import 'dart:io';
import 'dart:math';

import 'package:sync_relay_core/core.dart';

enum MediaGate { ok, gone, unauthorized, offline }

class ViewerToken {
  final String token;
  /// Cleaned ([cleanMemberName]); follows `profile` renames.
  String name;
  /// Sent the server's host key in hello: the hosting app's own client.
  bool isHost = false;
  int bytesServed = 0;
  DateTime lastSeen;
  /// When this member's recent nudges went out, for the rate cap.
  final List<DateTime> nudges = [];
  ViewerToken({required this.token, required this.name})
      : lastSeen = DateTime.now().toUtc();

  /// Takes one nudge at [now] if under the caps
  /// ([RelayConstants.nudgesPerSec] / [RelayConstants.nudgesPerMin]).
  bool takeNudge(DateTime now) {
    nudges.removeWhere((t) => now.difference(t) >= const Duration(minutes: 1));
    final lastSec = nudges.where((t) => now.difference(t) < const Duration(seconds: 1)).length;
    if (nudges.length >= RelayConstants.nudgesPerMin || lastSec >= RelayConstants.nudgesPerSec) return false;
    nudges.add(now);
    return true;
  }

  bool isStale(Duration timeout, [DateTime? now]) =>
      (now ?? DateTime.now().toUtc()).difference(lastSeen) > timeout;

  void touch([DateTime? now]) => lastSeen = now ?? DateTime.now().toUtc();
}

class SessionMedia {
  final String name;
  final int size;
  final double duration;
  final String? url;
  final File? file;
  /// Jellyfin media by reference; never together with [url] or [file].
  final JellyfinRef? jellyfin;
  final int mediaId;
  const SessionMedia({
    required this.name,
    required this.size,
    required this.duration,
    this.url,
    this.file,
    this.jellyfin,
    this.mediaId = 1,
  });
}

class Session {
  final String id;
  /// The server password; '' is an open server. The hosting app changes it
  /// when it starts sharing ([SyncServer.share]).
  String secret;
  final Map<String, ViewerToken> tokens = {};
  SessionMedia? media;
  final _random = Random.secure();

  Session({required this.id, required this.secret});

  /// The avatar is only checked here; the engine keeps the picture.
  String issueToken(String name, String avatar) {
    if (avatar.length > RelayConstants.maxAvatarBytes) {
      throw const AuthException('avatar too large');
    }
    final bytes = List<int>.generate(16, (_) => _random.nextInt(256));
    final token = bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
    tokens[token] = ViewerToken(token: token, name: cleanMemberName(name));
    return token;
  }

  MediaGate gate(String? token) {
    if (token == null || !tokens.containsKey(token)) return MediaGate.unauthorized;
    return MediaGate.ok;
  }

  void addBytes(String? token, int n) {
    if (token != null) tokens[token]?.bytesServed += n;
  }

  int get totalBytesServed => tokens.values.fold(0, (a, v) => a + v.bytesServed);
}

class SessionMap {
  final Map<String, Session> _sessions = {};

  Session getOrCreate(String id, String secret) =>
      _sessions.putIfAbsent(id, () => Session(id: id, secret: secret));

  Session? get(String id) => _sessions[id];

  void drop(String id) => _sessions.remove(id);
}