import { useMemo } from 'react';
import { ImageWithFallback } from '@/components/ImageWithFallback';
import { Link } from 'react-router-dom';
import { useSeoMeta } from '@unhead/react';
import { nip19 } from 'nostr-tools';
import { useQuery } from '@tanstack/react-query';
import { ArrowLeft, Radio, Calendar } from 'lucide-react';
import { Skeleton } from '@/components/ui/skeleton';
import { Avatar, AvatarImage, AvatarFallback } from '@/components/ui/avatar';
import { ZapButton } from '@/components/ZapButton';
import { NewsletterSubscribeButton } from '@/components/NewsletterSubscribeButton';
import { useSkateRelays } from '@/hooks/useSkateRelays';
import { useAuthor } from '@/hooks/useAuthor';
import { genUserName } from '@/lib/genUserName';
import { NEWSLETTER_KIND, parseNewsletterIssue, type SkateNewsletterIssue } from '@/lib/types';
import NotFound from '@/pages/NotFound';

/**
 * Very small, safe Markdown → React renderer for newsletter bodies.
 * Supports headings, bold, italics, links, list items and paragraphs — enough
 * for a newsletter without pulling in a full Markdown dependency. All text is
 * rendered as plain React text nodes (never dangerouslySetInnerHTML), and only
 * http(s) links are linkified, so there's no XSS surface from issue content.
 */
function renderMarkdown(md: string) {
  const lines = md.split('\n');
  const blocks: React.ReactNode[] = [];
  let key = 0;

  const renderInline = (text: string): React.ReactNode[] => {
    const nodes: React.ReactNode[] = [];
    // Tokenise **bold**, *italic*, and [label](url) / bare http(s) links.
    const regex = /(\*\*([^*]+)\*\*)|(\*([^*]+)\*)|(\[([^\]]+)\]\((https?:\/\/[^\s)]+)\))|(https?:\/\/[^\s]+)/g;
    let last = 0;
    let m: RegExpExecArray | null;
    let i = 0;
    while ((m = regex.exec(text)) !== null) {
      if (m.index > last) nodes.push(text.slice(last, m.index));
      if (m[1]) {
        nodes.push(<strong key={i++} className="font-black text-white">{m[2]}</strong>);
      } else if (m[3]) {
        nodes.push(<em key={i++} className="italic">{m[4]}</em>);
      } else if (m[5]) {
        nodes.push(
          <a key={i++} href={m[7]} target="_blank" rel="noopener noreferrer" className="text-[#ccff00] underline underline-offset-2 hover:opacity-80">
            {m[6]}
          </a>,
        );
      } else if (m[8]) {
        nodes.push(
          <a key={i++} href={m[8]} target="_blank" rel="noopener noreferrer" className="text-[#ccff00] underline underline-offset-2 hover:opacity-80 break-all">
            {m[8]}
          </a>,
        );
      }
      last = regex.lastIndex;
    }
    if (last < text.length) nodes.push(text.slice(last));
    return nodes;
  };

  let listBuffer: string[] = [];
  const flushList = () => {
    if (listBuffer.length === 0) return;
    blocks.push(
      <ul key={key++} className="my-4 list-disc space-y-1.5 pl-5 text-gray-300">
        {listBuffer.map((item, idx) => (
          <li key={idx}>{renderInline(item)}</li>
        ))}
      </ul>,
    );
    listBuffer = [];
  };

  for (const raw of lines) {
    const line = raw.trimEnd();
    if (/^\s*[-*]\s+/.test(line)) {
      listBuffer.push(line.replace(/^\s*[-*]\s+/, ''));
      continue;
    }
    flushList();
    if (line.trim() === '') continue;
    if (line.startsWith('### ')) {
      blocks.push(<h3 key={key++} className="mt-6 mb-2 text-lg font-black uppercase text-white">{renderInline(line.slice(4))}</h3>);
    } else if (line.startsWith('## ')) {
      blocks.push(<h2 key={key++} className="mt-8 mb-3 text-xl font-black uppercase text-white">{renderInline(line.slice(3))}</h2>);
    } else if (line.startsWith('# ')) {
      blocks.push(<h1 key={key++} className="mt-8 mb-3 text-2xl font-black uppercase text-white">{renderInline(line.slice(2))}</h1>);
    } else {
      blocks.push(<p key={key++} className="my-3 leading-relaxed text-gray-300">{renderInline(line)}</p>);
    }
  }
  flushList();
  return blocks;
}

export function NewsletterIssueView({ pubkey, identifier }: { pubkey: string; identifier: string }) {
  const { querySkateContent, getQueryKeySuffix } = useSkateRelays();
  const author = useAuthor(pubkey);

  const { data: issue, isLoading } = useQuery({
    queryKey: ['newsletter-issue', pubkey, identifier, getQueryKeySuffix()],
    staleTime: 5 * 60 * 1000,
    queryFn: async (c): Promise<SkateNewsletterIssue | null> => {
      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(6000)]);
      const events = await querySkateContent(
        [{ kinds: [NEWSLETTER_KIND], authors: [pubkey], '#d': [identifier], limit: 1 }],
        { signal },
      );
      for (const ev of events) {
        const parsed = parseNewsletterIssue(ev);
        if (parsed) return parsed;
      }
      return null;
    },
  });

  const body = useMemo(() => (issue ? renderMarkdown(issue.content) : null), [issue]);

  useSeoMeta({
    title: issue ? `${issue.title} - SkateSpots Newsletter` : 'Newsletter - SkateSpots',
    description: issue?.summary || 'A SkateSpots newsletter drop.',
    ...(issue?.image ? { ogImage: issue.image } : {}),
  });

  if (isLoading) {
    return (
      <>
        <div className="container max-w-2xl px-4 py-8">
          <Skeleton className="mb-6 h-6 w-32" />
          <Skeleton className="mb-4 aspect-video w-full rounded-2xl" />
          <Skeleton className="mb-3 h-10 w-3/4" />
          <div className="space-y-2">
            <Skeleton className="h-4 w-full" />
            <Skeleton className="h-4 w-5/6" />
            <Skeleton className="h-4 w-4/6" />
          </div>
        </div>
      </>
    );
  }

  // Not a valid / admin-authored newsletter issue → 404 (keeps the trust boundary).
  if (!issue) return <NotFound />;

  const authorName = author.data?.metadata?.name ?? genUserName(pubkey);
  const authorPic = author.data?.metadata?.picture;
  const date = new Date(issue.publishedAt * 1000).toLocaleDateString('en-US', {
    year: 'numeric',
    month: 'long',
    day: 'numeric',
  });

  return (
    <>
      <article className="container max-w-2xl px-4 py-8 pb-24 md:pb-14">
        <Link
          to="/newsletter"
          className="mb-6 inline-flex items-center gap-2 text-sm text-gray-400 transition-colors hover:text-[#ccff00]"
        >
          <ArrowLeft className="h-4 w-4" /> All issues
        </Link>

        <div className="mb-4 inline-flex items-center gap-2 rounded-full border border-[#ccff00]/30 bg-[#ccff00]/5 px-3 py-1.5 text-[10px] font-black uppercase tracking-widest text-[#ccff00]">
          <Radio className="h-3 w-3" /> SkateSpots Newsletter
        </div>

        {issue.image && (
          <div className="mb-6 aspect-video w-full overflow-hidden rounded-2xl border border-white/10">
            <ImageWithFallback src={issue.image} alt={issue.title} className="h-full w-full object-cover" />
          </div>
        )}

        <h1 className="mb-3 text-3xl font-black uppercase leading-tight text-white sm:text-4xl">
          {issue.title}
        </h1>

        <div className="mb-6 flex flex-wrap items-center gap-4 text-xs text-gray-500">
          <span className="flex items-center gap-1.5">
            <Calendar className="h-3.5 w-3.5" /> {date}
          </span>
          <Link to={`/${nip19.npubEncode(pubkey)}`} className="flex items-center gap-1.5 hover:text-gray-300">
            <Avatar className="h-5 w-5">
              <AvatarImage src={authorPic} alt={authorName} />
              <AvatarFallback className="text-[8px]">{authorName.slice(0, 2).toUpperCase()}</AvatarFallback>
            </Avatar>
            {authorName}
          </Link>
        </div>

        {issue.summary && (
          <p className="mb-6 border-l-2 border-[#ccff00]/40 pl-4 text-lg leading-relaxed text-gray-300">
            {issue.summary}
          </p>
        )}

        <div className="prose-invert">{body}</div>

        {/* Footer CTA: zap the issue + subscribe */}
        <div className="mt-10 flex flex-col items-center gap-4 rounded-2xl border-2 border-[#ccff00]/20 bg-white/[0.03] p-6 text-center">
          <p className="text-sm font-bold text-white">Dig the drop? Zap it and never miss the next one.</p>
          <div className="flex flex-wrap items-center justify-center gap-3">
            <ZapButton target={issue.event} className="bg-[#ccff00] font-bold text-black hover:bg-[#ccff00]/90" />
            <NewsletterSubscribeButton />
          </div>
        </div>
      </article>
    </>
  );
}