#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

#include "tar.h"

int fileexists(char *fname);

int main(int argc, char *argv[])
{
	char *name = argv[1];  // name of archive
	char buffer[300];	   // character buffer for sprintf
	int fp, r, i, j, p, w; // counters and pointers

	if (argc != 2)
	{
		fprintf(stderr, "%s:\n	Usage: utar filename \n", strerror(5));
		exit(EXIT_FAILURE);
	}

	if (fileexists(name) == 0)
	{
		fprintf(stderr, "archive doesnt exist%s\n", strerror(2));
		exit(EXIT_FAILURE);
	}

	fp = open(name, O_RDONLY, 0644); // opens file; creates it if it does not exist;
	if (fp < 0)
	{
		fprintf(stderr, "cannot open %s because of %s\n", argv[2], strerror(5));
		exit(EXIT_FAILURE);
	}

	hdr header;
	int tempfp;
	char byte;
	char f_name[sizeof(short int)];
	short int l;

	while (true)
	{

		r = read(fp, &header, sizeof(hdr));
		if (r != sizeof(hdr))
		{
			fprintf(stderr, "%s: file is not the size of a header object\n", strerror(5));
			exit(EXIT_FAILURE);
		}
		else if (header.magic != 0x63746172)
		{
			fprintf(stderr, "%s: header does not include the magic number [magic number is: %x]\n", strerror(5), header.magic);
			exit(EXIT_FAILURE);
		}

		for (i = 0; i < header.block_count; i++)
		{
			if (header.deleted[i] == 1)
			{
				// skip it
			}
			else
			{
				lseek(fp, header.file_name[i], SEEK_SET);
				read(fp, (char *)&l, sizeof(short int));
				read(fp, f_name, l);

				if (fileexists(f_name))
				{
					fprintf(stderr, "%s\n", strerror(17));
					exit(EXIT_FAILURE);
				}

				tempfp = open(f_name, O_RDWR | O_CREAT, 0644); // creates the new file;
				for (j = 0; j < header.file_size[i]; j++)
				{
					r = read(fp, &byte, sizeof(byte));
					if (r < 0)
					{
						fprintf(stderr, "%s: file %s could not be read from archive\n", f_name, strerror(5));
						exit(EXIT_FAILURE);
					}

					w = write(tempfp, &byte, sizeof(byte));
					if (w < 0)
					{
						fprintf(stderr, "%s: file %s could not be written to file\n", f_name, strerror(5));
						exit(EXIT_FAILURE);
					}
				}
			}
		}

		if (header.next < 0)
		{
			printf("Untared Successfully\n");
			exit(EXIT_SUCCESS);
		}
		else
		{
			p = header.next;
			lseek(fp, header.next, SEEK_SET);
		}
	}

	return EXIT_SUCCESS;
}

int fileexists(char *fname)
{
	if (open(fname, O_RDONLY, 0644) < 0)
	{
		return false; // file doesn't exist
	}
	else
	{
		return true; // file exists
	}
}