#include <string.h>

#include <libopencm3/stm32/i2c.h>
#include <libopencm3/stm32/dma.h>

#include "i2c_dma.h"

#include "rs485.h"

#define DMA_CHANNEL_TX DMA_CHANNEL2
#define DMA_CHANNEL_RX DMA_CHANNEL3

static uint8_t m_wdata[2];
static uint8_t m_wlen;
static uint8_t m_rdata[32];
static uint8_t m_rlen;

static uint8_t m_addr;
static uint32_t m_i2c;

typedef enum {
	IDLE,
	SEND_DATA,
	RECEIVE_DATA
} i2c_dma_state_t;

static i2c_dma_state_t m_state;


static i2c_dma_callback_t m_callback;

static void setup_txdma(void)
{
	dma_channel_reset(DMA1, DMA_CHANNEL_TX);

	dma_set_priority(DMA1, DMA_CHANNEL_TX, DMA_CCR_PL_LOW);
	dma_set_memory_size(DMA1, DMA_CHANNEL_TX, DMA_CCR_MSIZE_8BIT);
	dma_set_peripheral_size(DMA1, DMA_CHANNEL_TX, DMA_CCR_PSIZE_8BIT);
	dma_enable_memory_increment_mode(DMA1, DMA_CHANNEL_TX);
	dma_set_read_from_memory(DMA1, DMA_CHANNEL_TX);
	dma_set_peripheral_address(DMA1, DMA_CHANNEL_TX, (uint32_t) &I2C_TXDR(m_i2c));

	// send m_wlen bytes from m_wdata
	dma_set_memory_address(DMA1, DMA_CHANNEL_TX, (uint32_t)m_wdata);
	dma_set_number_of_data(DMA1, DMA_CHANNEL_TX, m_wlen);

	dma_enable_channel(DMA1, DMA_CHANNEL_TX);

	i2c_enable_txdma(m_i2c);
}


static void setup_rxdma(void)
{
	dma_channel_reset(DMA1, DMA_CHANNEL_RX);

	dma_set_priority(DMA1, DMA_CHANNEL_RX, DMA_CCR_PL_LOW);
	dma_set_memory_size(DMA1, DMA_CHANNEL_RX, DMA_CCR_MSIZE_8BIT);
	dma_set_peripheral_size(DMA1, DMA_CHANNEL_RX, DMA_CCR_PSIZE_8BIT);
	dma_enable_memory_increment_mode(DMA1, DMA_CHANNEL_RX);
	dma_set_read_from_peripheral(DMA1, DMA_CHANNEL_RX);
	dma_set_peripheral_address(DMA1, DMA_CHANNEL_RX, (uint32_t) &I2C_RXDR(m_i2c));

	// receive m_rlen bytes and store them in m_rdata
	dma_set_memory_address(DMA1, DMA_CHANNEL_RX, (uint32_t)m_rdata);
	dma_set_number_of_data(DMA1, DMA_CHANNEL_RX, m_rlen);

	dma_enable_channel(DMA1, DMA_CHANNEL_RX);

	i2c_enable_rxdma(m_i2c);
}


void i2c_dma_init(i2c_dma_callback_t callback)
{
	m_callback = callback;

	m_state = IDLE;
}


void i2c_dma_loop(void)
{
	switch(m_state) {
		case IDLE:
			// nothing to do
			return;

		case SEND_DATA:
			//if(i2c_transfer_complete(m_i2c)) { // does not work for some reason :(
			if(dma_get_interrupt_flag(DMA1, DMA_CHANNEL_TX, DMA_TCIF)) {
				dma_clear_interrupt_flags(DMA1, DMA_CHANNEL_TX, DMA_TCIF);

				if(m_rlen) {
					m_state = RECEIVE_DATA;

					i2c_set_7bit_address(m_i2c, m_addr);
					i2c_set_read_transfer_dir(m_i2c);
					i2c_set_bytes_to_transfer(m_i2c, m_rlen);
					i2c_send_start(m_i2c);
					i2c_enable_autoend(m_i2c); // important to do it after start() for a proper repeated start!
					setup_rxdma();
				} else {
					// no RX requested => we are done here
					m_state = IDLE;
					m_callback(NULL, 0);
				}
			}
			break;

		case RECEIVE_DATA:
			//if(i2c_transfer_complete(m_i2c)) { // does not work for some reason :(
			if(dma_get_interrupt_flag(DMA1, DMA_CHANNEL_RX, DMA_TCIF)) {
				dma_clear_interrupt_flags(DMA1, DMA_CHANNEL_RX, DMA_TCIF);

				m_state = IDLE;
				m_callback(m_rdata, m_rlen);
			}
			break;
	}
}


void i2c_dma_start_transfer7(uint32_t i2c, uint8_t addr, const uint8_t *w, size_t wn, size_t rn)
{
	m_wlen = wn;
	m_rlen = rn;

	memcpy(m_wdata, w, wn);

	m_state = SEND_DATA;

	m_i2c = i2c;
	m_addr = addr;

	i2c_set_7bit_address(i2c, addr);
	i2c_set_write_transfer_dir(i2c);
	i2c_set_bytes_to_transfer(i2c, wn);

	if(rn) {
		i2c_disable_autoend(i2c); // prepare repeated start
	} else {
		i2c_enable_autoend(i2c); // stop condition after write transfer
	}

	i2c_send_start(i2c); // start the transfer. The rest is handled by the DMA.
	setup_txdma();
}