/**
 * Post detail — full view of one post with stats, thread context, and a
 * lazy-rendered image attachment.
 *
 * Why a dedicated screen?
 *  - PostCard in the timeline intentionally doesn't render attachments
 *    (would explode initial render time with N images).
 *  - Per-post stats (views, likes, liked_by_me) want a fresh refresh
 *    on open; timeline batches but not at the per-second cadence a
 *    reader expects when they just tapped in.
 *
 * Layout:
 *   [← back  ·  Пост]
 *   [PostCard (full — with attachment)]
 *   [stats bar: views · likes · fee]
 *   [— reply affordance below (future)]
 */
import React, { useCallback, useEffect, useState } from 'react';
import {
  View, Text, ScrollView, ActivityIndicator, Image,
} from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { router, useLocalSearchParams } from 'expo-router';

import { Header } from '@/components/Header';
import { IconButton } from '@/components/IconButton';
import { PostCard } from '@/components/feed/PostCard';
import { useStore } from '@/lib/store';
import {
  fetchPost, fetchStats, bumpView, formatCount, formatFee,
  type FeedPostItem, type PostStats,
} from '@/lib/feed';

export default function PostDetailScreen() {
  const { id: postID } = useLocalSearchParams<{ id: string }>();
  const keyFile = useStore(s => s.keyFile);

  const [post, setPost]   = useState<FeedPostItem | null>(null);
  const [stats, setStats] = useState<PostStats | null>(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  const load = useCallback(async () => {
    if (!postID) return;
    setLoading(true);
    setError(null);
    try {
      const [p, s] = await Promise.all([
        fetchPost(postID),
        fetchStats(postID, keyFile?.pub_key),
      ]);
      setPost(p);
      setStats(s);
      if (p) bumpView(postID);  // fire-and-forget
    } catch (e: any) {
      setError(String(e?.message ?? e));
    } finally {
      setLoading(false);
    }
  }, [postID, keyFile]);

  useEffect(() => { load(); }, [load]);

  const onStatsChanged = useCallback(async () => {
    if (!postID) return;
    const s = await fetchStats(postID, keyFile?.pub_key);
    if (s) setStats(s);
  }, [postID, keyFile]);

  const onDeleted = useCallback(() => {
    // Go back to feed — the post is gone.
    router.back();
  }, []);

  return (
    <View style={{ flex: 1, backgroundColor: '#000000' }}>
      <Header
        divider
        left={<IconButton icon="chevron-back" size={36} onPress={() => router.back()} />}
        title="Пост"
      />

      {loading ? (
        <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
          <ActivityIndicator color="#1d9bf0" />
        </View>
      ) : error ? (
        <View style={{ padding: 24 }}>
          <Text style={{ color: '#f4212e' }}>{error}</Text>
        </View>
      ) : !post ? (
        <View style={{ padding: 24, alignItems: 'center' }}>
          <Ionicons name="trash-outline" size={32} color="#6a6a6a" />
          <Text style={{ color: '#8b8b8b', marginTop: 10 }}>
            Пост удалён или больше недоступен
          </Text>
        </View>
      ) : (
        <ScrollView>
          <PostCard
            post={{ ...post, likes: stats?.likes ?? post.likes, views: stats?.views ?? post.views }}
            likedByMe={stats?.liked_by_me ?? false}
            onStatsChanged={onStatsChanged}
            onDeleted={onDeleted}
          />

          {/* Attachment preview (if any). For MVP we try loading from the
              CURRENT node — works when you're connected to the hosting
              relay. Cross-relay discovery (look up hosting_relay URL via
              /api/relays) is future work. */}
          {post.has_attachment && (
            <AttachmentPreview postID={post.post_id} />
          )}

          {/* Detailed stats block */}
          <View
            style={{
              marginHorizontal: 14,
              marginTop: 12,
              paddingVertical: 14,
              paddingHorizontal: 14,
              borderRadius: 14,
              backgroundColor: '#0a0a0a',
              borderWidth: 1,
              borderColor: '#1f1f1f',
            }}
          >
            <Text style={{
              color: '#5a5a5a',
              fontSize: 11,
              fontWeight: '700',
              letterSpacing: 1.2,
              textTransform: 'uppercase',
              marginBottom: 10,
            }}>
              Информация о посте
            </Text>

            <DetailRow label="Просмотров" value={formatCount(stats?.views ?? post.views)} />
            <DetailRow label="Лайков"     value={formatCount(stats?.likes ?? post.likes)} />
            <DetailRow label="Размер"     value={`${Math.round(post.size / 1024 * 10) / 10} KB`} />
            <DetailRow
              label="Стоимость публикации"
              value={formatFee(1000 + post.size)}
            />
            <DetailRow
              label="Хостинг"
              value={shortAddr(post.hosting_relay)}
              mono
            />

            {post.hashtags && post.hashtags.length > 0 && (
              <>
                <View style={{ height: 1, backgroundColor: '#1f1f1f', marginVertical: 10 }} />
                <Text style={{ color: '#5a5a5a', fontSize: 11, marginBottom: 6 }}>
                  Хештеги
                </Text>
                <View style={{ flexDirection: 'row', flexWrap: 'wrap', gap: 6 }}>
                  {post.hashtags.map(tag => (
                    <Text
                      key={tag}
                      onPress={() => router.push(`/(app)/feed/tag/${encodeURIComponent(tag)}` as never)}
                      style={{
                        color: '#1d9bf0',
                        fontSize: 13,
                        paddingHorizontal: 8,
                        paddingVertical: 3,
                        backgroundColor: '#081a2a',
                        borderRadius: 999,
                      }}
                    >
                      #{tag}
                    </Text>
                  ))}
                </View>
              </>
            )}
          </View>

          <View style={{ height: 80 }} />
        </ScrollView>
      )}
    </View>
  );
}

function DetailRow({ label, value, mono }: { label: string; value: string; mono?: boolean }) {
  return (
    <View style={{ flexDirection: 'row', paddingVertical: 3 }}>
      <Text style={{ color: '#8b8b8b', fontSize: 13, flex: 1 }}>{label}</Text>
      <Text
        style={{
          color: '#ffffff',
          fontSize: 13,
          fontWeight: '600',
          fontFamily: mono ? 'monospace' : undefined,
        }}
      >
        {value}
      </Text>
    </View>
  );
}

function AttachmentPreview({ postID }: { postID: string }) {
  // For MVP we hit the local node URL; if the body is hosted elsewhere
  // the image load will fail and the placeholder stays visible.
  const { getNodeUrl } = require('@/lib/api');
  const url = `${getNodeUrl()}/feed/post/${postID}`;
  // The body is a JSON object, not raw image bytes. For now we just
  // show a placeholder — decoding base64 attachment → data-uri is a
  // Phase D improvement once we add /feed/post/{id}/attachment raw bytes.
  return (
    <View
      style={{
        margin: 14,
        paddingVertical: 32,
        borderRadius: 14,
        backgroundColor: '#0a0a0a',
        borderWidth: 1,
        borderColor: '#1f1f1f',
        alignItems: 'center',
      }}
    >
      <Ionicons name="image-outline" size={32} color="#5a5a5a" />
      <Text style={{ color: '#8b8b8b', marginTop: 10, fontSize: 12 }}>
        Вложение: {url}
      </Text>
      <Text style={{ color: '#5a5a5a', marginTop: 4, fontSize: 10 }}>
        Прямой просмотр вложений — в следующем релизе
      </Text>
    </View>
  );
}

function shortAddr(a: string, n = 6): string {
  if (!a) return '—';
  return a.length <= n * 2 + 1 ? a : `${a.slice(0, n)}…${a.slice(-n)}`;
}

// Silence Image import when unused (reserved for future attachment preview).
void Image;