import { useState, useRef, useEffect } from 'react';
import { useParams, Link, useSearchParams } from 'react-router-dom';
import { useSeoMeta } from '@unhead/react';
import { nip19 } from 'nostr-tools';
import { Layout } from '@/components/Layout';
import { Card, CardContent } from '@/components/ui/card';
import { Button } from '@/components/ui/button';
import { Textarea } from '@/components/ui/textarea';
import { Avatar, AvatarImage, AvatarFallback } from '@/components/ui/avatar';
import { Skeleton } from '@/components/ui/skeleton';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useNostrLogin } from '@nostrify/react/login';
import { hasNip44 as checkNip44 } from '@/lib/signerCapabilities';
import { useConversation, useSendDirectMessage, type DirectMessage } from '@/hooks/useDirectMessages';
import { useDMRead } from '@/hooks/useDMRead';
import { useAuthor } from '@/hooks/useAuthor';
import { genUserName } from '@/lib/genUserName';
import { formatDistanceToNow } from 'date-fns';
import {
  ArrowLeft,
  Send,
  Lock,
  Loader2,
  AlertCircle,
  RefreshCw,
} from 'lucide-react';
import { cn } from '@/lib/utils';
import { AmberApprovalHint } from '@/components/AmberApprovalHint';
import NotFound from './NotFound';

// Single message bubble
function MessageBubble({ message, isFromMe }: { message: DirectMessage; isFromMe: boolean }) {
  const timeAgo = formatDistanceToNow(new Date(message.createdAt * 1000), { addSuffix: true });

  return (
    <div className={cn(
      "flex",
      isFromMe ? "justify-end" : "justify-start"
    )}>
      <div className={cn(
        "max-w-[85%] sm:max-w-[80%] rounded-2xl px-3 py-2 sm:px-4",
        isFromMe 
          ? "bg-[#ff0040] text-white rounded-br-sm" 
          : "bg-gray-800 text-white rounded-bl-sm"
      )}>
        <p className="whitespace-pre-wrap break-words text-sm sm:text-base">{message.content}</p>
        <p className={cn(
          "text-[10px] sm:text-xs mt-1",
          isFromMe ? "text-white/60" : "text-gray-500"
        )}>
          {timeAgo}
        </p>
      </div>
    </div>
  );
}

function MessageSkeleton({ isFromMe }: { isFromMe: boolean }) {
  return (
    <div className={cn("flex", isFromMe ? "justify-end" : "justify-start")}>
      <Skeleton className={cn(
        "rounded-2xl h-16",
        isFromMe ? "w-48" : "w-64"
      )} />
    </div>
  );
}

export default function ConversationPage() {
  const { npub } = useParams<{ npub: string }>();
  const [searchParams] = useSearchParams();
  const { user } = useCurrentUser();
  const { logins } = useNostrLogin();
  const messagesEndRef = useRef<HTMLDivElement>(null);
  
  // Support pre-filled message from URL query param
  const prefillMessage = searchParams.get('message') || '';
  const [newMessage, setNewMessage] = useState('');
  
  // Set pre-filled message when URL param changes
  useEffect(() => {
    if (prefillMessage) {
      setNewMessage(prefillMessage);
    }
  }, [prefillMessage]);

  // Decode npub to get pubkey
  let otherPubkey: string | null = null;
  try {
    if (npub?.startsWith('npub1')) {
      const decoded = nip19.decode(npub);
      if (decoded.type === 'npub') {
        otherPubkey = decoded.data;
      }
    }
  } catch {
    // Invalid npub
  }

  const { data: messages, isLoading, error, refetch, isRefetching } = useConversation(otherPubkey || '');
  const { mutate: sendMessage, isPending: isSending } = useSendDirectMessage();
  const { markRead } = useDMRead();
  const author = useAuthor(otherPubkey || undefined);
  const metadata = author.data?.metadata;
  const displayName = metadata?.name ?? (otherPubkey ? genUserName(otherPubkey) : 'Unknown');
  const avatar = metadata?.picture;

  useSeoMeta({
    title: `Chat with ${displayName} - SkateSpots`,
    description: 'Private encrypted conversation',
  });

  // Scroll to bottom when messages change
  useEffect(() => {
    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  }, [messages]);

  // Viewing a conversation marks it read up to its newest message, so the
  // unread dot on the inbox clears the moment you open it.
  useEffect(() => {
    if (!otherPubkey || !messages || messages.length === 0) return;
    const newest = messages.reduce((max, m) => Math.max(max, m.createdAt), 0);
    markRead(otherPubkey, newest);
  }, [otherPubkey, messages, markRead]);

  const handleSend = () => {
    if (!newMessage.trim() || !otherPubkey || isSending) return;

    sendMessage(
      { recipients: otherPubkey, content: newMessage.trim() },
      {
        onSuccess: () => {
          setNewMessage('');
        },
      }
    );
  };

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      handleSend();
    }
  };

  // Invalid npub
  if (!otherPubkey) {
    return <NotFound />;
  }

  // Not logged in
  if (!user) {
    return (
      <Layout>
        <div className="container px-4 py-8">
          <Card className="border-dashed border-2 border-gray-700">
            <CardContent className="py-16 text-center">
              <Lock className="h-16 w-16 mx-auto mb-4 text-gray-600" />
              <h2 className="text-xl font-bold mb-2">Log in to view messages</h2>
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  // Check NIP-44 support
  if (!checkNip44(user, logins)) {
    const isAndroid = /Android/i.test(navigator.userAgent);
    const isMobile = isAndroid || /iPhone|iPad|iPod/i.test(navigator.userAgent);
    
    return (
      <Layout>
        <div className="container px-4 py-8">
          <Card className="border-dashed border-2 border-orange-500/30">
            <CardContent className="py-12 text-center px-4">
              <AlertCircle className="h-12 w-12 mx-auto mb-4 text-orange-500" />
              <h2 className="text-lg font-bold mb-2">Secure Login Required</h2>
              <p className="text-gray-400 text-sm mb-3">
                Messages require a secure signer app.
              </p>
              {isMobile && isAndroid && (
                <a 
                  href="https://github.com/greenart7c3/Amber"
                  target="_blank"
                  rel="noopener noreferrer"
                  className="inline-flex items-center gap-2 px-4 py-2 rounded-full bg-[#ccff00] text-black font-bold text-sm"
                >
                  Get Amber →
                </a>
              )}
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  return (
    <Layout>
      <div className="container px-4 py-2 sm:py-4 max-w-2xl h-[calc(100dvh-56px-80px)] sm:h-[calc(100dvh-64px-60px)] md:h-[calc(100vh-64px-60px)] flex flex-col">
        {/* Header */}
        <div className="flex items-center gap-2 sm:gap-3 pb-3 sm:pb-4 border-b border-gray-800 flex-shrink-0">
          <Link to="/messages">
            <Button variant="ghost" size="icon" className="text-gray-400 hover:text-white">
              <ArrowLeft className="h-5 w-5" />
            </Button>
          </Link>
          <Avatar className="h-8 w-8 sm:h-10 sm:w-10 border-2 border-gray-700 flex-shrink-0">
            <AvatarImage src={avatar} alt={displayName} />
            <AvatarFallback className="bg-[#ff0040]/20 text-[#ff0040] text-xs sm:text-sm">
              {displayName.slice(0, 2).toUpperCase()}
            </AvatarFallback>
          </Avatar>
          <div className="flex-1 min-w-0">
            <p className="font-bold text-white truncate text-sm sm:text-base">{displayName}</p>
            <p className="text-[10px] sm:text-xs text-gray-500 flex items-center gap-1">
              <Lock className="h-2.5 w-2.5 sm:h-3 sm:w-3" />
              Encrypted
            </p>
          </div>
          <Button
            variant="ghost"
            size="icon"
            onClick={() => refetch()}
            disabled={isRefetching}
            className="text-gray-400 hover:text-white"
          >
            <RefreshCw className={cn("h-4 w-4", isRefetching && "animate-spin")} />
          </Button>
        </div>

        {/* Messages Area */}
        <div className="flex-1 overflow-y-auto py-3 sm:py-4 space-y-2 sm:space-y-3 min-h-0">
          {isLoading ? (
            <>
              <MessageSkeleton isFromMe={false} />
              <MessageSkeleton isFromMe={true} />
              <MessageSkeleton isFromMe={false} />
            </>
          ) : error ? (
            <div className="text-center py-8">
              <AlertCircle className="h-12 w-12 mx-auto mb-3 text-red-500" />
              <p className="text-gray-400">Failed to load messages</p>
              <Button
                variant="outline"
                onClick={() => refetch()}
                className="mt-4 border-gray-700"
              >
                Try Again
              </Button>
            </div>
          ) : messages && messages.length > 0 ? (
            messages.map((msg) => (
              <MessageBubble
                key={msg.id}
                message={msg}
                isFromMe={msg.pubkey === user.pubkey}
              />
            ))
          ) : (
            <div className="text-center py-12">
              <p className="text-gray-500">No messages yet</p>
              <p className="text-gray-600 text-sm mt-1">
                Send a message to start the conversation
              </p>
            </div>
          )}
          <div ref={messagesEndRef} />
        </div>

        {/* Message Input */}
        <div className="pt-3 sm:pt-4 border-t border-gray-800 flex-shrink-0 pb-safe">
          <div className="flex gap-2">
            <Textarea
              value={newMessage}
              onChange={(e) => setNewMessage(e.target.value)}
              onKeyDown={handleKeyDown}
              placeholder="Type a message..."
              className="bg-gray-900 border-gray-700 text-white resize-none min-h-[44px] max-h-24 sm:max-h-32 text-sm sm:text-base"
              rows={1}
            />
            <Button
              onClick={handleSend}
              disabled={!newMessage.trim() || isSending}
              className="bg-[#ff0040] hover:bg-[#ff0040]/90 text-white h-[44px] w-[44px] sm:h-auto sm:w-auto p-0 sm:px-4 flex-shrink-0"
            >
              {isSending ? (
                <Loader2 className="h-5 w-5 animate-spin" />
              ) : (
                <Send className="h-5 w-5" />
              )}
            </Button>
          </div>
          <p className="text-[10px] sm:text-xs text-gray-600 mt-1.5 sm:mt-2 text-center hidden sm:block">
            Messages are end-to-end encrypted using NIP-17
          </p>
          {/* A 1:1 NIP-17 DM encrypts + signs to the recipient AND to yourself
              (so you keep a copy) = up to 4 signer approvals. Warn Amber users. */}
          <AmberApprovalHint approvals={4} action="send this message" className="mt-1.5 justify-center" />
        </div>
      </div>
    </Layout>
  );
}