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

#include <liquid/liquid.h>

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

#include "utils.h"
#include "options.h"
#include "jsonlogger.h"
#include "debug_structs.h"

#include "layer1/tx.h"
#include "layer1/rx.h"

#include "layer2/tundev.h"

#include "sdr/sdr.h"

#include "config.h"

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

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

static double next_tx_switch_time = 0.0;

static rx_stats_t m_rx_stats;

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

	fprintf(stderr, "\nGracefully shutting down on signal %d.\n", signal);

	m_running = false;
}

static void block_tx_for(unsigned offset_ms)
{
	next_tx_switch_time = get_hires_time() + (double)offset_ms * 0.001;
}

void print_complex_array(const char *varname, float complex const *array, size_t len)
{
	fprintf(stderr, "%s=np.array([%f%+fj", varname, crealf(array[0]), cimagf(array[0]));
	for(size_t k = 1; k < len; k++) {
		fprintf(stderr, ", %f%+fj", crealf(array[k]), cimagf(array[k]));
	}
	fprintf(stderr, "])\n");
}


void hexdump(const uint8_t *data, size_t len)
{
	static const char lut[16] = "0123456789ABCDEF";
	static const size_t BYTES_PER_LINE = 16;

	size_t pos = 0;

	while(pos < len) {
		size_t bytes_in_line = len - pos;
		if(bytes_in_line > BYTES_PER_LINE) {
			bytes_in_line = BYTES_PER_LINE;
		}

		for(size_t i = 0; i < BYTES_PER_LINE; i++) {
			if(i >= bytes_in_line) {
				fputs("   ", stderr);
			} else {
				uint8_t byte = data[pos+i];

				fprintf(stderr, "%c%c ", lut[byte >> 4], lut[byte & 0x0F]);
			}
		}

		fputs("  ", stderr);

		for(size_t i = 0; i < bytes_in_line; i++) {
			uint8_t byte = data[pos+i];

			if(isprint(byte)) {
				putc(byte, stderr);
			} else {
				putc('.', stderr);
			}
		}

		putc('\n', stderr);
		pos += bytes_in_line;
	}
}


void cb_rx(rx_evt_t evt, uint8_t *packet_data, size_t packet_len)
{
	int ret;

	switch(evt)
	{
		case RX_EVT_CHECKSUM_ERROR:
			//fprintf(stderr, "Received a message of %zu bytes, but decoding failed.\n", packet_len);
			//fprintf(stderr, "=== FAILED PAYLOAD ===\n");
			//hexdump(packet_data, packet_len);
			//fprintf(stderr, "=======================\n");
			m_rx_stats.failed_decodes++;
			break;

		case RX_EVT_HEADER_ERROR:
			m_rx_stats.header_errors++;
			break;

		case RX_EVT_PACKET_RECEIVED:
			//fprintf(stderr, "A message of %zu bytes was decoded successfully.\n", packet_len);
			//fprintf(stderr, "=== DECODED PAYLOAD (%4zu bytes) ===\n", packet_len);
			//hexdump(packet_data, packet_len < 64 ? packet_len : 64);
			//fprintf(stderr, "====================================\n");

			m_rx_stats.successful_decodes++;

			block_tx_for(TX_SWITCH_BACKOFF_END_OF_PACKET_MS);

			ret = write(m_tunfd, packet_data, packet_len);
			if(ret < 0) {
				perror("write");
			}
			break;

		case RX_EVT_PREAMBLE_FOUND:
			//fprintf(stderr, "Found preamble!\n");
			block_tx_for(TX_SWITCH_BACKOFF_PREAMBLE_MS);
			m_rx_stats.preambles_found++;
			break;
	}

	jsonlogger_log_rx_stats(&m_rx_stats);
}


static int debug_fd;

static result_t transmit(sdr_ctx_t *sdr, const float complex *samples, size_t len)
{
	size_t to_transmit_rf = len * SDR_OVERSAMPLING;
	float complex rf_samples[to_transmit_rf];

	RESULT_CHECK(sdr_baseband_to_rf(sdr, samples, len, rf_samples, &to_transmit_rf));

	result_t result = sdr_transmit(sdr, rf_samples, to_transmit_rf, 100000);

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


int main(int argc, char **argv)
{
	layer1_tx_t tx;
	layer1_rx_t rx;

	sdr_ctx_t   sdr;

	int parsed_options = options_parse(argc, argv);
	fprintf(stderr, "%d options parsed.\n", parsed_options);
	if(parsed_options < 0) {
		return EXIT_FAILURE;
	}

	if(!jsonlogger_init("jsonlog.fifo")) {
		fprintf(stderr, "Could not initialize JSON logger.\n");
		return EXIT_FAILURE;
	}

	bool on_air = true;

	debug_fd = open("/tmp/dump.cf32", O_CREAT | O_WRONLY | O_TRUNC);

	// ** Initialize **

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

	if(m_tunfd < 0) {
		return 1;
	}

	RESULT_CHECK(sdr_init(&sdr));

	RESULT_CHECK(layer1_tx_init(&tx));
	RESULT_CHECK(layer1_rx_init(&rx, cb_rx));

	// ** Set up signal handling

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

	if(sigaction(SIGTERM, &term_action, NULL) < 0) {
		perror("sigaction");
		exit(EXIT_FAILURE);
	}

	if(sigaction(SIGINT, &term_action, NULL) < 0) {
		perror("sigaction");
		exit(EXIT_FAILURE);
	}

	// ** Process packets **

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

	pfd.fd = m_tunfd;
	pfd.events = POLLIN;

	// start in TX mode to work around SoapyHackRF not setting the correct frequency.
	RESULT_CHECK(sdr_start_tx(&sdr, 1));

	unsigned rx_retries = 0;

	double old = get_hires_time();
	size_t total_samples = 0;
	double next_stats_print_time = old + 0.5;

	while(m_running) {
		double now = get_hires_time();

		if((now > next_tx_switch_time) && (on_air || !layer1_rx_is_busy(&rx))) {
			int ret = poll(&pfd, 1, 0);
			if(ret < 0) {
				perror("poll");
				break;
			} else if(ret > 0) {
				// there is a packet to be read.

				// check free buffer space (50 ms required corresponding to 5000 baseband symbols)
				size_t buffer_free_space_samples = sdr_get_tx_buffer_free_space(&sdr);

				fprintf(stderr, "TX buffer free: %zu\n", buffer_free_space_samples);

				if(buffer_free_space_samples < 400000) { // sample count for 200 ms at 2 MHz
					// try again after a short delay
					fsleep(10e-3);
					continue;
				}

				uint8_t packetbuf[2048];
				ret = read(m_tunfd, packetbuf, sizeof(packetbuf));
				if(ret < 0) {
					perror("read");
					break;
				} else if(ret == 0) {
					// no more data
					break;
				}

				fprintf(stderr, "Transmitting packet with %d bytes.\n", ret);

				RESULT_CHECK(layer1_tx_reset(&tx));

				// ** Modulate packet **

				RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, packetbuf, ret));
				RESULT_CHECK(layer1_tx_finalize_burst(&tx));

				size_t burst_len = layer1_tx_get_sample_count(&tx);
				const float complex *whole_burst = layer1_tx_get_sample_data(&tx);

				dump_array_cf(whole_burst, burst_len, 1.0f, "/tmp/tx.cpx");

				// ensure that the buffer is full before TX is turned on to avoid transmitting empty buffers
				RESULT_CHECK(transmit(&sdr, whole_burst, burst_len));

				if(!on_air) {
					size_t buffer_used_samples = sdr_get_tx_buffer_used_space(&sdr);
					const size_t min_required_samples = 4*128*1024;

					int ret2 = poll(&pfd, 1, 0);
					if(ret2 < 0) {
						perror("poll");
						break;
					} else if(ret2 != 0 && (buffer_used_samples < min_required_samples)) {
						// enqueue more packets before starting TX
						fprintf(stderr, "Pre-buffering more packets: %zd / %zd samples.\n", buffer_used_samples, min_required_samples);
						continue;
					}

					fprintf(stderr, "RX -> TX\n");
					RESULT_CHECK(sdr_stop_rx(&sdr));

					// transmit packets on the frequency where the last packet was received.
					layer1_tx_set_carrier_frequency_offset(&tx, layer1_rx_get_coarse_carrier_frequency(&rx));

					RESULT_CHECK(sdr_start_tx(&sdr, burst_len * SDR_OVERSAMPLING));
				}

				on_air = true;
			} else if(on_air) { // ret == 0
				fprintf(stderr, "TX -> RX\n");
				RESULT_CHECK(sdr_flush_tx_buffer(&sdr));

				RESULT_CHECK(sdr_stop_tx(&sdr));
				RESULT_CHECK(sdr_start_rx(&sdr));
				on_air = false;

				block_tx_for(TX_SWITCH_BACKOFF_AFTER_RX_ON);
			}
		}

		if(!on_air) {
			// ** Receive signal **

			const size_t CHUNKSIZE_BB = 16384;
			const size_t CHUNKSIZE_RF = (CHUNKSIZE_BB * SDR_OVERSAMPLING);

			float complex rf_samples[CHUNKSIZE_RF];
			float complex bb_samples[CHUNKSIZE_BB];

			size_t n_rf_samples = CHUNKSIZE_RF;
			size_t n_bb_samples = CHUNKSIZE_BB;

			if(sdr_receive(&sdr, rf_samples, &n_rf_samples, 100000, SDR_OVERSAMPLING) != OK) {
				rx_retries++;
				fprintf(stderr, "sdr_receive() failed %d times.\n", rx_retries);
				if(rx_retries >= 3) {
					break;
				} else {
					continue;
				}
			}

			if(n_rf_samples == 0) {
				fsleep(1e-3);
				continue;
			}

			total_samples += n_rf_samples;

			double new = get_hires_time();
			if(new >= next_stats_print_time) {
				double rate = total_samples / (new - old);
				fprintf(stderr, "\nEstimated rate: %.3f MS/s\n", rate / 1e6);
				fprintf(stderr, "Receiver statistics:\n");
				fprintf(stderr, "  Preambles found:    %8zd\n", m_rx_stats.preambles_found);
				fprintf(stderr, "  Successful decodes: %8zd (%6.2f %%)\n",
						m_rx_stats.successful_decodes, m_rx_stats.successful_decodes * 100.0f / m_rx_stats.preambles_found);
				fprintf(stderr, "  Header errors:      %8zd (%6.2f %%)\n",
						m_rx_stats.header_errors, m_rx_stats.header_errors * 100.0f / m_rx_stats.preambles_found);
				fprintf(stderr, "  Failed decodes:     %8zd (%6.2f %%)\n",
						m_rx_stats.failed_decodes, m_rx_stats.failed_decodes * 100.0f / m_rx_stats.preambles_found);
				next_stats_print_time += 0.5;

				total_samples = 0;
				old = new;
			}

			rx_retries = 0;

			fprintf(stderr, "r");

			RESULT_CHECK(sdr_rf_to_baseband(&sdr, rf_samples, n_rf_samples, bb_samples, &n_bb_samples));

			RESULT_CHECK(layer1_rx_process(&rx, bb_samples, n_bb_samples));
		} else {
			rx_retries = 0;
		}
	}

	close(debug_fd);

	// ** Cleanup **

	layer1_tx_shutdown(&tx);
	layer1_rx_shutdown(&rx);

	sdr_destroy(&sdr);

	jsonlogger_shutdown();

	fprintf(stderr, "Done.\n");
}