/**
 * some magic number
 */
const GOLDEN_RATIO_64 = 0xfd258f8f3210c68;

/** initial value for the hash code */
const HASH_SEED_64 = 0x47da98c72c46f4a6;

/**
 * Returns an initial value for the hash code
 *
 * @return the initial value
 */
function _longHash() {
    return HASH_SEED_64;
}

function _longCombine(oldHash: number, data: number): number {
    // tslint:disable-next-line:no-bitwise
    return oldHash ^ (data + GOLDEN_RATIO_64 + (oldHash << 6) + (oldHash >> 2));
}

function _hashString(oldHash: number, s: string): number {
    let newHash = oldHash;
    let len = s.length;
    while (len-- > 0) {
        newHash = _longCombine(newHash, s.charCodeAt(len));
    }
    return newHash;
}

// some character sets
const _START = '$_';
const _DIGITS = '0123456789';
const _LOWERCASE = 'abcdefghijklmnopqrstuvwxyz';
const _UPPERCASE = _LOWERCASE.toUpperCase();

// valid first letters
const _FIRST_LETTERS = _START + _LOWERCASE + _UPPERCASE;
const _NEXT_LETTERS = _FIRST_LETTERS + _DIGITS;
const _FIRST_LETTERS_LENGTH = _FIRST_LETTERS.length;
const _NEXT_LETTERS_LENGTH = _NEXT_LETTERS.length;

// shortcut to math functions
const _abs = Math.abs;
const _floor = Math.floor;

/**
 * Converts a hash number into a javascript identifier
 *
 * @param aHash     the hash number
 * @return a valid javascript identifier
 */
function _hashToIdentifier(aHash: number): string {
    // make sure the number is positive
    let num = _abs(_floor(aHash));
    const res = [_FIRST_LETTERS[num % _FIRST_LETTERS_LENGTH]];
    num = _floor(num / _FIRST_LETTERS_LENGTH);
    // next
    while (num > 0) {
        res.push(_NEXT_LETTERS[num % _NEXT_LETTERS_LENGTH]);
        num = _floor(num / _NEXT_LETTERS_LENGTH);
    }
    // ok
    return res.join('');
}

export {
    _hashString as hashString,
    _longHash as longHash,
    _hashToIdentifier as hashToIdentifier
};