import sqlite3 from 'sqlite3';
import path from 'path';
import fs from 'fs';

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 });
}

// 创建数据库连接
export const db = new sqlite3.Database(DB_PATH, (err) => {
  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');

const exec = (sql: string): Promise<void> => {
  return new Promise((resolve, reject) => {
    db.exec(sql, (err) => {
      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))) {
    await exec(`ALTER TABLE ${tableName} ADD COLUMN ${columnDefSql}`);
  }
};

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

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

const migrateDatabase = async () => {
  await ensureColumn('users', `password TEXT NOT NULL DEFAULT ''`, 'password');

  await ensureColumn('questions', `category TEXT NOT NULL DEFAULT '通用'`, 'category');
  await run(`UPDATE questions SET category = '通用' WHERE category IS NULL OR category = ''`);

  await ensureTable(`
    CREATE TABLE IF NOT EXISTS question_categories (
      id TEXT PRIMARY KEY,
      name TEXT UNIQUE NOT NULL,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    );
  `);

  await run(
    `INSERT OR IGNORE INTO question_categories (id, name) VALUES ('default', '通用')`
  );

  await ensureTable(`
    CREATE TABLE IF NOT EXISTS exam_subjects (
      id TEXT PRIMARY KEY,
      name TEXT UNIQUE NOT NULL,
      type_ratios TEXT NOT NULL,
      category_ratios TEXT NOT NULL,
      total_score INTEGER NOT NULL,
      duration_minutes INTEGER NOT NULL DEFAULT 60,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
      updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
    );
  `);

  await ensureTable(`
    CREATE TABLE IF NOT EXISTS exam_tasks (
      id TEXT PRIMARY KEY,
      name TEXT NOT NULL,
      subject_id TEXT NOT NULL,
      start_at DATETIME NOT NULL,
      end_at DATETIME NOT NULL,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
      FOREIGN KEY (subject_id) REFERENCES exam_subjects(id)
    );
  `);

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

  if (await tableExists('quiz_records')) {
    await ensureColumn('quiz_records', `subject_id TEXT`, 'subject_id');
    await ensureColumn('quiz_records', `task_id TEXT`, 'task_id');
  }

  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_questions_category ON questions(category);`);
  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_exam_tasks_subject_id ON exam_tasks(subject_id);`);
  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_exam_task_users_task_id ON exam_task_users(task_id);`);
  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_exam_task_users_user_id ON exam_task_users(user_id);`);
  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_quiz_records_subject_id ON quiz_records(subject_id);`);
  await ensureIndex(`CREATE INDEX IF NOT EXISTS idx_quiz_records_task_id ON quiz_records(task_id);`);
};

// 数据库初始化函数
export const initDatabase = async () => {
  const initSQL = fs.readFileSync(path.join(process.cwd(), 'api', 'database', 'init.sql'), 'utf8');

  const hasUsersTable = await tableExists('users');
  if (!hasUsersTable) {
    await exec(initSQL);
    console.log('数据库初始化成功');
  } else {
    console.log('数据库已初始化，准备执行迁移检查');
  }

  await migrateDatabase();
};

// 数据库查询工具函数
export const query = (sql: string, params: any[] = []): Promise<any[]> => {
  return new Promise((resolve, reject) => {
    db.all(sql, params, (err, rows) => {
      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 = (sql: string, params: any[] = []): Promise<{ id: string }> => {
  return new Promise((resolve, reject) => {
    db.run(sql, params, function(err) {
      if (err) {
        reject(err);
      } else {
        resolve({ id: this.lastID.toString() });
      }
    });
  });
};

export const get = (sql: string, params: any[] = []): Promise<any> => {
  return new Promise((resolve, reject) => {
    db.get(sql, params, (err, row) => {
      if (err) {
        reject(err);
      } else {
        resolve(row);
      }
    });
  });
};