// created on 10/30/2004 at 09:54
using System;

public class Mapper
{
	public Cartridge mapperCartridge;
	Nes nes;
	
	public uint [] current_prg_rom_page;
	public uint [] current_chr_rom_page;
			
	public bool timer_irq_enabled;
	public bool timer_reload_next;
	public uint timer_irq_count, timer_irq_reload;
	bool timer_zero_pulse;  //the single pulse timer

    public Mapper(Nes nes)
    {
        this.nes = nes;
        current_prg_rom_page = new uint[8];
        current_chr_rom_page = new uint[8];
        timer_irq_enabled = false;
    }

    public void SetUpMapperDefaults()
    {
        Switch32kPrgRom(0);
        Switch8kChrRom(0);
    }
	
	public byte ReadChrRom(ushort address)
	{
		byte returnvalue = 0xff;
		
		if (address < 0x400)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[0]][address];
		}
		else if (address < 0x800)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[1]][address - 0x400];
		}
		else if (address < 0xC00)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[2]][address - 0x800];
		}
		else if (address < 0x1000)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[3]][address - 0xC00];
		}
		else if (address < 0x1400)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[4]][address - 0x1000];
		}
		else if (address < 0x1800)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[5]][address - 0x1400];
		}
		else if (address < 0x1C00)
		{
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[6]][address - 0x1800];
		}
		else
		{			
			returnvalue = mapperCartridge.chr_rom[current_chr_rom_page[7]][address - 0x1C00];			
		}
		
		return returnvalue;
	}
	
	void Switch32kPrgRom(int start)
	{
		int i;
		switch (mapperCartridge.prg_rom_pages)
		{
			case (2): start = (start & 0x7); break;
			case (4): start = (start & 0xf); break;
			case (8): start = (start & 0x1f); break;
			case (16): start = (start & 0x3f); break;
			case (32): start = (start & 0x7f); break;
		}
		for (i = 0; i < 8; i++)
		{
			current_prg_rom_page[i] = (uint)(start + i);
		}
	}

	void Switch8kChrRom(int start)
	{
		int i;
		switch (mapperCartridge.chr_rom_pages)
		{
			case (2): start = (start & 0xf); break;
			case (4): start = (start & 0x1f); break;
			case (8): start = (start & 0x3f); break;
			case (16): start = (start & 0x7f); break;
			case (32): start = (start & 0xff); break;
		}
		for (i = 0; i < 8; i++)
		{
			current_chr_rom_page[i] = (uint)(start + i);
		}
	}
	
	public byte ReadPrgRom(ushort address)
	{
		byte returnvalue = 0xff;
		
		if (address < 0x9000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[0]][address - 0x8000];
		}
		else if (address < 0xA000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[1]][address - 0x9000];
		}
		else if (address < 0xB000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[2]][address - 0xA000];
		}
		else if (address < 0xC000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[3]][address - 0xB000];
		}
		else if (address < 0xD000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[4]][address - 0xC000];
		}
		else if (address < 0xE000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[5]][address - 0xD000];
		}
		else if (address < 0xF000)
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[6]][address - 0xE000];
		}
		else
		{
			returnvalue = mapperCartridge.prg_rom[current_prg_rom_page[7]][address - 0xF000];
		}
		
		return returnvalue;
	}
	
	public void TickTimer()
	{
		if (nes.myPPU.currentScanline < 240)
		{
			if ((timer_reload_next)&&(timer_irq_enabled))
			{
				//Console.WriteLine("Timer reloaded with: {0} in scanline: {1}", timer_irq_reload, myEngine.myPPU.currentScanline);
				timer_irq_count = timer_irq_reload;
				timer_reload_next = false;
			}
			else
			{
				if (timer_irq_enabled)
				{
					if (timer_irq_count == 0)
					{
						//Count down complete, fire our irq
						//Special case: if we're doing a single pulse because of a zero
						//being written to C000
						if (timer_irq_reload > 0)
						{
							//if (myEngine.my6502.interrupt_flag == 0)
							{
								nes.my6502.Push16(nes.my6502.pc_register);
								nes.my6502.PushStatus();
								nes.my6502.pc_register = nes.ReadMemory16(0xFFFE);
								nes.my6502.interrupt_flag = 1;
							}
							timer_irq_enabled = false;
						}
						else if (timer_zero_pulse)
						{
							nes.my6502.Push16(nes.my6502.pc_register);
							nes.my6502.PushStatus();
							nes.my6502.pc_register = nes.ReadMemory16(0xFFFE);
							timer_zero_pulse = false;
						}

						//Make sure that we also carry in the timer
						timer_reload_next = true;
					}
					else
					{
						if ((nes.myPPU.backgroundVisible) || ( nes.myPPU.spritesVisible))
							timer_irq_count = timer_irq_count - 1;
					}
				}
			}
		}
	}
}