500, 'Failed to load course');
  }
}