/*
 *  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.codehaus.groovy.transform;

import groovy.lang.GroovyClassLoader;
import groovy.transform.AnnotationCollector;
import groovy.transform.AnnotationCollectorMode;
import org.codehaus.groovy.ast.AnnotatedNode;
import org.codehaus.groovy.ast.AnnotationNode;
import org.codehaus.groovy.ast.ClassCodeVisitorSupport;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.control.CompilePhase;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.control.messages.ExceptionMessage;
import org.codehaus.groovy.control.messages.SimpleMessage;
import org.codehaus.groovy.transform.trait.TraitASTTransformation;
import org.codehaus.groovy.transform.trait.Traits;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Stream;

import static org.codehaus.groovy.transform.stc.StaticTypeCheckingSupport.evaluateExpression;

/**
 * Walks the AST and collects references to annotations that are annotated
 * themselves by {@link GroovyASTTransformation}. Each such annotation is added.
 * <p>
 * This visitor is only intended to be executed once, during the
 * {@link CompilePhase#SEMANTIC_ANALYSIS} phase of compilation.
 */
public class ASTTransformationCollectorCodeVisitor extends ClassCodeVisitorSupport {

    private ClassNode classNode;
    private final SourceUnit source;
    private final GroovyClassLoader transformLoader;

    public ASTTransformationCollectorCodeVisitor(final SourceUnit source, final GroovyClassLoader transformLoader) {
        this.source = source;
        this.transformLoader = transformLoader;
    }

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

    @Override
    public void visitClass(final ClassNode classNode) {
        ClassNode oldClass = this.classNode;
        this.classNode = classNode;
        super.visitClass(classNode);
        this.classNode = oldClass;
    }

    @Override
    public void visitAnnotations(final AnnotatedNode node) {
        List<AnnotationNode> nodeAnnotations = node.getAnnotations();
        if (nodeAnnotations.isEmpty()) return;
        super.visitAnnotations(node);

        for (;;) {
            Map<Integer, AnnotationCollectorMode> modes = new LinkedHashMap<>();
            Map<Integer, List<AnnotationNode>> existing = new LinkedHashMap<>();
            Map<Integer, List<AnnotationNode>> replacements = new LinkedHashMap<>();
            int index = 0;
            for (AnnotationNode annotation : nodeAnnotations) {
                findCollectedAnnotations(annotation, node, index, modes, existing, replacements);
                index += 1;
            }
            for (Map.Entry<Integer, List<AnnotationNode>> entry : replacements.entrySet()) {
                Integer replacementIndex = entry.getKey();
                List<AnnotationNode> annotationNodeList = entry.getValue();
                mergeCollectedAnnotations(modes.get(replacementIndex), existing, annotationNodeList);
                existing.put(replacementIndex, annotationNodeList);
            }
            List<AnnotationNode> mergedList = new ArrayList<>();
            existing.values().forEach(mergedList::addAll);
            if (mergedList.equals(nodeAnnotations)) break;

            nodeAnnotations.clear();
            nodeAnnotations.addAll(mergedList);
            // GROOVY-9238: look again for collector annotations
        }

        for (AnnotationNode annotation : nodeAnnotations) {
            addTransformsToClassNode(annotation);
        }
    }

    private static void mergeCollectedAnnotations(final AnnotationCollectorMode mode, final Map<Integer, List<AnnotationNode>> existing, final List<AnnotationNode> replacements) {
        switch (mode) {
            case PREFER_COLLECTOR:
                deleteExisting(false, existing, replacements);
                break;
            case PREFER_COLLECTOR_MERGED:
                deleteExisting(true, existing, replacements);
                break;
            case PREFER_EXPLICIT:
                deleteReplacement(false, existing, replacements);
                break;
            case PREFER_EXPLICIT_MERGED:
                deleteReplacement(true, existing, replacements);
                break;
            default:
                // nothing to do
        }
    }

    private static void deleteExisting(final boolean mergeParams, final Map<Integer, List<AnnotationNode>> existing, final List<AnnotationNode> replacements) {
        for (AnnotationNode replacement : replacements) {
            for (Map.Entry<Integer, List<AnnotationNode>> entry : existing.entrySet()) {
                List<AnnotationNode> annotationNodes = new ArrayList<>(entry.getValue());
                for (Iterator<AnnotationNode> iterator = annotationNodes.iterator(); iterator.hasNext();) {
                    AnnotationNode annotation = iterator.next();
                    if (replacement.getClassNode().getName().equals(annotation.getClassNode().getName())) {
                        if (mergeParams) {
                            mergeParameters(replacement, annotation);
                        }
                        iterator.remove();
                    }
                }
                existing.put(entry.getKey(), annotationNodes);
            }
        }
    }

    private static void deleteReplacement(final boolean mergeParams, final Map<Integer, List<AnnotationNode>> existing, final List<AnnotationNode> replacements) {
        for (Iterator<AnnotationNode> nodeIterator = replacements.iterator(); nodeIterator.hasNext();) {
            boolean remove = false;
            AnnotationNode replacement = nodeIterator.next();
            for (Map.Entry<Integer, List<AnnotationNode>> entry : existing.entrySet()) {
                for (AnnotationNode annotation : entry.getValue()) {
                    if (replacement.getClassNode().getName().equals(annotation.getClassNode().getName())) {
                        if (mergeParams) {
                            mergeParameters(annotation, replacement);
                        }
                        remove = true;
                    }
                }
            }
            if (remove) {
                nodeIterator.remove();
            }
        }
    }

    private static void mergeParameters(final AnnotationNode to, final AnnotationNode from) {
        for (String name : from.getMembers().keySet()) {
            if (to.getMember(name) == null) {
                to.setMember(name, from.getMember(name));
            }
        }
    }

    private void findCollectedAnnotations(final AnnotationNode alias, final AnnotatedNode origin, final Integer index, final Map<Integer, AnnotationCollectorMode> modes, final Map<Integer, List<AnnotationNode>> existing, final Map<Integer, List<AnnotationNode>> replacements) {
        for (AnnotationNode annotation : alias.getClassNode().getAnnotations()) {
            if (annotation.getClassNode().getName().equals(AnnotationCollector.class.getName())) {
                Expression mode = annotation.getMember("mode");
                modes.put(index, Optional.ofNullable(mode)
                    .map(exp -> evaluateExpression(exp, source.getConfiguration()))
                    .map(val -> (AnnotationCollectorMode) val)
                    .orElse(AnnotationCollectorMode.DUPLICATE)
                );

                Expression processor = annotation.getMember("processor");
                AnnotationCollectorTransform act = null;
                if (processor != null) {
                    String className = (String) evaluateExpression(processor, source.getConfiguration());
                    Class<?> klass = loadTransformClass(className, alias);
                    if (klass != null) {
                        try {
                            act = (AnnotationCollectorTransform) klass.getDeclaredConstructor().newInstance();
                        } catch (ReflectiveOperationException | RuntimeException e) {
                            source.getErrorCollector().addErrorAndContinue(new ExceptionMessage(e, true, source));
                        }
                    }
                } else {
                    act = new AnnotationCollectorTransform();
                }
                if (act != null) {
                    List<AnnotationNode> result = act.visit(annotation, alias, origin, source);
                    replacements.put(index, result);
                    return;
                }
            }
        }
        if (!replacements.containsKey(index)) {
            existing.put(index, Collections.singletonList(alias));
        }
    }

    private Class<?> loadTransformClass(final String transformClass, final AnnotationNode annotation) {
        try {
            return transformLoader.loadClass(transformClass, false, true, false);
        } catch (ReflectiveOperationException | LinkageError e) {
            String error = "Could not find class for Transformation Processor " + transformClass + " declared by " + annotation.getClassNode().getName();
            source.getErrorCollector().addErrorAndContinue(new SimpleMessage(error, source));
        }
        return null;
    }

    //--------------------------------------------------------------------------

    /**
     * Determines if given annotation specifies an AST transformation and if so,
     * adds it to the current class.
     */
    private void addTransformsToClassNode(final AnnotationNode annotation) {
        Annotation transformClassAnnotation = getTransformClassAnnotation(annotation.getClassNode());
        if (transformClassAnnotation != null) {
            try {
                Method valueMethod = transformClassAnnotation.getClass().getMethod("value");
                String[] transformClassNames = (String[]) valueMethod.invoke(transformClassAnnotation);
                if (transformClassNames == null) transformClassNames = new String[0];

                Method classesMethod = transformClassAnnotation.getClass().getMethod("classes");
                Class<?>[] transformClasses = (Class[]) classesMethod.invoke(transformClassAnnotation);
                if (transformClasses == null) transformClasses = new Class[0];

                if (transformClassNames.length == 0 && transformClasses.length == 0) {
                    String error = "@GroovyASTTransformationClass in " + annotation.getClassNode().getName() + " does not specify any transform class names or types";
                    source.getErrorCollector().addError(new SimpleMessage(error, source));
                }

                if (transformClassNames.length > 0 && transformClasses.length > 0) {
                    String error = "@GroovyASTTransformationClass in " + annotation.getClassNode().getName() + " should specify transforms by name or by type, not by both";
                    source.getErrorCollector().addError(new SimpleMessage(error, source));
                }

                Stream.concat(Stream.of(transformClassNames), Stream.of(transformClasses).map(Class::getName)).map(transformClassName -> loadTransformClass(transformClassName, annotation)).filter(Objects::nonNull).forEach(transformClass -> verifyAndAddTransform(annotation, transformClass));
            } catch (ReflectiveOperationException | RuntimeException e) {
                source.getErrorCollector().addError(new ExceptionMessage(e, true, source));
            }
        }
    }

    private static Annotation getTransformClassAnnotation(final ClassNode annotationType) {
        if (!annotationType.isResolved()) return null;

        for (Annotation a : annotationType.getTypeClass().getAnnotations()) {
            // clients are free to choose any GroovyClassLoader for resolving a
            // ClassNode such as annotationType; we have to compare by name and
            // cannot cast the return value to our GroovyASTTransformationClass
            if (a.annotationType().getName().equals(GroovyASTTransformationClass.class.getName())) {
                return a;
            }
        }

        return null;
    }

    @SuppressWarnings("unchecked")
    private void verifyAndAddTransform(final AnnotationNode annotation, final Class<?> transformClass) {
        if (!ASTTransformation.class.isAssignableFrom(transformClass)) {
            String error = "Not an ASTTransformation: " + transformClass.getName() + " declared by " + annotation.getClassNode().getName();
            source.getErrorCollector().addError(new SimpleMessage(error, source));
        }

        GroovyASTTransformation transformationClass = transformClass.getAnnotation(GroovyASTTransformation.class);
        if (transformationClass == null) {
            String error = "AST transformation implementation classes must be annotated with " + GroovyASTTransformation.class.getName() + ". " + transformClass.getName() + " lacks this annotation.";
            source.getErrorCollector().addError(new SimpleMessage(error, source));
        }

        CompilePhase specifiedCompilePhase = transformationClass.phase();
        if (specifiedCompilePhase.getPhaseNumber() < CompilePhase.SEMANTIC_ANALYSIS.getPhaseNumber()) {
            String error = annotation.getClassNode().getName() + " is defined to be run in compile phase " + specifiedCompilePhase + ". Local AST transformations must run in SEMANTIC_ANALYSIS or later!";
            source.getErrorCollector().addError(new SimpleMessage(error, source));
        }

        if (!Traits.isTrait(classNode) || transformClass == TraitASTTransformation.class || transformClass == SealedASTTransformation.class) {
            classNode.addTransform((Class<? extends ASTTransformation>) transformClass, annotation);
        }
    }
}
