const TILE_SIZE = 25;

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.

​

movePos (pos X Y) (pos X' Y') :- 

  reachPos (pos X Y),

  delta DX DY, 

  plus X DX is X',

  plus Y DY is Y',

  dim X', dim Y'.

​

# waypoint 4 5.

waypoint is? (pos X Y) :- dim X, dim Y.

​

moveState (state X Y W) (state X' Y' W)

  :- movePos (pos X Y) (pos X' Y'),

     reachState (state X Y W).

​

moveState (state X Y false) (state X Y true)

  :- reachPos (pos X Y), waypoint is (pos X Y).

​

start (state 1 1 false).

​

parent S is none :- start S.

parent S is? { S' } :-

   parent S' is _,

   moveState S' S.

​

reachState S :- parent S is _.

reachPos (pos X Y) :- reachState (state X Y _).

​

goal (state size size true).

​

after S is done :- goal S.

after S' is S :-

   after S is _,

   parent S is S'.

`);

let iteration = 0;

const iterator = dusa.solve();

​

function setup() {

  createCanvas(

    Math.max(DIMENSION * TILE_SIZE, 150), 

    DIMENSION * TILE_SIZE + 30

  );

  noLoop();

}

​

function touchStarted() {

  draw();

}

​

function draw() {

  stroke(167)

  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);

  const waypoint = solution.get('waypoint').args;

  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;

      const fstate = solution.get('after', { name: 'state', args: [col, row, { name: 'false' }] })

      const tstate = solution.get('after', { name: 'state', args: [col, row, { name: 'true' }] })

      if (waypoint[0] === col && waypoint[1] === row) {

        fill("#fe96ca")

      } else if (tstate && fstate) {

        fill("#56d8a3"); // bright blue

      } else if (tstate) {

        fill("#09d3f2"); 

      } else if (fstate) {

        fill("#bdc653"); 

      } else {

        fill("white")

      }

      rect(x, y, TILE_SIZE, TILE_SIZE);

    }

  }

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

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

    const [col1, row1] = poskey.args;

    const [col2, row2] = value.args;

    // COMMENT OUT THIS LINE TO SHOW BOTH 'true' AND 'false' TREES OVERLAID

    if (value.args[2].name === 'false') continue;

    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;

    stroke(0)

    line(x1,y1,x2,y2)

  }

}