#include <cctype>
#include <chrono>
#include <cstdint>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>

#include <sys/types.h>
#include <sys/stat.h>

// https://stackoverflow.com/questions/3883993/how-could-these-case-conversion-functions-be-improved

// g++ -std=c++11 -O3 lowercase_util.cc -o lowercase_util
int main(const int argc, char** argv)
{
    if (argc < 2)
    {
        std::cerr << "USAGE: " << argv[0] << " <filename>" << std::endl;
        return -1;
    }
    std::cout << "Lowercase Test Util\n" << std::endl;
    
    
    std::string filePath(argv[1]);

    // Stat the file path to get its size
    struct stat fs_stat;
    const int gotStatOK(stat(filePath.c_str(), &fs_stat));
    if (gotStatOK < 0)
    {
        perror("stat()");
        return -1;
    }

    uint32_t fileSize = fs_stat.st_size;
    std::cout << "File size: " << fileSize << "\n" << std::endl;
    
    // Read in file
    std::ifstream inFileStream(filePath, std::ios::in | std::ios::binary);
    if (! inFileStream)
    {
        std::cerr << "Unable to open specified file." << std::endl;
        return -1;
    }
    
    // Read file in then close stream
    std::vector<char> contents;
    contents.resize(fileSize);
    inFileStream.read(contents.data(), fileSize);
    inFileStream.close();
    
    // TEST1: regular tolower() -----------------------------------------------
    std::vector<char> copy1(contents);
    
    auto start = std::chrono::system_clock::now();
    
    for (uint32_t idx = 0; idx < fileSize; ++idx)
    {
        copy1[idx] = tolower(copy1[idx]);
    }
    
    auto end = std::chrono::system_clock::now();
    auto diff = end - start;
    std::cout << "Test 1 -- duration: " 
              << std::chrono::duration<double, std::milli>(diff).count() 
              << " ms" << std::endl;
    
    // TEST2: technique 1 -----------------------------------------------------
    std::vector<char> copy2(contents);
    
    start = std::chrono::system_clock::now();
    
    for (uint32_t idx = 0; idx < fileSize; ++idx)
    {
        // *c += (*c - 'A' < 26U) << 5;
        copy2[idx] += (copy2[idx] - 'A' < 26U) << 5;
    }
    
    end = std::chrono::system_clock::now();
    diff = end - start;
    std::cout << "Test 2 -- duration: " 
              << std::chrono::duration<double, std::milli>(diff).count() 
              << " ms" << std::endl;
    
    #if 0
    // Verify copy2
    std::ofstream outStream1("output_copy2.txt", std::ios::out | std::ios::binary);
    outStream1.write(copy2.data(), fileSize);
    outStream1.close();
    #endif
    
    
    // TEST3: technque 2 ------------------------------------------------------
    std::vector<char> copy3(contents);
    
    start = std::chrono::system_clock::now();
    
    for (uint32_t idx = 0; idx < fileSize; ++idx)
    {
        // *c += (64U - *c & *c - 91U) >> CHAR_BIT * sizeof(unsigned) - 1 << 5;
        // *c += ((64U - *c & *c - 91U) >> 31) << 5;
        copy3[idx] += ((64U - copy3[idx] & copy3[idx] - 91U) >> 31) << 5;
    }
    
    end = std::chrono::system_clock::now();
    diff = end - start;
    std::cout << "Test 3 -- duration: " 
              << std::chrono::duration<double, std::milli>(diff).count() 
              << " ms" << std::endl;
    
    #if 0
    // Verify copy3
    std::ofstream outStream2("output_copy3.txt", std::ios::out | std::ios::binary);
    outStream2.write(copy3.data(), fileSize);
    outStream2.close();
    #endif
    
    
    // TEST 4: technique 3 ----------------------------------------------------
    std::vector<char> copy4(contents);
    
    start = std::chrono::system_clock::now();
    
    for (uint32_t idx = 0; idx < fileSize; ++idx)
    {
        // c += (((96-(int)c)&((int)c-123))>>9)&(-32);
        copy4[idx] += (((96 - (int)copy4[idx]) & ((int)copy4[idx] - 123)) >> 9) & (-32);
    }
    
    end = std::chrono::system_clock::now();
    diff = end - start;
    std::cout << "Test 4 -- duration: " 
              << std::chrono::duration<double, std::milli>(diff).count() 
              << " ms" << std::endl;
    
    return 0;
}