custom command trees, no validation so far

src/main/java/carpet/script/command/CommandArgument.java

@@ -89,6 +89,11 @@ import static net.minecraft.server.command.CommandManager.argument;
 
 public abstract class CommandArgument
 {
+    public static CommandSyntaxException error(String text)
+    {
+        return new SimpleCommandExceptionType(new LiteralText(text)).create();
+    }
+
     private static final List<? extends CommandArgument> baseTypes = Lists.newArrayList(
             // default
             new StringArgument(),
@@ -241,7 +246,7 @@ public abstract class CommandArgument
 
     public static final CommandArgument DEFAULT = baseTypes.get(0);
 
-    private static CommandArgument getTypeForArgument(String argument, CarpetScriptHost host)
+    public static CommandArgument getTypeForArgument(String argument, CarpetScriptHost host)
     {
         String[] components = argument.split("_");
         String suffix = components[components.length-1].toLowerCase(Locale.ROOT);
@@ -290,7 +295,7 @@ public abstract class CommandArgument
     public static CommandArgument buildFromConfig(String suffix, Map<String, Value> config)
     {
         if (!config.containsKey("type"))
-            throw new InternalExpressionException("Custom types should at least specify the base type");
+            throw new InternalExpressionException("Custom types should at least specify the type");
         String baseType = config.get("type").getString();
         if (!builtIns.containsKey(baseType))
             throw new InternalExpressionException("Unknown base type: "+baseType);

src/main/java/carpet/script/command/CommandToken.java

@@ -0,0 +1,68 @@
+package carpet.script.command;
+
+import carpet.script.CarpetScriptHost;
+import carpet.script.value.FunctionValue;
+import com.google.common.collect.Lists;
+import com.mojang.brigadier.builder.ArgumentBuilder;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import net.minecraft.server.command.ServerCommandSource;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static net.minecraft.server.command.CommandManager.literal;
+
+public class CommandToken
+{
+    public String surface;
+    public boolean isArgument;
+
+    private CommandToken(String surface, CommandArgument type )
+    {
+        this.surface = surface;
+        isArgument = type != null;
+    }
+
+    public static CommandToken getToken(String source, CarpetScriptHost host)
+    {
+        // todo add more type checking and return null
+        if (!source.startsWith("<"))
+        {
+            return new CommandToken(source, null);
+        }
+        source = source.substring(1, source.length()-1);
+        CommandArgument arg = CommandArgument.getTypeForArgument(source, host);
+        return new CommandToken(source, arg);
+    }
+
+    public static List<CommandToken> parseSpec(String spec, CarpetScriptHost host) throws CommandSyntaxException
+    {
+        spec = spec.trim();
+        if (spec.isEmpty()) return Collections.emptyList();
+        List<CommandToken> elements = new ArrayList<>();
+        for (String el: spec.split("\\s+"))
+        {
+            CommandToken tok = CommandToken.getToken(el, host);
+            if (tok == null) throw CommandArgument.error("Unrecognized command token: "+ el);
+            elements.add(tok);
+        }
+        return elements;
+    }
+
+    public static String specFromSignature(FunctionValue function)
+    {
+        List<String> tokens = Lists.newArrayList(function.getString());
+        for (String arg : function.getArguments()) tokens.add("<"+arg+">");
+        return String.join(" ", tokens);
+    }
+
+
+    public ArgumentBuilder<ServerCommandSource, ?> getCommandNode(CarpetScriptHost host) throws CommandSyntaxException
+    {
+        if (isArgument)
+            return CommandArgument.argumentNode(surface, host);
+        return literal(surface);
+
+    }
+}