/*jslint node: true*/
var toArray = require('lodash/toArray');
var emojiByName = require('./emoji.json');

"use strict";

/**
 * regex to parse emoji in a string - finds emoji, e.g. :coffee:
 */
var emojiNameRegex = /:([a-zA-Z0-9_\-\+]+):/g;

/**
 * regex to trim whitespace
 * use instead of String.prototype.trim() for IE8 support
 */
var trimSpaceRegex = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g;

/**
 * Removes colons on either side
 * of the string if present
 * @param  {string} str
 * @return {string}
 */
function stripColons (str) {
  var colonIndex = str.indexOf(':');
  if (colonIndex > -1) {
    // :emoji: (http://www.emoji-cheat-sheet.com/)
    if (colonIndex === str.length - 1) {
      str = str.substring(0, colonIndex);
      return stripColons(str);
    } else {
      str = str.substr(colonIndex + 1);
      return stripColons(str);
    }
  }

  return str;
}

/**
 * Adds colons to either side
 * of the string
 * @param {string} str
 * @return {string}
 */
function wrapColons (str) {
  return (typeof str === 'string' && str.length > 0) ? ':' + str + ':' : str;
}

/**
 * Ensure that the word is wrapped in colons
 * by only adding them, if they are not there.
 * @param {string} str
 * @return {string}
 */
function ensureColons (str) {
  return (typeof str === 'string' && str[0] !== ':') ? wrapColons(str) : str;
}

// Non spacing mark, some emoticons have them. It's the 'Variant Form',
// which provides more information so that emoticons can be rendered as
// more colorful graphics. FE0E is a unicode text version, where as FE0F
// should be rendered as a graphical version. The code gracefully degrades.
var NON_SPACING_MARK = String.fromCharCode(65039); // 65039 - '️' - 0xFE0F;
var nonSpacingRegex = new RegExp(NON_SPACING_MARK, 'g')

// Remove the non-spacing-mark from the code, never send a stripped version
// to the client, as it kills graphical emoticons.
function stripNSB (code) {
  return code.replace(nonSpacingRegex, '');
};

// Reversed hash table, where as emojiByName contains a { heart: '❤' }
// dictionary emojiByCode contains { ❤: 'heart' }. The codes are normalized
// to the text version.
var emojiByCode = Object.keys(emojiByName).reduce(function(h,k) {
  h[stripNSB(emojiByName[k])] = k;
  return h;
}, {});

/**
 * Emoji namespace
 */
var Emoji = {
  emoji: emojiByName,
};

/**
 * get emoji code from name. return emoji code back if code is passed in.
 * @param  {string} emoji
 * @return {string}
 */
Emoji._get = function _get (emoji) {
  if (emojiByCode[stripNSB(emoji)]) {
    return emoji;
  } else if (emojiByName.hasOwnProperty(emoji)) {
    return emojiByName[emoji];
  }

  return ensureColons(emoji);
};

/**
 * get emoji code from :emoji: string or name
 * @param  {string} emoji
 * @return {string}
 */
Emoji.get = function get (emoji) {
  emoji = stripColons(emoji);

  return Emoji._get(emoji);
};

/**
 * find the emoji by either code or name
 * @param {string} nameOrCode The emoji to find, either `coffee`, `:coffee:` or `☕`;
 * @return {object}
 */
Emoji.find = function find (nameOrCode) {
  return Emoji.findByName(nameOrCode) || Emoji.findByCode(nameOrCode);
};

/**
 * find the emoji by name
 * @param {string} name The emoji to find either `coffee` or `:coffee:`;
 * @return {object}
 */
Emoji.findByName = function findByName (name) {
  var stripped = stripColons(name);
  var emoji = emojiByName[stripped];

  return emoji ? ({ emoji: emoji, key: stripped }) : undefined;
};

/**
 * find the emoji by code (emoji)
 * @param {string} code The emoji to find; for example `☕` or `☔`
 * @return {object}
 */
Emoji.findByCode = function findByCode (code) {
  var stripped = stripNSB(code);
  var name = emojiByCode[stripped];

  // lookup emoji to ensure the Variant Form is returned
  return name ? ({ emoji: emojiByName[name], key: name }) : undefined;
};


/**
 * Check if an emoji is known by this library
 * @param {string} nameOrCode The emoji to validate, either `coffee`, `:coffee:` or `☕`;
 * @return {object}
 */
Emoji.hasEmoji = function hasEmoji (nameOrCode) {
  return Emoji.hasEmojiByName(nameOrCode) || Emoji.hasEmojiByCode(nameOrCode);
};

/**
 * Check if an emoji with given name is known by this library
 * @param {string} name The emoji to validate either `coffee` or `:coffee:`;
 * @return {object}
 */
Emoji.hasEmojiByName = function hasEmojiByName (name) {
  var result = Emoji.findByName(name);
  return !!result && result.key === stripColons(name);
};

/**
 * Check if a given emoji is known by this library
 * @param {string} code The emoji to validate; for example `☕` or `☔`
 * @return {object}
 */
Emoji.hasEmojiByCode = function hasEmojiByCode (code) {
  var result = Emoji.findByCode(code);
  return !!result && stripNSB(result.emoji) === stripNSB(code);
};

/**
 * get emoji name from code
 * @param  {string} emoji
 * @param  {boolean} includeColons should the result include the ::
 * @return {string}
 */
Emoji.which = function which (emoji_code, includeColons) {
  var code = stripNSB(emoji_code);
  var word = emojiByCode[code];

  return includeColons ? wrapColons(word) : word;
};

/**
 * emojify a string (replace :emoji: with an emoji)
 * @param  {string} str
 * @param  {function} on_missing (gets emoji name without :: and returns a proper emoji if no emoji was found)
 * @param  {function} format (wrap the returned emoji in a custom element)
 * @return {string}
 */
Emoji.emojify = function emojify (str, on_missing, format) {
  if (!str) return '';

  return str.split(emojiNameRegex) // parse emoji via regex
            .map(function parseEmoji(s, i) {
              // every second element is an emoji, e.g. "test :fast_forward:" -> [ "test ", "fast_forward" ]
              if (i % 2 === 0) return s;
              var emoji = Emoji._get(s);
              var isMissing = emoji.indexOf(':') > -1;

              if (isMissing && typeof on_missing === 'function') {
                return on_missing(s);
              }

              if (!isMissing && typeof format === 'function') {
                return format(emoji, s);
              }

              return emoji;
            })
            .join('') // convert back to string
  ;
};

/**
 * return a random emoji
 * @return {string}
 */
Emoji.random = function random () {
  var emojiKeys = Object.keys(emojiByName);
  var randomIndex = Math.floor(Math.random() * emojiKeys.length);
  var key = emojiKeys[randomIndex];
  var emoji = Emoji._get(key);
  return { key: key, emoji: emoji };
}

/**
 *  return an collection of potential emoji matches
 *  @param {string} str
 *  @return {Array.<Object>}
 */
Emoji.search = function search (str) {
  var emojiKeys = Object.keys(emojiByName);
  var matcher = stripColons(str)
  var matchingKeys = emojiKeys.filter(function(key) {
    return key.toString().indexOf(matcher) === 0;
  });
  return matchingKeys.map(function(key) {
    return {
      key: key,
      emoji: Emoji._get(key),
    };
  });
}

/**
 * unemojify a string (replace emoji with :emoji:)
 * @param  {string} str
 * @return {string}
 */
Emoji.unemojify = function unemojify (str) {
  if (!str) return '';
  var words = toArray(str);

  return words.map(function(word) {
    return Emoji.which(word, true) || word;
  }).join('');
};

/**
 * replace emojis with replacement value
 * @param {string} str
 * @param {function|string} the string or callback function to replace the emoji with
 * @param {boolean} should trailing whitespaces be cleaned? Defaults false
 * @return {string}
 */
Emoji.replace = function replace (str, replacement, cleanSpaces) {
  if (!str) return '';

  var replace = typeof replacement === 'function' ? replacement : function() { return replacement; };
  var words = toArray(str);

  var replaced = words.map(function(word, idx) {
    var emoji = Emoji.findByCode(word);

    if (emoji && cleanSpaces && words[idx + 1] === ' ') {
      words[idx + 1] = '';
    }

    return emoji ? replace(emoji) : word;
  }).join('');

  return cleanSpaces ? replaced.replace(trimSpaceRegex, '') : replaced;
};


/**
 * remove all emojis from a string
 * @param {string} str
 * @return {string}
 */
Emoji.strip = function strip (str) {
  return Emoji.replace(str, '', true);
};

module.exports = Emoji;