initial commit

common/site/lab0x13/scrow/commands/CommandHandler.java

@@ -0,0 +1,67 @@
+package site.lab0x13.scrow.commands;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.literal.RootLiteral;
+import site.lab0x13.scrow.commands.parser.NodeTreeWalker;
+import site.lab0x13.scrow.commands.parser.WalkResult;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static java.util.Objects.requireNonNull;
+
+public class CommandHandler<C extends CommandContext<C>> {
+
+    private final NodeTreeWalker<C> nodeTreeWalker;
+    private final PlatformAdapter<C> platformAdapter;
+
+    public CommandHandler(PlatformAdapter<C> platformAdapter) {
+        this.nodeTreeWalker = new NodeTreeWalker<>(platformAdapter);
+        this.platformAdapter = platformAdapter;
+    }
+
+    public void invoke(RootLiteral<C> rootLiteral, C ctx, Stream<String> args) {
+        var walkResult = nodeTreeWalker.walk(ctx, rootLiteral, args.iterator());
+        if (!walkResult.isValidUsage()) {
+            platformAdapter.sendMessage(ctx, rootLiteral.style().err(walkResult.message()));
+            return;
+        }
+        requireNonNull(walkResult.lastLiteral().executor())
+                .execute(walkResult.ctx())
+                .exceptionally(ex -> {
+                    platformAdapter.sendMessage(ctx, rootLiteral.style().exception(ex));
+                    return null;
+                });
+    }
+
+    public List<String> suggest(RootLiteral<C> rootLiteral, C ctx, String[] args, boolean trailingSpace) {
+        var walkResult = nodeTreeWalker.walk(ctx, rootLiteral, Arrays.stream(args).iterator());
+        Stream<String> stream;
+        String input = null;
+        switch (walkResult) {
+            case WalkResult.LiteralUnknown<C> res -> {
+                stream = res.lastLiteral().subLiteralNames().stream();
+                input = res.input();
+            }
+            case WalkResult.ArgumentIllegal<C> res -> {
+                stream = res.arg().suggestionProvider().suggest(ctx, res.input()).stream();
+                input = res.input();
+            }
+            case WalkResult.LiteralExpected<C> res when trailingSpace ->
+                    stream = res.lastLiteral().subLiteralNames().stream();
+            case WalkResult.ArgumentExpected<C> res when trailingSpace ->
+                    stream = res.arg().suggestionProvider().suggest(ctx, "").stream();
+            default -> {
+                return Collections.emptyList();
+            }
+        }
+
+        if (input == null) return stream.toList();
+        final var finalInput = input;
+        return stream
+                .filter(s -> s.startsWith(finalInput))
+                .toList();
+    }
+}

common/site/lab0x13/scrow/commands/IScrowCommands.java

@@ -0,0 +1,12 @@
+package site.lab0x13.scrow.commands;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.literal.RootLiteral;
+
+public interface IScrowCommands<C extends CommandContext<C>> {
+
+    void register(RootLiteral<C> rootLiteral);
+
+    @Nullable RootLiteral<C> getRootLiteral(String name);
+}

common/site/lab0x13/scrow/commands/PlatformAdapter.java

@@ -0,0 +1,10 @@
+package site.lab0x13.scrow.commands;
+
+import net.kyori.adventure.text.Component;
+
+public interface PlatformAdapter<C> {
+
+    boolean checkPermission(C ctx, String permission);
+
+    void sendMessage(C ctx, Component message);
+}

common/site/lab0x13/scrow/commands/model/AbstractCommandContext.java

@@ -0,0 +1,23 @@
+package site.lab0x13.scrow.commands.model;
+
+import site.lab0x13.scrow.commands.model.argument.Argument;
+import site.lab0x13.scrow.commands.model.argument.ParsedArgument;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public abstract class AbstractCommandContext<C extends CommandContext<C>> implements CommandContext<C> {
+
+    private final Map<String, ParsedArgument<?, ?>> parsedArguments = new HashMap<>();
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <V> ParsedArgument<C, V> getArgument(String id) {
+        return (ParsedArgument<C, V>) parsedArguments.get(id);
+    }
+
+    @Override
+    public <V> void addParsedArgument(Argument<?, V> argument, String rawValue, V value) {
+        parsedArguments.put(argument.id(), new ParsedArgument<>(argument, rawValue, value));
+    }
+}

common/site/lab0x13/scrow/commands/model/CommandContext.java

@@ -0,0 +1,27 @@
+package site.lab0x13.scrow.commands.model;
+
+import site.lab0x13.scrow.commands.model.argument.Argument;
+import site.lab0x13.scrow.commands.model.argument.ParsedArgument;
+
+/**
+ * @param <C> argument of this
+ */
+public interface CommandContext<C extends CommandContext<C>> {
+
+    <V> ParsedArgument<C, V> getArgument(String id);
+
+    default <V> V getArg(String id) {
+        ParsedArgument<C, V> arg = getArgument(id);
+        return arg.value();
+    }
+
+    default <V> V getArg(Argument<C, V> arg) {
+        return getArg(arg.id());
+    }
+
+    default <V> ParsedArgument<C, V> getArgument(Argument<C, V> arg) {
+        return getArgument(arg.id());
+    }
+
+    <V> void addParsedArgument(Argument<?, V> argument, String rawValue, V value);
+}

common/site/lab0x13/scrow/commands/model/CommandExecutor.java

@@ -0,0 +1,22 @@
+package site.lab0x13.scrow.commands.model;
+
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * @param <C> argument of command context
+ */
+public interface CommandExecutor<C extends CommandContext<C>> {
+
+    CompletableFuture<?> execute(C ctx);
+
+    interface Sync<C extends CommandContext<C>> extends CommandExecutor<C> {
+
+        void executeSync(C ctx);
+
+        @Override
+        default CompletableFuture<?> execute(C ctx) {
+            executeSync(ctx);
+            return CompletableFuture.completedFuture(Void.TYPE);
+        }
+    }
+}

common/site/lab0x13/scrow/commands/model/Node.java

@@ -0,0 +1,6 @@
+package site.lab0x13.scrow.commands.model;
+
+public interface Node<C extends CommandContext<C>> {
+
+    SuggestionProvider<C> suggestionProvider();
+}

common/site/lab0x13/scrow/commands/model/SuggestionProvider.java

@@ -0,0 +1,16 @@
+package site.lab0x13.scrow.commands.model;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * @param <C> argument of command context
+ */
+public interface SuggestionProvider<C extends CommandContext<C>> {
+
+    static <C extends CommandContext<C>> SuggestionProvider<C> none() {
+        return (_, _) -> Collections.emptyList();
+    }
+
+    List<String> suggest(C ctx, String input);
+}

common/site/lab0x13/scrow/commands/model/argument/Argument.java

@@ -0,0 +1,41 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import com.leakyabstractions.result.api.Result;
+import com.leakyabstractions.result.core.Results;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.Node;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+
+import java.util.List;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of argument value
+ */
+public record Argument<C extends CommandContext<C>, V>(
+        String id,
+        ArgumentType<C, V> type,
+        List<ArgumentRequirement<C, V>> requirements,
+        SuggestionProvider<C> suggestionProvider,
+        DefaultValueProvider<C, V> defaultValueProvider
+) implements Node<C> {
+
+    public static <C extends CommandContext<C>, V> ArgumentBuilder<C, V> builder(String id, ArgumentType<C, V> type) {
+        return new ArgumentBuilder<>(id, type);
+    }
+
+    public Result<ParsedArgument<C, V>, String> parse(C ctx, String rawInput) {
+        var parseResult = type.parseInput(rawInput);
+        if (parseResult.hasFailure())
+            return parseResult.mapSuccess(_ -> null);
+        var value = parseResult.getSuccess().orElseThrow();
+
+        for (var requirement : requirements) {
+            var isAllowed = requirement.predicate().check(ctx, value);
+            if (!isAllowed)
+                return Results.failure(requirement.errorMessage());
+        }
+
+        return Results.success(new ParsedArgument<>(this, rawInput, value));
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/ArgumentBuilder.java

@@ -0,0 +1,55 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of argument value
+ */
+public final class ArgumentBuilder<C extends CommandContext<C>, V> {
+
+    private final String id;
+    private final ArgumentType<C, V> type;
+    private DefaultValueProvider<C, V> defaultValueProvider = DefaultValueProvider.none();
+    private @Nullable SuggestionProvider<C> suggestionProvider = null;
+
+    private final List<ArgumentRequirement<C, V>> requirements = new ArrayList<>();
+
+    ArgumentBuilder(String id, ArgumentType<C, V> type) {
+        this.id = id;
+        this.type = type;
+    }
+
+    public ArgumentBuilder<C, V> withRequirement(ArgumentPredicate<C, V> predicate, String errorMessage) {
+        this.requirements.add(new ArgumentRequirement<>(predicate, errorMessage));
+        return this;
+    }
+
+    public ArgumentBuilder<C, V> withDefaultValue(@Nullable DefaultValueProvider<C, V> defaultValue) {
+        this.defaultValueProvider = defaultValue;
+        return this;
+    }
+
+    /**
+     * @param suggestionProvider if null, use the argument's suggestion provider
+     */
+    public ArgumentBuilder<C, V> withSuggestionProvider(@Nullable SuggestionProvider<C> suggestionProvider) {
+        this.suggestionProvider = suggestionProvider;
+        return this;
+    }
+
+    public Argument<C, V> build() {
+        return new Argument<>(
+                id,
+                type,
+                new ArrayList<>(requirements),
+                suggestionProvider != null ? suggestionProvider : type.defaultSuggestionProvider(),
+                defaultValueProvider
+        );
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/ArgumentPredicate.java

@@ -0,0 +1,12 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of argument value
+ */
+@FunctionalInterface
+public interface ArgumentPredicate<C extends CommandContext<C>, V> {
+    boolean check(C ctx, V value);
+}

common/site/lab0x13/scrow/commands/model/argument/ArgumentRequirement.java

@@ -0,0 +1,13 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of argument value
+ */
+public record ArgumentRequirement<C extends CommandContext<C>, V>(
+     ArgumentPredicate<C, V> predicate,
+     String errorMessage
+) {
+}

common/site/lab0x13/scrow/commands/model/argument/ArgumentType.java

@@ -0,0 +1,28 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import com.leakyabstractions.result.api.Result;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of parsed argument value
+ */
+public interface ArgumentType<C extends CommandContext<C>, V> {
+
+    Result<V, String> parseInput(String input);
+
+    /**
+     * @return default suggestion provider for the argument, if not overwritten by the argument
+     */
+    SuggestionProvider<C> defaultSuggestionProvider();
+
+    /**
+     * @return whether this argument is greedy. Greedy arguments consume all remaining input instead of a single word.
+     * For example, given the 2 words "hello" "world" as input, a greedy argument parses "hello world" as a single value.
+     * Greedy arguments may not be followed by another argument or a literal
+     */
+    default boolean greedy() {
+        return false;
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/DefaultValueProvider.java

@@ -0,0 +1,14 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+@FunctionalInterface
+public interface DefaultValueProvider<C extends CommandContext<C>, V> {
+
+    static <V, C extends CommandContext<C>> DefaultValueProvider<C, V> none() {
+        return _ -> null;
+    }
+
+    @Nullable V getDefault(C ctx);
+}

common/site/lab0x13/scrow/commands/model/argument/ParsedArgument.java

@@ -0,0 +1,14 @@
+package site.lab0x13.scrow.commands.model.argument;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+/**
+ * @param <C> argument of command context
+ * @param <V> argument of argument value
+ */
+public record ParsedArgument<C extends CommandContext<C>, V>(
+        Argument<C, V> argument,
+        String rawValue,
+        V value
+) {
+}

common/site/lab0x13/scrow/commands/model/argument/types/BooleanArgumentType.java

@@ -0,0 +1,23 @@
+package site.lab0x13.scrow.commands.model.argument.types;
+
+import com.leakyabstractions.result.api.Result;
+import com.leakyabstractions.result.core.Results;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+import site.lab0x13.scrow.commands.model.argument.ArgumentType;
+
+import java.util.List;
+
+public class BooleanArgumentType<C extends CommandContext<C>> implements ArgumentType<C, Boolean> {
+
+    @Override
+    public Result<Boolean, String> parseInput(String input) {
+        return Results.ofCallable(() -> Boolean.parseBoolean(input))
+                .mapFailure(_ -> "Must be true or false.");
+    }
+
+    @Override
+    public SuggestionProvider<C> defaultSuggestionProvider() {
+        return (_, _) -> List.of("true", "false");
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/types/DoubleArgumentType.java

@@ -0,0 +1,20 @@
+package site.lab0x13.scrow.commands.model.argument.types;
+
+import com.leakyabstractions.result.api.Result;
+import com.leakyabstractions.result.core.Results;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+import site.lab0x13.scrow.commands.model.argument.ArgumentType;
+
+public class DoubleArgumentType<C extends CommandContext<C>> implements ArgumentType<C, Double> {
+    @Override
+    public Result<Double, String> parseInput(String input) {
+        return Results.ofCallable(() -> Double.parseDouble(input))
+                .mapFailure(_ -> "Not a valid double.");
+    }
+
+    @Override
+    public SuggestionProvider<C> defaultSuggestionProvider() {
+        return SuggestionProvider.none();
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/types/IntegerArgumentType.java

@@ -0,0 +1,21 @@
+package site.lab0x13.scrow.commands.model.argument.types;
+
+import com.leakyabstractions.result.api.Result;
+import com.leakyabstractions.result.core.Results;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+import site.lab0x13.scrow.commands.model.argument.ArgumentType;
+
+public class IntegerArgumentType<C extends CommandContext<C>> implements ArgumentType<C, Integer> {
+
+    @Override
+    public Result<Integer, String> parseInput(String string) {
+        return Results.ofCallable(() -> Integer.parseInt(string))
+                .mapFailure(_ -> "Not a number.");
+    }
+
+    @Override
+    public SuggestionProvider<C> defaultSuggestionProvider() {
+        return SuggestionProvider.none();
+    }
+}

common/site/lab0x13/scrow/commands/model/argument/types/StringArgumentType.java

@@ -0,0 +1,25 @@
+package site.lab0x13.scrow.commands.model.argument.types;
+
+import com.leakyabstractions.result.api.Result;
+import com.leakyabstractions.result.core.Results;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+import site.lab0x13.scrow.commands.model.argument.ArgumentType;
+
+public record StringArgumentType<C extends CommandContext<C>>(boolean greedy)
+        implements ArgumentType<C, String> {
+
+    public StringArgumentType() {
+        this(false);
+    }
+
+    @Override
+    public Result<String, String> parseInput(String string) {
+        return Results.success(string);
+    }
+
+    @Override
+    public SuggestionProvider<C> defaultSuggestionProvider() {
+        return SuggestionProvider.none();
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/DynamicLiteral.java

@@ -0,0 +1,46 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.CommandExecutor;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+
+import java.util.List;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+public abstract class DynamicLiteral<C extends CommandContext<C>> implements Literal<C>{
+
+    private final List<String> names;
+    private final @Nullable CommandExecutor<C> executor;
+    private final List<Argument<C, ?>> arguments;
+    private final String permission;
+
+    public DynamicLiteral(List<String> names, @Nullable CommandExecutor<C> executor, List<Argument<C, ?>> arguments, String permission) {
+        checkArgument(!names.isEmpty(), "at least one name expected");
+        this.names = names;
+        this.executor = executor;
+        this.arguments = arguments;
+        this.permission = permission;
+    }
+
+    @Override
+    public List<String> names() {
+        return names;
+    }
+
+    @Override
+    public @Nullable CommandExecutor<C> executor() {
+        return executor;
+    }
+
+    @Override
+    public List<Argument<C, ?>> arguments() {
+        return arguments;
+    }
+
+    @Override
+    public String permission() {
+        return permission;
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/DynamicLiteralBuilder.java

@@ -0,0 +1,55 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public final class DynamicLiteralBuilder<C extends CommandContext<C>> extends LiteralBuilder<C, DynamicLiteralBuilder<C>> {
+
+    private Supplier<List<String>> subLiteralNamesSupplier = Collections::emptyList;
+    private Function<String, @Nullable Literal<C>> subLiteralProvider = _ -> null;
+
+    DynamicLiteralBuilder(String... names) {
+        super(names);
+    }
+
+    @Override
+    protected DynamicLiteralBuilder<C> getThis() {
+        return this;
+    }
+
+    @Override
+    public Literal<C> build() {
+        return new DynamicLiteral<>(
+                Arrays.asList(this.names),
+                this.executor,
+                this.arguments,
+                this.permission
+        ) {
+            @Override
+            public @Nullable Literal<C> getSubLiteral(String name) {
+                return subLiteralProvider.apply(name);
+            }
+
+            @Override
+            public List<String> subLiteralNames() {
+                return subLiteralNamesSupplier.get();
+            }
+        };
+    }
+
+    public DynamicLiteralBuilder<C> withSubLiteralNames(Supplier<List<String>> names) {
+        subLiteralNamesSupplier = names;
+        return this;
+    }
+
+    public DynamicLiteralBuilder<C> withSubLiteralProvider(Function<String, @Nullable Literal<C>> literalProvider) {
+        this.subLiteralProvider = literalProvider;
+        return this;
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/Literal.java

@@ -0,0 +1,44 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.CommandExecutor;
+import site.lab0x13.scrow.commands.model.Node;
+import site.lab0x13.scrow.commands.model.SuggestionProvider;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+
+import java.util.List;
+
+/**
+ * @param <C> argument of the command context
+ */
+public interface Literal<C extends CommandContext<C>> extends Node<C> {
+
+    static <C extends CommandContext<C>> StaticLiteralBuilder<C> builder(String... names) {
+        return new StaticLiteralBuilder<>(names);
+    }
+
+    static <C extends CommandContext<C>> DynamicLiteralBuilder<C> dynamic(String... names) {
+        return new DynamicLiteralBuilder<>(names);
+    }
+
+    List<String> names();
+
+    @Nullable CommandExecutor<C> executor();
+
+    @Nullable Literal<C> getSubLiteral(String name);
+
+    /**
+     * @return aliases/names of literals
+     */
+    List<String> subLiteralNames();
+
+    List<Argument<C, ?>> arguments();
+
+    String permission();
+
+    @Override
+    default SuggestionProvider<C> suggestionProvider() {
+        return (_, _) -> subLiteralNames();
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/LiteralBuilder.java

@@ -0,0 +1,53 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.CommandExecutor;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @param <C> argument of command context
+ * @param <B> argument of this/builder
+ */
+public abstract class LiteralBuilder<C extends CommandContext<C>,B extends LiteralBuilder<C, B>> {
+
+    protected final String[] names;
+    protected @Nullable CommandExecutor<C> executor;
+    protected @Nullable String permission;
+    protected final List<Argument<C, ?>> arguments = new ArrayList<>();
+
+    protected abstract B getThis();
+
+    public abstract Literal<C> build();
+
+    protected LiteralBuilder(String... names) {
+        this.names = names;
+    }
+
+    public final RootLiteral<C> asRootLiteral(MessageStyle style) {
+        return new RootLiteralWrapper<>(build(), style);
+    }
+
+    public final B withExecutor(@Nullable CommandExecutor<C> executor) {
+        this.executor = executor;
+        return getThis();
+    }
+
+    public final B withSyncExecutor(@Nullable CommandExecutor.Sync<C> executor) {
+        this.executor = executor;
+        return getThis();
+    }
+
+    public final B withPermission(@Nullable String permission) {
+        this.permission = permission;
+        return getThis();
+    }
+
+    public final B withArgument(Argument<C, ?> argument) {
+        arguments.add(argument);
+        return getThis();
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/MessageStyle.java

@@ -0,0 +1,32 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import net.kyori.adventure.text.Component;
+
+public interface MessageStyle {
+
+    MessageStyle PLAIN = new PlainMessageStyle();
+
+    Component ok(Component msg);
+
+    Component err(Component msg);
+
+    Component exception(Component msg);
+
+    default Component ok(String msg) {
+        return ok(Component.text(msg));
+    }
+
+    default Component err(String msg) {
+        return err(Component.text(msg));
+    }
+
+    default Component exception(String msg) {
+        return exception(Component.text(msg));
+    }
+
+    default Component exception(Throwable ex) {
+        while (ex.getMessage() == null && ex.getCause() != null)
+            ex = ex.getCause();
+        return exception(ex.getMessage());
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/PlainMessageStyle.java

@@ -0,0 +1,20 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import net.kyori.adventure.text.Component;
+
+class PlainMessageStyle implements MessageStyle {
+    @Override
+    public Component ok(Component msg) {
+        return msg;
+    }
+
+    @Override
+    public Component err(Component msg) {
+        return msg;
+    }
+
+    @Override
+    public Component exception(Component msg) {
+        return Component.text("ERROR: ").append(msg);
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/RootLiteral.java

@@ -0,0 +1,8 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+public interface RootLiteral<C extends CommandContext<C>> extends Literal<C>{
+
+    MessageStyle style();
+}

common/site/lab0x13/scrow/commands/model/literal/RootLiteralWrapper.java

@@ -0,0 +1,53 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.CommandExecutor;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+
+import java.util.List;
+
+public class RootLiteralWrapper<C extends CommandContext<C>> implements RootLiteral<C> {
+    private final Literal<C> literal;
+    private final MessageStyle messageStyle;
+
+    public RootLiteralWrapper(Literal<C> literal, MessageStyle messageStyle) {
+        this.literal = literal;
+        this.messageStyle = messageStyle;
+    }
+
+    @Override
+    public MessageStyle style() {
+        return messageStyle;
+    }
+
+    @Override
+    public List<String> names() {
+        return literal.names();
+    }
+
+    @Override
+    public @Nullable CommandExecutor<C> executor() {
+        return literal.executor();
+    }
+
+    @Override
+    public @Nullable Literal<C> getSubLiteral(String name) {
+        return literal.getSubLiteral(name);
+    }
+
+    @Override
+    public List<String> subLiteralNames() {
+        return literal.subLiteralNames();
+    }
+
+    @Override
+    public List<Argument<C, ?>> arguments() {
+        return literal.arguments();
+    }
+
+    @Override
+    public String permission() {
+        return literal.permission();
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/StaticLiteral.java

@@ -0,0 +1,38 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.CommandExecutor;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+
+import java.util.List;
+
+public class StaticLiteral<C extends CommandContext<C>> extends DynamicLiteral<C> {
+
+    private final List<Literal<C>> subLiterals;
+
+    public StaticLiteral(
+            List<String> names,
+            @Nullable CommandExecutor<C> executor,
+            List<Argument<C, ?>> arguments,
+            String permission, List<Literal<C>> subLiterals
+    ) {
+        super(names, executor, arguments, permission);
+        this.subLiterals = subLiterals;
+    }
+
+    @Override
+    public @Nullable Literal<C> getSubLiteral(String name) {
+        return subLiterals.stream()
+                .filter(literal -> literal.names().contains(name))
+                .findAny()
+                .orElse(null);
+    }
+
+    @Override
+    public List<String> subLiteralNames() {
+        return subLiterals.stream()
+                .flatMap(literal -> literal.names().stream())
+                .toList();
+    }
+}

common/site/lab0x13/scrow/commands/model/literal/StaticLiteralBuilder.java

@@ -0,0 +1,37 @@
+package site.lab0x13.scrow.commands.model.literal;
+
+import site.lab0x13.scrow.commands.model.CommandContext;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public final class StaticLiteralBuilder<C extends CommandContext<C>> extends LiteralBuilder<C, StaticLiteralBuilder<C>> {
+
+    private final List<Literal<C>> subLiterals = new ArrayList<>();
+
+    StaticLiteralBuilder(String... names) {
+        super(names);
+    }
+
+    @Override
+    protected StaticLiteralBuilder<C> getThis() {
+        return this;
+    }
+
+    @Override
+    public Literal<C> build() {
+        return new StaticLiteral<>(
+                Arrays.asList(this.names),
+                this.executor,
+                this.arguments,
+                this.permission,
+                this.subLiterals
+        );
+    }
+
+    public StaticLiteralBuilder<C> withSubLiteral(Literal<C> subLiteral) {
+        subLiterals.add(subLiteral);
+        return this;
+    }
+}

common/site/lab0x13/scrow/commands/parser/NodeTreeWalker.java

@@ -0,0 +1,100 @@
+package site.lab0x13.scrow.commands.parser;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.PlatformAdapter;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+import site.lab0x13.scrow.commands.model.literal.Literal;
+import site.lab0x13.scrow.commands.model.literal.RootLiteral;
+
+import java.util.Iterator;
+
+import static java.util.Objects.requireNonNull;
+
+public class NodeTreeWalker<C extends CommandContext<C>> {
+
+    private final PlatformAdapter<C> platformAdapter;
+
+    public NodeTreeWalker(PlatformAdapter<C> platformAdapter) {
+        this.platformAdapter = platformAdapter;
+    }
+
+    public WalkResult<C> walk(
+            C ctx,
+            RootLiteral<C> rootLiteral,
+            Iterator<String> iter
+    ) {
+        var cursor = new Cursor(iter);
+        Literal<C> literal = rootLiteral;
+        String token;
+
+        while (true) {
+            for (var arg : literal.arguments()) {
+                //noinspection unchecked
+                var res = walkArgument(ctx, cursor, literal, (Argument<C, Object>) arg);
+                if (res != null)
+                    return res;
+            }
+
+            token = cursor.nextToken();
+            if (token == null)
+                break;
+            var nextLiteral = literal.getSubLiteral(token);
+            if (nextLiteral == null)
+                return new WalkResult.LiteralUnknown<>(ctx, literal, token);
+            if (nextLiteral.permission() != null && platformAdapter.checkPermission(ctx, nextLiteral.permission()))
+                return new WalkResult.LiteralUnknown<>(ctx, literal, token);
+            literal = nextLiteral;
+        }
+
+        if (!literal.subLiteralNames().isEmpty()) {
+            var isOptional = literal.executor() != null;
+            return new WalkResult.LiteralExpected<>(ctx, literal, isOptional);
+        }
+
+        return new WalkResult.Complete<>(ctx, literal);
+    }
+
+    private @Nullable WalkResult<C> walkArgument(
+            C ctx,
+            Cursor cursor,
+            Literal<C> literal,
+            Argument<C, Object> arg
+    ) {
+        var rawInput = arg.type().greedy() ? cursor.remainingTokens() : cursor.nextToken();
+        if (rawInput == null) {
+            var value = requireNonNull(arg.defaultValueProvider()).getDefault(ctx);
+            if (value == null)
+                return new WalkResult.ArgumentExpected<>(ctx, literal, false, arg);
+            ctx.addParsedArgument(arg, "", value);
+            return null;
+        }
+
+        var parseResult = arg.parse(ctx, rawInput);
+        if (parseResult.hasFailure())
+            return new WalkResult.ArgumentIllegal<>(ctx, literal, false,
+                    parseResult.getFailure().orElseThrow(), arg, rawInput);
+        ctx.addParsedArgument(arg, rawInput, parseResult.getSuccess().orElseThrow().value());
+        return null;
+    }
+
+    private static class Cursor {
+        private final Iterator<String> tokenIter;
+
+        public Cursor(Iterator<String> tokenIter) {
+            this.tokenIter = tokenIter;
+        }
+
+        public @Nullable String nextToken() {
+            if (!tokenIter.hasNext())
+                return null;
+            return tokenIter.next();
+        }
+
+        public @Nullable String remainingTokens() {
+            var builder = new StringBuilder();
+            tokenIter.forEachRemaining(s -> builder.append(' ').append(s));
+            return builder.toString();
+        }
+    }
+}

common/site/lab0x13/scrow/commands/parser/WalkResult.java

@@ -0,0 +1,80 @@
+package site.lab0x13.scrow.commands.parser;
+
+import org.jetbrains.annotations.Nullable;
+import site.lab0x13.scrow.commands.model.CommandContext;
+import site.lab0x13.scrow.commands.model.argument.Argument;
+import site.lab0x13.scrow.commands.model.literal.Literal;
+
+public sealed interface WalkResult<C extends CommandContext<C>> {
+    C ctx();
+
+    Literal<C> lastLiteral();
+
+    boolean isValidUsage();
+
+    @Nullable String message();
+
+    record ArgumentIllegal<C extends CommandContext<C>>(
+            C ctx,
+            Literal<C> lastLiteral,
+            boolean isValidUsage,
+            String message,
+            Argument<C, ?> arg,
+            String input
+    ) implements WalkResult<C> {
+    }
+
+    record ArgumentExpected<C extends CommandContext<C>>(
+            C ctx,
+            Literal<C> lastLiteral,
+            boolean isValidUsage,
+            Argument<C, ?> arg
+    ) implements WalkResult<C> {
+        @Override
+        public String message() {
+            return "Argument expected.";
+        }
+    }
+
+    record LiteralExpected<C extends CommandContext<C>>(
+            C ctx,
+            Literal<C> lastLiteral,
+            boolean isValidUsage
+    ) implements WalkResult<C> {
+        @Override
+        public String message() {
+            return "Literal expected.";
+        }
+    }
+
+    record LiteralUnknown<C extends CommandContext<C>>(
+            C ctx,
+            Literal<C> lastLiteral,
+            String input
+    ) implements WalkResult<C> {
+        @Override
+        public boolean isValidUsage() {
+            return false;
+        }
+
+        @Override
+        public String message() {
+            return "Unknown literal \"" + input + "\".";
+        }
+    }
+
+    record Complete<C extends CommandContext<C>>(
+            C ctx,
+            Literal<C> lastLiteral
+    ) implements WalkResult<C> {
+        @Override
+        public boolean isValidUsage() {
+            return true;
+        }
+
+        @Override
+        public @Nullable String message() {
+            return null;
+        }
+    }
+}