//
//  Atari2600.cpp
//  CLK
//
//  Created by Thomas Harte on 14/07/2015.
//  Copyright © 2015 Thomas Harte. All rights reserved.
//

#include "Atari2600.hpp"
#include <algorithm>
#include <stdio.h>

using namespace Atari2600;
static const char atari2600DataType[] = "Atari2600";
static const int horizontalTimerReload = 227;

Machine::Machine()
{
	_timestamp = 0;
	_horizontalTimer = horizontalTimerReload;
	_lastOutputStateDuration = 0;
	_lastOutputState = OutputState::Sync;
	_crt = new Outputs::CRT(228, 262, 1, 4);
	_piaTimerStatus = 0xff;

	setup6502();
}

Machine::~Machine()
{
	delete _crt;
}

void Machine::switch_region()
{
	_crt->set_new_timing(228, 312);
}

void Machine::get_output_pixel(uint8_t *pixel, int offset)
{
	const uint8_t palette[16][3] =
	{
		{255, 255, 255},	{253, 250, 115},	{236, 199, 125},	{252, 187, 151},
		{252, 180, 181},	{235, 177, 223},	{211, 178, 250},	{187, 182, 250},
		{164, 186, 250},	{166, 201, 250},	{164, 224, 251},	{165, 251, 213},
		{185, 251, 187},	{201, 250, 168},	{225, 235, 160},	{252, 223, 145}
	};
	const uint8_t alphaValues[8] =
	{
		//		0, 64, 108, 144, 176, 200, 220, 255
		//	};
		//
		//	{
		69, 134, 108, 161, 186, 210, 235, 255
	};

	// get the playfield pixel and hence a proposed colour
	const int x = offset >> 2;
	const int mirrored = (x / 20) & (_playfieldControl&1);
	const int index = mirrored ? x - 20 : 19 - (x%20);
	const int byte = 2 - (index >> 3);
	const int lowestBit = (byte&1)^1;
	const int bit = (index & 7)^(lowestBit | (lowestBit << 1) | (lowestBit << 2));
	uint8_t playfieldPixel = (_playfield[byte] >> bit)&1;
	uint8_t playfieldColour = ((_playfieldControl&6) == 2) ? _playerColour[x / 20] : _playfieldColour;

	// get player and missile proposed pixels
	uint8_t playerPixels[2], missilePixels[2];
	for(int c = 0; c < 2; c++)
	{
		// figure out player colour
		int flipMask = (_playerReflection[c]&0x8) ? 0 : 7;

		int relativeTimer = _playerCounter[c] - 5;//_playerPosition[c] - _horizontalTimer;
		switch (_playerAndMissileSize[c]&7)
		{
			case 0: break;
			case 1:
				if (relativeTimer >= 16) relativeTimer -= 16;
			break;
			case 2:
				if (relativeTimer >= 32) relativeTimer -= 32;
			break;
			case 3:
				if (relativeTimer >= 32) relativeTimer -= 32;
				else if (relativeTimer >= 16) relativeTimer -= 16;
			break;
			case 4:
				if (relativeTimer >= 64) relativeTimer -= 64;
			break;
			case 5:
				relativeTimer >>= 1;
			break;
			case 6:
				if (relativeTimer >= 64) relativeTimer -= 64;
				else if (relativeTimer >= 32) relativeTimer -= 32;
			break;
			case 7:
				relativeTimer >>= 2;
			break;
		}

		if(relativeTimer >= 0 && relativeTimer < 8)
			playerPixels[c] = (_playerGraphics[c] >> (relativeTimer ^ flipMask)) &1;
		else
			playerPixels[c] = 0;

		// figure out missile colour
		int missileIndex = _missileCounter[c] - 4;
		int missileSize = 1 << ((_playerAndMissileSize[c] >> 4)&3);
		missilePixels[c] = (missileIndex >= 0 && missileIndex < missileSize && (_missileGraphicsEnable[c]&2)) ? 1 : 0;
	}

	// get the ball proposed colour
	uint8_t ballPixel;
	int ballIndex = _ballCounter - 4;
	int ballSize = 1 << ((_playfieldControl >> 4)&3);
	ballPixel = (ballIndex >= 0 && ballIndex < ballSize && (_ballGraphicsEnable&2)) ? 1 : 0;

	// apply appropriate priority to pick a colour
	playfieldPixel |= ballPixel;
	uint8_t outputColour = playfieldPixel ? playfieldColour : _backgroundColour;

	if(!(_playfieldControl&0x04) || !playfieldPixel) {
		if (playerPixels[1] || missilePixels[1]) outputColour = _playerColour[1];
		if (playerPixels[0] || missilePixels[0]) outputColour = _playerColour[0];
	}

	// map that colour to an RGBA
	pixel[0] = palette[outputColour >> 4][0];
	pixel[1] = palette[outputColour >> 4][1];
	pixel[2] = palette[outputColour >> 4][2];
	pixel[3] = alphaValues[(outputColour >> 1)&7];
}

void Machine::output_pixels(int count)
{
	const int32_t start_of_sync = 214;
	const int32_t end_of_sync = 198;

	_timestamp += count;
	while(count--)
	{
		OutputState state;

		// update hmove
		if (!(_horizontalTimer&3) && _hMoveFlags) {
			if (_hMoveFlags&1) _playerCounter[0] = (_playerCounter[0]+1)%160;
			if (_hMoveFlags&2) _playerCounter[1] = (_playerCounter[1]+1)%160;
			if (_hMoveFlags&4) _missileCounter[0] = (_missileCounter[0]+1)%160;
			if (_hMoveFlags&8) _missileCounter[1] = (_missileCounter[1]+1)%160;
			if (_hMoveFlags&16) _ballCounter = (_ballCounter+1)%160;

			_hMoveCounter --;

			if ((_hMoveCounter^8^(_playerMotion[0] >> 4)) == 0xf) _hMoveFlags &= ~1;
			if ((_hMoveCounter^8^(_playerMotion[1] >> 4)) == 0xf) _hMoveFlags &= ~2;
			if ((_hMoveCounter^8^(_missileMotion[0] >> 4)) == 0xf) _hMoveFlags &= ~4;
			if ((_hMoveCounter^8^(_missileMotion[1] >> 4)) == 0xf) _hMoveFlags &= ~8;
			if ((_hMoveCounter^8^(_ballMotion >> 4)) == 0xf) _hMoveFlags &= ~16;
		}

		// logic: if in vsync, output that; otherwise if in vblank then output that;
		// otherwise output a pixel
		if(_vSyncEnabled) {
			state = (_horizontalTimer < start_of_sync) ? OutputState::Sync : OutputState::Blank;
		} else {

			// blank is decoded as 68 counts; sync and colour burst as 16 counts

			// 4 blank
			// 4 sync
			// 9 'blank'; colour burst after 4
			// 40 pixels

			// it'll be about 43 cycles from start of hsync to start of visible frame, so...
			// guesses, until I can find information: 26 cycles blank, 16 sync, 40 blank, 160 pixels
			if(_horizontalTimer >= start_of_sync) state = OutputState::Blank;
			else if (_horizontalTimer >= end_of_sync) state = OutputState::Sync;
			else if (_horizontalTimer >= (_vBlankExtend ? 152 : 160)) state = OutputState::Blank;
			else {
				if(_vBlankEnabled) {
					state = OutputState::Blank;
				} else {
					state = OutputState::Pixel;
				}
			}
		}

		_lastOutputStateDuration++;
		if(state != _lastOutputState)
		{
			switch(_lastOutputState)
			{
				case OutputState::Blank:	_crt->output_blank(_lastOutputStateDuration);					break;
				case OutputState::Sync:		_crt->output_sync(_lastOutputStateDuration);					break;
				case OutputState::Pixel:	_crt->output_data(_lastOutputStateDuration, atari2600DataType);	break;
			}
			_lastOutputStateDuration = 0;
			_lastOutputState = state;

			if(state == OutputState::Pixel)
			{
				_vBlankExtend = false;
				_crt->allocate_write_area(160);
				_outputBuffer = _crt->get_write_target_for_buffer(0);
			}
		}

		if(state == OutputState::Pixel)
		{
			if(_outputBuffer)
				get_output_pixel(&_outputBuffer[_lastOutputStateDuration * 4], 159 - _horizontalTimer);

			// increment all graphics counters
			_playerCounter[0] = (_playerCounter[0]+1)%160;
			_playerCounter[1] = (_playerCounter[1]+1)%160;
			_missileCounter[0] = (_missileCounter[0]+1)%160;
			_missileCounter[1] = (_missileCounter[1]+1)%160;
			_ballCounter = (_ballCounter+1)%160;
		}

		// assumption here: signed shifts right; otherwise it's just
		// an attempt to avoid both the % operator and a conditional
		_horizontalTimer--;
		const int32_t sign_extension = _horizontalTimer >> 31;
		_horizontalTimer = (_horizontalTimer&~sign_extension) | (sign_extension&horizontalTimerReload);
	}
}

int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value)
{
	uint8_t returnValue = 0xff;
	int cycles_run_for = 1;
	const int32_t ready_line_disable_time = horizontalTimerReload - 3;

	if(operation == CPU6502::BusOperation::Ready) {
		int32_t distance_to_end_of_ready = _horizontalTimer - ready_line_disable_time + horizontalTimerReload;
		cycles_run_for = distance_to_end_of_ready / 3;
		output_pixels(distance_to_end_of_ready);
		set_ready_line(false);
	} else {
		output_pixels(3);
		if(_horizontalTimer == ready_line_disable_time)
			set_ready_line(false);
	}

	if(operation != CPU6502::BusOperation::Ready) {

		// check for a ROM access
		if ((address&0x1000) && isReadOperation(operation)) {
			returnValue &= _rom[address&_romMask];
		}

		// check for a RAM access
		if ((address&0x1280) == 0x80) {

			if(isReadOperation(operation)) {
				returnValue &= _ram[address&0x7f];
			} else {
				_ram[address&0x7f] = *value;
			}
		}

		// check for a TIA access
		if (!(address&0x1080)) {
			if(isReadOperation(operation)) {
				switch(address & 0xf) {
					case 0x00:	returnValue &= 0x3f;	break;	// missile 0 / player collisions
					case 0x01:	returnValue &= 0x3f;	break;	// missile 1 / player collisions
					case 0x02:	returnValue &= 0x3f;	break;	// player 0 / playfield / ball collisions
					case 0x03:	returnValue &= 0x3f;	break;	// player 1 / playfield / ball collisions
					case 0x04:	returnValue &= 0x3f;	break;	// missile 0 / playfield / ball collisions
					case 0x05:	returnValue &= 0x3f;	break;	// missile 1 / playfield / ball collisions
					case 0x06:	returnValue &= 0x7f;	break;	// ball / playfield collisions
					case 0x07:	returnValue &= 0x3f;	break;	// player / player, missile / missile collisions
				}
			} else {
				switch(address & 0x3f) {
					case 0x00:	_vSyncEnabled = !!(*value & 0x02);	break;
					case 0x01:	_vBlankEnabled = !!(*value & 0x02);	break;

					case 0x02: {
						set_ready_line(true);
					} break;
					case 0x03: _horizontalTimer = horizontalTimerReload; break;

					case 0x04: _playerAndMissileSize[0] = *value;	break;
					case 0x05: _playerAndMissileSize[1] = *value;	break;

					case 0x06: _playerColour[0] = *value;	break;
					case 0x07: _playerColour[1] = *value;	break;
					case 0x08: _playfieldColour = *value;	break;
					case 0x09: _backgroundColour = *value;	break;

					case 0x0a: _playfieldControl = *value;		break;
					case 0x0b: _playerReflection[0] = *value;	break;
					case 0x0c: _playerReflection[1] = *value;	break;
					case 0x0d: _playfield[0] = *value;			break;
					case 0x0e: _playfield[1] = *value;			break;
					case 0x0f: _playfield[2] = *value;			break;

					case 0x10: _playerCounter[0] = 0;		break;
					case 0x11: _playerCounter[1] = 0;		break;
					case 0x12: _missileCounter[0] = 0;		break;
					case 0x13: _missileCounter[1] = 0;		break;
					case 0x14: _ballCounter = 0;			break;

					case 0x1c:
						_ballGraphicsEnable = _ballGraphicsEnableLatch;
					case 0x1b: {
						int index = (address & 0x3f) - 0x1b;
						_playerGraphicsLatch[index] = *value;
						if(!(_playerGraphicsLatchEnable[index]&1))
							_playerGraphics[index] = _playerGraphicsLatch[index];
						_playerGraphics[index^1] = _playerGraphicsLatch[index^1];
					} break;
					case 0x1d: _missileGraphicsEnable[0] = *value;	break;
					case 0x1e: _missileGraphicsEnable[1] = *value;	break;
					case 0x1f:
						_ballGraphicsEnableLatch = *value;
						if(!(_ballGraphicsEnableDelay&1))
							_ballGraphicsEnable = _ballGraphicsEnableLatch;
					break;

					case 0x20: _playerMotion[0] = *value;			break;
					case 0x21: _playerMotion[1] = *value;			break;
					case 0x22: _missileMotion[0] = *value;			break;
					case 0x23: _missileMotion[1] = *value;			break;
					case 0x24: _ballMotion = *value;				break;

					case 0x25: _playerGraphicsLatchEnable[0] = *value;	break;
					case 0x26: _playerGraphicsLatchEnable[1] = *value;	break;
					case 0x27: _ballGraphicsEnableDelay = *value;		break;

	//				case 0x28: _missilePosition[0] = _playerPosition[0];	break;

					case 0x2a:
						_vBlankExtend = true;
						_hMoveCounter = 15;
						_hMoveFlags = 0x1f;
					break;
					case 0x2b: _playerMotion[0] = _playerMotion[1] = _missileMotion[0] = _missileMotion[1] = _ballMotion = 0; break;
				}
			}
	//		printf("Uncaught TIA %04x\n", address);
		}

		// check for a PIA access
		if ((address&0x1280) == 0x280) {
			if(isReadOperation(operation)) {
				switch(address & 0xf) {
					case 0x04: returnValue &= _piaTimerValue >> _piaTimerShift;				break;
					case 0x05: returnValue &= _piaTimerStatus; _piaTimerStatus &= ~0x40;	break;
				}
			} else {
				switch(address & 0x0f) {
					case 0x04:	_piaTimerShift = 0;		_piaTimerValue = *value << 0;   _piaTimerStatus &= ~0xc0;   break;
					case 0x05:	_piaTimerShift = 3;		_piaTimerValue = *value << 3;   _piaTimerStatus &= ~0xc0;   break;
					case 0x06:	_piaTimerShift = 6;		_piaTimerValue = *value << 6;   _piaTimerStatus &= ~0xc0;   break;
					case 0x07:	_piaTimerShift = 10;	_piaTimerValue = *value << 10;  _piaTimerStatus &= ~0xc0;   break;
				}
			}
	//		printf("Uncaught PIA %04x\n", address);
		}

		if(isReadOperation(operation)) {
			*value = returnValue;
		}
	}

	if(_piaTimerValue >= cycles_run_for) {
		_piaTimerValue -= cycles_run_for;
	} else {
		_piaTimerValue += 0xff - cycles_run_for;
		_piaTimerShift = 0;
		_piaTimerStatus |= 0xc0;
	}

	return  cycles_run_for;
}

void Machine::set_rom(size_t length, const uint8_t *data)
{
	length = std::min((size_t)4096, length);
	memcpy(_rom, data, length);
	_romMask = length - 1;
}