move-turtle-around.js

<?php
// noinspection FallThroughInSwitchStatementJS

/*
  - We have a NxN grid
  - Turtle initial point is bottom left (1,1) looking north
  - Turtle movement is one of: Forward one step (F), Turn left (L), Turn right (R).
  - Grid has 4 directions: E/W/S/N.
   _______________
  |   |   |   |   |
  |___|___|___|___|
  |   |   |   |   |
  |___|___|___|___|
  |   |   |   |   |
  |___|___|___|___|
  | ^ |   |   |   |
  |_O_|___|___|___|

   W = LEFT
   E = RIGHT
   N = UP
   S = DOWN

  - Implement `moveTurtleAround(movement)` - Input is movement string: "FFFRRFLF". Output is point and direction: (2,3,E)


Examples:

input: board size is 5, movement string: "FFFRRFLF"
output: (2,3,E)

input: board size is 10, movement string: "FLLFLL"
output: (1,1,N)
 */

/*
 * Instructions:
 * If you need more classes, simply define them inline.
 */
function getNextPosition( currentPosition, newDirection ) {
	let result;

	switch ( currentPosition ) {
		case 'UP':
		case 'DOWN': {
			switch ( newDirection ) {
				case 'L':
					result = 'LEFT';
					break;

				case 'R':
					result = 'RIGHT';
					break;
			}

			break;
		}

		case 'RIGHT':
		case 'LEFT': {
			result = 'R' === newDirection ? 'DOWN' : 'UP';

			break;
		}

		default:
			throw new Error( `Invalid currentPosition: ${currentPosition}` );
	}

	return result;
}

function getForwardInstructions( position ) {
	const result = { orientation: '', op: undefined };

	switch ( position ) {
		case 'UP':
			result.op = '+';
		case 'DOWN':
			result.op ??= '-';
			result.orientation = 'y';

			break;

		case 'RIGHT':
			result.op = '-';
		case 'LEFT':
			result.op ??= '+';
			result.orientation = 'x';

			break;
		default:
			throw new Error( `Invalid current position: ${position}` );
	}

	return result;
}

function moveTurtleAround( movement ) {
	const result = {
		x: 1,
		y: 1,
		pos: 'UP',
	};

	movement.split( '' ).forEach( direction => {
		if ( [ 'L', 'R' ].includes( direction ) ) {
			return result.pos = getNextPosition( result.pos, direction );
		}

		const { orientation, op } = getForwardInstructions( result.pos, direction );

		switch ( op ) {
			case '+':
				result[ orientation ] += 1;
				break;

			case '-':
				result[ orientation ] -= 1;
				break;

			default:
				new Error( `Invalid math operation ${ op }`)
		}
	} );

	return result;
}

console.log( 'FLLFLL', moveTurtleAround( 'FLLFLL' ) );
console.log( 'FFFRRFLF', moveTurtleAround( 'FFFRRFLF' ) );