review gate for pi

review-gate.ts

/**
 * Review Gate Extension
 *
 * Toggle with /review-gate. When active, intercepts edit/write tool calls:
 * writes /tmp/review-a, /tmp/review-b, and /tmp/proposed.diff, then prompts
 * inside pi. Empty input = approve, text = block with reason.
 */

import type { ExtensionAPI, EditToolCallEvent, WriteToolCallEvent } from "@mariozechner/pi-coding-agent";
import { readFile, writeFile } from "fs/promises";
import { resolve } from "path";

export default function (pi: ExtensionAPI) {
	let enabled = true;

	pi.registerCommand("review-gate", {
		description: "Toggle review gate for edit/write tools",
		handler: async (_args, ctx) => {
			enabled = !enabled;
			ctx.ui.notify(`Review gate ${enabled ? "on" : "off"}`, "info");
		},
	});

	pi.on("tool_call", async (event, ctx) => {
		if (!enabled) return undefined;
		if (event.toolName !== "edit" && event.toolName !== "write") return undefined;
		if (!ctx.hasUI) return undefined;

		const path = resolve(ctx.cwd, event.input.path as string);

		let a: string;
		let b: string;

		if (event.toolName === "edit") {
			const input = event.input as EditToolCallEvent["input"];
			a = input.oldText;
			b = input.newText;
		} else {
			const input = event.input as WriteToolCallEvent["input"];
			try {
				a = await readFile(path, "utf-8");
			} catch {
				a = "";
			}
			b = input.content;
		}

		await writeFile("/tmp/review-a", a);
		await writeFile("/tmp/review-b", b);

		const label = event.input.path as string;
		const diff = await pi.exec("diff", [
			"-u",
			"--label",
			`a/${label}`,
			"--label",
			`b/${label}`,
			"/tmp/review-a",
			"/tmp/review-b",
		]);
		const diffText = diff.stdout || "(no differences)\n";
		await writeFile("/tmp/proposed.diff", diffText);

		const response = await ctx.ui.input(`${event.toolName} ${label}`);

		if (response === undefined) {
			return { block: true, reason: "Review cancelled" };
		}
		if (response.trim() === "") return undefined;
		return { block: true, reason: response.trim() };
	});
}