import type { App } from "../core/app.ts";
import { existsSync } from "node:fs";
import { writeFile } from "node:fs/promises";
import { join, resolve } from "node:path";

export interface WorkerEnv {
	[key: string]: unknown;
}

export interface WorkerContext {
	waitUntil(promise: Promise<unknown>): void;
	passThroughOnException?(): void;
}

export interface WorkerOptions {
	/** Builds the application from the bindings of the worker. */
	create?: (env: WorkerEnv) => App | Promise<App>;
}

export interface WranglerSetupOptions {
	name?: string;
	main?: string;
	compatibilityDate?: string;
}

/** Creates a minimal Wrangler config when a project has not supplied one. */
export async function setupWrangler(root: string, options: WranglerSetupOptions = {}): Promise<string> {
	const path = join(resolve(root), "wrangler.jsonc");
	if (existsSync(path)) return path;
	const source = JSON.stringify({ name: options.name ?? "muddle-app", main: options.main ?? "src/worker.ts", compatibility_date: options.compatibilityDate ?? "2026-10-22" }, null, 2).concat("\n");
	await writeFile(path, source, "utf8");
	return path;
}

/** Creates the fetch handler of a worker. */
export function createWorker(app: App | WorkerOptions["create"]): {
	fetch(
		request: Request,
		env: WorkerEnv,
		ctx: WorkerContext,
	): Promise<Response>;
} {
	let instance: App | undefined = typeof app === "function" ? undefined : app;

	return {
		async fetch(request: Request, env: WorkerEnv, _ctx: WorkerContext) {
			if (!instance) {
				instance = await (app as (env: WorkerEnv) => Promise<App>)(env);
			}
			return instance.fetch(request);
		},
	};
}