/**
 * 把旧库数据编排成新库可直接写入的数据集。
 *
 * 逻辑集中在这里，migrate.ts（写库）与 transform.test.ts（校验）共用同一份实现，
 * 避免两边各写一遍导致漂移。
 */

import { asString, type LegacyRows } from './load';
import {
  HOME_COURSE_TITLE_MAP,
  OPENID_RE,
  transformArticle,
  transformBanner,
  transformCourse,
  transformCourseTip,
  transformEntitlement,
  transformFreeLesson,
  transformHomeCourse,
  transformHomeFreeCourse,
  transformLesson,
  transformSetting,
  transformUser,
} from './transform';

export type Dataset = ReturnType<typeof buildDataset>;

export function buildDataset(db: LegacyRows, staticBase: string) {
  // 先建课程，得到 code → 自增 id 的映射（新库 id 从 1 开始，与插入顺序一致）
  const courses = db.课程口令码读取信息.map(transformCourse);
  const courseIdByCode = new Map(courses.map((c, i) => [c.code, i + 1]));
  const courseIdByTitle = new Map(courses.map((c, i) => [c.title, i + 1]));

  // 过滤旧库里混入的攻击载荷：只有符合 openid 形态的才当作真实用户
  const skippedUsers: Array<{ openid: string; reason: string }> = [];
  const users = db.用户信息.flatMap((row) => {
    const openid = asString(row.OpenID);
    if (!OPENID_RE.test(openid)) {
      skippedUsers.push({ openid: openid.slice(0, 60), reason: '非法 openid 形态（疑似攻击载荷）' });
      return [];
    }
    return [transformUser(row)];
  });
  const userIdByOpenid = new Map(users.map((u, i) => [u.openid, i + 1]));

  const skippedLessonOrphans: string[] = [];
  const lessons = db.视频课程数据.flatMap((row) => {
    const courseId = courseIdByCode.get(asString(row.课程id));
    if (!courseId) {
      skippedLessonOrphans.push(asString(row.课程id));
      return [];
    }
    return [transformLesson(row, courseId)];
  });

  // 权益：按 (user, course) 去重，重复的只保留第一条
  const seen = new Set<string>();
  const duplicateEntitlements: string[] = [];
  const droppedEntitlements: string[] = [];
  const entitlements = db.用户已购课程.flatMap((row) => {
    const userId = userIdByOpenid.get(asString(row.OpenID));
    const courseId = courseIdByCode.get(asString(row.课程id));
    if (!userId || !courseId) {
      droppedEntitlements.push(`${asString(row.OpenID).slice(0, 30)}::${asString(row.课程id).slice(0, 12)}`);
      return [];
    }
    const key = `${userId}::${courseId}`;
    if (seen.has(key)) {
      duplicateEntitlements.push(key);
      return [];
    }
    seen.add(key);
    return [transformEntitlement(row, userId, courseId)];
  });

  const unmappedHomeCourses: string[] = [];
  const homeCourses = db.首页课程列表.map((row) => {
    const courseName = asString(row.课程名称);
    const title = HOME_COURSE_TITLE_MAP[courseName];
    const courseId = title ? courseIdByTitle.get(title) ?? null : null;
    if (courseId === null) unmappedHomeCourses.push(courseName);
    return transformHomeCourse(row, courseId, staticBase);
  });

  return {
    courses,
    users,
    lessons,
    entitlements,
    homeCourses,
    freeLessons: db.免费视频课程数据.map(transformFreeLesson),
    homeFreeCourses: db.首页免费课程列表.map(transformHomeFreeCourse),
    banners: db.首页横幅图片.map(transformBanner),
    articles: db.网页列表.map((row) => transformArticle(row, staticBase)),
    courseTips: db.课程页面Tips.map(transformCourseTip),
    settings: db.cloudconfig
      .map(transformSetting)
      .filter((v): v is NonNullable<typeof v> => v !== null),
    diagnostics: {
      skippedLessonOrphans,
      duplicateEntitlements,
      unmappedHomeCourses,
      skippedUsers,
      droppedEntitlements,
    },
  };
}