"use client";

import React from "react";
import { RefreshCw } from "lucide-react";

import ExplorerPageShell from "@/components/explorer/ExplorerPageShell";
import ExplorerSectionCard from "@/components/explorer/ExplorerSectionCard";
import ExplorerLoading from "@/components/explorer/states/ExplorerLoading";
import ExplorerEmpty from "@/components/explorer/states/ExplorerEmpty";
import ForbiddenView from "@/components/system/ForbiddenView";

import AdminUsersFilters from "@/components/admin/users/AdminUsersFilters";
import AdminUsersTableToolbar from "@/components/admin/users/AdminUsersTableToolbar";
import UsersTable from "@/components/admin/users/UsersTable";
import CreateUserDialog from "@/components/admin/users/CreateUserDialog";
import { normalizeBranchIdDraft } from "@/components/admin/users/usersUi";
import {
	ADMIN_USERS_SORT,
	sortAdminUsers,
} from "@/lib/frontend/admin/users/usersSorting";

import { ApiClientError } from "@/lib/frontend/apiClient";
import { buildLoginUrl, LOGIN_REASONS } from "@/lib/frontend/authRedirect";
import { useAdminUsersQuery } from "@/lib/frontend/admin/users/useAdminUsersQuery";

import { Button } from "@/components/ui/button";
import { Alert, AlertTitle, AlertDescription } from "@/components/ui/alert";

const LIMIT = 50;

export default function AdminUsersClient() {
	const [draft, setDraft] = React.useState({
		q: "",
		role: "",
		branchId: "",
	});

	const [query, setQuery] = React.useState({
		q: null,
		role: null,
		branchId: null,
		sort: ADMIN_USERS_SORT.DEFAULT,
	});

	const {
		status,
		items,
		nextCursor,
		error,
		refresh,
		loadMore,
		isLoadingMore,
		loadMoreError,
	} = useAdminUsersQuery({ query, limit: LIMIT });

	React.useEffect(() => {
		if (!(error instanceof ApiClientError)) return;

		if (error.code === "AUTH_UNAUTHENTICATED") {
			const next =
				typeof window !== "undefined"
					? `${window.location.pathname}${window.location.search}`
					: "/admin/users";

			window.location.replace(
				buildLoginUrl({ reason: LOGIN_REASONS.EXPIRED, next }),
			);
		}
	}, [error]);

	if (
		error instanceof ApiClientError &&
		error.code === "AUTH_FORBIDDEN_USER_MANAGEMENT"
	) {
		return <ForbiddenView />;
	}

	const disabled = status === "loading" || isLoadingMore;
	const effectiveSortMode = query.sort || ADMIN_USERS_SORT.DEFAULT;
	const visibleItems = React.useMemo(() => {
		return sortAdminUsers(items, effectiveSortMode);
	}, [items, effectiveSortMode]);

	function onDraftChange(patch) {
		setDraft((prev) => ({ ...prev, ...(patch || {}) }));
	}

	function applyFilters() {
		setQuery({
			q: draft.q.trim() ? draft.q.trim() : null,
			role: draft.role.trim() ? draft.role.trim() : null,
			branchId: normalizeBranchIdDraft(draft.branchId) || null,
			sort: query.sort || ADMIN_USERS_SORT.DEFAULT,
		});
	}

	function resetFilters() {
		setDraft({ q: "", role: "", branchId: "" });
		setQuery((prev) => ({
			q: null,
			role: null,
			branchId: null,
			sort: prev.sort || ADMIN_USERS_SORT.DEFAULT,
		}));
	}

	function onSortModeChange(nextSortMode) {
		setQuery((prev) => ({
			...prev,
			sort: nextSortMode || ADMIN_USERS_SORT.DEFAULT,
		}));
	}

	const actions = (
		<Button
			variant="outline"
			size="sm"
			onClick={refresh}
			disabled={disabled}
			title="Aktualisieren"
		>
			<RefreshCw className="h-4 w-4" />
			Aktualisieren
		</Button>
	);

	return (
		<ExplorerPageShell
			title="Benutzerverwaltung"
			description="Benutzerkonten anzeigen und filtern (nur Superadmin/Entwicklung)."
			actions={actions}
		>
			<ExplorerSectionCard
				title="Benutzer"
				description="Suche und Filter anwenden."
				headerRight={
					<CreateUserDialog disabled={disabled} onCreated={refresh} />
				}
			>
				<div className="space-y-4">
					<AdminUsersFilters
						draft={draft}
						onDraftChange={onDraftChange}
						onApply={applyFilters}
						onReset={resetFilters}
						disabled={disabled}
					/>

					<AdminUsersTableToolbar
						loadedCount={visibleItems.length}
						sortMode={effectiveSortMode}
						onSortModeChange={onSortModeChange}
						disabled={disabled}
					/>

					{status === "error" ? (
						<Alert variant="destructive">
							<AlertTitle>Fehler</AlertTitle>
							<AlertDescription>
								{error instanceof ApiClientError
									? `Anfrage fehlgeschlagen (${error.code}). Bitte erneut versuchen.`
									: "Anfrage fehlgeschlagen. Bitte erneut versuchen."}
							</AlertDescription>
						</Alert>
					) : null}

					{status === "loading" ? (
						<ExplorerLoading variant="table" count={8} />
					) : items.length === 0 ? (
						<ExplorerEmpty
							title="Keine Benutzer gefunden"
							description="Für die aktuellen Filter wurden keine Benutzer gefunden."
							upHref={null}
						/>
					) : (
						<UsersTable
							items={visibleItems}
							disabled={disabled}
							onUserUpdated={refresh}
						/>
					)}

					{loadMoreError ? (
						<Alert variant="destructive">
							<AlertTitle>
								Weitere Benutzer konnten nicht geladen werden
							</AlertTitle>
							<AlertDescription>Bitte erneut versuchen.</AlertDescription>
						</Alert>
					) : null}

					{nextCursor ? (
						<div className="flex justify-center">
							<Button
								type="button"
								variant="outline"
								onClick={loadMore}
								disabled={isLoadingMore}
								title="Mehr laden"
							>
								{isLoadingMore ? "Lädt…" : "Mehr laden"}
							</Button>
						</div>
					) : null}
				</div>
			</ExplorerSectionCard>
		</ExplorerPageShell>
	);
}