import { ChessPiece } from "./chess_piece.js";

import * as SQUARE from './square_methods.js';

export class Knight extends ChessPiece {

/**

* Pawn constructor

* @param {string} pieceID

* @param {string} location

* @param {string} image

*/

constructor(pieceID, location, image) {

super(pieceID, location, image);

}

/**

*

* @param {string} target the square we want to move to

* @param {Set<string>} occSet the set of squares which are occupied

* @returns true if we can move to the target

* @returns false otherwise

*/

canMove(target, occSet) {

if (super.canMove(target, occSet)) { //ask the parent class

return this.canMove2(target);//ask the knight's specific rules for movement

}

//else super says no, you cannot move there

return false;

}

/**

* helper function for the canMove function that can be unit tested since it doesn't use the DOM

* @param {string} target the square we want to move to

* @returns true if the knight is allowed to move there

* @returns false, with an error string otherwise

*/

canMove2(target){

const dxAbs = Math.abs(SQUARE.DeltaX(this.location, target));

const dyAbs = Math.abs(SQUARE.DeltaY(this.location, target));

if(dxAbs === 1){

if(dyAbs === 2){

return true;

}

this.setFeedback('For knight, if |DeltaX| === 1, then |DeltaY| must equal 2.');

return false;

}

if(dxAbs === 2){

if(dyAbs === 1){

return true;

}

this.setFeedback('For knight, if |DeltaX| === 2, then |DeltaY| must equal 1.');

return false;

}

this.setFeedback('A knight must move in an "L"-shaped pattern.');

return false;

}

}