#define _GNU_SOURCE
#include <stdint.h>
#include <stdlib.h>

#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/spi.h>
#include <libopencm3/stm32/usart.h>

#include <spi.h>

static int stm32f0_spi_set_cs_level(struct spi_dev *dev, int level);
static int stm32f0_spi_tx_rx(struct spi_dev *dev, void *rx_buf,
	const void *tx_buf, size_t len);

static struct spi_ops stm32f0_spi_ops = {
	.set_cs_level = stm32f0_spi_set_cs_level,
	.tx_rx = stm32f0_spi_tx_rx,
};

static void stm32f0_spi_init(void)
{
	/* Set up clocks for SPI 1 */
	rcc_clock_setup_in_hsi_out_48mhz();
	rcc_periph_clock_enable(RCC_GPIOA);
	rcc_periph_clock_enable(RCC_GPIOB);
	rcc_periph_clock_enable(RCC_SPI1);

	/* Set up GPIOs for SPI 1 */
	gpio_mode_setup(GPIOA, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO4);
	gpio_set(GPIOA, GPIO4);
	gpio_mode_setup(GPIOB, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO3 | GPIO4 | GPIO5);
	gpio_set_af(GPIOB, GPIO_AF0, GPIO3 | GPIO4 | GPIO5);

	spi_set_master_mode(SPI1);
	spi_set_baudrate_prescaler(SPI1, SPI_CR1_BR_FPCLK_DIV_64);
	spi_set_clock_polarity_0(SPI1);
	spi_set_clock_phase_0(SPI1);
	spi_set_full_duplex_mode(SPI1);
	spi_set_unidirectional_mode(SPI1); /* bidirectional but in 3-wire */
	spi_set_data_size(SPI1, SPI_CR2_DS_8BIT);
	spi_enable_software_slave_management(SPI1);
	spi_send_msb_first(SPI1);
	spi_set_nss_high(SPI1);
	spi_fifo_reception_threshold_8bit(SPI1);
	SPI_I2SCFGR(SPI1) &= ~SPI_I2SCFGR_I2SMOD;
	spi_enable(SPI1);
}

struct spi_dev *spi_probe(void)
{
	struct spi_dev *dev;

	if (!(dev = malloc(sizeof *dev)))
		return NULL;

	dev->ops = &stm32f0_spi_ops;
	dev->dev_id = SPI1;

	stm32f0_spi_init();

	return dev;
}

static int stm32f0_spi_set_cs_level(struct spi_dev *dev, int level)
{
	(void)dev;

	if (level) {
		gpio_set(GPIOA, GPIO4);
	} else {
		gpio_clear(GPIOA, GPIO4);
	}

	return 0;
}

static int stm32f0_spi_tx_rx(struct spi_dev *dev, void *rx_buf,
	const void *tx_buf, size_t len)
{
	char *rx = rx_buf;
	const char *tx = tx_buf;
	size_t i;

	for (i = 0; i < len; ++i) {
		spi_send8(dev->dev_id, tx ? *tx++ : 0);

		if (rx) {
			*rx++ = spi_read8(dev->dev_id);
		}
	}

	return 0;
}