/*******************************************************************************************
*
*   raylib [textures] example - Texture drawing
*
*   This example illustrates how to draw on a blank texture using a shader
*
*   This example has been created using raylib 2.0 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Example contributed by Michał Ciesielski and reviewed by Ramon Santamaria (@raysan5)
*
*   Copyright (c) 2019 Michał Ciesielski and Ramon Santamaria (@raysan5)
*
********************************************************************************************/

#include "raylib.h"

#if defined(PLATFORM_WEB)
    #include <emscripten/emscripten.h>
#endif

#if defined(PLATFORM_DESKTOP)
    #define GLSL_VERSION            330
#else   // PLATFORM_RPI, PLATFORM_ANDROID, PLATFORM_WEB
    #define GLSL_VERSION            100
#endif

//----------------------------------------------------------------------------------
// Global Variables Definition
//----------------------------------------------------------------------------------
const int screenWidth = 800;
const int screenHeight = 450;

// NOTE: Textures MUST be loaded after Window initialization (OpenGL context is required)

Texture2D texture = { 0 };
Shader shader = { 0 };

static float time = 0.0f;   // WARNING: This variable MUST be static, it seems to collide somewhere
int timeLoc = 0;

//----------------------------------------------------------------------------------
// Module Functions Declaration
//----------------------------------------------------------------------------------
void UpdateDrawFrame(void);     // Update and Draw one frame

//----------------------------------------------------------------------------------
// Program Main Entry Point
//----------------------------------------------------------------------------------
int main(void)
{
    // Initialization
    //--------------------------------------------------------------------------------------
    InitWindow(screenWidth, screenHeight, "raylib [shaders] example - texture drawing");

    Image imBlank = GenImageColor(1024, 1024, BLANK);
    texture = LoadTextureFromImage(imBlank);  // Load blank texture to fill on shader
    UnloadImage(imBlank);

    // NOTE: Using GLSL 330 shader version, on OpenGL ES 2.0 use GLSL 100 shader version
    shader = LoadShader(0, FormatText("resources/shaders/glsl%i/cubes_panning.fs", GLSL_VERSION));

    timeLoc = GetShaderLocation(shader, "uTime");
    SetShaderValue(shader, timeLoc, &time, UNIFORM_FLOAT);

#if defined(PLATFORM_WEB)
    emscripten_set_main_loop(UpdateDrawFrame, 0, 1);
#else
    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
    //--------------------------------------------------------------------------------------

    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        UpdateDrawFrame();
    }
#endif

    // De-Initialization
    //--------------------------------------------------------------------------------------
    UnloadShader(shader);

    CloseWindow();        // Close window and OpenGL context
    //--------------------------------------------------------------------------------------

    return 0;
}

//----------------------------------------------------------------------------------
// Module Functions Definition
//----------------------------------------------------------------------------------
void UpdateDrawFrame(void)
{
    // Update
    //----------------------------------------------------------------------------------
    time = GetTime();
    SetShaderValue(shader, timeLoc, &time, UNIFORM_FLOAT);
    //----------------------------------------------------------------------------------

    // Draw
    //----------------------------------------------------------------------------------
    BeginDrawing();

        ClearBackground(RAYWHITE);

        BeginShaderMode(shader);    // Enable our custom shader for next shapes/textures drawings
            DrawTexture(texture, 0, 0, WHITE);  // Drawing BLANK texture, all magic happens on shader
        EndShaderMode();            // Disable our custom shader, return to default shader

        DrawText("BACKGROUND is PAINTED and ANIMATED on SHADER!", 10, 10, 20, MAROON);

    EndDrawing();
    //----------------------------------------------------------------------------------
}