verify flags better

Author: Elektryk-Andrzej

Code/ContextSystem/Contexts/FlagContext.cs

@@ -0,0 +1,39 @@
+using SER.Code.ContextSystem.BaseContexts;
+using SER.Code.ContextSystem.Structures;
+using SER.Code.FlagSystem.Flags;
+using SER.Code.Helpers.ResultSystem;
+using SER.Code.TokenSystem.Tokens;
+
+namespace SER.Code.ContextSystem.Contexts;
+
+public class FlagContext : StandardContext
+{
+    private string? _flagName;
+
+    public override string FriendlyName => "flag declaration";
+
+    public override TryAddTokenRes TryAddToken(BaseToken token)
+    {
+        if (Flag.FlagInfos.Count == 0)
+        {
+            Flag.RegisterFlags();
+        }
+
+        if (!Flag.FlagInfos.ContainsKey(token.RawRep))
+        {
+            return TryAddTokenRes.Error($"Flag '{token.RawRep}' is not a valid flag.");
+        }
+
+        _flagName = token.RawRep;
+        return TryAddTokenRes.End();
+    }
+
+    public override Result VerifyCurrentState()
+    {
+        return Result.Assert(_flagName is not null, "Name of the flag is missing.");
+    }
+
+    protected override void Execute()
+    {
+    }
+}

Code/TokenSystem/Tokens/FlagToken.cs

@@ -13,5 +13,9 @@ protected override IParseResult InternalParse(Script scr)
             : new Ignore();
     }
 
-    public RunnableContext? GetContext(Script scr) => null;   
-}
+    public RunnableContext GetContext(Script scr) => new SER.Code.ContextSystem.Contexts.FlagContext
+    {
+        LineNum = LineNum,
+        Script = scr,
+    };
+}