// Link test: measures the tablet ⇄ Orin link from the app, whose sockets are the
// only ones on the tablet bound to the USB network (`adb shell` traffic goes over
// WiFi). Pairs with tool/linktest_server.py on the Orin, which also logs every
// result, so a run is readable over SSH whatever happens to the screen.

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:math';
import 'dart:typed_data';

import 'package:flutter/material.dart';

import '../link/net.dart';
import '../shell_scope.dart';

const _down = 7791, _up = 7792, _echo = 7793, _results = 7794;

class LinkTest extends ChangeNotifier {
  LinkTest(this.usb);
  final UsbLink usb;

  bool running = false;
  String status = 'idle';
  final List<String> lines = [];

  /// UDP echo at each (size, rate) for [udpSecs], an app-like soak, then TCP each way.
  Future<void> run(String host, String label, {int udpSecs = 3, int soakSecs = 30, int tcpSecs = 5}) async {
    if (running) return;
    running = true;
    lines.clear();
    final id = '$label-${DateTime.now().toUtc().toIso8601String().substring(0, 19)}';
    _line('run $id → $host');
    try {
      await usb.bindFor(Uri(scheme: 'ws', host: host));
      await _report(host, {'id': id, 'kind': 'start', 'label': label});
      for (final size in [64, 1400]) {
        for (final rate in [10, 50, 100, 200, 500]) {
          _status('udp $size B × $rate/s');
          final r = await udpEcho(host, size: size, rate: rate, secs: udpSecs);
          _line('udp ${size}B $rate/s: ${r['loss_pct']}% loss, rtt p50 ${r['rtt_p50_ms']} p99 ${r['rtt_p99_ms']} max ${r['rtt_max_ms']} ms');
          await _report(host, {'id': id, 'kind': 'udp', ...r});
        }
      }
      _status('soak: 64 B × 10/s for $soakSecs s');
      final soak = await udpEcho(host, size: 64, rate: 10, secs: soakSecs);
      _line('soak ${soakSecs}s: ${soak['loss_pct']}% loss, max gap ${soak['max_gap_ms']} ms, rtt max ${soak['rtt_max_ms']} ms');
      await _report(host, {'id': id, 'kind': 'soak', ...soak});
      _status('tcp down $tcpSecs s');
      final d = await tcpDown(host, id, tcpSecs);
      _line('tcp down: ${d['mb_s']} MB/s');
      await _report(host, {'id': id, 'kind': 'tcp_down', ...d});
      _status('tcp up $tcpSecs s');
      final u = await tcpUp(host, id, tcpSecs);
      _line('tcp up: ${u['mb_s']} MB/s');
      await _report(host, {'id': id, 'kind': 'tcp_up', ...u});
      await _report(host, {'id': id, 'kind': 'end'});
      _status('done');
    } catch (e) {
      _line('error: $e');
      _status('failed');
      try {
        await _report(host, {'id': id, 'kind': 'error', 'error': '$e'});
      } catch (_) {}
    } finally {
      running = false;
      notifyListeners();
    }
  }

  /// Sends [rate] packets/s of [size] bytes for [secs], each carrying its sequence
  /// number and send time; loss, RTT and the longest silence come from the echoes.
  static Future<Map<String, dynamic>> udpEcho(String host, {required int size, required int rate, required int secs}) async {
    final addr = InternetAddress(host);
    final sock = await RawDatagramSocket.bind(InternetAddress.anyIPv4, 0);
    final clock = Stopwatch()..start();
    final rtts = <int>[];
    final seen = <int>{};
    var dups = 0, sendFails = 0, sent = 0;
    int? lastRx;
    var maxGap = 0;
    sock.listen((ev) {
      if (ev != RawSocketEvent.read) return;
      Datagram? d;
      while ((d = sock.receive()) != null) {
        if (d!.data.length < 12) continue;
        final b = ByteData.sublistView(d.data);
        final seq = b.getUint32(0);
        final now = clock.elapsedMicroseconds;
        if (!seen.add(seq)) {
          dups++;
          continue;
        }
        rtts.add(now - b.getInt64(4));
        if (lastRx != null) maxGap = max(maxGap, now - lastRx!);
        lastRx = now;
      }
    });
    final total = rate * secs;
    final buf = Uint8List(size);
    final done = Completer<void>();
    Timer.periodic(const Duration(milliseconds: 2), (t) {
      final due = min(total, clock.elapsedMicroseconds * rate ~/ 1000000);
      while (sent < due) {
        final b = ByteData.sublistView(buf);
        b.setUint32(0, sent);
        b.setInt64(4, clock.elapsedMicroseconds);
        if (sock.send(buf, addr, _echo) == 0) sendFails++;
        sent++;
      }
      if (sent >= total) {
        t.cancel();
        done.complete();
      }
    });
    await done.future;
    await Future<void>.delayed(const Duration(seconds: 1)); // stragglers
    sock.close();
    rtts.sort();
    double ms(int us) => (us / 100).round() / 10;
    int pct(double p) => rtts.isEmpty ? 0 : rtts[min(rtts.length - 1, (rtts.length * p).floor())];
    return {
      'size': size,
      'rate': rate,
      'secs': secs,
      'sent': sent,
      'received': seen.length,
      'loss_pct': sent == 0 ? 0 : ((sent - seen.length) * 1000 / sent).round() / 10,
      'dups': dups,
      'send_fails': sendFails,
      'rtt_p50_ms': ms(pct(0.5)),
      'rtt_p99_ms': ms(pct(0.99)),
      'rtt_max_ms': rtts.isEmpty ? null : ms(rtts.last),
      'max_gap_ms': ms(maxGap),
    };
  }

  static Future<Map<String, dynamic>> tcpDown(String host, String id, int secs) async {
    final s = await Socket.connect(host, _down, timeout: const Duration(seconds: 5));
    s.write('$id $secs\n');
    final clock = Stopwatch()..start();
    var bytes = 0;
    await s.timeout(Duration(seconds: secs + 30)).forEach((b) => bytes += b.length);
    s.destroy();
    final t = clock.elapsedMicroseconds / 1e6;
    return {'bytes': bytes, 'secs': (t * 1000).round() / 1000, 'mb_s': (bytes / t / 1e4).round() / 100};
  }

  /// Orin → tablet only: sustained bulk sampled every 250 ms, TTS-like bursts on a
  /// warm connection, and camera-like paced streams.
  Future<void> runDownload(String host, String label, {int repeats = 5, int bulkSecs = 10, int pacedSecs = 10}) async {
    if (running) return;
    running = true;
    lines.clear();
    final id = '$label-${DateTime.now().toUtc().toIso8601String().substring(0, 19)}';
    _line('download series $id → $host');
    try {
      await usb.bindFor(Uri(scheme: 'ws', host: host));
      await _report(host, {'id': id, 'kind': 'start', 'label': label, 'series': 'download'});
      for (var i = 0; i < repeats; i++) {
        _status('bulk ${i + 1}/$repeats, $bulkSecs s');
        final r = await tcpBulkSampled(host, id, bulkSecs);
        _line('bulk ${i + 1}: ${r['mb_s']} MB/s, 250 ms windows min ${r['win_min_mb_s']} p10 ${r['win_p10_mb_s']} max ${r['win_max_mb_s']}, longest stall ${r['max_gap_ms']} ms');
        await _report(host, {'id': id, 'kind': 'dl_bulk', 'n': i, ...r});
      }
      _status('bursts');
      final b = await tcpBursts(host, id, sizes: const [65536, 262144, 1048576, 4194304], repeats: repeats);
      for (final e in (b['sizes'] as List)) {
        _line('burst ${e['bytes'] ~/ 1024} KB: p50 ${e['p50_ms']} ms, max ${e['max_ms']} ms (${e['mb_s_p50']} MB/s at p50)');
      }
      await _report(host, {'id': id, 'kind': 'dl_bursts', ...b});
      for (final rate in const [500000, 1000000, 2000000, 4000000]) {
        _status('paced ${rate / 1e6} MB/s, $pacedSecs s');
        final r = await tcpPaced(host, id, rate, pacedSecs);
        _line('paced ${rate / 1e6} MB/s: got ${r['mb_s']} MB/s, ${r['frames']}/${r['expected']} frames, queueing p50 ${r['q_p50_ms']} p99 ${r['q_p99_ms']} max ${r['q_max_ms']} ms, >100 ms ${r['late_100']}, >500 ms ${r['late_500']}');
        await _report(host, {'id': id, 'kind': 'dl_paced', ...r});
      }
      await _report(host, {'id': id, 'kind': 'end'});
      _status('done');
    } catch (e) {
      _line('error: $e');
      _status('failed');
      try {
        await _report(host, {'id': id, 'kind': 'error', 'error': '$e'});
      } catch (_) {}
    } finally {
      running = false;
      notifyListeners();
    }
  }

  /// Burst latency against the idle gap before each burst, with and without keepalive traffic.
  Future<void> runBurstIdle(String host, String label) async {
    if (running) return;
    running = true;
    lines.clear();
    final id = '$label-${DateTime.now().toUtc().toIso8601String().substring(0, 19)}';
    _line('burst/idle series $id → $host');
    try {
      await usb.bindFor(Uri(scheme: 'ws', host: host));
      await _report(host, {'id': id, 'kind': 'start', 'label': label, 'series': 'burst-idle'});
      for (final (idleMs, ka) in const [(0, 0), (50, 0), (200, 0), (1000, 0), (1000, 50), (0, 0)]) {
        _status('256 KB bursts, idle $idleMs ms, keepalive $ka/s');
        final r = await tcpBursts(host, id, sizes: const [262144], repeats: 8, idle: Duration(milliseconds: idleMs), keepalivePps: ka);
        final e = (r['sizes'] as List).first;
        _line('idle $idleMs ms ka $ka/s: p50 ${e['p50_ms']} max ${e['max_ms']} ms ${e['ms']}');
        await _report(host, {'id': id, 'kind': 'dl_bursts', ...r});
      }
      await _report(host, {'id': id, 'kind': 'end'});
      _status('done');
    } catch (e) {
      _line('error: $e');
      _status('failed');
      try {
        await _report(host, {'id': id, 'kind': 'error', 'error': '$e'});
      } catch (_) {}
    } finally {
      running = false;
      notifyListeners();
    }
  }

  static Future<Map<String, dynamic>> tcpBulkSampled(String host, String id, int secs) async {
    final s = await Socket.connect(host, _down, timeout: const Duration(seconds: 5));
    s.write('$id $secs\n');
    final clock = Stopwatch()..start();
    final windows = <int, int>{};
    var bytes = 0, maxGap = 0;
    int? first, last;
    await s.timeout(Duration(seconds: secs + 60)).forEach((b) {
      final now = clock.elapsedMicroseconds;
      first ??= now;
      if (last != null) maxGap = max(maxGap, now - last!);
      last = now;
      bytes += b.length;
      windows.update((now - first!) ~/ 250000, (v) => v + b.length, ifAbsent: () => b.length);
    });
    s.destroy();
    final t = ((last ?? 0) - (first ?? 0)) / 1e6;
    final n = windows.isEmpty ? 0 : windows.keys.reduce(max); // drop the last, partial window
    final rates = [for (var i = 0; i < n; i++) (windows[i] ?? 0) * 4 / 1e6]..sort();
    double r2(num v) => (v * 100).round() / 100;
    return {
      'bytes': bytes,
      'secs': r2(t),
      'mb_s': t > 0 ? r2(bytes / t / 1e6) : 0,
      'win_min_mb_s': rates.isEmpty ? null : r2(rates.first),
      'win_p10_mb_s': rates.isEmpty ? null : r2(rates[rates.length ~/ 10]),
      'win_p50_mb_s': rates.isEmpty ? null : r2(rates[rates.length ~/ 2]),
      'win_max_mb_s': rates.isEmpty ? null : r2(rates.last),
      'zero_windows': rates.where((r) => r == 0).length,
      'max_gap_ms': (maxGap / 100).round() / 10,
    };
  }

  /// Each burst is requested on the same connection after 1 s idle, as utterances would be.
  static Future<Map<String, dynamic>> tcpBursts(String host, String id,
      {required List<int> sizes, required int repeats, Duration idle = const Duration(seconds: 1), int keepalivePps = 0}) async {
    // Optional light UDP traffic during the idle gaps, to tell link power saving from TCP behaviour.
    RawDatagramSocket? ka;
    Timer? kaTimer;
    if (keepalivePps > 0) {
      ka = await RawDatagramSocket.bind(InternetAddress.anyIPv4, 0);
      final addr = InternetAddress(host);
      kaTimer = Timer.periodic(Duration(microseconds: 1000000 ~/ keepalivePps), (_) => ka!.send(Uint8List(16), addr, _echo));
    }
    final s = await Socket.connect(host, _down, timeout: const Duration(seconds: 5));
    s.write('$id burst\n');
    var got = 0;
    Completer<void>? want;
    var target = 0;
    final sub = s.listen((b) {
      got += b.length;
      final w = want;
      if (w != null && !w.isCompleted && got >= target) w.complete();
    });
    final out = <Map<String, dynamic>>[];
    for (final size in sizes) {
      final ms = <double>[];
      for (var i = 0; i < repeats; i++) {
        await Future<void>.delayed(idle);
        got = 0;
        target = size;
        final w = want = Completer<void>();
        final clock = Stopwatch()..start();
        s.write('$size\n');
        await w.future.timeout(const Duration(seconds: 60));
        want = null;
        ms.add(clock.elapsedMicroseconds / 1000);
      }
      ms.sort();
      final p50 = ms[ms.length ~/ 2];
      out.add({
        'bytes': size,
        'ms': [for (final m in ms) (m * 10).round() / 10],
        'p50_ms': (p50 * 10).round() / 10,
        'max_ms': (ms.last * 10).round() / 10,
        'mb_s_p50': (size / p50 / 10).round() / 100,
      });
    }
    await sub.cancel();
    s.destroy();
    kaTimer?.cancel();
    ka?.close();
    return {'idle_ms': idle.inMilliseconds, 'keepalive_pps': keepalivePps, 'sizes': out};
  }

  /// Frames carry the Orin's send time. The clocks are not compared absolutely: queueing
  /// delay is each frame's one-way delay minus the run's smallest.
  static Future<Map<String, dynamic>> tcpPaced(String host, String id, int rate, int secs) async {
    final s = await Socket.connect(host, _down, timeout: const Duration(seconds: 5));
    s.write('$id paced $rate $secs\n');
    final header = BytesBuilder();
    var skip = 0, bytes = 0;
    final owd = <double>[];
    double? firstRx, lastRx;
    await s.timeout(Duration(seconds: secs + 60)).forEach((chunk) {
      bytes += chunk.length;
      var i = 0;
      while (i < chunk.length) {
        if (skip > 0) {
          final n = min(skip, chunk.length - i);
          skip -= n;
          i += n;
          continue;
        }
        final n = min(12 - header.length, chunk.length - i);
        header.add(Uint8List.sublistView(chunk, i, i + n));
        i += n;
        if (header.length == 12) {
          final h = ByteData.sublistView(header.takeBytes());
          final size = h.getUint32(0);
          final sentAt = h.getFloat64(4);
          skip = size - 12;
          // Arrival of the header stands for the frame; with skip pending, the rest follows.
          final now = DateTime.now().microsecondsSinceEpoch / 1e6;
          firstRx ??= now;
          lastRx = now;
          owd.add(now - sentAt);
        }
      }
    });
    s.destroy();
    final base = owd.isEmpty ? 0.0 : owd.reduce(min);
    final q = [for (final d in owd) (d - base) * 1000]..sort();
    double r1(num v) => (v * 10).round() / 10;
    final t = (lastRx ?? 0) - (firstRx ?? 0);
    return {
      'rate': rate,
      'secs': secs,
      'expected': secs * 30,
      'frames': owd.length,
      'mb_s': t > 0 ? (bytes / t / 1e4).round() / 100 : 0,
      'q_p50_ms': q.isEmpty ? null : r1(q[q.length ~/ 2]),
      'q_p99_ms': q.isEmpty ? null : r1(q[min(q.length - 1, (q.length * 0.99).floor())]),
      'q_max_ms': q.isEmpty ? null : r1(q.last),
      'late_100': q.where((v) => v > 100).length,
      'late_500': q.where((v) => v > 500).length,
    };
  }

  static Future<Map<String, dynamic>> tcpUp(String host, String id, int secs) async {
    final s = await Socket.connect(host, _up, timeout: const Duration(seconds: 5));
    final reply = utf8.decoder.bind(s).join();
    s.write('$id\n');
    final chunk = Uint8List(65536);
    final clock = Stopwatch()..start();
    var bytes = 0;
    while (clock.elapsed < Duration(seconds: secs)) {
      s.add(chunk);
      await s.flush();
      bytes += chunk.length;
    }
    await s.close();
    final got = int.tryParse((await reply.timeout(const Duration(seconds: 30))).trim()) ?? -1;
    final t = clock.elapsedMicroseconds / 1e6;
    s.destroy();
    return {'bytes': bytes, 'orin_bytes': got, 'secs': (t * 1000).round() / 1000, 'mb_s': (got / t / 1e4).round() / 100};
  }

  static Future<void> _report(String host, Map<String, dynamic> rec) async {
    final s = await Socket.connect(host, _results, timeout: const Duration(seconds: 5));
    s.write('${jsonEncode({...rec, 'tablet_ts': DateTime.now().millisecondsSinceEpoch / 1000})}\n');
    await s.close();
    s.destroy();
  }

  void _status(String s) {
    status = s;
    notifyListeners();
  }

  void _line(String s) {
    lines.add(s);
    notifyListeners();
  }
}

class LinkTestPage extends StatefulWidget {
  const LinkTestPage({super.key, required this.test, required this.host, this.restoreBinding});
  final LinkTest test;
  final String host;

  /// Called after a run, to return the binding to what the gateway link needs.
  final Future<void> Function()? restoreBinding;

  @override
  State<LinkTestPage> createState() => _LinkTestPageState();
}

class _LinkTestPageState extends State<LinkTestPage> {
  late final _host = TextEditingController(text: widget.host);
  final _label = TextEditingController(text: 'setup');

  Future<void> _run() async {
    await widget.test.run(_host.text.trim(), _label.text.trim().replaceAll(' ', '_'));
    await widget.restoreBinding?.call();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(leading: const MenuButton(), title: const Text('Link test')),
      body: ListenableBuilder(
        listenable: widget.test,
        builder: (context, _) {
          final t = widget.test;
          return ListView(padding: const EdgeInsets.all(16), children: [
            Row(children: [
              Expanded(child: TextField(controller: _host, decoration: const InputDecoration(labelText: 'Orin address'))),
              const SizedBox(width: 16),
              Expanded(child: TextField(controller: _label, decoration: const InputDecoration(labelText: 'Setup label'))),
              const SizedBox(width: 16),
              FilledButton(onPressed: t.running ? null : _run, child: Text(t.running ? 'Running…' : 'Run')),
            ]),
            const SizedBox(height: 12),
            Text('Status: ${t.status}', style: Theme.of(context).textTheme.titleMedium),
            const SizedBox(height: 8),
            for (final l in t.lines) Text(l, style: const TextStyle(fontFamily: 'monospace')),
          ]);
        },
      ),
    );
  }
}