/*
 * JavaScript base64 / base64url encoder and decoder
 */

var b64c = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"   // base64 dictionary
var b64u = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"   // base64url dictionary
var b64pad_url = '='

/* base64_encode_data
 * Internal helper to encode data to base64 using specified dictionary.
 */
function base64_encode_data(data, len, b64x) {
    var dst = ""
    var i

    for (i = 0; i <= len - 3; i += 3)
    {
        dst += b64x.charAt(data.charCodeAt(i) >>> 2)
        dst += b64x.charAt(((data.charCodeAt(i) & 3) << 4) | (data.charCodeAt(i+1) >>> 4))
        dst += b64x.charAt(((data.charCodeAt(i+1) & 15) << 2) | (data.charCodeAt(i+2) >>> 6))
        dst += b64x.charAt(data.charCodeAt(i+2) & 63)
    }

    if (len % 3 == 2)
    {
        dst += b64x.charAt(data.charCodeAt(i) >>> 2)
        dst += b64x.charAt(((data.charCodeAt(i) & 3) << 4) | (data.charCodeAt(i+1) >>> 4))
        dst += b64x.charAt(((data.charCodeAt(i+1) & 15) << 2))
        dst += b64pad_url
    }
    else if (len % 3 == 1)
    {
        dst += b64x.charAt(data.charCodeAt(i) >>> 2)
        dst += b64x.charAt(((data.charCodeAt(i) & 3) << 4))
        dst += b64pad_url
        dst += b64pad_url
    }

    return dst
}

/* base64_encode
 * Encode a JavaScript string to base64.
 * Specified string is first converted from JavaScript UCS-2 to UTF-8.
 */
function base64_encode(str) {
    var utf8str = unescape(encodeURIComponent(str))
    return base64_encode_data(utf8str, utf8str.length, b64c)
}

/* base64url_encode
 * Encode a JavaScript string to base64url.
 * Specified string is first converted from JavaScript UCS-2 to UTF-8.
 */
function base64url_encode(str) {
    var utf8str = unescape(encodeURIComponent(str))
    return base64_encode_data(utf8str, utf8str.length, b64u)
}

/* base64_charIndex
 * Internal helper to translate a base64 character to its integer index.
 */
function base64_charIndex(c) {
    if (c == "+") return 62
    if (c == "/") return 63
    return b64u.indexOf(c)
}

/* base64_decode
 * Decode a base64 or base64url string to a JavaScript string.
 * Input is assumed to be a base64/base64url encoded UTF-8 string.
 * Returned result is a JavaScript (UCS-2) string.
 */
function base64_decode(data) {
    var dst = ""
    var i, a, b, c, d, z
    
    for (i = 0; i < data.length - 3; i += 4) {
        a = base64_charIndex(data.charAt(i+0))
        b = base64_charIndex(data.charAt(i+1))
        c = base64_charIndex(data.charAt(i+2))
        d = base64_charIndex(data.charAt(i+3))

        dst += String.fromCharCode((a << 2) | (b >>> 4))
        if (data.charAt(i+2) != b64pad_url)
            dst += String.fromCharCode(((b << 4) & 0xF0) | ((c >>> 2) & 0x0F))
        if (data.charAt(i+3) != b64pad_url)
            dst += String.fromCharCode(((c << 6) & 0xC0) | d)
    }

    dst = decodeURIComponent(escape(dst))
    return dst
}

/* base64url_sniff
 * Check whether specified base64 string contains base64url specific characters.
 * Return true if specified string is base64url encoded, false otherwise.
 */
function base64url_sniff(base64) {
    if (base64.indexOf("-") >= 0) return true
    if (base64.indexOf("_") >= 0) return true
    return false
}