composer/src/Composer/DependencyResolver/PoolOptimizer.php

<?php

/*
 * This file is part of Composer.
 *
 * (c) Nils Adermann <naderman@naderman.de>
 *     Jordi Boggiano <j.boggiano@seld.be>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Composer\DependencyResolver;

use Composer\Package\AliasPackage;
use Composer\Package\BasePackage;
use Composer\Semver\CompilingMatcher;
use Composer\Semver\Constraint\ConstraintInterface;
use Composer\Semver\Constraint\Constraint;
use Composer\Semver\Constraint\MultiConstraint;
use Composer\Semver\Intervals;

/**
 * Optimizes a given pool
 *
 * @author Yanick Witschi <yanick.witschi@terminal42.ch>
 */
class PoolOptimizer
{
    /**
     * @var PolicyInterface
     */
    private $policy;

    /**
     * @var array<int, true>
     */
    private $irremovablePackages = array();

    /**
     * @var array<string, array<string, ConstraintInterface>>
     */
    private $requireConstraintsPerPackage = array();

    /**
     * @var array<string, array<string, ConstraintInterface>>
     */
    private $conflictConstraintsPerPackage = array();

    /**
     * @var array<int, true>
     */
    private $packagesToRemove = array();

    /**
     * @var array<int, BasePackage[]>
     */
    private $aliasesPerPackage = array();

    public function __construct(PolicyInterface $policy)
    {
        $this->policy = $policy;
    }

    /**
     * @return Pool
     */
    public function optimize(Request $request, Pool $pool)
    {
        $this->prepare($request, $pool);

        $optimizedPool = $this->optimizeByIdenticalDependencies($pool);

        // No need to run this recursively at the moment
        // because the current optimizations cannot provide
        // even more gains when ran again. Might change
        // in the future with additional optimizations.

        $this->irremovablePackages = array();
        $this->requireConstraintsPerPackage = array();
        $this->conflictConstraintsPerPackage = array();
        $this->packagesToRemove = array();
        $this->aliasesPerPackage = array();

        return $optimizedPool;
    }

    /**
     * @return void
     */
    private function prepare(Request $request, Pool $pool)
    {
        $irremovablePackageConstraintGroups = array();

        // Mark fixed or locked packages as irremovable
        foreach ($request->getFixedOrLockedPackages() as $package) {
            $irremovablePackageConstraintGroups[$package->getName()][] = new Constraint('==', $package->getVersion());
        }

        // Extract requested package requirements
        foreach ($request->getRequires() as $require => $constraint) {
            $constraint = Intervals::compactConstraint($constraint);
            $this->requireConstraintsPerPackage[$require][(string) $constraint] = $constraint;
        }

        // First pass over all packages to extract information and mark package constraints irremovable
        foreach ($pool->getPackages() as $package) {
            // Extract package requirements
            foreach ($package->getRequires() as $link) {
                $constraint = Intervals::compactConstraint($link->getConstraint());
                $this->requireConstraintsPerPackage[$link->getTarget()][(string) $constraint] = $constraint;
            }
            // Extract package conflicts
            foreach ($package->getConflicts() as $link) {
                $constraint = Intervals::compactConstraint($link->getConstraint());
                $this->conflictConstraintsPerPackage[$link->getTarget()][(string) $constraint] = $constraint;
            }

            // Keep track of alias packages for every package so if either the alias or aliased is kept
            // we keep the others as they are a unit of packages really
            if ($package instanceof AliasPackage) {
                $this->aliasesPerPackage[$package->getAliasOf()->id][] = $package;
            }
        }

        $irremovablePackageConstraints = array();
        foreach ($irremovablePackageConstraintGroups as $packageName => $constraints) {
            $irremovablePackageConstraints[$packageName] = 1 === \count($constraints) ? $constraints[0] : new MultiConstraint($constraints, false);
        }
        unset($irremovablePackageConstraintGroups);

        // Mark the packages as irremovable based on the constraints
        foreach ($pool->getPackages() as $package) {
            if (!isset($irremovablePackageConstraints[$package->getName()])) {
                continue;
            }

            if (CompilingMatcher::match($irremovablePackageConstraints[$package->getName()], Constraint::OP_EQ, $package->getVersion())) {
                $this->markPackageIrremovable($package);
            }
        }
    }

    /**
     * @return void
     */
    private function markPackageIrremovable(BasePackage $package)
    {
        $this->irremovablePackages[$package->id] = true;
        if ($package instanceof AliasPackage) {
            // recursing here so aliasesPerPackage for the aliasOf can be checked
            // and all its aliases marked as irremovable as well
            $this->markPackageIrremovable($package->getAliasOf());
        }
        if (isset($this->aliasesPerPackage[$package->id])) {
            foreach ($this->aliasesPerPackage[$package->id] as $aliasPackage) {
                $this->irremovablePackages[$aliasPackage->id] = true;
            }
        }
    }

    /**
     * @return Pool Optimized pool
     */
    private function applyRemovalsToPool(Pool $pool)
    {
        $packages = array();
        foreach ($pool->getPackages() as $package) {
            if (!isset($this->packagesToRemove[$package->id])) {
                $packages[] = $package;
            }
        }

        $optimizedPool = new Pool($packages, $pool->getUnacceptableFixedOrLockedPackages());

        // Reset package removals
        $this->packagesToRemove = array();

        return $optimizedPool;
    }

    /**
     * @return Pool
     */
    private function optimizeByIdenticalDependencies(Pool $pool)
    {
        $identicalDefinitionPerPackage = array();
        $packageIdsToRemove = array();

        foreach ($pool->getPackages() as $package) {

            // If that package was already marked irremovable, we can skip
            // the entire process for it
            if (isset($this->irremovablePackages[$package->id])) {
                continue;
            }

            $packageIdsToRemove[$package->id] = true;

            $dependencyHash = $this->calculateDependencyHash($package);

            foreach ($package->getNames(false) as $packageName) {

                if (!isset($this->requireConstraintsPerPackage[$packageName])) {
                    continue;
                }

                foreach ($this->requireConstraintsPerPackage[$packageName] as $requireConstraint) {

                    $groupHashParts = array();

                    if (CompilingMatcher::match($requireConstraint, Constraint::OP_EQ, $package->getVersion())) {
                        $groupHashParts[] = 'require:' . (string) $requireConstraint;
                    }

                    if ($package->getReplaces()) {
                        foreach ($package->getReplaces() as $link) {
                            if (CompilingMatcher::match($link->getConstraint(), Constraint::OP_EQ, $package->getVersion())) {
                                // Use the same hash part as the regular require hash because that's what the replacement does
                                $groupHashParts[] = 'require:' . (string) $link->getConstraint();
                            }
                        }
                    }

                    if (isset($this->conflictConstraintsPerPackage[$packageName])) {
                        foreach ($this->conflictConstraintsPerPackage[$packageName] as $conflictConstraint) {
                            if (CompilingMatcher::match($conflictConstraint, Constraint::OP_EQ, $package->getVersion())) {
                                $groupHashParts[] = 'conflict:' . (string) $conflictConstraint;
                            }
                        }
                    }

                    if (!$groupHashParts) {
                        continue;
                    }

                    $identicalDefinitionPerPackage[$packageName][implode('', $groupHashParts)][$dependencyHash][] = $package;
                }
            }
        }

        $keepPackage = function (BasePackage $package, $aliasesPerPackage) use (&$packageIdsToRemove, &$keepPackage) {
            unset($packageIdsToRemove[$package->id]);
            if ($package instanceof AliasPackage) {
                // recursing here so aliasesPerPackage for the aliasOf can be checked
                // and all its aliases marked to be kept as well
                $keepPackage($package->getAliasOf(), $aliasesPerPackage);
            }
            if (isset($aliasesPerPackage[$package->id])) {
                foreach ($aliasesPerPackage[$package->id] as $aliasPackage) {
                    unset($packageIdsToRemove[$aliasPackage->id]);
                }
            }
        };

        foreach ($identicalDefinitionPerPackage as $package => $constraintGroups) {
            foreach ($constraintGroups as $constraintGroup) {
                foreach ($constraintGroup as $hash => $packages) {

                    // Only one package in this constraint group has the same requirements, we're not allowed to remove that package
                    if (1 === \count($packages)) {
                        $keepPackage($packages[0], $this->aliasesPerPackage);
                        continue;
                    }

                    // Otherwise we find out which one is the preferred package in this constraint group which is
                    // then not allowed to be removed either
                    $literals = array();

                    foreach ($packages as $package) {
                        $literals[] = $package->id;
                    }

                    foreach ($this->policy->selectPreferredPackages($pool, $literals) as $preferredLiteral) {
                        $keepPackage($pool->literalToPackage($preferredLiteral), $this->aliasesPerPackage);
                    }
                }
            }
        }

        foreach ($packageIdsToRemove as $id => $dummy) {
            $this->markPackageForRemoval($id);
        }

        // Apply removals
        return $this->applyRemovalsToPool($pool);
    }

    /**
     * @return string
     */
    private function calculateDependencyHash(BasePackage $package)
    {
        $hash = '';

        $hashRelevantLinks = array(
            'requires' => $package->getRequires(),
            'conflicts' => $package->getConflicts(),
            'replaces' => $package->getReplaces(),
            'provides' => $package->getProvides()
        );

        foreach ($hashRelevantLinks as $key => $links) {
            if (0 === \count($links)) {
                continue;
            }

            // start new hash section
            $hash .= $key . ':';

            $subhash = array();

            foreach ($links as $link) {
                // To get the best dependency hash matches we should use Intervals::compactConstraint() here.
                // However, the majority of projects are going to specify their constraints already pretty
                // much in the best variant possible. In other words, we'd be wasting time here and it would actually hurt
                // performance more than the additional few packages that could be filtered out would benefit the process.
                $subhash[$link->getTarget()] = (string) $link->getConstraint();
            }

            // Sort for best result
            ksort($subhash);

            foreach ($subhash as $target => $constraint) {
                $hash .= $target . '@' . $constraint;
            }
        }

        return $hash;
    }

    /**
     * @param int $id
     * @return void
     */
    private function markPackageForRemoval($id)
    {
        // We are not allowed to remove packages if they have been marked as irremovable
        if (isset($this->irremovablePackages[$id])) {
            throw new \LogicException('Attempted removing a package which was previously marked irremovable');
        }

        $this->packagesToRemove[$id] = true;
    }
}