import { useState, useRef, useEffect, useMemo } from 'react';
import { useParams, Link } from 'react-router-dom';
import { useSeoMeta } from '@unhead/react';
import { Layout } from '@/components/Layout';
import { LoginArea } from '@/components/auth/LoginArea';
import { Card, CardContent } from '@/components/ui/card';
import { Button } from '@/components/ui/button';
import { Textarea } from '@/components/ui/textarea';
import { Skeleton } from '@/components/ui/skeleton';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useToast } from '@/hooks/useToast';
import { useNostrLogin } from '@nostrify/react/login';
import { hasNip44 as checkNip44 } from '@/lib/signerCapabilities';
import { useGroupConversation, useSendDirectMessage } from '@/hooks/useDirectMessages';
import { useAuthor } from '@/hooks/useAuthor';
import { genUserName } from '@/lib/genUserName';
import { formatDistanceToNow } from 'date-fns';
import { ArrowLeft, Lock, Loader2, RefreshCw, Send, Users } from 'lucide-react';
import { cn } from '@/lib/utils';

function ParticipantName({ pubkey }: { pubkey: string }) {
  const author = useAuthor(pubkey);
  const name = author.data?.metadata?.name ?? genUserName(pubkey);
  return <span className="truncate">{name}</span>;
}

/**
 * Group DM thread (NIP-17 fan-out group messaging).
 *
 * The URL carries the OTHER participants' hex pubkeys (comma-separated);
 * `useGroupConversation` takes the full set including us. This is the same
 * gift-wrap primitive as 1:1 DMs with one `p` tag per recipient.
 */
export default function GroupConversationPage() {
  const { participants: participantsParam } = useParams<{ participants: string }>();
  const { user } = useCurrentUser();
  const { logins } = useNostrLogin();
  const { toast } = useToast();
  const { mutate: sendMessage, isPending: isSending } = useSendDirectMessage();

  const [newMessage, setNewMessage] = useState('');
  const messagesEndRef = useRef<HTMLDivElement>(null);

  const otherPubkeys = useMemo(
    () => (participantsParam ? participantsParam.split(',').filter(Boolean) : []),
    [participantsParam],
  );
  const allParticipants = useMemo(
    () => (user ? [user.pubkey, ...otherPubkeys] : otherPubkeys),
    [user, otherPubkeys],
  );

  useSeoMeta({ title: 'Group chat - SkateSpots' });

  const { data: messages, isLoading, refetch, isRefetching } = useGroupConversation(allParticipants);

  useEffect(() => {
    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  }, [messages]);

  if (!participantsParam || otherPubkeys.length === 0) {
    return (
      <Layout>
        <div className="container mx-auto max-w-2xl px-4 py-16 text-center text-gray-400">
          This group chat link is invalid.
        </div>
      </Layout>
    );
  }

  if (!user) {
    return (
      <Layout>
        <div className="container mx-auto max-w-2xl px-4 py-8">
          <Card className="border-dashed border-2 border-gray-700">
            <CardContent className="py-16 text-center">
              <Lock className="mx-auto mb-4 h-16 w-16 text-gray-600" />
              <h2 className="mb-2 text-xl font-bold">Log in to view this group</h2>
              <div className="mt-6 flex justify-center">
                <LoginArea className="max-w-60" />
              </div>
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  if (!checkNip44(user, logins)) {
    return (
      <Layout>
        <div className="container mx-auto max-w-2xl px-4 py-12 text-center">
          <Card className="border-2 border-dashed border-orange-500/30">
            <CardContent className="py-12">
              <Lock className="mx-auto mb-4 h-12 w-12 text-orange-500" />
              <h2 className="mb-2 text-lg font-bold">Secure signer required</h2>
              <p className="text-sm text-gray-400">Group messages need a NIP-44 capable signer.</p>
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  const handleSend = () => {
    if (!newMessage.trim() || isSending) return;
    sendMessage(
      { recipients: otherPubkeys, content: newMessage.trim() },
      {
        onSuccess: () => setNewMessage(''),
        onError: (error) => {
          toast({
            title: 'Message failed to send',
            description: error instanceof Error ? error.message : 'Please try again in a moment.',
            variant: 'destructive',
          });
        },
      },
    );
  };

  return (
    <Layout>
      <div className="container mx-auto flex h-[calc(100dvh-56px-80px)] max-w-2xl flex-col px-4 py-2 sm:h-[calc(100dvh-64px-60px)] sm:py-4 md:h-[calc(100vh-64px-60px)]">
        {/* Header */}
        <div className="flex flex-shrink-0 items-center gap-2 border-b border-gray-800 pb-3 sm:gap-3 sm:pb-4">
          <Link to="/messages">
            <Button variant="ghost" size="icon" aria-label="Back" className="text-gray-400 hover:text-white">
              <ArrowLeft className="h-5 w-5" />
            </Button>
          </Link>
          <div className="flex h-9 w-9 flex-shrink-0 items-center justify-center rounded-full bg-[#ccff00]/15 text-[#ccff00]">
            <Users className="h-5 w-5" />
          </div>
          <div className="min-w-0 flex-1">
            <p className="truncate text-sm font-bold text-white sm:text-base">
              {otherPubkeys.length === 1 ? (
                <ParticipantName pubkey={otherPubkeys[0]} />
              ) : (
                `${otherPubkeys.length + 1} people`
              )}
            </p>
            <p className="flex items-center gap-1 text-[10px] text-gray-500 sm:text-xs">
              <Lock className="h-2.5 w-2.5 sm:h-3 sm:w-3" />
              End-to-end encrypted group
            </p>
          </div>
          <Button
            variant="ghost"
            size="icon"
            aria-label="Refresh"
            onClick={() => refetch()}
            disabled={isRefetching}
            className="text-gray-400 hover:text-white"
          >
            <RefreshCw className={cn('h-4 w-4', isRefetching && 'animate-spin')} />
          </Button>
        </div>

        {/* Messages */}
        <div className="flex-1 space-y-3 overflow-y-auto py-4">
          {isLoading ? (
            <>
              <Skeleton className="h-16 w-3/4 rounded-2xl" />
              <Skeleton className="ml-auto h-16 w-2/3 rounded-2xl" />
              <Skeleton className="h-16 w-3/4 rounded-2xl" />
            </>
          ) : messages && messages.length > 0 ? (
            messages.map((msg) => {
              const isMine = msg.pubkey === user.pubkey;
              return (
                <div key={msg.id} className={cn('flex flex-col', isMine ? 'items-end' : 'items-start')}>
                  {!isMine && (
                    <span className="mb-0.5 px-2 text-[10px] font-bold text-gray-500">
                      <ParticipantName pubkey={msg.pubkey} />
                    </span>
                  )}
                  <div
                    className={cn(
                      'max-w-[80%] break-words rounded-2xl px-3.5 py-2 text-sm',
                      isMine ? 'bg-[#ff0040] text-white' : 'bg-white/8 text-gray-100',
                    )}
                  >
                    {msg.content}
                  </div>
                  <span className="mt-0.5 px-2 text-[10px] text-gray-600">
                    {formatDistanceToNow(new Date(msg.createdAt * 1000), { addSuffix: true })}
                  </span>
                </div>
              );
            })
          ) : (
            <div className="py-10 text-center text-sm text-gray-500">
              No messages yet — say hi to the group.
            </div>
          )}
          <div ref={messagesEndRef} />
        </div>

        {/* Composer */}
        <div className="flex flex-shrink-0 gap-2 border-t border-gray-800 pb-safe pt-3 sm:pt-4">
          <Textarea
            value={newMessage}
            onChange={(e) => setNewMessage(e.target.value)}
            onKeyDown={(e) => {
              if (e.key === 'Enter' && !e.shiftKey) {
                e.preventDefault();
                handleSend();
              }
            }}
            placeholder="Message the group..."
            className="min-h-[44px] max-h-24 resize-none border-gray-700 bg-gray-900 text-sm text-white sm:max-h-32 sm:text-base"
            rows={1}
          />
          <Button
            onClick={handleSend}
            disabled={!newMessage.trim() || isSending}
            aria-label="Send message"
            className="h-[44px] w-[44px] flex-shrink-0 bg-[#ff0040] p-0 text-white hover:bg-[#ff0040]/90 sm:h-auto sm:w-auto sm:px-4"
          >
            {isSending ? <Loader2 className="h-5 w-5 animate-spin" /> : <Send className="h-5 w-5" />}
          </Button>
        </div>
      </div>
    </Layout>
  );
}