Add support for 2-character manufacturer codes in the WMI

Some manufacturers use the first 2 characters of the WMI as the
manufacturer ID, with the 3rd denoting the specific class of vehicle
specific to that manufacturer.

Fixes #7.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.2.1
+
+- Support VINs with 2-character manufacturer IDs in their WMI (reported by @huangkaichang, issue #7)
+
 ## 0.2.0-nullsafety
 
 - Migrate for null safety

lib/src/vin_decoder_base.dart

@@ -65,10 +65,18 @@ class VIN {
 
   /// Get the full name of the vehicle manufacturer as defined by the [wmi].
   String? getManufacturer() {
+    // Check for the standard case - a 3 character WMI
     if (manufacturers.containsKey(this.wmi)) {
       return manufacturers[this.wmi];
     } else {
-      return "Unknown (WMI: ${this.wmi.toUpperCase()})";
+      // Some manufacturers only use the first 2 characters for manufacturer
+      // identification, and the third for the class of vehicle.
+      var id = this.wmi.substring(0, 2);
+      if (manufacturers.containsKey(id)) {
+        return manufacturers[id];
+      } else {
+        return "Unknown (WMI: ${this.wmi.toUpperCase()})";
+      }
     }
   }
 

test/vin_decoder_test.dart

@@ -37,4 +37,26 @@ void main() {
       expect(vin.getRegion(), 'AS');
     });
   });
+
+  group('2-character WMI Manufacturer Test', () {
+    late VIN vin;
+
+    setUp(() {
+      // Here the first 2 characters refer to the manufacturer, with the 3rd
+      // representing the class of vehicle specific to that manufacturer.
+      vin = VIN(number: '5TENL42N94Z436445');
+    });
+
+    test('Validity Test', () {
+      expect(vin.valid(), isTrue);
+    });
+
+    test('Region Test', () {
+      expect(vin.getRegion(), 'NA');
+    });
+
+    test('Manufacturer Test', () {
+      expect(vin.getManufacturer(), 'Toyota - trucks');
+    });
+  });
 }