Setup command for day 3

bin/adventofcode2025.dart

@@ -1,5 +1,6 @@
 import 'package:adventofcode2025/day1/command.dart' as day1;
 import 'package:adventofcode2025/day2/command.dart' as day2;
+import 'package:adventofcode2025/day3/command.dart' as day3;
 
 import 'package:args/command_runner.dart';
 
@@ -7,5 +8,6 @@ void main(List<String> arguments) {
   CommandRunner("adventofcode2025", "Advent of Code 2025 solutions")
     ..addCommand(day1.Day1Command())
     ..addCommand(day2.Day2Command())
+    ..addCommand(day3.Day3Command())
     ..run(arguments);
 }

lib/day3/command.dart

@@ -0,0 +1,36 @@
+import "dart:io";
+
+import "package:args/command_runner.dart";
+
+class Day3Command extends Command {
+  // The [name] and [description] properties must be defined by every
+  // subclass.
+  @override
+  final name = "day3";
+
+  @override
+  final description = "Run Advent of Code 2025 Day 3";
+
+  Day3Command() {
+    // we can add command specific arguments here.
+    // [argParser] is automatically created by the parent class.
+  }
+
+  // [run] may also return a Future.
+  @override
+  Future<void> run() async {
+    // [argResults] is set before [run()] is called and contains the flags/options
+    // passed to this command.
+
+    if (argResults!.rest.length != 1) {
+      print(
+        "Expected 1 positional arguments, found ${argResults!.rest.length}",
+      );
+    }
+    var filePath = argResults!.rest[0];
+
+    print("Parsing file: $filePath");
+
+    var inputFile = File(filePath);
+  }
+}