add timeline

lib/objects/objects.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
 
 class DestinationObject {
   const DestinationObject(
@@ -190,6 +191,143 @@ class LocoSummary extends Loco {
   );
 }
 
+class LocoAttrVersion {
+  final String attrCode;
+  final int? versionId;
+  final int locoId;
+  final int? attrTypeId;
+  final String? valueStr;
+  final int? valueInt;
+  final DateTime? valueDate;
+  final bool? valueBool;
+  final String? valueEnum;
+  final DateTime? validFrom;
+  final DateTime? validTo;
+  final DateTime? txnFrom;
+  final DateTime? txnTo;
+  final String? suggestedBy;
+  final String? approvedBy;
+  final DateTime? approvedAt;
+  final int? sourceEventId;
+  final String? precisionLevel;
+  final String? maskedValidFrom;
+  final dynamic valueNorm;
+
+  const LocoAttrVersion({
+    required this.attrCode,
+    required this.locoId,
+    this.versionId,
+    this.attrTypeId,
+    this.valueStr,
+    this.valueInt,
+    this.valueDate,
+    this.valueBool,
+    this.valueEnum,
+    this.validFrom,
+    this.validTo,
+    this.txnFrom,
+    this.txnTo,
+    this.suggestedBy,
+    this.approvedBy,
+    this.approvedAt,
+    this.sourceEventId,
+    this.precisionLevel,
+    this.maskedValidFrom,
+    this.valueNorm,
+  });
+
+  factory LocoAttrVersion.fromJson(Map<String, dynamic> json) {
+    return LocoAttrVersion(
+      attrCode: json['attr_code']?.toString() ?? '',
+      locoId: (json['loco_id'] as num?)?.toInt() ?? 0,
+      versionId: (json['loco_attr_v_id'] as num?)?.toInt(),
+      attrTypeId: (json['attr_type_id'] as num?)?.toInt(),
+      valueStr: json['value_str']?.toString(),
+      valueInt: (json['value_int'] as num?)?.toInt(),
+      valueDate: _parseDate(json['value_date']),
+      valueBool: _parseBool(json['value_bool']),
+      valueEnum: json['value_enum']?.toString(),
+      validFrom: _parseDate(json['valid_from']),
+      validTo: _parseDate(json['valid_to']),
+      txnFrom: _parseDate(json['txn_from']),
+      txnTo: _parseDate(json['txn_to']),
+      suggestedBy: json['suggested_by']?.toString(),
+      approvedBy: json['approved_by']?.toString(),
+      approvedAt: _parseDate(json['approved_at']),
+      sourceEventId: (json['source_event_id'] as num?)?.toInt(),
+      precisionLevel: json['precision_level']?.toString(),
+      maskedValidFrom: json['masked_valid_from']?.toString(),
+      valueNorm: json['value_norm'],
+    );
+  }
+
+  static DateTime? _parseDate(dynamic value) {
+    if (value == null) return null;
+    if (value is DateTime) return value;
+    return DateTime.tryParse(value.toString());
+  }
+
+  static bool? _parseBool(dynamic value) {
+    if (value == null) return null;
+    if (value is bool) return value;
+    if (value is num) return value != 0;
+    final str = value.toString().toLowerCase();
+    if (['true', '1', 'yes'].contains(str)) return true;
+    if (['false', '0', 'no'].contains(str)) return false;
+    return null;
+  }
+
+  static List<LocoAttrVersion> fromGroupedJson(dynamic json) {
+    final List<LocoAttrVersion> items = [];
+    if (json is Map) {
+      json.forEach((key, value) {
+        if (value is List) {
+          for (final entry in value) {
+            if (entry is Map<String, dynamic>) {
+              final merged = Map<String, dynamic>.from(entry);
+              merged.putIfAbsent('attr_code', () => key);
+              items.add(LocoAttrVersion.fromJson(merged));
+            }
+          }
+        }
+      });
+    }
+    items.sort(
+      (a, b) {
+        final aDate = a.validFrom ?? a.txnFrom ?? DateTime.fromMillisecondsSinceEpoch(0);
+        final bDate = b.validFrom ?? b.txnFrom ?? DateTime.fromMillisecondsSinceEpoch(0);
+        final dateCompare = aDate.compareTo(bDate);
+        if (dateCompare != 0) return dateCompare;
+        return a.attrCode.compareTo(b.attrCode);
+      },
+    );
+    return items;
+  }
+
+  String get valueLabel {
+    if (valueStr != null && valueStr!.isNotEmpty) return valueStr!;
+    if (valueEnum != null && valueEnum!.isNotEmpty) return valueEnum!;
+    if (valueInt != null) return valueInt!.toString();
+    if (valueBool != null) return valueBool! ? 'Yes' : 'No';
+    if (valueDate != null) return DateFormat('yyyy-MM-dd').format(valueDate!);
+    if (valueNorm != null && valueNorm.toString().isNotEmpty) {
+      return valueNorm.toString();
+    }
+    return '—';
+  }
+
+  String get validityRange {
+    final start = maskedValidFrom ?? _formatDate(validFrom) ?? 'Unknown';
+    final end = _formatDate(validTo, fallback: 'Present') ?? 'Present';
+    return '$start → $end';
+  }
+
+  String? _formatDate(DateTime? value, {String? fallback}) {
+    if (value == null) return fallback;
+    return DateFormat('yyyy-MM-dd').format(value);
+  }
+}
+
 class LeaderboardEntry {
   final String userId, username, userFullName;
   final double mileage;