dvdoug / BoxPacker

src/VolumePacker.php

<?php
/**
 * Box packing (3D bin packing, knapsack problem).
 *
 * @author Doug Wright
 */
declare(strict_types=1);

namespace DVDoug\BoxPacker;

use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;

use function array_map;
use function count;
use function max;
use function reset;
use function usort;

/**
 * Actual packer.
 */
class VolumePacker implements LoggerAwareInterface
{
    protected LoggerInterface $logger;

    protected ItemList $items;

    protected bool $singlePassMode = false;

    protected bool $packAcrossWidthOnly = false;

    private readonly LayerPacker $layerPacker;

    protected bool $beStrictAboutItemOrdering = false;

    private readonly bool $hasConstrainedItems;

    private readonly bool $hasNoRotationItems;

    public function __construct(protected Box $box, ItemList $items)
    {
        $this->items = clone $items;

        $this->logger = new NullLogger();

        $this->hasConstrainedItems = $items->hasConstrainedItems();

The property hasConstrainedItems is declared read-only in DVDoug\BoxPacker\VolumePacker.

        $this->hasNoRotationItems = $items->hasNoRotationItems();

The property hasNoRotationItems is declared read-only in DVDoug\BoxPacker\VolumePacker.

        $this->layerPacker = new LayerPacker($this->box);

The property layerPacker is declared read-only in DVDoug\BoxPacker\VolumePacker.

        $this->layerPacker->setLogger($this->logger);
    }

    /**
     * Sets a logger.
     */
    public function setLogger(LoggerInterface $logger): void
    {
        $this->logger = $logger;
        $this->layerPacker->setLogger($logger);
    }

    public function packAcrossWidthOnly(): void
    {
        $this->packAcrossWidthOnly = true;
    }

    public function beStrictAboutItemOrdering(bool $beStrict): void
    {
        $this->beStrictAboutItemOrdering = $beStrict;
        $this->layerPacker->beStrictAboutItemOrdering($beStrict);
    }

    /**
     * @internal
     */
    public function setSinglePassMode(bool $singlePassMode): void
    {
        $this->singlePassMode = $singlePassMode;
        if ($singlePassMode) {
            $this->packAcrossWidthOnly = true;
        }
        $this->layerPacker->setSinglePassMode($singlePassMode);
    }

    /**
     * Pack as many items as possible into specific given box.
     *
     * @return PackedBox packed box
     */
    public function pack(): PackedBox
    {
        $orientatedItemFactory = new OrientatedItemFactory($this->box);
        $orientatedItemFactory->setLogger($this->logger);
        $this->logger->debug("[EVALUATING BOX] {$this->box->getReference()}", ['box' => $this->box]);

        // Sometimes "space available" decisions depend on orientation of the box, so try both ways
        $rotationsToTest = [false];
        if (!$this->packAcrossWidthOnly && !$this->hasNoRotationItems) {
            $rotationsToTest[] = true;
        }

        // The orientation of the first item can have an outsized effect on the rest of the placement, so special-case
        // that and try everything

        $boxPermutations = [];
        foreach ($rotationsToTest as $rotation) {
            if ($rotation) {
                $boxWidth = $this->box->getInnerLength();
                $boxLength = $this->box->getInnerWidth();
            } else {
                $boxWidth = $this->box->getInnerWidth();
                $boxLength = $this->box->getInnerLength();
            }

            $specialFirstItemOrientations = [null];
            if (!$this->singlePassMode) {
                $specialFirstItemOrientations = $orientatedItemFactory->getPossibleOrientations($this->items->top(), null, $boxWidth, $boxLength, $this->box->getInnerDepth(), 0, 0, 0, new PackedItemList()) ?: [null];
            }

            foreach ($specialFirstItemOrientations as $firstItemOrientation) {
                $boxPermutation = $this->packRotation($boxWidth, $boxLength, $firstItemOrientation);
                if ($boxPermutation->items->count() === $this->items->count()) {
                    return $boxPermutation;
                }

                $boxPermutations[] = $boxPermutation;
            }
        }

        usort($boxPermutations, static fn (PackedBox $a, PackedBox $b) => $b->getVolumeUtilisation() <=> $a->getVolumeUtilisation());

        return reset($boxPermutations);
    }

    /**
     * Pack as many items as possible into specific given box.
     *
     * @return PackedBox packed box
     */
    private function packRotation(int $boxWidth, int $boxLength, ?OrientatedItem $firstItemOrientation): PackedBox
    {
        $this->logger->debug("[EVALUATING ROTATION] {$this->box->getReference()}", ['width' => $boxWidth, 'length' => $boxLength]);
        $this->layerPacker->setBoxIsRotated($this->box->getInnerWidth() !== $boxWidth);

        $layers = [];
        $items = clone $this->items;

        while ($items->count() > 0) {
            $layerStartDepth = self::getCurrentPackedDepth($layers);
            $packedItemList = $this->getPackedItemList($layers);

            if ($packedItemList->count() > 0) {
                $firstItemOrientation = null;
            }

            // do a preliminary layer pack to get the depth used
            $preliminaryItems = clone $items;
            $preliminaryLayer = $this->layerPacker->packLayer($preliminaryItems, clone $packedItemList, 0, 0, $layerStartDepth, $boxWidth, $boxLength, $this->box->getInnerDepth() - $layerStartDepth, 0, true, $firstItemOrientation);
            if (count($preliminaryLayer->getItems()) === 0) {
                break;
            }

            $preliminaryLayerDepth = $preliminaryLayer->getDepth();
            if ($preliminaryLayerDepth === $preliminaryLayer->getItems()[0]->depth) { // preliminary === final
                $layers[] = $preliminaryLayer;
                $items = $preliminaryItems;
            } else { // redo with now-known-depth so that we can stack to that height from the first item
                $layers[] = $this->layerPacker->packLayer($items, $packedItemList, 0, 0, $layerStartDepth, $boxWidth, $boxLength, $this->box->getInnerDepth() - $layerStartDepth, $preliminaryLayerDepth, true, $firstItemOrientation);
            }
        }

        if (!$this->singlePassMode && $layers) {
            $layers = $this->stabiliseLayers($layers);

            // having packed layers, there may be tall, narrow gaps at the ends that can be utilised
            $maxLayerWidth = max(array_map(static fn (PackedLayer $layer) => $layer->getEndX(), $layers));
            $layers[] = $this->layerPacker->packLayer($items, $this->getPackedItemList($layers), $maxLayerWidth, 0, 0, $boxWidth, $boxLength, $this->box->getInnerDepth(), $this->box->getInnerDepth(), false, null);

            $maxLayerLength = max(array_map(static fn (PackedLayer $layer) => $layer->getEndY(), $layers));
            $layers[] = $this->layerPacker->packLayer($items, $this->getPackedItemList($layers), 0, $maxLayerLength, 0, $boxWidth, $boxLength, $this->box->getInnerDepth(), $this->box->getInnerDepth(), false, null);
        }

        $layers = $this->correctLayerRotation($layers, $boxWidth);

        return new PackedBox($this->box, $this->getPackedItemList($layers));
    }

    /**
     * During packing, it is quite possible that layers have been created that aren't physically stable
     * i.e. they overhang the ones below.
     *
     * This function reorders them so that the ones with the greatest surface area are placed at the bottom
     *
     * @param  PackedLayer[] $oldLayers
     * @return PackedLayer[]
     */
    private function stabiliseLayers(array $oldLayers): array
    {
        if ($this->hasConstrainedItems || $this->beStrictAboutItemOrdering) { // constraints include position, so cannot change
            return $oldLayers;
        }

        $stabiliser = new LayerStabiliser();

        return $stabiliser->stabilise($oldLayers);
    }

    /**
     * Swap back width/length of the packed items to match orientation of the box if needed.
     *
     * @param PackedLayer[] $oldLayers
     *
     * @return PackedLayer[]
     */
    private function correctLayerRotation(array $oldLayers, int $boxWidth): array
    {
        if ($this->box->getInnerWidth() === $boxWidth) {
            return $oldLayers;
        }

        $newLayers = [];
        foreach ($oldLayers as $originalLayer) {
            $newLayer = new PackedLayer();
            foreach ($originalLayer->getItems() as $item) {
                $packedItem = new PackedItem($item->item, $item->y, $item->x, $item->z, $item->length, $item->width, $item->depth);
                $newLayer->insert($packedItem);
            }
            $newLayers[] = $newLayer;
        }

        return $newLayers;
    }

    /**
     * Generate a single list of items packed.
     * @param PackedLayer[] $layers
     */
    private function getPackedItemList(array $layers): PackedItemList
    {
        $packedItemList = new PackedItemList();
        foreach ($layers as $layer) {
            foreach ($layer->getItems() as $packedItem) {
                $packedItemList->insert($packedItem);
            }
        }

        return $packedItemList;
    }

    /**
     * Return the current packed depth.
     *
     * @param PackedLayer[] $layers
     */
    private static function getCurrentPackedDepth(array $layers): int
    {
        $depth = 0;
        foreach ($layers as $layer) {
            $depth += $layer->getDepth();
        }

        return $depth;
    }
}