import { VertFile } from "$lib/types";
import { Converter } from "./converter.svelte";
import { browser } from "$app/environment";
import PandocWorker from "$lib/workers/pandoc?worker";

export class PandocConverter extends Converter {
	public name = "pandoc";
	public ready = $state(false);
	public wasm: ArrayBuffer = null!;

	constructor() {
		super();
		if (!browser) return;
		(async () => {
			this.wasm = await fetch("/pandoc.wasm").then((r) =>
				r.arrayBuffer(),
			);
			this.ready = true;
		})();
	}

	public async convert(input: VertFile, to: string): Promise<VertFile> {
		const worker = new PandocWorker();
		worker.postMessage({ type: "load", wasm: this.wasm });
		await waitForMessage(worker, "loaded");
		worker.postMessage({
			type: "convert",
			to,
			file: input.file,
		});
		const result = await waitForMessage(worker);
		if (result.type === "error") {
			worker.terminate();
			// throw new Error(result.error);
			switch (result.errorKind) {
				case "PandocUnknownReaderError": {
					throw new Error(
						`${input.from} is not a supported input format for documents.`,
					);
				}

				case "PandocUnknownWriterError": {
					throw new Error(
						`${to} is not a supported output format for documents.`,
					);
				}

				default:
					if (result.errorKind)
						throw new Error(
							`[${result.errorKind}] ${result.error}`,
						);
					else throw new Error(result.error);
			}
		}
		worker.terminate();
		if (!to.startsWith(".")) to = `.${to}`;
		return new VertFile(new File([result.output], input.name), to);
	}

	// public name = "pandoc";
	// public ready = $state(false);
	// public wasm: ArrayBuffer = null!;

	public supportedFormats = [
		".docx",
		".doc",
		".md",
		".html",
		".rtf",
		".csv",
		".tsv",
		".json",
		".rst",
		".epub",
		".odt",
		".docbook",
	];
}

// eslint-disable-next-line @typescript-eslint/no-explicit-any
function waitForMessage(worker: Worker, type?: string): Promise<any> {
	return new Promise((resolve) => {
		const onMessage = (e: MessageEvent) => {
			if (type && e.data.type === type) {
				worker.removeEventListener("message", onMessage);
				resolve(e.data);
			} else {
				worker.removeEventListener("message", onMessage);
				resolve(e.data);
			}
		};
		worker.addEventListener("message", onMessage);
	});
}