/*
 * (C) Copyright 2014 Leo C. <erbl259-lmu@yahoo.de>
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/usart.h>
#include <libopencm3/cm3/nvic.h>
#include "serial.h"


#define USART_CONSOLE USART1

int _write(int fd, char *ptr, int len)  __attribute__((used));


struct ring {
	uint8_t *data;
	int size;
	volatile int begin;
	volatile int end;
};


#define BUFFER_SIZE 256

struct ring rx_ring;
struct ring tx_ring;
uint8_t rx_ring_buffer[BUFFER_SIZE];
uint8_t tx_ring_buffer[BUFFER_SIZE];


static void ring_init(struct ring *ring, uint8_t *buf, int size)
{
	ring->data = buf;
	ring->size = size;
	ring->begin = 0;
	ring->end = 0;
}

static int ring_write_ch(struct ring *ring, uint8_t ch)
{
	int ep = (ring->end + 1) % ring->size;

	if ((ep) != ring->begin) {
		ring->data[ring->end] = ch;
		ring->end = ep;
		return 1;
	}

	return -1;
}

static int ring_write(struct ring *ring, uint8_t *data, int size)
{
	int i;

	for (i = 0; i < size; i++) {
		if (ring_write_ch(ring, data[i]) < 0)
			return -i;
	}

	return i;
}

static int ring_read_ch(struct ring *ring)
{
	int ret = -1;

	if (ring->begin != ring->end) {
		ret = ring->data[ring->begin];
		ring->begin = (ring->begin +1) % ring->size;
	}

	return ret;
}

void usart_setup(void)
{
	/* Initialize output ring buffer. */
	ring_init(&rx_ring, rx_ring_buffer, BUFFER_SIZE);
	ring_init(&tx_ring, tx_ring_buffer, BUFFER_SIZE);

	/* Enable the USART1 interrupt. */
	nvic_enable_irq(NVIC_USART1_IRQ);

	/* Setup GPIO pin GPIO_USART1_TX/LED_GREEN_PIN on GPIO port A for transmit. */
	/* TODO: USART1 --> USART_CONSOLE */

	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
		      GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX);

	/* Setup GPIO pin GPIO_USART1_RE_RX on GPIO port B for receive. */
	gpio_set_mode(GPIOA, GPIO_MODE_INPUT,
		      GPIO_CNF_INPUT_FLOAT, GPIO_USART1_RX);

	/* Setup UART parameters. */
//	usart_set_baudrate(USART_CONSOLE, 38400);
	usart_set_baudrate(USART_CONSOLE, 115200);
	usart_set_databits(USART_CONSOLE, 8);
	usart_set_stopbits(USART_CONSOLE, USART_STOPBITS_1);
	usart_set_parity(USART_CONSOLE, USART_PARITY_NONE);
	usart_set_flow_control(USART_CONSOLE, USART_FLOWCONTROL_NONE);
	usart_set_mode(USART_CONSOLE, USART_MODE_TX_RX);

	/* Enable USART1 Receive interrupt. */
	USART_CR1(USART1) |= USART_CR1_RXNEIE;

	/* Finally enable the USART. */
	usart_enable(USART_CONSOLE);
}

void usart1_isr(void)
{
	/* Check if we were called because of RXNE. */
	if (((USART_CR1(USART1) & USART_CR1_RXNEIE) != 0) &&
	    ((USART_SR(USART1) & USART_SR_RXNE) != 0)) {

		/* Retrieve the data from the peripheral. */
		ring_write_ch(&rx_ring, usart_recv(USART1));

	}

	/* Check if we were called because of TXE. */
	if (((USART_CR1(USART1) & USART_CR1_TXEIE) != 0) &&
	    ((USART_SR(USART1) & USART_SR_TXE) != 0)) {

		int data;

		data = ring_read_ch(&tx_ring);

		if (data == -1) {
			/* Disable the TXE interrupt, it's no longer needed. */
			USART_CR1(USART1) &= ~USART_CR1_TXEIE;
		} else {
			/* Put data into the transmit register. */
			usart_send(USART1, data);
		}
	}
}

/*--------------------------------------------------------------------------*/

void serial_setup(void)
{
	usart_setup();
}

/*--------------------------------------------------------------------------*/

/**
 * Use USART_CONSOLE as a console.
 * This is a syscall for newlib
 * @param fd
 * @param ptr
 * @param len
 * @return
 */
int _write(int fd, char *ptr, int len)
{
	int i;

	if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
		for (i = 0; i < len; i++) {
			if (ptr[i] == '\n') {
				serial_putc('\r');
			}
			serial_putc(ptr[i]);
		}
		return i;
	}
	errno = EIO;
	return -1;
}

int serial_getc(void)
{
	return ring_read_ch(&rx_ring);
}

void serial_putc(uint8_t data)
{
	while (ring_write_ch(&tx_ring, data) < 0)
		;

	/* Enable the TXE interrupt. */
	USART_CR1(USART1) |= USART_CR1_TXEIE;
}