#include <stdio.h>
#include <string.h>
#include <time.h>
#include <Windows.h>


struct packet_s
{
    unsigned char data_size;
    unsigned char data[256];
};

enum _xfer_state_
{
    SEND_HEADER,
    SEND_DATA,
    SEND_COMPLETE,
    WAIT_FOR_ACK
};

enum _recv_state_
{
    RECV_HEADER,
    RECV_DATA,
    RECV_COMPLETE,
    SEND_ACK
};

enum _response_
{
    ACK = 0xE2,
    NACK = 0xF4
};

unsigned char _dummy[256];
unsigned char global_comm_buffer[8];
unsigned char comm;

DWORD WINAPI recv_data(void)
{
    struct packet_s packet;
    enum _recv_state_ recv_state = RECV_HEADER;
    unsigned char local_comm = 0;
    unsigned char data_recv;
    unsigned char* ptr_data;

    while (recv_state != RECV_COMPLETE) {

        switch (recv_state) {

        case RECV_HEADER:
            //insert your code here
            break;

        case RECV_DATA:
            //insert your code here
            break;

        case SEND_ACK:
            //insert your code here
            break;
        }
    }
    memcpy((void *)_dummy,(void*)packet.data,packet.data_size);
    printf("RECV Complete\r\n");
    return 0;
}


DWORD WINAPI xfer_data(struct packet_s* ptr_packet)
{
    enum _xfer_state_ xfer_state = SEND_HEADER;
    unsigned char local_comm = comm;
    unsigned char data_sent;
    unsigned char* ptr_data = ptr_packet->data;

    while (xfer_state != SEND_COMPLETE) {

        switch(xfer_state) {

        case SEND_HEADER:
            data_sent = 0;                                                      //total data sent
            global_comm_buffer[0] = ptr_packet->data_size;      //set byte zero of header packet to the total data size
            local_comm = comm ^= 1;                                     //flip the comm bit to let recieving side know data is there
            xfer_state = WAIT_FOR_ACK;                              //wait for the acknowledgement before advancing
            break;

        case SEND_DATA:
            memcpy((void *)&global_comm_buffer[0], (void*)ptr_data, 8);         //copy the appropriate amount of data into the comm buffer
            data_sent += 8;                                                                     //track the amount of data sent
            ptr_data += 8;                                                                      //advance the buffer pointer 8 bytes
            local_comm = comm ^= 1;                                                     //flip the comm bit to let recieving side know data is there
            xfer_state = WAIT_FOR_ACK;                                              //wait for the acknowledgement before advancing
            break;

        case WAIT_FOR_ACK:
            if (local_comm != comm) {                                       //wait for the acknowledgement before advancing (has the bit been changed?)
                if (global_comm_buffer[0] == ACK) {                 //was the response and ACK?
                    printf("Recieving ACK\r\n");
                    if (data_sent >= ptr_packet->data_size) {           //has all the data been sent?
                        xfer_state = SEND_COMPLETE;             //yes - complete and break the loop return to main thread
                    } else {
                        xfer_state = SEND_DATA;                         //no -- send the next chunk
                    }
                }
                else {
                    printf("Error Sending\r\n");
                    xfer_state = SEND_COMPLETE; //break loop and return
                }
            }
            break;
        }
    }
    printf("XFER Complete\r\n");
    return 0;
}



int main(void)
{
    struct packet_s packet;
    unsigned char* ptr_data = &packet.data[0];
    unsigned int buf_len;
    HANDLE threads[2];

    comm = 0;

    //designating random buffer sizes
    srand(time(NULL));
    buf_len = (unsigned int)rand() % 256;
    packet.data_size = buf_len;


    //fill with random data
    while(buf_len--) {
        *ptr_data++ = (unsigned char)rand()%256;
    }

    buf_len = packet.data_size;
    ptr_data = &packet.data[0];

    printf("Buffer Size: %u\r\n", packet.data_size);
    while(buf_len--) {
        printf("0x%02x ", *ptr_data++);
    }
    printf("\r\n");

    //create two threads recv and xfer
    threads[0] = CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)xfer_data,&packet,0,NULL);
    threads[1] = CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)recv_data,NULL,0,NULL);

    WaitForMultipleObjects(1,threads,TRUE,INFINITE);
    printf("Threads Complete\r\n");

    //compare the recieved buffer with the sent buffer
    if(memcmp((void*)packet.data,(void *)_dummy,packet.data_size) == 0) {
        printf("Challenge Completed Correctly\r\n");
    } else {
        printf("Incorrect Transfer\r\n");
    }

    getchar();

    return 0;
}