#include <stdio.h>
#include <sys/cdefs.h>
#include <libopencm3/cm3/assert.h>
#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/usart.h>

#include <libcommon/iob.h>

#include <librfn/ringbuf.h>

/* STM32F0 has slightly different status register #defines */
#ifdef USART_ISR_RXNE
#define USART_SR_RXNE USART_ISR_RXNE
#define USART_SR_TXE USART_ISR_TXE
#define USART_SR(x) USART_ISR(x)
#endif

/* picolibc iob implementation for non-blocking I/O on USART via ring-buffer */

static uint32_t stdio_usart;
static uint8_t outbuf[1024];
static ringbuf_t outring = RINGBUF_VAR_INIT(outbuf, sizeof(outbuf));

static uint8_t inbuf[256];
static ringbuf_t inring = RINGBUF_VAR_INIT(inbuf, sizeof(inbuf));

void iob_init(uint32_t usart)
{
	cm3_assert(usart == USART2);
	stdio_usart = usart;

	nvic_enable_irq(NVIC_USART2_IRQ);
	/* Enable RX non-empty interrupt */
	USART_CR1(stdio_usart) |= USART_CR1_RXNEIE;
}

/* FIXME: this obviously doesn't work with iob_init() getting passed a dynamic UART */
void usart2_isr(void)
{
	if ((USART_CR1(stdio_usart) & USART_CR1_RXNEIE) &&
	    (USART_SR(stdio_usart) & USART_SR_RXNE)) {
		uint16_t c = usart_recv(stdio_usart);
		ringbuf_put(&inring, c);
	}

	if ((USART_CR1(stdio_usart) & USART_CR1_TXEIE) &&
	    (USART_SR(stdio_usart) & USART_SR_TXE)) {
		int data = ringbuf_get(&outring);
		if (data == -1) {
			USART_CR1(stdio_usart) &= ~USART_CR1_TXEIE;
		} else {
			usart_send(stdio_usart, data);
		}
	}
}

/* buffered output to stdout */
static int my_stdout_putc(char c, FILE *file)
{
	(void) file;
	cm3_assert(stdio_usart);
	ringbuf_put(&outring, c);
	USART_CR1(stdio_usart) |= USART_CR1_TXEIE;
	return c;
}

/* unbuffered, blocking output to stderr (e.g. for assert, fault handlers, ...) */
static int my_stderr_putc(char c, FILE *file)
{
	(void) file;
	cm3_assert(stdio_usart);
	usart_send_blocking(stdio_usart, c);
	return c;
}

static int my_stdin_getc(FILE *file)
{
	(void) file;
	int data = ringbuf_get(&inring);

	if (data == -1)
		return EOF;
	else
		return data;
}

static int my_stdout_flush(FILE *file)
{
	(void) file;
	do { } while (!ringbuf_empty(&outring));
	return 0;
}

static FILE __stdin = FDEV_SETUP_STREAM(NULL, my_stdin_getc, NULL, _FDEV_SETUP_READ);
static FILE __stdout = FDEV_SETUP_STREAM(my_stdout_putc, NULL, my_stdout_flush, _FDEV_SETUP_WRITE);
static FILE __stderr = FDEV_SETUP_STREAM(my_stderr_putc, NULL, NULL, _FDEV_SETUP_WRITE);

#ifndef PICOLIBC_STDIO_GLOBALS
FILE *const __iob[3] = { &__stdin, &__stdout, &__stderr };
#else
FILE *const stdin = &__stdin;
FILE *const stdout = &__stdout;
FILE *const stderr = &__stderr;
#endif

#include <libcommon/microvty.h>

bool microvty_cb_uart_rx_not_empty(void)
{
	return !ringbuf_empty(&inring);
}