#include<stdio.h>
#include<readline/readline.h>
#include<readline/history.h>
#include<unistd.h>
#include<signal.h>
#include<stdlib.h>
#include<sys/wait.h>
#include<fcntl.h>

void signal_handler(int sigal){
	// We don't actually want to do anything here right now
}

char *remove_whitespace(char *input){
	while(isspace(*input))
		input++;
	char *end = input + strlen(input);
	while(isspace(*(--end)))
		*end = 0;
	return input;
}

char **split(char *tosplit){
	size_t length = strlen(tosplit);
	char **lines = (char**)malloc(100 * sizeof(char*));
	size_t line = 0;
	size_t lines_space_left = 100;
	lines[0] = tosplit;
	for(size_t i = 0; i < length; i++){
		if(isspace(tosplit[i])){
			while(isspace(tosplit[i + 1]))
				i++;
			line++;
			tosplit[i] = 0;
			lines[line] = &tosplit[i] + 1; // If we have an extra one, revise this
			lines_space_left -= 1;
		}
		if(!lines_space_left){
			lines = realloc(lines, (line + 100) * sizeof(char*));
			lines_space_left += 100;
		}
	}
	return lines;
}

/* We'll expect that pipes, variables, etc. have already been processed */
void execute_command(char *command, int input_fd, int output_fd, int err_fd){
	/* What if it's a shell builtin? */
	/* Parsing for cd lacks good support for multiple or extranious spaces */
	if(!strcmp(command, "cd")){ // Change to home directory
		chdir(getenv("HOME")); // I'll just leave out error handling
		return; // Might have to close some fds, etc
	} else if(!strncmp(command, "cd ", 3)){
		if(chdir(command + 3))
			perror(command + 3);
		return;
	}

	/* It's not a shell builtin */
	pid_t pid = fork();
	// In the parent, pid is the pid of the child
	if(pid){ // We're the parent
		wait(0);
	} else { // In the child, pid is 0
		/* Assemble argv here */
		char ** argv = split(command);
		dup2(output_fd, 1);	
		execvp(argv[0], argv);
	}
}

void process_line(char *line){
	/* Process the line and get it ready to execute (handle >, etc) */
	char *gt_place = strchr(line, '>');
	if(gt_place) {
		*gt_place = ' ';
		while(*(++gt_place) == ' ');
		char *filename_end = gt_place;
		while(*filename_end && isspace(*filename_end))
			filename_end++;
		*filename_end = 0;
		int output_fd = open(gt_place, O_WRONLY | O_CREAT | O_TRUNC);
		while(gt_place < filename_end){
			*gt_place = ' ';
			++gt_place;
		}
		*filename_end = ' ';
		execute_command(remove_whitespace(line), 0, output_fd, 2);
		close(output_fd);
	} else {
		execute_command(line, 0, 1, 2);
	}
	free(line);
}

int main(){
	char *line;
	struct sigaction sa;
	sa.sa_handler = signal_handler;
	sigaction(SIGINT, &sa, 0);
	
	while(1){
		line = readline("prompt>> ");
		if(!line) {
			printf("Line was empty, leaving\n");
			break;
		}
		if(!line[0])
			continue;
		add_history(line);
		
		/* After this:  We do whatever the shell was actually supposed to do! */
		process_line(line);
	}
}