#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/un.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <errno.h>
#include <sys/poll.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <signal.h>
#include <netdb.h>
#include <fcntl.h>
#include "libtel.h"

#define CALL_BUF_SIZE 16

// config

struct config {
	struct sockaddr *addr;
	socklen_t addr_len;
	int connect_timeout;
};

struct in_call {
	int fd;
	union tel_sa_any addr;
};

//
//  Call buffer operations
//

struct call_buf {
	struct in_call buf[CALL_BUF_SIZE];
	size_t len;
};

void call_buf_init(struct call_buf *buf) {
	buf->len = 0;
}

void call_buf_add(struct call_buf *buf, struct in_call call) {
	// if buffer is full, remove and close tail element
	if(buf->len == CALL_BUF_SIZE) {
		struct in_call last = buf->buf[0];
		close(last.fd);
		memmove(buf->buf, buf->buf + 1, CALL_BUF_SIZE - 1);
	}
	buf->buf[buf->len++] = call;
}

struct in_call call_buf_remove(struct call_buf *buf, int n) {
	struct in_call call = buf->buf[n];
	buf->len--;
	buf->buf[n] = buf->buf[buf->len];
	return call;
}

int call_buf_search(struct call_buf *buf, union tel_sa_any *callinfo) {
	for(size_t i = 0; i < buf->len; i++) {
		if(tel_sa_any_eq(&buf->buf[i].addr, callinfo)) {
			return i;
		}
	}
	return -1;
}

//
//  Socket initialization
//

int init_client_sock(char *path) {
	int res;
	int sock;
	struct sockaddr_un addr;

	memset(&addr, 0, sizeof(struct sockaddr_un));
	addr.sun_family = AF_UNIX;
	strncpy(addr.sun_path, path, sizeof(addr.sun_path) - 1);

	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if(sock < 0) {
		perror("error opening client socket");
		exit(1);
	}

	unlink(path);

	res = bind(sock, (const struct sockaddr *)&addr, sizeof(struct sockaddr_un));
	if(res < 0) {
		perror("error binding to client socket");
		exit(1);
	}

	res = listen(sock, 16);
	if(res < 0) {
		perror("error listening on client socket");
		exit(1);
	}

	printf("client socket listening at %s\n", path);

	return sock;
}

int init_net_sock(struct sockaddr *addr, socklen_t addr_len) {
	int res;
	int sock;

	sock = socket(addr->sa_family, SOCK_STREAM, 0);
	if(sock < 0) {
		perror("error opening network socket");
		exit(1);
	}
	
	int enable = 1;

	res = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
	if(res < 0) {
		perror("failed to set socket option SO_REUSEADDR");
		exit(1);
	}

	res = setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &enable, sizeof(int));
	if(res < 0) {
		perror("failed to set socket option SO_REUSEPORT");
		exit(1);
	}

	res = bind(sock, addr, addr_len);
	if(res < 0) {
		perror("error binding to network socket");
		exit(1);
	}

	res = listen(sock, 16);
	if(res < 0) {
		perror("error listening on network socket");
		exit(1);
	}
	
	char buf[TEL_STRADDRLEN];
	res = tel_straddr(addr, buf);
	if(res >= 0) {
		printf("network socket listening at %s\n", buf);
	}

	return sock;
}

void client_pickup(struct call_buf *call_buf, int stream) {
	int res;
	
	union tel_sa_any remote_addr;
	socklen_t remote_addr_len = sizeof(union tel_sa_any);
	res = tel_read_sockaddr(stream, &remote_addr, &remote_addr_len);

	int idx = call_buf_search(call_buf, &remote_addr);
	if(idx < 0) {
		tel_write_u32(stream, MSG_NONE);
		return;
	}

	struct in_call call = call_buf_remove(call_buf, idx);
	int fd = call.fd;

	tel_write_u32(stream, MSG_SOCKET);

	res = tel_write_fd(stream, fd);
	if(res < 0) { 
		tel_write_err(stream, strerror(errno));
	};
	close(fd);
	return;
}

void client_call(int stream, struct config cfg) {
	int res;

	union tel_sa_any remote_addr;
	socklen_t remote_addr_len = sizeof(union tel_sa_any);
	res = tel_read_sockaddr(stream, &remote_addr, &remote_addr_len);
	if(res < 0) goto err_noclose;

	char buf[TEL_STRADDRLEN];
	res = tel_straddr((struct sockaddr *)&remote_addr, buf);
	if(res >= 0) {
		printf("client calling %s...\n", buf);
	}

	int sock = socket(remote_addr.v4.sin_family, SOCK_STREAM, 0);
	if(res < 0) goto err_noclose;

	int enable = 1;

	res = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
	if(res < 0) goto err;

	res = setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &enable, sizeof(int));
	if(res < 0) goto err;

	res = bind(sock, cfg.addr, cfg.addr_len);
	if(res < 0) goto err;

	int sock_flags = fcntl(sock, F_GETFL);
	fcntl(sock, F_SETFL, sock_flags | O_NONBLOCK);

	struct pollfd pollfds[1];
	pollfds[0].fd = sock;
	pollfds[0].events = POLLOUT;

	res = connect(sock, (struct sockaddr *)&remote_addr, remote_addr_len);
	if(res < 0 && errno != EINPROGRESS) goto err;

	res = poll(pollfds, 1, cfg.connect_timeout);
	if(res < 0) goto err;
	if(res == 0) {
		printf("error making call: timed out\n");
		tel_write_err(stream, "timed out");
		close(sock);
		return;
	}
	if(pollfds[0].revents & POLLERR) {
		printf("error making call: timed out\n");
		tel_write_err(stream, "unknown error connecting");
		close(sock);
		return;
	}

	fcntl(sock, F_SETFL, sock_flags);

	res = tel_write_u32(stream, MSG_SOCKET);
	if(res < 0) goto err;

	res = tel_write_fd(stream, sock);
	if(res < 0) goto err;

	printf("call made successfully\n");
	close(sock);
	return;

err_noclose:
	printf("error making call: %s\n", strerror(errno));
	tel_write_err(stream, strerror(errno));
	return;

err:
	printf("error making call: %s\n", strerror(errno));
	tel_write_err(stream, strerror(errno));
	close(sock);
	return;
}

void accept_client(struct call_buf *call_buf, int fd, struct config cfg) {
	int stream = accept(fd, NULL, 0);
	if(stream < 0) {
		perror("error accepting client connection");
		exit(1);
	}

	printf("accepted client connection\n");

	enum tel_message msg;
	int rc = tel_read_u32(stream, &msg);
	if(rc < 0) {
		tel_write_err(stream, strerror(errno));
		return;
	}

	switch(msg) {
		case MSG_PICKUP:
			client_pickup(call_buf, stream);
			break;
		case MSG_CALL:
			client_call(stream, cfg);
			break;
		default:
			tel_write_err(stream, "invalid command");
			break;
	}

	close(stream);
}

//
//  Processing network connections
//

void accept_net(struct call_buf *call_buf, int fd) {
	union tel_sa_any cli_addr;
	socklen_t addr_len = sizeof(union tel_sa_any);

	int stream = accept(fd, (struct sockaddr *)&cli_addr, &addr_len);
	if(stream < 0) {
		perror("error accepting network connection");
		exit(1);
	}

	char buf[TEL_STRADDRLEN];
	int res = tel_straddr((struct sockaddr *)&cli_addr, buf);
	if(res >= 0) {
		printf("accepted connection: %s\n", buf);
	}


	struct in_call call;
	call.fd = stream;
	call.addr = cli_addr;
	call_buf_add(call_buf, call);
}

//
//  Main
//

void run(struct config cfg) {
	char trash[4096];

	int client_sock = init_client_sock("/tmp/tel.sock");
	int net_sock = init_net_sock(cfg.addr, cfg.addr_len);

	struct call_buf call_buf;
	call_buf_init(&call_buf);

	struct pollfd fds[2 + CALL_BUF_SIZE];
	fds[0].fd = client_sock;
	fds[0].events = POLLIN;
	fds[1].fd = net_sock;
	fds[1].events = POLLIN;

	while(1) {
		int fd_count = 2 + call_buf.len;
		for(size_t i = 0; i < call_buf.len; i++) {
			fds[i + 2].fd = call_buf.buf[i].fd;
			fds[i + 2].events = POLLIN | POLLERR | POLLHUP;
		}
		int res = poll(fds, fd_count, -1);
		if(res < 0) {
			perror("error polling");
			exit(1);
		}

		if(fds[0].revents & POLLIN) {
			accept_client(&call_buf, fds[0].fd, cfg);
		} 
		if(fds[1].revents & POLLIN) {
			accept_net(&call_buf, fds[1].fd);
		}
		for(int i = 2; i < fd_count; i++) {
			if(fds[i].revents & (POLLHUP | POLLHUP)) {
				call_buf_remove(&call_buf, i-2);
				close(fds[i].fd);
			}
			if(fds[i].revents & POLLIN) {
				read(fds[i].fd, trash, 4096);
			}
		}
	}
}

int main(int argc, char **argv) {
	if(argc < 1) return 1;
	if(argc < 3) {
		fprintf(stderr, "usage: %s <addr> <port>\n", argv[0]);
		exit(1);
	}

	struct config cfg;
	cfg.connect_timeout = 1000;

	// disable SIGPIPE handler
	struct sigaction sa;
	sa.sa_handler = SIG_IGN;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = 0;
	sigaction(SIGPIPE, &sa, NULL);

	// get address from ip/port
	char *ip = argv[1];
	char *port = argv[2];

	int res = tel_get_addr(ip, port, &cfg.addr, &cfg.addr_len);
	if(res != 0) {
		fprintf(stderr, "error: %s\n", gai_strerror(res));
		exit(1);
	}

	// run application
	run(cfg);
	return 0;
}