/**
 * 文件编辑工具（1 个）
 *
 * file_editor — 精准文件编辑，支持行替换/插入/删除/正则替换
 *
 * 相比 write_file 的整文件覆盖，file_editor 支持精准定位修改，
 * 避免大文件全量重写，减少 token 消耗和出错风险。
 *
 * @see docs/MetonaAI-Desktop 架构与交互设计.html — 9 个基础工具
 */

import { readFile, writeFile, rename, mkdir } from 'fs/promises';
import { dirname } from 'path';
import { existsSync } from 'fs';
import type { IMetonaTool, ToolExecutionContext } from '../../types/metona-tool';
import type { MetonaToolDef } from '../../../harness/types';
import { MetonaToolCategory, MetonaRiskLevel } from '../../../harness/types';
import { isProtectedWorkspaceFile, isPathWithinWorkspace } from './file-guard';
import { resolve } from 'path';

/** 安全校验：路径遍历防护 + 受保护文件拦截 */
function safeResolvePath(filePath: string, workspacePath: string): string {
  const resolved = resolve(workspacePath, filePath);
  if (!isPathWithinWorkspace(filePath, workspacePath)) {
    throw new Error(`Path traversal detected: ${filePath}`);
  }
  if (isProtectedWorkspaceFile(filePath, workspacePath)) {
    throw new Error('Access denied: MEMORY.md is managed by the memory system and cannot be accessed via file tools');
  }
  return resolved;
}

export class FileEditorTool implements IMetonaTool {
  readonly definition: MetonaToolDef = {
    name: 'file_editor',
    description: 'Edit a file with precision. Supports operations: replace (replace lines), insert (insert at line), delete (delete lines), regex (regex replace in range). More efficient than write_file for targeted edits.',
    parameters: {
      type: 'object',
      properties: {
        file_path: { type: 'string', description: 'Path to the file to edit' },
        operation: {
          type: 'string',
          description: 'Edit operation',
          enum: ['replace', 'insert', 'delete', 'regex'],
        },
        start_line: { type: 'number', description: 'Start line number (1-indexed). Used by replace/insert/delete/regex' },
        end_line: { type: 'number', description: 'End line number (inclusive). Used by replace/delete' },
        content: { type: 'string', description: 'New content for replace/insert operations' },
        pattern: { type: 'string', description: 'Regex pattern for regex operation' },
        replacement: { type: 'string', description: 'Replacement string for regex operation' },
        flags: { type: 'string', description: 'Regex flags (default "g")' },
      },
      required: ['file_path', 'operation'],
    },
    category: MetonaToolCategory.FILESYSTEM,
    riskLevel: MetonaRiskLevel.MEDIUM,
    requiresPermission: true,
    timeoutMs: 15_000,
  };

  async execute(args: Record<string, unknown>, context: ToolExecutionContext): Promise<unknown> {
    try {
      // F1.5: file_path 空值校验
      if (!args.file_path || typeof args.file_path !== 'string') {
        return { success: false, error: 'file_path is required' };
      }
      const filePath = safeResolvePath(args.file_path as string, context.workspacePath);
      const operation = args.operation as 'replace' | 'insert' | 'delete' | 'regex';

      // 文件必须存在（不支持创建新文件，请用 write_file）
      if (!existsSync(filePath)) {
        return { success: false, error: `File not found: ${args.file_path}. Use write_file to create new files.` };
      }

      const originalContent = await readFile(filePath, 'utf-8');
      const lines = originalContent.split('\n');

      let newLines: string[];
      let affectedRange: { start: number; end: number };

      switch (operation) {
        case 'replace': {
          const startLine = Math.max(1, (args.start_line as number) ?? 1);
          const endLine = Math.min(lines.length, (args.end_line as number) ?? startLine);
          if (endLine < startLine) {
            return { success: false, error: `end_line (${endLine}) must be >= start_line (${startLine})` };
          }
          const content = (args.content as string) ?? '';
          const contentLines = content.split('\n');
          newLines = [
            ...lines.slice(0, startLine - 1),
            ...contentLines,
            ...lines.slice(endLine),
          ];
          affectedRange = { start: startLine, end: endLine };
          break;
        }

        case 'insert': {
          let startLine = Math.max(1, (args.start_line as number) ?? 1);
          startLine = Math.min(startLine, lines.length + 1);  // 允许追加到末尾
          const content = (args.content as string) ?? '';
          const contentLines = content.split('\n');
          newLines = [
            ...lines.slice(0, startLine - 1),
            ...contentLines,
            ...lines.slice(startLine - 1),
          ];
          affectedRange = { start: startLine, end: startLine + contentLines.length - 1 };
          break;
        }

        case 'delete': {
          const startLine = Math.max(1, (args.start_line as number) ?? 1);
          const endLine = Math.min(lines.length, (args.end_line as number) ?? startLine);
          if (endLine < startLine) {
            return { success: false, error: `end_line (${endLine}) must be >= start_line (${startLine})` };
          }
          newLines = [
            ...lines.slice(0, startLine - 1),
            ...lines.slice(endLine),
          ];
          affectedRange = { start: startLine, end: endLine };
          break;
        }

        case 'regex': {
          const pattern = args.pattern as string;
          const replacement = (args.replacement as string) ?? '';
          const flags = (args.flags as string) ?? 'g';
          if (!pattern) {
            return { success: false, error: 'Regex operation requires "pattern" parameter' };
          }
          // F1.3: regex pattern 长度限制
          if (pattern.length > 500) {
            return { success: false, error: 'Regex pattern too long (max 500 chars)' };
          }
          const startLine = Math.max(1, (args.start_line as number) ?? 1);
          const endLine = Math.min(lines.length, (args.end_line as number) ?? lines.length);
          if (endLine < startLine) {
            return { success: false, error: `end_line (${endLine}) must be >= start_line (${startLine})` };
          }

          let regex: RegExp;
          try {
            regex = new RegExp(pattern, flags);
          } catch (err) {
            return { success: false, error: `Invalid regex: ${(err as Error).message}` };
          }

          // F1.4: 用带 g 标志的正则统计匹配数
          let replaceCount = 0;
          const targetLines = lines.slice(startLine - 1, endLine);
          const countRegex = new RegExp(pattern, flags.includes('g') ? flags : flags + 'g');
          const replacedLines = targetLines.map((line) => {
            const matches = line.match(countRegex);
            if (matches) replaceCount += matches.length;
            return line.replace(regex, replacement);
          });

          newLines = [
            ...lines.slice(0, startLine - 1),
            ...replacedLines,
            ...lines.slice(endLine),
          ];
          affectedRange = { start: startLine, end: endLine };

          // 如果没有替换，返回提示
          if (replaceCount === 0) {
            return {
              success: true,
              operation,
              file_path: args.file_path,
              message: 'No matches found for regex pattern',
              replacements: 0,
              affected_range: affectedRange,
            };
          }

          break;
        }

        default:
          return { success: false, error: `Unknown operation: ${operation}` };
      }

      // 自动创建父目录 (F1.8: 异步 mkdir)
      const parentDir = dirname(filePath);
      if (!existsSync(parentDir)) {
        await mkdir(parentDir, { recursive: true });
      }

      const newContent = newLines.join('\n');
      // F1.7: 原子写入 - 临时文件 + rename
      const tmpPath = `${filePath}.tmp_${Date.now()}`;
      await writeFile(tmpPath, newContent, 'utf-8');
      await rename(tmpPath, filePath);

      return {
        success: true,
        operation,
        file_path: args.file_path,
        affected_range: affectedRange,
        lines_before: lines.length,
        lines_after: newLines.length,
        bytes_written: Buffer.byteLength(newContent, 'utf-8'),
      };
    } catch (err) {
      return { success: false, error: (err as Error).message };
    }
  }
}