/*
 *  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
 *
 *    https://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.grails.cli.compiler;

import java.lang.reflect.Modifier;
import java.util.ArrayList;

import org.codehaus.groovy.ast.ASTNode;
import org.codehaus.groovy.ast.ClassCodeVisitorSupport;
import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.ModuleNode;
import org.codehaus.groovy.ast.PropertyNode;
import org.codehaus.groovy.ast.expr.ClosureExpression;
import org.codehaus.groovy.ast.stmt.BlockStatement;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.transform.ASTTransformation;

import org.springframework.core.annotation.Order;

/**
 * {@link ASTTransformation} to resolve beans declarations inside application source
 * files. Users only need to define a <code>beans{}</code> DSL element, and this
 * transformation will remove it and make it accessible to the Spring application through
 * an interface.
 *
 * @author Dave Syer
 * @since 1.0.0
 */
@Order(GroovyBeansTransformation.ORDER)
public class GroovyBeansTransformation implements ASTTransformation {

    /**
     * The order of the transformation.
     */
    public static final int ORDER = DependencyManagementBomTransformation.ORDER + 200;

    @Override
    public void visit(ASTNode[] nodes, SourceUnit source) {
        for (ASTNode node : nodes) {
            if (node instanceof ModuleNode) {
                ModuleNode module = (ModuleNode) node;
                for (ClassNode classNode : new ArrayList<>(module.getClasses())) {
                    if (classNode.isScript()) {
                        classNode.visitContents(new ClassVisitor(source, classNode));
                    }
                }
            }
        }
    }

    private class ClassVisitor extends ClassCodeVisitorSupport {

        private static final String SOURCE_INTERFACE = "org.springframework.boot.BeanDefinitionLoader.GroovyBeanDefinitionSource";

        private static final String BEANS = "beans";

        private final SourceUnit source;

        private final ClassNode classNode;

        private boolean xformed = false;

        ClassVisitor(SourceUnit source, ClassNode classNode) {
            this.source = source;
            this.classNode = classNode;
        }

        @Override
        protected SourceUnit getSourceUnit() {
            return this.source;
        }

        @Override
        public void visitBlockStatement(BlockStatement block) {
            if (block.isEmpty() || this.xformed) {
                return;
            }
            ClosureExpression closure = beans(block);
            if (closure != null) {
                // Add a marker interface to the current script
                this.classNode.addInterface(ClassHelper.make(SOURCE_INTERFACE));
                // Implement the interface by adding a public read-only property with the
                // same name as the method in the interface (getBeans). Make it return the
                // closure.
                this.classNode.addProperty(new PropertyNode(BEANS, Modifier.PUBLIC | Modifier.FINAL,
                        ClassHelper.CLOSURE_TYPE.getPlainNodeReference(), this.classNode, closure, null, null));
                // Only do this once per class
                this.xformed = true;
            }
        }

        /**
         * Extract a top-level <code>beans{}</code> closure from inside this block if
         * there is one. Removes it from the block at the same time.
         * @param block a block statement (class definition)
         * @return a beans Closure if one can be found, null otherwise
         */
        private ClosureExpression beans(BlockStatement block) {
            return AstUtils.getClosure(block, BEANS, true);
        }

    }

}
