/*
 *  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 groovy.util.logging;

import groovy.lang.GroovyClassLoader;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.expr.ArgumentListExpression;
import org.codehaus.groovy.ast.expr.AttributeExpression;
import org.codehaus.groovy.ast.expr.BooleanExpression;
import org.codehaus.groovy.ast.expr.ClassExpression;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.MethodCallExpression;
import org.codehaus.groovy.ast.expr.TernaryExpression;
import org.codehaus.groovy.transform.GroovyASTTransformationClass;
import org.codehaus.groovy.transform.LogASTTransformation;
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;
import java.util.Locale;

/**
 * This local transform adds a logging ability to your program using
 * Log4j logging. Every method call on a unbound variable named <i>log</i>
 * will be mapped to a call to the logger. For this a <i>log</i> 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.
 * <pre>
 * log.name(exp)
 * </pre>is mapped to
 * <pre>
 * if (log.isNameEnabled() {
 *    log.name(exp)
 * }</pre>
 * Here name is a place holder for info, debug, warning, error, etc.
 * 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 Hamlet D'Arcy
 * @author Tomek Bujok
 * @since 1.8.0
 */
@java.lang.annotation.Documented
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.TYPE})
@GroovyASTTransformationClass("org.codehaus.groovy.transform.LogASTTransformation")
public @interface Log4j {
    String value() default "log";
    String category() default LogASTTransformation.DEFAULT_CATEGORY_NAME;
    Class<? extends LogASTTransformation.LoggingStrategy> loggingStrategy() default Log4jLoggingStrategy.class;

    public static class Log4jLoggingStrategy extends LogASTTransformation.AbstractLoggingStrategy {
        private static final String LOGGER_NAME = "org.apache.log4j.Logger";
        private static final String PRIORITY_NAME = "org.apache.log4j.Priority";

        protected Log4jLoggingStrategy(final GroovyClassLoader loader) {
            super(loader);
        }

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

        public boolean isLoggingMethod(String methodName) {
            return methodName.matches("fatal|error|warn|info|debug|trace");
        }

        public Expression wrapLoggingMethodCall(Expression logVariable, String methodName, Expression originalExpression) {
            final MethodCallExpression condition;
            if (!"trace".equals(methodName)) {
                AttributeExpression logLevelExpression = new AttributeExpression(
                        new ClassExpression(classNode(PRIORITY_NAME)),
                        new ConstantExpression(methodName.toUpperCase(Locale.ENGLISH)));
                ArgumentListExpression args = new ArgumentListExpression();
                args.addExpression(logLevelExpression);
                condition = new MethodCallExpression(logVariable, "isEnabledFor", args);
            } else {
                // log4j api is inconsistent, so trace requires special handling
                condition = new MethodCallExpression(
                        logVariable,
                        "is" + methodName.substring(0, 1).toUpperCase(Locale.ENGLISH) + methodName.substring(1, methodName.length()) + "Enabled",
                        ArgumentListExpression.EMPTY_ARGUMENTS);
            }
            condition.setImplicitThis(false);

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