const TILE_SIZE = 15;

const dusa = new Dusa(`

​

#builtin INT_MINUS minus

#builtin INT_PLUS plus

​

size is ${DIMENSION}.

dim N :- size is N.

dim (minus N 1) :- dim N, N != 1.

​

delta 0 1.

delta 0 -1.

delta 1 0.

delta -1 0.

​

parent 1 1 is none.

parent X2 Y2 is { pair X1 Y1? } :-

   parent X1 Y1 is _,

   delta DX DY, 

   X2 == plus X1 DX, dim X2,

   Y2 == plus Y1 DY, dim Y2.

​

after N N is none :- size is N.

after X1 Y1 is (pair X2 Y2) :-

   after X2 Y2 is _,

   parent X2 Y2 is (pair X1 Y1).

​

`);

let iteration = 0;

const iterator = dusa.solutions;

​

function setup() {

  createCanvas(

    Math.max(DIMENSION * TILE_SIZE, 150), 

    DIMENSION * TILE_SIZE + 30

  );

  noLoop();

}

​

function touchStarted() {

  draw();

}

​

function draw() {

  const { value: solution } = iterator.next();

​

  erase();

  rect(0, 0, Math.max(DIMENSION * TILE_SIZE, 150), 30);

  noErase();

  fill("black");

  if (!solution && iteration == 0) {

    text("There are no solutions", 0, 20);

    return;

  }

  if (!solution) {

    text(`Solution ${iteration} out of ${iteration}`, 0, 20);

    return;    

  }

  iteration += 1;

  text(`Solution ${iteration} out of ?`, 0, 20);

  for (let col = 1; col <= DIMENSION; col++) {

    for (let row = 1; row <= DIMENSION; row++) {

      const x = (col-1) * TILE_SIZE;

      const y = (row-1) * TILE_SIZE + 30;

      if (solution.get('after', col, row)) {

        fill("lightgreen");

      } else {

        fill("white")

      }

      rect(x, y, TILE_SIZE, TILE_SIZE);

    }

  }

  for (const [col1, row1, value] of solution.lookup('parent')) {

    if (value.name !== 'pair') continue;

    const [col2, row2] = value.args;

    const x1 = (Number(col1)-0.5) * TILE_SIZE;

    const x2 = (Number(col2)-0.5) * TILE_SIZE;

    const y1 = (Number(row1)-0.5) * TILE_SIZE + 30;

    const y2 = (Number(row2)-0.5) * TILE_SIZE + 30;

    line(x1,y1,x2,y2)

  }

}