<?php declare(strict_types=1);

/*
 * 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\Package\PackageInterface;
use Composer\Semver\CompilingMatcher;
use Composer\Semver\Constraint\Constraint;

/**
 * @author Nils Adermann <naderman@naderman.de>
 * @author Jordi Boggiano <j.boggiano@seld.be>
 */
class DefaultPolicy implements PolicyInterface
{
    /** @var bool */
    private $preferStable;
    /** @var bool */
    private $preferLowest;
    /** @var array<string, string>|null */
    private $preferredVersions;
    /** @var array<int, array<string, non-empty-list<int>>> */
    private $preferredPackageResultCachePerPool;
    /** @var array<int, array<string, int>> */
    private $sortingCachePerPool;

    /**
     * @param array<string, string>|null $preferredVersions Must be an array of package name => normalized version
     */
    public function __construct(bool $preferStable = false, bool $preferLowest = false, ?array $preferredVersions = null)
    {
        $this->preferStable = $preferStable;
        $this->preferLowest = $preferLowest;
        $this->preferredVersions = $preferredVersions;
    }

    /**
     * @param string $operator One of Constraint::STR_OP_*
     *
     * @phpstan-param Constraint::STR_OP_* $operator
     */
    public function versionCompare(PackageInterface $a, PackageInterface $b, string $operator): bool
    {
        if ($this->preferStable && ($stabA = $a->getStability()) !== ($stabB = $b->getStability())) {
            return BasePackage::STABILITIES[$stabA] < BasePackage::STABILITIES[$stabB];
        }

        // dev versions need to be compared as branches via matchSpecific's special treatment, the rest can be optimized with compiling matcher
        if (($a->isDev() && str_starts_with($a->getVersion(), 'dev-')) || ($b->isDev() && str_starts_with($b->getVersion(), 'dev-'))) {
            $constraint = new Constraint($operator, $b->getVersion());
            $version = new Constraint('==', $a->getVersion());

            return $constraint->matchSpecific($version, true);
        }

        return CompilingMatcher::match(new Constraint($operator, $b->getVersion()), Constraint::OP_EQ, $a->getVersion());
    }

    /**
     * @param  non-empty-list<int>  $literals
     * @return non-empty-list<int>
     */
    public function selectPreferredPackages(Pool $pool, array $literals, ?string $requiredPackage = null): array
    {
        sort($literals);
        $resultCacheKey = implode(',', $literals).$requiredPackage;
        $poolId = spl_object_id($pool);

        if (isset($this->preferredPackageResultCachePerPool[$poolId][$resultCacheKey])) {
            return $this->preferredPackageResultCachePerPool[$poolId][$resultCacheKey];
        }

        $packages = $this->groupLiteralsByName($pool, $literals);

        foreach ($packages as &$nameLiterals) {
            usort($nameLiterals, function ($a, $b) use ($pool, $requiredPackage, $poolId): int {
                $cacheKey = 'i'.$a.'.'.$b.$requiredPackage; // i prefix -> ignoreReplace = true

                if (isset($this->sortingCachePerPool[$poolId][$cacheKey])) {
                    return $this->sortingCachePerPool[$poolId][$cacheKey];
                }

                return $this->sortingCachePerPool[$poolId][$cacheKey] = $this->compareByPriority($pool, $pool->literalToPackage($a), $pool->literalToPackage($b), $requiredPackage, true);
            });
        }

        foreach ($packages as &$sortedLiterals) {
            $sortedLiterals = $this->pruneToBestVersion($pool, $sortedLiterals);
            $sortedLiterals = $this->pruneRemoteAliases($pool, $sortedLiterals);
        }

        $selected = array_merge(...array_values($packages));

        // now sort the result across all packages to respect replaces across packages
        usort($selected, function ($a, $b) use ($pool, $requiredPackage, $poolId): int {
            $cacheKey = $a.'.'.$b.$requiredPackage; // no i prefix -> ignoreReplace = false

            if (isset($this->sortingCachePerPool[$poolId][$cacheKey])) {
                return $this->sortingCachePerPool[$poolId][$cacheKey];
            }

            return $this->sortingCachePerPool[$poolId][$cacheKey] = $this->compareByPriority($pool, $pool->literalToPackage($a), $pool->literalToPackage($b), $requiredPackage);
        });

        return $this->preferredPackageResultCachePerPool[$poolId][$resultCacheKey] = $selected;
    }

    /**
     * @param  non-empty-list<int> $literals
     * @return non-empty-array<string, non-empty-list<int>>
     */
    protected function groupLiteralsByName(Pool $pool, array $literals): array
    {
        $packages = [];
        foreach ($literals as $literal) {
            $packageName = $pool->literalToPackage($literal)->getName();

            if (!isset($packages[$packageName])) {
                $packages[$packageName] = [];
            }
            $packages[$packageName][] = $literal;
        }

        return $packages;
    }

    /**
     * @protected
     */
    public function compareByPriority(Pool $pool, BasePackage $a, BasePackage $b, ?string $requiredPackage = null, bool $ignoreReplace = false): int
    {
        // prefer aliases to the original package
        if ($a->getName() === $b->getName()) {
            $aAliased = $a instanceof AliasPackage;
            $bAliased = $b instanceof AliasPackage;
            if ($aAliased && !$bAliased) {
                return -1; // use a
            }
            if (!$aAliased && $bAliased) {
                return 1; // use b
            }
        }

        if (!$ignoreReplace) {
            // return original, not replaced
            if ($this->replaces($a, $b)) {
                return 1; // use b
            }
            if ($this->replaces($b, $a)) {
                return -1; // use a
            }

            // for replacers not replacing each other, put a higher prio on replacing
            // packages with the same vendor as the required package
            if ($requiredPackage !== null && false !== ($pos = strpos($requiredPackage, '/'))) {
                $requiredVendor = substr($requiredPackage, 0, $pos);

                $aIsSameVendor = strpos($a->getName(), $requiredVendor) === 0;
                $bIsSameVendor = strpos($b->getName(), $requiredVendor) === 0;

                if ($bIsSameVendor !== $aIsSameVendor) {
                    return $aIsSameVendor ? -1 : 1;
                }
            }
        }

        // priority equal, sort by package id to make reproducible
        if ($a->id === $b->id) {
            return 0;
        }

        return ($a->id < $b->id) ? -1 : 1;
    }

    /**
     * Checks if source replaces a package with the same name as target.
     *
     * Replace constraints are ignored. This method should only be used for
     * prioritisation, not for actual constraint verification.
     */
    protected function replaces(BasePackage $source, BasePackage $target): bool
    {
        foreach ($source->getReplaces() as $link) {
            if ($link->getTarget() === $target->getName()
//                && (null === $link->getConstraint() ||
//                $link->getConstraint()->matches(new Constraint('==', $target->getVersion())))) {
            ) {
                return true;
            }
        }

        return false;
    }

    /**
     * @param  list<int> $literals
     * @return list<int>
     */
    protected function pruneToBestVersion(Pool $pool, array $literals): array
    {
        if ($this->preferredVersions !== null) {
            $name = $pool->literalToPackage($literals[0])->getName();
            if (isset($this->preferredVersions[$name])) {
                $preferredVersion = $this->preferredVersions[$name];
                $bestLiterals = [];
                foreach ($literals as $literal) {
                    if ($pool->literalToPackage($literal)->getVersion() === $preferredVersion) {
                        $bestLiterals[] = $literal;
                    }
                }
                if (\count($bestLiterals) > 0) {
                    return $bestLiterals;
                }
            }
        }

        $operator = $this->preferLowest ? '<' : '>';
        $bestLiterals = [$literals[0]];
        $bestPackage = $pool->literalToPackage($literals[0]);
        foreach ($literals as $i => $literal) {
            if (0 === $i) {
                continue;
            }

            $package = $pool->literalToPackage($literal);

            if ($this->versionCompare($package, $bestPackage, $operator)) {
                $bestPackage = $package;
                $bestLiterals = [$literal];
            } elseif ($this->versionCompare($package, $bestPackage, '==')) {
                $bestLiterals[] = $literal;
            }
        }

        return $bestLiterals;
    }

    /**
     * Assumes that locally aliased (in root package requires) packages take priority over branch-alias ones
     *
     * If no package is a local alias, nothing happens
     *
     * @param  list<int> $literals
     * @return list<int>
     */
    protected function pruneRemoteAliases(Pool $pool, array $literals): array
    {
        $hasLocalAlias = false;

        foreach ($literals as $literal) {
            $package = $pool->literalToPackage($literal);

            if ($package instanceof AliasPackage && $package->isRootPackageAlias()) {
                $hasLocalAlias = true;
                break;
            }
        }

        if (!$hasLocalAlias) {
            return $literals;
        }

        $selected = [];
        foreach ($literals as $literal) {
            $package = $pool->literalToPackage($literal);

            if ($package instanceof AliasPackage && $package->isRootPackageAlias()) {
                $selected[] = $literal;
            }
        }

        return $selected;
    }
}