/*******************************************************************************************
*
*   raylib [rlgl] example - Using rlgl module as standalone module
*
*   NOTE: This example requires OpenGL 3.3 or ES2 versions for shaders support,
*         OpenGL 1.1 does not support shaders but it can also be used.
*
*   Compile rlgl module using:
*   gcc -c rlgl.c -Wall -std=c99 -DRLGL_STANDALONE -DRAYMATH_IMPLEMENTATION -DGRAPHICS_API_OPENGL_33
*
*   Compile example using:
*   gcc -o $(NAME_PART).exe $(FILE_NAME) rlgl.o -lglfw3 -lopengl32 -lgdi32 -std=c99
*
*   This example has been created using raylib 1.5 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Copyright (c) 2015 Ramon Santamaria (@raysan5)
*
********************************************************************************************/

#include "glad.h"               // Extensions loading library
#include <GLFW/glfw3.h>         // Windows/Context and inputs management

#define RLGL_STANDALONE
#include "rlgl.h"               // rlgl library: OpenGL 1.1 immediate-mode style coding

#include <stdlib.h>             // Required for: abs()


#define RED        (Color){ 230, 41, 55, 255 }     // Red
#define MAROON     (Color){ 190, 33, 55, 255 }     // Maroon
#define RAYWHITE   (Color){ 245, 245, 245, 255 }   // My own White (raylib logo)
#define DARKGRAY   (Color){ 80, 80, 80, 255 }      // Dark Gray
#define WHITE      (Color){ 255, 255, 255, 255 }   // White

//----------------------------------------------------------------------------------
// Types and Structures Definition
//----------------------------------------------------------------------------------

// Rectangle type
typedef struct Rectangle {
    int x;
    int y;
    int width;
    int height;
} Rectangle;

//----------------------------------------------------------------------------------
// Module specific Functions Declaration
//----------------------------------------------------------------------------------
static void ErrorCallback(int error, const char* description);
static void KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods);

// Drawing functions (uses rlgl functionality)
static void DrawGrid(int slices, float spacing);
static void DrawCube(Vector3 position, float width, float height, float length, Color color);
static void DrawCubeWires(Vector3 position, float width, float height, float length, Color color);
static void DrawRectangleV(Vector2 position, Vector2 size, Color color);
static void DrawTextureRec(Texture2D texture, Rectangle sourceRec, Vector2 position, Color tint);
static void DrawTexturePro(Texture2D texture, Rectangle sourceRec, Rectangle destRec, Vector2 origin, float rotation, Color tint);

//----------------------------------------------------------------------------------
// Main Entry point
//----------------------------------------------------------------------------------
int main(void)
{
    // Initialization
    //--------------------------------------------------------------------------------------
    const int screenWidth = 1080;
    const int screenHeight = 600;
    
    // GLFW3 Initialization + OpenGL 3.3 Context + Extensions
    //--------------------------------------------------------
    glfwSetErrorCallback(ErrorCallback);
    
    if (!glfwInit())
    {
        TraceLog(WARNING, "GLFW3: Can not initialize GLFW");
        return 1;
    }
    else TraceLog(INFO, "GLFW3: GLFW initialized successfully");
    
    glfwWindowHint(GLFW_SAMPLES, 4);
    glfwWindowHint(GLFW_DEPTH_BITS, 16);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_DEBUG_CONTEXT, GL_TRUE);
   
    GLFWwindow *window = glfwCreateWindow(screenWidth, screenHeight, "rlgl standalone", NULL, NULL);
    
    if (!window)
    {
        glfwTerminate();
        return 2;
    }
    else TraceLog(INFO, "GLFW3: Window created successfully");
    
    glfwSetKeyCallback(window, KeyCallback);
    
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);

    // Load OpenGL 3.3 extensions
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        TraceLog(WARNING, "GLAD: Cannot load OpenGL extensions");
        return 3;
    }
    else TraceLog(INFO, "GLAD: OpenGL extensions loaded successfully");
    //--------------------------------------------------------
    
    // Initialize rlgl internal buffers and OpenGL state
    rlglInit();
    rlglInitGraphics(0, 0, screenWidth, screenHeight);
    rlClearColor(245, 245, 245, 255);   // Define clear color
    rlEnableDepthTest();                // Enable DEPTH_TEST for 3D
    
    Shader distortion = LoadShader("base.vs", "distortion.fs");
    
    // TODO: Upload to distortion shader configuration parameters (screen size, etc.)
    //SetShaderValue(Shader shader, int uniformLoc, float *value, int size);
    
    // Create a RenderTexture2D to be used for render to texture
    RenderTexture2D target = rlglLoadRenderTexture(screenWidth, screenHeight);
    
    Vector3 cubePosition = { 0.0f, 0.0f, 0.0f };
    
    Camera camera;
    camera.position = (Vector3){ 5.0f, 5.0f, 5.0f };    // Camera position
    camera.target = (Vector3){ 0.0f, 0.0f, 0.0f };      // Camera looking at point
    camera.up = (Vector3){ 0.0f, 1.0f, 0.0f };          // Camera up vector (rotation towards target)
    camera.fovy = 60.0f;                               // Camera field-of-view Y
    //--------------------------------------------------------------------------------------    

    // Main game loop    
    while (!glfwWindowShouldClose(window)) 
    {
        // Update
        //----------------------------------------------------------------------------------
        // ...
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        rlEnableRenderTexture(target.id);   // Enable render target
    
        rlClearScreenBuffers();             // Clear current framebuffer
    
        for (int i = 0; i < 2; i++)
        {
            rlViewport(i*screenWidth/2, 0, screenWidth/2, screenHeight); 
    
            // Calculate projection matrix (from perspective) and view matrix from camera look at
            // TODO: Consider every eye fovy
            Matrix matProj = MatrixPerspective(camera.fovy, (double)(screenWidth/2)/(double)screenHeight, 0.01, 1000.0);
            MatrixTranspose(&matProj);
            
            // TODO: Recalculate view matrix considering IPD (inter-pupillary-distance)
            Matrix matView = MatrixLookAt(camera.position, camera.target, camera.up);

            SetMatrixModelview(matView);    // Replace internal modelview matrix by a custom one
            SetMatrixProjection(matProj);   // Replace internal projection matrix by a custom one

            DrawCube(cubePosition, 2.0f, 2.0f, 2.0f, RED);
            DrawCubeWires(cubePosition, 2.0f, 2.0f, 2.0f, RAYWHITE);
            DrawGrid(10, 1.0f);

            // NOTE: Internal buffers drawing (3D data)
            rlglDraw();
            
            // Draw '2D' elements in the scene (GUI)
#define RLGL_CREATE_MATRIX_MANUALLY
#if defined(RLGL_CREATE_MATRIX_MANUALLY)

            matProj = MatrixOrtho(0.0, screenWidth/2, screenHeight, 0.0, 0.0, 1.0);
            MatrixTranspose(&matProj);
            matView = MatrixIdentity();
            
            SetMatrixModelview(matView);    // Replace internal modelview matrix by a custom one
            SetMatrixProjection(matProj);   // Replace internal projection matrix by a custom one

#else   // Let rlgl generate and multiply matrix internally

            rlMatrixMode(RL_PROJECTION);                            // Enable internal projection matrix
            rlLoadIdentity();                                       // Reset internal projection matrix
            rlOrtho(0.0, screenWidth/2, screenHeight, 0.0, 0.0, 1.0); // Recalculate internal projection matrix
            rlMatrixMode(RL_MODELVIEW);                             // Enable internal modelview matrix
            rlLoadIdentity();                                       // Reset internal modelview matrix
#endif
            // TODO: 2D not drawing properly on stereo rendering
            //DrawRectangleV((Vector2){ 10.0f, 10.0f }, (Vector2){ 500.0f, 20.0f }, DARKGRAY);

            // NOTE: Internal buffers drawing (2D data)
            rlglDraw();
        }
        
        rlDisableRenderTexture();           // Disable render target

        // Set viewport to default framebuffer size (screen size)
        rlViewport(0, 0, screenWidth, screenHeight);
        
        // Let rlgl reconfigure internal matrices using OpenGL 1.1 style coding
        rlMatrixMode(RL_PROJECTION);                            // Enable internal projection matrix
        rlLoadIdentity();                                       // Reset internal projection matrix
        rlOrtho(0.0, screenWidth, screenHeight, 0.0, 0.0, 1.0); // Recalculate internal projection matrix
        rlMatrixMode(RL_MODELVIEW);                             // Enable internal modelview matrix
        rlLoadIdentity();                                       // Reset internal modelview matrix
    
        // Draw RenderTexture (fbo) using distortion shader 
        BeginShaderMode(distortion);
            // NOTE: Render texture must be y-flipped due to default OpenGL coordinates (left-bottom)
            DrawTextureRec(target.texture, (Rectangle){ 0, 0, target.texture.width, -target.texture.height }, (Vector2){ 0, 0 }, WHITE);
        EndShaderMode();
            
        glfwSwapBuffers(window);
        glfwPollEvents();
        //----------------------------------------------------------------------------------
    }

    // De-Initialization
    //--------------------------------------------------------------------------------------
    UnloadShader(distortion);
    
    rlglClose();                // Unload rlgl internal buffers and default shader/texture
    
    glfwDestroyWindow(window);
    glfwTerminate();
    //--------------------------------------------------------------------------------------
    
    return 0;
}

//----------------------------------------------------------------------------------
// Module specific Functions Definitions
//----------------------------------------------------------------------------------

// GLFW3: Error callback
static void ErrorCallback(int error, const char* description)
{
    TraceLog(ERROR, description);
}

// GLFW3: Keyboard callback
static void KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
    {
        glfwSetWindowShouldClose(window, GL_TRUE);
    }
}

// Draw rectangle using rlgl OpenGL 1.1 style coding (translated to OpenGL 3.3 internally)
static void DrawRectangleV(Vector2 position, Vector2 size, Color color)
{
    rlBegin(RL_TRIANGLES);
        rlColor4ub(color.r, color.g, color.b, color.a);

        rlVertex2i(position.x, position.y);
        rlVertex2i(position.x, position.y + size.y);
        rlVertex2i(position.x + size.x, position.y + size.y);

        rlVertex2i(position.x, position.y);
        rlVertex2i(position.x + size.x, position.y + size.y);
        rlVertex2i(position.x + size.x, position.y);
    rlEnd();
}

// Draw a grid centered at (0, 0, 0)
static void DrawGrid(int slices, float spacing)
{
    int halfSlices = slices / 2;

    rlBegin(RL_LINES);
        for(int i = -halfSlices; i <= halfSlices; i++)
        {
            if (i == 0)
            {
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
            }
            else
            {
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
            }

            rlVertex3f((float)i*spacing, 0.0f, (float)-halfSlices*spacing);
            rlVertex3f((float)i*spacing, 0.0f, (float)halfSlices*spacing);

            rlVertex3f((float)-halfSlices*spacing, 0.0f, (float)i*spacing);
            rlVertex3f((float)halfSlices*spacing, 0.0f, (float)i*spacing);
        }
    rlEnd();
}

// Draw cube
// NOTE: Cube position is the center position
void DrawCube(Vector3 position, float width, float height, float length, Color color)
{
    float x = 0.0f;
    float y = 0.0f;
    float z = 0.0f;

    rlPushMatrix();

        // NOTE: Be careful! Function order matters (rotate -> scale -> translate)
        rlTranslatef(position.x, position.y, position.z);
        //rlScalef(2.0f, 2.0f, 2.0f);
        //rlRotatef(45, 0, 1, 0);

        rlBegin(RL_TRIANGLES);
            rlColor4ub(color.r, color.g, color.b, color.a);

            // Front Face -----------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left

            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right

            // Back Face ------------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Bottom Left
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right

            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left

            // Top Face -------------------------------------------------------
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Bottom Left
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Bottom Right

            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Bottom Right

            // Bottom Face ----------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right
            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Bottom Left

            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Top Right
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Top Left

            // Right face -----------------------------------------------------
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Left

            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Left

            // Left Face ------------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Right

            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Bottom Left
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Bottom Right
        rlEnd();
    rlPopMatrix();
}

// Draw cube wires
void DrawCubeWires(Vector3 position, float width, float height, float length, Color color)
{
    float x = 0.0f;
    float y = 0.0f;
    float z = 0.0f;

    rlPushMatrix();

        rlTranslatef(position.x, position.y, position.z);
        //rlRotatef(45, 0, 1, 0);

        rlBegin(RL_LINES);
            rlColor4ub(color.r, color.g, color.b, color.a);

            // Front Face -----------------------------------------------------
            // Bottom Line
            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right

            // Left Line
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Right

            // Top Line
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left

            // Right Line
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Bottom Left

            // Back Face ------------------------------------------------------
            // Bottom Line
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right

            // Left Line
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right

            // Top Line
            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left

            // Right Line
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Bottom Left

            // Top Face -------------------------------------------------------
            // Left Line
            rlVertex3f(x-width/2, y+height/2, z+length/2);  // Top Left Front
            rlVertex3f(x-width/2, y+height/2, z-length/2);  // Top Left Back

            // Right Line
            rlVertex3f(x+width/2, y+height/2, z+length/2);  // Top Right Front
            rlVertex3f(x+width/2, y+height/2, z-length/2);  // Top Right Back

            // Bottom Face  ---------------------------------------------------
            // Left Line
            rlVertex3f(x-width/2, y-height/2, z+length/2);  // Top Left Front
            rlVertex3f(x-width/2, y-height/2, z-length/2);  // Top Left Back

            // Right Line
            rlVertex3f(x+width/2, y-height/2, z+length/2);  // Top Right Front
            rlVertex3f(x+width/2, y-height/2, z-length/2);  // Top Right Back
        rlEnd();
    rlPopMatrix();
}

// Draw a part of a texture (defined by a rectangle)
static void DrawTextureRec(Texture2D texture, Rectangle sourceRec, Vector2 position, Color tint)
{
    Rectangle destRec = { (int)position.x, (int)position.y, abs(sourceRec.width), abs(sourceRec.height) };
    Vector2 origin = { 0, 0 };

    DrawTexturePro(texture, sourceRec, destRec, origin, 0.0f, tint);
}

// Draw a part of a texture (defined by a rectangle) with 'pro' parameters
// NOTE: origin is relative to destination rectangle size
static void DrawTexturePro(Texture2D texture, Rectangle sourceRec, Rectangle destRec, Vector2 origin, float rotation, Color tint)
{
    // Check if texture is valid
    if (texture.id != 0)
    {
        if (sourceRec.width < 0) sourceRec.x -= sourceRec.width;
        if (sourceRec.height < 0) sourceRec.y -= sourceRec.height;
        
        rlEnableTexture(texture.id);

        rlPushMatrix();
            rlTranslatef(destRec.x, destRec.y, 0);
            rlRotatef(rotation, 0, 0, 1);
            rlTranslatef(-origin.x, -origin.y, 0);

            rlBegin(RL_QUADS);
                rlColor4ub(tint.r, tint.g, tint.b, tint.a);
                rlNormal3f(0.0f, 0.0f, 1.0f);                          // Normal vector pointing towards viewer

                // Bottom-left corner for texture and quad
                rlTexCoord2f((float)sourceRec.x / texture.width, (float)sourceRec.y / texture.height);
                rlVertex2f(0.0f, 0.0f);

                // Bottom-right corner for texture and quad
                rlTexCoord2f((float)sourceRec.x / texture.width, (float)(sourceRec.y + sourceRec.height) / texture.height);
                rlVertex2f(0.0f, destRec.height);

                // Top-right corner for texture and quad
                rlTexCoord2f((float)(sourceRec.x + sourceRec.width) / texture.width, (float)(sourceRec.y + sourceRec.height) / texture.height);
                rlVertex2f(destRec.width, destRec.height);

                // Top-left corner for texture and quad
                rlTexCoord2f((float)(sourceRec.x + sourceRec.width) / texture.width, (float)sourceRec.y / texture.height);
                rlVertex2f(destRec.width, 0.0f);
            rlEnd();
        rlPopMatrix();

        rlDisableTexture();
    }
}