<?php

namespace App\Services\Access;

use App\Models\Permission;
use App\Models\Role;
use App\Models\User;
use Illuminate\Database\QueryException;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Schema;

class AccessService
{
    private const CACHE_VERSION_KEY = 'permissions:version';

    public function can(User $user, string $permission): bool
    {
        if ($this->isDirectAdmin($user)) {
            return true;
        }

        $effect = $this->getEffectivePermissions($user)->get($permission);

        return $effect === 'allow';
    }

    public function canAny(User $user, array $permissions): bool
    {
        foreach ($permissions as $permission) {
            if ($this->can($user, trim((string) $permission))) {
                return true;
            }
        }

        return false;
    }

    public function canViewField(User $user, string $module, string $field, ?string $entity = null): bool
    {
        return $this->can($user, $this->fieldPermissionSlug($module, $field, 'view'));
    }

    public function canUpdateField(User $user, string $module, string $field, ?string $entity = null): bool
    {
        return $this->can($user, $this->fieldPermissionSlug($module, $field, 'update'));
    }

    public function filterReadableFields(User $user, string $module, array $fields, ?string $entity = null): array
    {
        return array_values(array_filter(
            $fields,
            fn (string $field): bool => $this->canViewField($user, $module, $field, $entity)
        ));
    }

    public function filterWritableData(User $user, string $module, array $data, ?string $entity = null): array
    {
        return array_filter(
            $data,
            fn (string $field): bool => $this->canUpdateField($user, $module, $field, $entity),
            ARRAY_FILTER_USE_KEY
        );
    }

    public function assertCan(User $user, string $permission): void
    {
        abort_unless($this->can($user, $permission), 403);
    }

    public function roleHasPermission(Role $role, string $permission): bool
    {
        if ($role->slug === Role::ADMIN) {
            return true;
        }

        $permissionModel = $role->permissions()
            ->where('slug', $permission)
            ->first();

        return $permissionModel?->pivot?->effect === 'allow';
    }

    public function getEffectivePermissions(User $user): Collection
    {
        if ($this->isDirectAdmin($user)) {
            try {
                return Permission::query()->pluck('slug')->mapWithKeys(fn (string $slug): array => [$slug => 'allow']);
            } catch (QueryException) {
                return collect();
            }
        }

        return Cache::remember(
            $this->cacheKey($user),
            now()->addHour(),
            fn (): Collection => $this->resolveEffectivePermissions($user)
        );
    }

    public function bumpCacheVersion(): void
    {
        Cache::forever(self::CACHE_VERSION_KEY, $this->cacheVersion() + 1);
    }

    private function resolveEffectivePermissions(User $user): Collection
    {
        if (!$this->tablesExist()) {
            return collect();
        }

        $effects = collect();

        $role = $user->roleModel()->with('permissions')->first();
        if ($role) {
            foreach ($role->permissions as $permission) {
                $effects->put($permission->slug, $permission->pivot->effect);
            }
        }

        $userPermissions = $user->permissions()
            ->where(function ($query) {
                $query->whereNull('expires_at')
                    ->orWhere('expires_at', '>', now());
            })
            ->get();

        foreach ($userPermissions as $permission) {
            $effects->put($permission->slug, $permission->pivot->effect);
        }

        return $effects;
    }

    private function isDirectAdmin(User $user): bool
    {
        return $user->resolvedRoleSlug() === Role::ADMIN;
    }

    private function fieldPermissionSlug(string $module, string $field, string $action): string
    {
        return "{$module}.fields.{$field}.{$action}";
    }

    private function cacheKey(User $user): string
    {
        return 'permissions:user:' . $user->id . ':v' . $this->cacheVersion();
    }

    private function cacheVersion(): int
    {
        return (int) Cache::get(self::CACHE_VERSION_KEY, 1);
    }

    private function tablesExist(): bool
    {
        return Schema::hasTable('roles')
            && Schema::hasTable('permissions')
            && Schema::hasTable('role_permissions')
            && Schema::hasTable('user_permissions');
    }
}