<?php

declare(strict_types=1);

namespace App\Services;

use App\Models\Artwork;
use App\Models\ArtworkMetricSnapshotHourly;
use App\Models\Leaderboard;
use App\Models\Story;
use App\Models\StoryLike;
use App\Models\StoryView;
use App\Models\User;
use Carbon\CarbonImmutable;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\DB;

class LeaderboardService
{
    private const CACHE_TTL_SECONDS = 3600;
    private const CREATOR_STORE_LIMIT = 10000;
    private const ENTITY_STORE_LIMIT = 500;

    public function calculateCreatorLeaderboard(string $period): int
    {
        $normalizedPeriod = $this->normalizePeriod($period);
        $rows = $normalizedPeriod === Leaderboard::PERIOD_ALL_TIME
            ? $this->allTimeCreatorRows()
            : $this->windowedCreatorRows($this->periodStart($normalizedPeriod));

        return $this->persistRows(Leaderboard::TYPE_CREATOR, $normalizedPeriod, $rows, self::CREATOR_STORE_LIMIT);
    }

    public function calculateArtworkLeaderboard(string $period): int
    {
        $normalizedPeriod = $this->normalizePeriod($period);
        $rows = $normalizedPeriod === Leaderboard::PERIOD_ALL_TIME
            ? $this->allTimeArtworkRows()
            : $this->windowedArtworkRows($this->periodStart($normalizedPeriod));

        return $this->persistRows(Leaderboard::TYPE_ARTWORK, $normalizedPeriod, $rows, self::ENTITY_STORE_LIMIT);
    }

    public function calculateStoryLeaderboard(string $period): int
    {
        $normalizedPeriod = $this->normalizePeriod($period);
        $rows = $normalizedPeriod === Leaderboard::PERIOD_ALL_TIME
            ? $this->allTimeStoryRows()
            : $this->windowedStoryRows($this->periodStart($normalizedPeriod));

        return $this->persistRows(Leaderboard::TYPE_STORY, $normalizedPeriod, $rows, self::ENTITY_STORE_LIMIT);
    }

    public function refreshAll(): array
    {
        $results = [];

        foreach ([
            Leaderboard::TYPE_CREATOR,
            Leaderboard::TYPE_ARTWORK,
            Leaderboard::TYPE_STORY,
        ] as $type) {
            foreach ($this->periods() as $period) {
                $results[$type][$period] = match ($type) {
                    Leaderboard::TYPE_CREATOR => $this->calculateCreatorLeaderboard($period),
                    Leaderboard::TYPE_ARTWORK => $this->calculateArtworkLeaderboard($period),
                    Leaderboard::TYPE_STORY => $this->calculateStoryLeaderboard($period),
                };
            }
        }

        return $results;
    }

    public function getLeaderboard(string $type, string $period, int $limit = 50): array
    {
        $normalizedType = $this->normalizeType($type);
        $normalizedPeriod = $this->normalizePeriod($period);
        $limit = max(1, min($limit, 100));

        return Cache::remember(
            $this->cacheKey($normalizedType, $normalizedPeriod, $limit),
            self::CACHE_TTL_SECONDS,
            function () use ($normalizedType, $normalizedPeriod, $limit): array {
                $items = Leaderboard::query()
                    ->where('type', $normalizedType)
                    ->where('period', $normalizedPeriod)
                    ->orderByDesc('score')
                    ->orderBy('entity_id')
                    ->limit($limit)
                    ->get(['entity_id', 'score'])
                    ->values();

                if ($items->isEmpty()) {
                    return [
                        'type' => $normalizedType,
                        'period' => $normalizedPeriod,
                        'items' => [],
                    ];
                }

                $entities = match ($normalizedType) {
                    Leaderboard::TYPE_CREATOR => $this->creatorEntities($items->pluck('entity_id')->all()),
                    Leaderboard::TYPE_ARTWORK => $this->artworkEntities($items->pluck('entity_id')->all()),
                    Leaderboard::TYPE_STORY => $this->storyEntities($items->pluck('entity_id')->all()),
                };

                return [
                    'type' => $normalizedType,
                    'period' => $normalizedPeriod,
                    'items' => $items->values()->map(function (Leaderboard $row, int $index) use ($entities): array {
                        return [
                            'rank' => $index + 1,
                            'score' => round((float) $row->score, 1),
                            'entity' => $entities[(int) $row->entity_id] ?? null,
                        ];
                    })->filter(fn (array $item): bool => $item['entity'] !== null)->values()->all(),
                ];
            }
        );
    }

    public function creatorRankSummary(int $userId, string $period = Leaderboard::PERIOD_WEEKLY): ?array
    {
        $normalizedPeriod = $this->normalizePeriod($period);

        return Cache::remember(
            sprintf('leaderboard:creator-rank:%d:%s', $userId, $normalizedPeriod),
            self::CACHE_TTL_SECONDS,
            function () use ($userId, $normalizedPeriod): ?array {
                $row = Leaderboard::query()
                    ->where('type', Leaderboard::TYPE_CREATOR)
                    ->where('period', $normalizedPeriod)
                    ->where('entity_id', $userId)
                    ->first(['entity_id', 'score']);

                if (! $row) {
                    return null;
                }

                $higherScores = Leaderboard::query()
                    ->where('type', Leaderboard::TYPE_CREATOR)
                    ->where('period', $normalizedPeriod)
                    ->where(function ($query) use ($row): void {
                        $query->where('score', '>', $row->score)
                            ->orWhere(function ($ties) use ($row): void {
                                $ties->where('score', '=', $row->score)
                                    ->where('entity_id', '<', $row->entity_id);
                            });
                    })
                    ->count();

                return [
                    'period' => $normalizedPeriod,
                    'rank' => $higherScores + 1,
                    'score' => round((float) $row->score, 1),
                ];
            }
        );
    }

    public function periods(): array
    {
        return [
            Leaderboard::PERIOD_DAILY,
            Leaderboard::PERIOD_WEEKLY,
            Leaderboard::PERIOD_MONTHLY,
            Leaderboard::PERIOD_ALL_TIME,
        ];
    }

    public function normalizePeriod(string $period): string
    {
        return match (strtolower(trim($period))) {
            'daily' => Leaderboard::PERIOD_DAILY,
            'weekly' => Leaderboard::PERIOD_WEEKLY,
            'monthly' => Leaderboard::PERIOD_MONTHLY,
            'all', 'all_time', 'all-time' => Leaderboard::PERIOD_ALL_TIME,
            default => Leaderboard::PERIOD_WEEKLY,
        };
    }

    private function normalizeType(string $type): string
    {
        return match (strtolower(trim($type))) {
            'creator', 'creators' => Leaderboard::TYPE_CREATOR,
            'artwork', 'artworks' => Leaderboard::TYPE_ARTWORK,
            'story', 'stories' => Leaderboard::TYPE_STORY,
            default => Leaderboard::TYPE_CREATOR,
        };
    }

    private function periodStart(string $period): CarbonImmutable
    {
        $now = CarbonImmutable::now();

        return match ($period) {
            Leaderboard::PERIOD_DAILY => $now->subDay(),
            Leaderboard::PERIOD_WEEKLY => $now->subWeek(),
            Leaderboard::PERIOD_MONTHLY => $now->subMonth(),
            default => $now->subWeek(),
        };
    }

    private function persistRows(string $type, string $period, Collection $rows, int $limit): int
    {
        $trimmed = $rows
            ->sortByDesc('score')
            ->take($limit)
            ->values();

        DB::transaction(function () use ($type, $period, $trimmed): void {
            Leaderboard::query()
                ->where('type', $type)
                ->where('period', $period)
                ->delete();

            if ($trimmed->isNotEmpty()) {
                $timestamp = now();
                Leaderboard::query()->insert(
                    $trimmed->map(fn (array $row): array => [
                        'type' => $type,
                        'period' => $period,
                        'entity_id' => (int) $row['entity_id'],
                        'score' => round((float) $row['score'], 2),
                        'created_at' => $timestamp,
                        'updated_at' => $timestamp,
                    ])->all()
                );
            }
        });

        $this->flushCache($type, $period);

        return $trimmed->count();
    }

    private function flushCache(string $type, string $period): void
    {
        foreach ([10, 25, 50, 100] as $limit) {
            Cache::forget($this->cacheKey($type, $period, $limit));
        }

        if ($type === Leaderboard::TYPE_CREATOR) {
            Cache::forget('leaderboard:top-creators-widget:' . $period);
        }
    }

    private function cacheKey(string $type, string $period, int $limit): string
    {
        return sprintf('leaderboard:%s:%s:%d', $type, $period, $limit);
    }

    private function allTimeCreatorRows(): Collection
    {
        return User::query()
            ->from('users')
            ->leftJoin('user_statistics as us', 'us.user_id', '=', 'users.id')
            ->whereNull('users.deleted_at')
            ->where('users.is_active', true)
            ->select([
                'users.id',
                DB::raw('COALESCE(users.xp, 0) as xp'),
                DB::raw('COALESCE(us.followers_count, 0) as followers_count'),
                DB::raw('COALESCE(us.favorites_received_count, 0) as likes_received'),
                DB::raw('COALESCE(us.artwork_views_received_count, 0) as artwork_views'),
            ])
            ->get()
            ->map(function ($row): array {
                $score = ((int) $row->xp * 1)
                    + ((int) $row->followers_count * 10)
                    + ((int) $row->likes_received * 2)
                    + ((int) $row->artwork_views * 0.1);

                return [
                    'entity_id' => (int) $row->id,
                    'score' => $score,
                ];
            })
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function windowedCreatorRows(CarbonImmutable $start): Collection
    {
        $xp = DB::table('user_xp_logs')
            ->select('user_id', DB::raw('SUM(xp) as xp'))
            ->where('created_at', '>=', $start)
            ->groupBy('user_id');

        $followers = DB::table('user_followers')
            ->select('user_id', DB::raw('COUNT(*) as followers_count'))
            ->where('created_at', '>=', $start)
            ->groupBy('user_id');

        $likes = DB::table('artwork_likes as likes')
            ->join('artworks as artworks', 'artworks.id', '=', 'likes.artwork_id')
            ->select('artworks.user_id', DB::raw('COUNT(*) as likes_received'))
            ->where('likes.created_at', '>=', $start)
            ->groupBy('artworks.user_id');

        $views = DB::query()
            ->fromSub($this->artworkSnapshotDeltas($start), 'deltas')
            ->join('artworks as artworks', 'artworks.id', '=', 'deltas.artwork_id')
            ->select('artworks.user_id', DB::raw('SUM(deltas.views_delta) as artwork_views'))
            ->groupBy('artworks.user_id');

        return User::query()
            ->from('users')
            ->leftJoinSub($xp, 'xp', 'xp.user_id', '=', 'users.id')
            ->leftJoinSub($followers, 'followers', 'followers.user_id', '=', 'users.id')
            ->leftJoinSub($likes, 'likes', 'likes.user_id', '=', 'users.id')
            ->leftJoinSub($views, 'views', 'views.user_id', '=', 'users.id')
            ->whereNull('users.deleted_at')
            ->where('users.is_active', true)
            ->select([
                'users.id',
                DB::raw('COALESCE(xp.xp, 0) as xp'),
                DB::raw('COALESCE(followers.followers_count, 0) as followers_count'),
                DB::raw('COALESCE(likes.likes_received, 0) as likes_received'),
                DB::raw('COALESCE(views.artwork_views, 0) as artwork_views'),
            ])
            ->get()
            ->map(function ($row): array {
                $score = ((int) $row->xp * 1)
                    + ((int) $row->followers_count * 10)
                    + ((int) $row->likes_received * 2)
                    + ((float) $row->artwork_views * 0.1);

                return [
                    'entity_id' => (int) $row->id,
                    'score' => $score,
                ];
            })
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function allTimeArtworkRows(): Collection
    {
        return Artwork::query()
            ->from('artworks')
            ->join('artwork_stats as stats', 'stats.artwork_id', '=', 'artworks.id')
            ->public()
            ->select([
                'artworks.id',
                DB::raw('COALESCE(stats.favorites, 0) as likes_count'),
                DB::raw('COALESCE(stats.views, 0) as views_count'),
                DB::raw('COALESCE(stats.downloads, 0) as downloads_count'),
                DB::raw('COALESCE(stats.comments_count, 0) as comments_count'),
            ])
            ->get()
            ->map(fn ($row): array => [
                'entity_id' => (int) $row->id,
                'score' => ((int) $row->likes_count * 3)
                    + ((int) $row->views_count * 1)
                    + ((int) $row->downloads_count * 5)
                    + ((int) $row->comments_count * 4),
            ])
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function windowedArtworkRows(CarbonImmutable $start): Collection
    {
        $views = $this->artworkSnapshotDeltas($start);

        $likes = DB::table('artwork_likes')
            ->select('artwork_id', DB::raw('COUNT(*) as favourites_delta'))
            ->where('created_at', '>=', $start)
            ->groupBy('artwork_id');

        $downloads = DB::table('artwork_downloads')
            ->select('artwork_id', DB::raw('COUNT(*) as downloads_delta'))
            ->where('created_at', '>=', $start)
            ->groupBy('artwork_id');

        $comments = DB::table('artwork_comments')
            ->select('artwork_id', DB::raw('COUNT(*) as comments_delta'))
            ->where('created_at', '>=', $start)
            ->where('is_approved', true)
            ->whereNull('deleted_at')
            ->groupBy('artwork_id');

        return Artwork::query()
            ->from('artworks')
            ->leftJoinSub($views, 'views', 'views.artwork_id', '=', 'artworks.id')
            ->leftJoinSub($likes, 'likes', 'likes.artwork_id', '=', 'artworks.id')
            ->leftJoinSub($downloads, 'downloads', 'downloads.artwork_id', '=', 'artworks.id')
            ->leftJoinSub($comments, 'comments', 'comments.artwork_id', '=', 'artworks.id')
            ->where('artworks.is_public', true)
            ->where('artworks.is_approved', true)
            ->whereNull('artworks.deleted_at')
            ->whereNotNull('artworks.published_at')
            ->select([
                'artworks.id',
                DB::raw('COALESCE(likes.favourites_delta, 0) as favourites_delta'),
                DB::raw('COALESCE(views.views_delta, 0) as views_delta'),
                DB::raw('COALESCE(downloads.downloads_delta, 0) as downloads_delta'),
                DB::raw('COALESCE(comments.comments_delta, 0) as comments_delta'),
            ])
            ->get()
            ->map(fn ($row): array => [
                'entity_id' => (int) $row->id,
                'score' => ((int) $row->favourites_delta * 3)
                    + ((int) $row->views_delta * 1)
                    + ((int) $row->downloads_delta * 5)
                    + ((int) $row->comments_delta * 4),
            ])
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function allTimeStoryRows(): Collection
    {
        return Story::query()
            ->published()
            ->select(['id', 'views', 'likes_count', 'comments_count', 'reading_time'])
            ->get()
            ->map(fn (Story $story): array => [
                'entity_id' => (int) $story->id,
                'score' => ((int) $story->views * 1)
                    + ((int) $story->likes_count * 3)
                    + ((int) $story->comments_count * 4)
                    + ((int) $story->reading_time * 0.5),
            ])
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function windowedStoryRows(CarbonImmutable $start): Collection
    {
        $views = StoryView::query()
            ->select('story_id', DB::raw('COUNT(*) as views_count'))
            ->where('created_at', '>=', $start)
            ->groupBy('story_id');

        $likes = StoryLike::query()
            ->select('story_id', DB::raw('COUNT(*) as likes_count'))
            ->where('created_at', '>=', $start)
            ->groupBy('story_id');

        return Story::query()
            ->from('stories')
            ->leftJoinSub($views, 'views', 'views.story_id', '=', 'stories.id')
            ->leftJoinSub($likes, 'likes', 'likes.story_id', '=', 'stories.id')
            ->published()
            ->select([
                'stories.id',
                'stories.comments_count',
                'stories.reading_time',
                DB::raw('COALESCE(views.views_count, 0) as views_count'),
                DB::raw('COALESCE(likes.likes_count, 0) as likes_count'),
            ])
            ->get()
            ->map(fn ($row): array => [
                'entity_id' => (int) $row->id,
                'score' => ((int) $row->views_count * 1)
                    + ((int) $row->likes_count * 3)
                    + ((int) $row->comments_count * 4)
                    + ((int) $row->reading_time * 0.5),
            ])
            ->filter(fn (array $row): bool => $row['score'] > 0)
            ->values();
    }

    private function artworkSnapshotDeltas(CarbonImmutable $start): \Illuminate\Database\Query\Builder
    {
        return ArtworkMetricSnapshotHourly::query()
            ->from('artwork_metric_snapshots_hourly as snapshots')
            ->where('snapshots.bucket_hour', '>=', $start)
            ->select([
                'snapshots.artwork_id',
                DB::raw('GREATEST(MAX(snapshots.views_count) - MIN(snapshots.views_count), 0) as views_delta'),
                DB::raw('GREATEST(MAX(snapshots.downloads_count) - MIN(snapshots.downloads_count), 0) as downloads_delta'),
                DB::raw('GREATEST(MAX(snapshots.favourites_count) - MIN(snapshots.favourites_count), 0) as favourites_delta'),
                DB::raw('GREATEST(MAX(snapshots.comments_count) - MIN(snapshots.comments_count), 0) as comments_delta'),
            ])
            ->groupBy('snapshots.artwork_id')
            ->toBase();
    }

    private function creatorEntities(array $ids): array
    {
        return User::query()
            ->from('users')
            ->leftJoin('user_profiles as profiles', 'profiles.user_id', '=', 'users.id')
            ->whereIn('users.id', $ids)
            ->select([
                'users.id',
                'users.username',
                'users.name',
                'users.level',
                'users.rank',
                'profiles.avatar_hash',
            ])
            ->get()
            ->mapWithKeys(fn ($row): array => [
                (int) $row->id => [
                    'id' => (int) $row->id,
                    'type' => Leaderboard::TYPE_CREATOR,
                    'name' => (string) ($row->username ?: $row->name ?: 'Creator'),
                    'username' => $row->username,
                    'url' => $row->username ? '/@' . $row->username : null,
                    'avatar' => \App\Support\AvatarUrl::forUser((int) $row->id, $row->avatar_hash, 128),
                    'level' => (int) ($row->level ?? 1),
                    'rank' => (string) ($row->rank ?? 'Newbie'),
                ],
            ])
            ->all();
    }

    private function artworkEntities(array $ids): array
    {
        return Artwork::query()
            ->with(['user.profile'])
            ->whereIn('id', $ids)
            ->get()
            ->mapWithKeys(fn (Artwork $artwork): array => [
                (int) $artwork->id => [
                    'id' => (int) $artwork->id,
                    'type' => Leaderboard::TYPE_ARTWORK,
                    'name' => $artwork->title,
                    'url' => '/art/' . $artwork->id . '/' . $artwork->slug,
                    'image' => $artwork->thumbUrl('md') ?? $artwork->thumbnail_url,
                    'creator_name' => (string) ($artwork->user?->username ?: $artwork->user?->name ?: 'Creator'),
                    'creator_url' => $artwork->user?->username ? '/@' . $artwork->user->username : null,
                ],
            ])
            ->all();
    }

    private function storyEntities(array $ids): array
    {
        return Story::query()
            ->with('creator.profile')
            ->whereIn('id', $ids)
            ->get()
            ->mapWithKeys(fn (Story $story): array => [
                (int) $story->id => [
                    'id' => (int) $story->id,
                    'type' => Leaderboard::TYPE_STORY,
                    'name' => $story->title,
                    'url' => '/stories/' . $story->slug,
                    'image' => $story->cover_url,
                    'creator_name' => (string) ($story->creator?->username ?: $story->creator?->name ?: 'Creator'),
                    'creator_url' => $story->creator?->username ? '/@' . $story->creator->username : null,
                ],
            ])
            ->all();
    }
}