/*
 * Copyright (c) 2019 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file
 * @brief Sample echo app for CDC ACM class
 *
 * Sample app for USB CDC ACM class driver. The received data is echoed back
 * to the serial port.
 */

#include <sample_usbd.h>

#include <stdio.h>
#include <string.h>
#include <zephyr/device.h>
#include <zephyr/drivers/uart.h>
#include <zephyr/kernel.h>
#include <zephyr/sys/ring_buffer.h>

#include <zephyr/usb/usb_device.h>
#include <zephyr/usb/usbd.h>
#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(cdc_acm_echo, LOG_LEVEL_INF);

#define RING_BUF_SIZE 1024
uint8_t ring_buffer[RING_BUF_SIZE];

struct ring_buf ringbuf;

static bool rx_throttled;

#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
static struct usbd_contex *sample_usbd;

static int enable_usb_device_next(void)
{
	int err;

	sample_usbd = sample_usbd_init_device();
	if (sample_usbd == NULL) {
		LOG_ERR("Failed to initialize USB device");
		return -ENODEV;
	}

	err = usbd_enable(sample_usbd);
	if (err) {
		LOG_ERR("Failed to enable device support");
		return err;
	}

	LOG_DBG("USB device support enabled");

	return 0;
}
#endif /* IS_ENABLED(CONFIG_USB_DEVICE_STACK_NEXT) */

static void interrupt_handler(const struct device *dev, void *user_data)
{
	ARG_UNUSED(user_data);

	while (uart_irq_update(dev) && uart_irq_is_pending(dev)) {
		if (!rx_throttled && uart_irq_rx_ready(dev)) {
			int recv_len, rb_len;
			uint8_t buffer[64];
			size_t len = MIN(ring_buf_space_get(&ringbuf),
					 sizeof(buffer));

			if (len == 0) {
				/* Throttle because ring buffer is full */
				uart_irq_rx_disable(dev);
				rx_throttled = true;
				continue;
			}

			recv_len = uart_fifo_read(dev, buffer, len);
			if (recv_len < 0) {
				LOG_ERR("Failed to read UART FIFO");
				recv_len = 0;
			};

			rb_len = ring_buf_put(&ringbuf, buffer, recv_len);
			if (rb_len < recv_len) {
				LOG_ERR("Drop %u bytes", recv_len - rb_len);
			}

			LOG_DBG("tty fifo -> ringbuf %d bytes", rb_len);
			if (rb_len) {
				uart_irq_tx_enable(dev);
			}
		}

		if (uart_irq_tx_ready(dev)) {
			uint8_t buffer[64];
			int rb_len, send_len;

			rb_len = ring_buf_get(&ringbuf, buffer, sizeof(buffer));
			if (!rb_len) {
				LOG_DBG("Ring buffer empty, disable TX IRQ");
				uart_irq_tx_disable(dev);
				continue;
			}

			if (rx_throttled) {
				uart_irq_rx_enable(dev);
				rx_throttled = false;
			}

			send_len = uart_fifo_fill(dev, buffer, rb_len);
			if (send_len < rb_len) {
				LOG_ERR("Drop %d bytes", rb_len - send_len);
			}

			LOG_DBG("ringbuf -> tty fifo %d bytes", send_len);
		}
	}
}

int main(void)
{
	const struct device *dev;
	uint32_t baudrate, dtr = 0U;
	int ret;

	dev = DEVICE_DT_GET_ONE(zephyr_cdc_acm_uart);
	if (!device_is_ready(dev)) {
		LOG_ERR("CDC ACM device not ready");
		return 0;
	}

#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
		ret = enable_usb_device_next();
#else
		ret = usb_enable(NULL);
#endif

	if (ret != 0) {
		LOG_ERR("Failed to enable USB");
		return 0;
	}

	ring_buf_init(&ringbuf, sizeof(ring_buffer), ring_buffer);

	LOG_INF("Wait for DTR");

	while (true) {
		uart_line_ctrl_get(dev, UART_LINE_CTRL_DTR, &dtr);
		if (dtr) {
			break;
		} else {
			/* Give CPU resources to low priority threads. */
			k_sleep(K_MSEC(100));
		}
	}

	LOG_INF("DTR set");

	/* They are optional, we use them to test the interrupt endpoint */
	ret = uart_line_ctrl_set(dev, UART_LINE_CTRL_DCD, 1);
	if (ret) {
		LOG_WRN("Failed to set DCD, ret code %d", ret);
	}

	ret = uart_line_ctrl_set(dev, UART_LINE_CTRL_DSR, 1);
	if (ret) {
		LOG_WRN("Failed to set DSR, ret code %d", ret);
	}

	/* Wait 100ms for the host to do all settings */
	k_msleep(100);

	ret = uart_line_ctrl_get(dev, UART_LINE_CTRL_BAUD_RATE, &baudrate);
	if (ret) {
		LOG_WRN("Failed to get baudrate, ret code %d", ret);
	} else {
		LOG_INF("Baudrate detected: %d", baudrate);
	}

	uart_irq_callback_set(dev, interrupt_handler);

	/* Enable rx interrupts */
	uart_irq_rx_enable(dev);
	return 0;
}