angular
    .module('bit.services')

    .factory('passwordService', function () {
        var _service = {};

        _service.generatePassword = function (options) {
            var defaults = {
                length: 10,
                ambiguous: false,
                number: true,
                minNumber: 1,
                uppercase: true,
                minUppercase: 1,
                lowercase: true,
                minLowercase: 1,
                special: false,
                minSpecial: 1
            };

            // overload defaults with given options
            var o = angular.extend({}, defaults, options);

            // sanitize
            if (o.uppercase && o.minUppercase < 0) o.minUppercase = 1;
            if (o.lowercase && o.minLowercase < 0) o.minLowercase = 1;
            if (o.number && o.minNumber < 0) o.minNumber = 1;
            if (o.special && o.minSpecial < 0) o.minSpecial = 1;

            if (!o.length || o.length < 1) o.length = 10;
            var minLength = o.minUppercase + o.minLowercase + o.minNumber + o.minSpecial;
            if (o.length < minLength) o.length = minLength;

            var positions = [];
            if (o.lowercase && o.minLowercase > 0) {
                for (var i = 0; i < o.minLowercase; i++) {
                    positions.push('l');
                }
            }
            if (o.uppercase && o.minUppercase > 0) {
                for (var j = 0; j < o.minUppercase; j++) {
                    positions.push('u');
                }
            }
            if (o.number && o.minNumber > 0) {
                for (var k = 0; k < o.minNumber; k++) {
                    positions.push('n');
                }
            }
            if (o.special && o.minSpecial > 0) {
                for (var l = 0; l < o.minSpecial; l++) {
                    positions.push('s');
                }
            }
            while (positions.length < o.length) {
                positions.push('a');
            }

            // shuffle
            positions.sort(function () {
                return randomInt(0, 1) * 2 - 1;
            });

            // build out the char sets
            var allCharSet = '';

            var lowercaseCharSet = 'abcdefghijkmnopqrstuvwxyz';
            if (o.ambiguous) lowercaseCharSet += 'l';
            if (o.lowercase) allCharSet += lowercaseCharSet;

            var uppercaseCharSet = 'ABCDEFGHIJKLMNPQRSTUVWXYZ';
            if (o.ambiguous) uppercaseCharSet += 'O';
            if (o.uppercase) allCharSet += uppercaseCharSet;

            var numberCharSet = '23456789';
            if (o.ambiguous) numberCharSet += '01';
            if (o.number) allCharSet += numberCharSet;

            var specialCharSet = '!@#$%^&*';
            if (o.special) allCharSet += specialCharSet;

            var password = '';
            for (var m = 0; m < o.length; m++) {
                var positionChars;
                switch (positions[m]) {
                    case 'l': positionChars = lowercaseCharSet; break;
                    case 'u': positionChars = uppercaseCharSet; break;
                    case 'n': positionChars = numberCharSet; break;
                    case 's': positionChars = specialCharSet; break;
                    case 'a': positionChars = allCharSet; break;
                }

                var randomCharIndex = randomInt(0, positionChars.length - 1);
                password += positionChars.charAt(randomCharIndex);
            }

            return password;
        };

        // EFForg/OpenWireless
        // ref https://github.com/EFForg/OpenWireless/blob/master/app/js/diceware.js
        function randomInt(min, max) {
            var rval = 0;
            var range = max - min;

            var bits_needed = Math.ceil(Math.log2(range));
            if (bits_needed > 53) {
                throw new Exception("We cannot generate numbers larger than 53 bits.");
            }
            var bytes_needed = Math.ceil(bits_needed / 8);
            var mask = Math.pow(2, bits_needed) - 1;
            // 7776 -> (2^13 = 8192) -1 == 8191 or 0x00001111 11111111

            // Create byte array and fill with N random numbers
            var byteArray = new Uint8Array(bytes_needed);
            window.crypto.getRandomValues(byteArray);

            var p = (bytes_needed - 1) * 8;
            for (var i = 0; i < bytes_needed; i++) {
                rval += byteArray[i] * Math.pow(2, p);
                p -= 8;
            }

            // Use & to apply the mask and reduce the number of recursive lookups
            rval = rval & mask;

            if (rval >= range) {
                // Integer out of acceptable range
                return randomInt(min, max);
            }
            // Return an integer that falls within the range
            return min + rval;
        }

        return _service;
    });