import javax.microedition.lcdui.*;
import java.util.Random;
import java.io.InputStream;
import java.io.DataInputStream;
import java.io.IOException;

public class Emulator extends Canvas {

 public boolean gameLoaded = false;
 int scw = 64, sch = 32;
 byte[][] screen = new byte[scw][sch];
 byte[] key = new byte[16];
 byte[] mem = new byte[4096];
 byte[] V = new byte[16];
 short I;
 byte delay_timer;
 byte sound_timer;
 short[] stack = new short[16];
 short opcode;
 short PC;
 byte SP;
 int w;
 int h;
 long old_time = System.currentTimeMillis();
 int sleep = 40;

 /**
 * constructor
 */
 public Emulator() {
  setFullScreenMode(true);
  w = getWidth();
  h = getHeight();

  PC = 0x200;
  SP = 0;
  I = 0x200;

  delay_timer = 0;
  sound_timer = 0;

  for(int a = 0; a<sch; a++){
   for(int b = 0; b<scw; b++){
    screen[b][a] = 0;
   }
  }
  for(int i = 0; i<16; i++){
   key[i] = 0;
  }
  for(int i = 0; i<4096; i++){
   mem[i] = 0;
  }
  for(int i = 0; i<16; i++){
   V[i] = 0;
  }
  for(int i = 0; i<16; i++){
   stack[i] = 0;
  }
  byte[] font = {
   0x71, 0x11, 0x71, 0x11, 0x71, //0
   -0x5F, -0x1F, -0x1F, -0x1F, -0x5F, //1
   0x71, -0x6F, 0x71, 0x01, 0x71, //2
   0x71, -0x6F, 0x71, -0x6F, 0x71, //3
   0x11, 0x11, 0x71, -0x6F, -0x6F, //4
   0x71, 0x01, 0x71, -0x6F, 0x71, //5
   0x71, 0x01, 0x71, -0x6F, 0x71, //6
   0x71, -0x6F, -0x5F, -0x3F, -0x3F, //7
   0x71, 0x11, 0x71, 0x11, 0x71, //8
   0x71, 0x11, 0x71, -0x6F, 0x71, //9
   0x71, 0x11, 0x71, 0x11, 0x11, //A
   0x61, 0x11, 0x61, 0x11, 0x61, //B
   0x71, 0x01, 0x01, 0x01, 0x71, //C
   0x61, 0x11, 0x11, 0x11, 0x61, //D
   0x71, 0x01, 0x71, 0x01, 0x71, //E
   0x71, 0x01, 0x71, 0x01, 0x01 //F
  };
  for(int i = 0; i<0x050; i++){
   mem[i] = font[i];
  }
 }

 public void loadGame() {
  try{
   InputStream is = getClass().getResourceAsStream("/game.c8");
   DataInputStream dis = new DataInputStream(is);
   dis.readFully(mem, 0x200, dis.available());
   dis.close();
   is.close();
   gameLoaded = true;
  }catch(Throwable t){
    Midlet.getInstance().displayError(t.toString().concat(" at Emulator"));
  }
 }

 public void drawSprite(int X, int Y, int N) {
 try {
  V[0xF] = 0;
  if(N == 0) N = 16;
  for(int yline = 0; yline<N; yline++) {
   byte data = mem[I+yline];
   for(int xpix = 0; xpix<8; xpix++){
    if((data&(0x80 >> xpix))!=0){
     if((V[X] + xpix)<64&&(V[Y] + yline)<32&&(V[X] + xpix)>=0&&(V[Y] + yline)>=0) {
      if(screen[V[X] + xpix][V[Y] + yline] == 1) V[0xF] = 1;
      screen[V[X] + xpix][V[Y] + yline]^=1;
     }
    }
   }
  }
 } catch (Throwable t) {
   Midlet.getInstance().displayError(t.toString().concat(" at Emulator.drawSprite()"));
 }
 }

 public void executeNextOpcode() {
 try {
  opcode = (short)((mem[PC]<<8) | mem[PC+1]);
  PC+=2;
  int x = (int)((opcode&0x0F00)>>8);
  int y = (int)((opcode&0x00F0)>>4);
  byte kk = (byte)(opcode&0x00FF);

  switch((opcode&0xF000)>>12){
   case 0x0:
    switch(opcode&0x00FF) {
     case 0xE0:
      for(int a = 0; a<sch; a++){
       for(int b = 0; b<scw; b++){
        screen[b][a] = 0;
       }
      }
      break;
     case 0xEE:
      PC = stack[--SP];
      break;
    }
    break;
   case 0x1:
    PC = (short)(opcode&0x0FFF);
    break;
   case 0x2:
    stack[SP++] = PC;
    PC = (short)(opcode&0x0FFF);
    break;
   case 0x3:
    if(V[x] == kk) PC+=2;
    break;
   case 0x4:
    if(V[x]!=kk) PC+=2;
    break;
   case 0x5:
    switch(opcode&0x000F){
     case 0x0:
      if(V[x] == V[y]) PC+=2;
      break;
    }
    break;
   case 0x6:
    V[x] = kk;
    break;
   case 0x7:
    V[x]+=kk;
    break;
   case 0x8:
    switch(opcode&0x000F){
     case 0x0:
      V[x] = V[y];
      break;
     case 0x1:
      V[x]=(byte)(V[x]|V[y]);
      break;
     case 0x2:
      V[x] = (byte)(V[x]&V[y]);
      break;
     case 0x3:
      V[x] = (byte)(V[x]^V[y]);
      break;
     case 0x4:
      if((V[x] + V[y])>0xF) V[0xF] = 1;
      else V[0xF] = 0;
      break;
     case 0x5:
      if(V[x]>=V[y]) V[0xF] = 1;
      else V[0xF] = 0;
      V[x]-=V[y];
      break;
     case 0x6:
      if((V[x]&0x000F) == 1) V[0xF] = 1;
      else V[0xF] = 0;
      V[x] = (byte)(V[x] >> 1);
      break;
     case 0x7:
      if(V[y]>=V[x]) V[0xF] = 1;
      else V[0xF] = 0;
      V[x] = (byte)(V[y] - V[x]);
      break;
     case 0xE:
      if((V[x]&0x000F)==1) V[0xF] = 1;
      else V[0xF] = 0;
      V[x] = (byte)(V[x] << 1);
      break;
    }
    break;
   case 0x9:
    switch(opcode&0x000F){
     case 0x0:
      if(V[x]!=V[y]) PC+=2;
      break;
    }
    break;
   case 0xA:
    I = (short)(opcode&0x0FFF);
    break;
   case 0xB:
    PC = (short)(opcode&0x0FFF + V[0x0]);
    break;
   case 0xC:
    Random rnd = new Random();
    V[x] = (byte)(((rnd.nextInt()>>>1)%255)&kk);
    break;
   case 0xD:
    byte varx = (byte)((opcode&0x0F00)>>8);
    byte vary = (byte)((opcode&0x00F0)>>4);
    byte n = (byte)(opcode&0x000F);
    drawSprite(x, y, (int)n);
    break;
   case 0xE:
    switch(opcode&0x00FF){
     case 0x9E:
      if(key[(int)(V[x])] == 1) PC+=2;
      break;
     case 0xA1:
      if(key[(int)(V[x])]==0) PC+=2;
      break;
    }
    break;
   case 0xF:
    switch(opcode&0x00FF){
     case 0x07:
      V[x] = delay_timer;
      break;
     case 0x0A:
      for(int i = 0; i<16; i++){
       if(key[i] == 1){
         V[x] = (byte)i;
         break;
       }
      }
      break;
     case 0x15:
      delay_timer = V[x];
      break;
     case 0x18:
      sound_timer = V[x];
      break;
     case 0x1E:
      I = (short)(I + V[x]);
      break;
     case 0x29:
      I = (short)((V[x]-1)*5+1);
      break;
     case 0x33:
      byte a = (byte)(V[x]/100);
      byte b = (byte)((V[x] - 100*a)/10);
      byte c = (byte)(V[x] - 100*a - 10*b);
      mem[I] = (byte)(a&0xF);
      mem[I+1] = (byte)(b&0xF);
      mem[I+2] = (byte)(c&0xF);
      break;
     case 0x55:
      for(int i = 0; i<16; i++){
       mem[I+i] = V[i];
      }
      break;
     case 0x65:
      for(int i = 0; i<16; i++){
       V[i] = mem[I+i];
      }
      break;
    }
    break;
  }
 } catch (Throwable t) {
     Midlet.getInstance().displayError(t.toString().concat(" at Emulator.executeNextOpcode()"));
 }
 }

 public void decreaseTimers(){
  if (System.currentTimeMillis() - old_time >= 1000 / 60) {
   if(delay_timer > 0) {
    delay_timer--;
   }
   if(sound_timer > 0) {
    sound_timer--;
   }
   old_time = System.currentTimeMillis();
  }
 }

 /**
 * paint
 */
 public void paint(Graphics g) {
  if (gameLoaded && isShown()) {
   try {
    g.setColor(0xFFFFFF);
    g.fillRect(0, 0, w, h);
    g.setColor(0x000000);
    g.drawString("0x".concat(Integer.toHexString(opcode)), 5, 5, 0);

    Image i = Image.createImage(scw, sch);
    Graphics G = i.getGraphics();
    for(int a = 0; a<32; a++){
     for(int b = 0; b<64;b++){
      if(screen[b][a]==1){
       G.setColor(0xFFFFFF);
       G.fillRect(b, a, 1, 1);
      }
      else {
       G.setColor(0x000000);
       G.fillRect(b, a, 1, 1);
      }
     }
    }
    g.drawImage(i, w / 2 - scw / 2, h / 2 - sch / 2, 0);

    executeNextOpcode();
    decreaseTimers();
    repaint();

    Thread.sleep(sleep);
   } catch (Throwable t) {
     Midlet.getInstance().displayError(t.toString().concat(" at Emulator.paint()"));
   }
  }
 }

 /**
 * Called when a key is pressed.
 */
 protected void keyPressed(int keyCode) {
  int ga = getGameAction(keyCode);
  switch(keyCode){
   case KEY_NUM1:
    key[0x1] = 1;
    break;
   case KEY_NUM2:
    key[0x2] = 1;
    break;
   case KEY_NUM3:
    key[0x3] = 1;
    break;
   case KEY_NUM4:
    key[0x4] = 1;
    break;
   case KEY_NUM5:
    key[0x5] = 1;
    break;
   case KEY_NUM6:
    key[0x6] = 1;
    break;
   case KEY_NUM7:
    key[0x7] = 1;
    break;
   case KEY_NUM8:
    key[0x8] = 1;
    break;
   case KEY_NUM9:
    key[0x9] = 1;
    break;
   case KEY_NUM0:
    key[0x0] = 1;
    break;
   case KEY_STAR:
    key[0xF] = 1;
    break;
   case -36:
    sleep += 10;
    break;
   case -37:
    if (sleep >= 10) sleep -= 10;
    break;
  }
  if(ga==UP&&keyCode!=KEY_NUM2){
   key[0xA] = 1;
  }
  if(ga==DOWN&&keyCode!=KEY_NUM8){
   key[0xB] = 1;
  }
  if(ga==LEFT&&keyCode!=KEY_NUM4){
   key[0xC] = 1;
  }
  if(ga==RIGHT&&keyCode!=KEY_NUM6){
   key[0xD] = 1;
  }
  if(ga == FIRE&&keyCode!=KEY_NUM5){
   key[0xE] = 1;
  }
 }
}