#include <dos.h>
#include <sys/nearptr.h>

#include "../Video.h"
#include "../../util/Asm.h"
#include "../../util/Log.h"

#define VGA_DAC_ADDR_RD 0x3c7
#define VGA_DAC_ADDR_WR 0x3c8
#define VGA_DAC_DATA 0x3c9
#define VGA_EXT_INPUT_STATUS 0x3da
#define VGA_EXT_INPUT_STATUS_VRETRACE 8

Video video;

Video::Video() {
	__djgpp_nearptr_enable();

	// Store current video mode
	_oldMode = GetMode();

	// Store current palette
	for (auto i = 0; i < 256; i++) {
		GetPaletteEntry(i, &_oldPalette[i]);
	}
}

Video::~Video() {
	exit();
}

void Video::enter() {
	SetMode(0x13);
}

void Video::exit() {
	// Restore old palette
	for (auto i = 0; i < 256; i++) {
		SetPaletteEntry(i, &_oldPalette[i]);
	}

	// Restore old video mode
	SetMode(_oldMode);
}

void Video::SetMode(uint8_t mode) {
	union REGS regs;
	regs.h.ah = 0x00;
	regs.h.al = mode;
	int86(0x10, &regs, &regs);

	//__djgpp_nearptr_enable();
	switch (mode) {
		default:
		case 0x13:
			_fb = (uint8_t *)(0xA0000 + __djgpp_conventional_base);

	}
}

uint8_t Video::GetMode() {
	union REGS regs;
	regs.h.ah = 0x0f;
	regs.h.al = 0;
	int86(0x10, &regs, &regs);

	return regs.h.al;
}

void Video::SetPaletteEntry(uint8_t index, PaletteEntry entry) {
	SetPaletteEntry(index, &entry);
}

Video::PaletteEntry Video::GetPaletteEntry(uint8_t index) {
	PaletteEntry entry;
	GetPaletteEntry(index, &entry);
	return entry;
}

void Video::SetPaletteEntry(uint8_t index, PaletteEntry *entry) {
	outb(VGA_DAC_ADDR_WR, index);
	outb(VGA_DAC_DATA, entry->r >> 2);
	outb(VGA_DAC_DATA, entry->g >> 2);
	outb(VGA_DAC_DATA, entry->b >> 2);
}

void Video::GetPaletteEntry(uint8_t index, PaletteEntry *entry) {
	outb(VGA_DAC_ADDR_RD, index);
	entry->r = inb(VGA_DAC_DATA);
	entry->g = inb(VGA_DAC_DATA);
	entry->b = inb(VGA_DAC_DATA);
}

void *Video::GetFB() {
	return _renderBuffer;
}

void Video::WaitForVerticalSync() {
	auto state = inb(VGA_EXT_INPUT_STATUS) & VGA_EXT_INPUT_STATUS_VRETRACE;
	if (!state) {
		// We started before a retrace, so wait until it begins
		while (!(inb(VGA_EXT_INPUT_STATUS) & VGA_EXT_INPUT_STATUS_VRETRACE)) {}
	}
	// Wait until it ends
	while (inb(VGA_EXT_INPUT_STATUS) & VGA_EXT_INPUT_STATUS_VRETRACE);
}

void Video::UpdateRect(const Rect &rect) {
	// Merge rect if it overlaps with an existing rect
	for (auto i = 0; i < _updateRectIndex; i++) {
		auto &r = _updatedRects[i];
		if (r.overlaps(rect)) {
			r += rect;
			return;
		}
	}

	// Add a new rect to the list
	_updatedRects[_updateRectIndex++] = rect;
}

void Video::Flip() {
	for (auto i = 0; i <= MAX_UPDATE_RECT_INDEX; i++) {
		auto &rect = _updatedRects[i];
		for (auto y = rect.y1; y <= rect.y2; y++) {
			auto yOffset = y * SCREEN_WIDTH;

			for (auto x = rect.x1; x <= rect.x2; x++) {
				_fb[yOffset + x] = _renderBuffer[yOffset + x];
			}
		}
	}

	_updateRectIndex = 0;
}