import { readFile } from "node:fs/promises";

import { runModule } from "../../javascript/src/run-module/index.js";

export const did = "did:plc:lpfuqerea3deuoyrn7ojser4";
export const now = "2026-11-06T12:34:56.789Z";

/** A build at `url`; with `json` (its module.json's URL), handle() holds it to that file's calls and anyRecords. */
export async function load(url, json) {
	const module = new WebAssembly.Module(await readFile(url));
	const { calls, anyRecords } = json ? JSON.parse(await readFile(json, "utf8")) : {};
	const { exports } = new WebAssembly.Instance(module, {});

	function run(entry, input) {
		const data = new TextEncoder().encode(JSON.stringify(input ?? null));
		const ptr = exports.alloc(data.length);
		new Uint8Array(exports.memory.buffer, ptr, data.length).set(data);
		const packed = BigInt.asUintN(64, exports[entry](ptr, data.length));
		const outPtr = Number(packed >> 32n);
		const outLen = Number(packed & 0xffffffffn);
		return JSON.parse(new TextDecoder().decode(new Uint8Array(exports.memory.buffer, outPtr, outLen)));
	}

	// The real host loop (runModule) over this module, with did and now fixed.
	// respond({ nsid, params, input, proxy, service, subscribe }) returns { ok, output } or { ok: false, error }
	// for a request; for a subscribe, the messages (an array, or any async iterable), after which the
	// subscription closes. Resolves to runModule's result plus sends: [{ nsid, data }] written up subscriptions.
	async function handle(entry, input, { respond, inputs, budget, signal } = {}) {
		const sends = [];
		const ctx = { wasm: { run: async ({ entry, input }) => run(entry, { ...input, now }) } };
		const call = async (nsid, request) => {
			const answer = await respond({ nsid, ...request });
			if (!request.subscribe) {
				if (answer?.ok === false) throw new Error(answer.error ?? "call failed");
				return answer?.output;
			}
			return { [Symbol.asyncIterator]: async function* () { yield* answer; }, send: async (data) => void sends.push({ nsid, data }) };
		};
		const ran = await runModule(ctx, { module, calls, anyRecords }, entry, { did, ...input }, call, { inputs, budget, signal });
		return { ...ran, sends };
	}

	return { module, run, handle };
}