import { useState } from 'react';
import { Link } 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 { Input } from '@/components/ui/input';
import { Avatar, AvatarImage, AvatarFallback } from '@/components/ui/avatar';
import { Skeleton } from '@/components/ui/skeleton';
import { Badge } from '@/components/ui/badge';
import {
  Dialog,
  DialogContent,
  DialogHeader,
  DialogTitle,
  DialogDescription,
} from '@/components/ui/dialog';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useConversations, formatPubkeyShort } from '@/hooks/useDirectMessages';
import { useAuthor } from '@/hooks/useAuthor';
import { genUserName } from '@/lib/genUserName';
import { useLocalStorage } from '@/hooks/useLocalStorage';
import { formatDistanceToNow } from 'date-fns';
import {
  MessageCircle,
  Plus,
  Search,
  Lock,
  AlertCircle,
  ShieldCheck,
  X,
} from 'lucide-react';
import { cn } from '@/lib/utils';

/**
 * Dismissible phishing-warning banner shown once at the top of the DM page.
 * Standard practice (Alby, Metamask, Muun) — protects users from social-engineering
 * attacks where a bad actor pretends to be "SkateSpots Support" via DM.
 */
function PhishingWarningBanner() {
  const [dismissed, setDismissed] = useLocalStorage<boolean>('dm-phishing-warning-dismissed', false);

  if (dismissed) return null;

  return (
    <div className="flex items-start gap-3 px-4 py-3 mb-4 rounded-xl border border-[#ccff00]/30 bg-[#ccff00]/5 text-sm">
      <ShieldCheck className="h-5 w-5 text-[#ccff00] flex-shrink-0 mt-0.5" />
      <div className="flex-1 min-w-0">
        <p className="text-[#ccff00] font-bold text-xs uppercase tracking-wide mb-0.5">
          Security reminder
        </p>
        <p className="text-gray-300 text-xs leading-relaxed">
          <strong className="text-white">SkateSpots will never DM you</strong> asking to verify your account,
          share your keys, or send payments. If someone claims to be SkateSpots support via DM — it&apos;s a scam.
        </p>
      </div>
      <button
        onClick={() => setDismissed(true)}
        className="flex-shrink-0 text-gray-500 hover:text-gray-300 transition-colors p-0.5 mt-0.5"
        aria-label="Dismiss security reminder"
      >
        <X className="h-4 w-4" />
      </button>
    </div>
  );
}

// Conversation preview component
function ConversationPreview({ pubkey, lastMessage }: { 
  pubkey: string; 
  lastMessage?: { content: string; createdAt: number; pubkey: string };
}) {
  const author = useAuthor(pubkey);
  const { user } = useCurrentUser();
  const metadata = author.data?.metadata;
  const displayName = metadata?.name ?? genUserName(pubkey);
  const avatar = metadata?.picture;

  const isFromMe = lastMessage?.pubkey === user?.pubkey;
  const timeAgo = lastMessage 
    ? formatDistanceToNow(new Date(lastMessage.createdAt * 1000), { addSuffix: true })
    : '';

  return (
    <Link to={`/messages/${nip19.npubEncode(pubkey)}`}>
      <Card className={cn(
        "hover:bg-gray-900/50 transition-colors cursor-pointer border-gray-800",
        "hover:border-[#ff0040]/50 active:scale-[0.99]"
      )}>
        <CardContent className="p-3 sm:p-4">
          <div className="flex items-center gap-2.5 sm:gap-3">
            <Avatar className="h-10 w-10 sm:h-12 sm:w-12 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">
              <div className="flex items-center justify-between gap-2">
                <p className="font-bold text-white truncate text-sm sm:text-base">{displayName}</p>
                {timeAgo && (
                  <span className="text-[10px] sm:text-xs text-gray-500 flex-shrink-0">{timeAgo}</span>
                )}
              </div>
              {lastMessage && (
                <p className="text-xs sm:text-sm text-gray-400 truncate">
                  {isFromMe && <span className="text-gray-500">You: </span>}
                  {lastMessage.content}
                </p>
              )}
            </div>
          </div>
        </CardContent>
      </Card>
    </Link>
  );
}

function ConversationSkeleton() {
  return (
    <Card className="border-gray-800">
      <CardContent className="p-4">
        <div className="flex items-center gap-3">
          <Skeleton className="h-12 w-12 rounded-full" />
          <div className="flex-1 space-y-2">
            <Skeleton className="h-4 w-32" />
            <Skeleton className="h-3 w-48" />
          </div>
        </div>
      </CardContent>
    </Card>
  );
}

export default function DirectMessagesPage() {
  const { user } = useCurrentUser();
  const { data: conversations, isLoading, error } = useConversations();
  const [showNewMessage, setShowNewMessage] = useState(false);
  const [newRecipient, setNewRecipient] = useState('');
  const [recipientError, setRecipientError] = useState('');

  useSeoMeta({
    title: 'Messages - SkateSpots',
    description: 'Private encrypted messages with the skateboarding community',
  });

  const handleStartConversation = () => {
    setRecipientError('');
    
    // Try to parse the input as npub or hex pubkey
    let pubkey = newRecipient.trim();
    
    try {
      if (pubkey.startsWith('npub1')) {
        const decoded = nip19.decode(pubkey);
        if (decoded.type === 'npub') {
          pubkey = decoded.data;
        } else {
          throw new Error('Invalid npub');
        }
      } else if (!/^[a-f0-9]{64}$/i.test(pubkey)) {
        throw new Error('Invalid pubkey format');
      }
      
      // Navigate to conversation
      window.location.href = `/messages/${nip19.npubEncode(pubkey)}`;
    } catch {
      setRecipientError('Please enter a valid npub or pubkey');
    }
  };

  // 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 access messages</h2>
              <p className="text-gray-400">
                Private, encrypted messaging with skaters in the community
              </p>
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  // Check if NIP-44 is available
  if (!user.signer?.nip44) {
    const isAndroid = /Android/i.test(navigator.userAgent);
    const isIOS = /iPhone|iPad|iPod/i.test(navigator.userAgent);
    const isMobile = isAndroid || isIOS;
    
    return (
      <Layout>
        <div className="container px-4 py-8">
          <Card className="border-dashed border-2 border-orange-500/30">
            <CardContent className="py-12 sm:py-16 text-center px-4">
              <AlertCircle className="h-12 w-12 sm:h-16 sm:w-16 mx-auto mb-4 text-orange-500" />
              <h2 className="text-lg sm:text-xl font-bold mb-2">Secure Login Required</h2>
              <p className="text-gray-400 mb-4 text-sm sm:text-base">
                Private messages require a secure signer app to encrypt your conversations.
              </p>
              {isMobile ? (
                <div className="space-y-3">
                  {isAndroid && (
                    <div className="p-4 rounded-lg bg-[#ccff00]/10 border border-[#ccff00]/30">
                      <p className="text-sm text-gray-300 mb-3">
                        <strong className="text-[#ccff00]">On Android:</strong> Use the Amber app
                      </p>
                      <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>
                    </div>
                  )}
                  {isIOS && (
                    <div className="p-4 rounded-lg bg-blue-500/10 border border-blue-500/30">
                      <p className="text-sm text-gray-300">
                        <strong className="text-blue-400">On iOS:</strong> Try logging in with a bunker connection (nsec.app) from Settings
                      </p>
                    </div>
                  )}
                </div>
              ) : (
                <p className="text-sm text-gray-500">
                  Try logging in with a browser extension like Alby or nos2x that supports encryption.
                </p>
              )}
            </CardContent>
          </Card>
        </div>
      </Layout>
    );
  }

  return (
    <Layout>
      <div className="container px-4 py-4 sm:py-8 max-w-2xl">
        {/* Phishing warning — shown once, dismissible */}
        <PhishingWarningBanner />

        {/* Header */}
        <div className="flex items-center justify-between gap-3 mb-4 sm:mb-6">
          <div className="min-w-0 flex-1">
            <h1 className="text-xl sm:text-2xl font-black uppercase tracking-wider flex items-center gap-2 sm:gap-3">
              <MessageCircle className="h-5 w-5 sm:h-7 sm:w-7 text-[#ff0040] flex-shrink-0" />
              <span className="truncate">MESSAGES</span>
            </h1>
            <p className="text-gray-400 text-xs sm:text-sm mt-1 flex items-center gap-1">
              <Lock className="h-2.5 w-2.5 sm:h-3 sm:w-3" />
              <span className="hidden xs:inline">End-to-end encrypted with NIP-17</span>
              <span className="xs:hidden">Encrypted</span>
            </p>
          </div>
          <Button
            onClick={() => setShowNewMessage(true)}
            className="bg-[#ff0040] hover:bg-[#ff0040]/90 text-white font-bold flex-shrink-0 h-10 sm:h-auto px-3 sm:px-4"
          >
            <Plus className="h-4 w-4 sm:mr-2" />
            <span className="hidden sm:inline">New Message</span>
          </Button>
        </div>

        {/* Conversations List */}
        <div className="space-y-3">
          {isLoading ? (
            <>
              <ConversationSkeleton />
              <ConversationSkeleton />
              <ConversationSkeleton />
            </>
          ) : error ? (
            <Card className="border-red-500/30">
              <CardContent className="py-8 text-center">
                <AlertCircle className="h-12 w-12 mx-auto mb-3 text-red-500" />
                <p className="text-gray-400">Failed to load messages</p>
              </CardContent>
            </Card>
          ) : conversations && conversations.length > 0 ? (
            conversations.map((conv) => (
              <ConversationPreview
                key={conv.pubkey}
                pubkey={conv.pubkey}
                lastMessage={conv.lastMessage}
              />
            ))
          ) : (
            <Card className="border-dashed border-2 border-gray-700">
              <CardContent className="py-12 text-center">
                <MessageCircle className="h-16 w-16 mx-auto mb-4 text-gray-600" />
                <h2 className="text-xl font-bold mb-2">No messages yet</h2>
                <p className="text-gray-400 mb-6">
                  Start a conversation with someone in the community
                </p>
                <Button
                  onClick={() => setShowNewMessage(true)}
                  className="bg-[#ff0040] hover:bg-[#ff0040]/90 text-white font-bold"
                >
                  <Plus className="h-4 w-4 mr-2" />
                  Start a Conversation
                </Button>
              </CardContent>
            </Card>
          )}
        </div>
      </div>

      {/* New Message Dialog */}
      <Dialog open={showNewMessage} onOpenChange={setShowNewMessage}>
        <DialogContent className="bg-black border-2 border-[#ff0040]/50 mx-4 max-w-[calc(100vw-2rem)] sm:max-w-lg">
          <DialogHeader>
            <DialogTitle className="flex items-center gap-2 text-white">
              <MessageCircle className="h-5 w-5 text-[#ff0040]" />
              New Message
            </DialogTitle>
            <DialogDescription className="text-gray-400 text-sm">
              Enter the npub or pubkey of the person you want to message
            </DialogDescription>
          </DialogHeader>
          <div className="space-y-4 mt-4">
            <div className="space-y-2">
              <Input
                value={newRecipient}
                onChange={(e) => {
                  setNewRecipient(e.target.value);
                  setRecipientError('');
                }}
                placeholder="npub1... or hex pubkey"
                className="bg-black border-gray-700 text-white font-mono text-sm h-11"
              />
              {recipientError && (
                <p className="text-sm text-red-500">{recipientError}</p>
              )}
            </div>
            <div className="flex gap-2">
              <Button
                variant="outline"
                onClick={() => setShowNewMessage(false)}
                className="flex-1 border-gray-700 h-11"
              >
                Cancel
              </Button>
              <Button
                onClick={handleStartConversation}
                disabled={!newRecipient.trim()}
                className="flex-1 bg-[#ff0040] hover:bg-[#ff0040]/90 text-white font-bold h-11"
              >
                Start Chat
              </Button>
            </div>
          </div>
        </DialogContent>
      </Dialog>
    </Layout>
  );
}