// SDL2_15 [SDL StarField v0.1].nova
// Original version by: Will Schenk (written in Java 1.1).
// Updated & converted to Nova by: Robert Platt - 25/02/2026.


using namespace lib.emscripten;
using namespace lib.math;
using namespace lib.sdl2;


// The Star class to handle 3D projection and rendering.
class Star 
{
    public int x, y, z;
    public int hPos, vPos;


    public Star( )
    {
        reset( true );
    }


    public void reset( bool randomZ )
    {
        x = ( Math.rand( ) % 640 ) - 320;
        y = ( Math.rand( ) % 480 ) - 240;

        if ( x == 0 && y == 0 ) x = 10;

        z = randomZ ? ( Math.rand( ) % 100 ) : 100;
    }


    public void updateAndRender( SDL_Renderer r, int renderStyle )
    {
        z -= 1;

        if ( z < -63 ) reset( false );

        // 3D to 2D Projection.
        hPos = ( x * 64 ) / (64 + z ) + 320;
        vPos = ( y * 64 ) / (64 + z ) + 240;

        // Screen bounds check.
        if ( hPos < 0 || hPos > 640 || vPos < 0 || vPos > 480 )
        {
            reset( false );
        }

        // Depth shading.
        if ( z > 50 ) SDL2.SDL_SetRenderDrawColor( r, 128, 128, 128, 255 );
        else if ( z > 25 ) SDL2.SDL_SetRenderDrawColor( r, 192, 192, 192, 255) ;
        else SDL2.SDL_SetRenderDrawColor( r, 255, 255, 255, 255 );

        // Render shapes based on the current 'renderStyle'.
        if ( renderStyle == 0 )
        {
            int size = ( 100 - z ) / 50;
            if ( size <= 0 ) size = 1;
            SDL_Rect rect = new SDL_Rect( hPos, vPos, size, size );
            SDL2.SDL_RenderFillRect( r, rect );
        }
        else 
        {
            int size = ( 100 - z ) / 20;
            SDL2.SDL_RenderDrawLine( r, hPos - size, vPos, hPos + size, vPos );
            SDL2.SDL_RenderDrawLine( r, hPos, vPos - size, hPos, vPos + size );
        }
    }
}



// The main application class.
class StarField
{
    private static SDL_Window w;
    private static SDL_Renderer r;
    private static bool runFlag;

    private static Star[] stars;
    private static int starType;

    private static int WIDTH;
    private static int HEIGHT;
    private static int NUM_STARS;


    public static void main( String[] args )
    {
        Stream.writeLine( "SDL2_15 [SDL StarField v0.1].nova" );


        runFlag = true;
        starType = 0;
        WIDTH = 640;
        HEIGHT = 480;
        NUM_STARS = 250;


        Emscripten.disableControls( );

        SDL2.SDL_Init( SDL2.SDL_INIT_VIDEO );

        w = SDL2.SDL_CreateWindow( "SDL2_15 [SDL StarField v0.1]",
                                   SDL2.SDL_WINDOWPOS_CENTERED,
                                   SDL2.SDL_WINDOWPOS_CENTERED,
                                   WIDTH,
                                   HEIGHT,
                                   SDL2.SDL_WINDOW_SHOWN );

        if ( w == null ) return;

        r = SDL2.SDL_CreateRenderer( w, -1, SDL2.SDL_RENDERER_ACCELERATED | SDL2.SDL_RENDERER_PRESENTVSYNC );

        stars = new Star[ NUM_STARS ];

        for ( int i = 0; i < NUM_STARS; i++ )
        {
            stars[ i ] = new Star( );
        }

        if ( Emscripten.isActive( ) )
        {
            int simulate_infinite_loop = 1;  // Call the function repeatedly.
            int fps = -1;  // Call the function as fast as the browser wants to render (typically 60fps).
            Emscripten.setMainLoop( renderFrame, fps, simulate_infinite_loop );
        }
        else 
        {
            do
            {
                renderFrame( );
            }
            while ( runFlag );
        }

        SDL2.SDL_DestroyRenderer( r );
        SDL2.SDL_DestroyWindow( w );
        SDL2.SDL_Quit( );
    }


    public static void renderFrame( )
    {
        SDL_Event e = SDL2.SDL_PollEvent( );

        if ( e != null )
        {
            if ( e.id == SDL2.SDL_QUIT )
            {
                runFlag = false;
            }
            else if ( e.id == SDL2.SDL_KEYDOWN )
            {
                // Cast to a keyboard event.
                SDL_KeyboardEvent kbEvent = (SDL_KeyboardEvent)e;

                if ( kbEvent.sym == SDL2.SDLK_SPACE )
                {
                    starType = ( starType == 0 ) ? 1 : 0;
                }
            }
        }


        SDL2.SDL_SetRenderDrawColor( r, 0, 0, 77, 255 );
        SDL2.SDL_RenderClear( r );

        for ( int i = 0; i < NUM_STARS; i++ )
        {
            stars[ i ].updateAndRender( r, starType );
        }

        SDL2.SDL_RenderPresent( r );
    }
}