import { useEffect, useMemo, useRef, useState } from 'react';
import { Link } from 'react-router-dom';
import { nip19 } from 'nostr-tools';
import { formatDistanceToNow } from 'date-fns';
import { Lock, Send, Loader2, ShieldCheck, MessageSquare } from 'lucide-react';

import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
import { Button } from '@/components/ui/button';
import { Textarea } from '@/components/ui/textarea';
import { Avatar, AvatarFallback, AvatarImage } from '@/components/ui/avatar';
import { Badge } from '@/components/ui/badge';
import { Skeleton } from '@/components/ui/skeleton';

import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useAuthor } from '@/hooks/useAuthor';
import { useToast } from '@/hooks/useToast';
import {
  useGroupConversation,
  useSendDirectMessage,
  type DirectMessage,
} from '@/hooks/useDirectMessages';
import { genUserName } from '@/lib/genUserName';
import { cn } from '@/lib/utils';

interface CrewChatProps {
  crewName: string;
  /** The crew founder pubkey. */
  founderPubkey: string;
  /** All listed member pubkeys (hex). */
  members: string[];
}

/** One message bubble, resolving the author's profile. */
function CrewMessageBubble({
  message,
  isOwn,
}: {
  message: DirectMessage;
  isOwn: boolean;
}) {
  const author = useAuthor(message.pubkey);
  const meta = author.data?.metadata;
  const name = meta?.name ?? genUserName(message.pubkey);
  const npub = useMemo(() => nip19.npubEncode(message.pubkey), [message.pubkey]);
  const timeAgo = formatDistanceToNow(new Date(message.createdAt * 1000), { addSuffix: true });

  return (
    <div className={cn('flex gap-2.5', isOwn && 'flex-row-reverse')}>
      <Link to={`/${npub}`} className="shrink-0">
        <Avatar className="h-8 w-8">
          <AvatarImage src={meta?.picture} alt={name} />
          <AvatarFallback className="text-xs bg-teal-900/40 text-teal-300">
            {name.slice(0, 2).toUpperCase()}
          </AvatarFallback>
        </Avatar>
      </Link>
      <div className={cn('flex max-w-[78%] flex-col gap-0.5', isOwn && 'items-end')}>
        <div className={cn('flex items-baseline gap-2', isOwn && 'flex-row-reverse')}>
          <Link to={`/${npub}`} className="text-xs font-semibold hover:underline truncate max-w-[10rem]">
            {name}
          </Link>
          <span className="text-[10px] text-muted-foreground shrink-0">{timeAgo}</span>
        </div>
        <div
          className={cn(
            'rounded-2xl px-3 py-2 text-sm break-words whitespace-pre-wrap',
            isOwn ? 'bg-teal-500 text-black rounded-tr-sm' : 'bg-muted rounded-tl-sm',
          )}
        >
          {message.content}
        </div>
      </div>
    </div>
  );
}

export function CrewChat({ crewName, founderPubkey, members }: CrewChatProps) {
  const { user } = useCurrentUser();
  const { toast } = useToast();
  const [draft, setDraft] = useState('');
  const scrollRef = useRef<HTMLDivElement>(null);

  // The chat participants = founder + all listed members (deduped).
  const participants = useMemo(
    () => Array.from(new Set([founderPubkey, ...members])),
    [founderPubkey, members],
  );

  // Only crew members (founder or a listed member) can read/write the chat,
  // because NIP-17 group messages are end-to-end encrypted to the participants.
  const isMember = !!user && participants.includes(user.pubkey);

  const { data: messages, isLoading } = useGroupConversation(isMember ? participants : []);
  const { mutateAsync: sendMessage, isPending } = useSendDirectMessage();

  // Auto-scroll to newest message when the list grows.
  const lastCount = useRef(0);
  useEffect(() => {
    const count = messages?.length ?? 0;
    if (count !== lastCount.current) {
      lastCount.current = count;
      scrollRef.current?.scrollTo({ top: scrollRef.current.scrollHeight, behavior: 'smooth' });
    }
  }, [messages]);

  const canSendNip44 = !!user?.signer?.nip44;

  const handleSend = async (e: React.FormEvent) => {
    e.preventDefault();
    const text = draft.trim();
    if (!text || !user) return;

    if (!canSendNip44) {
      toast({
        title: 'Encryption unavailable',
        description: 'Your signer does not support NIP-44 encryption. Please upgrade your extension.',
        variant: 'destructive',
      });
      return;
    }

    // Recipients = everyone except yourself (the hook also wraps a copy to self).
    const recipients = participants.filter((p) => p !== user.pubkey);
    if (recipients.length === 0) {
      toast({
        title: 'No one to message yet',
        description: 'This crew has no other members to chat with.',
      });
      return;
    }

    try {
      await sendMessage({
        recipients,
        content: text,
        subject: `${crewName} crew chat`,
      });
      setDraft('');
    } catch (err) {
      toast({
        title: 'Message failed',
        description: err instanceof Error ? err.message : 'Could not send message.',
        variant: 'destructive',
      });
    }
  };

  return (
    <Card className="bg-black/90 border-2 border-teal-500/20 flex flex-col overflow-hidden">
      <CardHeader className="pb-3 border-b border-white/5">
        <div className="flex items-center justify-between gap-3">
          <CardTitle className="flex items-center gap-2 text-lg font-black uppercase text-white">
            <MessageSquare className="h-5 w-5 text-teal-400" /> Crew Chat
          </CardTitle>
          <Badge
            variant="outline"
            className="gap-1 border-teal-500/40 bg-teal-500/10 text-teal-400 text-[10px] font-bold uppercase tracking-wide"
            title="End-to-end encrypted — only crew members can read these messages."
          >
            <Lock className="h-3 w-3" />
            Private
          </Badge>
        </div>
        <p className="text-xs text-muted-foreground flex items-center gap-1 pt-0.5">
          <ShieldCheck className="h-3 w-3 text-teal-400 shrink-0" />
          Encrypted group chat for the founder &amp; all listed crew members.
        </p>
      </CardHeader>

      <CardContent className="p-0 flex flex-col flex-1 min-h-0">
        {!user ? (
          <div className="flex flex-col items-center justify-center gap-2 py-10 px-6 text-center">
            <Lock className="h-8 w-8 text-teal-400/40" />
            <p className="text-sm text-muted-foreground">Log in to see if you can join the crew chat.</p>
          </div>
        ) : !isMember ? (
          <div className="flex flex-col items-center justify-center gap-2 py-10 px-6 text-center">
            <Lock className="h-8 w-8 text-teal-400/40" />
            <p className="text-sm text-muted-foreground max-w-xs">
              This chat is private to crew members. Ask the founder to add you to the crew to join
              the conversation.
            </p>
          </div>
        ) : (
          <>
            <div
              ref={scrollRef}
              className="flex-1 overflow-y-auto px-4 py-3 space-y-3 min-h-[280px] max-h-[440px]"
            >
              {isLoading &&
                Array.from({ length: 3 }).map((_, i) => (
                  <div key={i} className="flex gap-2.5">
                    <Skeleton className="h-8 w-8 rounded-full" />
                    <div className="space-y-1.5">
                      <Skeleton className="h-3 w-24" />
                      <Skeleton className="h-8 w-40 rounded-2xl" />
                    </div>
                  </div>
                ))}
              {!isLoading && (!messages || messages.length === 0) && (
                <div className="flex h-full flex-col items-center justify-center text-center gap-2 py-8">
                  <MessageSquare className="h-8 w-8 text-muted-foreground/40" />
                  <p className="text-sm text-muted-foreground max-w-[16rem]">
                    No messages yet. Kick off the crew chat — plan a session, share a spot, hype a clip.
                  </p>
                </div>
              )}
              {messages?.map((m) => (
                <CrewMessageBubble key={m.id} message={m} isOwn={m.pubkey === user.pubkey} />
              ))}
            </div>

            <div className="border-t border-white/5 p-3">
              <form onSubmit={handleSend} className="flex items-end gap-2">
                <Textarea
                  value={draft}
                  onChange={(e) => setDraft(e.target.value)}
                  onKeyDown={(e) => {
                    if (e.key === 'Enter' && !e.shiftKey) {
                      e.preventDefault();
                      handleSend(e);
                    }
                  }}
                  placeholder="Message your crew…"
                  maxLength={2000}
                  rows={1}
                  className="flex-1 resize-none min-h-[40px] max-h-32"
                />
                <Button
                  type="submit"
                  size="icon"
                  disabled={isPending || !draft.trim()}
                  className="bg-teal-500 hover:bg-teal-600 text-black shrink-0"
                >
                  {isPending ? <Loader2 className="h-4 w-4 animate-spin" /> : <Send className="h-4 w-4" />}
                </Button>
              </form>
            </div>
          </>
        )}
      </CardContent>
    </Card>
  );
}