#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>

#include "SDL.h"
#include "SDL_image.h"
#include "SDL_opengl.h"

SDL_Surface *screen;

const unsigned int width = 640, height = 480;


void initGl()
{
#if 0
    glViewport(0, 0, screen->w, screen->h);

    glMatrixMode(GL_PROJECTION);

    glOrtho(0.0, (GLdouble)screen->w,
            (GLdouble)screen->h, 0.0,
            0.0, 1.0);

#endif
    glClearColor(0.0, 0.0, 0.0, 0.0);
}


class Drawer
{
private:
    float fMinX;
    float fMinY;
    float fHeight;
    float fWidth;
    float fDistX;
    float fDistY;

    int iScreenHeight;
    int iScreenWidth;

    int iOriginX;
    int iOriginY;

public:
    //Constructor
    Drawer(float fScreeMaxX,float fScreenMaxY,float fScreenMinX,float fScreenMinY,
            int iScreenX,int iScreenY,int iCenterX,int iCenterY);

    //Formulas
    inline float Wrangle(float distance,float fT);

    //Drawers
    void Draw(float iT);
};

Drawer::Drawer(float fScreenMaxX,float fScreenMaxY,float fScreenMinX,float fScreenMinY,int iScreenX,
                           int iScreenY,int iCenterX,int iCenterY)
{
    fMinX = fScreenMinX;
    fMinY = fScreenMinY;
    fHeight = fScreenMaxY - fScreenMinY;
    fWidth = fScreenMaxX - fScreenMinX;
    fDistX = fWidth/iScreenX;
    fDistY = fHeight/iScreenY;

    iScreenHeight = iScreenX;
    iScreenWidth = iScreenY;
    iOriginX = iCenterX;
    iOriginY = iCenterX;
}
 
static const float fRadian = 3.14159265f / 180.0f;

float Drawer::Wrangle(float fDistance, float fT)
{
    fT *= 5*fRadian;

    float fCircular = cos( fDistance-fT)*0.025;
    float fDamp = fDistance*0.025;
    if(fDamp < 0.5f)
        fDamp = 0.5f;

    //float fWave = cos(fX+fT)/40.0f;
    return fCircular/(fDamp);
}


void Drawer::Draw(float iT)
{
    int i = 0;
    glColor3f(0.0f,0.0f,1.0f);

    float iScale = 64./iScreenWidth;
    float jScale = 64./iScreenHeight;

    static std::vector<float> distances;
    if (distances.empty()) {
        distances.resize(iScreenHeight * iScreenWidth);

        for (int i = 0; i < iScreenHeight; ++i) {
            for (int j = 0; j < iScreenWidth; ++j) {
                float fX = (i*iScale - iOriginX) * 100 * fRadian;
                float fY = (j*jScale - iOriginY) * 100 * fRadian;

                distances[i * iScreenWidth + j] = sqrt(fX*fX + fY*fY);
            }
        }
    }

    static std::vector<float> grid(iScreenHeight * iScreenWidth);
    for (int i = 0; i < iScreenHeight; ++i)
        for (int j = 0; j < iScreenWidth; ++j)
            grid[i * iScreenWidth + j] = Wrangle(distances[i * iScreenWidth + j], iT);

    static std::vector<float> vertices((iScreenHeight - 1) * iScreenWidth * 6);
    static std::vector<float> colors((iScreenHeight - 1) * iScreenWidth * 6);

#if 1
    while(i < iScreenHeight - 1)
    {
        float fResult[2];
        int j = 0;
        while(j < iScreenWidth) {
            fResult[0] = grid[(i + 1) * iScreenWidth + j];
            fResult[1] = grid[i * iScreenWidth + j];

            int index = (i*iScreenWidth+j)*6;

            colors[index + 2] = 0.75 - fResult[0]*10;
            colors[index + 5] = 0.75 - fResult[1]*10;

            float fX = fMinX + i*fDistX;
            float fY = fMinY + j*fDistY;

            vertices[index] = fX + fDistX;
            vertices[index+1] = fY;
            vertices[index+2] = fResult[0];
            vertices[index+3] = fX;
            vertices[index+4] = fY;
            vertices[index+5] = fResult[1];

            j++;
        }

        i++;
    }
#endif

    glVertexPointer(3, GL_FLOAT, 0, &vertices[0]);
    glColorPointer(3, GL_FLOAT, 0, &colors[0]);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);

    for (int i = 0; i < iScreenHeight-1; ++i)
        glDrawArrays(GL_TRIANGLE_STRIP, iScreenWidth*i*2, iScreenWidth*2);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
}

void render(float time, Drawer &Simple)
{
    if (SDL_MUSTLOCK(screen))
        if (SDL_LockSurface(screen) < 0) 
            return;

    glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glPushMatrix();
    glRotatef(45.0f, 1.0f, 1.0f, 0.0f);

    Simple.Draw(time*100);

    glPopMatrix();

    if (SDL_MUSTLOCK(screen))
        SDL_UnlockSurface(screen);

    //SDL_UpdateRect(screen, 0, 0, width, height);

    SDL_GL_SwapBuffers();
}

int main(int argc, char *argv[])
{
    if (SDL_Init(SDL_INIT_VIDEO) < 0)
        std::exit(1);

    atexit(SDL_Quit);

    SDL_GL_SetAttribute(SDL_GL_RED_SIZE,     8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE,   8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE,    8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE,   8);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE,  16);

    screen = SDL_SetVideoMode(width, height, 0, SDL_OPENGL);

    if (!screen)
        std::exit(1);

    initGl();

    unsigned int lastTime = SDL_GetTicks();

    float accumulatedSeconds = 0;

    int frames = 0;
    bool done = false;

    Drawer Simple(1.0f,1.0f,-1.0f,-1.0f,256,256,16,16);

    while (!done) {
        unsigned int currentTime = SDL_GetTicks();

        while (currentTime == lastTime)
            currentTime = SDL_GetTicks();

        float seconds = (currentTime - lastTime) * 0.001f;

        accumulatedSeconds += seconds;
        render(accumulatedSeconds, Simple);

        lastTime = currentTime;

        ++frames;

        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
                case SDL_KEYDOWN:
                    if (event.key.keysym.sym == SDLK_PLUS)
                        ;
                    else if (event.key.keysym.sym == SDLK_MINUS)
                        ;
                    break;
                case SDL_KEYUP:
                    if (event.key.keysym.sym == SDLK_ESCAPE)
                        done = true;
                    break;
                case SDL_MOUSEBUTTONUP:
                    break;
                case SDL_MOUSEBUTTONDOWN:
                    break;
                case SDL_MOUSEMOTION:
                    break;
                case SDL_QUIT:
                    done = true;
                    break;
            }
        }
    }

    printf("FPS: %f\n", frames / accumulatedSeconds);

    return 0;
}