/**
* Copyright (c) 2012-2015 Edgar Espina
*
* This file is part of Handlebars.java.
*
* Licensed 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 com.github.jknack.handlebars.helper;
import static org.apache.commons.lang3.Validate.notNull;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import com.github.jknack.handlebars.Handlebars;
import com.github.jknack.handlebars.Helper;
import com.github.jknack.handlebars.Options;
/**
* Wrap a method as Handlebars helper.
*
* @author edgar.espina
* @see Handlebars#registerHelpers(Object)
* @see Handlebars#registerHelpers(Class)
*/
public class MethodHelper implements Helper<Object> {
/** No args. */
private static final Object[] NO_ARGS = new Object[0];
/**
* The source or instance object. Might be null.
*/
private Object source;
/**
* The method to invoke. Required.
*/
private Method method;
/**
* Creates a new {@link MethodHelper}.
*
* @param method The method to invoke. Required.
* @param source The source or instance object. Might be null.
*/
public MethodHelper(final Method method, final Object source) {
this.method = notNull(method, "A helper method is required.");
this.source = source;
}
@Override
public Object apply(final Object context, final Options options) throws IOException {
try {
Class<?>[] paramTypes = method.getParameterTypes();
Object[] args = NO_ARGS;
if (paramTypes.length > 0) {
args = new Object[paramTypes.length];
args[0] = paramTypes[0] == Options.class ? options : context;
for (int i = 1; i < args.length; i++) {
if (paramTypes[i] == Options.class) {
args[i] = options;
} else {
args[i] = options.param(i - 1);
}
}
}
return (CharSequence) method.invoke(source, args);
} catch (ArrayIndexOutOfBoundsException ex) {
throw new IllegalArgumentException(
"could not execute helper: " + toString(method) + ", with the given arguments: "
+ toString(options.params),
ex);
} catch (InvocationTargetException ex) {
throw launderThrowable(ex.getCause());
} catch (IllegalAccessException ex) {
throw new IllegalStateException("could not execute helper: " + toString(method), ex);
}
}
/**
* Describe params.
*
* @param params Params to describe.
* @return ToString of params
*/
private String toString(final Object[] params) {
StringBuilder buff = new StringBuilder();
buff.append("[");
for (Object param : params) {
buff.append(param == null ? "null" : param.getClass().getSimpleName()).append(", ");
}
if (buff.length() > 1) {
buff.setLength(buff.length() - 2);
}
return buff.append("]").toString();
}
/**
* Describes method.
*
* @param method Method to describe.
* @return ToString of method.
*/
private String toString(final Method method) {
return method.getName() + "(" + toString(method.getParameterTypes()) + ")";
}
/**
* Describe types.
*
* @param types Types to describe.
* @return ToString of types.
*/
private String toString(final Class<?>[] types) {
StringBuilder buff = new StringBuilder();
for (Class<?> type : types) {
buff.append(type.getSimpleName()).append(", ");
}
if (buff.length() > 0) {
buff.setLength(buff.length() - 2);
}
return buff.toString();
}
/**
* Return a runtime exception or throw an {@link IOException}.
*
* @param cause The invocation cause.
* @return A runtime exception or throw an {@link IOException}.
* @throws IOException If the cause is an {@link IOException}.
*/
private RuntimeException launderThrowable(final Throwable cause) throws IOException {
if (cause instanceof RuntimeException) {
return (RuntimeException) cause;
}
if (cause instanceof IOException) {
throw (IOException) cause;
}
return new IllegalStateException("could not execute helper: " + method.getName(), cause);
}
}