const sqlite3 = require('sqlite3').verbose();
const path = require('path');
const fs = require('fs');

const dbPath = path.join(__dirname, '..', 'data', 'database.sqlite');
const migrationsDir = __dirname;

class MigrationManager {
  constructor() {
    this.db = new sqlite3.Database(dbPath);
  }

  // 初始化迁移表
  async initMigrationTable() {
    return new Promise((resolve, reject) => {
      this.db.run(`
        CREATE TABLE IF NOT EXISTS migrations (
          id INTEGER PRIMARY KEY AUTOINCREMENT,
          version INTEGER NOT NULL UNIQUE,
          name TEXT NOT NULL,
          executed_at DATETIME DEFAULT CURRENT_TIMESTAMP
        )
      `, (err) => {
        if (err) reject(err);
        else resolve();
      });
    });
  }

  // 获取已执行的迁移版本
  async getExecutedMigrations() {
    return new Promise((resolve, reject) => {
      this.db.all('SELECT version FROM migrations ORDER BY version', (err, rows) => {
        if (err) reject(err);
        else resolve(rows.map(r => r.version));
      });
    });
  }

  // 记录迁移执行
  async recordMigration(version, name) {
    return new Promise((resolve, reject) => {
      this.db.run(
        'INSERT INTO migrations (version, name) VALUES (?, ?)',
        [version, name],
        (err) => {
          if (err) reject(err);
          else resolve();
        }
      );
    });
  }

  // 执行SQL语句
  async executeSql(sql) {
    return new Promise((resolve, reject) => {
      this.db.run(sql, (err) => {
        if (err) {
          // 忽略字段已存在的错误
          if (err.message.includes('duplicate column name')) {
            resolve();
          } else {
            reject(err);
          }
        } else {
          resolve();
        }
      });
    });
  }

  // 加载所有迁移文件
  loadMigrations() {
    const files = fs.readdirSync(migrationsDir)
      .filter(f => f.match(/^\d{4}-.*\.js$/) && f !== 'index.js')
      .sort();

    return files.map(file => {
      const version = parseInt(file.split('-')[0]);
      const name = file.replace(/^\d{4}-/, '').replace('.js', '');
      const migration = require(path.join(migrationsDir, file));
      return { version, name, file, migration };
    });
  }

  // 执行迁移
  async runMigrations() {
    try {
      console.log('🔄 开始数据库迁移...\n');
      
      // 初始化迁移表
      await this.initMigrationTable();
      
      // 获取已执行的迁移
      const executed = await this.getExecutedMigrations();
      console.log(`📊 已执行迁移: ${executed.length} 个`);
      
      // 加载所有迁移文件
      const migrations = this.loadMigrations();
      console.log(`📁 发现迁移文件: ${migrations.length} 个\n`);
      
      // 执行未执行的迁移
      let count = 0;
      for (const { version, name, file, migration } of migrations) {
        if (!executed.includes(version)) {
          console.log(`⏳ 执行迁移 [${version}] ${name}...`);
          
          try {
            await migration.up(this);
            await this.recordMigration(version, name);
            console.log(`✅ 迁移 [${version}] ${name} 完成\n`);
            count++;
          } catch (error) {
            console.error(`❌ 迁移 [${version}] ${name} 失败:`, error.message);
            throw error;
          }
        } else {
          console.log(`⏭️  跳过已执行的迁移 [${version}] ${name}`);
        }
      }
      
      console.log(`\n✨ 迁移完成！共执行 ${count} 个新迁移`);
      
    } catch (error) {
      console.error('\n❌ 迁移失败:', error);
      throw error;
    } finally {
      this.db.close();
    }
  }
}

// 如果直接运行此文件
if (require.main === module) {
  const manager = new MigrationManager();
  manager.runMigrations()
    .then(() => process.exit(0))
    .catch(() => process.exit(1));
}

module.exports = MigrationManager;