/*
 * Copyright 2011 Marian Ohligs, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/wait.h>
#undef errno
extern int errno;

void showlogo() {
	printf("\n\n");
	printf("================================================================================\n");
	printf("                               m(etalsvm)shell\n\n");
	printf("================================================================================\n");
}

void help() {
	printf("possible commands: \n");
	printf("exit > exit shell \n");
}

#define MAXARGS 16

#define ST_WHITE 0
#define ST_ARG 1

char** splitargs(char* args) {
	static char* ret[MAXARGS+1];
	int i = 0;
	int state = ST_WHITE;
	while (*args != '\0') {
		if (state == ST_WHITE) {
			if (!isspace(*args)) {
				ret[i++] = args;
				if (i == MAXARGS)
					break;
				state = ST_ARG;
			}
		}
		else {
			if (isspace(*args)) {
				*args = '\0';
				state = ST_WHITE;
			}
		}
		args++;
	}
	ret[i] = NULL;

	return ret;
}

int main(int argc, char** argv)
{
	char  commandline[1024];
	char* command;

	int size = 0, status = 0;
	pid_t pid;
	system("clear");
	showlogo();
	while(1) {
		char** newargv;
		char*  newenv[] = {"USER=root", "PATH=/bin:/sbin:/usr/bin", "PWD=/", "TEMP=/tmp", NULL};
		
		printf("mshell> ");
		gets(commandline);
		
		newargv = splitargs(commandline);
		command = newargv[0];
		
		if(command == NULL) {
			continue;
		}
		if(!strcmp(command, "exit")) {
			return 0;
		}
		if(!strcmp(command, "help")) {
			help();
		} else {
			char path[128];
			sprintf(path, "/bin/%s", command);
			pid = fork();
			if (pid == 0) { //child
				status = execve(path, newargv, newenv);
				if (status)
					printf("mshell: %s: command not found\n", path);
				return errno;
			} else {
				wait(&status);
			}
		}	
	}
	return errno;
}