import 'dart:collection';
import 'dart:convert';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:http/http.dart' as http;

import '../model/account_data.dart';
import '../model/endpoint_data.dart';

class UserAvatar extends StatefulWidget {
  final String id;
  final bool isGroup;
  final int size;

  /// Server-side pixel size requested for user avatars. `null` lets the
  /// widget pick `(size * 4).clamp(64, 1024)` — enough headroom for typical
  /// device pixel ratios. Group avatars ignore this (Spreed serves one
  /// fixed-size image per token).
  final int? requestSize;

  const UserAvatar({
    required this.id,
    this.isGroup = false,
    this.size = 20,
    this.requestSize,
    super.key,
  });

  @override
  State<UserAvatar> createState() => _UserAvatarState();
}

class _AvatarPayload {
  final Uint8List bytes;
  final bool isSvg;
  _AvatarPayload(this.bytes, this.isSvg);
}

class _AvatarCacheEntry {
  final _AvatarPayload? payload;
  final DateTime fetchedAt;
  _AvatarCacheEntry(this.payload, this.fetchedAt);
}

// LRU via LinkedHashMap insertion order + remove-on-hit. TTL so
// server-side avatar updates become visible within a session.
const int _kAvatarCacheMax = 256;
const Duration _kAvatarCacheTtl = Duration(minutes: 30);

// Pending map dedups concurrent mounts onto a single HTTP call.
final LinkedHashMap<String, _AvatarCacheEntry> _resolvedAvatars =
    LinkedHashMap<String, _AvatarCacheEntry>();
final Map<String, Future<_AvatarPayload?>> _pendingAvatars = {};

// Bumped by invalidateAvatarCache so *already mounted* avatars re-resolve.
// Clearing the cache map alone only affects future mounts — a UserAvatar
// elsewhere on screen (chat list, chat header) holds its bytes in State and
// would keep showing the stale image until rebuilt. Each state listens here
// and re-attaches: invalidated urls miss the cache and re-fetch, the rest
// hit the cache and cost nothing.
final ValueNotifier<int> _avatarCacheGeneration = ValueNotifier<int>(0);

String avatarUrl({required String id, required bool isGroup, int size = 512}) {
  final host = EndpointData().nextcloud().full();
  if (isGroup) {
    return 'https://$host/ocs/v2.php/apps/spreed/api/v1/room/$id/avatar';
  }
  return 'https://$host/avatar/$id/$size';
}

/// Drops cached avatar bytes so the next mount re-fetches from the server.
/// Call after the app uploaded or removed an avatar — without this the
/// 30-min TTL would mask the change for the rest of the session.
///
/// With [id]+[isGroup], invalidates every cached size for that subject
/// (user avatars cache per-size URL). Without arguments, clears everything.
/// Pending fetches are also discarded so a stale in-flight response can't
/// repopulate the cache.
void invalidateAvatarCache({String? id, bool? isGroup}) {
  if (id == null) {
    _resolvedAvatars.clear();
    _pendingAvatars.clear();
  } else if (isGroup == true) {
    final url = avatarUrl(id: id, isGroup: true);
    _resolvedAvatars.remove(url);
    _pendingAvatars.remove(url);
  } else {
    // User avatars include the rendered size in the URL — drop every variant.
    final host = EndpointData().nextcloud().full();
    final prefix = 'https://$host/avatar/$id/';
    _resolvedAvatars.removeWhere((url, _) => url.startsWith(prefix));
    _pendingAvatars.removeWhere((url, _) => url.startsWith(prefix));
  }
  _avatarCacheGeneration.value++;
}

_AvatarCacheEntry? _readAvatarCache(String url) {
  final entry = _resolvedAvatars.remove(url);
  if (entry == null) return null;
  if (DateTime.now().difference(entry.fetchedAt) > _kAvatarCacheTtl) {
    return null;
  }
  // Re-insert at the tail so it counts as most-recently-used.
  _resolvedAvatars[url] = entry;
  return entry;
}

void _writeAvatarCache(String url, _AvatarPayload? payload) {
  _resolvedAvatars.remove(url);
  _resolvedAvatars[url] = _AvatarCacheEntry(payload, DateTime.now());
  while (_resolvedAvatars.length > _kAvatarCacheMax) {
    _resolvedAvatars.remove(_resolvedAvatars.keys.first);
  }
}

class _UserAvatarState extends State<UserAvatar> {
  _AvatarPayload? _payload;

  @override
  void initState() {
    super.initState();
    _attach();
    _avatarCacheGeneration.addListener(_onCacheInvalidated);
  }

  @override
  void dispose() {
    _avatarCacheGeneration.removeListener(_onCacheInvalidated);
    super.dispose();
  }

  // Re-resolve when the cache generation changes. Cache hit → no network and
  // the visible bytes stay; cache miss (our url was invalidated) → re-fetch.
  void _onCacheInvalidated() {
    if (!mounted) return;
    setState(_attach);
  }

  @override
  void didUpdateWidget(UserAvatar oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.id != widget.id ||
        oldWidget.isGroup != widget.isGroup ||
        oldWidget.size != widget.size ||
        oldWidget.requestSize != widget.requestSize) {
      _attach();
    }
  }

  int _resolvedRequestSize() =>
      widget.requestSize ?? (widget.size * 4).clamp(64, 1024);

  String _url() => avatarUrl(
    id: widget.id,
    isGroup: widget.isGroup,
    size: _resolvedRequestSize(),
  );

  void _attach() {
    final url = _url();
    final cached = _readAvatarCache(url);
    if (cached != null) {
      _payload = cached.payload;
      return;
    }
    _payload = null;
    final pending = _pendingAvatars.putIfAbsent(url, () => _fetch(url));
    pending.then((p) {
      _writeAvatarCache(url, p);
      _pendingAvatars.remove(url);
      if (!mounted || _url() != url) return;
      setState(() => _payload = p);
    });
  }

  Future<_AvatarPayload?> _fetch(String url) async {
    try {
      final response = await http.get(
        Uri.parse(url),
        headers: {
          'Authorization': AccountData().getBasicAuthHeader(),
          'Accept': 'image/png,image/jpeg,image/webp,image/svg+xml',
        },
      );
      if (response.statusCode != 200 || response.bodyBytes.isEmpty) return null;

      final contentType = response.headers['content-type']?.toLowerCase() ?? '';
      final bytes = response.bodyBytes;
      final isSvg = contentType.contains('svg') || _looksLikeSvg(bytes);
      return _AvatarPayload(bytes, isSvg);
    } catch (_) {
      return null;
    }
  }

  static bool _looksLikeSvg(Uint8List bytes) {
    final head = utf8
        .decode(
          bytes.sublist(0, bytes.length < 256 ? bytes.length : 256),
          allowMalformed: true,
        )
        .trimLeft();
    return head.startsWith('<?xml') || head.startsWith('<svg');
  }

  @override
  Widget build(BuildContext context) {
    final radius = widget.size.toDouble();
    final theme = Theme.of(context);
    final payload = _payload;

    Widget content;
    if (payload != null) {
      if (payload.isSvg) {
        content = SvgPicture.memory(
          payload.bytes,
          width: radius * 2,
          height: radius * 2,
          fit: BoxFit.cover,
        );
      } else {
        content = Image.memory(
          payload.bytes,
          width: radius * 2,
          height: radius * 2,
          fit: BoxFit.cover,
          gaplessPlayback: true,
        );
      }
    } else {
      content = Icon(
        widget.isGroup ? Icons.group : Icons.person,
        size: radius,
        color: Colors.white,
      );
    }

    return CircleAvatar(
      radius: radius,
      backgroundColor: theme.primaryColor,
      foregroundColor: Colors.white,
      child: ClipOval(
        child: SizedBox(
          width: radius * 2,
          height: radius * 2,
          child: content,
        ),
      ),
    );
  }
}