/*
 * Stuff to mention next time:
 * 	includes and silly stuff
 * 	if(' ') is always true
 * 	space = 0 for else if case
 * 	permissions need to be set (show without doing this)
 *		newline in command line is a problem for execvp, not system
 *
 *		Next time:
 *			Actually call chdir()
 *			
 */ 


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


#define MAX_CMDLEN 10000
#define HISTORYLEN 100
char *prompt = " $: ";
char command[MAX_CMDLEN];
char cwd[1024] = "";
char *history;
int hspot = 0;

void eat_spaces(char **spot_pointer){
	while(*(*spot_pointer) == ' ')
		(*spot_pointer)++;
}

int main(){
	history = malloc(MAX_CMDLEN * HISTORYLEN);
	while(1){
		// Write the prompt and read a command
		write(2, cwd, strlen(cwd));
		write(2, prompt, strlen(prompt));
		size_t cmdlen = read(0, command, MAX_CMDLEN);
		if(!cmdlen){
			write(2, "\n", 1);
			goto done;
		}
		if(cmdlen == 1){
			strcpy(command, history + (hspot-1) * MAX_CMDLEN);
		} else {
			command[cmdlen] = 0;
			strcpy(history + hspot * MAX_CMDLEN, command);
			hspot++;
			hspot = hspot % HISTORYLEN;
		}
		
		// Check to see if the command requires action by us
		if(!strncmp("cd ", command, 3)){
			char* directory = command+3;
			while(directory[0] == ' ')
				directory++;
			directory[strlen(directory)-1] = 0;
			if(chdir(directory))
				perror(directory);
			else
				if(!getcwd(cwd, 1024))
					perror("getcwd");
			continue;
		}
		
		char quote = 0;
		char stdout_file[128];
		stdout_file[0] = 0;
		// *spot means the same thing as spot[0]
		for(char *spot = command; *spot && *spot != '\n'; spot++){
			if(*spot == '"') // TODO:  What if we're in single quotes instead of double?
				quote = !quote;
			if(*spot == '>' && !quote){
				char* redirfile;
				redirfile = spot+1;
				eat_spaces(&redirfile);
				char* filename_end = redirfile;
				while(*filename_end && *filename_end != ' ' && *filename_end != '\n') filename_end++;
				*filename_end = 0;
				filename_end[1] = 0;
				strcpy(stdout_file, redirfile);
				while(*redirfile){
					*redirfile = ' ';
					redirfile++;
				}
				*filename_end = ' ';
				*spot = ' ';
			}
		}
		pid_t pid = fork();
		if(pid){ // We're the parent
			wait(0);
		} else { // We're the child
			// setup redirection
			char *argv[128];
			argv[0] = command;
			int argv_total = 1;
			char space = 0;
			quote = 0;
			for(char *spot = command; *spot; spot++){
				if(*spot == '"') { // TODO:  What if we're in single quotes instead of double?
					if(*(spot-1) == '\\'){ // Then it's an escaped quote!
						for(char *c = spot; *c; c++)						
							*(c-1) = *c;
						spot--;
					} else {
						quote = !quote;
						*spot = 0;
						spot++;
					}
				}
				if((*spot == ' ' || *spot == '\n') && !quote){
					space = 1;
					*spot = 0;
				} else if(space) {
					space = 0;
					argv[argv_total] = spot;
					argv_total++;
				}
			}
			argv[argv_total] = 0;
			int stdout_fd = 0;
			if(stdout_file[0]){
				stdout_fd = open(stdout_file, O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR);
				dup2(stdout_fd, 1);
			} // otherwise we don't have to do any redirection
			execvp(command, argv);
			perror("execvp");
			if(stdout_fd) close(stdout_fd);
			return 0;
		}
	}
done:
	free(history);
	return 0;
}