/*
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * Copyright (C) 2024  Thomas Kolb
 */

#include <linux/if.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <arpa/inet.h>

#include <liquid/liquid.h>

#include <sys/poll.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <errno.h>

#include "layer2/ham64.h"
#include "utils.h"

#define LOGGER_MODULE_NAME "main"
#include "logger.h"
#include "jsonlogger.h"
#include "debug_structs.h"

#include "layer2/digipeater.h"

#include "layer2/tundev.h"

#include "config.h"

#define RESULT_CHECK(stmt) { \
	result_t res = stmt; \
	if(res != OK) { \
		LOG(LVL_FATAL, "Error %d in %s:%d!", res, __FILE__, __LINE__); \
		exit(1); \
	} \
}

#define BROADCAST_PORT 3737

static int  m_tunfd = -1;
static bool m_running = true;

static int m_bcast_sock = -1;

static uint64_t next_tx_switch_time = 0;

static rx_stats_t m_rx_stats;

static void signal_handler(int signal, siginfo_t *info, void *ctx)
{
	(void)signal;
	(void)info;
	(void)ctx;

	LOG(LVL_INFO, "\nGracefully shutting down on signal %d.", signal);

	m_running = false;
}

static void block_tx_for(unsigned offset_ms)
{
	next_tx_switch_time = get_hires_time() + HRTIME_MS(offset_ms);
}


static result_t transmit(const uint8_t *data, size_t len)
{
	result_t result = OK;

	struct sockaddr_in bcast_addr = {0};

	bcast_addr.sin_family = AF_INET;
	bcast_addr.sin_port = htons(BROADCAST_PORT);
	bcast_addr.sin_addr.s_addr = INADDR_BROADCAST;

	int ret = sendto(m_bcast_sock, data, len, 0, (struct sockaddr*)&bcast_addr, sizeof(bcast_addr));
	if(ret < 0) {
		LOG(LVL_ERR, "sendto: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	fprintf(stderr, "t");
	return result;
}


void rx_data_to_tun(const layer2_data_packet_t *data_packet)
{
	uint8_t tun_packet[4 + data_packet->payload_len];

	// flags
	tun_packet[0] = 0;
	tun_packet[1] = 0;

	switch(data_packet->payload_type) {
		case L2_PAYLOAD_TYPE_IPV6:
			*(uint16_t*)(tun_packet+2) = 0x86dd;
			break;
		case L2_PAYLOAD_TYPE_IPV4:
			*(uint16_t*)(tun_packet+2) = 0x0800;
			break;
		default:
			LOG(LVL_ERR, "Unsupported payload type: 0x%08x.", data_packet->payload_type);
			return;
	}

	memcpy(tun_packet+4, data_packet->payload, data_packet->payload_len);

	int ret = write(m_tunfd, tun_packet, sizeof(tun_packet));
	if(ret < 0) {
		LOG(LVL_ERR, "write(tun): %s", strerror(errno));
	}
}


int main(int argc, char **argv)
{
	// initialize the console logger
	logger_init();

	if(!jsonlogger_init("jsonlog.fifo")) {
		LOG(LVL_FATAL, "Could not initialize JSON logger.");
		return EXIT_FAILURE;
	}

	srand(get_hires_time());

	// ** Initialize **

	char devname[IFNAMSIZ] = "hamnet70";
	m_tunfd = tundev_open(devname);

	if(m_tunfd < 0) {
		return 1;
	}

	ham64_t my_address, peer_address;
	ham64_encode(MY_CALL, &my_address);
	ham64_encode(PEER_CALL, &peer_address);

	digipeater_ctx_t digipeater;
	RESULT_CHECK(digipeater_init(&digipeater, &my_address));

	// ** Set up signal handling

	struct sigaction term_action = {0};
	term_action.sa_sigaction = signal_handler;

	if(sigaction(SIGTERM, &term_action, NULL) < 0) {
		LOG(LVL_ERR, "sigaction: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	if(sigaction(SIGINT, &term_action, NULL) < 0) {
		LOG(LVL_ERR, "sigaction: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	// ** Set up UDP socket

	m_bcast_sock = socket(AF_INET, SOCK_DGRAM, 0);
	if(m_bcast_sock < 0) {
		LOG(LVL_ERR, "socket: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	int broadcastEnable=1;
	int ret = setsockopt(m_bcast_sock, SOL_SOCKET, SO_BROADCAST, &broadcastEnable, sizeof(broadcastEnable));
	if(ret < 0) {
		LOG(LVL_ERR, "setsockopt: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	struct sockaddr_in bind_addr = {0};

	bind_addr.sin_family = AF_INET;
	bind_addr.sin_port = htons(BROADCAST_PORT);
	bind_addr.sin_addr.s_addr = INADDR_ANY;

	ret = bind(m_bcast_sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr));
	if(ret < 0) {
		LOG(LVL_ERR, "bind: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	// ** Process packets **

	struct pollfd pfd_tun;
	memset(&pfd_tun, 0, sizeof(pfd_tun));

	pfd_tun.fd = m_tunfd;
	pfd_tun.events = POLLIN;

	struct pollfd pfd_bcast;
	memset(&pfd_bcast, 0, sizeof(pfd_bcast));

	pfd_bcast.fd = m_bcast_sock;
	pfd_bcast.events = POLLIN;

	uint64_t old = get_hires_time();
	size_t total_bytes = 0;
	uint64_t next_stats_print_time = old + HRTIME_MS(500);

	while(m_running) {
		RESULT_CHECK(digipeater_maintain(&digipeater));

		RESULT_CHECK(digipeater_fill_packet_queues_from_tundev(&digipeater, m_tunfd));

		// transmit anything available
		if(digipeater_can_transmit(&digipeater)) {
			// there is a packet to be (re)transmitted.

			LOG(LVL_DEBUG, "Starting new burst.");

			size_t burst_len = 0;

			// add packets to the burst until only 50000 samples remain free in the SDR buffer
			while(true) {
				uint8_t packet_buf[2048];
				size_t packet_size;

				bool end_burst;

				packet_size = digipeater_encode_next_packet(&digipeater,
						packet_buf, sizeof(packet_buf), &end_burst);

				if(packet_size == 0) {
					// no more packets available
					LOG(LVL_DEBUG, "Ending burst due to empty packet queue.");
					break;
				}

				LOG(LVL_DEBUG, "Adding packet with %d bytes to burst.", packet_size);

				burst_len++;
				RESULT_CHECK(transmit(packet_buf, packet_size));

				if(end_burst) {
					LOG(LVL_DEBUG, "Ending burst on request.");
					break;
				}
			}

			LOG(LVL_DEBUG, "Burst finished: %zd packets sent.", burst_len);
		}

		// make sure the receiver runs for a minimum amount of time
		block_tx_for(TX_SWITCH_BACKOFF_AFTER_RX_ON);

		// receive response
		while(get_hires_time() < next_tx_switch_time) {
			// ** Receive packets from the broadcast socket **

			int ret = poll(&pfd_bcast, 1, 10);
			if(ret < 0) {
				LOG(LVL_ERR, "poll: %s", strerror(errno));
				return EXIT_FAILURE;
			}

			if(ret == 0) {
				continue;
			}

			uint8_t packetbuf[65536];
			ret = recv(m_bcast_sock, packetbuf, sizeof(packetbuf), 0);
			if(ret < 0) {
				LOG(LVL_ERR, "recv: %s", strerror(errno));
				return EXIT_FAILURE;
			} else if(ret == 0) {
				LOG(LVL_ERR, "recv() returned zero.");
				return EXIT_FAILURE;
			}

			block_tx_for(TX_SWITCH_BACKOFF_END_OF_PACKET_MS);

			layer2_data_packet_t data_packet;

			result_t result = digipeater_handle_packet(&digipeater, packetbuf, ret, &data_packet);
			switch(result) {
				case OK:
					m_rx_stats.successful_decodes++;

					if(data_packet.payload_len != 0) {
						rx_data_to_tun(&data_packet);
					}
					break;

				case ERR_INTEGRITY:
					LOG(LVL_ERR, "Packet could not be decoded by Layer 2.");
					m_rx_stats.failed_decodes++;
					break;

				case ERR_SEQUENCE:
					LOG(LVL_ERR, "Packet not in the expected sequence.");
					break;

				default: // all other errors
					LOG(LVL_ERR, "layer2_rx_handle_packet() returned error code %u.", result);
					break;
			}

			total_bytes += ret;

			uint64_t new = get_hires_time();
			if(new >= next_stats_print_time) {
				double rate = total_bytes * 1e9 / (new - old);
				LOG(LVL_INFO, "\nEstimated rate: %.3f kB/s", rate / 1e3);
				LOG(LVL_INFO, "Receiver statistics:");
				LOG(LVL_INFO, "  Preambles found:    %8zd", m_rx_stats.preambles_found);
				LOG(LVL_INFO, "  Successful decodes: %8zd (%6.2f %%)",
						m_rx_stats.successful_decodes, m_rx_stats.successful_decodes * 100.0f / m_rx_stats.preambles_found);
				LOG(LVL_INFO, "  Header errors:      %8zd (%6.2f %%)",
						m_rx_stats.header_errors, m_rx_stats.header_errors * 100.0f / m_rx_stats.preambles_found);
				LOG(LVL_INFO, "  Failed decodes:     %8zd (%6.2f %%)",
						m_rx_stats.failed_decodes, m_rx_stats.failed_decodes * 100.0f / m_rx_stats.preambles_found);
				next_stats_print_time += HRTIME_MS(500);

				total_bytes = 0;
				old = new;
			}

			fprintf(stderr, "r");
		}
	}

	// ** Cleanup **

	close(m_bcast_sock);

	digipeater_destroy(&digipeater);

	jsonlogger_shutdown();

	LOG(LVL_INFO, "Done.");

	logger_shutdown();
}