const { getDBConnection } = require('./file-utils');

// 获取所有问题
function getQuestions() {
  try {
    const db = getDBConnection(true);
    
    const questions = db.prepare(`
      SELECT q.*, 
             COUNT(a.id) as answer_count,
             MAX(a.created_at) as last_answer_time
      FROM questions q
      LEFT JOIN answers a ON q.id = a.question_id
      GROUP BY q.id
      ORDER BY q.created_at DESC
    `).all();

    // 获取每个问题的回答
    questions.forEach(question => {
      question.answers = db.prepare(`
        SELECT * FROM answers 
        WHERE question_id = ? 
        ORDER BY created_at ASC
      `).all(question.id);
    });

    return questions;
  } catch (error) {
    console.error('获取问题列表失败:', error);
    throw error;
  }
}

// 创建新问题
function createQuestion(title, content, author) {
  try {
    if (!title || !content) {
      throw new Error('标题和内容不能为空');
    }

    const db = getDBConnection();
    
    const result = db.prepare(`
      INSERT INTO questions (title, content, author)
      VALUES (?, ?, ?)
    `).run(title, content, author || '匿名用户');

    if (result.changes > 0) {
      return {
        success: true,
        questionId: result.lastInsertRowid,
        message: '问题创建成功'
      };
    } else {
      throw new Error('问题创建失败');
    }
  } catch (error) {
    console.error('创建问题失败:', error);
    throw error;
  }
}

// 添加回答
function addAnswer(questionId, content, author) {
  try {
    if (!content) {
      throw new Error('回答内容不能为空');
    }

    const db = getDBConnection();
    
    // 检查问题是否存在
    const question = db.prepare('SELECT id FROM questions WHERE id = ?').get(questionId);
    if (!question) {
      throw new Error('问题不存在');
    }

    const result = db.prepare(`
      INSERT INTO answers (question_id, content, author)
      VALUES (?, ?, ?)
    `).run(questionId, content, author || '匿名用户');

    if (result.changes > 0) {
      return {
        success: true,
        answerId: result.lastInsertRowid,
        message: '回答添加成功'
      };
    } else {
      throw new Error('回答添加失败');
    }
  } catch (error) {
    console.error('添加回答失败:', error);
    throw error;
  }
}

// 删除问题
function deleteQuestion(questionId) {
  try {
    const db = getDBConnection();
    
    const result = db.prepare('DELETE FROM questions WHERE id = ?').run(questionId);

    if (result.changes > 0) {
      return {
        success: true,
        message: '问题删除成功'
      };
    } else {
      throw new Error('问题不存在');
    }
  } catch (error) {
    console.error('删除问题失败:', error);
    throw error;
  }
}

// 删除回答
function deleteAnswer(answerId) {
  try {
    const db = getDBConnection();
    
    const result = db.prepare('DELETE FROM answers WHERE id = ?').run(answerId);

    if (result.changes > 0) {
      return {
        success: true,
        message: '回答删除成功'
      };
    } else {
      throw new Error('回答不存在');
    }
  } catch (error) {
    console.error('删除回答失败:', error);
    throw error;
  }
}

module.exports = {
  getQuestions,
  createQuestion,
  addAnswer,
  deleteQuestion,
  deleteAnswer
};