#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <iostream>

//Jason Kim
//CSE 660
//Lab 1
//Due 4/15/05 


using namespace std;

int main()
{
	//variables
	int file1,file2,file3,file4;
	char buf[BUFSIZ];
	int bsize,bsize2;
	char step2[10] = "Jason Kim";	
	char step3[17] = "ABCDEFGHabcdefgh";
	char step4[17] = "ijklmnopIJKLMNOP";
	
	//Step 1
	// Create ABC1 and ABC2 files
	file1 = creat("abc1.txt",S_IRWXU);
	close(file1); //creates abc1 file with read,write,and execute permission
	file2 = creat("abc2.txt",S_IRWXU);
	close(file2); //creates abc2 file with read,write,and execute permission
	file4 = creat("abc3.txt",S_IRWXU);//create abc3
	close(file4);
	//note this creates abc files in my home directory
	//for another user, simply change the path to /home/youruser/abc1
	if(file1 == -1)
	{
		cout << endl;
		cout << "The file was not created, this may because you did not change the file path to your specified directory, or you dont have permission to write files" << endl;
	}

	//opens x.x file 
	file1 = open("/usr/class/cis660/x.x",O_RDONLY);
	if(file1 == -1)//check if file could not open
	{
		cout << "could not open file" << endl;
		exit(1);
	}
	
	file2 = open("abc1.txt",O_RDWR);
	file3 = open("abc2.txt",O_RDWR);
	file4 = open("abc3.txt",O_RDWR);
	
	//pulls of the first 10 characters and writes them to abc1
	bsize = read(file1,buf,10);
	write(file2,buf,10);
	//pulls off the next 20 characters and writes them to abc2
	bsize2 = read(file1,buf,20);
	write(file3,buf,20);

	//continues doing the above until end of file
	while( (bsize>=10) || (bsize2>=20) )
	{
		bsize = read(file1,buf,10);
		write(file2,buf,10);
		bsize2 = read(file1,buf,20);
		write(file3,buf,20);
	}

	//step 2 Append "Jason Kim" (My Name) into abc1 at the end of the file
	lseek(file2,0,SEEK_END);
	write(file2,step2,14);
	
	//step 3 Write ABCDEFGHabcdefgh starting from location 100 int ABC1 (increase file size by 16)
	lseek(file2,100,SEEK_SET);
	write(file2,step3,17);

	//step 4 inserts into abc2 ijklmnopIJKLMNOP into location 160
	lseek(file3,160,SEEK_SET);
	write(file3,step4,17); 
	

	//step 5 create abc3, and copies abc1 into abc3 100 characters at a time
	lseek(file2,0,SEEK_SET);//reset buffer pointer of file abc1 back to start 	  of the file abc1
	
	bsize = read(file2,buf,100); //read 100 characters from abc1
	write(file4,buf,100); //write 100 characters into abc3
	while(bsize>=100)
	{
		bsize = read(file2,buf,100);
		write(file4,buf,100);
	}
	

	
	//step 6 appends abc3 with abc2 in reverse order
	
	//first read all of abc2
	lseek(file3,0,SEEK_SET);
	bsize = read(file3,buf,1000);
	while(bsize>=1000)
	{
		bsize = read(file3,buf,1000);
	}
	char temp[BUFSIZ];
	int tsize=BUFSIZ;
	while(tsize > 0)// now reverse the order
	{
		temp[tsize] = buf[tsize];
		if(tsize != 0)
		{
			tsize--;
		}
	}
	lseek(file4,0,SEEK_END);
	write(file4,buf,BUFSIZ); //append reverse abc2 into abc3
	

	//step 7 reads abc3 80 characters at a time and prints 80 characters to 	the screen. then deletes abc1,abc2,abc3	
	
	lseek(file4,0,SEEK_SET);	
	read(file4,buf,80);
	int count=0;
	while(count < 80)
	{
		cout << buf[count];
		count++;
	}

	file1 = unlink("abc1.txt"); //deletes files
	unlink("abc2.txt");
	unlink("abc3.txt");
	if(file1 == -1)
	{
		cout << endl;
		cout << "Files were not deleted, this may because you do not have permission to delete it" << endl;	
	}
	return 0;
}