<?php

declare(strict_types=1);

namespace App\Modules\Files\Access;

use App\Models\User;
use App\Modules\Files\Models\File;
use App\Modules\Files\Models\FileAssignment;
use App\Modules\Files\Models\Folder;
use App\Modules\Files\Models\FolderAssignment;
use App\Modules\Groups\Models\Group;
use App\Modules\Identity\UserType;
use Illuminate\Database\Eloquent\Builder;

/**
 * The single point that decides which library content a staff member
 * sees. An unscoped staff member sees the whole shared library; a
 * client-scoped one (see User::isClientScoped) sees only the files &
 * folders they created, plus everything belonging to the clients
 * assigned to them.
 *
 * Every staff listing goes through here, and the policies consult
 * allowsFile()/allowsFolder() so direct access (download, details,
 * edit…) respects the same boundary.
 *
 * @method Builder<File> files(User $user)
 * @method Builder<Folder> folders(User $user)
 */
class StaffLibraryScope
{
    /**
     * Built queries, by user id. Building one is not free: it walks the
     * assigned clients and File::scopeVisibleToClient runs four immediate
     * lookups for each of them, none of which depend on the query being
     * built. Callers ask over and over — the policies ask once per row on
     * a listing, and Gate resolves a fresh policy for every check — so the
     * same handful of lookups were being repeated per row.
     *
     * A clone goes back rather than the query itself, since every caller
     * adds to it. Registered with the container as `scoped`, so the memo
     * lasts a request and is dropped between queue jobs.
     *
     * @var array<int, Builder<File>>
     */
    private array $files = [];

    /** @var array<int, Builder<Folder>> */
    private array $folders = [];

    /**
     * @return Builder<File>
     */
    public function files(User $user): Builder
    {
        return clone ($this->files[$user->id] ??= $this->buildFiles($user));
    }

    /**
     * @return Builder<File>
     */
    private function buildFiles(User $user): Builder
    {
        $query = File::query();

        if (! $user->isClientScoped()) {
            return $query;
        }

        // Own uploads ∪ files visible to each assigned client. The
        // per-client visibility is File::scopeVisibleToClient — the single
        // source of truth for client file access — so no rule is duplicated.
        return $query->where(function (Builder $outer) use ($user): void {
            $outer->where('uploaded_by', $user->id);

            foreach ($user->assignedClients as $client) {
                $outer->orWhere(fn (Builder $scoped) => $scoped->visibleToClient($client));
            }
        });
    }

    /**
     * @return Builder<Folder>
     */
    public function folders(User $user): Builder
    {
        return clone ($this->folders[$user->id] ??= $this->buildFolders($user));
    }

    /**
     * @return Builder<Folder>
     */
    private function buildFolders(User $user): Builder
    {
        $query = Folder::query();

        if (! $user->isClientScoped()) {
            return $query;
        }

        return $query->where(function (Builder $outer) use ($user): void {
            $outer->where('created_by', $user->id);

            foreach ($user->assignedClients as $client) {
                $outer->orWhere(fn (Builder $scoped) => $scoped->visibleToClient($client));
            }
        });
    }

    /**
     * Whether a scoped staff member may reach this specific file. Unscoped
     * staff always may; the policies AND this into their permission checks
     * so direct access respects the same boundary as the listings.
     */
    public function allowsFile(User $user, File $file): bool
    {
        if (! $user->isClientScoped()) {
            return true;
        }

        return $this->files($user)->whereKey($file->getKey())->exists();
    }

    public function allowsFolder(User $user, Folder $folder): bool
    {
        if (! $user->isClientScoped()) {
            return true;
        }

        return $this->folders($user)->whereKey($folder->getKey())->exists();
    }

    /**
     * Client ids a user may share with, or null when unrestricted (the
     * whole roster). A scoped user may only share with their assigned
     * clients.
     *
     * @return list<int>|null
     */
    public function assignableClientIds(User $user): ?array
    {
        if (! $user->isClientScoped()) {
            return null;
        }

        return array_values($user->assignedClients()->pluck('users.id')->map(fn ($id): int => (int) $id)->all());
    }

    /**
     * Group ids a user may share with, or null when unrestricted. A scoped
     * user may share with any group that contains at least one of their
     * assigned clients.
     *
     * @return list<int>|null
     */
    public function assignableGroupIds(User $user): ?array
    {
        if (! $user->isClientScoped()) {
            return null;
        }

        $clientIds = $this->assignableClientIds($user) ?? [];

        if ($clientIds === []) {
            return [];
        }

        return array_values(Group::query()
            ->whereHas('members', fn (Builder $members) => $members->whereIn('users.id', $clientIds))
            ->pluck('id')->map(fn ($id): int => (int) $id)->all());
    }

    public function canAssignClient(User $user, User $client): bool
    {
        $ids = $this->assignableClientIds($user);

        return $ids === null || in_array($client->id, $ids, true);
    }

    /**
     * Every client this staff member may act on, as a query.
     *
     * The listing half of canAssignClient(), so a screen narrows by the
     * same rule its buttons are guarded with rather than restating it —
     * which is how ClientsController came to list every client on the
     * installation, name and email, to a viewer who could reach nothing
     * of theirs. An unscoped user gets the whole roster, unchanged.
     *
     * @return Builder<User>
     */
    public function clients(User $user): Builder
    {
        $query = User::query()->where('type', UserType::Client);
        $ids = $this->assignableClientIds($user);

        return $ids === null ? $query : $query->whereIn('id', $ids);
    }

    public function canAssignGroup(User $user, Group $group): bool
    {
        $ids = $this->assignableGroupIds($user);

        return $ids === null || in_array($group->id, $ids, true);
    }

    /**
     * Whether a staff member may put a client into a group, or take one
     * out again.
     *
     * Not canAssignGroup(): that answers "may I share with this group",
     * and it answers it *from* the membership — a group counts as the
     * user's because one of their clients is in it. Deciding membership
     * with a predicate derived from membership means whoever may edit
     * the list also decides what the list entitles them to, which is not
     * a boundary at all. It is also the wrong answer here in the other
     * direction: a group nobody has joined yet belongs to nobody, so a
     * scoped staff member could never put the first member into a group
     * they had just created.
     *
     * The question membership actually asks is about reach. Joining a
     * group hands the new member everything shared with it, and — when
     * that member is one of the actor's own clients — hands the actor
     * the same content back through File::scopeVisibleToClient, which is
     * what StaffLibraryScope::files() is built on. So both sides have to
     * hold: the client must be one this staff member holds, and the
     * group must not already reach beyond their library. A group with
     * nothing shared with it passes trivially, which is what keeps a
     * newly created one usable.
     *
     * Unscoped staff are unaffected — both halves are true for them by
     * construction.
     */
    public function allowsGroupMembership(User $user, Group $group, User $client): bool
    {
        return $this->canAssignClient($user, $client) && $this->groupReachesNoFurther($user, $group);
    }

    /**
     * Whether this staff member may change a group itself — rename it,
     * make it public, delete it.
     *
     * The reach half of allowsGroupMembership, on its own because there
     * is no client in the question. Deleting a group is the destructive
     * end of it: an assignment to a group is how its members reach a
     * file, so removing the group takes that access away from every one
     * of them. A staff member who may not add somebody to a group out of
     * their reach should not be able to delete it out from under the
     * people already in it.
     */
    public function allowsGroupChange(User $user, Group $group): bool
    {
        return $this->groupReachesNoFurther($user, $group);
    }

    /**
     * Whether everything shared with this group is already inside the
     * user's library — files assigned to it, and the folders whose
     * subtrees it can browse.
     *
     * Asked as "is anything shared with this group outside my library",
     * rather than by counting assignment rows against library rows. An
     * assignment outlives the thing it points at: nothing clears these
     * rows when a file or folder is deleted, and a deleted one can never
     * appear in files()/folders(), which exclude trashed rows. Counting
     * therefore never balanced again, and the group became permanently
     * unmanageable for a scoped staff member — including for their own
     * clients, and including removing somebody. Starting from the live
     * row rather than from the assignment ignores the dead ones by
     * construction, which is also the right answer: a deleted file is
     * not reach, because nobody can reach it.
     */
    private function groupReachesNoFurther(User $user, Group $group): bool
    {
        if (! $user->isClientScoped()) {
            return true;
        }

        $morph = $group->getMorphClass();

        $assignedFiles = FileAssignment::query()->select('file_id')
            ->where('assignable_type', $morph)->where('assignable_id', $group->id);

        $outside = File::query()
            ->whereIn('id', $assignedFiles)
            ->whereNotIn('id', $this->files($user)->select('id'))
            ->exists();

        if ($outside) {
            return false;
        }

        $assignedFolders = FolderAssignment::query()->select('folder_id')
            ->where('assignable_type', $morph)->where('assignable_id', $group->id);

        return ! Folder::query()
            ->whereIn('id', $assignedFolders)
            ->whereNotIn('id', $this->folders($user)->select('id'))
            ->exists();
    }
}