(function () {
  var dialog = document.getElementById("exapp-dialog");
  if (!dialog || dialog.getAttribute("data-ready") === "1") return;
  dialog.setAttribute("data-ready", "1");

  var panel = document.getElementById("exapp-dialog-panel");
  var heading = document.getElementById("exapp-dialog-heading");
  var severity = document.getElementById("exapp-dialog-severity");
  var message = document.getElementById("exapp-dialog-message");
  var field = document.getElementById("exapp-dialog-value");
  var cancelBtn = document.getElementById("exapp-dialog-cancel");
  var agreeBtn = document.getElementById("exapp-dialog-agree");
  var queue = [];
  var busy = false;
  var finish = null;

  function textOf(value) {
    return value == null ? "" : String(value);
  }

  function trimmed() {
    return field.value.trim();
  }

  function refreshAgree() {
    agreeBtn.disabled = !field.hidden && trimmed() === "";
  }

  function settle(result) {
    var done = finish;
    finish = null;
    if (dialog.open) dialog.close();
    busy = false;
    if (done) done(result);
    pump();
  }

  function decline() {
    if (!finish) return;
    var kind = dialog.getAttribute("data-kind");
    if (kind === "confirm") settle(false);
    else if (kind === "prompt") settle(null);
    else settle(undefined);
  }

  function agree() {
    if (!finish || agreeBtn.disabled) return;
    var kind = dialog.getAttribute("data-kind");
    if (kind === "confirm") settle(true);
    else if (kind === "prompt") settle(trimmed());
    else settle(undefined);
  }

  cancelBtn.addEventListener("click", function (e) {
    e.stopPropagation();
    decline();
  });
  agreeBtn.addEventListener("click", function (e) {
    e.stopPropagation();
    agree();
  });
  field.addEventListener("input", refreshAgree);
  dialog.addEventListener("cancel", function (e) {
    e.preventDefault();
    decline();
  });
  dialog.addEventListener("click", function (e) {
    if (e.target === dialog) decline();
  });
  dialog.addEventListener("keydown", function (e) {
    if (e.key !== "Enter") return;
    e.preventDefault();
    agree();
  });
  panel.addEventListener("click", function (e) {
    e.stopPropagation();
  });

  function show(kind, opts, done) {
    opts = opts || {};
    finish = done;
    dialog.setAttribute("data-kind", kind);
    var head = textOf(opts.heading);
    heading.textContent = head;
    heading.hidden = head === "";
    message.textContent = textOf(opts.text);
    var sev = "";
    if (kind === "message") {
      sev = opts.severity === "warning" || opts.severity === "error" ? opts.severity : "info";
      dialog.setAttribute("data-severity", sev);
    } else {
      dialog.removeAttribute("data-severity");
    }
    severity.textContent = sev;
    severity.hidden = sev === "";
    var isPrompt = kind === "prompt";
    field.hidden = !isPrompt;
    field.value = isPrompt ? textOf(opts.value) : "";
    cancelBtn.hidden = kind === "message";
    agreeBtn.textContent = kind !== "message" && opts.agree ? textOf(opts.agree) : "OK";
    agreeBtn.classList.toggle("destructive", kind === "confirm" && !!opts.destructive);
    refreshAgree();
    if (!dialog.open) dialog.showModal();
    if (isPrompt) field.focus();
    else if (!agreeBtn.disabled) agreeBtn.focus();
  }

  function pump() {
    if (busy || queue.length === 0) return;
    busy = true;
    queue.shift()();
  }

  function enqueue(kind, opts) {
    return new Promise(function (resolve) {
      queue.push(function () {
        show(kind, opts, resolve);
      });
      pump();
    });
  }

  window.exappDialog = {
    message: function (opts) { return enqueue("message", opts); },
    confirm: function (opts) { return enqueue("confirm", opts); },
    prompt: function (opts) { return enqueue("prompt", opts); }
  };
})();