using Raylib;
using static Raylib.Raylib;
using static Raylib.BlendMode;

public partial class textures_particles_blending
{
    /*******************************************************************************************
    *
    *   raylib example - particles blending
    *
    *   This example has been created using raylib 1.7 (www.raylib.com)
    *   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
    *
    *   Copyright (c) 2017 Ramon Santamaria (@raysan5)
    *
    ********************************************************************************************/
    
    
    public const int MAX_PARTICLES = 200;

    // Particle structure with basic data
    struct Particle
    {
        public Vector2 position;
        public Color color;
        public float alpha;
        public float size;
        public float rotation;
        public bool active;        // NOTE: Use it to activate/deactive particle
    }
    
    public static int Main()
    {
        // Initialization
        //--------------------------------------------------------------------------------------
        int screenWidth = 800;
        int screenHeight = 450;
    
        InitWindow(screenWidth, screenHeight, "raylib [textures] example - particles blending");
        
        // Particles pool, reuse them!
        Particle[] mouseTail = new Particle[MAX_PARTICLES]; 
        
        // Initialize particles
        for (int i = 0; i < MAX_PARTICLES; i++)
        {
            mouseTail[i].position = new Vector2( 0, 0 );
            mouseTail[i].color = new Color( GetRandomValue(0, 255), GetRandomValue(0, 255), GetRandomValue(0, 255), 255 );
            mouseTail[i].alpha = 1.0f;
            mouseTail[i].size = (float)GetRandomValue(1, 30)/20.0f;
            mouseTail[i].rotation = GetRandomValue(0, 360);
            mouseTail[i].active = false;
        }
        
        float gravity = 3.0f;
    
        Texture2D smoke = LoadTexture("resources/smoke.png");
        
        int blending = (int)BLEND_ALPHA;
        
        SetTargetFPS(60);
        //--------------------------------------------------------------------------------------
    
        // Main game loop
        while (!WindowShouldClose())    // Detect window close button or ESC key
        {
            // Update
            //----------------------------------------------------------------------------------
            
            // Activate one particle every frame and Update active particles
            // NOTE: Particles initial position should be mouse position when activated
            // NOTE: Particles fall down with gravity and rotation... and disappear after 2 seconds (alpha = 0)
            // NOTE: When a particle disappears, active = false and it can be reused.
            for (int i = 0; i < MAX_PARTICLES; i++)
            {
                if (!mouseTail[i].active)
                {
                    mouseTail[i].active = true;
                    mouseTail[i].alpha = 1.0f;
                    mouseTail[i].position = GetMousePosition();
                    i = MAX_PARTICLES;
                }
            }
    
            for (int i = 0; i < MAX_PARTICLES; i++)
            {
                if (mouseTail[i].active)
                {
                    mouseTail[i].position.y += gravity;
                    mouseTail[i].alpha -= 0.01f;
                    
                    if (mouseTail[i].alpha <= 0.0f) mouseTail[i].active = false;
                    
                    mouseTail[i].rotation += 5.0f;
                }
            }
            
            if (IsKeyPressed(KEY_SPACE))
            {
                if (blending == (int)BLEND_ALPHA) blending = (int)BLEND_ADDITIVE;
                else blending = (int)BLEND_ALPHA;
            }
            //----------------------------------------------------------------------------------
    
            // Draw
            //----------------------------------------------------------------------------------
            BeginDrawing();
    
                ClearBackground(DARKGRAY);
                
                BeginBlendMode(blending);
    
                    // Draw active particles
                    for (int i = 0; i < MAX_PARTICLES; i++)
                    {
                        if (mouseTail[i].active) DrawTexturePro(smoke, new Rectangle( 0, 0, smoke.width, smoke.height ), 
                                                               new Rectangle( mouseTail[i].position.x, mouseTail[i].position.y, smoke.width*mouseTail[i].size, smoke.height*mouseTail[i].size ),
                                                               new Vector2( smoke.width*mouseTail[i].size/2, smoke.height*mouseTail[i].size/2 ), mouseTail[i].rotation,
                                                               Fade(mouseTail[i].color, mouseTail[i].alpha));
                    }
                
                EndBlendMode();
                
                DrawText("PRESS SPACE to CHANGE BLENDING MODE", 180, 20, 20, BLACK);
                
                if (blending == (int)BLEND_ALPHA) DrawText("ALPHA BLENDING", 290, screenHeight - 40, 20, BLACK);
                else DrawText("ADDITIVE BLENDING", 280, screenHeight - 40, 20, RAYWHITE);
                
            EndDrawing();
            //----------------------------------------------------------------------------------
        }
    
        // De-Initialization
        //--------------------------------------------------------------------------------------
        UnloadTexture(smoke);
        
        CloseWindow();        // Close window and OpenGL context
        //--------------------------------------------------------------------------------------
    
        return 0;
    }    
}