/**
 * LLM Redaction Extension
 *
 * WHAT: Before each provider request, redacts secrets from the outbound
 *       payload so tokens/keys never leave the machine in a prompt. Uses the
 *       `before_provider_request` hook and returns a modified payload.
 *
 * CONFIGURE: secret patterns live in extensions/lib/secrets.ts.
 *
 * DISABLE: remove/rename this file from the package `extensions/` folder.
 */

import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
import { redact } from "./lib/secrets.ts";
import { audit } from "./lib/audit.ts";

/** Recursively redact secrets in every string within a JSON-like value. */
function redactDeep(value: unknown, counter: { n: number }): unknown {
	if (typeof value === "string") {
		const cleaned = redact(value);
		if (cleaned !== value) counter.n++;
		return cleaned;
	}
	if (Array.isArray(value)) return value.map((v) => redactDeep(v, counter));
	if (value && typeof value === "object") {
		const out: Record<string, unknown> = {};
		for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
			out[k] = redactDeep(v, counter);
		}
		return out;
	}
	return value;
}

export default function llmRedactionExtension(pi: ExtensionAPI) {
	pi.on("before_provider_request", async (event) => {
		const payload = event.payload;
		if (!payload) return undefined;

		const counter = { n: 0 };
		// Only rewrite the message content to avoid disturbing payload metadata.
		const messages = (payload as { messages?: unknown }).messages;
		if (messages === undefined) return undefined;

		const redactedMessages = redactDeep(messages, counter);
		if (counter.n === 0) return undefined;

		audit({ kind: "redaction", occurrences: counter.n });
		return { ...payload, messages: redactedMessages };
	});
}