// Everything here is additive: with JavaScript off, the plain multipart POST
// still works.
(function () {
  'use strict';

  // Wired before the form-specific code bails out, because the result page has
  // copy buttons and no form. They ship hidden, so without this there is no
  // dead button.
  function wireCopy() {
    var buttons = document.querySelectorAll('button.copy[data-copy]');
    Array.prototype.forEach.call(buttons, function (button) {
      var target = document.getElementById(button.dataset.copy);
      if (!target) return;
      button.hidden = false;

      var label = button.textContent, timer;
      function say(word) {
        button.textContent = word;
        clearTimeout(timer);
        timer = setTimeout(function () { button.textContent = label; }, 1500);
      }

      // Answers both ways the clipboard API fails us: absent over plain HTTP,
      // where it is not a secure context, and present but refusing. Needs no
      // permission. If it fails too, the text is selected, so say what to press.
      function copySelection() {
        var ok = false;
        try { ok = document.execCommand('copy'); } catch (e) { /* ok stays false */ }
        say(ok ? 'Copied' : 'Press Ctrl-C');
      }

      button.addEventListener('click', function () {
        target.select();
        target.setSelectionRange(0, target.value.length); // iOS ignores select()
        if (navigator.clipboard && navigator.clipboard.writeText) {
          navigator.clipboard.writeText(target.value).then(function () {
            say('Copied');
          }, copySelection);
        } else {
          copySelection();
        }
      });
    });
  }
  wireCopy();

  Array.prototype.forEach.call(document.querySelectorAll('[data-confirm]'), function (button) {
    button.addEventListener('click', function (e) {
      if (!window.confirm(button.dataset.confirm)) e.preventDefault();
    });
  });

  var form = document.getElementById('upload');
  if (!form) return;

  var fileInput = document.getElementById('file');
  var drop = document.getElementById('drop');
  var dropHint = document.getElementById('drop-hint');
  var progress = document.getElementById('progress');
  var barFill = document.getElementById('bar-fill');
  var progressText = document.getElementById('progress-text');
  var submit = document.getElementById('submit');
  var errorBox = document.getElementById('error');

  // Zero means unlimited.
  var maxSize = parseInt(form.dataset.maxSize, 10) || 0;

  function formatSize(n) {
    var units = ['B', 'KiB', 'MiB', 'GiB', 'TiB'], i = 0;
    while (n >= 1024 && i < units.length - 1) { n /= 1024; i++; }
    return (i === 0 ? n : n.toFixed(2).replace(/\.00$/, '')) + ' ' + units[i];
  }

  function showError(msg) {
    errorBox.textContent = msg;
    errorBox.hidden = !msg;
  }

  function describeSelection() {
    var f = fileInput.files[0];
    dropHint.textContent = f ? f.name + ' - ' + formatSize(f.size)
                             : 'Choose a file, or drop one here.';
  }

  ['dragenter', 'dragover'].forEach(function (name) {
    drop.addEventListener(name, function (e) {
      e.preventDefault();
      drop.classList.add('over');
    });
  });
  ['dragleave', 'drop'].forEach(function (name) {
    drop.addEventListener(name, function () { drop.classList.remove('over'); });
  });
  drop.addEventListener('drop', function (e) {
    e.preventDefault();
    if (!e.dataTransfer.files.length) return;
    // DataTransfer is the only way to put a dropped file into a file input.
    var dt = new DataTransfer();
    dt.items.add(e.dataTransfer.files[0]);
    fileInput.files = dt.files;
    describeSelection();
  });
  fileInput.addEventListener('change', describeSelection);

  form.addEventListener('submit', function (e) {
    var file = fileInput.files[0];
    if (!file) return; // let the browser's own validation speak

    if (maxSize && file.size > maxSize) {
      e.preventDefault();
      showError('That file is ' + formatSize(file.size) + '; your limit is ' +
                formatSize(maxSize) + '.');
      return;
    }

    e.preventDefault();
    showError('');
    submit.disabled = true;
    progress.hidden = false;

    // FormData follows markup order, not painted order, so the options and the
    // token precede the file part as the server requires. The drop zone only
    // looks like it comes first; see the order rules in style.css.
    var data = new FormData(form);
    var started = Date.now();

    var xhr = new XMLHttpRequest();
    xhr.open('POST', form.action);
    // Ask for the page a plain form post would get: the server owns what a
    // finished upload looks like, and this only adds a progress bar.
    xhr.setRequestHeader('Accept', 'text/html');

    xhr.upload.onprogress = function (ev) {
      if (!ev.lengthComputable) return;
      var pct = ev.loaded / ev.total;
      barFill.style.width = (pct * 100).toFixed(1) + '%';
      var elapsed = (Date.now() - started) / 1000;
      var rate = elapsed > 0 ? ev.loaded / elapsed : 0;
      var eta = rate > 0 ? (ev.total - ev.loaded) / rate : 0;
      progressText.textContent =
        (pct * 100).toFixed(0) + '% - ' + formatSize(ev.loaded) + ' of ' +
        formatSize(ev.total) + ' - ' + formatSize(rate) + '/s' +
        (eta > 1 ? ', ' + formatTime(eta) + ' left' : '');
    };

    xhr.onload = function () {
      // Writing the response into this document rather than navigating leaves
      // the address on the form's URL, so a reload offers a fresh form instead
      // of posting the file again.
      document.open();
      document.write(xhr.responseText);
      document.close();
    };
    xhr.onerror = function () {
      submit.disabled = false;
      progress.hidden = true;
      showError('Upload failed: the connection was lost.');
    };

    xhr.send(data);
  });

  function formatTime(s) {
    s = Math.round(s);
    if (s < 60) return s + 's';
    var m = Math.floor(s / 60);
    if (m < 60) return m + 'm ' + (s % 60) + 's';
    return Math.floor(m / 60) + 'h ' + (m % 60) + 'm';
  }
})();