// ----------------------------------------------------------------------------
//   ___  ___  ___  ___       ___  ____  ___  _  _      __  ___
//  /__/ /__/ /  / /__  /__/ /__    /   /_   / |/ /      / / _
// /    / \  /__/ ___/ ___/ ___/   /   /__  /    /   ___/ /__/
//
// ----------------------------------------------------------------------------
// Copyright 2005 Greg Stanton
// Copyright 2020 Rupert Carmichael
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
// ----------------------------------------------------------------------------
// TiaSound is Copyright(c) 1997 by Ron Fries
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of version 2 of the GNU Library General Public License
// as published by the Free Software Foundation.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library
// General Public License for more details.
// To obtain a copy of the GNU Library General Public License, write to the
// Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// Any permitted reproduction of these routines, in whole or in part, must
// bear this legend.
// ----------------------------------------------------------------------------
// Tia.c
// ----------------------------------------------------------------------------
#include <stddef.h>
#include <stdint.h>

#include "Tia.h"
#define TIA_POLY4_SIZE 15
#define TIA_POLY5_SIZE 31
#define TIA_POLY9_SIZE 511

uint8_t tia_buffer[TIA_BUFFER_SIZE] = {0};
uint32_t tia_size = TIA_BUFFER_SIZE; // previously was 524

static const uint8_t TIA_POLY4[] = {1,1,0,1,1,1,0,0,0,0,1,0,1,0,0};
static const uint8_t TIA_POLY5[] = {0,0,1,0,1,1,0,0,1,1,1,1,1,0,0,0,1,1,0,1,1,1,0,1,0,1,0,0,0,0,1};
static const uint8_t TIA_POLY9[] = {0,0,1,0,1,0,0,0,1,0,0,0,0,0,0,0,1,0,1,1,1,0,0,1,0,1,0,0,1,1,1,1,1,0,0,1,1,0,1,1,0,1,0,1,1,1,0,1,1,0,0,1,0,0,1,1,1,1,0,1,0,0,0,0,1,1,0,1,1,0,0,0,1,0,0,0,1,1,1,1,0,1,0,1,1,0,1,0,1,0,0,0,0,1,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,1,1,0,0,1,1,0,1,1,0,0,1,1,1,1,1,0,0,1,1,0,0,0,1,1,0,1,0,0,0,1,1,0,0,1,1,1,1,0,0,1,0,0,0,1,1,1,0,0,1,1,0,1,0,1,1,0,1,1,0,1,0,0,1,0,0,1,1,1,1,1,1,0,1,1,1,1,0,1,1,0,0,0,0,1,1,1,1,1,0,0,0,1,0,0,0,0,1,0,0,0,1,0,1,0,1,1,0,0,0,0,1,0,1,1,1,1,0,1,0,0,0,1,1,0,0,0,1,1,1,0,1,1,1,0,1,0,0,0,0,0,0,0,0,1,0,1,0,0,1,0,0,0,0,1,1,1,0,0,0,1,1,1,0,0,1,1,0,0,1,0,0,1,0,1,1,0,0,0,0,1,0,0,0,1,0,0,0,1,0,1,1,1,1,0,0,0,1,1,1,0,0,0,1,0,0,1,1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,0,1,0,1,1,1,1,0,0,1,0,1,0,1,1,1,0,0,0,0,0,1,1,0,1,1,0,0,0,1,0,1,0,1,0,0,0,0,1,0,1,1,1,0,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,1,1,0,0,1,1,1,1,1,1,1,0,0,0,0,0,1,0,0,1,1,0,1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,1,0,1,0,0,0,0,0,1,1,1,1,0,0,1,0,0,1,0,1,1,1,1,1,1,1,0,1,0,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,0,1,0,0,1,0,1,0,1,0,1,1,1,0,0,1,0,1,1,0,0,1,1,1,1,1,0,0,0,1,1,0};
static const uint8_t TIA_DIV31[] = {1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0};
static uint8_t tia_volume[2] = {0};
static uint8_t tia_counterMax[2] = {0};
static uint8_t tia_counter[2] = {0};
static uint8_t tia_audc[2] = {0};
static uint8_t tia_audf[2] = {0};
static uint8_t tia_audv[2] = {0};
static uint32_t tia_poly4Cntr[2] = {0};
static uint32_t tia_poly5Cntr[2] = {0};
static uint32_t tia_poly9Cntr[2] = {0};
static uint32_t tia_soundCntr = 0;

static void tia_ProcessChannel(uint8_t channel) {
    tia_poly5Cntr[channel]++;
    
    if (tia_poly5Cntr[channel] == TIA_POLY5_SIZE) {
        tia_poly5Cntr[channel] = 0;
    }
    
    if (((tia_audc[channel] & 2) == 0) || (((tia_audc[channel] & 1) == 0) && TIA_DIV31[tia_poly5Cntr[channel]]) || (((tia_audc[channel] & 1) == 1) && TIA_POLY5[tia_poly5Cntr[channel]])) {
        if(tia_audc[channel] & 4) {
            tia_volume[channel] = (!tia_volume[channel])? tia_audv[channel]: 0;
        }
        else if (tia_audc[channel] & 8) {
            if (tia_audc[channel] == 8) {
                tia_poly9Cntr[channel]++;
                
                if (tia_poly9Cntr[channel] == TIA_POLY9_SIZE) {
                    tia_poly9Cntr[channel] = 0;
                }
                
                tia_volume[channel] = (TIA_POLY9[tia_poly9Cntr[channel]])? tia_audv[channel]: 0;
            }
            else {
                tia_volume[channel] = (TIA_POLY5[tia_poly5Cntr[channel]])? tia_audv[channel]: 0;
            }
        }
        else {
            tia_poly4Cntr[channel]++;
            
            if (tia_poly4Cntr[channel] == TIA_POLY4_SIZE) {
                tia_poly4Cntr[channel] = 0;
            }
            
            tia_volume[channel] = (TIA_POLY4[tia_poly4Cntr[channel]])? tia_audv[channel]: 0;
        }
    }
}

void tia_Reset(void) {
    tia_soundCntr = 0;
    
    for (int index = 0; index < 2; index++) {
        tia_volume[index] = 0;
        tia_counterMax[index] = 0;
        tia_counter[index] = 0;
        tia_audc[index] = 0;
        tia_audf[index] = 0;
        tia_audv[index] = 0;
        tia_poly4Cntr[index] = 0;
        tia_poly5Cntr[index] = 0;
        tia_poly9Cntr[index] = 0;
    }
    
    tia_Clear();
}

void tia_Clear(void) {
    for (int index = 0; index < TIA_BUFFER_SIZE; index++) {
        tia_buffer[index] = 0;
    }
}

void tia_SetRegister(uint16_t address, uint8_t data) {
    uint8_t channel;
    uint8_t frequency;

    switch (address) {
        case AUDC0:
            tia_audc[0] = data & 15;
            channel = 0;
            break;
        
        case AUDC1:
            tia_audc[1] = data & 15;
            channel = 1;
            break;
        
        case AUDF0:
            tia_audf[0] = data & 31;
            channel = 0;
            break;
        
        case AUDF1:
            tia_audf[1] = data & 31;
            channel = 1;
            break;
        
        case AUDV0:
            tia_audv[0] = (data & 15) << 2;
            channel = 0;
            break;
        
        case AUDV1:
            tia_audv[1] = (data & 15) << 2;
            channel = 1;
            break;
        
        default:
            return;
    }
    
    if (tia_audc[channel] == 0) {
        frequency = 0;
        tia_volume[channel] = tia_audv[channel];
    }
    else {
        frequency = tia_audf[channel] + 1;
        if(tia_audc[channel] > 11) {
            frequency *= 3;
        }
    }
    
    if (frequency != tia_counterMax[channel]) {
        tia_counterMax[channel] = frequency;
        
        if (tia_counter[channel] == 0 || frequency == 0) {
            tia_counter[channel] = frequency;
        }
    }
}

void tia_Process(uint32_t length) {
    for(size_t index = 0; index < length; index++) {
        if (tia_counter[0] > 1) {
            tia_counter[0]--;
        }
        else if (tia_counter[0] == 1) {
            tia_counter[0] = tia_counterMax[0];
            tia_ProcessChannel(0);
        }
        
        if (tia_counter[1] > 1) {
            tia_counter[1]--;
        }
        else if (tia_counter[1] == 1) {
            tia_counter[1] = tia_counterMax[1];
            tia_ProcessChannel(1);
        }
        
        tia_buffer[tia_soundCntr++] = tia_volume[0] + tia_volume[1];
        
        if (tia_soundCntr >= tia_size) {
            tia_soundCntr = 0;
        }
    }
}
