/*
 * Copyright (c) 2022 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "base/pt_base64.h"

namespace panda::ecmascript::tooling {
static const uint8_t DECODE_STR_LEN = 3;
static const uint8_t ENCODE_STR_LEN = 4;
static const uint8_t INVAILD_STR = 255;
static uint8_t decodeMap[] = {
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
    255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255,
    255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 255, 255, 255, 255, 255
};
static char encodeMap[] = {"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"};
uint32_t PtBase64::Decode(const std::string &input, std::string &output)
{
    size_t srcLen = input.size();
    if (srcLen < ENCODE_STR_LEN || srcLen % ENCODE_STR_LEN != 0) {
        return 0;
    }

    std::string strDecode;
    uint32_t decodeLen = srcLen / ENCODE_STR_LEN * DECODE_STR_LEN;
    strDecode.resize(decodeLen);

    uint32_t i = 0;
    uint32_t j = 0;
    uint32_t equalsCnt = 0;
    const char* src = input.data();
    char base64Char[ENCODE_STR_LEN];
    while (srcLen--) {
        if (*src != '=') {
            auto const v = decodeMap[static_cast<uint8_t>(*src)];
            if (v == INVAILD_STR) {
                return 0;
            }
            base64Char[j++] = v;
        } else {
            base64Char[j++] = '\0';
            equalsCnt++;
        }
        if (j == ENCODE_STR_LEN) {
            // 2: shift 2bits, 4: shift 4bits
            strDecode[i] = (base64Char[0] << 2) | ((base64Char[1] & 0x30) >> 4);
            // 2: shift 2bits, 4: shift 4bits
            strDecode[i + 1] = (base64Char[1] << 4) | ((base64Char[2] & 0x3c) >> 2);
            // 2: shift 2bits, 3: the last encode str, 6: shift 6bits
            strDecode[i + 2] = (base64Char[2] << 6) | base64Char[3];
            j = 0;
            i += DECODE_STR_LEN;
        }
        src++;
    }
    decodeLen -= equalsCnt;
    strDecode.resize(decodeLen);
    output = std::move(strDecode);
    return decodeLen;
}

uint32_t PtBase64::Encode(const std::string &input, std::string &output)
{
    uint32_t srcLen = input.size();
    if (srcLen == 0) {
        return 0;
    }

    uint32_t lastLen = srcLen % DECODE_STR_LEN;
    uint32_t encodeLen;
    uint32_t equalsCnt;
    if (lastLen == 0) {
        encodeLen = srcLen / DECODE_STR_LEN * ENCODE_STR_LEN;
        equalsCnt = 0;
    } else {
        encodeLen = (srcLen / DECODE_STR_LEN + 1) * ENCODE_STR_LEN;
        equalsCnt = DECODE_STR_LEN - lastLen;
    }

    uint32_t i = 0;
    uint32_t j = 0;
    uint32_t index = 0;
    std::string strEncode;
    strEncode.resize(encodeLen);
    const char* src = input.data();
    while (i + 3 < encodeLen) { // 3: the last encode str
        index = src[j] >> 2; // 2: shift 2bits
        strEncode[i] = encodeMap[index];
        index = ((src[j] & 0x03) << 4) | (src[j + 1] >> 4); // 4: shift 4bits
        strEncode[i + 1] = encodeMap[index];
        index = ((src[j + 1] & 0x0F) << 2) | (src[j + 2] >> 6); // 2: shift 2bits, 6: shift 6bits
        strEncode[i + 2] = encodeMap[index]; // 2: the second char
        index = src[j + 2] & 0x3F; // 2: the second char
        strEncode[i + 3] = encodeMap[index]; // 3: the third char

        i += ENCODE_STR_LEN;
        j += DECODE_STR_LEN;
    }

    if (equalsCnt == 1) {
        strEncode[encodeLen - 1] = '=';
    } else if (equalsCnt == 2) { // 2: Equal's count
        strEncode[encodeLen - 1] = '=';
        strEncode[encodeLen - 2] = '='; // 2: the last two chars
    }
    output = std::move(strEncode);
    return encodeLen;
}
}  // namespace panda::ecmascript::tooling