#include <iostream>  // so I can do reasonable i/o

#include <sys/types.h>  // open at least
#include <sys/stat.h>   // open
#include <fcntl.h>      // open
#include <unistd.h>     // read

#include <string.h>  // strcmp
#include <stdio.h>   // perror

const int BUFFER_SIZE = 1024;

using namespace std;

void Usage(char *);

int main(int argc, char * argv[]) {
   int inputFD, 
       outputFD, 
       openFlags;

   mode_t filePerms;

   ssize_t numRead;
   char buf[BUFFER_SIZE];

   if (argc != 3 || strcmp(argv[1],"--help") == 0)  {
      Usage(argv[0]);
   }

   cout << "copying " << argv[1] << " to " << argv[2] << endl;

   // open the input file.
   inputFD = open(argv[1], O_RDONLY);

   if (inputFD == -1) {
      perror("Could not open the inputfile ");
      return 1;
   }

   // build the arguments to open the  file.
   //  a | b is the bitwise inclusive or of the two arguments.
   //  1001 | 1010 = 1011
   // The constants are defined in the include files.
   //
   //   create the file if it does not exits
   //   open  for write only
   //   truncate  the file if it does exist
   //        This is standard ifstream.open() behavior
   openFlags = O_CREAT | O_WRONLY | O_TRUNC;

   // rw-rw-rw-
   filePerms = S_IRUSR | S_IWUSR | 
               S_IRGRP | S_IWGRP |
               S_IROTH | S_IWOTH; 
   outputFD = open(argv[2], openFlags, filePerms);

   if (outputFD == -1){
       perror("Could not open the output file ");
       return 1;
   }

   while((numRead = read(inputFD, buf, BUFFER_SIZE)) > 0) {
      if(write(outputFD, buf, numRead) != numRead) {
          perror("buffer write failed");
      }
   }

   if (numRead == -1) {
       perror("A read failed");
       return 1;
   }

   if(close(inputFD) == -1) {
       perror("Fail on closing input file");
       return 1;
   }

   if (close(outputFD) == -1) {
       perror("Fail on closing output file");
       return 1;
   }

   return 0;
   
}

void Usage(char * name) {
   cout << "Usage: " << name  << " inputFile outputFile " << endl;
   return;
}