5.2 文件编辑算法进化史：从 Diff 到精确锚点替换

// file-editor.ts
import * as fs from 'fs/promises';
 
export interface ReplaceOptions {
  filePath: string;
  targetContent: string;
  replacementContent: string;
  startLine?: number;
  endLine?: number;
}
 
export class SafeFileEditor {
  /**
   * 执行精确锚点替换
   */
  static async replaceContent(opts: ReplaceOptions): Promise<{ success: boolean; message: string }> {
    const { filePath, targetContent, replacementContent, startLine, endLine } = opts;
 
    let fileText: string;
    try {
      fileText = await fs.readFile(filePath, 'utf-8');
    } catch (err: any) {
      return { success: false, message: `无法读取文件: ${err.message}` };
    }
 
    // 1. 如果指定了行号区间，只在区间内检索与替换
    if (startLine !== undefined && endLine !== undefined) {
      const lines = fileText.split('\n');
      const prefixLines = lines.slice(0, startLine - 1);
      const targetLines = lines.slice(startLine - 1, endLine);
      const suffixLines = lines.slice(endLine);
 
      const targetBlock = targetLines.join('\n');
      const count = targetBlock.split(targetContent).length - 1;
 
      if (count === 0) {
        return {
          success: false,
          message: `在第 ${startLine} 至 ${endLine} 行区间内未找到精确匹配的 targetContent。`,
        };
      }
      if (count > 1) {
        return {
          success: false,
          message: `在指定区间内找到 ${count} 处重复匹配，请扩大锚点消除歧义。`,
        };
      }
 
      const replacedBlock = targetBlock.replace(targetContent, replacementContent);
      const fullNewContent = [...prefixLines, replacedBlock, ...suffixLines].join('\n');
      await fs.writeFile(filePath, fullNewContent, 'utf-8');
      return { success: true, message: `成功在第 ${startLine}~${endLine} 行完成代码原子替换。` };
    }
 
    // 2. 全局模式：要求全局唯一
    const occurrences = fileText.split(targetContent).length - 1;
    if (occurrences === 0) {
      // 可选扩展：在这里触发模糊匹配（例如去除前后空行或忽略尾部空格）
      return {
        success: false,
        message: `在整篇文件中未找到匹配的 targetContent，请确认是否有未注意的换行或缩进差异。`,
      };
    }
    if (occurrences > 1) {
      return {
        success: false,
        message: `目标代码在文件中出现了 ${occurrences} 次。为防止误伤，请使用 startLine/endLine 限定区间，或在 targetContent 中包含更多外层代码。`,
      };
    }
 
    // 唯一匹配，安全替换
    const newContent = fileText.replace(targetContent, replacementContent);
    await fs.writeFile(filePath, newContent, 'utf-8');
    return { success: true, message: `成功完成文件唯一代码锚点替换。` };
  }
}