import 'dart:async';

import '../layout/layout_controller.dart';
import '../session/log_buffer.dart';
import '../session/packet_buffer.dart';

typedef ProgressCallback = void Function(double progress);

/// Returned by export operations so the UI can report what happened.
class ExportResult {
  ExportResult({required this.path, required this.bytesWritten});
  /// On native: filesystem path. On Web: filename.
  final String path;
  final int bytesWritten;
}

/// Builds CSV row strings. Shared by both platform implementations so the
/// row layout is defined exactly once.
class CsvRowBuilder {
  CsvRowBuilder(this.layout);
  final LayoutController layout;

  /// Header row for data CSV. Disabled channels are omitted; pause and the
  /// 8 status fields always appear.
  String dataHeader() {
    final cols = <String>['timestamp_us'];
    for (var ch = 1; ch <= 16; ch++) {
      if (layout.configFor(ch).enabled) {
        cols.add('ch${ch}_${_safe(layout.configFor(ch).name)}');
      }
    }
    cols.add('pause');
    for (var s = 0; s < 8; s++) {
      cols.add('status${s + 1}_${_safe(layout.statusNames[s])}');
    }
    return cols.join(',');
  }

  /// Row for one packet. Missing values are blank cells.
  String dataRow(packet) {
    final cells = <String>[];
    cells.add(packet.hasTimestampUs() ? packet.timestampUs.toString() : '');
    for (var ch = 1; ch <= 16; ch++) {
      if (!layout.configFor(ch).enabled) continue;
      cells.add(_channelCell(packet, ch));
    }
    cells.add(packet.hasPause() ? (packet.pause ? '1' : '0') : '');
    for (var s = 1; s <= 8; s++) {
      cells.add(_statusCell(packet, s));
    }
    return cells.join(',');
  }

  String logHeader() => 'timestamp_us,severity,error_number,description';

  String logRow(entry) {
    final ts = entry.hasTimestampUs() ? entry.timestampUs.toString() : '';
    final sev = entry.hasSeverity() ? entry.severity.name : '';
    final err = entry.hasErrorNumber() ? entry.errorNumber.toString() : '';
    final desc = entry.hasDescription() ? _escape(entry.description) : '';
    return '$ts,$sev,$err,$desc';
  }

  static String _channelCell(packet, int ch) {
    switch (ch) {
      case 1:  return packet.hasCh1()  ? packet.ch1.toString()  : '';
      case 2:  return packet.hasCh2()  ? packet.ch2.toString()  : '';
      case 3:  return packet.hasCh3()  ? packet.ch3.toString()  : '';
      case 4:  return packet.hasCh4()  ? packet.ch4.toString()  : '';
      case 5:  return packet.hasCh5()  ? packet.ch5.toString()  : '';
      case 6:  return packet.hasCh6()  ? packet.ch6.toString()  : '';
      case 7:  return packet.hasCh7()  ? packet.ch7.toString()  : '';
      case 8:  return packet.hasCh8()  ? packet.ch8.toString()  : '';
      case 9:  return packet.hasCh9()  ? packet.ch9.toString()  : '';
      case 10: return packet.hasCh10() ? packet.ch10.toString() : '';
      case 11: return packet.hasCh11() ? packet.ch11.toString() : '';
      case 12: return packet.hasCh12() ? packet.ch12.toString() : '';
      case 13: return packet.hasCh13() ? packet.ch13.toString() : '';
      case 14: return packet.hasCh14() ? packet.ch14.toString() : '';
      case 15: return packet.hasCh15() ? packet.ch15.toString() : '';
      case 16: return packet.hasCh16() ? packet.ch16.toString() : '';
      default: return '';
    }
  }

  static String _statusCell(packet, int s) {
    switch (s) {
      case 1: return packet.hasStatus1() ? packet.status1.toString() : '';
      case 2: return packet.hasStatus2() ? packet.status2.toString() : '';
      case 3: return packet.hasStatus3() ? packet.status3.toString() : '';
      case 4: return packet.hasStatus4() ? packet.status4.toString() : '';
      case 5: return packet.hasStatus5() ? packet.status5.toString() : '';
      case 6: return packet.hasStatus6() ? packet.status6.toString() : '';
      case 7: return packet.hasStatus7() ? packet.status7.toString() : '';
      case 8: return packet.hasStatus8() ? packet.status8.toString() : '';
      default: return '';
    }
  }

  /// Strip characters that would break CSV column names.
  static String _safe(String s) => s.replaceAll(RegExp(r'[,\s]+'), '_');

  /// Escape a free-form field for CSV. Wraps in quotes if needed.
  static String _escape(String s) {
    if (s.contains(',') || s.contains('"') || s.contains('\n')) {
      return '"${s.replaceAll('"', '""')}"';
    }
    return s;
  }
}

/// Common interface implemented by both platform exporters.
abstract class CsvExporter {
  /// Export the entire packet buffer as data CSV.
  Future<ExportResult> exportData({
    required PacketBuffer buffer,
    required LayoutController layout,
    ProgressCallback? onProgress,
  });

  /// Export the entire log buffer as log CSV.
  Future<ExportResult> exportLog({
    required LogBuffer buffer,
    ProgressCallback? onProgress,
  });
}