<?php

declare(strict_types=1);

namespace App\Services;

use App\Models\DocumentationFolder;
use App\Models\DocumentationFolderPermission;
use App\Models\Role;
use App\Models\User;
use Illuminate\Database\Eloquent\Collection;

class DocumentationAccessService
{
    /** @var array<int, DocumentationFolder> */
    private array $folders = [];

    /** @var array<int, Collection<int, DocumentationFolderPermission>> */
    private array $effectiveRules = [];

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

    public function canRead(User $user, DocumentationFolder $folder): bool
    {
        return $this->can($user, $folder, false);
    }

    public function canWrite(User $user, DocumentationFolder $folder): bool
    {
        return $this->can($user, $folder, true);
    }

    public function canManagePermissions(User $user, DocumentationFolder $folder): bool
    {
        return $this->isAdministrator($user)
            || ($user->hasPermission('documents.update') && $this->canWrite($user, $folder));
    }

    /**
     * Returns readable folders plus their ancestors required to render the tree.
     * Ancestors without read access are navigation-only nodes.
     *
     * @return Collection<int, DocumentationFolder>
     */
    public function navigationFolders(User $user): Collection
    {
        $folders = DocumentationFolder::query()
            ->with(['permissionRules.role', 'creator'])
            ->orderBy('name')
            ->get();

        foreach ($folders as $folder) {
            $this->folders[$folder->id] = $folder;
        }

        $included = [];
        foreach ($folders as $folder) {
            $canRead = $this->canRead($user, $folder);
            $folder->setAttribute('can_read', $canRead);
            $folder->setAttribute('can_write', $this->canWrite($user, $folder));

            if (! $canRead) {
                continue;
            }

            $current = $folder;
            while ($current) {
                $included[$current->id] = true;
                $current = $current->parent_id ? ($this->folders[$current->parent_id] ?? null) : null;
            }
        }

        return $folders
            ->filter(fn (DocumentationFolder $folder): bool => isset($included[$folder->id]))
            ->values();
    }

    public function forgetCachedRules(): void
    {
        $this->effectiveRules = [];
        $this->folders = [];
    }

    private function can(User $user, DocumentationFolder $folder, bool $write): bool
    {
        if ($this->isAdministrator($user)) {
            return true;
        }

        $this->folders[$folder->id] = $folder;

        foreach ($this->rulesFor($folder) as $rule) {
            if (! $this->matches($rule, $user)) {
                continue;
            }

            if ($write && $rule->can_write) {
                return true;
            }

            if (! $write && ($rule->can_read || $rule->can_write)) {
                return true;
            }
        }

        return false;
    }

    /** @return Collection<int, DocumentationFolderPermission> */
    private function rulesFor(DocumentationFolder $folder): Collection
    {
        if (isset($this->effectiveRules[$folder->id])) {
            return $this->effectiveRules[$folder->id];
        }

        if ($folder->inherits_permissions && $folder->parent_id) {
            $parent = $this->folders[$folder->parent_id] ?? DocumentationFolder::query()
                ->with('permissionRules.role')
                ->find($folder->parent_id);

            if ($parent) {
                $this->folders[$parent->id] = $parent;

                return $this->effectiveRules[$folder->id] = $this->rulesFor($parent);
            }
        }

        $rules = $folder->relationLoaded('permissionRules')
            ? $folder->permissionRules
            : $folder->permissionRules()->with('role')->get();

        return $this->effectiveRules[$folder->id] = $rules;
    }

    private function matches(DocumentationFolderPermission $rule, User $user): bool
    {
        return match ($rule->subject_type) {
            DocumentationFolderPermission::SUBJECT_ALL => true,
            DocumentationFolderPermission::SUBJECT_USER => $rule->user_id === $user->id,
            DocumentationFolderPermission::SUBJECT_ROLE => $rule->role_id === $user->role_id
                || $rule->role?->slug === $user->resolvedRoleSlug(),
            default => false,
        };
    }
}