#include <helianthus.h></helianthus.h>

#include <math.h></math.h>

#define COUNT     16

#define SIZE      17

#define RADIUS    5

#define PRECISION 1e-5

double points[COUNT][2];

double *curPoint;

double curPointOffset[2];

int graphs[10];

double value(int ix)

  { return points[ ((ix + COUNT/2)%COUNT + COUNT)%COUNT ][1]; }

double nearest(double x)

  { return value(floor(x)); }

double linear(double x) {

  x -= 0.5;

  int ix = floor(x);

  x -= ix;

  return value(ix)*(1-x) + value(ix+1)*x;

}

double cubic(double x) {

  x -= 0.5;

  int ix = floor(x);

  x -= ix;

  double a = value(ix-1);

  double b = value(ix+0);

  double c = value(ix+1);

  double d = value(ix+2);

  return a*( -0.5*x*x*x +     x*x - 0.5*x )

			 + b*(  1.5*x*x*x - 2.5*x*x + 1.0   )

			 + c*( -1.5*x*x*x + 2.0*x*x + 0.5*x )

			 + d*(  0.5*x*x*x - 0.5*x*x         );

}

double bspline(double x) {

  x -= 0.5;

  int ix = floor(x);

  x -= ix;

  double a = value(ix-1);

  double b = value(ix+0);

  double c = value(ix+1);

  double d = value(ix+2);

  return a*(  -x*x*x + 3*x*x - 3*x + 1)/6

			 + b*( 3*x*x*x - 6*x*x + 4      )/6

			 + c*(-3*x*x*x + 3*x*x + 3*x + 1)/6

			 + d*(   x*x*x                  )/6;

}

void graph(double kx, double ky, double (*func)(double), unsigned int color) {

  saveState();

  strokeWidth(2);

  stroke(color);

  int hs = (int)ceil(SIZE*kx/2);

  for(int x = -hs; x <= hs; ++x)

    lineTo(x, func(x/kx)*ky);

  strokePath();

  restoreState();

}

void grid(double kx, double ky) {

  saveState();

  strokeWidth(1);

  stroke(colorByRGBA(0, 0, 1, 0.125));

  double hs = 0.5*SIZE;

  for(int step = 16; step; step >>= 1) {

    for(int i = 0; i <= SIZE/2; i += step) {

      line(-hs*kx,  i*ky, hs*kx,  i*ky);

      line(-hs*kx, -i*ky, hs*kx, -i*ky);

      line( i*kx, -hs*ky,  i*kx, hs*ky);

      line(-i*kx, -hs*ky, -i*kx, hs*ky);

    }

  }

  restoreState();

}

void randomize() {

  for(int i = 0; i < COUNT; ++i)

    points[i][1] = randomFloat()*SIZE - SIZE/2.0;

}

void zero() {

  for(int i = 0; i < COUNT; ++i)

    points[i][1] = 0;

}

void init() {

  for(int i = 0; i < COUNT; ++i)

    points[i][0] = i - COUNT/2 + 0.5;

  randomize();

}

void draw() {

  double w = windowGetWidth();

  double h = windowGetHeight();

  double kx = w/SIZE;

  double ky = h/SIZE;

  saveState();

  translate(w/2, h/2);

  scale(1, -1);

  if (keyWentDown("r")) { randomize(); curPoint = 0; }

  if (keyWentDown("z")) { zero(); curPoint = 0; }

  char key[] = "0";

  for(int i = 0; i < 10; ++i, ++*key)

    if (keyWentDown(key)) graphs[i] = !graphs[i];

  int m = mouseWentDown("left");

  double mx = mouseTransformedX();

  double my = mouseTransformedY();

  if (!mouseDown("left"))

    { m = FALSE; curPoint = 0; }

  if (curPoint) {

    //curPoint[0] = (mx + curPointOffset[0])/kx;

    curPoint[1] = (my + curPointOffset[1])/ky;

  }

  grid(kx, ky);

  if (graphs[0]) graph(kx, ky, nearest, colorByRGBA(0, 0, 0, 0.5));

  if (graphs[1]) graph(kx, ky, linear , colorByRGBA(0, 1, 0, 0.5));

  if (graphs[2]) graph(kx, ky, cubic  , colorByRGBA(0, 0, 1, 0.5));

  if (graphs[3]) graph(kx, ky, bspline, colorByRGBA(1, 0, 0, 0.5));

  strokeWidth(2);

  stroke(COLOR_BLUE);

  fill(COLOR_WHITE);

  for(int i = 0; i < COUNT; ++i) {

    double x = points[i][0]*kx, y = points[i][1]*ky;

    line(x, 0, x, y);

    circle(x, y, RADIUS);

    if (i == COUNT/2)

      circle(x, y, RADIUS + 1);

    double dx = x-mx, dy = y-my;

    if (m && dx*dx + dy*dy <= RADIUS*RADIUS) {

      curPoint = points[i];

      curPointOffset[0] = dx;

      curPointOffset[1] = dy;

    }

  }

  restoreState();

}

int main() {

  windowSetVariableFrameRate();

  windowSetResizable(TRUE);

  windowSetInit(&init);

  windowSetDraw(&draw);

  windowRun();

  return 0;

}