src/de/steamwar/command/AbstractValidator.java

@@ -19,6 +19,12 @@
 
 package de.steamwar.command;
 
+import lombok.RequiredArgsConstructor;
+
+import java.util.function.BooleanSupplier;
+import java.util.function.Function;
+import java.util.function.Predicate;
+
 @FunctionalInterface
 public interface AbstractValidator<K, T> {
 
@@ -32,8 +38,57 @@ public interface AbstractValidator<K, T> {
      */
     boolean validate(K sender, T value, MessageSender messageSender);
 
+    default <C> Validator<C> validate(C value, MessageSender messageSender) {
+        return new Validator<>(value, messageSender);
+    }
+
+    @RequiredArgsConstructor
+    class Validator<C> {
+        private final C value;
+        private final MessageSender messageSender;
+
+        private boolean valid = true;
+
+        public <M> Validator<M> map(Function<C, M> mapper) {
+            return new Validator<>(mapper.apply(value), messageSender).set(valid);
+        }
+
+        public Validator<C> set(boolean value) {
+            this.valid = value;
+            return this;
+        }
+
+        public Validator<C> and(Predicate<C> predicate) {
+            valid &= predicate.test(value);
+            return this;
+        }
+
+        public Validator<C> or(Predicate<C> predicate) {
+            valid |= predicate.test(value);
+            return this;
+        }
+
+        public Validator<C> errorMessage(String s, Object... args) {
+            if (!valid) messageSender.send(s, args);
+            return this;
+        }
+
+        public boolean result() {
+            return valid;
+        }
+    }
+
     @FunctionalInterface
     interface MessageSender {
         void send(String s, Object... args);
+
+        default boolean send(boolean condition, String s, Object... args) {
+            if (condition) send(s, args);
+            return condition;
+        }
+
+        default boolean send(BooleanSupplier condition, String s, Object... args) {
+            return send(condition.getAsBoolean(), s, args);
+        }
     }
 }