<?php

namespace DishPlanner\Dashboard\Services;

use App\Models\Dish;
use App\Models\Planner;
use App\Models\ScheduledUserDish;
use App\Models\User;
use Carbon\Carbon;
use Illuminate\Support\Collection;

class DashboardStatsService
{
    public function __construct(private readonly Planner $planner) {}

    /**
     * @return array{
     *     dish_count: int,
     *     user_count: int,
     *     meals_this_month: int,
     *     favorite_dishes: Collection<int, array{user: User, dish: Dish|null, count: int}>
     * }
     */
    public function stats(): array
    {
        // PHPStan cannot equate the identical array shapes; see favoriteDishes().
        /** @phpstan-ignore return.type */
        return [
            'dish_count' => $this->dishCount(),
            'user_count' => $this->userCount(),
            'meals_this_month' => $this->mealsThisMonth(),
            'favorite_dishes' => $this->favoriteDishes(),
        ];
    }

    public function dishCount(): int
    {
        return Dish::where('planner_id', $this->planner->id)->count();
    }

    public function userCount(): int
    {
        return User::where('planner_id', $this->planner->id)->count();
    }

    public function mealsThisMonth(): int
    {
        $start = Carbon::now()->startOfMonth()->toDateString();
        $end = Carbon::now()->endOfMonth()->toDateString();

        return ScheduledUserDish::query()
            ->where('is_skipped', false)
            ->whereNotNull('user_dish_id')
            ->whereHas('schedule', fn ($query) => $query
                ->where('planner_id', $this->planner->id)
                ->where('is_skipped', false)
                ->whereBetween('date', [$start, $end]))
            ->count();
    }

    /**
     * @return Collection<int, array{user: User, dish: Dish|null, count: int}>
     */
    public function favoriteDishes(): Collection
    {
        $users = User::where('planner_id', $this->planner->id)
            ->orderBy('name')
            ->get();

        $favorites = ScheduledUserDish::query()
            ->with(['user', 'userDish.dish'])
            ->whereNotNull('user_dish_id')
            ->whereHas('schedule', fn ($query) => $query->where('planner_id', $this->planner->id))
            ->get()
            ->groupBy('user_id')
            ->map(fn (Collection $items) => $this->favoriteForItems($items));

        // Eloquent map() returns a union type PHPStan cannot narrow to the declared shape.
        /** @phpstan-ignore return.type */
        return $users->map(fn (User $user) => $favorites->get($user->id) ?? [
            'user' => $user,
            'dish' => null,
            'count' => 0,
        ])->toBase()->values();
    }

    /**
     * @param  Collection<int, ScheduledUserDish>  $items
     * @return array{user: User, dish: Dish|null, count: int}
     */
    private function favoriteForItems(Collection $items): array
    {
        $dishCounts = $items
            ->groupBy(fn (ScheduledUserDish $item) => $item->userDish->dish_id)
            ->map(fn (Collection $dishItems) => [
                'dish' => $dishItems->firstOrFail()->userDish->dish,
                'count' => $dishItems->count(),
            ]);

        $top = $dishCounts->sort(function (array $a, array $b) {
            if ($a['count'] === $b['count']) {
                return ($a['dish']->name ?? '') <=> ($b['dish']->name ?? '');
            }

            return $b['count'] <=> $a['count'];
        })->first();

        return [
            'user' => $items->firstOrFail()->user,
            'dish' => $top['dish'] ?? null,
            'count' => $top['count'] ?? 0,
        ];
    }
}