/* SPDX-FileCopyrightText: 2014, Nils Schneider <nils@nilsschneider.net> */
/* SPDX-License-Identifier: BSD-2-Clause */

#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>

void usage() {
	puts("Usage: gluon-neighbour-info [-h] [-s] [-l] [-c <count>] [-t <sec>] -d <dest> -p <port> -i <if0> -r <request>");
	puts("  -p <int>         UDP port (default: 1001)");
	puts("  -d <ip6>         destination address (unicast ip6 or multicast group, e.g. ff02:0:0:0:0:0:2:1001, default: ::1)");
	puts("  -i <string>      interface, e.g. eth0 ");
	puts("  -r <string>      request, e.g. nodeinfo");
	puts("  -t <sec>         timeout in seconds (default: 3)");
	puts("  -s <event>       output as server-sent events of type <event>");
	puts("                   or without type if <event> is the empty string");
	puts("  -c <count>       only wait for at most <count> replies (default: 1");
	puts("                   if -l is not given for unicast destination addresses)");
	puts("  -l               after timeout (or <count> replies if -c is given),");
	puts("                   send another request and loop forever");
	puts("  -h               this help\n");
}

void getclock(struct timeval *tv) {
	struct timespec ts;
	clock_gettime(CLOCK_MONOTONIC, &ts);
	tv->tv_sec = ts.tv_sec;
	tv->tv_usec = ts.tv_nsec / 1000;
}

/* Assumes a and b are normalized */
void tv_subtract (struct timeval *r, const struct timeval *a, const struct timeval *b) {
	r->tv_usec = a->tv_usec - b->tv_usec;
	r->tv_sec = a->tv_sec - b->tv_sec;

	if (r->tv_usec < 0) {
		r->tv_usec += 1000000;
		r->tv_sec -= 1;
	}
}

void resize_recvbuffer(char **recvbuffer, size_t *recvbuffer_len, size_t recvlen)
{
	free(*recvbuffer);
	*recvbuffer = malloc(recvlen);

	if (!(*recvbuffer)) {
		perror("Could not resize recvbuffer");
		exit(EXIT_FAILURE);
	}

	*recvbuffer_len = recvlen;
}

ssize_t recvtimeout(int socket, char **recvbuffer, size_t *recvbuffer_len,
		const struct timeval *timeout) {
	struct timeval now, timeout_left;
	ssize_t recvlen;

	getclock(&now);
	tv_subtract(&timeout_left, timeout, &now);

	if (timeout_left.tv_sec < 0)
		return -1;

	setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, &timeout_left, sizeof(timeout_left));

	recvlen = recv(socket, *recvbuffer, 0, MSG_PEEK | MSG_TRUNC);
	if (recvlen < 0)
		return recvlen;

	if (recvlen > *recvbuffer_len)
		resize_recvbuffer(recvbuffer, recvbuffer_len, recvlen);

	return recv(socket, *recvbuffer, *recvbuffer_len, 0);
}

int request(const int sock, char **recvbuffer, size_t *recvbuffer_len,
		const struct sockaddr_in6 *client_addr, const char *request,
		const char *sse, double timeout, unsigned int max_count) {
	ssize_t ret;
	unsigned int count = 0;

	ret = sendto(sock, request, strlen(request), 0, (struct sockaddr *)client_addr, sizeof(struct sockaddr_in6));

	if (ret < 0) {
		perror("Error in sendto()");
		free(*recvbuffer);
		exit(EXIT_FAILURE);
	}

	struct timeval tv_timeout;
	getclock(&tv_timeout);

	tv_timeout.tv_sec += (int) timeout;
	tv_timeout.tv_usec += ((int) (timeout * 1000000)) % 1000000;
	if (tv_timeout.tv_usec >= 1000000) {
		tv_timeout.tv_usec -= 1000000;
		tv_timeout.tv_sec += 1;
	}

	do {
		ret = recvtimeout(sock, recvbuffer, recvbuffer_len, &tv_timeout);

		if (ret < 0)
			break;

		if (sse) {
			if (sse[0] != '\0')
				fprintf(stdout, "event: %s\n", sse);
			fputs("data: ", stdout);
		}

		fwrite(*recvbuffer, sizeof(char), ret, stdout);

		if (sse)
			fputs("\n\n", stdout);
		else
			fputs("\n", stdout);

		fflush(stdout);
		count++;
	} while (max_count == 0 || count < max_count);

	if ((max_count == 0 && count == 0) || count < max_count)
		return EXIT_FAILURE;
	else
		return EXIT_SUCCESS;
}

int main(int argc, char **argv) {
	int sock;
	struct sockaddr_in6 client_addr = {};
	char *request_string = NULL;
	char *recvbuffer = NULL;
	size_t recvbuffer_len = 0;

	sock = socket(PF_INET6, SOCK_DGRAM, 0);

	if (sock < 0) {
		perror("creating socket");
		exit(EXIT_FAILURE);
	}

	client_addr.sin6_addr = in6addr_loopback;
	client_addr.sin6_port = htons(1001);
	client_addr.sin6_family = AF_INET6;

	opterr = 0;

	int max_count = 0;
	double timeout = 3.0;
	char *sse = NULL;
	bool loop = false;
	int ret = false;

	int c;
	while ((c = getopt(argc, argv, "p:d:r:i:t:s:c:lh")) != -1)
		switch (c) {
		case 'p':
			client_addr.sin6_port = htons(atoi(optarg));
			break;
		case 'd':
			if (!inet_pton(AF_INET6, optarg, &client_addr.sin6_addr)) {
				fprintf(stderr, "Invalid destination address\n");
				exit(EXIT_FAILURE);
			}
			break;
		case 'i':
			client_addr.sin6_scope_id = if_nametoindex(optarg);
			if (client_addr.sin6_scope_id == 0) {
				perror("Can not use interface");
				exit(EXIT_FAILURE);
			}
			break;
		case 'r':
			request_string = optarg;
			break;
		case 't':
			timeout = atof(optarg);
			if (timeout < 0) {
				perror("Negative timeout not supported");
				exit(EXIT_FAILURE);
			}
			break;
		case 's':
			sse = optarg;
			break;
		case 'l':
			loop = true;
			break;
		case 'c':
			max_count = atoi(optarg);
			if (max_count < 0) {
				perror("Negative count not supported");
				exit(EXIT_FAILURE);
			}
			break;
		case 'h':
			usage();
			exit(EXIT_SUCCESS);
			break;
		default:
			fprintf(stderr, "Invalid parameter %c\n", optopt);
			exit(EXIT_FAILURE);
		}

	if (request_string == NULL) {
		fprintf(stderr, "No request string supplied\n");
		exit(EXIT_FAILURE);
	}

	if (client_addr.sin6_port == htons(0)) {
		fprintf(stderr, "No port supplied\n");
		exit(EXIT_FAILURE);
	}

	if (IN6_IS_ADDR_UNSPECIFIED(&client_addr.sin6_addr)) {
		fprintf(stderr, "No destination address supplied\n");
		exit(EXIT_FAILURE);
	}

	if (client_addr.sin6_scope_id) {
		if (setsockopt(
			sock, IPPROTO_IPV6, IPV6_MULTICAST_IF,
			&client_addr.sin6_scope_id, sizeof(client_addr.sin6_scope_id)
		) < 0) {
			perror("setsockopt");
			exit(EXIT_FAILURE);
		}
	}

	if (!loop && !IN6_IS_ADDR_MULTICAST(&client_addr.sin6_addr)) {
		max_count=1;
	}

	if (sse) {
		fputs("Content-Type: text/event-stream\n\n", stdout);
		fflush(stdout);
	}

	resize_recvbuffer(&recvbuffer, &recvbuffer_len, 8192);

	do {
		ret = request(sock, &recvbuffer, &recvbuffer_len, &client_addr,
				request_string, sse, timeout, max_count);
	} while(loop);

	if (sse)
		fputs("event: eot\ndata: null\n\n", stdout);

	free(recvbuffer);
	return ret;
}