// Copyright (C) 2005 and onwards Google, Inc.
//
// Base64 en/decoding. Not much to say here except that we work with
// decoded values in arrays of bytes. By "byte" I mean a number in [0,
// 255].


/**
* Base64 en/decoder. Useful in contexts that don't have atob/btoa, or
* when you need a custom encoding function (e.g., websafe base64).
* websafe-base64).
*
* @constructor
*/
function G_Base64() {
    this.byteToCharMap_ = {};
    this.charToByteMap_ = {};
    this.byteToCharMapWebSafe_ = {};
    this.charToByteMapWebSafe_ = {};
    this.init_();
}

/**
* Our default alphabet. Value 64 (=) is special; it means "nothing."
*/
G_Base64.ENCODED_VALS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                        "abcdefghijklmnopqrstuvwxyz" +
                        "0123456789+/=";

/**
* Our websafe alphabet. Value 64 (=) is special; it means "nothing."
*/
G_Base64.ENCODED_VALS_WEBSAFE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                                "abcdefghijklmnopqrstuvwxyz" +
                                "0123456789-_=";

/**
* We want quick mappings back and forth, so we precompute two maps.
*/
G_Base64.prototype.init_ = function() {
    for (var i = 0; i < G_Base64.ENCODED_VALS.length; i++) {
        this.byteToCharMap_[i] = G_Base64.ENCODED_VALS.charAt(i);
        this.charToByteMap_[this.byteToCharMap_[i]] = i;
        this.byteToCharMapWebSafe_[i] = G_Base64.ENCODED_VALS_WEBSAFE.charAt(i);
        this.charToByteMapWebSafe_[this.byteToCharMapWebSafe_[i]] = i;
    }
}

/**
* Base64-encode an array of bytes.
*
* @param input An array of bytes (numbers with value in [0, 255]) to encode
*
* @param opt_webSafe Boolean indicating we should use the alternative alphabet 
*
* @returns String containing the base64 encoding
*/
G_Base64.prototype.encodeByteArray = function(input, opt_webSafe) {

    if (!(input instanceof Array))
        throw new Error("encodeByteArray takes an array as a parameter");

    var byteToCharMap = opt_webSafe ?
                      this.byteToCharMapWebSafe_ :
                      this.byteToCharMap_;

    var output = [];

    var i = 0;
    while (i < input.length) {

        var byte1 = input[i];
        var haveByte2 = i + 1 < input.length;
        var byte2 = haveByte2 ? input[i + 1] : 0;
        var haveByte3 = i + 2 < input.length;
        var byte3 = haveByte3 ? input[i + 2] : 0;

        var outByte1 = byte1 >> 2;
        var outByte2 = ((byte1 & 0x03) << 4) | (byte2 >> 4);
        var outByte3 = ((byte2 & 0x0F) << 2) | (byte3 >> 6);
        var outByte4 = byte3 & 0x3F;

        if (!haveByte3) {
            outByte4 = 64;

            if (!haveByte2)
                outByte3 = 64;
        }

        output.push(byteToCharMap[outByte1]);
        output.push(byteToCharMap[outByte2]);
        output.push(byteToCharMap[outByte3]);
        output.push(byteToCharMap[outByte4]);

        i += 3;
    }

    return output.join("");
}

/**
* Base64-decode a string.
*
* @param input String to decode
*
* @param opt_webSafe Boolean indicating we should use the alternative alphabet 
* 
* @returns Array of bytes representing the decoded value.
*/
G_Base64.prototype.decodeString = function(input, opt_webSafe) {

    if (input.length % 4)
        throw new Error("Length of b64-encoded data must be zero mod four");

    var charToByteMap = opt_webSafe ?
                      this.charToByteMapWebSafe_ :
                      this.charToByteMap_;

    var output = [];

    var i = 0;
    while (i < input.length) {

        var byte1 = charToByteMap[input.charAt(i)];
        var byte2 = charToByteMap[input.charAt(i + 1)];
        var byte3 = charToByteMap[input.charAt(i + 2)];
        var byte4 = charToByteMap[input.charAt(i + 3)];

        if (byte1 === undefined || byte2 === undefined ||
        byte3 === undefined || byte4 === undefined)
            throw new Error("String contains characters not in our alphabet: " +
                      input);

        var outByte1 = (byte1 << 2) | (byte2 >> 4);
        output.push(outByte1);

        if (byte3 != 64) {
            var outByte2 = ((byte2 << 4) & 0xF0) | (byte3 >> 2);
            output.push(outByte2);

            if (byte4 != 64) {
                var outByte3 = ((byte3 << 6) & 0xC0) | byte4;
                output.push(outByte3);
            }
        }

        i += 4;
    }

    return output;
}

/**
* Helper function that turns a string into an array of numbers. 
*
* @param str String to arrify
*
* @returns Array holding numbers corresponding to the UCS character codes
*          of each character in str
*/
G_Base64.prototype.arrayifyString = function(str) {
    var output = [];
    for (var i = 0; i < str.length; i++) {
        var c = str.charCodeAt(i);
        while (c > 0xff) {
            output.push(c & 0xff);
            c >>= 8;
        }
        output.push(c);
    }
    return output;
}

/**
* Helper function that turns an array of numbers into the string
* given by the concatenation of the characters to which the numbesr
* correspond (got that?).
*
* @param array Array of numbers representing characters
*
* @returns {string} Stringification of the array
*/
G_Base64.prototype.stringifyArray = function(array) {
    var output = [];
    for (var i = 0; i < array.length; i++)
        output[i] = String.fromCharCode(array[i]);
    return output.join("");
}


/**
* Lame unittesting function
*/
function TEST_G_Base64() {
    if (G_GDEBUG) {
        var z = "base64 UNITTEST";
        G_debugService.enableZone(z);
        G_Debug(z, "Starting");

        var b = new G_Base64();

        // Let's see if it's sane by feeding it some well-known values. Index i
        // has the input and index i+1 has the expected value.

        var tests =
      ["", "",
        "f", "Zg==",
        "fo", "Zm8=",
        "foo", "Zm9v",
        "foob", "Zm9vYg==",
        "fooba", "Zm9vYmE=",
        "foobar", "Zm9vYmFy",

        // Testing non-ascii characters (1-10 in chinese)
        "\xe4\xb8\x80\xe4\xba\x8c\xe4\xb8\x89\xe5\x9b\x9b\xe4\xba\x94\xe5" +
        "\x85\xad\xe4\xb8\x83\xe5\x85\xab\xe4\xb9\x9d\xe5\x8d\x81",
            "5LiA5LqM5LiJ5Zub5LqU5YWt5LiD5YWr5Lmd5Y2B"];

        for (var i = 0; i < tests.length; i += 2) {
            var enc = b.encodeByteArray(b.arrayifyString(tests[i]));
            G_Assert(z, enc === tests[i + 1],
               "Error encoding: " + tests[i] + " (got " + enc +
               " but wanted " + tests[i + 1] + ")");
            var dec = b.stringifyArray(b.decodeString(enc));
            G_Assert(z, dec === tests[i],
               "Error deocding " + enc + " (got " + dec +
               " but wanted " + tests[i] + ")");
        }

        // Now run it through its paces

        var numIterations = 100;
        for (var i = 0; i < numIterations; i++) {

            var input = [];
            for (var j = 0; j < i; j++)
                input[j] = j % 256;

            var encoded = b.encodeByteArray(input);
            var decoded = b.decodeString(encoded);
            G_Assert(z, !(encoded.length % 4), "Encoded length not a multiple of 4?");
            G_Assert(z, input.length == decoded.length,
               "Decoded length not equal to input length?");

            for (var j = 0; j < i; j++)
                G_Assert(z, input[j] === decoded[j], "Values differ at position " + j);
        }

        // Test non-websafe / websafe difference
        var test = ">>>???>>>???";
        var enc = b.encodeByteArray(b.arrayifyString(test));
        G_Assert(z, enc == "Pj4+Pz8/Pj4+Pz8/", "Non-websafe broken?");
        enc = b.encodeByteArray(b.arrayifyString(test), true /* websafe */);
        G_Assert(z, enc == "Pj4-Pz8_Pj4-Pz8_", "Websafe encoding broken");
        var dec = b.stringifyArray(b.decodeString(enc, true /* websafe */));
        G_Assert(z, dec === test, "Websafe dencoding broken");

        // Test parsing malformed characters
        var caught = false;
        try {
            b.decodeString("foooooo+oooo", true /*websafe*/);
        } catch (e) {
            caught = true;
        }
        G_Assert(z, caught, "Didn't throw on malformed input");

        G_Debug(z, "PASSED");

    }
}