feat: improve record grouping and display

lib/screens/history_screen.dart

@@ -459,23 +459,64 @@ class HistoryScreenState extends State<HistoryScreen> {
     );
   }
 
+  String _formatLocoInfo(TrainRecord record) {
+    final locoType = record.locoType.trim();
+    final loco = record.loco.trim();
+
+    if (locoType.isNotEmpty && loco.isNotEmpty) {
+      final shortLoco =
+          loco.length > 5 ? loco.substring(loco.length - 5) : loco;
+      return "$locoType-$shortLoco";
+    } else if (locoType.isNotEmpty) {
+      return locoType;
+    } else if (loco.isNotEmpty) {
+      return loco;
+    }
+    return "";
+  }
+
   String _getDifferingInfo(
       TrainRecord record, TrainRecord latest, GroupBy groupBy) {
     final train = record.train.trim();
     final loco = record.loco.trim();
+    final locoType = record.locoType.trim();
     final latestTrain = latest.train.trim();
     final latestLoco = latest.loco.trim();
+    final latestLocoType = latest.locoType.trim();
 
     switch (groupBy) {
       case GroupBy.trainOnly:
-        return loco != latestLoco && loco.isNotEmpty ? loco : "";
+        if (loco != latestLoco && loco.isNotEmpty) {
+          return _formatLocoInfo(record);
+        }
+        return "";
       case GroupBy.locoOnly:
         return train != latestTrain && train.isNotEmpty ? train : "";
       case GroupBy.trainOrLoco:
-        if (train.isNotEmpty && train != latestTrain) return train;
-        if (loco.isNotEmpty && loco != latestLoco) return loco;
+        final trainDiff = train.isNotEmpty && train != latestTrain ? train : "";
+        final locoDiff = loco.isNotEmpty && loco != latestLoco
+            ? _formatLocoInfo(record)
+            : "";
+
+        if (trainDiff.isNotEmpty && locoDiff.isNotEmpty) {
+          return "$trainDiff $locoDiff";
+        } else if (trainDiff.isNotEmpty) {
+          return trainDiff;
+        } else if (locoDiff.isNotEmpty) {
+          return locoDiff;
+        }
         return "";
       case GroupBy.trainAndLoco:
+        if (train.isNotEmpty && train != latestTrain) {
+          final locoInfo = _formatLocoInfo(record);
+          if (locoInfo.isNotEmpty) {
+            return "$train $locoInfo";
+          }
+          return train;
+        }
+        if (loco.isNotEmpty && loco != latestLoco) {
+          return _formatLocoInfo(record);
+        }
         return "";
     }
   }

lib/services/merge_service.dart

@@ -5,7 +5,8 @@ class MergeService {
   static String? _generateGroupKey(TrainRecord record, GroupBy groupBy) {
     final train = record.train.trim();
     final loco = record.loco.trim();
-    final hasTrain = train.isNotEmpty && train != "<NUL>" && !train.contains("-----");
+    final hasTrain =
+        train.isNotEmpty && train != "<NUL>" && !train.contains("-----");
     final hasLoco = loco.isNotEmpty && loco != "<NUL>";
 
     switch (groupBy) {
@@ -14,8 +15,13 @@ class MergeService {
       case GroupBy.locoOnly:
         return hasLoco ? loco : null;
       case GroupBy.trainOrLoco:
-        if (hasTrain) return train;
-        if (hasLoco) return loco;
+        if (hasTrain && hasLoco) {
+          return "train:$train|loco:$loco";
+        } else if (hasTrain) {
+          return "train:$train";
+        } else if (hasLoco) {
+          return "loco:$loco";
+        }
         return null;
       case GroupBy.trainAndLoco:
         return (hasTrain && hasLoco) ? "${train}_$loco" : null;
@@ -39,6 +45,13 @@ class MergeService {
                 settings.timeWindow.duration!)
             .toList();
 
+    validRecords
+        .sort((a, b) => b.receivedTimestamp.compareTo(a.receivedTimestamp));
+
+    if (settings.groupBy == GroupBy.trainOrLoco) {
+      return _groupByTrainOrLoco(validRecords);
+    }
+
     final groupedRecords = <String, List<TrainRecord>>{};
     for (final record in validRecords) {
       final key = _generateGroupKey(record, settings.groupBy);
@@ -52,13 +65,10 @@ class MergeService {
 
     groupedRecords.forEach((key, group) {
       if (group.length >= 2) {
-        group
-            .sort((a, b) => b.receivedTimestamp.compareTo(a.receivedTimestamp));
-        final latestRecord = group.first;
         mergedRecords.add(MergedTrainRecord(
           groupKey: key,
           records: group,
-          latestRecord: latestRecord,
+          latestRecord: group.first,
         ));
         for (final record in group) {
           mergedRecordIds.add(record.uniqueId);
@@ -66,8 +76,9 @@ class MergeService {
       }
     });
 
-    final singleRecords =
-        allRecords.where((r) => !mergedRecordIds.contains(r.uniqueId)).toList();
+    final singleRecords = validRecords
+        .where((r) => !mergedRecordIds.contains(r.uniqueId))
+        .toList();
 
     final List<Object> mixedList = [...mergedRecords, ...singleRecords];
     mixedList.sort((a, b) {
@@ -82,4 +93,77 @@ class MergeService {
 
     return mixedList;
   }
+
+  static List<Object> _groupByTrainOrLoco(List<TrainRecord> records) {
+    final List<MergedTrainRecord> mergedRecords = [];
+    final Set<String> usedRecordIds = {};
+
+    for (int i = 0; i < records.length; i++) {
+      final record = records[i];
+      if (usedRecordIds.contains(record.uniqueId)) continue;
+
+      final group = <TrainRecord>[record];
+      usedRecordIds.add(record.uniqueId);
+
+      for (int j = i + 1; j < records.length; j++) {
+        final otherRecord = records[j];
+        if (usedRecordIds.contains(otherRecord.uniqueId)) continue;
+
+        final recordTrain = record.train.trim();
+        final otherTrain = otherRecord.train.trim();
+        final recordLoco = record.loco.trim();
+        final otherLoco = otherRecord.loco.trim();
+
+        final trainMatch = recordTrain.isNotEmpty &&
+            recordTrain != "<NUL>" &&
+            !recordTrain.contains("-----") &&
+            otherTrain.isNotEmpty &&
+            otherTrain != "<NUL>" &&
+            !otherTrain.contains("-----") &&
+            recordTrain == otherTrain;
+
+        final locoMatch = recordLoco.isNotEmpty &&
+            recordLoco != "<NUL>" &&
+            otherLoco.isNotEmpty &&
+            otherLoco != "<NUL>" &&
+            recordLoco == otherLoco;
+
+        final bothTrainEmpty = (recordTrain.isEmpty ||
+                recordTrain == "<NUL>" ||
+                recordTrain.contains("----")) &&
+            (otherTrain.isEmpty ||
+                otherTrain == "<NUL>" ||
+                otherTrain.contains("----"));
+
+        if (trainMatch || locoMatch || (bothTrainEmpty && locoMatch)) {
+          group.add(otherRecord);
+          usedRecordIds.add(otherRecord.uniqueId);
+        }
+      }
+
+      if (group.length >= 2) {
+        mergedRecords.add(MergedTrainRecord(
+          groupKey: "train_or_loco_group",
+          records: group,
+          latestRecord: group.first,
+        ));
+      }
+    }
+
+    final singleRecords =
+        records.where((r) => !usedRecordIds.contains(r.uniqueId)).toList();
+
+    final List<Object> result = [...mergedRecords, ...singleRecords];
+    result.sort((a, b) {
+      final aTime = a is MergedTrainRecord
+          ? a.latestRecord.receivedTimestamp
+          : (a as TrainRecord).receivedTimestamp;
+      final bTime = b is MergedTrainRecord
+          ? b.latestRecord.receivedTimestamp
+          : (b as TrainRecord).receivedTimestamp;
+      return bTime.compareTo(aTime);
+    });
+
+    return result;
+  }
 }