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

#include <dirent.h>
#include <limits.h>
#include <unistd.h>

/* get insert-before offset of first argument if any, argv end if none, or -1
 * if wd already defined */
int get_wd_off(int argc, char *argv[])
{
	int i;

	for (i = 0; i < argc; i++) {
		if (strcmp("--working-directory", argv[i]) == 0)
			return -1;
		if (argv[i][0] == '-')
			break;
	}

	return i;
}

/* walk through /proc looking for alacritty cmdline */
bool walk_proc(void)
{
	struct dirent *de;
	DIR *d = opendir("/proc");
	FILE *f;
	char path[PATH_MAX], cmd[PATH_MAX];

	if (d == NULL)
		abort();

	while ((de = readdir(d)) != NULL) {
		path[0] = '\0';
		strcat(path, "/proc/");
		strcat(path, de->d_name);
		strcat(path, "/cmdline");

		f = fopen(path, "r");

		if (f == NULL)
			continue;

		fscanf(f, "%s", cmd);

		if (strstr(cmd, "alacritty") != NULL) {
			fclose(f);
			closedir(d);
			return true;
		}

		fclose(f);
	}

	closedir(d);

	return false;
}

int main(int argc, char *argv[])
{
	/* two for --working-directory and cwd, two for msg and create-window, one
	 * for NULL */
	char *argvnew[argc + 5];
	char wd_arg_str[] = "--working-directory";
	char cwd[PATH_MAX];

	char alacritty[] = "alacritty";

	char *msg_create_window[] = {"msg", "create-window"};

	int i;
	int wd_off = get_wd_off(argc, argv);

	argvnew[0] = alacritty;

	/* insert --working-directory cwd if not already extant */
	if (wd_off == -1) {
		for (i = 1; i < argc; i++) {
			argvnew[i] = argv[i];
		}

		argvnew[i] = NULL;
	} else {
		getcwd(cwd, sizeof(cwd));

		for (i = 1; i < wd_off; i++)
			argvnew[i] = argv[i];

		argvnew[i] = wd_arg_str;
		argvnew[i + 1] = cwd;
		i += 2;

		for (; i < argc + 2; i++)
			argvnew[i] = argv[i - 2];

		argvnew[i] = NULL;
	}

	/* check if alacritty is running and, if so, insert msg create-window */
	if ( (argc < 2 || strcmp("msg", argv[1]) != 0) && walk_proc()) {
		/* shunt args up two to make room */
		for (i = argc + 4; i > 2; i--)
			argvnew[i] = argvnew[i - 2];

		argvnew[1] = msg_create_window[0];
		argvnew[2] = msg_create_window[1];
	}

	execv("/bin/alacritty", argvnew);
}