/*
 * Copyright (c) 2019 Manivannan Sadhasivam
 * Copyright (c) 2020 Grinn
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <drivers/gpio.h>
#include <drivers/lora.h>
#include <logging/log.h>
#include <sys/atomic.h>
#include <zephyr.h>

/* LoRaMac-node specific includes */
#include <radio.h>

#include "sx12xx_common.h"

#define STATE_FREE      0
#define STATE_BUSY      1
#define STATE_CLEANUP   2

LOG_MODULE_REGISTER(sx12xx_common, CONFIG_LORA_LOG_LEVEL);

struct sx12xx_rx_params {
	uint8_t *buf;
	uint8_t *size;
	int16_t *rssi;
	int8_t *snr;
};

static struct sx12xx_data {
	const struct device *dev;
	struct k_poll_signal *operation_done;
	lora_recv_cb async_rx_cb;
	RadioEvents_t events;
	struct lora_modem_config tx_cfg;
	atomic_t modem_usage;
	struct sx12xx_rx_params rx_params;
} dev_data;

int __sx12xx_configure_pin(const struct gpio_dt_spec *gpio, gpio_flags_t flags)
{
	int err;

	if (!device_is_ready(gpio->port)) {
		LOG_ERR("GPIO device not ready %s", gpio->port->name);
		return -ENODEV;
	}

	err = gpio_pin_configure_dt(gpio, flags);
	if (err) {
		LOG_ERR("Cannot configure gpio %s %d: %d", gpio->port->name,
			gpio->pin, err);
		return err;
	}

	return 0;
}

/**
 * @brief Attempt to acquire the modem for operations
 *
 * @param data common sx12xx data struct
 *
 * @retval true if modem was acquired
 * @retval false otherwise
 */
static inline bool modem_acquire(struct sx12xx_data *data)
{
	return atomic_cas(&data->modem_usage, STATE_FREE, STATE_BUSY);
}

/**
 * @brief Safely release the modem from any context
 *
 * This function can be called from any context and guarantees that the
 * release operations will only be run once.
 *
 * @param data common sx12xx data struct
 *
 * @retval true if modem was released by this function
 * @retval false otherwise
 */
static bool modem_release(struct sx12xx_data *data)
{
	/* Increment atomic so both acquire and release will fail */
	if (!atomic_cas(&data->modem_usage, STATE_BUSY, STATE_CLEANUP)) {
		return false;
	}
	/* Put radio back into sleep mode */
	Radio.Sleep();
	/* Completely release modem */
	data->operation_done = NULL;
	atomic_clear(&data->modem_usage);
	return true;
}

static void sx12xx_ev_rx_done(uint8_t *payload, uint16_t size, int16_t rssi,
			      int8_t snr)
{
	struct k_poll_signal *sig = dev_data.operation_done;

	/* Receiving in asynchronous mode */
	if (dev_data.async_rx_cb) {
		/* Start receiving again */
		Radio.Rx(0);
		/* Run the callback */
		dev_data.async_rx_cb(dev_data.dev, payload, size, rssi, snr);
		/* Don't run the synchronous code */
		return;
	}

	/* Manually release the modem instead of just calling modem_release
	 * as we need to perform cleanup operations while still ensuring
	 * others can't use the modem.
	 */
	if (!atomic_cas(&dev_data.modem_usage, STATE_BUSY, STATE_CLEANUP)) {
		return;
	}
	/* We can make two observations here:
	 *  1. lora_recv hasn't already exited due to a timeout.
	 *         (modem_release would have been successfully called)
	 *  2. If the k_poll in lora_recv times out before we raise the signal,
	 *     but while this code is running, it will block on the
	 *     signal again.
	 * This lets us guarantee that the operation_done signal and pointers
	 * in rx_params are always valid in this function.
	 */

	/* Store actual size */
	if (size < *dev_data.rx_params.size) {
		*dev_data.rx_params.size = size;
	}
	/* Copy received data to output buffer */
	memcpy(dev_data.rx_params.buf, payload,
	       *dev_data.rx_params.size);
	/* Output RSSI and SNR */
	if (dev_data.rx_params.rssi) {
		*dev_data.rx_params.rssi = rssi;
	}
	if (dev_data.rx_params.snr) {
		*dev_data.rx_params.snr = snr;
	}
	/* Put radio back into sleep mode */
	Radio.Sleep();
	/* Completely release modem */
	dev_data.operation_done = NULL;
	atomic_clear(&dev_data.modem_usage);
	/* Notify caller RX is complete */
	k_poll_signal_raise(sig, 0);
}

static void sx12xx_ev_tx_done(void)
{
	struct k_poll_signal *sig = dev_data.operation_done;

	if (modem_release(&dev_data)) {
		/* Raise signal if provided */
		if (sig) {
			k_poll_signal_raise(sig, 0);
		}
	}
}

int sx12xx_lora_send(const struct device *dev, uint8_t *data,
		     uint32_t data_len)
{
	struct k_poll_signal done = K_POLL_SIGNAL_INITIALIZER(done);
	struct k_poll_event evt = K_POLL_EVENT_INITIALIZER(
		K_POLL_TYPE_SIGNAL,
		K_POLL_MODE_NOTIFY_ONLY,
		&done);
	uint32_t air_time;
	int ret;

	/* Validate that we have a TX configuration */
	if (!dev_data.tx_cfg.frequency) {
		return -EINVAL;
	}

	ret = sx12xx_lora_send_async(dev, data, data_len, &done);
	if (ret < 0) {
		return ret;
	}

	/* Calculate expected airtime of the packet */
	air_time = Radio.TimeOnAir(MODEM_LORA,
				   dev_data.tx_cfg.bandwidth,
				   dev_data.tx_cfg.datarate,
				   dev_data.tx_cfg.coding_rate,
				   dev_data.tx_cfg.preamble_len,
				   0, data_len, true);
	LOG_DBG("Expected air time of %d bytes = %dms", data_len, air_time);

	/* Wait for the packet to finish transmitting.
	 * Use twice the tx duration to ensure that we are actually detecting
	 * a failed transmission, and not some minor timing variation between
	 * modem and driver.
	 */
	ret = k_poll(&evt, 1, K_MSEC(2 * air_time));
	if (ret < 0) {
		LOG_ERR("Packet transmission failed!");
		if (!modem_release(&dev_data)) {
			/* TX done interrupt is currently running */
			k_poll(&evt, 1, K_FOREVER);
		}
	}
	return 0;
}

int sx12xx_lora_send_async(const struct device *dev, uint8_t *data,
			   uint32_t data_len, struct k_poll_signal *async)
{
	/* Ensure available, freed by sx12xx_ev_tx_done */
	if (!modem_acquire(&dev_data)) {
		return -EBUSY;
	}

	/* Store signal */
	dev_data.operation_done = async;

	Radio.SetMaxPayloadLength(MODEM_LORA, data_len);

	Radio.Send(data, data_len);

	return 0;
}

int sx12xx_lora_recv(const struct device *dev, uint8_t *data, uint8_t size,
		     k_timeout_t timeout, int16_t *rssi, int8_t *snr)
{
	struct k_poll_signal done = K_POLL_SIGNAL_INITIALIZER(done);
	struct k_poll_event evt = K_POLL_EVENT_INITIALIZER(
		K_POLL_TYPE_SIGNAL,
		K_POLL_MODE_NOTIFY_ONLY,
		&done);
	int ret;

	/* Ensure available, decremented by sx12xx_ev_rx_done or on timeout */
	if (!modem_acquire(&dev_data)) {
		return -EBUSY;
	}

	dev_data.async_rx_cb = NULL;
	/* Store operation signal */
	dev_data.operation_done = &done;
	/* Set data output location */
	dev_data.rx_params.buf = data;
	dev_data.rx_params.size = &size;
	dev_data.rx_params.rssi = rssi;
	dev_data.rx_params.snr = snr;

	Radio.SetMaxPayloadLength(MODEM_LORA, 255);
	Radio.Rx(0);

	ret = k_poll(&evt, 1, timeout);
	if (ret < 0) {
		if (!modem_release(&dev_data)) {
			/* Releasing the modem failed, which means that
			 * the RX callback is currently running. Wait until
			 * the RX callback finishes and we get our packet.
			 */
			k_poll(&evt, 1, K_FOREVER);

			/* We did receive a packet */
			return size;
		}
		LOG_INF("Receive timeout");
		return ret;
	}

	return size;
}

int sx12xx_lora_recv_async(const struct device *dev, lora_recv_cb cb)
{
	/* Cancel ongoing reception */
	if (cb == NULL) {
		if (!modem_release(&dev_data)) {
			/* Not receiving or already being stopped */
			return -EINVAL;
		}
		return 0;
	}

	/* Ensure available */
	if (!modem_acquire(&dev_data)) {
		return -EBUSY;
	}

	/* Store parameters */
	dev_data.async_rx_cb = cb;

	/* Start reception */
	Radio.SetMaxPayloadLength(MODEM_LORA, 255);
	Radio.Rx(0);

	return 0;
}

int sx12xx_lora_config(const struct device *dev,
		       struct lora_modem_config *config)
{
	/* Ensure available, decremented after configuration */
	if (!modem_acquire(&dev_data)) {
		return -EBUSY;
	}

	Radio.SetChannel(config->frequency);

	if (config->tx) {
		/* Store TX config locally for airtime calculations */
		memcpy(&dev_data.tx_cfg, config, sizeof(dev_data.tx_cfg));
		/* Configure radio driver */
		Radio.SetTxConfig(MODEM_LORA, config->tx_power, 0,
				  config->bandwidth, config->datarate,
				  config->coding_rate, config->preamble_len,
				  false, true, 0, 0, false, 4000);
	} else {
		/* TODO: Get symbol timeout value from config parameters */
		Radio.SetRxConfig(MODEM_LORA, config->bandwidth,
				  config->datarate, config->coding_rate,
				  0, config->preamble_len, 10, false, 0,
				  false, 0, 0, false, true);
	}

	modem_release(&dev_data);
	return 0;
}

int sx12xx_lora_test_cw(const struct device *dev, uint32_t frequency,
			int8_t tx_power,
			uint16_t duration)
{
	/* Ensure available, freed in sx12xx_ev_tx_done */
	if (!modem_acquire(&dev_data)) {
		return -EBUSY;
	}

	Radio.SetTxContinuousWave(frequency, tx_power, duration);
	return 0;
}

int sx12xx_init(const struct device *dev)
{
	atomic_set(&dev_data.modem_usage, 0);

	dev_data.dev = dev;
	dev_data.events.TxDone = sx12xx_ev_tx_done;
	dev_data.events.RxDone = sx12xx_ev_rx_done;
	Radio.Init(&dev_data.events);

	/*
	 * Automatically place the radio into sleep mode upon boot.
	 * The required `lora_config` call before transmission or reception
	 * will bring the radio out of sleep mode before it is used. The radio
	 * is automatically placed back into sleep mode upon TX or RX
	 * completion.
	 */
	Radio.Sleep();

	return 0;
}