#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

#include <tabby/avr/printer.h>
#include <tabby/avr/uart.h>
#include <tabby/avr/link.h>
#include <tabby/avr.h>

static volatile uint16_t offset_header = 0,
                         offset_body   = 0,
                         size_body     = 0,
                         sum_calc      = 0,
                         sum_footer    = 0;

static volatile tabby_printer_response response = {
    .device = TABBY_PRINTER_DEVICE_ID,
    .status = TABBY_PRINTER_OK
};

/*
 * SPI byte receipt interrupt vector
 */
ISR(SPI_STC_vect) {
    uint8_t in  = SPDR,
            out = 0;

    uart_putchar(in, NULL);

    switch (offset_header) {
        case 0: {
            if (in == TABBY_PRINTER_SYNC_1) {
                offset_header++;
                offset_body = 0;
                sum_calc    = 0;

                response.status = TABBY_PRINTER_OK;
            }

            break;
        }

        case 1: {
            if (in == TABBY_PRINTER_SYNC_2) {
                offset_header++;
            } else {
                offset_header = 0;
            }

            break;
        }

        case 2:
        case 3: {
            offset_header++;
            sum_calc += in;

            break;
        }

        case 4: {
            size_body = in;

            sum_calc += in;
            offset_header++;

            break;
        }

        case 5: {
            size_body |= in << 8;

            if (size_body > TABBY_PRINTER_PACKET_MAX_SIZE) {
                offset_header = 0;
            } else {
                offset_header++;
            }

            sum_calc += in;

            break;
        }

        default: {
            if (offset_body < size_body) {
                offset_body++;
                sum_calc += in;
            } else if (offset_body == size_body) {
                offset_body++;
                sum_footer = in;
            } else if (offset_body == size_body + 1) {
                offset_body++;

                sum_footer |= in << 8;

                if (sum_footer != sum_calc) {
                    response.status |= TABBY_PRINTER_SUM;
                }

                out = response.device;
            } else if (offset_body == size_body + 2) {
                offset_body++;

                out = response.status;
            } else if (offset_body == size_body + 3) {
                offset_header = 0;
            }
        }
    }

    SPDR = out;
}

int main() {
    uart_init();

    tabby_avr_link_init_slave();

    sei();

    while (1) {
        sleep_mode();
    }

    return 0;
}