#include <err.h>
#include <readline/history.h>
#include <readline/readline.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void handle_int() { /* handle ctrl-c */
	printf("\n");
	rl_on_new_line();
	rl_replace_line("", 0);
	rl_redisplay(); /* thanks James Taylor on Stack Overflow */
}

void usage(char **argv) {
	fprintf(stderr, "usage: %s [-a] command\n", argv[0]);
	exit(1);
}

int main(int argc, char *argv[]) {
	bool append = false;

	if (argc < 2 || argc > 3)
		usage(argv);
	if (argc > 1 && argv[1][0] == '-') {
		if (argv[1][1] != 'a' || argc < 3)
			usage(argv);
		append = true;
	}

	int size = strlen(argv[argc-1]) + 3 + 1;
	char *prompt = malloc(size);
	if (prompt == NULL) err(1, NULL);
	snprintf(prompt, size, "%s& ", argv[argc-1]);

	struct sigaction act = {0};
	act.sa_handler = handle_int;
	sigaction(SIGINT, &act, NULL);

	rl_clear_signals(); /* tell readline to ignore signals */

	while (true) {
		char *input = readline(prompt);

		if (input == NULL) /* ctrl-d */
			break;
		
		if (input[0] != '\0') add_history(input);

		int size = strlen(argv[argc-1]) + 1 + strlen(input) + 1;
		char *command = malloc(size);
		if (command == NULL) err(1, NULL);
		if (strncmp(input, "!cd ", 4) == 0) {
			if (chdir(input + 4) == -1)
				warn(NULL);
			goto next;
		}
		if (input[0] == '!')
			snprintf(command, size, "%s", input + 1);
		else if (append)
			snprintf(command, size, "%s %s", input, argv[argc-1]);
		else
			snprintf(command, size, "%s %s", argv[argc-1], input);

		system(command);

next:
		free(input);
		free(command);
	}

	free(prompt);

	return 0;
}