/*
 *     .============.
 *    //  M A K E  / \
 *   //  C++ DEV  /   \
 *  //  E A S Y  /  \/ \
 * ++ ----------.  \/\  .
 *  \\     \     \ /\  /
 *   \\     \     \   /
 *    \\     \     \ /
 *     -============'
 *
 * Copyright (c) 2018 Hevake and contributors, all rights reserved.
 *
 * This file is part of cpp-tbox (https://github.com/cpp-main/cpp-tbox)
 * Use of this source code is governed by MIT license that can be found
 * in the LICENSE file in the root of the source tree. All contributing
 * project authors may be found in the CONTRIBUTORS.md file in the root
 * of the source tree.
 */
#include "base64.h"

#include <cstdint>
#include <cstring>
#include <tbox/base/assert.h>

namespace tbox {
namespace util {
namespace base64 {

namespace {

#define BASE64_PAD '='

/* BASE 64 encode table */
const char base64en[] = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '0', '1', '2', '3',
    '4', '5', '6', '7', '8', '9', '+', '/',
};

/* ASCII order for BASE 64 decode, 255 in unused character */
const uint8_t base64de[] = {
 // nul, soh, stx, etx, eot, enq, ack, bel,
    255, 255, 255, 255, 255, 255, 255, 255,
 //  bs,  ht,  nl,  vt,  np,  cr,  so,  si,
    255, 255, 255, 255, 255, 255, 255, 255,
 // dle, dc1, dc2, dc3, dc4, nak, syn, etb,
    255, 255, 255, 255, 255, 255, 255, 255,
 // can,  em, sub, esc,  fs,  gs,  rs,  us,
    255, 255, 255, 255, 255, 255, 255, 255,
 //  sp, '!', '"', '#', '$', '%', '&', ''',
    255, 255, 255, 255, 255, 255, 255, 255,
 // '(', ')', '*', '+', ',', '-', '.', '/',
    255, 255, 255,  62, 255, 255, 255,  63,
 // '0', '1', '2', '3', '4', '5', '6', '7',
     52,  53,  54,  55,  56,  57,  58,  59,
 // '8', '9', ':', ';', '<', '=', '>', '?',
     60,  61, 255, 255, 255, 255, 255, 255,
 // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
    255,   0,   1,   2,   3,   4,   5,   6,
 // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
      7,   8,   9,  10,  11,  12,  13,  14,
 // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
     15,  16,  17,  18,  19,  20,  21,  22,
 // 'X', 'Y', 'Z', '[', '\', ']', '^', '_',
     23,  24,  25, 255, 255, 255, 255, 255,
 // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
    255,  26,  27,  28,  29,  30,  31,  32,
 // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
     33,  34,  35,  36,  37,  38,  39,  40,
 // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
     41,  42,  43,  44,  45,  46,  47,  48,
 // 'x', 'y', 'z', '{', '|', '}', '~', del
     49,  50,  51, 255, 255, 255, 255, 255
};

}

size_t DecodeLength(const char *base64_ptr, size_t base64_size)
{
    if (base64_size == 0 || (base64_size & 0x3) != 0)
        return 0;

    size_t len = base64_size / 4 * 3;
    //! 检查字串尾部的=符号
    if (base64_ptr[base64_size - 1] == BASE64_PAD)
        --len;
    if (base64_ptr[base64_size - 2] == BASE64_PAD)
        --len;
    return len;
}

size_t DecodeLength(const char *base64_str)
{
    return DecodeLength(base64_str, ::strlen(base64_str));
}

size_t DecodeLength(const std::string &base64_str)
{
    return DecodeLength(base64_str.data(), base64_str.length());
}

size_t Encode(const void *raw_data_ptr, size_t raw_data_len, char *base64_ptr, size_t base64_size)
{
    TBOX_ASSERT(raw_data_ptr != nullptr);
    TBOX_ASSERT(raw_data_len > 0);
    TBOX_ASSERT(base64_ptr != nullptr);
    TBOX_ASSERT(base64_size > 0);

    if (EncodeLength(raw_data_len) > base64_size)
        return 0;

    int s = 0;
    uint8_t l = 0;
    size_t w_pos = 0;
    const uint8_t *in_bytes = static_cast<const uint8_t*>(raw_data_ptr);

    for (size_t r_pos = 0; r_pos < raw_data_len; r_pos++) {
        uint8_t c = in_bytes[r_pos];

        switch (s) {
            case 0:
                s = 1;
                base64_ptr[w_pos++] = base64en[(c >> 2) & 0x3F];
                break;
            case 1:
                s = 2;
                base64_ptr[w_pos++] = base64en[((l & 0x3) << 4) | ((c >> 4) & 0xF)];
                break;
            case 2:
                s = 0;
                base64_ptr[w_pos++] = base64en[((l & 0xF) << 2) | ((c >> 6) & 0x3)];
                base64_ptr[w_pos++] = base64en[c & 0x3F];
                break;
        }
        l = c;
    }

    switch (s) {
        case 1:
            base64_ptr[w_pos++] = base64en[(l & 0x3) << 4];
            base64_ptr[w_pos++] = BASE64_PAD;
            base64_ptr[w_pos++] = BASE64_PAD;
            break;
        case 2:
            base64_ptr[w_pos++] = base64en[(l & 0xF) << 2];
            base64_ptr[w_pos++] = BASE64_PAD;
            break;
    }

    return w_pos;
}

std::string Encode(const void *raw_data_ptr, size_t raw_data_len)
{
    TBOX_ASSERT(raw_data_ptr != nullptr);
    TBOX_ASSERT(raw_data_len > 0);

    std::string base64_str;
    auto base64_len = EncodeLength(raw_data_len);
    base64_str.reserve(base64_len);

    uint8_t l = 0;
    uint8_t s = 0;
    const uint8_t *in_bytes = static_cast<const uint8_t*>(raw_data_ptr);

    for (size_t r_pos = 0; r_pos < raw_data_len; ++r_pos) {
        uint8_t c = in_bytes[r_pos];

        switch (s) {
            case 0:
                s = 1;
                base64_str.push_back(base64en[(c >> 2) & 0x3F]);
                break;
            case 1:
                s = 2;
                base64_str.push_back(base64en[((l & 0x3) << 4) | ((c >> 4) & 0xF)]);
                break;
            case 2:
                s = 0;
                base64_str.push_back(base64en[((l & 0xF) << 2) | ((c >> 6) & 0x3)]);
                base64_str.push_back(base64en[c & 0x3F]);
                break;
        }
        l = c;
    }

    switch (s) {
        case 1:
            base64_str.push_back(base64en[(l & 0x3) << 4]);
            base64_str.push_back(BASE64_PAD);
            base64_str.push_back(BASE64_PAD);
            break;
        case 2:
            base64_str.push_back(base64en[(l & 0xF) << 2]);
            base64_str.push_back(BASE64_PAD);
            break;
    }

    return base64_str;
}

std::string Encode(const std::vector<uint8_t> &raw_data)
{
    return Encode(raw_data.data(), raw_data.size());
}

size_t Decode(const char *base64_ptr, size_t base64_len, void *raw_data_ptr, size_t raw_data_size)
{
    TBOX_ASSERT(base64_ptr != nullptr);
    TBOX_ASSERT(raw_data_ptr != nullptr);

    if (base64_len & 0x3)
        return 0;

    if (DecodeLength(base64_ptr, base64_len) > raw_data_size)
        return 0;

    size_t w_pos = 0;
    uint8_t *out_bytes = static_cast<uint8_t*>(raw_data_ptr);

    for (size_t r_pos = 0; r_pos < base64_len; r_pos++) {
        char c = base64_ptr[r_pos];
        if (c == BASE64_PAD)
            break;

        uint8_t v = base64de[int(c)];
        if (v == 255)
            return 0;

        switch (r_pos & 0x3) {
            case 0:
                out_bytes[w_pos] = v << 2;
                break;
            case 1:
                out_bytes[w_pos++] |= v >> 4;
                out_bytes[w_pos] = v << 4;
                break;
            case 2:
                out_bytes[w_pos++] |= v >> 2;
                out_bytes[w_pos] = v << 6;
                break;
            case 3:
                out_bytes[w_pos++] |= v;
                break;
        }
    }

    return w_pos;
}

size_t Decode(const char *base64_str, void *raw_data_ptr, size_t raw_data_size)
{
    return Decode(base64_str, ::strlen(base64_str), raw_data_ptr, raw_data_size);
}

size_t Decode(const std::string &base64_str, std::vector<uint8_t> &raw_data)
{
    size_t out_len = DecodeLength(base64_str);
    if (out_len == 0)
        return 0;

    raw_data.reserve(raw_data.size() + out_len);

    uint8_t tmp = 0;
    uint8_t s = 0;

    for (char c : base64_str) {
        if (c == BASE64_PAD)
            break;

        uint8_t v = base64de[int(c)];
        if (v == 255)
            return 0;

        switch (s) {
            case 0:
                tmp = v << 2;
                break;
            case 1:
                tmp |= v >> 4;
                raw_data.push_back(tmp);
                tmp = v << 4;
                break;
            case 2:
                tmp |= v >> 2;
                raw_data.push_back(tmp);
                tmp = v << 6;
                break;
            case 3:
                tmp |= v;
                raw_data.push_back(tmp);
                break;
        }

        ++s;
        s &= 0x03;
    }

    return out_len;
}

}
}
}