MethodReference.java

/*
 * Copyright 2023 Terminal Utils Authors
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package net.morimekta.terminal.args.reference;

import net.morimekta.terminal.args.ArgException;

import java.lang.annotation.Annotation;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

/**
 * Reference backed by a getter method on the config object.
 */
public class MethodReference implements Reference {
    final Object           instance;
    final Method           getter;
    final AccessibleObject annotationRef;

    public MethodReference(
            Object instance,
            Method getter,
            AccessibleObject annotationRef) {
        this.instance = instance;
        this.getter = getter;
        this.annotationRef = annotationRef;
    }

    @Override
    public String getName() {
        return getter.getName();
    }

    @Override
    public String getUsage() {
        return "Apply " + getName() + "().";
    }

    @Override
    public Object get() {
        if (getter == null) {
            return null;
        }
        return safeInvoke(getter, instance);
    }

    @Override
    public boolean isAnnotationPresent(Class<? extends Annotation> annotation) {
        return annotationRef.isAnnotationPresent(annotation) ||
               (getter != null && getter.isAnnotationPresent(annotation));
    }

    @Override
    public <A extends Annotation> A getAnnotation(Class<A> annotation) {
        if (getter != null && getter.isAnnotationPresent(annotation)) {
            return getter.getAnnotation(annotation);
        }
        if (annotationRef.isAnnotationPresent(annotation)) {
            return annotationRef.getAnnotation(annotation);
        }
        return null;
    }

    @Override
    public Class<?> getType() {
        return getter.getReturnType();
    }

    @Override
    public Type getGenericType() {
        return getter.getGenericReturnType();
    }

    static Object safeInvoke(Method method, Object instance, Object... params) {
        try {
            return method.invoke(instance, params);
        } catch (InvocationTargetException e) {
            if (e.getCause().getMessage() == null) {
                throw new ArgException(
                        e.getCause().getClass().getSimpleName(),
                        e.getCause());
            }
            throw new ArgException(e.getCause().getMessage(), e.getCause());
        } catch (IllegalAccessException e) {
            throw new ArgException(e.getMessage(), e.getCause());
        }
    }
}