co-mono/packages/coding-agent/src/tools/bash.ts

import { randomBytes } from "node:crypto";
import { createWriteStream, existsSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import type { AgentTool } from "@mariozechner/pi-ai";
import { Type } from "@sinclair/typebox";
import { spawn, spawnSync } from "child_process";
import { SettingsManager } from "../settings-manager.js";
import { DEFAULT_MAX_BYTES, DEFAULT_MAX_LINES, type TruncationResult, truncateTail } from "./truncate.js";

let cachedShellConfig: { shell: string; args: string[] } | null = null;

/**
 * Find bash executable on PATH (Windows)
 */
function findBashOnPath(): string | null {
	try {
		const result = spawnSync("where", ["bash.exe"], { encoding: "utf-8", timeout: 5000 });
		if (result.status === 0 && result.stdout) {
			const firstMatch = result.stdout.trim().split(/\r?\n/)[0];
			if (firstMatch && existsSync(firstMatch)) {
				return firstMatch;
			}
		}
	} catch {
		// Ignore errors
	}
	return null;
}

/**
 * Get shell configuration based on platform.
 * Resolution order:
 * 1. User-specified shellPath in settings.json
 * 2. On Windows: Git Bash in known locations
 * 3. Fallback: bash on PATH (Windows) or sh (Unix)
 */
function getShellConfig(): { shell: string; args: string[] } {
	if (cachedShellConfig) {
		return cachedShellConfig;
	}

	const settings = new SettingsManager();
	const customShellPath = settings.getShellPath();

	// 1. Check user-specified shell path
	if (customShellPath) {
		if (existsSync(customShellPath)) {
			cachedShellConfig = { shell: customShellPath, args: ["-c"] };
			return cachedShellConfig;
		}
		throw new Error(
			`Custom shell path not found: ${customShellPath}\n` + `Please update shellPath in ~/.pi/agent/settings.json`,
		);
	}

	if (process.platform === "win32") {
		// 2. Try Git Bash in known locations
		const paths: string[] = [];
		const programFiles = process.env.ProgramFiles;
		if (programFiles) {
			paths.push(`${programFiles}\\Git\\bin\\bash.exe`);
		}
		const programFilesX86 = process.env["ProgramFiles(x86)"];
		if (programFilesX86) {
			paths.push(`${programFilesX86}\\Git\\bin\\bash.exe`);
		}

		for (const path of paths) {
			if (existsSync(path)) {
				cachedShellConfig = { shell: path, args: ["-c"] };
				return cachedShellConfig;
			}
		}

		// 3. Fallback: search bash.exe on PATH (Cygwin, MSYS2, WSL, etc.)
		const bashOnPath = findBashOnPath();
		if (bashOnPath) {
			cachedShellConfig = { shell: bashOnPath, args: ["-c"] };
			return cachedShellConfig;
		}

		throw new Error(
			`No bash shell found. Options:\n` +
				`  1. Install Git for Windows: https://git-scm.com/download/win\n` +
				`  2. Add your bash to PATH (Cygwin, MSYS2, etc.)\n` +
				`  3. Set shellPath in ~/.pi/agent/settings.json\n\n` +
				`Searched Git Bash in:\n${paths.map((p) => `  ${p}`).join("\n")}`,
		);
	}

	cachedShellConfig = { shell: "sh", args: ["-c"] };
	return cachedShellConfig;
}

/**
 * Kill a process and all its children
 */
function killProcessTree(pid: number): void {
	if (process.platform === "win32") {
		// Use taskkill on Windows to kill process tree
		try {
			spawn("taskkill", ["/F", "/T", "/PID", String(pid)], {
				stdio: "ignore",
				detached: true,
			});
		} catch (e) {
			// Ignore errors if taskkill fails
		}
	} else {
		// Use SIGKILL on Unix/Linux/Mac
		try {
			process.kill(-pid, "SIGKILL");
		} catch (e) {
			// Fallback to killing just the child if process group kill fails
			try {
				process.kill(pid, "SIGKILL");
			} catch (e2) {
				// Process already dead
			}
		}
	}
}

/**
 * Generate a unique temp file path for bash output
 */
function getTempFilePath(): string {
	const id = randomBytes(8).toString("hex");
	return join(tmpdir(), `pi-bash-${id}.log`);
}

const bashSchema = Type.Object({
	command: Type.String({ description: "Bash command to execute" }),
	timeout: Type.Optional(Type.Number({ description: "Timeout in seconds (optional, no default timeout)" })),
});

interface BashToolDetails {
	truncation?: TruncationResult;
	fullOutputPath?: string;
}

export const bashTool: AgentTool<typeof bashSchema> = {
	name: "bash",
	label: "bash",
	description: `Execute a bash command in the current working directory. Returns stdout and stderr. Output is truncated to last ${DEFAULT_MAX_LINES} lines or ${DEFAULT_MAX_BYTES / 1024}KB (whichever is hit first). If truncated, full output is saved to a temp file. Optionally provide a timeout in seconds.`,
	parameters: bashSchema,
	execute: async (
		_toolCallId: string,
		{ command, timeout }: { command: string; timeout?: number },
		signal?: AbortSignal,
	) => {
		return new Promise((resolve, reject) => {
			const { shell, args } = getShellConfig();
			const child = spawn(shell, [...args, command], {
				detached: true,
				stdio: ["ignore", "pipe", "pipe"],
			});

			// We'll stream to a temp file if output gets large
			let tempFilePath: string | undefined;
			let tempFileStream: ReturnType<typeof createWriteStream> | undefined;
			let totalBytes = 0;

			// Keep a rolling buffer of the last chunk for tail truncation
			const chunks: Buffer[] = [];
			let chunksBytes = 0;
			// Keep more than we need so we have enough for truncation
			const maxChunksBytes = DEFAULT_MAX_BYTES * 2;

			let timedOut = false;

			// Set timeout if provided
			let timeoutHandle: NodeJS.Timeout | undefined;
			if (timeout !== undefined && timeout > 0) {
				timeoutHandle = setTimeout(() => {
					timedOut = true;
					onAbort();
				}, timeout * 1000);
			}

			const handleData = (data: Buffer) => {
				totalBytes += data.length;

				// Start writing to temp file once we exceed the threshold
				if (totalBytes > DEFAULT_MAX_BYTES && !tempFilePath) {
					tempFilePath = getTempFilePath();
					tempFileStream = createWriteStream(tempFilePath);
					// Write all buffered chunks to the file
					for (const chunk of chunks) {
						tempFileStream.write(chunk);
					}
				}

				// Write to temp file if we have one
				if (tempFileStream) {
					tempFileStream.write(data);
				}

				// Keep rolling buffer of recent data
				chunks.push(data);
				chunksBytes += data.length;

				// Trim old chunks if buffer is too large
				while (chunksBytes > maxChunksBytes && chunks.length > 1) {
					const removed = chunks.shift()!;
					chunksBytes -= removed.length;
				}
			};

			// Collect stdout and stderr together
			if (child.stdout) {
				child.stdout.on("data", handleData);
			}
			if (child.stderr) {
				child.stderr.on("data", handleData);
			}

			// Handle process exit
			child.on("close", (code) => {
				if (timeoutHandle) {
					clearTimeout(timeoutHandle);
				}
				if (signal) {
					signal.removeEventListener("abort", onAbort);
				}

				// Close temp file stream
				if (tempFileStream) {
					tempFileStream.end();
				}

				// Combine all buffered chunks
				const fullBuffer = Buffer.concat(chunks);
				const fullOutput = fullBuffer.toString("utf-8");

				if (signal?.aborted) {
					let output = fullOutput;
					if (output) output += "\n\n";
					output += "Command aborted";
					reject(new Error(output));
					return;
				}

				if (timedOut) {
					let output = fullOutput;
					if (output) output += "\n\n";
					output += `Command timed out after ${timeout} seconds`;
					reject(new Error(output));
					return;
				}

				// Apply tail truncation
				const truncation = truncateTail(fullOutput);
				let outputText = truncation.content || "(no output)";

				// Build details with truncation info
				let details: BashToolDetails | undefined;
				if (truncation.truncated) {
					details = {
						truncation,
						fullOutputPath: tempFilePath,
					};
				}

				if (code !== 0 && code !== null) {
					outputText += `\n\nCommand exited with code ${code}`;
					reject(new Error(outputText));
				} else {
					resolve({ content: [{ type: "text", text: outputText }], details });
				}
			});

			// Handle abort signal - kill entire process tree
			const onAbort = () => {
				if (child.pid) {
					killProcessTree(child.pid);
				}
			};

			if (signal) {
				if (signal.aborted) {
					onAbort();
				} else {
					signal.addEventListener("abort", onAbort, { once: true });
				}
			}
		});
	},
};