import { v4 as uuidv4 } from 'uuid';
import { get, query, run } from '../database';

export type QuestionType = 'single' | 'multiple' | 'judgment' | 'text';

export interface ExamSubject {
  id: string;
  name: string;
  totalScore: number;
  timeLimitMinutes: number;
  typeRatios: Record<QuestionType, number>;
  categoryRatios: Record<string, number>;
  createdAt: string;
  updatedAt: string;
}

type RawSubjectRow = {
  id: string;
  name: string;
  typeRatios: string;
  categoryRatios: string;
  totalScore: number;
  timeLimitMinutes: number;
  createdAt: string;
  updatedAt: string;
};

const parseJson = <T>(value: string, fallback: T): T => {
  try {
    return JSON.parse(value) as T;
  } catch {
    return fallback;
  }
};

const validateRatiosSum100 = (ratios: Record<string, number>, label: string) => {
  const values = Object.values(ratios);
  if (values.length === 0) throw new Error(`${label}不能为空`);
  if (values.some((v) => typeof v !== 'number' || Number.isNaN(v) || v < 0)) {
    throw new Error(`${label}必须是非负数字`);
  }
  const sum = values.reduce((a, b) => a + b, 0);
  if (Math.abs(sum - 100) > 0.01) {
    throw new Error(`${label}总和必须为100`);
  }
};

export class ExamSubjectModel {
  static async findAll(): Promise<ExamSubject[]> {
    const sql = `
      SELECT 
        id,
        name,
        type_ratios as typeRatios,
        category_ratios as categoryRatios,
        total_score as totalScore,
        duration_minutes as timeLimitMinutes,
        created_at as createdAt,
        updated_at as updatedAt
      FROM exam_subjects
      ORDER BY created_at DESC
    `;

    const rows: RawSubjectRow[] = await query(sql);
    return rows.map((row) => ({
      id: row.id,
      name: row.name,
      totalScore: row.totalScore,
      timeLimitMinutes: row.timeLimitMinutes,
      typeRatios: parseJson<Record<QuestionType, number>>(row.typeRatios, {
        single: 40,
        multiple: 30,
        judgment: 20,
        text: 10
      }),
      categoryRatios: parseJson<Record<string, number>>(row.categoryRatios, { 通用: 100 }),
      createdAt: row.createdAt,
      updatedAt: row.updatedAt
    }));
  }

  static async findById(id: string): Promise<ExamSubject | null> {
    const sql = `
      SELECT 
        id,
        name,
        type_ratios as typeRatios,
        category_ratios as categoryRatios,
        total_score as totalScore,
        duration_minutes as timeLimitMinutes,
        created_at as createdAt,
        updated_at as updatedAt
      FROM exam_subjects
      WHERE id = ?
    `;

    const row: RawSubjectRow | undefined = await get(sql, [id]);
    if (!row) return null;

    return {
      id: row.id,
      name: row.name,
      totalScore: row.totalScore,
      timeLimitMinutes: row.timeLimitMinutes,
      typeRatios: parseJson<Record<QuestionType, number>>(row.typeRatios, {
        single: 40,
        multiple: 30,
        judgment: 20,
        text: 10
      }),
      categoryRatios: parseJson<Record<string, number>>(row.categoryRatios, { 通用: 100 }),
      createdAt: row.createdAt,
      updatedAt: row.updatedAt
    };
  }

  static async create(data: {
    name: string;
    totalScore: number;
    timeLimitMinutes?: number;
    typeRatios: Record<QuestionType, number>;
    categoryRatios?: Record<string, number>;
  }): Promise<ExamSubject> {
    const name = data.name.trim();
    if (!name) throw new Error('科目名称不能为空');
    if (!data.totalScore || data.totalScore <= 0) throw new Error('总分必须为正整数');

    const timeLimitMinutes = data.timeLimitMinutes ?? 60;
    if (!Number.isInteger(timeLimitMinutes) || timeLimitMinutes <= 0) throw new Error('答题时间必须为正整数(分钟)');

    validateRatiosSum100(data.typeRatios, '题型比重');
    const categoryRatios = data.categoryRatios && Object.keys(data.categoryRatios).length > 0 ? data.categoryRatios : { 通用: 100 };
    validateRatiosSum100(categoryRatios, '题目类别比重');

    const id = uuidv4();
    const sql = `
      INSERT INTO exam_subjects (
        id, name, type_ratios, category_ratios, total_score, duration_minutes, updated_at
      ) VALUES (?, ?, ?, ?, ?, ?, datetime('now'))
    `;

    try {
      await run(sql, [
        id,
        name,
        JSON.stringify(data.typeRatios),
        JSON.stringify(categoryRatios),
        data.totalScore,
        timeLimitMinutes
      ]);
    } catch (error: any) {
      if (error.code === 'SQLITE_CONSTRAINT_UNIQUE') {
        throw new Error('科目名称已存在');
      }
      throw error;
    }

    return (await this.findById(id)) as ExamSubject;
  }

  static async update(id: string, data: {
    name: string;
    totalScore: number;
    timeLimitMinutes?: number;
    typeRatios: Record<QuestionType, number>;
    categoryRatios?: Record<string, number>;
  }): Promise<ExamSubject> {
    const existing = await this.findById(id);
    if (!existing) throw new Error('科目不存在');

    const name = data.name.trim();
    if (!name) throw new Error('科目名称不能为空');
    if (!data.totalScore || data.totalScore <= 0) throw new Error('总分必须为正整数');

    const timeLimitMinutes = data.timeLimitMinutes ?? 60;
    if (!Number.isInteger(timeLimitMinutes) || timeLimitMinutes <= 0) throw new Error('答题时间必须为正整数(分钟)');

    validateRatiosSum100(data.typeRatios, '题型比重');
    const categoryRatios = data.categoryRatios && Object.keys(data.categoryRatios).length > 0 ? data.categoryRatios : { 通用: 100 };
    validateRatiosSum100(categoryRatios, '题目类别比重');

    const sql = `
      UPDATE exam_subjects 
      SET name = ?, type_ratios = ?, category_ratios = ?, total_score = ?, duration_minutes = ?, updated_at = datetime('now')
      WHERE id = ?
    `;

    try {
      await run(sql, [
        name,
        JSON.stringify(data.typeRatios),
        JSON.stringify(categoryRatios),
        data.totalScore,
        timeLimitMinutes,
        id
      ]);
    } catch (error: any) {
      if (error.code === 'SQLITE_CONSTRAINT_UNIQUE') {
        throw new Error('科目名称已存在');
      }
      throw error;
    }

    return (await this.findById(id)) as ExamSubject;
  }

  static async delete(id: string): Promise<void> {
    const existing = await this.findById(id);
    if (!existing) throw new Error('科目不存在');

    const taskCount = await get(`SELECT COUNT(*) as total FROM exam_tasks WHERE subject_id = ?`, [id]);
    if (taskCount && taskCount.total > 0) {
      throw new Error('该科目已被考试任务使用，无法删除');
    }

    await run(`DELETE FROM exam_subjects WHERE id = ?`, [id]);
  }
}