//////////////////////////////////////////////////////////////////////
// sram_demo1 ARM9 Code - Based on an example shipped with NDSLIB.
// Chris Double (chris.double@double.co.nz)
//////////////////////////////////////////////////////////////////////

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

static char card_id[5] = { 0,0,0,0,0 };
static char sram_data[101] = { 0 };
static char copy_status[32] = { 0 };

void on_irq() 
{	
  if(REG_IF & IRQ_VBLANK) {
    // Clear screen
    printf("\x1b[2J");

    printf("\n\nReading and Writing GBA SRAM!\n\n");
    printf("Using your flash cartridge\n");
    printf("software you can load text data\n");
    printf("into SRAM to test this program.\n");
    printf("SRAM is the 'save game' area in\n");
    printf("the cartridge.\n\n");
    printf("Press:\n");
    printf("'A' to display some SRAM data.\n");
    printf("'B' to set SRAM to some text,\n");
    printf("then press 'A' to display it.\n\n");
  
    printf("Card ID = %s\n", card_id);			
    printf("Copy Status:\n");
    printf("%s\n", copy_status);			
    printf("SRAM Data:\n");
    printf("%s", sram_data);			

    // Tell the DS we handled the VBLANK interrupt
    VBLANK_INTR_WAIT_FLAGS |= IRQ_VBLANK;
    REG_IF |= IRQ_VBLANK;
  }
  else {
    // Ignore all other interrupts
    REG_IF = REG_IF;
  }
}

void InitInterruptHandler()
{
  REG_IME = 0;
  IRQ_HANDLER = on_irq;
  REG_IE = IRQ_VBLANK;
  REG_IF = ~0;
  DISP_SR = DISP_VBLANK_IRQ;
  REG_IME = 1;
}

static void memcpy(char* dest, char const* src, int size) {
  while(size--) 
    *dest++ = *src++;
}

static void memset(char* dest, char fill, int size) {
  while(size--)
    *dest++ = fill;
}

/* Return true if the card id is 'PASS' */
static int is_homebrew_cartridge() {
  return 
    card_id[0] == 'P' &&
    card_id[1] == 'A' &&
    card_id[2] == 'S' &&
    card_id[3] == 'S';
}

int main(void)
{
  powerON(POWER_ALL);  
  videoSetMode(MODE_0_2D | DISPLAY_BG0_ACTIVE);
  vramSetBankA(VRAM_A_MAIN_BG);
  BG0_CR = BG_MAP_BASE(31);
  BG_PALETTE[255] = RGB15(31,31,31);
  lcdSwap();

  /* Clear out our local copy of 1st 100 bytes of SRAM */
  memset(sram_data, 0, sizeof(sram_data));
  memset(copy_status, 0, sizeof(copy_status));

  /* Enable the ARM9 to access the GBA cartridge memory area */
  WAIT_CR &= ~0x80;

  /* Copy contents of the 4 character ROM identifier into a local
     variable. This should be 'PASS' for all homebrew ROM's. The
     identifier is located at 0x080000AC.*/
  memcpy(card_id, (char*)0x080000AC, 4);

  /* Set up the vertical blank interrupt where we display our data */
  InitInterruptHandler();
	
  consoleInitDefault((u16*)SCREEN_BASE_BLOCK(31), (u16*)CHAR_BASE_BLOCK(0), 16);
  while(1) {
    int keys = ~REG_KEYINPUT;
    if(keys & KEY_A) {
      /* Copy from SRAM to our local variable to display */
      memcpy(sram_data, (char*)SRAM, sizeof(sram_data) - 1);
    }
    if(keys & KEY_B) {
      /* Copy a string of text to SRAM if the cartridge has a homebrew
	 ROM in it. */
      const char text[] = "Hello from SRAM!";
      const char error[] = "Not Homebrew! Copy failed.";
      const char success[] = "Copy succeeded.";
      if(is_homebrew_cartridge()) {
	memcpy((char*)SRAM, text, sizeof(text));
	memcpy(copy_status, success, sizeof(success));
      }
      else
	memcpy(copy_status, error, sizeof(error));

    }
    swiWaitForVBlank();
  }
  return 0;
}