/**
 * This is a solution to the numcat problem.
 * It does not:
 * 	-	indent the numbers the right way;
 * 	-	report all the errors the right way.
 */

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

#define BUFFSIZE 4096

char buff[BUFFSIZE];

int number = 2;

/**
 * A simple function to reverse some part of a string
 */
void reverse(char *start, char *end)
{	char x;
	while (start < end)
	{
		x = *start;
		*start = *end;
		*end = x;
		start++;
		end--;
	}
}

/**
 * A simple function to print a number in a string.
 * It also adds a tab before the string and a space after it.
 */
char *itostr(int n, char *result)
{
	int i = 1;
	result[0] = '\t';
	while (n)
	{
		result[i++] = n%10 + '0';
		n/=10;
	}
	reverse(&result[1], &result[i-1]);
	result[i] = ' ';
	result[i+1] = 0;
	return result;
}
/**
 * A function to process the buffer after each read.
 * It splits it in new lines and writes the number and
 * the line.
 */
void output(char *buf, int start, int end)
{
	int i;
	char x[10];

	for (i=start;i<end;i++)
	{
		if (buf[i]=='\n')
		{
			write(1, &buf[start], i+1-start);
			itostr(number++, x);
			write(1, x, strlen(x));
			start = i + 1;
		}
	}
	write(1, buf + start, end - start);
}

int main(int argc, char **argv)
{
	if (argc < 2)
	{
		write(2, "Usage: numcat filename\n", 11);
		exit(EXIT_FAILURE);
	}

	int fd = open(argv[1], O_RDONLY);
	if (fd == -1)
	{
		write(2,"hmm..\n",6);
		exit(EXIT_FAILURE);
	}

	ssize_t read_bytes;
	write(1, "\t1 ",3);
	while (1)
	{
		read_bytes = read(fd, buff, BUFFSIZE);
		if (read_bytes == -1)
		{
			write(2, "Error!\n", 7);
			exit(EXIT_FAILURE);
		}
		if (read_bytes == 0)
		{
			write(1, "\n", 1);
			exit(EXIT_SUCCESS);
		}
		output(buff, 0, read_bytes);
	}
	return 0;
}