Add arguments validator

app/src/main/java/com/annimon/hotarufx/exceptions/ArgumentsMismatchException.java

@@ -0,0 +1,14 @@
+package com.annimon.hotarufx.exceptions;
+
+import com.annimon.hotarufx.lexer.SourcePosition;
+
+public class ArgumentsMismatchException extends HotaruRuntimeException {
+
+    public ArgumentsMismatchException(String message) {
+        super(message);
+    }
+
+    public ArgumentsMismatchException(String message, SourcePosition start, SourcePosition end) {
+        super(message, start, end);
+    }
+}

app/src/main/java/com/annimon/hotarufx/lib/Validator.java

@@ -0,0 +1,51 @@
+package com.annimon.hotarufx.lib;
+
+import com.annimon.hotarufx.exceptions.ArgumentsMismatchException;
+import com.annimon.hotarufx.exceptions.TypeException;
+import lombok.RequiredArgsConstructor;
+import lombok.val;
+
+@RequiredArgsConstructor(staticName = "with")
+public class Validator {
+
+    private final Value[] args;
+
+    public Validator check(int expected) {
+        if (args.length != expected) throw new ArgumentsMismatchException(String.format(
+                "%d %s expected, got %d", expected, pluralize(expected), args.length));
+        return this;
+    }
+
+    public Validator checkAtLeast(int expected) {
+        if (args.length < expected) throw new ArgumentsMismatchException(String.format(
+                "At least %d %s expected, got %d", expected, pluralize(expected), args.length));
+        return this;
+    }
+
+    public Validator checkOrOr(int expectedOne, int expectedTwo) {
+        if (expectedOne != args.length && expectedTwo != args.length)
+            throw new ArgumentsMismatchException(String.format(
+                    "%d or %d arguments expected, got %d", expectedOne, expectedTwo, args.length));
+        return this;
+    }
+
+    public Validator checkRange(int from, int to) {
+        if (from > args.length || args.length > to)
+            throw new ArgumentsMismatchException(String.format(
+                    "From %d to %d arguments expected, got %d", from, to, args.length));
+        return this;
+    }
+
+    public MapValue requireMapAt(int index) {
+        checkAtLeast(index + 1);
+        val value = args[index];
+        if (value.type() != Types.MAP) {
+            throw new TypeException(String.format("Map required at %d argument", index));
+        }
+        return (MapValue) value;
+    }
+
+    private static String pluralize(int count) {
+        return (count == 1) ? "argument" : "arguments";
+    }
+}