angular.module('ui.bootstrap.dateparser', [])

  .service('dateParser', ['$locale', 'orderByFilter', function($locale, orderByFilter) {

    this.parsers = {};

    var formatCodeToRegex = {
      'yyyy': {
        regex: '\\d{4}',
        apply: function(value) { this.year = +value; }
      },
      'yy': {
        regex: '\\d{2}',
        apply: function(value) { this.year = +value + 2000; }
      },
      'y': {
        regex: '\\d{1,4}',
        apply: function(value) { this.year = +value; }
      },
      'MMMM': {
        regex: $locale.DATETIME_FORMATS.MONTH.join('|'),
        apply: function(value) { this.month = $locale.DATETIME_FORMATS.MONTH.indexOf(value); }
      },
      'MMM': {
        regex: $locale.DATETIME_FORMATS.SHORTMONTH.join('|'),
        apply: function(value) { this.month = $locale.DATETIME_FORMATS.SHORTMONTH.indexOf(value); }
      },
      'MM': {
        regex: '0[1-9]|1[0-2]',
        apply: function(value) { this.month = value - 1; }
      },
      'M': {
        regex: '[1-9]|1[0-2]',
        apply: function(value) { this.month = value - 1; }
      },
      'dd': {
        regex: '[0-2][0-9]{1}|3[0-1]{1}',
        apply: function(value) { this.date = +value; }
      },
      'd': {
        regex: '[1-2]?[0-9]{1}|3[0-1]{1}',
        apply: function(value) { this.date = +value; }
      },
      'EEEE': {
        regex: $locale.DATETIME_FORMATS.DAY.join('|')
      },
      'EEE': {
        regex: $locale.DATETIME_FORMATS.SHORTDAY.join('|')
      }
    };

    this.createParser = function(format) {
      var map = [], regex = format.split('');

      angular.forEach(formatCodeToRegex, function(data, code) {
        var index = format.indexOf(code);

        if (index > -1) {
          format = format.split('');

          regex[index] = '(' + data.regex + ')';
          format[index] = '$'; // Custom symbol to define consumed part of format
          for (var i = index + 1, n = index + code.length; i < n; i++) {
            regex[i] = '';
            format[i] = '$';
          }
          format = format.join('');

          map.push({ index: index, apply: data.apply });
        }
      });

      return {
        regex: new RegExp('^' + regex.join('') + '$'),
        map: orderByFilter(map, 'index')
      };
    };

    this.parse = function(input, format) {
      if ( !angular.isString(input) ) {
        return input;
      }

      format = $locale.DATETIME_FORMATS[format] || format;

      if ( !this.parsers[format] ) {
        this.parsers[format] = this.createParser(format);
      }

      var parser = this.parsers[format],
        regex = parser.regex,
        map = parser.map,
        results = input.match(regex);

      if ( results && results.length ) {
        var fields = { year: 1900, month: 0, date: 1, hours: 0 }, dt;

        for( var i = 1, n = results.length; i < n; i++ ) {
          var mapper = map[i-1];
          if ( mapper.apply ) {
            mapper.apply.call(fields, results[i]);
          }
        }

        if ( isValid(fields.year, fields.month, fields.date) ) {
          dt = new Date( fields.year, fields.month, fields.date, fields.hours);
        }

        return dt;
      }
    };

    // Check if date is valid for specific month (and year for February).
    // Month: 0 = Jan, 1 = Feb, etc
    function isValid(year, month, date) {
      if ( month === 1 && date > 28) {
        return date === 29 && ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0);
      }

      if ( month === 3 || month === 5 || month === 8 || month === 10) {
        return date < 31;
      }

      return true;
    }

  }]);