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<?php |
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/** |
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* (c) 2018 Douglas Reith. |
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* |
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* For the full copyright and license information, please view the LICENSE |
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* file that was distributed with this source code. |
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*/ |
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declare(strict_types=1); |
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namespace Reith\ToyRobot\Domain\Robot; |
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use Assert\Assertion; |
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use MathPHP\LinearAlgebra\MatrixFactory; |
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use MathPHP\LinearAlgebra\Vector; |
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/** |
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* Manage robot direction. |
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* |
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* Matrix multiplication gives us the new direction. |
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*/ |
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class Direction |
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{ |
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// Counter clockwise |
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private const ROTATE_LEFT_MATRIX = [ |
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[0, -1], |
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[1, 0] |
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]; |
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// Clockwise |
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private const ROTATE_RIGHT_MATRIX = [ |
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[0, 1], |
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[-1, 0] |
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]; |
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private const CHAR_VECTOR_MAPPING = [ |
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'N' => [0, 1], |
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'E' => [1, 0], |
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'S' => [0, -1], |
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'W' => [-1, 0], |
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]; |
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private $leftTransform; |
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private $rightTransform; |
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private $direction; |
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/** |
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* @param string|null $startingDirection |
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*/ |
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public function __construct(?string $startingDirection = 'E') |
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{ |
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// Normalise |
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$startingDirection = strtoupper(trim($startingDirection)); |
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Assertion::choice($startingDirection, ['N', 'S', 'E', 'W']); |
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$this->setDirectionFromString($startingDirection); |
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$this->leftTransform = MatrixFactory::create(self::ROTATE_LEFT_MATRIX); |
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$this->rightTransform = MatrixFactory::create(self::ROTATE_RIGHT_MATRIX); |
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} |
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/** |
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* @param string $direction |
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* @return Direction |
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*/ |
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private function setDirectionFromString(string $direction): Direction |
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{ |
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$this->direction = new Vector( |
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self::CHAR_VECTOR_MAPPING[$direction] |
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); |
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return $this; |
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} |
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2 |
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public function northward(): Vector |
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{ |
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return $this->setDirectionFromString('N')->getDirectionAsVector(); |
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} |
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1 |
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public function eastward(): Vector |
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{ |
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return $this->setDirectionFromString('E')->getDirectionAsVector(); |
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} |
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public function westward(): Vector |
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{ |
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return $this->setDirectionFromString('W')->getDirectionAsVector(); |
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} |
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public function southward(): Vector |
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{ |
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return $this->setDirectionFromString('S')->getDirectionAsVector(); |
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} |
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/** |
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* @return Direction |
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*/ |
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1 |
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public function rotateLeft(): Direction |
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{ |
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1 |
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$this->direction = $this->leftTransform->vectorMultiply( |
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1 |
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$this->direction |
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); |
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return $this; |
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} |
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/** |
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* @return Direction |
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*/ |
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public function rotateRight() |
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{ |
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1 |
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$this->direction = $this->rightTransform->vectorMultiply( |
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1 |
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$this->direction |
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); |
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return $this; |
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} |
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/** |
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* @return Vector |
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*/ |
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public function getDirectionAsVector(): Vector |
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{ |
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return $this->direction; |
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} |
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/** |
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* @return string |
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* @throws \LogicException |
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*/ |
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public function getDirectionAsString(): string |
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{ |
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foreach (self::CHAR_VECTOR_MAPPING as $char => $coords) { |
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// Array equality === same key, value pairs in the same |
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// order (no type casting) |
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if ($coords === $this->direction->getVector()) { |
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return $char; |
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} |
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} |
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throw new \LogicException( |
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'Unable to find the direction char from the vector' |
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); |
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} |
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} |
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reithbot /
toyrobot-php
