/** @file usart.c
 * Module handling Universal Synchronous/Asynchronous Receiver/Transmitter
 *
 * The module provides functions to configure the usarts and read/write from/to
 * it
 */

//--includes--------------------------------------------------------------------

#include "usart.h"
#include "usart_regs.h"
#include "reg.h"

#include "rcc.h"
#include "dma.h"

#include "stddef.h"


//--local definitions-----------------------------------------------------------

struct CircularBuffer {
	volatile uint8_t* buffer;
	uint16_t size;
	uint16_t begin;
	bool dmaLooped;
};

static void configure_usart(volatile struct USART* regs,
		enum UsartConfig config);
static void configure_baudrate(volatile struct USART* regs, uint32_t clock,
		uint32_t baudrate);
static uint32_t periph_regs(enum UsartPeriph periph,
		volatile struct USART** regs);
static uint32_t read_from_buffer(struct CircularBuffer* buffer,
		enum DmaChannel channel, uint8_t* byte);

static void usart1_rx_callback(enum DmaIRQSource src);


//--local variables-------------------------------------------------------------

static volatile struct USART* const usart1 = (struct USART*)USART1_BASE_ADDRESS;
static volatile struct USART* const usart2 = (struct USART*)USART2_BASE_ADDRESS;
static volatile struct USART* const usart3 = (struct USART*)USART3_BASE_ADDRESS;

static struct CircularBuffer usart1_rx_buffer;


//--public functions------------------------------------------------------------

void usart_configure(enum UsartPeriph periph, enum UsartConfig config,
		uint32_t baudrate)
{
	struct RccClocks clocks;
	rcc_get_clocks(&clocks);

	switch (periph) {
		case USART_PERIPH_1:
			rcc_enable(RCC_AHB_NONE, RCC_APB1_NONE, RCC_APB2_USART);
			configure_baudrate(usart1, clocks.apb2_freq, baudrate);
			configure_usart(usart1, config);
			break;
		case USART_PERIPH_2:
			rcc_enable(RCC_AHB_NONE, RCC_APB1_USART2, RCC_APB2_NONE);
			configure_baudrate(usart2, clocks.apb1_freq, baudrate);
			configure_usart(usart2, config);
			break;
		case USART_PERIPH_3:
			rcc_enable(RCC_AHB_NONE, RCC_APB1_USART3, RCC_APB2_NONE);
			configure_baudrate(usart3, clocks.apb1_freq, baudrate);
			configure_usart(usart3, config);
			break;
		default:
			break;
	}
}

uint32_t usart_write_byte(enum UsartPeriph periph, uint8_t byte)
{
	volatile struct USART* regs;
	if (periph_regs(periph, &regs)) {
		return 1;
	}

	if (regs->SR.TXE) {
		reg_write(regs->DR, USART_DR_DR, byte);
		return 0;
	} else {
		return 1;
	}
}

uint32_t usart_read_byte(enum UsartPeriph periph, uint8_t* byte)
{
	volatile struct USART* regs;
	struct CircularBuffer* buffer;
	enum DmaChannel dma_channel;

	switch (periph) {
		case USART_PERIPH_1:
			regs = usart1;
			buffer = &usart1_rx_buffer;
			dma_channel = DMA_CHANNEL_5;
			break;
		case USART_PERIPH_2:
		case USART_PERIPH_3:
		default:
			return 1;
			break;
	}

	if (buffer->buffer) {
		return read_from_buffer(buffer, dma_channel, byte);
	} else {
		if (regs->SR.RXNE) {
			*byte = regs->DR.DR;
			return 0;
		} else {
			return 1;
		}
	}
}

void usart_set_rx_buffer(enum UsartPeriph periph, uint8_t* buffer,
		uint16_t size)
{
	switch (periph) {
		case USART_PERIPH_1:
			dma_configure(DMA_PERIPH_1, DMA_CHANNEL_5,
					DMA_CONFIG_IRQ_COMPLETE | DMA_CONFIG_FROM_PERIPH
					| DMA_CONFIG_CIRCULAR | DMA_CONFIG_INC_MEM
					| DMA_CONFIG_PSIZE_8BITS | DMA_CONFIG_MSIZE_8BITS
					| DMA_CONFIG_PRIO_LOW, (void*)&usart1->DR, buffer,
					size, usart1_rx_callback);
			usart1_rx_buffer.buffer = buffer;
			usart1_rx_buffer.size = size;
			usart1_rx_buffer.begin = 0;
			usart1_rx_buffer.dmaLooped = false;
			reg_set(usart1->CR3, USART_CR3_DMAR);
			break;
		case USART_PERIPH_2:
			break;
		case USART_PERIPH_3:
			break;
	}
}

//--local functions-------------------------------------------------------------

static void configure_usart(volatile struct USART* regs, enum UsartConfig config)
{
	usart1_rx_buffer.buffer = NULL;
	//configure parity
	switch (config)
	{
		case USART_CONFIG_7E1:
		case USART_CONFIG_8E1:
		case USART_CONFIG_7E2:
		case USART_CONFIG_8E2:
			reg_set(regs->CR1, USART_CR1_PCE);
			reg_reset(regs->CR1, USART_CR1_PS);
			break;
		case USART_CONFIG_7O1:
		case USART_CONFIG_7O2:
		case USART_CONFIG_8O1:
		case USART_CONFIG_8O2:
			reg_set(regs->CR1, USART_CR1_PCE);
			reg_set(regs->CR1, USART_CR1_PS);
			break;
		case USART_CONFIG_8N1:
		case USART_CONFIG_8N2:
			reg_reset(regs->CR1, USART_CR1_PCE);
			break;
		default:
			break;
	}

	//configure bit number
	switch (config)
	{
		case USART_CONFIG_7E1:
		case USART_CONFIG_7E2:
		case USART_CONFIG_7O1:
		case USART_CONFIG_7O2:
		case USART_CONFIG_8N1:
		case USART_CONFIG_8N2:
			reg_reset(regs->CR1, USART_CR1_M);
			break;
		case USART_CONFIG_8E2:
		case USART_CONFIG_8E1:
		case USART_CONFIG_8O1:
		case USART_CONFIG_8O2:
			reg_set(regs->CR1, USART_CR1_M);
			break;
		default:
			break;
	}

	//configure stop bits
	switch (config)
	{
		case USART_CONFIG_7E1:
		case USART_CONFIG_7O1:
		case USART_CONFIG_8N1:
		case USART_CONFIG_8E1:
		case USART_CONFIG_8O1:
			reg_reset(regs->CR2, USART_CR2_STOP);
			break;
		case USART_CONFIG_7E2:
		case USART_CONFIG_7O2:
		case USART_CONFIG_8N2:
		case USART_CONFIG_8E2:
		case USART_CONFIG_8O2:
			reg_reset(regs->CR2, USART_CR2_STOP);
			reg_write(regs->CR2, USART_CR2_STOP, 2);
			break;
		default:
			break;
	}

	//enable Rx/Tx
	reg_set(regs->CR1, USART_CR1_TE);
	reg_set(regs->CR1, USART_CR1_RE);
	reg_set(regs->CR1, USART_CR1_UE);
}

static void configure_baudrate(volatile struct USART* regs, uint32_t clock,
		uint32_t baudrate)
{
	uint32_t mantissa = clock / (baudrate * 16);
	uint32_t factor = clock / baudrate;
	volatile uint32_t divider = factor - (mantissa * 16);

	reg_reset(regs->BRR, USART_BRR_DIV_Mantissa);
	reg_write(regs->BRR, USART_BRR_DIV_Mantissa, mantissa & 0xFFF);
	reg_reset(regs->BRR, USART_BRR_DIV_Fraction);
	reg_write(regs->BRR, USART_BRR_DIV_Fraction, divider & 0xF);
}

static uint32_t periph_regs(enum UsartPeriph periph, volatile struct USART** regs)
{
	switch (periph) {
		case USART_PERIPH_1:
			*regs = usart1;
			break;
		case USART_PERIPH_2:
			*regs = usart2;
			break;
		case USART_PERIPH_3:
			*regs = usart3;
			break;
		default:
			return 1;
			break;
	}

	return 0;
}

static uint32_t read_from_buffer(struct CircularBuffer* buffer,
		enum DmaChannel channel, uint8_t* byte)
{
	uint16_t end = buffer->size - dma_get_remaining(DMA_PERIPH_1, channel);

	if ((end > buffer->begin) && buffer->dmaLooped) {
		//TODO overflow
		buffer->begin = end;
	} else if ((buffer->begin == end) && !buffer->dmaLooped) {
		//TODO no data
		return 1;
	}

	*byte = buffer->buffer[buffer->begin];
	++buffer->begin;
	if (buffer->begin >= buffer->size) {
		buffer->begin = 0;
		buffer->dmaLooped = false;
	}

	return 0;
}

//--callbacks-------------------------------------------------------------------

static void usart1_rx_callback(enum DmaIRQSource src)
{
	(void)src; //only transfer complete expected
	usart1_rx_buffer.dmaLooped = true;
}