#include <go32.h>

#include "Timer.h"

#include "Pic.h"
#include "../util/Asm.h"

#define PIT_FREQ 1193181
#define PIT_MODE_CH0 0x00
#define PIT_MODE_CH1 0x40
#define PIT_MODE_CH2 0x80
#define PIT_MODE_ACCESS_LO 0x10
#define PIT_MODE_ACCESS_HI 0x20
#define PIT_MODE_ACCESS_LOHI 0x30
#define PIT_MODE_M0 0x00
#define PIT_MODE_M1 0x02
#define PIT_MODE_M2 0x04
#define PIT_MODE_M3 0x06
#define PIT_MODE_M4 0x08
#define PIT_MODE_M5 0x0a
#define PIT_MODE_BIN 0x00
#define PIT_MODE_BCD 0x01

#define PIT_REG_CH0 0x40
#define PIT_REG_CH1 0x41
#define PIT_REG_CH2 0x42
#define PIT_REG_MODE 0x43

Timer timer;

void timerISR() {
	timer.update();
}

Timer::Timer() {
	_go32_dpmi_get_protected_mode_interrupt_vector(8, &_oldIsr);
	
	_newIsr.pm_offset = reinterpret_cast<int>(timerISR);
    _newIsr.pm_selector = _go32_my_cs();
    _go32_dpmi_allocate_iret_wrapper(&_newIsr);
	_go32_dpmi_set_protected_mode_interrupt_vector(8, &_newIsr);
}

Timer::~Timer() {
	setDivider(65535);
	_go32_dpmi_set_protected_mode_interrupt_vector(8, &_oldIsr);
	_go32_dpmi_free_iret_wrapper(&_newIsr);
}

void Timer::update() {
	_ticks++;
	
	if (_callback) _callback();
	
	_elapsed += _div;
	if (_elapsed >= 65535) {
		_elapsed -= 65535;
		// TODO call old isr
		// Documentation is kind of nonexistant so we will not call the handler for now
		Pic::clearInterrupt();
	} else {
		Pic::clearInterrupt();
	}
}

uint32_t Timer::getTicks() const {
	return _ticks;
}

void Timer::setFrequency(uint16_t freq) {
	setDivider(PIT_FREQ / freq);
}

void Timer::setDivider(uint16_t div) {
	auto wasEnabled = interruptsEnabled();
	disableInterrupts();
	
	_div = div;
	
	// Update PIT frequency
    outb(PIT_REG_MODE, PIT_MODE_CH0|PIT_MODE_ACCESS_LOHI|PIT_MODE_M2|PIT_MODE_BIN);
    outb(PIT_REG_CH0, _div & 0xff);
    outb(PIT_REG_CH0, (_div >> 8) & 0xff);
	
	if (1) enableInterrupts();
}

Timer::Callback Timer::setCallback(Timer::Callback callback) {
	auto oldCallback = _callback;
	_callback = callback;
	return oldCallback;
}