// translated from copy.c page 71 of the book.

#include <iostream>
#include <stdio.h>
#include <string>
#include <string.h>

#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>

using namespace std;

const size_t BUF_SIZE{1024};

int main(int argc, char * argv[]) {
    int inputFd{-1}, 
        outputFd{-1}, 
        openFlags{O_CREAT | O_WRONLY | O_TRUNC};

    mode_t filePerms{S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH};

    int numRead;

    char buf[BUF_SIZE];  // warning, danger Will Robinson
    string errorMsg;

    if (argc != 3 or strcmp(argv[1],"--help") == 0) {
       cerr << "Usage: " << argv[0] << " infile outfile " << endl;
    }

    inputFd = open(argv[1], O_RDONLY);
    if (inputFd == -1) {
       errorMsg = argv[1];
       // apparently string + char * is not implemented.
       //errorMsg = " open failed for " + argv[1];
       errorMsg = " open failed for " + errorMsg;
       perror(errorMsg.c_str());
       return 1;
    }

    outputFd = open(argv[2], openFlags, filePerms);
    if (outputFd == -1) {
       errorMsg = argv[2];
       errorMsg = " open failed for " + errorMsg;
       perror(errorMsg.c_str());
       return 1;
    }
     
    while((numRead = read(inputFd, buf, BUF_SIZE)) > 0) {
       if (write(outputFd, buf, numRead) != numRead) {
          perror("could not write the entire output buffer");
          return 1;
       }
    }

    if (close(inputFd) == -1) {
       errorMsg = argv[1];
       errorMsg = " failed to close " + errorMsg;
       perror(errorMsg.c_str());
       return 1;
    }
    if (close(outputFd) == -1) {
       errorMsg = argv[2];
       errorMsg = " failed to close " + errorMsg;
       perror(errorMsg.c_str());
       return 1;
    }

    return 0;


}