import brotliInit, { compress, decompress } from "./vendor/brotli_wasm.js";
import base from "./vendor/base-x.js";

const COMPRESS_WAIT = 500;
const ENCODER = new TextEncoder();
const DECODER = new TextDecoder();
const BASE66 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~";
const BASE66CODEC = base(BASE66);
const QUALITY = 11;
const MAX_URL = 2048;

let brotli;
let compressTimeout = null;
let rootURLSize = 0;

/**
 * Returns a promise that is resolved when page is loaded enough to run JavaScripts.
 */
function waitForLoad() {
  return new Promise(resolve => {
    // If already loaded, fire immediately
    if (/complete|interactive|loaded/.test(document.readyState)) {
      resolve();
    }
    else {
      document.addEventListener('DOMContentLoaded', resolve);
    }
  });
}

function maxHashLength() {
  if (rootURLSize === 0) {
    const rootURL = new URL(window.location.href);
    rootURL.hash = "";
    rootURLSize = rootURL.toString().length;
  }

  return MAX_URL - rootURLSize - 1;
}

async function init() {
  brotli = await brotliInit();

  const codeEl = document.getElementById("code");
  const lengthEl = document.getElementById("length");

  codeEl.addEventListener("input", () => {
    if (compressTimeout) {
      clearTimeout(compressTimeout);
    }

    if (codeEl.value === "") {
      history.replaceState(null, "", "#");
      lengthEl.textContent = "Waiting...";
      return;
    }

    compressTimeout = setTimeout(async () => {
      const content = codeEl.value;
      const compressed = compress(ENCODER.encode(content), { quality: QUALITY });
      const encoded = BASE66CODEC.encode(compressed);

      lengthEl.textContent = `Length: ${content.length} chars -> ${compressed.length} bytes -> ${encoded.length}/${maxHashLength()} chars`;

      if (encoded.length <= maxHashLength()) {
        history.replaceState(null, "", `#${encoded}`);
      } else {
        lengthEl.textContent += " (TOO BIG!)";
      }
    }, COMPRESS_WAIT);
  });

  if (window.location.hash.length > 1) {
    try {
      const bytes = BASE66CODEC.decode(window.location.hash.substring(1));
      const decompressed = decompress(bytes);
      const content = DECODER.decode(decompressed);
      codeEl.textContent = content;
    } catch (e) {
      codeEl.textContent = e.stack;
    }
  }
}

await waitForLoad();
await init();