#include <stdint.h>
#include "boot.h"
#include "circ_buf.h"

#define CPUREG 0x00
#define CPUREG_ROM_DISABLE 0x01
#define CPUREG_BANK_SELECT 0x02
#define CPUREG_BANK_ENABLE 0x04
#define CPUREG_GPO_0 0x08
#define CPUREG_GPO_1 0x10
#define CPUREG_GPO_2 0x20
#define CPUREG_GPO_3 0x40
#define CPUREG_GPO_4 0x80
#define CPUREG_GPO_MASK 0xf8

#define UART_CTC_CARD_BASE 0x20

#define CTC_BASE (UART_CTC_CARD_BASE+0x00)
#define CTC_CHANNEL_0 (CTC_BASE+0)
#define CTC_CHANNEL_1 (CTC_BASE+1)
#define CTC_CHANNEL_2 (CTC_BASE+2)
#define CTC_CHANNEL_3 (CTC_BASE+3)

#define UART_BASE (UART_CTC_CARD_BASE+0x04)
#define UART_CONTROL (UART_BASE+0)
#define UART_DATA (UART_BASE+1)

volatile uint8_t v;
volatile uint8_t uart_tx_busy;
volatile circular_buffer_t rx_buf;
volatile circular_buffer_t tx_buf;

void uart_puts(char * c){
    while(*c){
        // fill tx buffer till it is full
        while(*c && buffer_enqueue(&tx_buf, *c)){
            c++;
        }
        // if uart not busy kick off
        if(!uart_tx_busy){
            disable_interrupts();
            char cc;
            if(buffer_dequeue(&tx_buf, &cc)){
                uart_tx_busy = 1;
                io_out(UART_DATA, cc);
                io_out(UART_CONTROL, 0b10110101);
            }
            enable_interrupts();
        }
    }
}

void uart_interrupt(){
    uint8_t status = io_in(UART_CONTROL);

    if((status&0x21)!=0){
        // RDRF or OVRN
        char c = io_in(UART_DATA);
        if((status&0x01)!=0){
            // RDRF
            buffer_enqueue(&rx_buf, c);
        }
    }

    if((status&0x02)!=0 && uart_tx_busy){
        //TXRE
        char c;
        if(buffer_dequeue(&tx_buf, &c)){
            io_out(UART_DATA, c);
        }else{
            io_out(UART_CONTROL, 0b10010101);
            uart_tx_busy = 0;
        }
    }
}

void ctc_interrupt(){
}

void main(){
    buffer_init(&rx_buf);
    buffer_init(&tx_buf);

    io_out(CTC_CHANNEL_0, 0x57); // no int, counter @ rising, value follows, soft reset, control word
    io_out(CTC_CHANNEL_0, 13); // 38.462 kHz out;

    io_out(CTC_CHANNEL_3, 0b11001111); // int, counter @ falling, ext trig, value follows, soft reset, control word
    io_out(CTC_CHANNEL_3, 1);

    io_out(CTC_CHANNEL_0, 0x00); // vector follows
    io_out(CTC_CHANNEL_0, 0x40);
    
    uart_tx_busy = 0;
    io_out(UART_CONTROL, 0b00000011); // master reset
    io_out(UART_CONTROL, 0b10010101); // recv int, 8N1, /16 -> 2403.85 baud
    
    enable_interrupts();

    uart_puts("Z80 monitor - v1\r\n");
    uart_puts("----------------\r\n");

    v = 0;
    for(;;){
        char c[2] = {0, 0};
        while(buffer_dequeue(&rx_buf, c)){
            uart_puts(c);
        }
    }
}