/*
   interrupts_demo1 ARM9 Code 
   Chris Double (chris.double@double.co.nz)
   http://www.double.co.nz/nintendo_ds
*/

#include <nds.h>
#include "nds/arm9/console.h"
#include <stdio.h>
#include <stdlib.h>

static int old_x = 0;
static int old_y = 0;
static int shape_x = 0;
static int shape_y = 0;
static int shape_width = 10;
static int shape_height = 10;
static int interrupt_count = 0;
static int swi_return_count = 0;

void draw_shape(int x, int y, uint16* buffer, uint16 color)
{
  buffer += y * SCREEN_WIDTH + x;
  for(int i = 0; i < shape_height; ++i) {
    uint16* line = buffer + (SCREEN_WIDTH * i);
    for(int j = 0; j < shape_width; ++j) {
      *line++ = color;
    }
  }
}

void on_irq_vblank() 
{	
  old_x = shape_x;
  old_y = shape_y;
  shape_x++;
  if(shape_x + shape_width >= SCREEN_WIDTH) {
    shape_x = 0;
    shape_y += shape_height;
    if(shape_y + shape_height >= SCREEN_HEIGHT) {
      shape_y = 0;
    }
  }      

  draw_shape(old_x, old_y, VRAM_A, RGB15(0, 0, 0));
  draw_shape(shape_x, shape_y, VRAM_A, RGB15(31, 0, 0));
  printf("\x1b[2J");
  printf("Interrupt Count: %d\n", interrupt_count);
  printf("SWI Count      : %d\n", swi_return_count);
}

void on_irq_keys() 
{
  // Key interrupt occurred.
  interrupt_count++;
}

void on_irq() 
{
  if(REG_IF & IRQ_VBLANK) {
    on_irq_vblank();
    VBLANK_INTR_WAIT_FLAGS |= IRQ_VBLANK;  
    REG_IF |= IRQ_VBLANK;
  }  
  if(REG_IF & IRQ_KEYS) {
    on_irq_keys();
    VBLANK_INTR_WAIT_FLAGS |= IRQ_KEYS;  
    REG_IF |= IRQ_KEYS;
  }
}

void swiWaitForKeys() 
{
  asm("mov r0, #1");
  asm("mov r1, #4096");
  asm("swi #262144");
}

int main(void)
{
  powerON(POWER_ALL);
  videoSetMode(MODE_FB0);
  vramSetBankA(VRAM_A_LCD);

  // Set up second screen details
  videoSetModeSub(MODE_0_2D | DISPLAY_BG0_ACTIVE);
  vramSetBankC(VRAM_C_SUB_BG);
  SUB_BG0_CR = BG_MAP_BASE(31);
  BG_PALETTE_SUB[255] = RGB15(31,31,31);
  consoleInitDefault((u16*)SCREEN_BASE_BLOCK_SUB(31), (u16*)CHAR_BASE_BLOCK_SUB(0), 16);

  // Set up the interrupt handler
  REG_IME = 0;
  IRQ_HANDLER = on_irq;
  REG_IE = IRQ_VBLANK | IRQ_KEYS;
  REG_IF = ~0;
  DISP_SR = DISP_VBLANK_IRQ;
  REG_IME = 1;

  // The interrupt will fire when both the A and B key are
  // pressed. Bit 15 being set is what makes the requirement that both
  // keys must be pressed.
  REG_KEYCNT = KEY_A | KEY_B | (1<<14) | (1<<15);

  while(1) {
    swiWaitForKeys();
    ++swi_return_count;
  }

  return 0;
}