#include "vt1200_board.h"

bool vt1200_board::is_switch_port(uint32_t addr) const
{
	// The monitor-selection switch lives in bits 4-6 of window 3's +0xD0
	// register (harness offset 0x0d).
	return addr == (VT1200_WIN3 + VT1200_OFF_SWITCH);
}

uint16_t vt1200_board::read(uint32_t addr)
{
	auto ov = m_override.find(addr);
	if (ov != m_override.end())
		return ov->second;

	uint16_t value = m_default;
	auto st = m_store.find(addr);
	if (st != m_store.end())
		value = st->second;

	// DMA command port: while a command is in flight the port reads back the
	// latched command; once the configured ticks elapse it reads back 0.
	if (m_dma_ticks > 0 && (addr & 0xffff0000) == VT1200_WIN1)
		return (m_dma_left > 0) ? m_dma_cmd : (uint16_t)0x0000;

	if (m_switch_set && is_switch_port(addr))
		return (uint16_t)((value & 0xff8f) | (m_switch_bits & 0x0070));

	if (m_handshake && (addr & 0xffff) == VT1200_OFF_STATUS)
	{
		auto busy = m_busy_left.find(addr & 0xffff0000);
		if (busy != m_busy_left.end() && busy->second > 0)
			value |= 0x0001;
		else
			value &= ~0x0001;
	}
	return value;
}

void vt1200_board::write(uint32_t addr, uint16_t data)
{
	m_store[addr] = data;
	if (m_handshake && (addr & 0xffff) == VT1200_OFF_CMD)
	{
		const uint32_t win = addr & 0xffff0000;
		auto ticks = m_busy_ticks_by_win.find(win);
		m_busy_left[win] = (ticks != m_busy_ticks_by_win.end()) ? ticks->second : 0;
	}

	// A command written to the DMA command port (WIN1) is latched and, when the
	// DMA model is configured, starts its completion timer.
	if ((addr & 0xffff0000) == VT1200_WIN1)
	{
		m_dma_cmd = data;
		if (m_dma_ticks > 0)
			m_dma_left = m_dma_ticks;
	}
}

void vt1200_board::tick()
{
	// Advance every window's state machine, not just the one last touched.
	for (auto &entry : m_busy_left)
		if (entry.second > 0)
			entry.second--;

	// Merge the DMA pair's timer into the same tick.
	if (m_dma_left > 0)
		m_dma_left--;
}