/**
 ******************************************************************************
 * @addtogroup OpenPilotSystem OpenPilot System
 * @{
 * @addtogroup OpenPilotLibraries OpenPilot System Libraries
 * @{
 *
 * @file       uavtalk.c
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 * @brief      UAVTalk library, implements to telemetry protocol. See the wiki for more details.
 * 	       This library should not be called directly by the application, it is only used by the
 * 	       Telemetry module.
 * @see        The GNU Public License (GPL) Version 3
 *
 *****************************************************************************/
/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "openpilot.h"

// Private constants
#define SYNC_VAL			0x3C
#define TYPE_MASK			0xFC
#define TYPE_VER			0x20
#define TYPE_OBJ			(TYPE_VER | 0x00)
#define TYPE_OBJ_REQ		(TYPE_VER | 0x01)
#define TYPE_OBJ_ACK		(TYPE_VER | 0x02)
#define TYPE_ACK			(TYPE_VER | 0x03)

#define MIN_HEADER_LENGTH	8	// sync(1), type (1), size (2), object ID (4)
#define MAX_HEADER_LENGTH	10	// sync(1), type (1), size (2), object ID (4), instance ID (2, not used in single objects)

#define CHECKSUM_LENGTH		1

#define MAX_PAYLOAD_LENGTH	256

#define MAX_PACKET_LENGTH	(MAX_HEADER_LENGTH + MAX_PAYLOAD_LENGTH + CHECKSUM_LENGTH)

// CRC lookup table
static const uint8_t crc_table[256] = {
    0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15, 0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d,
    0x70, 0x77, 0x7e, 0x79, 0x6c, 0x6b, 0x62, 0x65, 0x48, 0x4f, 0x46, 0x41, 0x54, 0x53, 0x5a, 0x5d,
    0xe0, 0xe7, 0xee, 0xe9, 0xfc, 0xfb, 0xf2, 0xf5, 0xd8, 0xdf, 0xd6, 0xd1, 0xc4, 0xc3, 0xca, 0xcd,
    0x90, 0x97, 0x9e, 0x99, 0x8c, 0x8b, 0x82, 0x85, 0xa8, 0xaf, 0xa6, 0xa1, 0xb4, 0xb3, 0xba, 0xbd,
    0xc7, 0xc0, 0xc9, 0xce, 0xdb, 0xdc, 0xd5, 0xd2, 0xff, 0xf8, 0xf1, 0xf6, 0xe3, 0xe4, 0xed, 0xea,
    0xb7, 0xb0, 0xb9, 0xbe, 0xab, 0xac, 0xa5, 0xa2, 0x8f, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9d, 0x9a,
    0x27, 0x20, 0x29, 0x2e, 0x3b, 0x3c, 0x35, 0x32, 0x1f, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0d, 0x0a,
    0x57, 0x50, 0x59, 0x5e, 0x4b, 0x4c, 0x45, 0x42, 0x6f, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7d, 0x7a,
    0x89, 0x8e, 0x87, 0x80, 0x95, 0x92, 0x9b, 0x9c, 0xb1, 0xb6, 0xbf, 0xb8, 0xad, 0xaa, 0xa3, 0xa4,
    0xf9, 0xfe, 0xf7, 0xf0, 0xe5, 0xe2, 0xeb, 0xec, 0xc1, 0xc6, 0xcf, 0xc8, 0xdd, 0xda, 0xd3, 0xd4,
    0x69, 0x6e, 0x67, 0x60, 0x75, 0x72, 0x7b, 0x7c, 0x51, 0x56, 0x5f, 0x58, 0x4d, 0x4a, 0x43, 0x44,
    0x19, 0x1e, 0x17, 0x10, 0x05, 0x02, 0x0b, 0x0c, 0x21, 0x26, 0x2f, 0x28, 0x3d, 0x3a, 0x33, 0x34,
    0x4e, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5c, 0x5b, 0x76, 0x71, 0x78, 0x7f, 0x6a, 0x6d, 0x64, 0x63,
    0x3e, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2c, 0x2b, 0x06, 0x01, 0x08, 0x0f, 0x1a, 0x1d, 0x14, 0x13,
    0xae, 0xa9, 0xa0, 0xa7, 0xb2, 0xb5, 0xbc, 0xbb, 0x96, 0x91, 0x98, 0x9f, 0x8a, 0x8d, 0x84, 0x83,
    0xde, 0xd9, 0xd0, 0xd7, 0xc2, 0xc5, 0xcc, 0xcb, 0xe6, 0xe1, 0xe8, 0xef, 0xfa, 0xfd, 0xf4, 0xf3
};

// Private types
typedef enum {STATE_SYNC, STATE_TYPE, STATE_SIZE, STATE_OBJID, STATE_INSTID, STATE_DATA, STATE_CS} RxState;

// Private variables
static UAVTalkOutputStream outStream;
static xSemaphoreHandle lock;
static xSemaphoreHandle transLock;
static xSemaphoreHandle respSema;
static UAVObjHandle respObj;
static uint16_t respInstId;
static uint8_t rxBuffer[MAX_PACKET_LENGTH];
static uint8_t txBuffer[MAX_PACKET_LENGTH];
static UAVTalkStats stats;

// Private functions
static uint8_t updateCRCbyte(uint8_t crc, const uint8_t data);
static uint8_t updateCRC(uint8_t crc, const uint8_t* data, int32_t length);
static int32_t objectTransaction(UAVObjHandle objectId, uint16_t instId, uint8_t type, int32_t timeout);
static int32_t sendObject(UAVObjHandle obj, uint16_t instId, uint8_t type);
static int32_t sendSingleObject(UAVObjHandle obj, uint16_t instId, uint8_t type);
static int32_t receiveObject(uint8_t type, UAVObjHandle obj, uint16_t instId, uint8_t* data, int32_t length);
static void updateAck(UAVObjHandle obj, uint16_t instId);

/**
 * Initialize the UAVTalk library
 * \param[in] outputStream Function pointer that is called to send a data buffer
 * \return 0 Success
 * \return -1 Failure
 */
int32_t UAVTalkInitialize(UAVTalkOutputStream outputStream)
{
    outStream = outputStream;
    lock = xSemaphoreCreateRecursiveMutex();
    transLock = xSemaphoreCreateRecursiveMutex();
    vSemaphoreCreateBinary(respSema);
    xSemaphoreTake(respSema, 0); // reset to zero
    UAVTalkResetStats();
    return 0;
}

/**
 * Get communication statistics counters
 * @param[out] statsOut Statistics counters
 */
void UAVTalkGetStats(UAVTalkStats* statsOut)
{
	// Lock
    xSemaphoreTakeRecursive(lock, portMAX_DELAY);

    // Copy stats
    memcpy(statsOut, &stats, sizeof(UAVTalkStats));

    // Release lock
    xSemaphoreGiveRecursive(lock);
}

/**
 * Reset the statistics counters.
 */
void UAVTalkResetStats()
{
	// Lock
    xSemaphoreTakeRecursive(lock, portMAX_DELAY);

    // Clear stats
    memset(&stats, 0, sizeof(UAVTalkStats));

    // Release lock
    xSemaphoreGiveRecursive(lock);
}

/**
 * Request an update for the specified object, on success the object data would have been
 * updated by the GCS.
 * \param[in] obj Object to update
 * \param[in] instId The instance ID or UAVOBJ_ALL_INSTANCES for all instances.
 * \param[in] timeout Time to wait for the response, when zero it will return immediately
 * \return 0 Success
 * \return -1 Failure
 */
int32_t UAVTalkSendObjectRequest(UAVObjHandle obj, uint16_t instId, int32_t timeout)
{
    return objectTransaction(obj, instId, TYPE_OBJ_REQ, timeout);
}

/**
 * Send the specified object through the telemetry link.
 * \param[in] obj Object to send
 * \param[in] instId The instance ID or UAVOBJ_ALL_INSTANCES for all instances.
 * \param[in] acked Selects if an ack is required (1:ack required, 0: ack not required)
 * \param[in] timeoutMs Time to wait for the ack, when zero it will return immediately
 * \return 0 Success
 * \return -1 Failure
 */
int32_t UAVTalkSendObject(UAVObjHandle obj, uint16_t instId, uint8_t acked, int32_t timeoutMs)
{
	// Send object
    if (acked == 1)
    {
        return objectTransaction(obj, instId, TYPE_OBJ_ACK, timeoutMs);
    }
    else
    {
        return objectTransaction(obj, instId, TYPE_OBJ, timeoutMs);
    }
}

/**
 * Execute the requested transaction on an object.
 * \param[in] obj Object
 * \param[in] instId The instance ID of UAVOBJ_ALL_INSTANCES for all instances.
 * \param[in] type Transaction type
 * 			  TYPE_OBJ: send object,
 * 			  TYPE_OBJ_REQ: request object update
 * 			  TYPE_OBJ_ACK: send object with an ack
 * \return 0 Success
 * \return -1 Failure
 */
static int32_t objectTransaction(UAVObjHandle obj, uint16_t instId, uint8_t type, int32_t timeoutMs)
{
	int32_t respReceived;

    // Send object depending on if a response is needed
    if (type == TYPE_OBJ_ACK || type == TYPE_OBJ_REQ)
    {
    	// Get transaction lock (will block if a transaction is pending)
    	xSemaphoreTakeRecursive(transLock, portMAX_DELAY);
    	// Send object
    	xSemaphoreTakeRecursive(lock, portMAX_DELAY);
        respObj = obj;
        respInstId = instId;
        sendObject(obj, instId, type);
        xSemaphoreGiveRecursive(lock);
        // Wait for response (or timeout)
    	respReceived = xSemaphoreTake(respSema, timeoutMs/portTICK_RATE_MS);
    	// Check if a response was received
    	if (respReceived == pdFALSE)
    	{
    		// Cancel transaction
    		xSemaphoreTakeRecursive(lock, portMAX_DELAY);
    		xSemaphoreTake(respSema, 0); // non blocking call to make sure the value is reset to zero (binary sema)
    		respObj = 0;
    		xSemaphoreGiveRecursive(lock);
    		xSemaphoreGiveRecursive(transLock);
    		return -1;
    	}
    	else
    	{
    		xSemaphoreGiveRecursive(transLock);
    		return 0;
    	}
    }
    else if (type == TYPE_OBJ)
    {
    	xSemaphoreTakeRecursive(lock, portMAX_DELAY);
        sendObject(obj, instId, TYPE_OBJ);
        xSemaphoreGiveRecursive(lock);
        return 0;
    }
    else
    {
        return -1;
    }
}

/**
 * Process an byte from the telemetry stream.
 * \param[in] rxbyte Received byte
 * \return 0 Success
 * \return -1 Failure
 */
int32_t UAVTalkProcessInputStream(uint8_t rxbyte)
{
    static uint8_t tmpBuffer[4];
    static UAVObjHandle obj;
    static uint8_t type;
    static uint16_t packet_size;
    static uint32_t objId;
    static uint16_t instId;
    static uint32_t length;
    static uint8_t cs, csRx;
    static int32_t rxCount;
    static RxState state = STATE_SYNC;
    static uint16_t rxPacketLength = 0;

    ++stats.rxBytes;

    if (rxPacketLength < 0xffff)
    	rxPacketLength++;   // update packet byte count

    // Receive state machine
    switch (state)
    {
		case STATE_SYNC:
			if (rxbyte != SYNC_VAL)
				break;

			// Initialize and update the CRC
			cs = updateCRCbyte(0, rxbyte);

			rxPacketLength = 1;

			state = STATE_TYPE;
			break;

		case STATE_TYPE:

			// update the CRC
			cs = updateCRCbyte(cs, rxbyte);

			if ((rxbyte & TYPE_MASK) != TYPE_VER)
			{
				state = STATE_SYNC;
				break;
			}

			type = rxbyte;

			packet_size = 0;

			state = STATE_SIZE;
			rxCount = 0;
			break;

		case STATE_SIZE:

			// update the CRC
			cs = updateCRCbyte(cs, rxbyte);

			if (rxCount == 0)
			{
				packet_size += rxbyte;
				rxCount++;
				break;
			}

			packet_size += rxbyte << 8;

            if (packet_size < MIN_HEADER_LENGTH || packet_size > MAX_HEADER_LENGTH + MAX_PAYLOAD_LENGTH)
            {   // incorrect packet size
                state = STATE_SYNC;
                break;
            }

			rxCount = 0;
			state = STATE_OBJID;
			break;

		case STATE_OBJID:

			// update the CRC
			cs = updateCRCbyte(cs, rxbyte);

			tmpBuffer[rxCount++] = rxbyte;
			if (rxCount < 4)
				break;

			// Search for object, if not found reset state machine
			objId = (tmpBuffer[3] << 24) | (tmpBuffer[2] << 16) | (tmpBuffer[1] << 8) | (tmpBuffer[0]);
			obj = UAVObjGetByID(objId);
            if (obj == 0)
            {
                stats.rxErrors++;
                state = STATE_SYNC;
                break;
            }

            // Determine data length
            if (type == TYPE_OBJ_REQ || type == TYPE_ACK)
            	length = 0;
            else
				length = UAVObjGetNumBytes(obj);

            // Check length and determine next state
            if (length >= MAX_PAYLOAD_LENGTH)
			{
				stats.rxErrors++;
				state = STATE_SYNC;
				break;
			}

            // Check the lengths match
            if ((rxPacketLength + length) != packet_size)
            {   // packet error - mismatched packet size
                stats.rxErrors++;
                state = STATE_SYNC;
                break;
            }

            // Check if this is a single instance object (i.e. if the instance ID field is coming next)
			if (UAVObjIsSingleInstance(obj))
			{
				// If there is a payload get it, otherwise receive checksum
	        	if (length > 0)
	        		state = STATE_DATA;
	        	else
	        		state = STATE_CS;
				instId = 0;
				rxCount = 0;
			}
			else
			{
				state = STATE_INSTID;
				rxCount = 0;
			}

			break;

		case STATE_INSTID:

			// update the CRC
			cs = updateCRCbyte(cs, rxbyte);

			tmpBuffer[rxCount++] = rxbyte;
			if (rxCount < 2)
				break;

        	instId = (tmpBuffer[1] << 8) | (tmpBuffer[0]);

        	rxCount = 0;

        	// If there is a payload get it, otherwise receive checksum
        	if (length > 0)
        		state = STATE_DATA;
        	else
        		state = STATE_CS;

        	break;

		case STATE_DATA:

			// update the CRC
			cs = updateCRCbyte(cs, rxbyte);

			rxBuffer[rxCount++] = rxbyte;
			if (rxCount < length)
				break;

            state = STATE_CS;
            rxCount = 0;
            break;

		case STATE_CS:

			// the CRC byte
			csRx = rxbyte;

			if (csRx != cs)
			{   // packet error - faulty CRC
				stats.rxErrors++;
		        state = STATE_SYNC;
				break;
			}

            if (rxPacketLength != (packet_size + 1))
            {   // packet error - mismatched packet size
                stats.rxErrors++;
                state = STATE_SYNC;
                break;
            }

        	xSemaphoreTakeRecursive(lock, portMAX_DELAY);
				receiveObject(type, obj, instId, rxBuffer, length);
				stats.rxObjectBytes += length;
				stats.rxObjects++;
            xSemaphoreGiveRecursive(lock);

            state = STATE_SYNC;
            break;

		default:
			stats.rxErrors++;
			state = STATE_SYNC;
    }

    // Done
    return 0;
}

/**
 * Receive an object. This function process objects received through the telemetry stream.
 * \param[in] type Type of received message (TYPE_OBJ, TYPE_OBJ_REQ, TYPE_OBJ_ACK, TYPE_ACK)
 * \param[in] obj Handle of the received object
 * \param[in] instId The instance ID of UAVOBJ_ALL_INSTANCES for all instances.
 * \param[in] data Data buffer
 * \param[in] length Buffer length
 * \return 0 Success
 * \return -1 Failure
 */
static int32_t receiveObject(uint8_t type, UAVObjHandle obj, uint16_t instId, uint8_t* data, int32_t length)
{
    int32_t ret = 0;

    // Process message type
    switch (type) {
    case TYPE_OBJ:
        // All instances, not allowed for OBJ messages
        if (instId != UAVOBJ_ALL_INSTANCES)
        {
            // Unpack object, if the instance does not exist it will be created!
        	UAVObjUnpack(obj, instId, data);
            // Check if an ack is pending
            updateAck(obj, instId);
        }
        else
        {
            ret = -1;
        }
        break;
    case TYPE_OBJ_ACK:
        // All instances, not allowed for OBJ_ACK messages
        if (instId != UAVOBJ_ALL_INSTANCES)
        {
            // Unpack object, if the instance does not exist it will be created!
        	if ( UAVObjUnpack(obj, instId, data) == 0 )
        	{
        		// Transmit ACK
        		sendObject(obj, instId, TYPE_ACK);
        	}
        	else
        	{
        		ret = -1;
        	}
        }
        else
        {
        	ret = -1;
        }
        break;
    case TYPE_OBJ_REQ:
        // Send requested object if message is of type OBJ_REQ
    	sendObject(obj, instId, TYPE_OBJ);
        break;
    case TYPE_ACK:
        // All instances, not allowed for ACK messages
        if (instId != UAVOBJ_ALL_INSTANCES)
        {
            // Check if an ack is pending
            updateAck(obj, instId);
        }
        else
        {
        	ret = -1;
        }
        break;
    default:
        ret = -1;
    }
    // Done
    return ret;
}

/**
 * Check if an ack is pending on an object and give response semaphore
 */
static void updateAck(UAVObjHandle obj, uint16_t instId)
{
    if (respObj == obj && (respInstId == instId || respInstId == UAVOBJ_ALL_INSTANCES))
    {
    	xSemaphoreGive(respSema);
        respObj = 0;
    }
}

/**
 * Send an object through the telemetry link.
 * \param[in] obj Object handle to send
 * \param[in] instId The instance ID or UAVOBJ_ALL_INSTANCES for all instances
 * \param[in] type Transaction type
 * \return 0 Success
 * \return -1 Failure
 */
static int32_t sendObject(UAVObjHandle obj, uint16_t instId, uint8_t type)
{
	uint32_t numInst;
	uint32_t n;

	// If all instances are requested and this is a single instance object, force instance ID to zero
	if ( instId == UAVOBJ_ALL_INSTANCES && UAVObjIsSingleInstance(obj) )
	{
		instId = 0;
	}

    // Process message type
    if ( type == TYPE_OBJ || type == TYPE_OBJ_ACK )
    {
    	if (instId == UAVOBJ_ALL_INSTANCES)
    	{
			// Get number of instances
			numInst = UAVObjGetNumInstances(obj);
			// Send all instances
			for (n = 0; n < numInst; ++n)
			{
				sendSingleObject(obj, n, type);
			}
			return 0;
    	}
    	else
    	{
    		return sendSingleObject(obj, instId, type);
    	}
    }
    else if (type == TYPE_OBJ_REQ)
    {
        return sendSingleObject(obj, instId, TYPE_OBJ_REQ);
    }
    else if (type == TYPE_ACK)
    {
        if ( instId != UAVOBJ_ALL_INSTANCES )
        {
            return sendSingleObject(obj, instId, TYPE_ACK);
        }
        else
        {
            return -1;
        }
    }
    else
    {
        return -1;
    }
}

/**
 * Send an object through the telemetry link.
 * \param[in] obj Object handle to send
 * \param[in] instId The instance ID (can NOT be UAVOBJ_ALL_INSTANCES, use sendObject() instead)
 * \param[in] type Transaction type
 * \return 0 Success
 * \return -1 Failure
 */
static int32_t sendSingleObject(UAVObjHandle obj, uint16_t instId, uint8_t type)
{
    int32_t length;
    int32_t dataOffset;
    uint32_t objId;

    // Setup type and object id fields
    objId = UAVObjGetID(obj);
    txBuffer[0] = SYNC_VAL;  // sync byte
    txBuffer[1] = type;
	// data length inserted here below
    txBuffer[4] = (uint8_t)(objId & 0xFF);
    txBuffer[5] = (uint8_t)((objId >> 8) & 0xFF);
    txBuffer[6] = (uint8_t)((objId >> 16) & 0xFF);
    txBuffer[7] = (uint8_t)((objId >> 24) & 0xFF);

    // Setup instance ID if one is required
    if (UAVObjIsSingleInstance(obj))
    {
    	dataOffset = 8;
    }
    else
    {
    	txBuffer[8] = (uint8_t)(instId & 0xFF);
    	txBuffer[9] = (uint8_t)((instId >> 8) & 0xFF);
    	dataOffset = 10;
    }

    // Determine data length
    if (type == TYPE_OBJ_REQ || type == TYPE_ACK)
    {
    	length = 0;
    }
    else
    {
		length = UAVObjGetNumBytes(obj);
    }

    // Check length
    if (length >= MAX_PAYLOAD_LENGTH)
    {
    	return -1;
    }

    // Copy data (if any)
    if (length > 0)
    {
    	if ( UAVObjPack(obj, instId, &txBuffer[dataOffset]) < 0 )
    	{
    		return -1;
    	}
    }

    // Store the packet length
    txBuffer[2] = (uint8_t)((dataOffset+length) & 0xFF);
    txBuffer[3] = (uint8_t)(((dataOffset+length) >> 8) & 0xFF);

    // Calculate checksum
    txBuffer[dataOffset+length] = updateCRC(0, txBuffer, dataOffset+length);

    // Send buffer
    if (outStream!=NULL) (*outStream)(txBuffer, dataOffset+length+CHECKSUM_LENGTH);

    // Update stats
    ++stats.txObjects;
    stats.txBytes += dataOffset+length+CHECKSUM_LENGTH;
    stats.txObjectBytes += length;

    // Done
    return 0;
}

/**
 * Update the crc value with new data.
 *
 * Generated by pycrc v0.7.5, http://www.tty1.net/pycrc/
 * using the configuration:
 *    Width        = 8
 *    Poly         = 0x07
 *    XorIn        = 0x00
 *    ReflectIn    = False
 *    XorOut       = 0x00
 *    ReflectOut   = False
 *    Algorithm    = table-driven
 *
 * \param crc      The current crc value.
 * \param data     Pointer to a buffer of \a data_len bytes.
 * \param length   Number of bytes in the \a data buffer.
 * \return         The updated crc value.
 */
static uint8_t updateCRCbyte(uint8_t crc, const uint8_t data)
{
	return crc_table[crc ^ data];
}
static uint8_t updateCRC(uint8_t crc, const uint8_t* data, int32_t length)
{
	// use registers for speed
	register int32_t len = length;
	register uint8_t crc8 = crc;
	register const uint8_t *p = data;

    while (len--)
        crc8 = crc_table[crc8 ^ *p++];

    return crc8;
}

/**
 * @}
 * @}
 */