/* Teensyduino Core Library
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2013 PJRC.COM, LLC.
 * Modified by Jacob Alexander 2013-2014
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * 1. The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * 2. If the Software is incorporated into a build system that allows
 * selection among a list of target devices, then similar target
 * devices manufactured by PJRC.COM must be included in the list of
 * target devices and selectable in the same manner.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

// ----- Includes -----

// Compiler Includes
#include <string.h> // For memcpy

// Project Includes
#include <Lib/OutputLib.h>

// Local Includes
#include "usb_dev.h"
#include "usb_serial.h"



// ----- Defines -----

#define TRANSMIT_FLUSH_TIMEOUT  5   /* in milliseconds */

// Maximum number of transmit packets to queue so we don't starve other endpoints for memory
#define TX_PACKET_LIMIT 8

// When the PC isn't listening, how long do we wait before discarding data?  If this is
// too short, we risk losing data during the stalls that are common with ordinary desktop
// software.  If it's too long, we stall the user's program when no software is running.
#define TX_TIMEOUT_MSEC 70

#if F_CPU == 96000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 596)
#elif F_CPU == 48000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 428)
#elif F_CPU == 24000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 262)
#endif



// ----- Variables -----

// serial port settings (baud rate, control signals, etc) set
// by the PC.  These are ignored, but kept in RAM.
volatile uint8_t usb_cdc_line_coding[7] = { 0x00, 0xE1, 0x00, 0x00, 0x00, 0x00, 0x08 };
volatile uint8_t usb_cdc_line_rtsdtr = 0;
volatile uint8_t usb_cdc_transmit_flush_timer = 0;

static usb_packet_t *rx_packet = NULL;
static usb_packet_t *tx_packet = NULL;
static volatile uint8_t tx_noautoflush = 0;

// When we've suffered the transmit timeout, don't wait again until the computer
// begins accepting data.  If no software is running to receive, we'll just discard
// data as rapidly as Serial.print() can generate it, until there's something to
// actually receive it.
static uint8_t transmit_previous_timeout = 0;



// ----- Functions -----

// get the next character, or -1 if nothing received
int usb_serial_getchar()
{
	unsigned int i;
	int c;

	if ( !rx_packet )
	{
		if ( !usb_configuration )
			return -1;
		rx_packet = usb_rx( CDC_RX_ENDPOINT );
		if ( !rx_packet )
			return -1;
	}
	i = rx_packet->index;
	c = rx_packet->buf[i++];
	if ( i >= rx_packet->len )
	{
		usb_free( rx_packet );
		rx_packet = NULL;
	}
	else
	{
		rx_packet->index = i;
	}
	return c;
}

// peek at the next character, or -1 if nothing received
int usb_serial_peekchar()
{
	if ( !rx_packet )
	{
		if ( !usb_configuration )
			return -1;
		rx_packet = usb_rx( CDC_RX_ENDPOINT );
		if ( !rx_packet )
			return -1;
	}
	if ( !rx_packet )
		return -1;
	return rx_packet->buf[ rx_packet->index ];
}

// number of bytes available in the receive buffer
int usb_serial_available()
{
	int count = usb_rx_byte_count( CDC_RX_ENDPOINT );
	if ( rx_packet )
		count += rx_packet->len - rx_packet->index;
	return count;
}

// read a block of bytes to a buffer
int usb_serial_read( void *buffer, uint32_t size )
{
	uint8_t *p = (uint8_t *)buffer;
	uint32_t qty, count=0;

	while ( size )
	{
		if ( !usb_configuration )
			break;
		if ( !rx_packet )
		{
			rx:
				rx_packet = usb_rx(CDC_RX_ENDPOINT);
				if ( !rx_packet )
					break;
				if ( rx_packet->len == 0 )
				{
					usb_free(rx_packet);
					goto rx;
				}
		}
		qty = rx_packet->len - rx_packet->index;
		if ( qty > size )
			qty = size;
		memcpy( p, rx_packet->buf + rx_packet->index, qty );
		p += qty;
		count += qty;
		size -= qty;
		rx_packet->index += qty;
		if ( rx_packet->index >= rx_packet->len )
		{
			usb_free( rx_packet );
			rx_packet = NULL;
		}
	}
	return count;
}

// discard any buffered input
void usb_serial_flush_input()
{
	usb_packet_t *rx;

	if ( !usb_configuration )
		return;
	if ( rx_packet )
	{
		usb_free( rx_packet );
		rx_packet = NULL;
	}
	while (1)
	{
		rx = usb_rx( CDC_RX_ENDPOINT );
		if ( !rx )
			break;
		usb_free( rx );
	}
}

// transmit a character.  0 returned on success, -1 on error
int usb_serial_putchar( uint8_t c )
{
	return usb_serial_write( &c, 1 );
}

int usb_serial_write( const void *buffer, uint32_t size )
{
	uint32_t len;
	uint32_t wait_count;
	const uint8_t *src = (const uint8_t *)buffer;
	uint8_t *dest;

	tx_noautoflush = 1;
	while ( size > 0 )
	{
		if ( !tx_packet )
		{
			wait_count = 0;
			while ( 1 )
			{
				if ( !usb_configuration )
				{
					tx_noautoflush = 0;
					return -1;
				}
				if ( usb_tx_packet_count( CDC_TX_ENDPOINT ) < TX_PACKET_LIMIT )
				{
					tx_noautoflush = 1;
					tx_packet = usb_malloc();
					if ( tx_packet )
						break;
					tx_noautoflush = 0;
				}
				if ( ++wait_count > TX_TIMEOUT || transmit_previous_timeout )
				{
					transmit_previous_timeout = 1;
					return -1;
				}
				yield();
			}
		}
		transmit_previous_timeout = 0;
		len = CDC_TX_SIZE - tx_packet->index;
		if ( len > size )
			len = size;
		dest = tx_packet->buf + tx_packet->index;
		tx_packet->index += len;
		size -= len;
		while ( len-- > 0 )
			*dest++ = *src++;
		if ( tx_packet->index >= CDC_TX_SIZE )
		{
			tx_packet->len = CDC_TX_SIZE;
			usb_tx( CDC_TX_ENDPOINT, tx_packet );
			tx_packet = NULL;
		}
		usb_cdc_transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
	}
	tx_noautoflush = 0;
	return 0;
}

void usb_serial_flush_output()
{
	if ( !usb_configuration )
		return;
	tx_noautoflush = 1;
	if ( tx_packet )
	{
		usb_cdc_transmit_flush_timer = 0;
		tx_packet->len = tx_packet->index;
		usb_tx( CDC_TX_ENDPOINT, tx_packet );
		tx_packet = NULL;
	}
	else
	{
		usb_packet_t *tx = usb_malloc();
		if ( tx )
		{
			usb_cdc_transmit_flush_timer = 0;
			usb_tx( CDC_TX_ENDPOINT, tx );
		}
		else
		{
			usb_cdc_transmit_flush_timer = 1;
		}
	}
	tx_noautoflush = 0;
}

void usb_serial_flush_callback()
{
	if ( tx_noautoflush )
		return;
	if ( tx_packet )
	{
		tx_packet->len = tx_packet->index;
		usb_tx( CDC_TX_ENDPOINT, tx_packet );
		tx_packet = NULL;
	} else {
		usb_packet_t *tx = usb_malloc();
		if ( tx )
		{
			usb_tx( CDC_TX_ENDPOINT, tx );
		}
		else
		{
			usb_cdc_transmit_flush_timer = 1;
		}
	}
}