stack/apps/gateway/src/agent/tools/git-tools.ts

import { Type } from '@sinclair/typebox';
import type { ToolDefinition } from '@mariozechner/pi-coding-agent';
import { exec } from 'node:child_process';
import { promisify } from 'node:util';
import { resolve, relative } from 'node:path';

const execAsync = promisify(exec);

const GIT_TIMEOUT_MS = 15_000;
const MAX_OUTPUT_BYTES = 100 * 1024; // 100 KB

/**
 * Clamp a user-supplied cwd to within the sandbox directory.
 * If the resolved path escapes the sandbox (via ../ or absolute path outside),
 * falls back to the sandbox directory itself.
 */
function clampCwd(sandboxDir: string, requestedCwd?: string): string {
  if (!requestedCwd) return sandboxDir;
  const resolved = resolve(sandboxDir, requestedCwd);
  const rel = relative(sandboxDir, resolved);
  if (rel.startsWith('..') || rel.startsWith('/')) {
    // Escape attempt — fall back to sandbox root
    return sandboxDir;
  }
  return resolved;
}

async function runGit(
  args: string[],
  cwd?: string,
): Promise<{ stdout: string; stderr: string; error?: string }> {
  // Only allow specific safe read-only git subcommands
  const allowedSubcommands = ['status', 'log', 'diff', 'show', 'branch', 'tag', 'ls-files'];
  const subcommand = args[0];
  if (!subcommand || !allowedSubcommands.includes(subcommand)) {
    return {
      stdout: '',
      stderr: '',
      error: `Blocked: git subcommand "${subcommand}" is not allowed. Permitted: ${allowedSubcommands.join(', ')}`,
    };
  }

  const cmd = `git ${args.map((a) => JSON.stringify(a)).join(' ')}`;
  try {
    const { stdout, stderr } = await execAsync(cmd, {
      cwd,
      timeout: GIT_TIMEOUT_MS,
      maxBuffer: MAX_OUTPUT_BYTES,
    });
    return { stdout, stderr };
  } catch (err: unknown) {
    const e = err as { stdout?: string; stderr?: string; message?: string };
    return {
      stdout: e.stdout ?? '',
      stderr: e.stderr ?? '',
      error: e.message ?? String(err),
    };
  }
}

export function createGitTools(sandboxDir?: string): ToolDefinition[] {
  const defaultCwd = sandboxDir ?? process.cwd();

  const gitStatus: ToolDefinition = {
    name: 'git_status',
    label: 'Git Status',
    description: 'Show the working tree status (staged, unstaged, untracked files).',
    parameters: Type.Object({
      cwd: Type.Optional(
        Type.String({
          description: 'Repository working directory (relative to sandbox or absolute within it).',
        }),
      ),
    }),
    async execute(_toolCallId, params) {
      const { cwd } = params as { cwd?: string };
      const safeCwd = clampCwd(defaultCwd, cwd);
      const result = await runGit(['status', '--short', '--branch'], safeCwd);
      const text = result.error
        ? `Error: ${result.error}\n${result.stderr}`
        : result.stdout || '(no output)';
      return {
        content: [{ type: 'text' as const, text: text }],
        details: undefined,
      };
    },
  };

  const gitLog: ToolDefinition = {
    name: 'git_log',
    label: 'Git Log',
    description: 'Show recent commit history.',
    parameters: Type.Object({
      limit: Type.Optional(Type.Number({ description: 'Number of commits to show (default 20)' })),
      oneline: Type.Optional(
        Type.Boolean({ description: 'Compact one-line format (default true)' }),
      ),
      cwd: Type.Optional(
        Type.String({
          description: 'Repository working directory (relative to sandbox or absolute within it).',
        }),
      ),
    }),
    async execute(_toolCallId, params) {
      const { limit, oneline, cwd } = params as {
        limit?: number;
        oneline?: boolean;
        cwd?: string;
      };
      const safeCwd = clampCwd(defaultCwd, cwd);
      const args = ['log', `--max-count=${limit ?? 20}`];
      if (oneline !== false) args.push('--oneline');
      const result = await runGit(args, safeCwd);
      const text = result.error
        ? `Error: ${result.error}\n${result.stderr}`
        : result.stdout || '(no commits)';
      return {
        content: [{ type: 'text' as const, text: text }],
        details: undefined,
      };
    },
  };

  const gitDiff: ToolDefinition = {
    name: 'git_diff',
    label: 'Git Diff',
    description: 'Show changes between commits, working tree, or staged changes.',
    parameters: Type.Object({
      staged: Type.Optional(
        Type.Boolean({ description: 'Show staged (cached) changes instead of unstaged' }),
      ),
      ref: Type.Optional(
        Type.String({ description: 'Compare against this ref (commit SHA, branch, or tag)' }),
      ),
      path: Type.Optional(
        Type.String({ description: 'Limit diff to a specific file or directory' }),
      ),
      cwd: Type.Optional(
        Type.String({
          description: 'Repository working directory (relative to sandbox or absolute within it).',
        }),
      ),
    }),
    async execute(_toolCallId, params) {
      const { staged, ref, path, cwd } = params as {
        staged?: boolean;
        ref?: string;
        path?: string;
        cwd?: string;
      };
      const safeCwd = clampCwd(defaultCwd, cwd);
      const args = ['diff'];
      if (staged) args.push('--cached');
      if (ref) args.push(ref);
      args.push('--');
      if (path) args.push(path);
      const result = await runGit(args, safeCwd);
      const text = result.error
        ? `Error: ${result.error}\n${result.stderr}`
        : result.stdout || '(no diff)';
      return {
        content: [{ type: 'text' as const, text: text }],
        details: undefined,
      };
    },
  };

  return [gitStatus, gitLog, gitDiff];
}