'use client';

import { useState } from 'react';

import {
  Building2,
  ChevronDown,
  ChevronRight,
  Link2,
  Network,
  Unlink,
} from 'lucide-react';
import { useAction } from 'next-safe-action/hooks';

import { Badge } from '@kit/ui/badge';
import { Button } from '@kit/ui/button';
import { Card, CardContent, CardHeader, CardTitle } from '@kit/ui/card';
import { toast } from '@kit/ui/sonner';

import {
  linkChildAccount,
  unlinkChildAccount,
} from '../server/actions/hierarchy-actions';
import type { HierarchyNode } from '../server/api';

interface HierarchyTreeProps {
  accountId: string;
  tree: HierarchyNode;
  availableAccounts: Array<{
    id: string;
    name: string;
    slug: string | null;
  }>;
}

function countDescendants(node: HierarchyNode): number {
  let count = node.children.length;
  for (const child of node.children) {
    count += countDescendants(child);
  }
  return count;
}

function TreeNodeRow({
  node,
  onUnlink,
  isUnlinking,
}: {
  node: HierarchyNode;
  onUnlink: (childId: string) => void;
  isUnlinking: boolean;
}) {
  const [expanded, setExpanded] = useState(node.depth < 2);
  const hasChildren = node.children.length > 0;
  const isRoot = node.depth === 0;

  return (
    <div>
      <div
        className="hover:bg-muted/50 flex items-center gap-2 rounded-md px-2 py-2 transition-colors"
        style={{ paddingLeft: `${node.depth * 24 + 8}px` }}
      >
        {hasChildren ? (
          <button
            onClick={() => setExpanded(!expanded)}
            className="text-muted-foreground hover:text-foreground"
          >
            {expanded ? (
              <ChevronDown className="h-4 w-4" />
            ) : (
              <ChevronRight className="h-4 w-4" />
            )}
          </button>
        ) : (
          <span className="w-4" />
        )}

        <Building2 className="text-muted-foreground h-4 w-4 shrink-0" />

        <span className="flex-1 truncate text-sm font-medium">
          {node.name}
          {node.slug && (
            <span className="text-muted-foreground ml-2 text-xs">
              /{node.slug}
            </span>
          )}
        </span>

        {hasChildren && (
          <span className="text-muted-foreground text-xs">
            {node.children.length} direkt
          </span>
        )}

        {isRoot ? (
          <Badge variant="default" className="text-xs">
            Dachverband
          </Badge>
        ) : node.depth === 1 ? (
          <Badge variant="secondary" className="text-xs">
            Unterverband
          </Badge>
        ) : (
          <Badge variant="outline" className="text-xs">
            Verein
          </Badge>
        )}

        {!isRoot && (
          <Button
            variant="ghost"
            size="sm"
            className="text-muted-foreground hover:text-destructive h-7 w-7 shrink-0 p-0"
            onClick={() => onUnlink(node.id)}
            disabled={isUnlinking}
            title="Verknüpfung lösen"
          >
            <Unlink className="h-3.5 w-3.5" />
          </Button>
        )}
      </div>

      {expanded &&
        hasChildren &&
        node.children.map((child) => (
          <TreeNodeRow
            key={child.id}
            node={child}
            onUnlink={onUnlink}
            isUnlinking={isUnlinking}
          />
        ))}
    </div>
  );
}

export function HierarchyTree({
  accountId,
  tree,
  availableAccounts,
}: HierarchyTreeProps) {
  const [selectedAccountId, setSelectedAccountId] = useState('');

  const totalDescendants = countDescendants(tree);

  const { execute: executeLink, isPending: isLinking } = useAction(
    linkChildAccount,
    {
      onSuccess: ({ data }) => {
        if (data?.success) {
          toast.success('Organisation erfolgreich verknüpft');
          setSelectedAccountId('');
        }
      },
      onError: ({ error }) => {
        toast.error(
          error.serverError ?? 'Fehler beim Verknüpfen der Organisation',
        );
      },
    },
  );

  const { execute: executeUnlink, isPending: isUnlinking } = useAction(
    unlinkChildAccount,
    {
      onSuccess: ({ data }) => {
        if (data?.success) {
          toast.success('Verknüpfung gelöst');
        }
      },
      onError: ({ error }) => {
        toast.error(
          error.serverError ?? 'Fehler beim Entfernen der Verknüpfung',
        );
      },
    },
  );

  function handleLink() {
    if (!selectedAccountId) return;
    executeLink({
      parentAccountId: accountId,
      childAccountId: selectedAccountId,
    });
  }

  function handleUnlink(childId: string) {
    executeUnlink({
      childAccountId: childId,
      parentAccountId: accountId,
    });
  }

  return (
    <div className="space-y-6">
      {/* Summary */}
      <div className="grid grid-cols-2 gap-4 sm:grid-cols-3">
        <Card>
          <CardContent className="p-4">
            <div className="text-muted-foreground text-xs">
              Direkte Unterverbände
            </div>
            <div className="text-2xl font-bold">{tree.children.length}</div>
          </CardContent>
        </Card>
        <Card>
          <CardContent className="p-4">
            <div className="text-muted-foreground text-xs">
              Organisationen gesamt
            </div>
            <div className="text-2xl font-bold">{totalDescendants}</div>
          </CardContent>
        </Card>
        <Card>
          <CardContent className="p-4">
            <div className="text-muted-foreground text-xs">
              Verfügbar zum Verknüpfen
            </div>
            <div className="text-2xl font-bold">{availableAccounts.length}</div>
          </CardContent>
        </Card>
      </div>

      {/* Tree */}
      <Card>
        <CardHeader>
          <CardTitle className="flex items-center gap-2 text-base">
            <Network className="h-4 w-4" />
            Organisationsstruktur
          </CardTitle>
        </CardHeader>
        <CardContent>
          <div className="rounded-md border p-2">
            <TreeNodeRow
              node={tree}
              onUnlink={handleUnlink}
              isUnlinking={isUnlinking}
            />
          </div>
        </CardContent>
      </Card>

      {/* Link Account */}
      {availableAccounts.length > 0 && (
        <Card>
          <CardHeader>
            <CardTitle className="flex items-center gap-2 text-base">
              <Link2 className="h-4 w-4" />
              Organisation hinzufügen
            </CardTitle>
          </CardHeader>
          <CardContent>
            <div className="flex items-end gap-3">
              <div className="flex-1">
                <label
                  htmlFor="link-account"
                  className="text-muted-foreground mb-1 block text-sm"
                >
                  Verfügbare Organisationen
                </label>
                <select
                  id="link-account"
                  value={selectedAccountId}
                  onChange={(e) => setSelectedAccountId(e.target.value)}
                  className="border-input bg-background flex h-9 w-full rounded-md border px-3 py-1 text-sm shadow-sm"
                >
                  <option value="">Organisation auswählen...</option>
                  {availableAccounts.map((a) => (
                    <option key={a.id} value={a.id}>
                      {a.name}
                      {a.slug ? ` (/${a.slug})` : ''}
                    </option>
                  ))}
                </select>
              </div>
              <Button
                onClick={handleLink}
                disabled={!selectedAccountId || isLinking}
              >
                <Link2 className="mr-2 h-4 w-4" />
                {isLinking ? 'Wird verknüpft...' : 'Verknüpfen'}
              </Button>
            </div>
          </CardContent>
        </Card>
      )}
    </div>
  );
}