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/*
 * Copyright 2003-2012 the original author or authors.
 *
 * 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 groovy.util.logging;

import groovy.lang.GroovyClassLoader;
import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.transform.GroovyASTTransformationClass;
import org.codehaus.groovy.transform.LogASTTransformation;
import org.codehaus.groovy.transform.LogASTTransformation.LoggingStrategy;
import org.objectweb.asm.Opcodes;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * This local transform adds a logging ability to your program using
 * java.util.logging. Every method call on a unbound variable named log
 * will be mapped to a call to the logger. For this a log field will be
 * inserted in the class. If the field already exists the usage of this transform
 * will cause a compilation error. The method name will be used to determine
 * what to call on the logger.
 *  * log.name(exp)
 * is mapped to
 *  * if (log.isLoggable(Level.NAME) {
 *    log.name(exp)
 * }
 * Here name is a place holder for info, fine, finer, finest, config, warning, severe.
 * NAME is name transformed to upper case. if anything else is used it will result in
 * an exception at runtime. If the expression exp is a constant or only a variable access
 * the method call will not be transformed. But this will still cause a call on the injected
 * logger.
 *
 * @author Guillaume Laforge
 * @author Jochen Theodorou
 * @author Dinko Srkoc
 * @author Hamlet D'Arcy
 * @author Raffaele Cigni
 * @author Alberto Vilches Raton
 * @since 1.8.0
 */
@java.lang.annotation.Documented
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.TYPE})
@GroovyASTTransformationClass("org.codehaus.groovy.transform.LogASTTransformation")
public @interface Log {
    String value() default "log";
    Class loggingStrategy() default JavaUtilLoggingStrategy.class;

    /**
     * This class contains the logic of how to weave a Java Util Logging logger into the host class.
     */
    public static class JavaUtilLoggingStrategy extends LogASTTransformation.AbstractLoggingStrategy {

        private static final ClassNode LOGGER_CLASSNODE = ClassHelper.make(java.util.logging.Logger.class);
        private static final ClassNode LEVEL_CLASSNODE = ClassHelper.make(java.util.logging.Level.class);

        protected JavaUtilLoggingStrategy(final GroovyClassLoader loader) {
            super(loader);
        }

        public FieldNode addLoggerFieldToClass(ClassNode classNode, String logFieldName) {
            return classNode.addField(logFieldName,
                        Opcodes.ACC_FINAL | Opcodes.ACC_TRANSIENT | Opcodes.ACC_STATIC | Opcodes.ACC_PRIVATE,
                        LOGGER_CLASSNODE,
                        new MethodCallExpression(
                                new ClassExpression(LOGGER_CLASSNODE),
                                "getLogger",
                                new ConstantExpression(classNode.getName())));
        }

        public boolean isLoggingMethod(String methodName) {
            return methodName.matches("severe|warning|info|fine|finer|finest");
        }

        public Expression wrapLoggingMethodCall(Expression logVariable, String methodName, Expression originalExpression) {
            AttributeExpression logLevelExpression = new AttributeExpression(
                    new ClassExpression(LEVEL_CLASSNODE),
                    new ConstantExpression(methodName.toUpperCase()));

            ArgumentListExpression args = new ArgumentListExpression();
            args.addExpression(logLevelExpression);
            MethodCallExpression condition = new MethodCallExpression(logVariable, "isLoggable", args);

            return new TernaryExpression(
                    new BooleanExpression(condition),
                    originalExpression,
                    ConstantExpression.NULL);

        }
    }
}