import path from 'path';
import fs from 'fs';
import { v4 as uuidv4 } from 'uuid';
import { createRequire } from 'module';
import { fileURLToPath } from 'url';

// 在ES模块中创建require函数，用于兼容CommonJS模块
const require = createRequire(import.meta.url);

const DEFAULT_DB_DIR = path.join(process.cwd(), 'data');
const DEFAULT_DB_PATH = path.join(DEFAULT_DB_DIR, 'survey.db');

const DB_PATH = process.env.DB_PATH || DEFAULT_DB_PATH;
const DB_DIR = path.dirname(DB_PATH);

// 确保数据目录存在
if (!fs.existsSync(DB_DIR)) {
  fs.mkdirSync(DB_DIR, { recursive: true });
}

// 延迟初始化数据库连接
let db: any = null;
let isInitialized = false;

// 初始化数据库连接的函数
export const initDbConnection = async () => {
  if (!isInitialized) {
    try {
      // 使用require加载sqlite3，因为它是CommonJS模块
      const sqlite3 = require('sqlite3');
      db = new sqlite3.Database(DB_PATH, (err: Error) => {
        if (err) {
          console.error('数据库连接失败:', err);
        } else {
          console.log('数据库连接成功');
          // 启用外键约束
          db.run('PRAGMA foreign_keys = ON');
        }
      });
      isInitialized = true;
    } catch (error) {
      console.error('初始化数据库失败:', error);
      // 初始化失败，不设置isInitialized为true，允许后续调用再次尝试
      return null;
    }
  }
  return db;
};

// 导出一个函数，用于获取数据库连接
export const getDb = async () => {
  if (!db) {
    return await initDbConnection();
  }
  return db;
};

const exec = async (sql: string): Promise<void> => {
  return new Promise(async (resolve, reject) => {
    const db = await getDb();
    if (!db) {
      reject(new Error('数据库连接未初始化'));
      return;
    }
    db.exec(sql, (err: Error) => {
      if (err) reject(err);
      else resolve();
    });
  });
};

const tableExists = async (tableName: string): Promise<boolean> => {
  const row = await get(
    "SELECT name FROM sqlite_master WHERE type='table' AND name=?",
    [tableName]
  );
  return Boolean(row);
};

const columnExists = async (tableName: string, columnName: string): Promise<boolean> => {
  const columns = await query(`PRAGMA table_info(${tableName})`);
  return columns.some((col: any) => col.name === columnName);
};

const ensureColumn = async (tableName: string, columnDefSql: string, columnName: string) => {
  if (!(await columnExists(tableName, columnName))) {
    console.log(`添加列 ${tableName}.${columnName}`);
    await exec(`ALTER TABLE ${tableName} ADD COLUMN ${columnDefSql}`);
  } else {
    console.log(`列 ${tableName}.${columnName} 已存在`);
  }
};

const ensureTable = async (createTableSql: string) => {
  await exec(createTableSql);
};

const ensureIndex = async (createIndexSql: string) => {
  await exec(createIndexSql);
};

const ensureUserGroupSchemaAndAllUsersMembership = async () => {
  // 1) Ensure tables
  await ensureTable(`
    CREATE TABLE IF NOT EXISTS user_groups (
      id TEXT PRIMARY KEY,
      name TEXT UNIQUE NOT NULL,
      description TEXT NOT NULL DEFAULT '',
      is_system BOOLEAN NOT NULL DEFAULT 0,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    );
  `);

  await ensureTable(`
    CREATE TABLE IF NOT EXISTS user_group_members (
      group_id TEXT NOT NULL,
      user_id TEXT NOT NULL,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
      PRIMARY KEY (group_id, user_id),
      FOREIGN KEY (group_id) REFERENCES user_groups(id) ON DELETE CASCADE,
      FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
    );
  `);

  // 2) Ensure indexes
  await ensureIndex(
    `CREATE INDEX IF NOT EXISTS idx_user_group_members_group_id ON user_group_members(group_id);`,
  );
  await ensureIndex(
    `CREATE INDEX IF NOT EXISTS idx_user_group_members_user_id ON user_group_members(user_id);`,
  );

  // 3) Ensure system group exists
  const existingSystemGroup = await get(
    `SELECT id FROM user_groups WHERE is_system = 1 ORDER BY created_at ASC LIMIT 1`,
  );

  let systemGroupId = existingSystemGroup?.id as string | undefined;
  if (!systemGroupId) {
    const preferredId = 'all-users';
    try {
      await run(
        `INSERT INTO user_groups (id, name, description, is_system) VALUES (?, ?, ?, 1)`,
        [preferredId, '全体用户', '系统内置：新用户自动加入'],
      );
      systemGroupId = preferredId;
    } catch {
      const fallbackId = uuidv4();
      await run(
        `INSERT INTO user_groups (id, name, description, is_system) VALUES (?, ?, ?, 1)`,
        [fallbackId, '全体用户', '系统内置：新用户自动加入'],
      );
      systemGroupId = fallbackId;
    }
  }

  // 4) Backfill membership: ensure all existing users are in the system group
  if (systemGroupId) {
    await run(
      `INSERT OR IGNORE INTO user_group_members (group_id, user_id)
       SELECT ?, u.id FROM users u`,
      [systemGroupId],
    );
  }
};

const migrateDatabase = async () => {
  // 跳过迁移，因为数据库连接可能未初始化
  console.log('跳过数据库迁移');
};

// 数据库初始化函数
export const initDatabase = async () => {
  try {
    // 确保数据库连接已初始化
    await initDbConnection();
    
    // 检查是否需要初始化：如果users表不存在，则执行初始化
    const usersTableExists = await tableExists('users');
    
    if (!usersTableExists) {
      // 读取并执行初始化SQL文件
      const initSqlPath = fileURLToPath(new URL('./init.sql', import.meta.url));
      const initSql = fs.readFileSync(initSqlPath, 'utf8');
      
      await exec(initSql);
      console.log('数据库初始化成功');

      // 用户组（含“全体用户”系统组）
      await ensureUserGroupSchemaAndAllUsersMembership();
    } else {
      console.log('数据库表已存在，跳过初始化');
      await ensureColumn('questions', "analysis TEXT NOT NULL DEFAULT ''", 'analysis');
      await ensureColumn('quiz_records', "score_percentage REAL", 'score_percentage');
      await ensureColumn('quiz_records', "status TEXT", 'status');

      // 用户组（含“全体用户”系统组）
      await ensureUserGroupSchemaAndAllUsersMembership();
    }
  } catch (error) {
    console.error('数据库初始化失败:', error);
    // 即使初始化失败，服务器也应该继续运行
  }
};

// 数据库查询工具函数
export const query = async (sql: string, params: any[] = []): Promise<any[]> => {
  return new Promise(async (resolve, reject) => {
    const db = await getDb();
    if (!db) {
      reject(new Error('数据库连接未初始化'));
      return;
    }
    db.all(sql, params, (err: Error, rows: any[]) => {
      if (err) {
        reject(err);
      } else {
        resolve(rows);
      }
    });
  });
};

// all函数是query函数的别名，用于向后兼容
export const all = query;

export const run = async (sql: string, params: any[] = []): Promise<{ id: string }> => {
  return new Promise(async (resolve, reject) => {
    const db = await getDb();
    if (!db) {
      reject(new Error('数据库连接未初始化'));
      return;
    }
    db.run(sql, params, function(this: any, err: Error | null) {
      if (err) {
        reject(err);
      } else {
        resolve({ id: this.lastID ? this.lastID.toString() : '' });
      }
    });
  });
};

export const get = async (sql: string, params: any[] = []): Promise<any> => {
  return new Promise(async (resolve, reject) => {
    const db = await getDb();
    if (!db) {
      reject(new Error('数据库连接未初始化'));
      return;
    }
    db.get(sql, params, (err: Error, row: any) => {
      if (err) {
        reject(err);
      } else {
        resolve(row);
      }
    });
  });
};