/* gameplaySP
 *
 * Copyright (C) 2006 Exophase <exophase@gmail.com>
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "common.h"
#include <ctype.h>

timer_type timer[4];

const u32 global_cycles_per_instruction = 1;

u32 cpu_ticks = 0;

u32 execute_cycles = 960;
s32 video_count = 960;

u32 last_frame = 0;
u32 flush_ram_count = 0;
u32 gbc_update_count = 0;
u32 oam_update_count = 0;

char main_path[512];
char save_path[512];

void trigger_ext_event(void);

static unsigned update_timers(irq_type *irq_raised, unsigned completed_cycles)
{
   unsigned i, ret = 0;
   for (i = 0; i < 4; i++)
   {
      if(timer[i].status == TIMER_INACTIVE)
         continue;

      if(timer[i].status != TIMER_CASCADE)
      {
         timer[i].count -= completed_cycles;
         /* io_registers accessors range: REG_TM0D, REG_TM1D, REG_TM2D, REG_TM3D */
         write_ioreg(REG_TM0D + (i * 2), -(timer[i].count > timer[i].prescale));
      }

      if(timer[i].count > 0)
         continue;

      /* irq_raised value range: IRQ_TIMER0, IRQ_TIMER1, IRQ_TIMER2, IRQ_TIMER3 */
      if(timer[i].irq)
         *irq_raised |= (8 << i);

      if((i != 3) && (timer[i + 1].status == TIMER_CASCADE))
      {
         timer[i + 1].count--;
         write_ioreg(REG_TM0D + (i + 1) * 2, -timer[i+1].count);
      }

      if(i < 2)
      {
         if(timer[i].direct_sound_channels & 0x01)
            ret += sound_timer(timer[i].frequency_step, 0);

         if(timer[i].direct_sound_channels & 0x02)
            ret += sound_timer(timer[i].frequency_step, 1);
      }

      timer[i].count += (timer[i].reload << timer[i].prescale);
   }
   return ret;
}

void init_main(void)
{
  u32 i;

  for(i = 0; i < 4; i++)
  {
    dma[i].start_type = DMA_INACTIVE;
    dma[i].direct_sound_channel = DMA_NO_DIRECT_SOUND;
    timer[i].status = TIMER_INACTIVE;
    timer[i].reload = 0x10000;
  }

  timer[0].direct_sound_channels = TIMER_DS_CHANNEL_BOTH;
  timer[1].direct_sound_channels = TIMER_DS_CHANNEL_NONE;

  cpu_ticks = 0;

  execute_cycles = 960;
  video_count = 960;

#ifdef HAVE_DYNAREC
  init_emitter();
  init_caches();
#endif
}

u32 update_gba(int remaining_cycles)
{
  irq_type irq_raised = IRQ_NONE;
  int dma_cycles;
  remaining_cycles = MAX(remaining_cycles, -64);

  do
  {
    unsigned i;
    // Number of cycles we ask to run - cycles that we did not execute
    // (remaining_cycles can be negative and should be close to zero)
    unsigned completed_cycles = execute_cycles - remaining_cycles;
    cpu_ticks += completed_cycles;

    remaining_cycles = 0;
    reg[CHANGED_PC_STATUS] = 0;
    reg[COMPLETED_FRAME] = 0;

    if(gbc_sound_update)
    {
      gbc_update_count++;
      update_gbc_sound(cpu_ticks);
      gbc_sound_update = 0;
    }

    // Timers can trigger DMA (usually sound) and consume cycles
    dma_cycles = update_timers(&irq_raised, completed_cycles);

    video_count -= completed_cycles;

    if(video_count <= 0)
    {
      u32 vcount = read_ioreg(REG_VCOUNT);
      u32 dispstat = read_ioreg(REG_DISPSTAT);

      if((dispstat & 0x02) == 0)
      {
        // Transition from hrefresh to hblank
        video_count += (272);
        dispstat |= 0x02;

        if((dispstat & 0x01) == 0)
        {
          u32 i;
          if(reg[OAM_UPDATED])
            oam_update_count++;

          update_scanline();

          // If in visible area also fire HDMA
          for(i = 0; i < 4; i++)
          {
            if(dma[i].start_type == DMA_START_HBLANK)
              dma_transfer(i, &dma_cycles);
          }
        }

        if(dispstat & 0x10)
          irq_raised |= IRQ_HBLANK;
      }
      else
      {
        // Transition from hblank to next line
        video_count += 960;
        dispstat &= ~0x02;

        vcount++;

        if(vcount == 160)
        {
          // Transition from vrefresh to vblank
          u32 i;

          dispstat |= 0x01;
          if(dispstat & 0x8)
          {
            irq_raised |= IRQ_VBLANK;
          }

          video_reload_counters();

          for(i = 0; i < 4; i++)
          {
            if(dma[i].start_type == DMA_START_VBLANK)
              dma_transfer(i, &dma_cycles);
          }
        }
        else

        if(vcount == 228)
        {
          // Transition from vblank to next screen
          dispstat &= ~0x01;

/*        printf("frame update (%x), %d instructions total, %d RAM flushes\n",
           reg[REG_PC], instruction_count - last_frame, flush_ram_count);
          last_frame = instruction_count;
*/
/*          printf("%d gbc audio updates\n", gbc_update_count);
          printf("%d oam updates\n", oam_update_count); */
          gbc_update_count = 0;
          oam_update_count = 0;
          flush_ram_count = 0;

          update_gbc_sound(cpu_ticks);
          gbc_sound_update = 0;

          /* If there's no cheat hook, run on vblank! */
          if (cheat_master_hook == ~0U)
             process_cheats();

          vcount = 0;
          // We completed a frame, tell the dynarec to exit to the main thread
          reg[COMPLETED_FRAME] = 1;
        }

        if(vcount == (dispstat >> 8))
        {
          // vcount trigger
          dispstat |= 0x04;
          if(dispstat & 0x20)
          {
            irq_raised |= IRQ_VCOUNT;
          }
        }
        else
          dispstat &= ~0x04;

        write_ioreg(REG_VCOUNT, vcount);
      }
      write_ioreg(REG_DISPSTAT, dispstat);
    }

    if(irq_raised)
      raise_interrupt(irq_raised);

    execute_cycles = MAX(video_count, 0);

    for (i = 0; i < 4; i++)
    {
       if(timer[i].status != TIMER_PRESCALE)
          continue;

       if(timer[i].count < execute_cycles)
          execute_cycles = timer[i].count;
    }
  } while(reg[CPU_HALT_STATE] != CPU_ACTIVE && !reg[COMPLETED_FRAME]);

  // We voluntarily limit this. It is not accurate but it would be much harder.
  dma_cycles = MIN(64, dma_cycles);
  dma_cycles = MIN(execute_cycles, dma_cycles);

  return execute_cycles - dma_cycles;
}

void reset_gba(void)
{
  init_memory();
  init_main();
  init_cpu();
  reset_sound();
}

#ifdef TRACE_REGISTERS
void print_regs(void)
{
  printf("R0=%08x R1=%08x R2=%08x R3=%08x "
         "R4=%08x R5=%08x R6=%08x R7=%08x "
         "R8=%08x R9=%08x R10=%08x R11=%08x "
         "R12=%08x R13=%08x R14=%08x\n",
         reg[0], reg[1], reg[2], reg[3],
         reg[4], reg[5], reg[6], reg[7],
         reg[8], reg[9], reg[10], reg[11],
         reg[12], reg[13], reg[14]);
}
#endif

bool main_read_savestate(const u8 *src)
{
  int i;
  const u8 *p1 = bson_find_key(src, "emu");
  const u8 *p2 = bson_find_key(src, "timers");
  if (!p1 || !p2)
    return false;

  if (!(bson_read_int32(p1, "cpu-ticks", &cpu_ticks) &&
         bson_read_int32(p1, "exec-cycles", &execute_cycles) &&
         bson_read_int32(p1, "video-count", (u32*)&video_count)))
    return false;

  for (i = 0; i < 4; i++)
  {
    char tname[2] = {'0' + i, 0};
    const u8 *p = bson_find_key(p2, tname);

    if (!(
      bson_read_int32(p, "count", (u32*)&timer[i].count) &&
      bson_read_int32(p, "reload", &timer[i].reload) &&
      bson_read_int32(p, "prescale", &timer[i].prescale) &&
      bson_read_int32(p, "freq-step", &timer[i].frequency_step) &&
      bson_read_int32(p, "dsc", &timer[i].direct_sound_channels) &&
      bson_read_int32(p, "irq", &timer[i].irq) &&
      bson_read_int32(p, "status", &timer[i].status)))
      return false;
  }  

  return true;
}

unsigned main_write_savestate(u8* dst)
{
  int i;
  u8 *wbptr, *wbptr2, *startp = dst;
  bson_start_document(dst, "emu", wbptr);
  bson_write_int32(dst, "cpu-ticks", cpu_ticks);
  bson_write_int32(dst, "exec-cycles", execute_cycles);
  bson_write_int32(dst, "video-count", video_count);
  bson_finish_document(dst, wbptr);

  bson_start_document(dst, "timers", wbptr);
  for (i = 0; i < 4; i++)
  {
    char tname[2] = {'0' + i, 0};
    bson_start_document(dst, tname, wbptr2);
    bson_write_int32(dst, "count", timer[i].count);
    bson_write_int32(dst, "reload", timer[i].reload);
    bson_write_int32(dst, "prescale", timer[i].prescale);
    bson_write_int32(dst, "freq-step", timer[i].frequency_step);
    bson_write_int32(dst, "dsc", timer[i].direct_sound_channels);
    bson_write_int32(dst, "irq", timer[i].irq);
    bson_write_int32(dst, "status", timer[i].status);
    bson_finish_document(dst, wbptr2);
  }
  bson_finish_document(dst, wbptr);

  return (unsigned int)(dst - startp);
}