#include "6522.h"

void via_init(via_t *via) {
	via->ira = 0;
	via->irb = 0;
	via->ora = 0;
	via->orb = 0;
	via->ddra = 0;
	via->ddrb = 0;
	via->tca = 0;
	via->tcb = 0;
	via->tla = 0;
	via->tlb = 0;
	via->acr = 0;
	via->pcr = 0;
	via->ifr = 0;
	via->ier = 0;

	via->tav = true;
	via->tbv = true;
}

void via_read(via_t *via, uint8_t addr, uint8_t *v, uint8_t cycle) {
	uint16_t tca = via->tca - cycle;
	uint16_t tcb = via->tcb - cycle;

	switch (addr) {
		case 0:
			via_pb_read(via, cycle);
			*v = (via->irb & ~via->ddrb) | (via->orb & via->ddrb);
			via->ifr &= 0b11100111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 1:
			via_pa_read(via, cycle);
			*v = via->ira;
			via->ifr &= 0b11111100;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 2:
			*v = via->ddrb;
			break;
		case 3:
			*v = via->ddra;
			break;
		case 4:
			*v = tca & 0xff;
			via->ifr &= 0b10111111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 5:
			*v = (tca & 0xff00) >> 8;
			break;
		case 6:
			*v = via->tla & 0xff;
			break;
		case 7:
			*v = (via->tla & 0xff00) >> 8;
			break;
		case 8:
			*v = tcb & 0xff;
			via->ifr &= 0b11011111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 9:
			*v = (tcb & 0xff00) >> 8;
		case 11:
			*v = via->acr;
			break;
		case 12:
			*v = via->pcr;
			break;
		case 13:
			*v = via->ifr;
			break;
		case 14:
			*v = via->ier | 0x80;
			break;
		default:
			break;
	}
}

void via_write(via_t *via, uint8_t addr, uint8_t v, uint8_t cycle) {
	switch (addr) {
		case 0:
			via->orb = v;
			via_pb_write(via, cycle);
			via->ifr &= 0b11100111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 1:
			via->ora = v;
			via_pa_write(via, cycle);
			via->ifr &= 0b11111100;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 2:
			via->ddrb = v;
			via_pb_write(via, cycle);
			break;
		case 3:
			via->ddra = v;
			via_pa_write(via, cycle);
			break;
		case 4:
			via->tla = (via->tla & 0xff00) | v;
			break;
		case 5:
			via->tla = (via->tla & 0xff) | (v << 8);
			via->tca = via->tla + cycle + 1;
			via->ifr &= 0b10111111;
			if (via->ifr == 0x80) via->ifr = 0;
			via->tav = false;
			break;
		case 6:
			via->tla = (via->tla & 0xff00) | v;
			break;
		case 7:
			via->tla = (via->tla & 0xff) | (v << 8);
			via->ifr &= 0b10111111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 8:
			via->tlb = (via->tlb & 0xff00) | v;
			break;
		case 9:
			via->tlb = (via->tlb & 0xff) | (v << 8);
			via->tcb = via->tlb + cycle + 1;
			via->tbv = false;
			via->ifr &= 0b11011111;
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 11:
			via->acr = v;
			break;
		case 12:
			via->pcr = v;
			break;
		case 13:
			via->ifr &= ~(v & 0x7f);
			if (via->ifr == 0x80) via->ifr = 0;
			break;
		case 14:
			if (v & 0x80) {
				via->ier |= v & 0x7f;
			} else {
				via->ier &= ~v;
			}
			break;
		default:
			break;
	}
}

void via_cycle(via_t *via, uint8_t cycles) {
	if (!via->tav) {
		uint16_t tca = via->tca - cycles;

		if (tca > via->tca) {
			via->ifr |= 0b11000000;
			if ((via->acr & 0b01000000) == 0) {
				tca = via->tla;
				via->tav = true;
			} else {
				tca = via->tla + tca + 1;
			}
		}

		via->tca = tca;
	}

	uint16_t tcb = via->tcb - cycles;

	if (tcb > via->tcb) {
		if (!via->tbv) {
			via->ifr |= 0b10100000;
		}
		via->tbv = true;
	}

	via->tcb = tcb;
}

bool via_irq(via_t *via) {
	return (via->ifr & via->ier) > 0;
}