/**
 * 文件变更追踪服务
 * 功能：收集和管理 AI 修改文件的变更记录
 * 依赖：types/fileChanges
 * 使用场景：在文件操作时记录变更，供用户审查
 */

import { FileChange, ChangeSession } from '../types/fileChanges';
import * as vscode from 'vscode';
import * as fs from 'fs';
import * as path from 'path';

class ChangeTrackerService {
  private currentSession: ChangeSession | null = null;
  private changeListeners: Array<(session: ChangeSession) => void> = [];

  /**
   * 开始新的变更会话
   */
  startSession(sessionId: string): void {
    // 如果已有 session（无论状态），重用并重置为 active
    if (this.currentSession) {
      this.currentSession.status = 'active';
      return;
    }

    this.currentSession = {
      sessionId,
      startTime: Date.now(),
      changes: [],
      status: 'active'
    };
  }

  /**
   * 记录文件变更
   */
  trackChange(filePath: string, oldContent: string, newContent: string): string {
    if (!this.currentSession) {
      this.startSession(`session_${Date.now()}`);
    }

    const changeId = `change_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;

    // 判断变更类型
    let changeType: 'create' | 'modify' | 'delete';
    if (oldContent === '' && newContent !== '') {
      changeType = 'create';
    } else if (oldContent !== '' && newContent === '') {
      changeType = 'delete';
    } else {
      changeType = 'modify';
    }

    const change: FileChange = {
      filePath,
      oldContent,
      newContent,
      timestamp: Date.now(),
      changeType,
      changeId
    };

    this.currentSession!.changes.push(change);
    this.notifyListeners();

    return changeId;
  }

  /**
   * 结束当前会话
   */
  endSession(): ChangeSession | null {
    if (this.currentSession && this.currentSession.changes.length > 0) {
      this.currentSession.status = 'completed';
      const session = this.currentSession;
      this.notifyListeners();
      return session;
    }
    return null;
  }

  /**
   * 获取当前会话
   */
  getCurrentSession(): ChangeSession | null {
    return this.currentSession;
  }

  /**
   * 清空当前会话
   */
  clearSession(): void {
    this.currentSession = null;
    this.notifyListeners();
  }

  /**
   * 移除指定的变更
   */
  removeChange(changeId: string): boolean {
    if (!this.currentSession) {
      return false;
    }

    const index = this.currentSession.changes.findIndex(c => c.changeId === changeId);
    if (index !== -1) {
      this.currentSession.changes.splice(index, 1);
      this.notifyListeners();
      return true;
    }
    return false;
  }

  /**
   * 监听变更
   */
  onChangeUpdate(listener: (session: ChangeSession) => void): void {
    this.changeListeners.push(listener);
  }

  /**
   * 通知所有监听器
   */
  private notifyListeners(): void {
    if (this.currentSession) {
      this.changeListeners.forEach(listener => listener(this.currentSession!));
    }
  }

  /**
   * 采纳变更（保存文件）
   */
  async acceptChange(changeId: string): Promise<boolean> {
    if (!this.currentSession) {
      return false;
    }

    const change = this.currentSession.changes.find(c => c.changeId === changeId);
    if (!change) {
      return false;
    }

    try {
      const workspaceFolder = vscode.workspace.workspaceFolders?.[0];
      if (!workspaceFolder) {
        return false;
      }

      const absolutePath = path.join(workspaceFolder.uri.fsPath, change.filePath);

      // 如果是删除操作，删除文件
      if (change.changeType === 'delete') {
        if (fs.existsSync(absolutePath)) {
          await fs.promises.unlink(absolutePath);
        }
      } else {
        // 创建或修改文件
        await fs.promises.writeFile(absolutePath, change.newContent, 'utf-8');
      }

      this.removeChange(changeId);
      return true;
    } catch (error) {
      console.error('[ChangeTracker] 采纳变更失败:', error);
      return false;
    }
  }

  /**
   * 拒绝变更（恢复旧内容）
   */
  async rejectChange(changeId: string): Promise<boolean> {
    if (!this.currentSession) {
      return false;
    }

    const change = this.currentSession.changes.find(c => c.changeId === changeId);
    if (!change) {
      return false;
    }

    try {
      const workspaceFolder = vscode.workspace.workspaceFolders?.[0];
      if (!workspaceFolder) {
        return false;
      }

      const absolutePath = path.join(workspaceFolder.uri.fsPath, change.filePath);

      // 如果是新建文件，删除它
      if (change.changeType === 'create') {
        if (fs.existsSync(absolutePath)) {
          await fs.promises.unlink(absolutePath);
        }
      } else {
        // 恢复旧内容
        await fs.promises.writeFile(absolutePath, change.oldContent, 'utf-8');
      }

      this.removeChange(changeId);
      return true;
    } catch (error) {
      console.error('[ChangeTracker] 拒绝变更失败:', error);
      return false;
    }
  }
}

export const changeTracker = new ChangeTrackerService();