<?php

declare(strict_types=1);

namespace App\Framework\Database;

use App\Framework\Database\Metadata\EntityMetadata;
use App\Framework\Database\Metadata\MetadataRegistry;
use App\Framework\Database\Metadata\PropertyMetadata;

final readonly class BatchRelationLoader
{
    public function __construct(
        private DatabaseManager $databaseManager,
        private MetadataRegistry $metadataRegistry,
        private IdentityMap $identityMap,
        private HydratorInterface $hydrator,
        private TypeResolver $typeResolver
    ) {
    }

    /**
     * Preload a specific relation for multiple entities in batches
     *
     * @param array<object> $entities
     * @param string $relationName
     */
    public function preloadRelation(array $entities, string $relationName): void
    {
        if (empty($entities)) {
            return;
        }

        $entityClass = get_class($entities[0]);
        $metadata = $this->metadataRegistry->getMetadata($entityClass);
        $relationMetadata = $this->getRelationMetadata($metadata, $relationName);

        if ($relationMetadata === null) {
            return; // Relation not found
        }

        match ($relationMetadata->relationType) {
            'hasMany' => $this->preloadHasMany($entities, $relationMetadata),
            'belongsTo' => $this->preloadBelongsTo($entities, $relationMetadata),
            'one-to-one' => $this->preloadOneToOne($entities, $relationMetadata),
            default => null
        };
    }

    /**
     * Preload hasMany relations (1:N)
     * Example: Post -> Comments
     */
    private function preloadHasMany(array $entities, PropertyMetadata $relationMetadata): void
    {
        // Collect all local keys (e.g., post IDs)
        $localKeys = array_filter(array_map(
            fn ($entity) => $this->getLocalKey($entity, $relationMetadata),
            $entities
        ));

        if (empty($localKeys)) {
            return;
        }

        // Load all related entities in one query
        // WHERE foreign_key IN (1, 2, 3, ...)
        $allRelations = $this->findByQuery(
            $relationMetadata->relationTargetClass,
            [$relationMetadata->relationForeignKey => $localKeys]
        );

        // Group relations by foreign key
        $groupedRelations = $this->groupByForeignKey($allRelations, $relationMetadata->relationForeignKey);

        // Set relations on entities
        foreach ($entities as $entity) {
            $localKey = $this->getLocalKey($entity, $relationMetadata);
            $keyString = $this->convertKeyForArray($localKey);
            $relations = $groupedRelations[$keyString] ?? [];
            $this->setRelationOnEntity($entity, $relationMetadata->name, $relations);
        }
    }

    /**
     * Preload belongsTo relations (N:1)
     * Example: Comment -> Post
     */
    private function preloadBelongsTo(array $entities, PropertyMetadata $relationMetadata): void
    {
        // Collect all foreign keys (e.g., post IDs from comments)
        $foreignKeys = array_filter(array_unique(array_map(
            fn ($entity) => $this->getForeignKey($entity, $relationMetadata),
            $entities
        )));

        if (empty($foreignKeys)) {
            return;
        }

        // Load all related entities in one query
        // WHERE id IN (1, 2, 3, ...)
        $allRelations = $this->findByQuery(
            $relationMetadata->relationTargetClass,
            ['id' => $foreignKeys] // Assuming 'id' is the primary key
        );

        // Index by primary key
        $indexedRelations = $this->indexByPrimaryKey($allRelations);

        // Set relations on entities
        foreach ($entities as $entity) {
            $foreignKey = $this->getForeignKey($entity, $relationMetadata);
            $keyString = $this->convertKeyForArray($foreignKey);
            $relation = $indexedRelations[$keyString] ?? null;
            $this->setRelationOnEntity($entity, $relationMetadata->name, $relation);
        }
    }

    /**
     * Preload one-to-one relations
     * Example: User -> Profile
     */
    private function preloadOneToOne(array $entities, PropertyMetadata $relationMetadata): void
    {
        // Similar to belongsTo but expecting single result
        $localKeys = array_filter(array_map(
            fn ($entity) => $this->getLocalKey($entity, $relationMetadata),
            $entities
        ));

        if (empty($localKeys)) {
            return;
        }

        $allRelations = $this->findByQuery(
            $relationMetadata->relationTargetClass,
            [$relationMetadata->relationForeignKey => $localKeys]
        );

        // Group by foreign key but expect only one result per key
        $groupedRelations = $this->groupByForeignKey($allRelations, $relationMetadata->relationForeignKey);

        foreach ($entities as $entity) {
            $localKey = $this->getLocalKey($entity, $relationMetadata);
            $keyString = $this->convertKeyForArray($localKey);
            $relation = $groupedRelations[$keyString][0] ?? null; // Take first (should be only one)
            $this->setRelationOnEntity($entity, $relationMetadata->name, $relation);
        }
    }

    private function getRelationMetadata(EntityMetadata $metadata, string $relationName): ?PropertyMetadata
    {
        foreach ($metadata->properties as $property) {
            if ($property->name === $relationName && $property->isRelation) {
                return $property;
            }
        }

        return null;
    }

    private function getLocalKey(object $entity, PropertyMetadata $relationMetadata): mixed
    {
        return $this->getPropertyValue($entity, $relationMetadata->relationLocalKey);
    }

    private function getForeignKey(object $entity, PropertyMetadata $relationMetadata): mixed
    {
        return $this->getPropertyValue($entity, $relationMetadata->relationForeignKey);
    }

    private function getPropertyValue(object $entity, string $propertyName): mixed
    {
        $reflection = new \ReflectionClass($entity);

        // Try direct property access first
        if ($reflection->hasProperty($propertyName)) {
            $property = $reflection->getProperty($propertyName);

            return $property->getValue($entity);
        }

        // Try getter method
        $getterMethod = 'get' . ucfirst($propertyName);
        if ($reflection->hasMethod($getterMethod)) {
            return $entity->$getterMethod();
        }

        // Try ID property as fallback for primary keys
        if ($propertyName === 'id' && $reflection->hasProperty('id')) {
            $property = $reflection->getProperty('id');

            return $property->getValue($entity);
        }

        return null;
    }

    /**
     * Group entities by foreign key value
     * @param array<object> $entities
     * @param string $foreignKeyProperty
     * @return array<mixed, array<object>>
     */
    private function groupByForeignKey(array $entities, string $foreignKeyProperty): array
    {
        $grouped = [];
        foreach ($entities as $entity) {
            $key = $this->getPropertyValue($entity, $foreignKeyProperty);
            if ($key !== null) {
                $keyString = $this->convertKeyForArray($key);
                $grouped[$keyString][] = $entity;
            }
        }

        return $grouped;
    }

    /**
     * Index entities by their primary key
     * @param array<object> $entities
     * @return array<mixed, object>
     */
    private function indexByPrimaryKey(array $entities): array
    {
        $indexed = [];
        foreach ($entities as $entity) {
            $key = $this->getPropertyValue($entity, 'id'); // Assuming 'id' is primary key
            if ($key !== null) {
                $keyString = $this->convertKeyForArray($key);
                $indexed[$keyString] = $entity;
            }
        }

        return $indexed;
    }

    /**
     * Internal method to execute database query and hydrate entities
     * @param string $entityClass
     * @param array $criteria
     * @return array<object>
     */
    private function findByQuery(string $entityClass, array $criteria): array
    {
        $metadata = $this->metadataRegistry->getMetadata($entityClass);

        $query = "SELECT * FROM {$metadata->tableName}";
        $params = [];

        if (! empty($criteria)) {
            $conditions = [];
            foreach ($criteria as $field => $value) {
                if (is_array($value)) {
                    // Handle IN queries for batch loading
                    $placeholders = str_repeat('?,', count($value) - 1) . '?';
                    $columnName = $metadata->getColumnName($field);
                    $conditions[] = "{$columnName} IN ({$placeholders})";
                    $params = array_merge($params, array_values($value));
                } else {
                    $columnName = $metadata->getColumnName($field);
                    $conditions[] = "{$columnName} = ?";
                    $params[] = $value;
                }
            }
            $query .= " WHERE " . implode(' AND ', $conditions);
        }

        $sqlQuery = ValueObjects\SqlQuery::create($query, $params);
        $result = $this->databaseManager->getConnection()->query($sqlQuery);

        $entities = [];
        foreach ($result->fetchAll() as $data) {
            $idValue = $data[$metadata->idColumn];

            // Check identity map first to avoid duplicates
            if ($this->identityMap->has($entityClass, $idValue)) {
                $entities[] = $this->identityMap->get($entityClass, $idValue);
            } else {
                $entity = $this->hydrator->hydrate($metadata, $data);
                $this->identityMap->set($entityClass, $idValue, $entity);
                $entities[] = $entity;
            }
        }

        return $entities;
    }

    private function setRelationOnEntity(object $entity, string $relationName, mixed $relationValue): void
    {
        $reflection = new \ReflectionClass($entity);

        // Try setter methods first
        $setterMethod = 'set' . ucfirst($relationName);
        if ($reflection->hasMethod($setterMethod)) {
            $entity->$setterMethod($relationValue);

            return;
        }

        // For readonly entities, we might need to use a different approach
        // This is tricky with readonly properties - we might need to store in a cache
        // For now, we'll skip setting on readonly entities
        if ($reflection->hasProperty($relationName)) {
            $property = $reflection->getProperty($relationName);
            if (! $property->isReadOnly()) {
                $property->setValue($entity, $relationValue);
            }
        }
    }

    /**
     * Convert a key to a string for use as array index
     * Uses TypeResolver to handle Value Objects like ULID properly
     */
    private function convertKeyForArray(mixed $key): string
    {
        return $this->typeResolver->toArrayKey($key);
    }
}