/******************************************************************************
 * This program converts a file into Base64.  Output is to the console.
 * 
 * Copyright © 2021 Richard Lesh.  All rights reserved.
 *****************************************************************************/

#undef NDEBUG

#include "Utils.hpp"
#include <fstream>
#include <iostream>
#include <string>

using namespace Utils;
using namespace std;

static string BASE64_CODES = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static int INPUT_COUNT = 0;
static int OUTPUT_COUNT = 0;
static bool HAS_LEFTOVER_BITS = false;
static int LEFTOVER_BITS = 0;

// Pass -1 to finish conversion
void output_base64(int c) noexcept {
    int const WHICH_POSITION = INPUT_COUNT % 3;
    int six_bit_code = 0;

    if (c < 0) {
        switch (INPUT_COUNT % 3) {
            case 1:
                six_bit_code = (LEFTOVER_BITS << 4);
                cout << BASE64_CODES[six_bit_code];
                cout << "==";
                break;
            case 2:
                six_bit_code = (LEFTOVER_BITS << 2);
                cout << BASE64_CODES[six_bit_code];
                cout << "=";
                break;
            default:
// No padding needed
                break;
        }
        if (OUTPUT_COUNT % 76 != 0) {
            cout << endl;
        }
        return;
    }

    switch (WHICH_POSITION) {
        case 0:
            six_bit_code = (c >> 2) & 0x3F;
            LEFTOVER_BITS = c & 0x3;
            HAS_LEFTOVER_BITS = true;
            cout << BASE64_CODES[six_bit_code];
            break;
        case 1:
            six_bit_code = (LEFTOVER_BITS << 4) | ((c >> 4) & 0xF);
            LEFTOVER_BITS = c & 0xF;
            HAS_LEFTOVER_BITS = true;
            cout << BASE64_CODES[six_bit_code];
            break;
        case 2:
            six_bit_code = (LEFTOVER_BITS << 2) | ((c >> 6) & 0x3);
            LEFTOVER_BITS = c & 0x3F;
            cout << BASE64_CODES[six_bit_code];
            cout << BASE64_CODES[LEFTOVER_BITS];
            LEFTOVER_BITS = 0;
            HAS_LEFTOVER_BITS = false;
            ++OUTPUT_COUNT;
            break;
    }
    ++INPUT_COUNT;
    ++OUTPUT_COUNT;
    if (OUTPUT_COUNT % 76 == 0) {
        cout << endl;
    }
}

void convert_binary_file(string filespec) {
    ifstream ifh(filesystem::path(filespec).c_str(), ios_base::binary);
    if (!ifh.good()) {
        throw ios_base::failure("Problem opening input file!");
    }
    unsigned char c;
    while (Utils::getbytes(ifh, c)) {
        output_base64(c);
    }
    output_base64(-1);
    ifh.close();
}

int main(int argc, char **argv) {
    if (argc != 2) {
        cout << "Syntax: " << argv[0] << " {filename}" << endl;
        exit(1);
    }
    string filespec(argv[1]);
    try {
        convert_binary_file(filespec);
    } catch (ios_base::failure ex) {
        cout << "Error: " << Utils::exceptionMessage<char>(ex) << endl;
    }
    return 0;
}