#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <readline/readline.h>
#include <readline/history.h>
#include <sys/wait.h>
#include <sys/types.h>

int myshell_exit(char **args);
int myshell_help(char **args);
char **myshell_split_line(char *line);
int myshell_execute(char **args);

const int builtin_functions_total = 2;
char *builtin_functions_names[] = { "help", "exit" };
int (*builtin_functions[])(char **) = { &myshell_help, &myshell_exit };

int myshell_exit(char **args)
{
	exit(0);
}

int myshell_help(char **args)
{
	printf("Built-in functions: help, exit\n");
	return 0;
}

char **myshell_split_line(char *line)
{
	int bufsize = 64;
	int position = 0;
	char **tokens = malloc(bufsize * sizeof(char*));
 	char *token;

	if(!tokens){
	    fprintf(stderr, "myshell: allocation error\n");
	    exit(EXIT_FAILURE);
	}

 	token = strtok(line, " \t\r\n\a");

 	while(token != NULL){
		tokens[position] = token;
		position++;

		if(position >= bufsize){
	 		bufsize += 64;
			tokens = realloc(tokens, bufsize * sizeof(char*));
			if(!tokens) {
				fprintf(stderr, "myshell: allocation error\n");
				exit(EXIT_FAILURE);
			}
		}
		token = strtok(NULL, " \t\r\n\a");
	}

	tokens[position] = NULL;
	return tokens;
}

int myshell_execute(char **args)
{
	for(int i = 0; i < builtin_functions_total; i++){
		if(strcmp(args[0], builtin_functions_names[i]) == 0){
			 return (*builtin_functions[i])(args);
		}
	}

	pid_t pid, wpid;
	int status;

	pid = fork();

	if(pid == 0){
		if(execvp(args[0], args) == -1){
			perror("myshell");
		}
		exit(EXIT_FAILURE);
	}else if (pid < 0){
		perror("myshell");
	}else{
		do{
			wpid = waitpid(pid, &status, WUNTRACED);
		} while(!WIFEXITED(status) && !WIFSIGNALED(status));
	}

	return 0;
}

int main(){
	int status = 0;
	char *line;
	char **args;

	do{
		line = readline("myshell> ");

		if(line){
            add_history(line);
			args = myshell_split_line(line);
			status = myshell_execute(args);

			free(line);
			free(args);
		}

	} while(status == 0);

	return status;
}