import { onDestroy } from "../lib/skeleton/index.js";

export async function loadJS(baseURL, path, opts = {}) {
    const $script = document.createElement("script");
    const link = new URL(path, baseURL);
    $script.setAttribute("src", link.toString());
    for (const key in opts) {
        $script.setAttribute(key, opts[key]);
    }
    if (document.head.querySelector(`[src="${link.toString()}"]`)) return Promise.resolve();
    document.head.appendChild($script);
    return new Promise((done) => {
        $script.onload = () => done();
        $script.onerror = () => done();
    });
}

export async function loadCSS(baseURL, path) {
    const $style = document.createElement("link");
    const link = new URL(path, baseURL);
    $style.setAttribute("href", link.toString());
    $style.setAttribute("rel", "stylesheet");
    if (document.head.querySelector(`[href="${link.toString()}"]`)) return Promise.resolve();
    document.head.appendChild($style);
    return new Promise((done) => {
        $style.onload = done;
        $style.onerror = done;
    });
}

export async function loadWorker(baseURL, path, opts = {}) {
    const { iframe = true } = opts;
    let url = new URL(path, baseURL);
    if (iframe) {
        // eg: fix issue coming from loading worker through an iframe like this nasty:
        //     SecurityError: Failed to construct 'Worker': Script at 'xxx.worker.js' cannot be accessed from origin 'null'.
        //        at Module.default (loader_dbf.js:9:20)
        //        at application_table.js:58:50
        let code = await fetch(new URL(path, baseURL)).then((res) => res.text());
        const importPathRE = new RegExp("import\\s+(?:[^'\";]*?\\s+from\\s+)?[\"']([^\"']+)[\"']", "gm");
        code = code.replaceAll("import.meta.url", `"${baseURL}"`);
        code.matchAll(importPathRE).forEach(([_, path]) => {
            code = code.replaceAll(path, new URL(path, baseURL));
        });
        url = URL.createObjectURL(new Blob([code], { type: "application/javascript" }));
        onDestroy(() => URL.revokeObjectURL(url));
    }
    const worker = new Worker(url, { type: "module" });
    onDestroy(() => worker.terminate());
    await new Promise((resolve) => worker.addEventListener(
        "message", resolve, { once: true },
    ));
    return worker;
}

export async function loadCSSInline(baseURL, filename) {
    const res = await fetch(new URL(filename, baseURL).pathname, {
        cache: "force-cache",
    });
    if (res.status !== 200) return `/* ERROR: ${res.status} */`;
    else if (!res.headers.get("Content-Type")?.startsWith("text/css")) return `/* ERROR: wrong type, got "${res.headers?.get("Content-Type")}"*/`;
    return await res.text();
}

export async function CSS(baseURL, ...arrayOfFilenames) {
    const sheets = await Promise.all(arrayOfFilenames.map((filename) => loadCSSInline(baseURL, filename)));
    return sheets.join("\n\n");
}