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

#include <stdlib.h></stdlib.h>

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

#define SIZE 100

double matrix[3][2] = {

  { 5,  2 },

  { 5, -2 },

  { 0, -5 } };

double invMatrix[2][2] = {

  { 0.1 ,  0.1  },

  { 0.25, -0.25 } };

double grid[2][SIZE][SIZE];

int gridId = 0;

double simTm;

double calcX(double x, double y, double z)

  { return matrix[0][0]*x + matrix[1][0]*y + matrix[2][0]*z; }

double calcY(double x, double y, double z)

  { return matrix[0][1]*x + matrix[1][1]*y + matrix[2][1]*z; }

double calcBackX(double sx, double sy)

  { return invMatrix[0][0]*sx + invMatrix[1][0]*sy; }

double calcBackY(double sx, double sy)

  { return invMatrix[0][1]*sx + invMatrix[1][1]*sy; }

void drawBox(double x, double y, double z, double dx, double dy, double dz, unsigned int color) {

  saveState();

  double ch = colorGetHue(color);

  double cs = colorGetSaturation(color);

  double cv = colorGetValue(color);

  noStroke();

  fill(colorByHSV(ch, cs, cv*0.6));

  moveTo( calcX(x, y, z),

          calcY(x, y, z) );

  lineTo( calcX(x+dx, y, z),

          calcY(x+dx, y, z) );

  lineTo( calcX(x+dx, y, z+dz),

          calcY(x+dx, y, z+dz) );

  lineTo( calcX(x, y, z+dz),

          calcY(x, y, z+dz) );

  closePath();

  fill(colorByHSV(ch, cs, cv*0.8));

  moveTo( calcX(x+dx, y, z),

          calcY(x+dx, y, z) );

  lineTo( calcX(x+dx, y+dy, z),

          calcY(x+dx, y+dy, z) );

  lineTo( calcX(x+dx, y+dy, z+dz),

          calcY(x+dx, y+dy, z+dz) );

  lineTo( calcX(x+dx, y, z+dz),

          calcY(x+dx, y, z+dz) );

  closePath();

  fill(color);

  moveTo( calcX(x, y, z+dz),

          calcY(x, y, z+dz) );

  lineTo( calcX(x+dx, y, z+dz),

          calcY(x+dx, y, z+dz) );

  lineTo( calcX(x+dx, y+dy, z+dz),

          calcY(x+dx, y+dy, z+dz) );

  lineTo( calcX(x, y+dy, z+dz),

          calcY(x, y+dy, z+dz) );

  closePath();

  restoreState();

}

void setPoint(int i, int j, int size, double z) {

  for(int ii = -size; ii <= size; ++ii)

    for(int jj = -size; jj <= size; ++jj)

      if ( i + ii >= 0 && i + ii < SIZE

        && j + jj >= 0 && j + jj < SIZE

        && ii*ii + jj*jj <= size*(size + 1) )

          grid[0][i+ii][j+jj] = grid[1][i+ii][j+jj] = z;

}

void init() { }

void draw() {

  double w = windowGetWidth();

  double h = windowGetHeight();

  double tm = windowGetSeconds();

  saveState();

  translate(w/2, h/2);

  double smx = mouseTransformedX();

  double smy = mouseTransformedY();

  double mx = calcBackX(smx, smy);

  double my = calcBackY(smx, smy);

  if (keyWentDown("space"))

    setPoint(randomNumber(0, SIZE-1), randomNumber(0, SIZE-1), 2, (randomFloat() - 0.5)*10);

  double k = 1/sqrt(2);

  double dt = 0.01;

  if (fabs(simTm - tm) > 5) simTm = tm - dt/2;

  while(simTm < tm) {

    if (mouseDown("left") || mouseDown("right") || mouseDown("middle")) {

      int i = (int)floor(mx + SIZE*0.5);

      int j = (int)floor(my + SIZE*0.5);

      setPoint(i, j, 4, mouseDown("left") ? 20 : mouseDown("right") ? -20 : 0);

    }

    int prevId = gridId;

    gridId = 1 - gridId;

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

      for(int j = 0; j < SIZE; ++j) {

        double z = grid[prevId][i][j];

        double v = z - grid[gridId][i][j];

        double f = 0;

        double sum = 0;

        if (i > 0     ) { f += grid[prevId][i-1][j] - z; sum += 1; }

        if (i < SIZE-1) { f += grid[prevId][i+1][j] - z; sum += 1; }

        if (j > 0     ) { f += grid[prevId][i][j-1] - z; sum += 1; }

        if (j < SIZE-1) { f += grid[prevId][i][j+1] - z; sum += 1; }

        if (i > 0      && j > 0     ) { f += k*(grid[prevId][i-1][j-1] - z); sum += k; }

        if (i < SIZE-1 && j > 0     ) { f += k*(grid[prevId][i+1][j-1] - z); sum += k; }

        if (i > 0      && j < SIZE-1) { f += k*(grid[prevId][i-1][j+1] - z); sum += k; }

        if (i < SIZE-1 && j < SIZE-1) { f += k*(grid[prevId][i+1][j+1] - z); sum += k; }

        if (sum > 0) f /= sum;

        grid[gridId][i][j] = z + (v + 0.1*f)*0.99;

      }

    }

    simTm += dt;

  }

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

    for(int j = SIZE-1; j >= 0; --j)

      drawBox( i - SIZE*0.5 - 0.5,

               j - SIZE*0.5 - 0.5,

               -50,

               1, 1, 50 + grid[gridId][i][j],

               COLOR_AQUA );

  restoreState();

  saveState();

  noFill();

  text(10, 10, "try left and right mouse buttons");

  restoreState();

}

int main() {

  windowSetTitle("Water");

  windowSetVariableFrameRate();

  windowSetResizable(TRUE);

  windowSetInit(&init);

  windowSetDraw(&draw);

  windowRun();

  return 0;

}