/*
 * Copyright (c) Camden Dixie O'Brien
 * SPDX-License-Identifier: AGPL-3.0-only
 */

#define _POSIX_C_SOURCE 199309L

#include <dlfcn.h>
#include <errno.h>
#include <poll.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/inotify.h>
#include <time.h>
#include <unistd.h>

#define LIBFN "libmod.so"

typedef const char *(*getmsg_t)(void);

static void *mod = NULL;
static getmsg_t getmsg = NULL;

static void loadmod(void)
{
	if (mod)
		dlclose(mod);
	mod = dlopen(LIBFN, RTLD_NOW);
	if (!mod) {
		fprintf(stderr, "ERROR(%s:%d) %s\n", __FILE__, __LINE__, dlerror());
		exit(1);
	}
	getmsg = (getmsg_t)dlsym(mod, "getmsg");
	if (!getmsg) {
		fprintf(stderr, "ERROR(%s:%d) %s\n", __FILE__, __LINE__, dlerror());
		exit(1);
	}
}

int main(void)
{
	loadmod();

	int fd = inotify_init();
	if (fd < 0) {
		fprintf(
		    stderr, "ERROR(%s:%d) %s\n", __FILE__, __LINE__,
		    strerror(errno));
		exit(1);
	}
	int wd = inotify_add_watch(fd, "build", IN_MODIFY);
	if (wd < 0) {
		fprintf(
		    stderr, "ERROR(%s:%d) %s\n", __FILE__, __LINE__,
		    strerror(errno));
		exit(1);
	}
	struct pollfd pfd = { .fd = fd, .events = POLLIN };

	const struct timespec pause = { .tv_nsec = 100000000 };
	while (1) {
		int polln = poll(&pfd, 1, 10);
		if (-1 == polln) {
			fprintf(
			    stderr, "ERROR(%s:%d) %s\n", __FILE__, __LINE__,
			    strerror(errno));
			exit(1);
		} else if (polln > 0 && pfd.revents & POLLIN) {
			static char buf[4096]
			    __attribute__((aligned(__alignof__(struct inotify_event))));
			const struct inotify_event *evt;
			ssize_t i = 0, len = read(fd, buf, sizeof(buf));
			bool reload = false;
			while (i < len) {
				evt = (struct inotify_event *)&buf[i];
				if (strcmp(LIBFN, evt->name) == 0)
					reload = true;
				i += sizeof(struct inotify_event) + evt->len;
			}
			if (reload)
				loadmod();
		}

		printf("\33[2K\r%s", getmsg());
		fflush(stdout);
		nanosleep(&pause, NULL);
	}

	return 0;
}