<?php

declare(strict_types=1);

namespace App\Services\Sitemaps;

use DateTimeImmutable;
use DateTimeInterface;

final class SitemapIndexService
{
    public function __construct(
        private readonly SitemapRegistry $registry,
        private readonly SitemapShardService $shards,
    ) {
    }

    /**
     * @return list<SitemapIndexItem>
     */
    public function items(?array $families = null): array
    {
        $items = [];
        $selectedFamilies = $families ?? (array) config('sitemaps.enabled', []);
        $groupedFamilies = [];

        foreach ($this->activeGroupIndexes($selectedFamilies) as $groupName => $groupFamilies) {
            $items[] = new SitemapIndexItem(
                url('/sitemaps/' . $groupName . '.xml'),
                $this->lastModifiedForFamilies($groupFamilies),
            );

            foreach ($groupFamilies as $family) {
                $groupedFamilies[$family] = true;
            }
        }

        foreach ($selectedFamilies as $name) {
            if (isset($groupedFamilies[(string) $name])) {
                continue;
            }

            $builder = $this->registry->get((string) $name);

            if ($builder === null) {
                continue;
            }

            $items[] = new SitemapIndexItem(
                url('/sitemaps/' . $this->shards->rootEntryName($builder) . '.xml'),
                $builder->lastModified(),
            );
        }

        return $items;
    }

    /**
     * @param  list<string>  $families
     * @return list<SitemapIndexItem>
     */
    public function itemsForFamilies(array $families): array
    {
        $items = [];

        foreach ($families as $family) {
            $builder = $this->registry->get($family);

            if ($builder === null) {
                continue;
            }

            $items[] = new SitemapIndexItem(
                url('/sitemaps/' . $this->shards->rootEntryName($builder) . '.xml'),
                $builder->lastModified(),
            );
        }

        return $items;
    }

    /**
     * @return list<SitemapIndexItem>
     */
    public function itemsForBuilder(SitemapBuilder $builder): array
    {
        if ($builder instanceof ShardableSitemapBuilder && $this->shards->shardCount($builder) > 1) {
            $items = [];

            foreach (range(1, $this->shards->shardCount($builder)) as $shard) {
                $items[] = new SitemapIndexItem(
                    url('/sitemaps/' . $this->shards->canonicalShardName($builder->name(), $shard) . '.xml'),
                    $builder->lastModifiedForShard($shard),
                );
            }

            return $items;
        }

        return [new SitemapIndexItem(
            url('/sitemaps/' . $this->shards->rootEntryName($builder) . '.xml'),
            $builder->lastModified(),
        )];
    }

    /**
     * @param  list<string>  $selectedFamilies
     * @return array<string, list<string>>
     */
    public function activeGroupIndexes(array $selectedFamilies): array
    {
        $selectedLookup = array_fill_keys($selectedFamilies, true);
        $groups = [];

        foreach ((array) config('sitemaps.group_indexes', []) as $groupName => $groupFamilies) {
            if (! is_string($groupName) || $groupName === '') {
                continue;
            }

            $validFamilies = array_values(array_filter(
                (array) $groupFamilies,
                fn (mixed $family): bool => is_string($family) && $family !== '' && $this->registry->get($family) !== null,
            ));

            if ($validFamilies === []) {
                continue;
            }

            foreach ($validFamilies as $family) {
                if (! isset($selectedLookup[$family])) {
                    continue 2;
                }
            }

            $groups[$groupName] = $validFamilies;
        }

        return $groups;
    }

    /**
     * @param  list<string>  $families
     */
    private function lastModifiedForFamilies(array $families): ?DateTimeInterface
    {
        $latest = null;

        foreach ($families as $family) {
            $builder = $this->registry->get($family);

            if ($builder === null) {
                continue;
            }

            $lastModified = $builder->lastModified();

            if ($lastModified !== null) {
                $candidate = $lastModified instanceof DateTimeInterface
                    ? $lastModified
                    : new DateTimeImmutable((string) $lastModified);

                if ($latest === null || $candidate->getTimestamp() > $latest->getTimestamp()) {
                    $latest = $candidate;
                }
            }
        }

        return $latest;
    }
}