/*
 * 
 * Hector Dominguez
 * 
 * cs100
 * hdomi001
 * 
 * */

#include <iostream>
#include <sstream>
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <cstdlib>
#include <fcntl.h>
#include <cstring>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>

using namespace std;

int FOREGROUND_BACKGROUND = 0;

void my_shell();
void error_checking(int check);
void forking(int ampersand,int &argc, char**  argv);
int find_ampersand(string line);
void do_work(int ampersand, int &argc, char** &argv, int fdr, int fdw);
char** get_commands(int &argc, int &ampersand);
void build_argv(char** &commands, int &argc, int ampersand, char** &argv);
char* search(char* command);
int check_if_exist(char* path, char* cmd);
char** get_Paths(int &size);
void signal_handlers(int signal);

int main()
{
	signal(SIGINT, signal_handlers);
	while(true)
		my_shell();
	return 0;
}
void my_shell()
{
	int ampersand = 0;
	int argc = 0;
	
	char** commands = get_commands(argc, ampersand);
	char** argv = new char*[argc+1];
	
	build_argv(commands, argc, ampersand, argv);
}

void signal_handlers(int signal)
{
	if(FOREGROUND_BACKGROUND == 0) raise(SIGCONT);
	cout << endl;
}
//functions that exectes the commands
void forking(int ampersand, int &argc, char** &argv, int fdr, int fdw)
{
	char* command = new char;
	int pid = fork();
	switch(pid)
	{
		case -1:
			cout << "error! failed\n";
			break;
		case 0:
			FOREGROUND_BACKGROUND = 1;
			if(fdr != 0) dup2(fdr,0);
			if(fdw != 1) dup2(1,fdw);
			command = search(argv[0]);
			execv(command, argv);
			break;
		default:
			FOREGROUND_BACKGROUND = 0;
			if(ampersand == 0) waitpid(pid, 0, 0);
			break;
	}
}
//fuction that builds the array of pointers "argv"
void build_argv(char** &commands, int &argc, int ampersand, char** &argv)
{
	int newargc = 0;
	int reading = 0;
	
	if(argc == 1)
	{
		argv[newargc] = commands[0];
		newargc++;
		argv[newargc] = NULL;
		forking(ampersand,newargc,argv,0,1);
	}
	else
	{
		argv[newargc] = commands[newargc];
		newargc++;
		
		for( int i = 1; i < argc;++i)
		{
			string temp = commands[i];
			if(temp == "<")
			{
				if(i == 1) continue;
				reading = open(commands[i+1], O_RDONLY);
				error_checking(reading);
				i++;
			}
			else if(temp == ">" )
			{
				if(i == 1) continue;
				reading = open(commands[i-1], O_RDONLY);
				error_checking(reading);
			}
			else
			{
				argv[newargc] = commands[i];
				newargc++;	
			}
		}
		do_work(ampersand,newargc, argv, reading, 1);
	}
}
void do_work(int ampersand, int &argc, char** &argv, int fdr, int fdw)
{
	argv[argc] = NULL;
	forking(ampersand, argc, argv, fdr, fdw);
}
char** get_commands(int &argc, int &ampersand)
{
	char** argv = new char*[256];
	char* line = new char[256];
	
	cout << "% " << flush;
	cin.getline(line,256, '\n');
	
	char* temp = strtok(line, " ");
	string temp2 = temp;
	if(temp2 == "exit") exit(0);
	argv[argc] = temp;
	argc++;
	
	while((temp = strtok(NULL, " ")))
	{
		string amptemp = temp;
		if(amptemp == "&") ampersand = 1;
		argv[argc] = temp;
		argc++;
	}
	argv[argc] = NULL;
	
	return argv;
}
void error_checking(int check)
{
        if(check == -1)
        {
                cout << "Unable to open file, use appropiate parameter\n\n";
                exit(0);
        }
}
int find_ampersand(string line)
{
	for(unsigned int i = 0; i < line.size(); ++i)
		if(line[i] == '&') return 1;
	return 0;
	
}

char** get_Paths(int &size)
{
	char** paths = new char*[256];
	char* path = getenv ("PATH");
	
	char* temp = strtok(path, ":");
	paths[size] = temp;
	size++;
	
	while((temp = strtok(NULL, ":")))
	{
		paths[size] = temp;
		size++;
	}
	paths[size] = NULL;
	return paths;
}

int check_if_exist(char* path, char* cmd)
{
	struct dirent *direntp;
    DIR *dirp = opendir(path);
    if(!dirp) return 0;
    
    while ((direntp = readdir(dirp)))
	{
		string s = direntp->d_name;
		if(s == cmd) return 1;
	}
	closedir(dirp);
	return 0;
}

char* search(char* command)
{
	int counter = 0;
	char** Paths = get_Paths(counter);
	for(int i = 0; i < counter; ++i)
	{
		if(check_if_exist(Paths[i], command) == 1)
		{
			strcat(Paths[i],"/");
			strcat(Paths[i],command);
			return Paths[i];
		}
	}
	cout << "Command does not exist\n";
	exit(0);
}