/*
 * Kangaroo Punch MultiPlayer Game Server Mark II
 * Copyright (C) 2020-2021  Scott Duensing
 *
 * 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, see <https://www.gnu.org/licenses/>.
 *
 */


#ifndef PACKET_H
#define PACKET_H


#include "os.h"


/*
 * Packet format (without framing):
 *
 * Byte 01:  cces ssss  - Two control bits, one encryption bit, five sequence bits.
 * Byte 02:  pppp pppp  - Eight bits, packet type.
 * Byte 03:  cccc cccc  - Eight bits, channel.
 * Byte 04:  dddd dddd  \
 * Byte ..:  dddd dddd   > Packet payload.
 * Byte X0:  dddd dddd  /
 * Byte X1:  cccc cccc  - Checksum
 *
 */


#define PACKET_MAX           1024  // Maximum number of bytes per packet
#define PACKET_SEQUENCE_MAX    32  // Five bits of data

#define PACKET_INPUT_QUEUE_SIZE  4096
#define PACKET_BUFFER_SIZE       (PACKET_MAX * 2 + 2 + 8)  // Worst case, every byte is a PACKET_FRAME.  Add two for ending frame.  Add 8 for worst case header and CRC.

#define PACKET_FRAME         0x7e

#define PACKET_CONTROL_DAT      0  // Regular data packet.
#define PACKET_CONTROL_RTX      1  // Retransmission packet.
#define PACKET_CONTROL_NAK      2  // Negative acknowledge.

#define PACKET_TYPE_NONE        0  // No packet.
#define PACKET_TYPE_TEST        1


typedef struct PacketDecodeDataS {
	// Output
	uint8_t   packetType;   // One of PACKET_TYPE_*
	char     *data;         // Buffer received.  MUST FREE.
	uint16_t  length;       // Length of buffer.
	uint8_t   channel;      // Which data channel it arrived on.
} PacketDecodeDataT;

typedef struct PacketEncodeDataS {
	// Input
	uint8_t   control;      // One of PACKET_CONTROL_*
	uint8_t   packetType;   // One of PACKET_TYPE_*
	uint8_t   channel;      // Which data channel to use.
	uint8_t   encrypt;      // Do we want the packet encrypted?
	// Input & Output
	uint16_t  sequence;     // For NAK packets, input the sequence number we missed.  Other packets returns the sequence of this packet.
	// Output
	char     *dataPointer;  // Buffer ready to send.  DO NOT FREE.
	uint16_t  length;       // Length of buffer.
} PacketEncodeDataT;

typedef struct PacketThreadDataS {
	// Internal state per thread for packet processing.
	uint8_t  sequence;
	char     decodeBuffer[PACKET_MAX];
	char     encodeBuffer[PACKET_BUFFER_SIZE];
	char     decodeQueue[PACKET_INPUT_QUEUE_SIZE];
	uint16_t decodeQueueHead;
	uint16_t decodeQueueTail;
	uint8_t  inEscape;
	uint8_t  newPacket;
} PacketThreadDataT;


uint8_t            packetDecode(PacketThreadDataT *threadData, PacketDecodeDataT *data, char *input, uint16_t length);
void               packetDecodeDataDestroy(PacketDecodeDataT **packet);
uint8_t            packetEncode(PacketThreadDataT *threadData, PacketEncodeDataT *data, char *input, uint16_t length);
PacketThreadDataT *packetThreadDataCreate(void);
void               packetThreadDataDestroy(PacketThreadDataT **data);


#endif // PACKET_H