/*-
 * Copyright (c) 2026, Mr. Goblin
 *
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided
 * with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include "cliflags.h"
#include "codes.h"

#define BTASKTD_HELP_STR \
	"Copyright (c) 2026, Mr. Goblin\n" \
	"btasktd - task tracking TCP-server\n" \
	"Usage: btasktd [-Vh] [-p port] [-u users]\n" \
	"For more info read the program's man page\n"

#define BTASKTD_VERSION_STR \
	"0.0.0"

#ifndef BTASKTD_QUEUE_LEN
#	define BTASKTD_QUEUE_LEN 16
#endif

#ifndef BTASKTD_CLIENT_BUF_SIZE
#	define BTASKTD_CLIENT_BUF_SIZE 4096
#endif

#ifndef BTASKTD_MAX_RESPONSE_BUF_SIZE
#	define BTASKTD_MAX_RESPONSE_BUF_SIZE 8192
#endif

#ifndef BTASKTD_RESPONSE_BUF_SIZE
#	define BTASKTD_RESPONSE_BUF_SIZE \
		((BTASKTD_MAX_RESPONSE_BUF_SIZE) - 256)
#endif


struct user {
	int fd;
	char buf[BTASKTD_CLIENT_BUF_SIZE];
	int bi; /* buf index */
};

/* BODY SHOULD BE EMPTY OR END WITH CRLF (\r\n, 13 10) */
struct response {
	int code;
	const char *body; /* for empty use NULL or "" */
};

struct btasktd {
	int fd;
	int users_cnt;
	struct user *users;
};

static void
fprint_help(FILE *f)
{
	fprintf(f, "%s", BTASKTD_HELP_STR);
}

static void
set_nonblock(int fd)
{
	int fflags = fcntl(fd, F_GETFL);
	fcntl(fd, F_SETFL, fflags|O_NONBLOCK);
}

static int
find_free_user(const struct user *arr, int count)
{
	int i;
	for (i = 0; i < count; i++) {
		if (-1 == arr[i].fd)
			return i;
	}
	return -1;
}

static void
reset_user_buf(struct user *pu)
{
	pu->bi = 0;
	memset(pu->buf, '\0', sizeof(pu->buf));
}

static void
reset_user(struct user *pu)
{
	pu->fd = -1;
	reset_user_buf(pu);
}

static void
send_to_client(int fd, const char *s)
{
	int len = strlen(s);
	int code = send(fd, s, len, 0);
	if (-1 == code)
		perror("send");
}

static void
send_response(int fd, struct response r)
{
	char buf[BTASKTD_MAX_RESPONSE_BUF_SIZE] = {0};
	if (NULL == r.body)
		r.body = "";
	snprintf(buf, sizeof(buf), "%s%s.\r\n", code_to_str(r.code),
		r.body);
	send_to_client(fd, buf);
}

static void
send_response_code(int fd, int code)
{
	struct response r = { CODE_200_OK, NULL };
	r.code = code;
	send_response(fd, r);
}

static void
handle_accept(struct btasktd *this)
{
	int idx;
	struct sockaddr_in user_addr = {0};
	socklen_t addrlen = sizeof(user_addr);
	int fd = accept(this->fd, (struct sockaddr*)&user_addr, &addrlen);
	if (-1 == fd) {
		perror("accept");
		return;
	}
	set_nonblock(fd);
	idx = find_free_user(this->users, this->users_cnt);
	if (-1 == idx) {
		send_response_code(fd, CODE_503_SERVICE_UNAVAILABLE);
		close(fd);
	}
	this->users[idx].fd = fd;
	this->users[idx].bi = 0;
}

static void
handle_timeout(struct btasktd *this)
{
}

static void
handle_buf(struct btasktd *this, int id, int should_send_response)
{
	struct response resp;
	struct user *pu = &(this->users[id]);
	char buf[BTASKTD_RESPONSE_BUF_SIZE] = {0};
	/* dummy yet */
	resp.code = CODE_200_OK;
	resp.body = "";
	if (should_send_response) {
		snprintf(buf, sizeof(buf), "%s", pu->buf);
#if 1
		send_to_client(pu->fd, buf);
#else
		resp.body = buf;
		send_response(pu->fd, resp);
#endif
	}
	reset_user_buf(pu);
}

static void
handle_user(struct btasktd *this, int id)
{
	int valread;
	struct user *pu = &(this->users[id]);
	unsigned sz = sizeof(pu->buf) - (pu->bi) - 1;
	valread = recv(pu->fd, pu->buf + pu->bi, sz, 0);
	if (0 == valread) {
		if (pu->bi > 0) {
			handle_buf(this, id, 0);
		}
		close(pu->fd);
		reset_user(pu);
		return;
	} else if (-1 == valread) {
		perror("recv");
		close(pu->fd);
		reset_user(pu);
		return;
	}
	handle_buf(this, id, 1);
}

int
main(int argc, char **argv)
{
	struct btasktd server;
	int server_fd, opt = 1, res, port, passed_flags = 1, users_cnt;
	int max_fd;
	struct user *users = NULL;
	int i;
	struct sockaddr_in addr = {0};
	struct int_flag_val int_res;
	struct bool_flag_val bool_res;
	fd_set readfds;

	bool_res = extract_bool_flag('V', argc, argv);
	if (fvr_ok == bool_res.code && bool_res.data) {
		printf("btasktd version %s\n", BTASKTD_VERSION_STR);
		return 0;
	}

	bool_res = extract_bool_flag('h', argc, argv);
	if (fvr_ok == bool_res.code && bool_res.data) {
		fprint_help(stdout);
		return 0;
	}

	int_res = extract_int_flag('p', argc, argv);
	switch (int_res.code) {
	case fvr_not_found:
#		ifdef BTASKTD_DEFAULT_PORT
			port = BTASKTD_DEFAULT_PORT;
#		else
			fprintf(stderr, "No port specified!\n");
			passed_flags = 0;
#		endif
		break;
	case fvr_ok:
		port = int_res.data;
		if (port > 0)
			break;
		/* fallthrough */
	case fvr_invalid:
		fprintf(stderr, "Invalid port!\n");
		return 1;
		break;
	}

	int_res = extract_int_flag('u', argc, argv);
	switch (int_res.code) {
	case fvr_not_found:
#		ifdef BTASKTD_DEFAULT_USERS_CNT
			users_cnt = BTASKTD_DEFAULT_USERS_CNT;
#		else
			fprintf(stderr, "No users count specified!\n");
			passed_flags = 0;
#		endif
		break;
	case fvr_ok:
		users_cnt = int_res.data;
		if (users_cnt > 0)
			break;
		/* fallthrough */
	case fvr_invalid:
		fprintf(stderr, "Invalid users count!\n");
		return 1;
		break;
	}

	if (!passed_flags) {
		fprintf(stderr, "-\n");
		fprint_help(stderr);
		return 1;
	}

	users = (struct user*)calloc(users_cnt, sizeof(struct user));
	if (NULL == users) {
		fprintf(stderr, "No memory!\n");
		return 1;
	}
	for (i = 0; i < users_cnt; i++) {
		users[i].fd = -1;
	}

	server_fd = socket(AF_INET, SOCK_STREAM, 0);
	if (server_fd < 0) {
		free(users);
		perror("socket");
		return 1;
	}
	addr.sin_family = AF_INET;
	addr.sin_port = htons(port);
	addr.sin_addr.s_addr = htonl(INADDR_ANY);
	res = setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR,
		&opt, sizeof(opt));
	if (0 != res) {
		close(server_fd);
		free(users);
		perror("setsockopt");
		return 1;
	}
	res = bind(server_fd, (struct sockaddr*)&addr, sizeof(addr));
	if (0 != res) {
		close(server_fd);
		free(users);
		perror("bind");
		return 1;
	}
	res = listen(server_fd, BTASKTD_QUEUE_LEN);
	if (0 != res) {
		close(server_fd);
		free(users);
		perror("listen");
		return 1;
	}

	set_nonblock(server_fd);

	server.fd = server_fd;
	server.users_cnt = users_cnt;
	server.users = users;
	printf("btaskt server btasktd started on port %d\n", port);

	for (;;) {
		FD_ZERO(&readfds);
		FD_SET(server_fd, &readfds);
		max_fd = server_fd;
		for (i = 0; i < users_cnt; i++) {
			if (-1 == users[i].fd)
				continue;
			FD_SET(users[i].fd, &readfds);
			if (users[i].fd > max_fd)
				max_fd = users[i].fd;
		}
		res = select(max_fd+1, &readfds, NULL, NULL, NULL);
		if (-1 == res) {
			if (EINTR == errno) {
				/* signal handler called */
			} else {
				perror("select");
			}
			continue;
		} else if (0 == res) {
			handle_timeout(&server);
			continue;
		}
		if (FD_ISSET(server_fd, &readfds))
			handle_accept(&server);
		for (i = 0; i < users_cnt; i++) {
			if (-1 == users[i].fd)
				continue;
			if (FD_ISSET(users[i].fd, &readfds))
				handle_user(&server, i);
		}
	}

	printf("btaskt server btasktd stopped\n");
	close(server_fd);
	free(users);
	return 0;
}