/*******************************************************************************************
*
*   raylib [shaders] example - julia sets
*
*   NOTE: This example requires raylib OpenGL 3.3 or ES2 versions for shaders support,
*         OpenGL 1.1 does not support shaders, recompile raylib to OpenGL 3.3 version.
*
*   NOTE: Shaders used in this example are #version 330 (OpenGL 3.3).
*
*   This example has been created using raylib 2.5 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Example contributed by eggmund (@eggmund) and reviewed by Ramon Santamaria (@raysan5)
*
*   Copyright (c) 2019 eggmund (@eggmund) and Ramon Santamaria (@raysan5)
*
********************************************************************************************/

#include "raylib.h"

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

// A few good julia sets
const float POINTS_OF_INTEREST[6][2] =
{
    { -0.348827, 0.607167 },
    { -0.786268, 0.169728 },
    { -0.8, 0.156 },
    { 0.285, 0.0 },
    { -0.835, -0.2321 },
    { -0.70176, -0.3842 },
};

int main(void)
{
    // Initialization
    //--------------------------------------------------------------------------------------
    const int screenWidth = 800;
    const int screenHeight = 450;

    InitWindow(screenWidth, screenHeight, "raylib [shaders] example - julia sets");

    // Load julia set shader
    // NOTE: Defining 0 (NULL) for vertex shader forces usage of internal default vertex shader
    Shader shader = LoadShader(0, FormatText("resources/shaders/glsl%i/julia_set.fs", GLSL_VERSION));

    // c constant to use in z^2 + c
    float c[2] = { POINTS_OF_INTEREST[0][0], POINTS_OF_INTEREST[0][1] };

    // Offset and zoom to draw the julia set at. (centered on screen and default size)
    float offset[2] = { -(float)screenWidth/2, -(float)screenHeight/2 };
    float zoom = 1.0f;

    Vector2 offsetSpeed = { 0.0f, 0.0f };

    // Get variable (uniform) locations on the shader to connect with the program
    // NOTE: If uniform variable could not be found in the shader, function returns -1
    int cLoc = GetShaderLocation(shader, "c");
    int zoomLoc = GetShaderLocation(shader, "zoom");
    int offsetLoc = GetShaderLocation(shader, "offset");

    // Tell the shader what the screen dimensions, zoom, offset and c are
    float screenDims[2] = { (float)screenWidth, (float)screenHeight };
    SetShaderValue(shader, GetShaderLocation(shader, "screenDims"), screenDims, UNIFORM_VEC2);

    SetShaderValue(shader, cLoc, c, UNIFORM_VEC2);
    SetShaderValue(shader, zoomLoc, &zoom, UNIFORM_FLOAT);
    SetShaderValue(shader, offsetLoc, offset, UNIFORM_VEC2);

    // Create a RenderTexture2D to be used for render to texture
    RenderTexture2D target = LoadRenderTexture(screenWidth, screenHeight);

    int incrementSpeed = 0;         // Multiplier of speed to change c value
    bool showControls = true;       // Show controls
    bool pause = false;             // Pause animation

    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
    //--------------------------------------------------------------------------------------

    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        // Update
        //----------------------------------------------------------------------------------
        // Press [1 - 6] to reset c to a point of interest
        if (IsKeyPressed(KEY_ONE) ||
            IsKeyPressed(KEY_TWO) ||
            IsKeyPressed(KEY_THREE) ||
            IsKeyPressed(KEY_FOUR) ||
            IsKeyPressed(KEY_FIVE) ||
            IsKeyPressed(KEY_SIX))
        {
            if (IsKeyPressed(KEY_ONE)) c[0] = POINTS_OF_INTEREST[0][0], c[1] = POINTS_OF_INTEREST[0][1];
            else if (IsKeyPressed(KEY_TWO)) c[0] = POINTS_OF_INTEREST[1][0], c[1] = POINTS_OF_INTEREST[1][1];
            else if (IsKeyPressed(KEY_THREE)) c[0] = POINTS_OF_INTEREST[2][0], c[1] = POINTS_OF_INTEREST[2][1];
            else if (IsKeyPressed(KEY_FOUR)) c[0] = POINTS_OF_INTEREST[3][0], c[1] = POINTS_OF_INTEREST[3][1];
            else if (IsKeyPressed(KEY_FIVE)) c[0] = POINTS_OF_INTEREST[4][0], c[1] = POINTS_OF_INTEREST[4][1];
            else if (IsKeyPressed(KEY_SIX)) c[0] = POINTS_OF_INTEREST[5][0], c[1] = POINTS_OF_INTEREST[5][1];

            SetShaderValue(shader, cLoc, c, UNIFORM_VEC2);
        }

        if (IsKeyPressed(KEY_SPACE)) pause = !pause;                 // Pause animation (c change)
        if (IsKeyPressed(KEY_F1)) showControls = !showControls;  // Toggle whether or not to show controls

        if (!pause)
        {
            if (IsKeyPressed(KEY_RIGHT)) incrementSpeed++;
            else if (IsKeyPressed(KEY_LEFT)) incrementSpeed--;

            // TODO: The idea is to zoom and move around with mouse
            // Probably offset movement should be proportional to zoom level
            if (IsMouseButtonDown(MOUSE_LEFT_BUTTON) || IsMouseButtonDown(MOUSE_RIGHT_BUTTON))
            {
                if (IsMouseButtonDown(MOUSE_LEFT_BUTTON)) zoom += zoom*0.003f;
                if (IsMouseButtonDown(MOUSE_RIGHT_BUTTON)) zoom -= zoom*0.003f;

                Vector2 mousePos = GetMousePosition();

                offsetSpeed.x = mousePos.x -(float)screenWidth/2;
                offsetSpeed.y = mousePos.y -(float)screenHeight/2;

                // Slowly move camera to targetOffset
                offset[0] += GetFrameTime()*offsetSpeed.x*0.8f;
                offset[1] += GetFrameTime()*offsetSpeed.y*0.8f;
            }
            else offsetSpeed = (Vector2){ 0.0f, 0.0f };

            SetShaderValue(shader, zoomLoc, &zoom, UNIFORM_FLOAT);
            SetShaderValue(shader, offsetLoc, offset, UNIFORM_VEC2);

            // Increment c value with time
            float amount = GetFrameTime()*incrementSpeed*0.0005f;
            c[0] += amount;
            c[1] += amount;

            SetShaderValue(shader, cLoc, c, UNIFORM_VEC2);
        }
        //----------------------------------------------------------------------------------

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

            ClearBackground(BLACK);         // Clear the screen of the previous frame.

            // Using a render texture to draw Julia set
            BeginTextureMode(target);       // Enable drawing to texture
                ClearBackground(BLACK);     // Clear the render texture

                // Draw a rectangle in shader mode to be used as shader canvas
                // NOTE: Rectangle uses font white character texture coordinates,
                // so shader can not be applied here directly because input vertexTexCoord
                // do not represent full screen coordinates (space where want to apply shader)
                DrawRectangle(0, 0, GetScreenWidth(), GetScreenHeight(), BLACK);
            EndTextureMode();

            // Draw the saved texture and rendered julia set with shader
            // NOTE: We do not invert texture on Y, already considered inside shader
            BeginShaderMode(shader);
                DrawTexture(target.texture, 0, 0, WHITE);
            EndShaderMode();

            if (showControls)
            {
                DrawText("Press Mouse buttons right/left to zoom in/out and move", 10, 15, 10, RAYWHITE);
                DrawText("Press KEY_F1 to toggle these controls", 10, 30, 10, RAYWHITE);
                DrawText("Press KEYS [1 - 6] to change point of interest", 10, 45, 10, RAYWHITE);
                DrawText("Press KEY_LEFT | KEY_RIGHT to change speed", 10, 60, 10, RAYWHITE);
                DrawText("Press KEY_SPACE to pause movement animation", 10, 75, 10, RAYWHITE);
            }

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

    // De-Initialization
    //--------------------------------------------------------------------------------------
    UnloadShader(shader);           // Unload shader
    UnloadRenderTexture(target);    // Unload render texture

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

    return 0;
}
