// Utilities
//
'use strict';


function _class(obj) { return Object.prototype.toString.call(obj); }

function isString(obj) { return _class(obj) === '[object String]'; }

// Merge objects
//
function assign(obj /*from1, from2, from3, ...*/) {
  var sources = Array.prototype.slice.call(arguments, 1);
  while (sources.length) {
    var source = sources.shift();
    if (!source) { continue; }

    if (typeof(source) !== 'object') {
      throw new TypeError(source + 'must be non-object');
    }

    for (var p in source) {
      if (source.hasOwnProperty(p)) {
        obj[p] = source[p];
      }
    }
  }

  return obj;
}


var UNESCAPE_MD_RE = /\\([\\!"#$%&'()*+,.\/:;<=>?@[\]^_`{|}~-])/g;

function unescapeMd(str) {
  if (str.indexOf('\\') < 0) { return str; }
  return str.replace(UNESCAPE_MD_RE, '$1');
}

function isValidEntityCode(c) {
  /*eslint no-bitwise:0*/
  // broken sequence
  if (c >= 0xD800 && c <= 0xDFFF) { return false; }
  // never used
  if (c >= 0xFDD0 && c <= 0xFDEF) { return false; }
  if ((c & 0xFFFF) === 0xFFFF || (c & 0xFFFF) === 0xFFFE) { return false; }
  // control codes
  if (c >= 0x00 && c <= 0x08) { return false; }
  if (c === 0x0B) { return false; }
  if (c >= 0x0E && c <= 0x1F) { return false; }
  if (c >= 0x7F && c <= 0x9F) { return false; }
  // out of range
  if (c > 0x10FFFF) { return false; }
  return true;
}

function fromCodePoint(c) {
  /*eslint no-bitwise:0*/
  if (c > 0xffff) {
    c -= 0x10000;
    var surrogate1 = 0xd800 + (c >> 10),
        surrogate2 = 0xdc00 + (c & 0x3ff);

    return String.fromCharCode(surrogate1, surrogate2);
  }
  return String.fromCharCode(c);
}

var NAMED_ENTITY_RE   = /&([a-z][a-z0-9]{1,31});/gi;
var entities = require('./entities');

function replaceEntities(str) {
  if (str.indexOf('&') < 0) { return str; }

  return str.replace(NAMED_ENTITY_RE, function(match, name) {
    if (entities.hasOwnProperty(name)) {
      return entities[name];
    }
    return match;
  });
}


exports.assign = assign;
exports.isString = isString;
exports.unescapeMd = unescapeMd;
exports.isValidEntityCode = isValidEntityCode;
exports.fromCodePoint = fromCodePoint;
exports.replaceEntities = replaceEntities;