/**
 * 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 org.apache.camel.language.ref;

import org.apache.camel.Exchange;
import org.apache.camel.Expression;
import org.apache.camel.IsSingleton;
import org.apache.camel.Predicate;
import org.apache.camel.builder.ExpressionBuilder;
import org.apache.camel.builder.PredicateBuilder;
import org.apache.camel.impl.ExpressionAdapter;
import org.apache.camel.spi.Language;

/**
 * A language for referred expressions.
 */
public class RefLanguage implements Language, IsSingleton {

    public static Expression ref(Object value) {
        String ref = value.toString();
        return ExpressionBuilder.refExpression(ref);
    }

    public Predicate createPredicate(String expression) {
        return PredicateBuilder.toPredicate(createExpression(expression));
    }

    public Expression createExpression(final String expression) {
        final Expression exp = RefLanguage.ref(expression);
        return new ExpressionAdapter() {
            public Object evaluate(Exchange exchange) {
                Expression lookup = exp.evaluate(exchange, Expression.class);
                if (lookup != null) {
                    return lookup.evaluate(exchange, Object.class);
                } else {
                    throw new IllegalArgumentException("Cannot find expression in registry with ref: " + expression);
                }
            }

            public String toString() {
                return exp.toString();
            }
        };
    }

    public boolean isSingleton() {
        return true;
    }
}
