//
// Test program for GBA devkitadv
//

// 型情報
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned long u32;
typedef signed char s8;
typedef signed short s16;
typedef signed long s32;

// 制御レジスタ情報
#define VRAMTOP (u16*)0x6000000  // VRAM frame buffer top address
#define MAPTOP0 (u16*)0x6004000  // VRAM frame buffer top address
#define MAPTOP1 (u16*)0x6004800  // VRAM frame buffer top address
#define MAPTOP2 (u16*)0x6005000  // VRAM frame buffer top address
#define MAPTOP3 (u16*)0x6005800  // VRAM frame buffer top address
#define PALETTE (u16*)0x5000000  // VRAM frame buffer top address
#define register(p) *((u16*) p)  // I/O register handling macro

#define LCD_CTRL  0x04000000   // LCD control
#define BG0CNT  0x04000008   // BG0 control
#define BG1CNT  0x0400000a   // BG1 control
#define BG2CNT  0x0400000c   // BG2 control
#define BG3CNT  0x0400000e   // BG3 control
#define BG0_X_SCROLLING 0x04000010
#define BG0_Y_SCROLLING 0x04000012
#define BG1_X_SCROLLING 0x04000014
#define BG1_Y_SCROLLING 0x04000016
#define BG2_X_SCROLLING 0x04000018
#define BG2_Y_SCROLLING 0x0400001a
#define BG3_X_SCROLLING 0x0400001c
#define BG3_Y_SCROLLING 0x0400001e

#define KEY_INPUT     0x04000130
#define KEY_INTERRUPT 0x04000132

#define INT_IE 0x04000200
#define INT_IF 0x04000202
#define INT_IME 0x04000208

#define LCD_BG0EN 0x0100     // Enable BG0
#define LCD_BG1EN 0x0200     // Enable BG1
#define LCD_BG2EN 0x0400     // Enable BG2
#define LCD_BG3EN 0x0800     // Enable BG3
#define RGB(r, g, b) (((b) << 10) + ((g) << 5) + (r))

#define KEY_A      0x0001
#define KEY_B      0x0002
#define KEY_SELECT 0x0004
#define KEY_START  0x0008
#define KEY_RIGHT  0x0010
#define KEY_LEFT   0x0020
#define KEY_UP     0x0040
#define KEY_DOWN   0x0080
#define KEY_R      0x0100
#define KEY_L      0x0200
#define KEY_INTEN  0x4000
#define KEY_INTAND 0x8000

#define INT_VBLANK 0x0001
#define INT_HBLANK 0x0002
#define INT_VCOUNT 0x0004
#define INT_TIMER0 0x0008
#define INT_TIMER1 0x0010
#define INT_TIMER2 0x0020
#define INT_TIMER3 0x0040
#define INT_COMM   0x0080
#define INT_DMA0   0x0100
#define INT_DMA1   0x0200
#define INT_DMA2   0x0400
#define INT_DMA3   0x0800
#define INT_KEY    0x1000
#define INT_GAMEP  0x2000

// マルチブート指定
int __gba_multiboot = 0;

volatile u16 x_scrolling = 0;

void IRQ_Handler()
{
  u16 Int_Flag;

  register(INT_IME) =  0;

  Int_Flag = register(INT_IF);

  if((Int_Flag & INT_KEY) != 0){
    if((register(KEY_INPUT) & KEY_A) == 0){
      x_scrolling = 0;
    }
    else if((register(KEY_INPUT) & KEY_B) == 0){
      x_scrolling = 8;
    }
  }

  register(INT_IF) = Int_Flag;
  register(INT_IME) =  1;
}

void WaitForVsync(void)
{
  while(*(volatile u16*)0x4000006 >= 160){};
  while(*(volatile u16*)0x4000006 < 160){};
}

// メインプログラム
int main(void)
{
  s32 i;

  u8 x, y;
  u16* vram = VRAMTOP;
  u16* map0 = MAPTOP0;
  u16* map1 = MAPTOP1;
  u16* map2 = MAPTOP2;
  u16* map3 = MAPTOP3;
  u16* palette = PALETTE;

  register(INT_IME) =  0;

  *(u32*)0x03007FFC = (u32)IRQ_Handler;

  register(INT_IE) |= INT_KEY;
  register(KEY_INTERRUPT) = KEY_INTEN | KEY_A | KEY_B;

  register(INT_IME) =  1;

  // 画面モードの初期化
  register(LCD_CTRL) = (0 << 13) | (1 << 6) | LCD_BG0EN | 0x0000; // Mode0, BG0 表示
  register(BG0CNT) = (8 << 8) | (0 << 7) | 0x0000;

  // 赤青緑のカラーパターン描画
  palette[0] = RGB(31, 31, 31);
  palette[1] = RGB(31, 0, 0);
  palette[2] = RGB(0, 31, 0);
  palette[3] = RGB(0, 0, 31);

  for(i = 0; i < 16; i++){
    vram[i] = 0x0000;
  }

  for(i = 16; i < 32; i++){
    vram[i] = 0x1111;
  }

  for(i = 32; i < 48; i++){
    vram[i] = 0x2222;
  }

  for(i = 48; i < 64; i++){
    vram[i] = 0x3333;
  }

  map0[0] = 0x0000;
  map0[1] = 0x0001;
  map0[2] = 0x0002;
  map0[3] = 0x0003;

  // 無限ループ
  while(1){
    register(BG0_X_SCROLLING) = x_scrolling;
    // Ｖブランクまで待機
    WaitForVsync();
  }
}