// Legacy classroom migration — re-package existing server-side classrooms
// (`data/classrooms/*.json`, stage + scenes) into published frozen bundles.
//
// The packager is byte-agnostic: media/narration bytes arrive through injected
// resolvers. Deployments with server persistence resolve them from the asset
// registry; otherwise (bytes only in learner browsers) the migration reports
// the classroom as "re-publish from the ops workbench" instead of publishing a
// broken bundle. The publish gate (`requireComplete`) is always on here.

import { packageCourseware, type PackageResult } from '@/lib/bundle/packager';
import { publishCourseware } from '@/lib/courseware-repo';
import { COURSEWARES_DIR, createFileCoursewareRepo } from '@/lib/courseware-repo/store';
import {
  COURSEWARE_BUNDLES_DIR,
  createFileBundleByteStore,
} from '@/lib/courseware-repo/bundle-store';
import { CLASSROOMS_DIR, type PersistedClassroomData } from '@/lib/server/classroom-storage';
import { promises as fs } from 'fs';
import path from 'path';
import { createLogger } from '@/lib/logger';
import type { CoursewareRepo } from '@/lib/courseware-repo/types';
import type { BundleByteStore } from '@/lib/courseware-repo/bundle-store';
import type { MediaFileRecord } from '@/lib/utils/database';

const log = createLogger('MigrateCoursewares');

export interface ClassroomByteResolvers {
  /** Resolve narration bytes by audioId (server asset registry, …). */
  resolveAudioBytes?: (audioId: string) => Promise<Blob | null>;
  /** Resolve media bytes by record shape (elementId + mimeType). */
  resolveMediaBytes?: (record: MediaFileRecord) => Promise<Blob | null>;
}

export interface MigrateClassroomOptions {
  /** Override the published courseware id (defaults to the classroom id). */
  coursewareId?: string;
  /** Explicit version (defaults to the repo's next monotonic version). */
  version?: number;
  baseUrl: string;
  resolvers?: ClassroomByteResolvers;
  repos?: {
    records?: CoursewareRepo;
    bytes?: BundleByteStore;
  };
}

export type MigrateClassroomResult =
  | {
      status: 'published';
      classroomId: string;
      coursewareId: string;
      version: number;
      record: Awaited<ReturnType<typeof publishCourseware>>['record'];
    }
  | {
      status: 'incomplete';
      classroomId: string;
      coursewareId: string;
      /** Human-readable missing-resource summary for the report. */
      missing: string[];
      completeness: PackageResult['completeness'];
    };

/**
 * Re-package one persisted classroom and publish it. Never publishes a broken
 * bundle: missing audio/media produce an `incomplete` result instead.
 */
export async function migrateClassroomToCourseware(
  classroom: PersistedClassroomData,
  options: MigrateClassroomOptions,
): Promise<MigrateClassroomResult> {
  const coursewareId = options.coursewareId ?? classroom.id;
  const { stage, scenes } = classroom;
  const resolvers = options.resolvers ?? {};

  const packaged = await packageCourseware({
    coursewareId,
    version: options.version,
    stage,
    scenes,
    agentConfigs: stage.generatedAgentConfigs ?? [],
    resolveAudioBytes: resolvers.resolveAudioBytes,
    resolveMediaBytes: resolvers.resolveMediaBytes,
    requireComplete: false, // report instead of throwing; the gate below decides
  });

  if (!packaged.completeness.complete) {
    const missing = packaged.completeness.missing.map(
      (m) => `${m.kind}:${m.ref}${m.sceneId ? ` (scene ${m.sceneId})` : ''}`,
    );
    log.warn(`Classroom ${classroom.id} incomplete — not published (${missing.length} gaps)`);
    return {
      status: 'incomplete',
      classroomId: classroom.id,
      coursewareId,
      missing,
      completeness: packaged.completeness,
    };
  }

  const { record } = await publishCourseware({
    zipBytes: new Uint8Array(await packaged.zip.arrayBuffer()),
    coursewareId,
    baseUrl: options.baseUrl,
    version: options.version,
    repos: {
      records: options.repos?.records ?? createFileCoursewareRepo(COURSEWARES_DIR),
      bytes: options.repos?.bytes ?? createFileBundleByteStore(COURSEWARE_BUNDLES_DIR),
    },
  });

  log.info(`Published ${classroom.id} as ${coursewareId} v${record.version}`);
  return {
    status: 'published',
    classroomId: classroom.id,
    coursewareId,
    version: record.version,
    record,
  };
}

/** Scan + migrate every classroom in the server classrooms dir. */
export async function migrateAllClassrooms(options: {
  baseUrl: string;
  resolvers?: ClassroomByteResolvers;
  classroomsDir?: string;
  repos?: MigrateClassroomOptions['repos'];
}): Promise<{
  published: MigrateClassroomResult[];
  incomplete: MigrateClassroomResult[];
  skipped: string[];
}> {
  const dir = options.classroomsDir ?? CLASSROOMS_DIR;

  let files: string[];
  try {
    files = await fs.readdir(dir);
  } catch {
    return { published: [], incomplete: [], skipped: [] };
  }

  const results: MigrateClassroomResult[] = [];
  const skipped: string[] = [];
  for (const file of files.filter((f) => f.endsWith('.json')).sort()) {
    const classroomId = path.basename(file, '.json');
    let classroom: PersistedClassroomData;
    try {
      const content = await fs.readFile(path.join(dir, file), 'utf-8');
      classroom = JSON.parse(content) as PersistedClassroomData;
    } catch {
      skipped.push(classroomId);
      continue;
    }
    results.push(
      await migrateClassroomToCourseware(classroom, {
        coursewareId: classroomId,
        baseUrl: options.baseUrl,
        resolvers: options.resolvers,
        repos: options.repos,
      }),
    );
  }
  return {
    published: results.filter((r) => r.status === 'published'),
    incomplete: results.filter((r) => r.status === 'incomplete'),
    skipped,
  };
}