/* eslint-env amd, node */

// github.com/umdjs/umd/blob/master/templates/returnExports.js (function (root, factory) {

'use strict';

if (typeof define === 'function' && define.amd) {
  // AMD. Register as an anonymous module.
  define([], factory);
} else if (typeof module === 'object' && module.exports) {
  // Node. Does not work with strict CommonJS, but
  // only CommonJS-like environments that support module.exports,
  // like Node.
  module.exports = factory();
} else {
  // Browser globals (root is window)
  root.AnchorJS = factory();
  root.anchors = new root.AnchorJS();
}

}(this, function () {

'use strict';

function AnchorJS(options) {
  this.options = options || {};
  this.elements = [];

  /**
   * Assigns options to the internal options object, and provides defaults.
   * @param {Object} opts - Options object
   */
  function _applyRemainingDefaultOptions(opts) {
    opts.icon = opts.hasOwnProperty('icon') ? opts.icon : '\ue9cb'; // Accepts characters (and also URLs?), like  '#', '¶', '❡', or '§'.
    opts.visible = opts.hasOwnProperty('visible') ? opts.visible : 'hover'; // Also accepts 'always' & 'touch'
    opts.placement = opts.hasOwnProperty('placement') ? opts.placement : 'right'; // Also accepts 'left'
    opts.ariaLabel = opts.hasOwnProperty('ariaLabel') ? opts.ariaLabel : 'Anchor'; // Accepts any text.
    opts.class = opts.hasOwnProperty('class') ? opts.class : ''; // Accepts any class name.
    // Using Math.floor here will ensure the value is Number-cast and an integer.
    opts.truncate = opts.hasOwnProperty('truncate') ? Math.floor(opts.truncate) : 64; // Accepts any value that can be typecast to a number.
  }

  _applyRemainingDefaultOptions(this.options);

  /**
   * Checks to see if this device supports touch. Uses criteria pulled from Modernizr:
   * https://github.com/Modernizr/Modernizr/blob/da22eb27631fc4957f67607fe6042e85c0a84656/feature-detects/touchevents.js#L40
   * @return {Boolean} - true if the current device supports touch.
   */
  this.isTouchDevice = function() {
    return !!(('ontouchstart' in window) || window.DocumentTouch && document instanceof DocumentTouch);
  };

  /**
   * Add anchor links to page elements.
   * @param  {String|Array|Nodelist} selector - A CSS selector for targeting the elements you wish to add anchor links
   *                                            to. Also accepts an array or nodeList containing the relavant elements.
   * @return {this}                           - The AnchorJS object
   */
  this.add = function(selector) {
    var elements,
        elsWithIds,
        idList,
        elementID,
        i,
        index,
        count,
        tidyText,
        newTidyText,
        readableID,
        anchor,
        visibleOptionToUse,
        indexesToDrop = [];

    // We reapply options here because somebody may have overwritten the default options object when setting options.
    // For example, this overwrites all options but visible:
    //
    // anchors.options = { visible: 'always'; }
    _applyRemainingDefaultOptions(this.options);

    visibleOptionToUse = this.options.visible;
    if (visibleOptionToUse === 'touch') {
      visibleOptionToUse = this.isTouchDevice() ? 'always' : 'hover';
    }

    // Provide a sensible default selector, if none is given.
    if (!selector) {
      selector = 'h2, h3, h4, h5, h6';
    }

    elements = _getElements(selector);

    if (elements.length === 0) {
      return this;
    }

    _addBaselineStyles();

    // We produce a list of existing IDs so we don't generate a duplicate.
    elsWithIds = document.querySelectorAll('[id]');
    idList = [].map.call(elsWithIds, function assign(el) {
      return el.id;
    });

    for (i = 0; i < elements.length; i++) {
      if (this.hasAnchorJSLink(elements[i])) {
        indexesToDrop.push(i);
        continue;
      }

      if (elements[i].hasAttribute('id')) {
        elementID = elements[i].getAttribute('id');
      } else if (elements[i].hasAttribute('data-anchor-id')) {
        elementID = elements[i].getAttribute('data-anchor-id');
      } else {
        tidyText = this.urlify(elements[i].textContent);

        // Compare our generated ID to existing IDs (and increment it if needed)
        // before we add it to the page.
        newTidyText = tidyText;
        count = 0;
        do {
          if (index !== undefined) {
            newTidyText = tidyText + '-' + count;
          }

          index = idList.indexOf(newTidyText);
          count += 1;
        } while (index !== -1);
        index = undefined;
        idList.push(newTidyText);

        elements[i].setAttribute('id', newTidyText);
        elementID = newTidyText;
      }

      readableID = elementID.replace(/-/g, ' ');

      // The following code builds the following DOM structure in a more effiecient (albeit opaque) way.
      // '<a class="anchorjs-link ' + this.options.class + '" href="#' + elementID + '" aria-label="Anchor" data-anchorjs-icon="' + this.options.icon + '"></a>';
      anchor = document.createElement('a');
      anchor.className = 'anchorjs-link ' + this.options.class;
      anchor.href = '#' + elementID;
      anchor.setAttribute('aria-label', this.options.ariaLabel);
      anchor.setAttribute('data-anchorjs-icon', this.options.icon);

      if (visibleOptionToUse === 'always') {
        anchor.style.opacity = '1';
      }

      if (this.options.icon === '\ue9cb') {
        anchor.style.font = '1em/1 anchorjs-icons';

        // We set lineHeight = 1 here because the `anchorjs-icons` font family could otherwise affect the
        // height of the heading. This isn't the case for icons with `placement: left`, so we restore
        // line-height: inherit in that case, ensuring they remain positioned correctly. For more info,
        // see https://github.com/bryanbraun/anchorjs/issues/39.
        if (this.options.placement === 'left') {
          anchor.style.lineHeight = 'inherit';
        }
      }

      if (this.options.placement === 'left') {
        anchor.style.position = 'absolute';
        anchor.style.marginLeft = '-1em';
        anchor.style.paddingRight = '0.5em';
        elements[i].insertBefore(anchor, elements[i].firstChild);
      } else { // if the option provided is `right` (or anything else).
        anchor.style.paddingLeft = '0.375em';
        elements[i].appendChild(anchor);
      }
    }

    for (i = 0; i < indexesToDrop.length; i++) {
      elements.splice(indexesToDrop[i] - i, 1);
    }
    this.elements = this.elements.concat(elements);

    return this;
  };

  /**
   * Removes all anchorjs-links from elements targed by the selector.
   * @param  {String|Array|Nodelist} selector - A CSS selector string targeting elements with anchor links,
   *                                            OR a nodeList / array containing the DOM elements.
   * @return {this}                           - The AnchorJS object
   */
  this.remove = function(selector) {
    var index,
        domAnchor,
        elements = _getElements(selector);

    for (var i = 0; i < elements.length; i++) {
      domAnchor = elements[i].querySelector('.anchorjs-link');
      if (domAnchor) {
        // Drop the element from our main list, if it's in there.
        index = this.elements.indexOf(elements[i]);
        if (index !== -1) {
          this.elements.splice(index, 1);
        }
        // Remove the anchor from the DOM.
        elements[i].removeChild(domAnchor);
      }
    }
    return this;
  };

  /**
   * Removes all anchorjs links. Mostly used for tests.
   */
  this.removeAll = function() {
    this.remove(this.elements);
  };

  /**
   * Urlify - Refine text so it makes a good ID.
   *
   * To do this, we remove apostrophes, replace nonsafe characters with hyphens,
   * remove extra hyphens, truncate, trim hyphens, and make lowercase.
   *
   * @param  {String} text - Any text. Usually pulled from the webpage element we are linking to.
   * @return {String}      - hyphen-delimited text for use in IDs and URLs.
   */
  this.urlify = function(text) {
    // Regex for finding the nonsafe URL characters (many need escaping): & +$,:;=?@"#{}|^~[`%!'<>]./()*\
    var nonsafeChars = /[& +$,:;=?@"#{}|^~[`%!'<>\]\.\/\(\)\*\\]/g,
        urlText;

    // The reason we include this _applyRemainingDefaultOptions is so urlify can be called independently,
    // even after setting options. This can be useful for tests or other applications.
    if (!this.options.truncate) {
      _applyRemainingDefaultOptions(this.options);
    }

    // Note: we trim hyphens after truncating because truncating can cause dangling hyphens.
    // Example string:                      // " ⚡⚡ Don't forget: URL fragments should be i18n-friendly, hyphenated, short, and clean."
    urlText = text.trim()                   // "⚡⚡ Don't forget: URL fragments should be i18n-friendly, hyphenated, short, and clean."
      .replace(/\'/gi, '')                  // "⚡⚡ Dont forget: URL fragments should be i18n-friendly, hyphenated, short, and clean."
      .replace(nonsafeChars, '-')           // "⚡⚡-Dont-forget--URL-fragments-should-be-i18n-friendly--hyphenated--short--and-clean-"
      .replace(/-{2,}/g, '-')               // "⚡⚡-Dont-forget-URL-fragments-should-be-i18n-friendly-hyphenated-short-and-clean-"
      .substring(0, this.options.truncate)  // "⚡⚡-Dont-forget-URL-fragments-should-be-i18n-friendly-hyphenated-"
      .replace(/^-+|-+$/gm, '')             // "⚡⚡-Dont-forget-URL-fragments-should-be-i18n-friendly-hyphenated"
      .toLowerCase();                       // "⚡⚡-dont-forget-url-fragments-should-be-i18n-friendly-hyphenated"

    return urlText;
  };

  /**
   * Determines if this element already has an AnchorJS link on it.
   * Uses this technique: http://stackoverflow.com/a/5898748/1154642
   * @param    {HTMLElemnt}  el - a DOM node
   * @return   {Boolean}     true/false
   */
  this.hasAnchorJSLink = function(el) {
    var hasLeftAnchor = el.firstChild && ((' ' + el.firstChild.className + ' ').indexOf(' anchorjs-link ') > -1),
        hasRightAnchor = el.lastChild && ((' ' + el.lastChild.className + ' ').indexOf(' anchorjs-link ') > -1);

    return hasLeftAnchor || hasRightAnchor || false;
  };

  /**
   * Turns a selector, nodeList, or array of elements into an array of elements (so we can use array methods).
   * It also throws errors on any other inputs. Used to handle inputs to .add and .remove.
   * @param  {String|Array|Nodelist} input - A CSS selector string targeting elements with anchor links,
   *                                         OR a nodeList / array containing the DOM elements.
   * @return {Array} - An array containing the elements we want.
   */
  function _getElements(input) {
    var elements;
    if (typeof input === 'string' || input instanceof String) {
      // See https://davidwalsh.name/nodelist-array for the technique transforming nodeList -> Array.
      elements = [].slice.call(document.querySelectorAll(input));
    // I checked the 'input instanceof NodeList' test in IE9 and modern browsers and it worked for me.
    } else if (Array.isArray(input) || input instanceof NodeList) {
      elements = [].slice.call(input);
    } else {
      throw new Error('The selector provided to AnchorJS was invalid.');
    }
    return elements;
  }

  /**
   * _addBaselineStyles
   * Adds baseline styles to the page, used by all AnchorJS links irregardless of configuration.
   */
  function _addBaselineStyles() {
    // We don't want to add global baseline styles if they've been added before.
    if (document.head.querySelector('style.anchorjs') !== null) {
      return;
    }

    var style = document.createElement('style'),
        linkRule =
        ' .anchorjs-link {'                       +
        '   opacity: 0;'                          +
        '   text-decoration: none;'               +
        '   -webkit-font-smoothing: antialiased;' +
        '   -moz-osx-font-smoothing: grayscale;'  +
        ' }',
        hoverRule =
        ' *:hover > .anchorjs-link,'              +
        ' .anchorjs-link:focus  {'                +
        '   opacity: 1;'                          +
        ' }',
        anchorjsLinkFontFace =
        ' @font-face {'                           +
        '   font-family: "anchorjs-icons";'       + // Icon from icomoon; 10px wide & 10px tall; 2 empty below & 4 above
        '   src: url(data:n/a;base64,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) format("truetype");' +
        ' }',
        pseudoElContent =
        ' [data-anchorjs-icon]::after {'          +
        '   content: attr(data-anchorjs-icon);'   +
        ' }',
        firstStyleEl;

    style.className = 'anchorjs';
    style.appendChild(document.createTextNode('')); // Necessary for Webkit.

    // We place it in the head with the other style tags, if possible, so as to
    // not look out of place. We insert before the others so these styles can be
    // overridden if necessary.
    firstStyleEl = document.head.querySelector('[rel="stylesheet"], style');
    if (firstStyleEl === undefined) {
      document.head.appendChild(style);
    } else {
      document.head.insertBefore(style, firstStyleEl);
    }

    style.sheet.insertRule(linkRule, style.sheet.cssRules.length);
    style.sheet.insertRule(hoverRule, style.sheet.cssRules.length);
    style.sheet.insertRule(pseudoElContent, style.sheet.cssRules.length);
    style.sheet.insertRule(anchorjsLinkFontFace, style.sheet.cssRules.length);
  }
}

return AnchorJS;

}));