/* +-----------------------------------------------+
   | John Breaux - jab0910 - JohnBreaux@my.unt.edu |
   |   bscopy.c - CSCE4600 Homework 1 Question 4   |
   +-----------------------------------------------+ */

#include <sys/stat.h> // mkdir()
#include <dirent.h> // opendir()
#include <stdlib.h> // atoi()
#include <stdint.h> // fixed-width integer
#include <string.h> // strerror(), strrchr()
#include <stdio.h>  // printf(), fopen(), fclose()
#include <errno.h>  // errno
#include <time.h>   // clock()

// F_ERROR: check file stream for errors; if error, print
#define F_ERROR(file_obj, ret) if (!file_obj) { printf ("%s: %s\n", #file_obj, strerror(ferror(file_obj)) ); return ret; }
#define MAX_BLOCK_SIZE 0x800

/* fcopy: copy in_filename to out_filename
   args:
      block: block size in bytes
      in_filename: filename of the input file
      out_filename: filename of the output file
   returns:
      size_t: number of bytes copied
*/
size_t fcopy (size_t block, char* in_filename, char* out_filename);
/* fcreate: create a new file at filename, if it doesn't exist.
            If file is attempted to be created in a nonexistent directory,
            recursively create directories until the error is resolved.
            I have no time for grading mistakes due to user error.
   args:
      size: size of file in bytes
      filename: path to file
   returns:
      size_t: difference between number of bytes requested and actually created (should be zero)
*/
int fcreate(size_t size, char* filename);

int main (int argc, char** argv) {
   int block_size = 1;
   char *in = "/tmp/A", *out = "/tmp/B";
   // get argument "block size", "in", "out" from args
   switch (argc) {
      case 4:
         out = argv[3];
      case 3:
         in = argv[2];
      case 2:
         block_size = atoi(argv[1]);
         if (block_size > MAX_BLOCK_SIZE) {
            printf ("%d too long (must not exceed %d)\n", block_size, MAX_BLOCK_SIZE);
            block_size = MAX_BLOCK_SIZE;
         }
      break;
      case 1:
      default:
         printf ("Usage: %s block_size [in [out]]\n", argv[0]);
         exit (EXIT_FAILURE);
   }


   printf ("Copy %s to %s with blocksize of %d.\n", in, out, block_size);
   // start the clock
   clock_t time = clock();
   // perform the copy
   int size = fcopy (block_size, in, out);
   // stop the clock
   time = clock() - time;
   printf ("Copy of %.3f MBytes took %f seconds\n", (double)size / (1024*1024), (double) time / CLOCKS_PER_SEC);
   exit (EXIT_SUCCESS);
}

size_t fcopy (size_t block, char *in_filename, char *out_filename) {
   FILE *in  = fopen (in_filename,  "r"); // Open in for reading
   F_ERROR (in, 0);
   FILE *out = fopen (out_filename, "w"); // Open out for writing
   F_ERROR (out, 0);
   // construct a buffer
   uint8_t buffer[MAX_BLOCK_SIZE];
   size_t bytes_copied = 0;
   // until end of file,
   while (!feof(in)) {
      // Read data from in
      size_t bytes_read = fread(&buffer, block, 1, in);
      // Write data to out
      size_t bytes_written = fwrite(&buffer, bytes_read, 1, out);
      // Make sure wrote same number of bytes as read
      if (bytes_read == bytes_written) {
         bytes_copied += bytes_read;
      } else {
         // Something's gone wrong
         printf ("Copy: %ld not equal %ld! Aborting!\n", bytes_read, bytes_written);
         bytes_copied = -bytes_copied;
         break;
      }
   }
   // Close the files
   fclose(in);
   fclose(out);
   // Return bytes copied
   return bytes_copied;
}

int min(int a, int b) {
   return (b-a >= 0)? a: b;
}

// Recursive mkdir
int dircreate(char* path) {
   while (mkdir(path, 0700)) {
      switch (errno){
         case EEXIST:
            return 0;
         case ENOENT: {
            char subpath[0x1000] = {0}, *last_slash;
            size_t l = 0;
            last_slash = strrchr(path, '/');
            l = path - (last_slash == NULL ? path : last_slash);
            strncpy(subpath, path, min(l, 0x1000)); // construct the substring
            dircreate(subpath);                     // recurse
         }
         default:
            printf("Could not create directory: %s\n", strerror(errno));
            return -1;
      }
   }
   return 0;
}

int fcreate(size_t size, char* filename) {
   // First, check if the directory exists
   char* last_slash = strrchr(filename,'/');
   // find the length of the substring
   int l = filename - (last_slash==NULL?filename:last_slash);
   char path[0x1000] = {0};
   strncpy(path, filename, l);        // construct the substring
   dircreate(path);                   // recursively create new directories until satisfied
   // then, try to create a file in that directory
   uint8_t buffer[0x400] = {0};       // Assemble a buffer
   FILE *file = fopen(filename, "w"); // Open for writing
   F_ERROR(file, -1);                     // abort if error
   // Copy 1024-byte chunks up until the desired filesize < 1024 bytes away
   while (size > 0x400) {
      size -= fwrite(buffer, 0x400, size/0x400, file);
   }
   // Copy the rest of the file
   if (size > 0) {
      size -= fwrite(buffer, size, 1, file);
   }
   return size;
}