//---------------------------------------------------------------------------
// NEOPOP : Emulator as in Dreamland
//
// Copyright (c) 2001-2002 by neopop_uk
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
//	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. See also the license.txt file for
//	additional informations.
//---------------------------------------------------------------------------

#include "neopop.h"
#include "mem.h"
#include "gfx.h"
#include "interrupt.h"
#include "Z80_interface.h"
#include "dma.h"

//=============================================================================

namespace MDFN_IEN_NGP
{

uint32 timer_hint;
static uint32 timer_clock[4];
static uint8 timer[4];	//Up-counters
static uint8 timer_threshold[4];

static uint8 TRUN;
static uint8 T01MOD, T23MOD;
static uint8 TRDC;
static uint8 TFFCR;
static uint8 HDMAStartVector[4];

static int32 ipending[24];
static int32 IntPrio[0xB]; // 0070-007a
static bool h_int, timer0, timer2;

// The way interrupt processing is set up is still written towards BIOS HLE emulation, which assumes
// that the interrupt handler will immediately call DI, clear the interrupt latch(so the interrupt won't happen again when interrupts are re-enabled),
// and then call the game's interrupt handler.

// We automatically clear the interrupt latch when the interrupt is accepted, and the interrupt latch is not checked every instruction,
// but only when: an EI/DI, POP SR, or RETI instruction occurs; after a write to an interrupt priority register occurs; and when
// a device sets the virual interrupt latch register, signaling it wants an interrupt.

// FIXME in the future if we ever add real bios support?
void interrupt(const uint8 index, const int level)
{
	//printf("INT: %d\n", index);
	push32(pc);
	push16(sr);

	//Up the IFF
	if(level >= 0)
	 setStatusIFF((level < 7) ? (level + 1) : 7);

        //Access the interrupt vector table to find the jump destination
        pc = loadL(0x6FB8 + index * 4);
}

void set_interrupt(uint8 index, bool set)
{
 assert(index < 24);

 ipending[index] = set;
 int_check_pending();
}

void int_check_pending(void)
{
 uint8 prio;
 uint8 curIFF = statusIFF();

 // Technically, the BIOS should clear the interrupt pending flag by writing with IxxC set to "0", but
 // we'll actually need to implement a BIOS to do that!

 prio = IntPrio[0x1] & 0x07;     // INT4
 if(ipending[5] && curIFF <= prio && prio && prio != 7)
 {
  ipending[5] = 0;
  interrupt(5, prio);
  return;
 }

 prio = (IntPrio[0x1] & 0x70) >> 4;	// INT5 (Z80)
 if(ipending[6] && curIFF <= prio && prio && prio != 7)
 {
  ipending[6] = 0;
  interrupt(6, prio);
  return;
 }

 prio = IntPrio[0x3] & 0x07;	// INTT0
 if(ipending[7] && curIFF <= prio && prio && prio != 7)
 {
  ipending[7] = 0;
  interrupt(7, prio);
  return;
 }

 prio = (IntPrio[0x3] & 0x70) >> 4;	// INTT1
 if(ipending[8] && curIFF <= prio && prio && prio != 7)
 {
  ipending[8] = 0;
  interrupt(8, prio);
  return;
 }

 prio = (IntPrio[0x4] & 0x07);	// INTT2
 if(ipending[9] && curIFF <= prio && prio && prio != 7)
 {
  ipending[9] = 0;
  interrupt(9, prio);
  return;
 }

 prio = ((IntPrio[0x4] & 0x70) >> 4); // INTT3
 if(ipending[10] && curIFF <= prio && prio && prio != 7)
 {
  ipending[10] = 0;
  interrupt(10, prio);
  return;
 }

 prio = (IntPrio[0x7] & 0x07); // INTRX0
 if(ipending[11] && curIFF <= prio && prio && prio != 7)
 {
  ipending[11] = 0;
  interrupt(11, prio);
  return;
 }

 prio = ((IntPrio[0x7] & 0x70) >> 4); // INTTX0
 if(ipending[12] && curIFF <= prio && prio && prio != 7)
 {
  ipending[12] = 0;
  interrupt(12, prio);
  return;
 }

}

MDFN_FASTCALL void int_write8(uint32 address, uint8 data)
{
 switch(address)
 {
  case 0x71: if(!(data & 0x08)) ipending[5] = 0;
             if(!(data & 0x80)) ipending[6] = 0;
             break;
  case 0x73: if(!(data & 0x08)) ipending[7] = 0; 
	     if(!(data & 0x80)) ipending[8] = 0;
	     break;
  case 0x74: if(!(data & 0x08)) ipending[9] = 0;
	     if(!(data & 0x80)) ipending[10] = 0;
	     break;
  case 0x77: if(!(data & 0x08)) ipending[11] = 0;
             if(!(data & 0x80)) ipending[12] = 0;
             break;
  case 0x7C: HDMAStartVector[0] = data; break;
  case 0x7D: HDMAStartVector[1] = data; break;
  case 0x7E: HDMAStartVector[2] = data; break;
  case 0x7F: HDMAStartVector[3] = data; break;
 }
 if(address >= 0x70 && address <= 0x7A)
 {
  IntPrio[address - 0x70] = data;
  int_check_pending();
 }
}

MDFN_FASTCALL uint8 int_read8(uint32 address)
{
 uint8 ret = 0;
 switch(address)
 {
  case 0x71: ret = ((ipending[5] ? 0x08 : 0x00) | (ipending[6] ? 0x80 : 0x00)); break;
  case 0x73: ret = ((ipending[7] ? 0x08 : 0x00) | (ipending[8] ? 0x80 : 0x00)); break;
  case 0x74: ret = ((ipending[9] ? 0x08 : 0x00) | (ipending[10] ? 0x80 : 0x00)); break;
  case 0x77: ret = ((ipending[11] ? 0x08 : 0x00) | (ipending[12] ? 0x80 : 0x00)); break;
 }

 return(ret);
}

void TestIntHDMA(int bios_num, int vec_num)
{
	bool WasDMA = 0;
               
                        if (HDMAStartVector[0] == vec_num)
                        {
                         WasDMA = 1;
                         DMA_update(0);
                        }
                        else
                        {
                         if (HDMAStartVector[1] == vec_num)
                         {
                          WasDMA = 1;
                          DMA_update(1);
                         }
                         else
                         {
                          if (HDMAStartVector[2] == vec_num)
                          {
                           WasDMA = 1;
                           DMA_update(2);
                          }
                          else
                          {
                           if (HDMAStartVector[3] == vec_num)
                           {
                            WasDMA = 1;
                            DMA_update(3);
                           }
                          }
                         }
                        }
	if(!WasDMA)
         set_interrupt(bios_num, true);
}

bool updateTimers(MDFN_Surface *surface, int cputicks)
{
	bool ret = 0;

	ngpc_soundTS += cputicks;
	//increment H-INT timer
	timer_hint += cputicks;

	//=======================

	//End of scanline / Start of Next one
	if (timer_hint >= TIMER_HINT_RATE)
	{
		uint8 data;

		// ============= END OF CURRENT SCANLINE =============

		h_int = NGPGfx->hint();	
		ret = NGPGfx->draw(surface, NGPFrameSkip);

		// ============= START OF NEXT SCANLINE =============

		timer_hint -= TIMER_HINT_RATE;	//Start of next scanline

		//Comms. Read interrupt
		if ((COMMStatus & 1) == 0 && system_comms_poll(&data))
		{
			storeB(0x50, data);
			TestIntHDMA(12, 0x19);
		}
	}

	//=======================

	//Tick the Clock Generator
	timer_clock[0] += cputicks;
	timer_clock[1] += cputicks;
	
	timer0 = false;	//Clear the timer0 tick, for timer1 chain mode.

	//=======================

	//Run Timer 0 (TRUN)?
	if ((TRUN & 0x01))
	{
		//T01MOD
		switch(T01MOD & 0x03)
		{
		case 0:	if (h_int)	//Horizontal interrupt trigger
				{
					timer[0]++;

					timer_clock[0] = 0;
					h_int = false;	// Stop h_int remaining active
				}
				break;

		case 1:	while (timer_clock[0] >= TIMER_T1_RATE)
				{
					timer[0]++;
					timer_clock[0] -= TIMER_T1_RATE;
				}
				break;

		case 2:	while(timer_clock[0] >= TIMER_T4_RATE)
				{
					timer[0]++;
					timer_clock[0] -= TIMER_T4_RATE;
				}
				break;

		case 3:	while (timer_clock[0] >= TIMER_T16_RATE)
				{
					timer[0]++;
					timer_clock[0] -= TIMER_T16_RATE;
				}
				break;
		}


		//Threshold check
		if (timer_threshold[0] && timer[0] >= timer_threshold[0])
		{
			timer[0] = 0;
			timer0 = true;

			TestIntHDMA(7, 0x10);
		}
	}

	//=======================

	//Run Timer 1 (TRUN)?
	if ((TRUN & 0x02))
	{
		//T01MOD
		switch((T01MOD & 0x0C) >> 2)
		{
		case 0:	if (timer0)	//Timer 0 chain mode.
				{
					timer[1] += timer0;
					timer_clock[1] = 0;
				}
				break;

		case 1:	while (timer_clock[1] >= TIMER_T1_RATE)
				{
					timer[1]++;
					timer_clock[1] -= TIMER_T1_RATE;
				}
				break;

		case 2:	while (timer_clock[1] >= TIMER_T16_RATE)
				{
					timer[1]++;
					timer_clock[1] -= TIMER_T16_RATE;
				}
				break;

		case 3:	while (timer_clock[1] >= TIMER_T256_RATE)
				{
					timer[1]++;
					timer_clock[1] -= TIMER_T256_RATE;
				}
				break;
		}

		//Threshold check
		if (timer_threshold[1] && timer[1] >= timer_threshold[1])
		{
			timer[1] = 0;

			TestIntHDMA(8, 0x11);
		}
	}

	//=======================

	//Tick the Clock Generator
	timer_clock[2] += cputicks;
	timer_clock[3] += cputicks;

	timer2 = false;	//Clear the timer2 tick, for timer3 chain mode.

	//=======================
	
	//Run Timer 2 (TRUN)?
	if ((TRUN & 0x04))
	{
		//T23MOD
		switch(T23MOD & 0x03)
		{
		case 0:	// -
				break;

		case 1:	while (timer_clock[2] >= TIMER_T1_RATE / 2) // Kludge :(
				{
					timer[2]++;
					timer_clock[2] -= TIMER_T1_RATE / 2;
				}
				break;

		case 2:	while (timer_clock[2] >= TIMER_T4_RATE)
				{
					timer[2]++;
					timer_clock[2] -= TIMER_T4_RATE;
				}
				break;

		case 3:	while (timer_clock[2] >= TIMER_T16_RATE)
				{
					timer[2]++;
					timer_clock[2] -= TIMER_T16_RATE;
				}
				break;
		}

		//Threshold check
		if (timer_threshold[2] && timer[2] >= timer_threshold[2])
		{
			timer[2] = 0;
			timer2 = true;

			TestIntHDMA(9, 0x12);
		}
	}

	//=======================

	//Run Timer 3 (TRUN)?
	if ((TRUN & 0x08))
	{
		//T23MOD
		switch((T23MOD & 0x0C) >> 2)
		{
		case 0:	if(timer2)	//Timer 2 chain mode.
				{
					timer[3] += timer2;
					timer_clock[3] = 0;
				}
				break;

		case 1:	while (timer_clock[3] >= TIMER_T1_RATE)
				{
					timer[3]++;
					timer_clock[3] -= TIMER_T1_RATE;
				}
				break;

		case 2:	while (timer_clock[3] >= TIMER_T16_RATE)
				{
					timer[3]++;
					timer_clock[3] -= TIMER_T16_RATE;
				}
				break;

		case 3:	while (timer_clock[3] >= TIMER_T256_RATE)
				{
					timer[3]++;
					timer_clock[3] -= TIMER_T256_RATE;
				}
				break;
		}

		//Threshold check
		if (timer_threshold[3] && timer[3] >= timer_threshold[3])
		{
			timer[3] = 0;

			Z80_irq();
			TestIntHDMA(10, 0x13);
		}
	}
	return(ret);
}

void reset_timers(void)
{
	timer_hint = 0;

	memset(timer, 0, sizeof(timer));
	memset(timer_clock, 0, sizeof(timer_clock));
	memset(timer_threshold, 0, sizeof(timer_threshold));

	timer0 = false;
	timer2 = false;
}

void reset_int(void)
{
 TRUN = 0;
 T01MOD = 0;
 T23MOD = 0;
 TRDC = 0;
 TFFCR = 0;

 memset(HDMAStartVector, 0, sizeof(HDMAStartVector));
 memset(ipending, 0, sizeof(ipending));
 memset(IntPrio, 0, sizeof(IntPrio));

 h_int = false;
}

MDFN_FASTCALL void timer_write8(uint32 address, uint8 data)
{
	switch(address)
	{
	 case 0x20: TRUN = data;
                    if ((TRUN & 0x01) == 0)         timer[0] = 0;
    	            if ((TRUN & 0x02) == 0)         timer[1] = 0;
        	    if ((TRUN & 0x04) == 0)         timer[2] = 0;
                    if ((TRUN & 0x08) == 0)         timer[3] = 0;
		    break;
	 case 0x22: timer_threshold[0] = data; break;
	 case 0x23: timer_threshold[1] = data; break;
	 case 0x24: T01MOD = data; break;
	 case 0x25: TFFCR = data & 0x33; break;
	 case 0x26: timer_threshold[2] = data; break;
	 case 0x27: timer_threshold[3] = data; break;
	 case 0x28: T23MOD = data; break;
	 case 0x29: TRDC = data & 0x3; break;
	}
}

MDFN_FASTCALL uint8 timer_read8(uint32 address)
{
	uint8 ret = 0;

	switch(address)
	{
	 //default: printf("Baaaad: %08x\n", address); break;
	 // Cool boarders is stupid and tries to read from a write-only register >_<
	 // Returning 4 makes the game run ok, so 4 it is!
	 default: ret = 0x4; break;
	 case 0x20: ret = TRUN; break;
	 case 0x29: ret = TRDC; break;
	}

	//printf("UNK B R: %08x\n", address);
	return(ret);
}

int int_timer_StateAction(StateMem *sm, int load, int data_only)
{
 SFORMAT StateRegs[] =
 {
  SFVAR(timer_hint),
  SFVAR(timer_clock),
  SFVAR(timer),
  SFVAR(timer_threshold),
  SFVAR(TRUN),
  SFVAR(T01MOD), SFVAR(T23MOD),
  SFVAR(TRDC),
  SFVAR(TFFCR),
  SFVAR(HDMAStartVector),
  SFVAR(ipending),
  SFVAR(IntPrio),
  SFVAR(h_int),
  SFVAR(timer0),
  SFVAR(timer2),
  SFEND
 };
 if(!MDFNSS_StateAction(sm, load, data_only, StateRegs, "INTT"))
  return(0);
 return(1);
}

}
