// ==UserScript==
// @name         GitHub Monospace Font Toggle
// @version      1.0.0
// @description  A userscript that adds monospace font toggle to comments
// @license      https://creativecommons.org/licenses/by-sa/4.0/
// @namespace    https://github.com/StylishThemes
// @include      https://github.com/*
// @grant        GM_addStyle
// @run-at       document-end
// @author       StylishThemes
// @downloadURL none
// ==/UserScript==
/* global GM_addStyle */
(function() {
  "use strict";
  /*
  This code is also part of the GitHub-Dark Script (https://github.com/StylishThemes/GitHub-Dark-Script)
  Extracted out into a separate userscript in case users only want to add this functionality
  */
  var busy = false,

  icon = [
    "<svg class='octicon' xmlns='http://www.w3.org/2000/svg' width='18' height='18' viewbox='0 0 32 32'>",
      "<path d='M5.91 7.31v8.41c0 .66.05 1.09.14 1.31.09.21.23.37.41.48.18.11.52.16 1.02.16v.41H2.41v-.41c.5 0 .86-.05 1.03-.14.16-.11.3-.27.41-.5.11-.23.16-.66.16-1.3V11.7c0-1.14-.04-1.87-.11-2.2-.04-.26-.13-.42-.24-.53-.11-.1-.27-.14-.46-.14-.21 0-.48.05-.77.18l-.18-.41 3.14-1.28h.52v-.01zm-.95-5.46c.32 0 .59.11.82.34.23.23.34.5.34.82 0 .32-.11.59-.34.82-.23.22-.51.34-.82.34-.32 0-.59-.11-.82-.34s-.36-.5-.36-.82c0-.32.11-.59.34-.82.24-.23.51-.34.84-.34zm19.636 19.006h-3.39v-1.64h5.39v9.8h3.43v1.66h-9.18v-1.66h3.77v-8.16h-.02zm.7-6.44c.21 0 .43.04.63.13.18.09.36.2.5.34s.25.3.34.5c.07.18.13.39.13.61 0 .22-.04.41-.13.61s-.19.36-.34.5-.3.25-.5.32c-.2.09-.39.13-.62.13-.21 0-.43-.04-.61-.12-.19-.07-.35-.19-.5-.34-.14-.14-.25-.3-.34-.5-.07-.2-.13-.39-.13-.61s.04-.43.13-.61c.07-.18.2-.36.34-.5s.31-.25.5-.34c.17-.09.39-.12.6-.12zM2 30L27.82 2H30L4.14 30H2z'/>",
    "</svg>"
  ].join(""),

  // Add monospace font toggle
  addMonospaceToggle = function() {
    busy = true;
    var indx, el, button,
      toolbars = document.querySelectorAll(".toolbar-commenting"),
      len = toolbars.length;
    for (indx = 0; indx < len; indx++) {
      el = toolbars[indx];
      if (!el.querySelector(".ghd-monospace")) {
        button = document.querySelector("button");
        button.type = "button";
        button.className = "ghd-monospace toolbar-item tooltipped tooltipped-n";
        button.setAttribute("aria-label", "Toggle monospaced font");
        button.setAttribute("tabindex", "-1");
        button.innerHTML = icon;
        el.insertBefore(button, el.childNodes[0]);
      }
    }
    busy = false;
  },

  matches = function(el, selector) {
    // https://developer.mozilla.org/en-US/docs/Web/API/Element/matches
    var matches = document.querySelectorAll(selector),
      i = matches.length;
    while (--i >= 0 && matches.item(i) !== el) {}
    return i > -1;
  },

  closest = function(el, selector) {
    while (el && !matches(el, selector)) {
      el = el.parentNode;
    }
    return matches(el, selector) ? el : null;
  },

  addBindings = function() {
    document.querySelector("body").addEventListener("click", function(event) {
      var textarea, active,
        target = event.target;
      if (target && target.classList.contains("ghd-monospace")) {
        textarea = closest(target, ".previewable-comment-form");
        textarea = textarea.querySelector(".comment-form-textarea");
        textarea.classList.toggle("ghd-monospace-font");
        textarea.focus();
        active = textarea.classList.contains("ghd-monospace-font");
        target.classList[active ? "add" : "remove"]("ghd-icon-active");
        return false;
      }
    });
  },

  targets = document.querySelectorAll([
    "#js-repo-pjax-container",
    "#js-pjax-container",
    ".js-preview-body"
  ].join(","));

  // don't initialize if GitHub Dark Script is active
  if (!document.querySelector("#ghd-menu")) {
    GM_addStyle([
      // monospace font toggle
      ".ghd-monospace-font { font-family: Menlo, Inconsolata, 'Droid Mono', monospace !important; font-size: 1em !important; }",
      ".ghd-monospace > svg { pointer-events: none; }"
    ].join(""));

    Array.prototype.forEach.call(targets, function(target) {
      new MutationObserver(function(mutations) {
        mutations.forEach(function(mutation) {
          // preform checks before adding code wrap to minimize function calls
          if (!busy && mutation.target === target) {
            addMonospaceToggle();
          }
        });
      }).observe(target, {
        childList: true,
        subtree: true
      });
    });

    addBindings();
    addMonospaceToggle();
  }

})();