/**
 * Configuration, read once at boot.
 *
 * Everything the process needs to know about its environment resolves here so
 * that a misconfiguration is a startup failure with a sentence attached rather
 * than a puzzling behaviour three screens later.
 */

import { resolve } from "node:path";

export type Config = {
	host: string;
	port: number;
	/** When set, required at the WebSocket upgrade. */
	key: string | undefined;
	/** What the agent is allowed to read. Printed at boot; never inferred later. */
	workingDir: string;
	/** Where room state is written. */
	dataDir: string;
	/** Planner model. */
	model: string;
};

const DEFAULT_PORT = 8787;
const DEFAULT_MODEL = "claude-sonnet-4.6";

function port(): number {
	let raw = process.env.PORT;
	if (!raw) return DEFAULT_PORT;
	let value = Number.parseInt(raw, 10);
	if (!Number.isInteger(value) || value < 1 || value > 65535) {
		throw new Error(`PORT must be a number between 1 and 65535, got ${JSON.stringify(raw)}`);
	}
	return value;
}

export function load(): Config {
	return {
		host: process.env.SERVER_HOST || "127.0.0.1",
		port: port(),
		key: process.env.ACCESS_KEY || undefined,
		workingDir: resolve(process.env.WORKING_DIR || process.cwd()),
		dataDir: resolve(process.env.DATA_DIR || "data"),
		model: process.env.MODEL || DEFAULT_MODEL,
	};
}

/**
 * What the operator needs to see before deciding to trust this process.
 *
 * The working directory is printed because it is the extent of what an agent
 * can read, and defaulting it to the current directory makes it too easy to
 * start one somewhere you did not intend.
 */
export function describe(config: Config): string {
	let parts = [
		"chopin",
		`http://${config.host}:${config.port}`,
		`working dir: ${config.workingDir}`,
	];
	if (config.key) parts.push("access key: required");
	if (config.host !== "127.0.0.1" && config.host !== "localhost" && !config.key) {
		parts.push("WARNING: bound beyond localhost with no ACCESS_KEY");
	}
	return parts.join("  ·  ");
}