// The converter form: sends the address to /api/convert (rekopub-web) and
// shows the download links on this page. Without this script the form still
// works, and the server answers with a page of its own.
(function () {
  "use strict";
  var form = document.getElementById("convert-form");
  var fields = document.getElementById("convert-fields");
  var result = document.getElementById("convert-result");
  var keepHours = document.getElementById("keep-hours");
  var button = form.querySelector("button");
  if (!window.fetch || !window.URLSearchParams) return;

  function el(tag, attrs, text) {
    var node = document.createElement(tag);
    for (var k in attrs) node.setAttribute(k, attrs[k]);
    if (text) node.textContent = text;
    return node;
  }

  function show(nodes) {
    result.replaceChildren.apply(result, nodes);
  }

  function message(text, isError) {
    show([el("p", isError ? { "class": "convert-error" } : {}, text)]);
  }

  function hours(n) {
    return n === 1 ? "1 hour" : n + " hours";
  }

  // pause disables the form while conversions are paused.
  function pause(text) {
    fields.disabled = true;
    message(text, true);
  }

  function size(bytes) {
    return bytes < 1024 * 1024
      ? Math.ceil(bytes / 1024) + " KB"
      : (bytes / 1024 / 1024).toFixed(1) + " MB";
  }

  // The server's reply, or a stand-in when nginx answered instead (a
  // limit, a timeout or the converter being down).
  function readReply(res) {
    return res.json().catch(function () {
      if (res.status === 429) return { error: "Too many requests at once. Please wait a minute and try again." };
      if (res.status === 503) return { error: "The converter is busy. Please try again in a minute." };
      if (res.status === 504) return { error: "That page took too long to convert." };
      return { error: "The converter isn't available right now. Please try again later." };
    });
  }

  fetch("/api/status", { headers: { Accept: "application/json" } })
    .then(readReply)
    .then(function (st) {
      if (st.keepHours) keepHours.textContent = st.keepHours;
      if (st.paused) pause(st.error);
    })
    .catch(function () {});

  form.addEventListener("submit", function (event) {
    event.preventDefault();
    var body = new URLSearchParams(new FormData(form));
    fields.disabled = true;
    button.textContent = "Converting…";
    message("Converting… this can take up to a minute.");
    fetch(form.action, {
      method: "POST",
      headers: { Accept: "application/json" },
      body: body
    })
      .then(readReply)
      .then(function (rep) {
        fields.disabled = false;
        button.textContent = "Convert";
        if (rep.paused) return pause(rep.error);
        if (rep.error) return message(rep.error, true);
        var list = el("ul", { "class": "convert-files" });
        rep.files.forEach(function (f) {
          var li = el("li");
          li.append(el("a", { href: f.url, download: "" }, f.name), " ",
            el("span", { "class": "small" }, f.format + ", " + size(f.size)));
          list.append(li);
        });
        var nodes = [el("p", { "class": "small" }, "Links work for " + hours(rep.keepHours) + "."), list];
        if (rep.warning) nodes.push(el("p", { "class": "convert-error" }, rep.warning));
        show(nodes);
      })
      .catch(function () {
        fields.disabled = false;
        button.textContent = "Convert";
        message("Couldn't reach the converter. Check your connection and try again.", true);
      });
  });
})();