import 'package:iperf3gui/domain/models/iperf3_event.dart';

/// Renders parsed iperf3 events as the kind of line iperf3 itself would print.
///
/// The app consumes `--json-stream`, so the familiar text layout has to be
/// rebuilt here. Keeping it in one pure function makes it testable and leaves
/// the structured events untouched for anything else that wants them.
String? formatIperf3Event(Iperf3Event event) {
  return switch (event) {
    Iperf3Start e => _formatStart(e),
    Iperf3Interval e => _formatInterval(e),
    Iperf3End e => _formatEnd(e),
    Iperf3Error e => 'iperf3 error: ${e.message}',
    Iperf3Stopped _ => 'Stopped by user.',
    Iperf3LogLine e => e.text.isEmpty ? null : e.text,
  };
}

String _formatStart(Iperf3Start e) {
  final parts = <String>[];
  if (e.targetHost != null) {
    final port = e.targetPort != null ? ', port ${e.targetPort}' : '';
    parts.add('Connecting to host ${e.targetHost}$port');
  }
  final detail = <String>[
    if (e.protocol != null) e.protocol!,
    if (e.streamCount != null)
      '${e.streamCount} stream${e.streamCount == 1 ? '' : 's'}',
    if (e.durationSeconds != null) '${e.durationSeconds}s',
  ];
  if (detail.isNotEmpty) parts.add(detail.join(' · '));
  return parts.isEmpty ? '' : parts.join('\n');
}

String _formatInterval(Iperf3Interval e) {
  final window = '${_seconds(e.start)}-${_seconds(e.end)} sec';
  final line = StringBuffer('[SUM]  $window   '
      '${formatBytes(e.bytes)}   ${formatBitrate(e.bitsPerSecond)}');
  if (e.retransmits != null) {
    line.write('   ${e.retransmits} retr');
  }
  if (e.omitted) line.write('   (omitted)');
  return line.toString();
}

String _formatEnd(Iperf3End e) {
  final lines = <String>['- ' * 20];
  final sent = e.sent;
  final received = e.received;
  if (sent != null) {
    lines.add('[SUM]  0.00-${_seconds(sent.seconds)} sec   '
        '${formatBytes(sent.bytes)}   ${formatBitrate(sent.bitsPerSecond)}'
        '${sent.retransmits != null ? '   ${sent.retransmits} retr' : ''}'
        '   sender');
  }
  if (received != null) {
    lines.add('[SUM]  0.00-${_seconds(received.seconds)} sec   '
        '${formatBytes(received.bytes)}   '
        '${formatBitrate(received.bitsPerSecond)}   receiver');
  }
  if (e.hostCpuPercent != null) {
    lines.add('CPU: local ${e.hostCpuPercent!.toStringAsFixed(1)}%'
        '${e.remoteCpuPercent != null ? ', remote ${e.remoteCpuPercent!.toStringAsFixed(1)}%' : ''}');
  }
  return lines.join('\n');
}

String _seconds(double value) => value.toStringAsFixed(2);

/// Byte totals the way iperf3 prints them — `93.8 MBytes`.
String formatBytes(int bytes) {
  const units = ['Bytes', 'KBytes', 'MBytes', 'GBytes', 'TBytes'];
  var value = bytes.toDouble();
  var unit = 0;
  while (value >= 1024 && unit < units.length - 1) {
    value /= 1024;
    unit++;
  }
  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
  return '${value.toStringAsFixed(precision)} ${units[unit]}';
}

/// Bitrates the way iperf3 prints them — `786 Mbits/sec`. Decimal units, since
/// network rates are powers of ten while transfer totals are powers of two.
String formatBitrate(double bitsPerSecond) {
  const units = ['bits/sec', 'Kbits/sec', 'Mbits/sec', 'Gbits/sec'];
  var value = bitsPerSecond;
  var unit = 0;
  while (value >= 1000 && unit < units.length - 1) {
    value /= 1000;
    unit++;
  }
  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
  return '${value.toStringAsFixed(precision)} ${units[unit]}';
}