/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.internal.shellsupport.doc;

import java.io.IOException;

import java.net.URI;

import java.net.URISyntaxException;

import java.nio.file.Path;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Comparator;

import java.util.HashMap;

import java.util.HashSet;

import java.util.IdentityHashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Objects;

import java.util.Set;

import java.util.Stack;

import java.util.TreeMap;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import javax.lang.model.element.Element;

import javax.lang.model.element.ElementKind;

import javax.lang.model.element.ExecutableElement;

import javax.lang.model.element.TypeElement;

import javax.lang.model.element.VariableElement;

import javax.lang.model.type.DeclaredType;

import javax.lang.model.type.TypeKind;

import javax.lang.model.util.ElementFilter;

import javax.tools.JavaCompiler;

import javax.tools.JavaFileManager;

import javax.tools.JavaFileObject;

import javax.tools.SimpleJavaFileObject;

import javax.tools.StandardJavaFileManager;

import javax.tools.StandardLocation;

import javax.tools.ToolProvider;

import com.sun.source.doctree.DocCommentTree;

import com.sun.source.doctree.DocTree;

import com.sun.source.doctree.InheritDocTree;

import com.sun.source.doctree.ParamTree;

import com.sun.source.doctree.ReturnTree;

import com.sun.source.doctree.ThrowsTree;

import com.sun.source.tree.ClassTree;

import com.sun.source.tree.CompilationUnitTree;

import com.sun.source.tree.MethodTree;

import com.sun.source.tree.VariableTree;

import com.sun.source.util.DocTreePath;

import com.sun.source.util.DocTreeScanner;

import com.sun.source.util.DocTrees;

import com.sun.source.util.JavacTask;

import com.sun.source.util.TreePath;

import com.sun.source.util.TreePathScanner;

import com.sun.source.util.Trees;

import com.sun.tools.javac.api.JavacTaskImpl;

import com.sun.tools.javac.util.DefinedBy;

import com.sun.tools.javac.util.DefinedBy.Api;

import com.sun.tools.javac.util.Pair;

/**Helper to find javadoc and resolve @inheritDoc.

 */

public abstract class JavadocHelper implements AutoCloseable {

    private static final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

    /**Create the helper.

     *

     * @param mainTask JavacTask from which the further Elements originate

     * @param sourceLocations paths where source files should be searched

     * @return a JavadocHelper

     */

    public static JavadocHelper create(JavacTask mainTask, Collection<? extends Path> sourceLocations) {

        StandardJavaFileManager fm = compiler.getStandardFileManager(null, null, null);

        try {

            fm.setLocationFromPaths(StandardLocation.SOURCE_PATH, sourceLocations);

            return new OnDemandJavadocHelper(mainTask, fm);

        } catch (IOException ex) {

            try {

                fm.close();

            } catch (IOException closeEx) {

            }

            return new JavadocHelper() {

                @Override

                public String getResolvedDocComment(Element forElement) throws IOException {

                    return null;

                }

                @Override

                public Element getSourceElement(Element forElement) throws IOException {

                    return forElement;

                }

                @Override

                public void close() throws IOException {}

            };

        }

    }

    /**Returns javadoc for the given element, if it can be found, or null otherwise. The javadoc

     * will have @inheritDoc resolved.

     *

     * @param forElement element for which the javadoc should be searched

     * @return javadoc if found, null otherwise

     * @throws IOException if something goes wrong in the search

     */

    public abstract String getResolvedDocComment(Element forElement) throws IOException;

    /**Returns an element representing the same given program element, but the returned element will

     * be resolved from source, if it can be found. Returns the original element if the source for

     * the given element cannot be found.

     *

     * @param forElement element for which the source element should be searched

     * @return source element if found, the original element otherwise

     * @throws IOException if something goes wrong in the search

     */

    public abstract Element getSourceElement(Element forElement) throws IOException;

    /**Closes the helper.

     *

     * @throws IOException if something foes wrong during the close

     */

    @Override

    public abstract void close() throws IOException;

    private static final class OnDemandJavadocHelper extends JavadocHelper {

        private final JavacTask mainTask;

        private final JavaFileManager baseFileManager;

        private final StandardJavaFileManager fm;

        private final Map<String, Pair<JavacTask, TreePath>> signature2Source = new HashMap<>();

        private OnDemandJavadocHelper(JavacTask mainTask, StandardJavaFileManager fm) {

            this.mainTask = mainTask;

            this.baseFileManager = ((JavacTaskImpl) mainTask).getContext().get(JavaFileManager.class);

            this.fm = fm;

        }

        @Override

        public String getResolvedDocComment(Element forElement) throws IOException {

            Pair<JavacTask, TreePath> sourceElement = getSourceElement(mainTask, forElement);

            if (sourceElement == null)

                return null;

            return getResolvedDocComment(sourceElement.fst, sourceElement.snd);

        }

        @Override

        public Element getSourceElement(Element forElement) throws IOException {

            Pair<JavacTask, TreePath> sourceElement = getSourceElement(mainTask, forElement);

            if (sourceElement == null)

                return forElement;

            Element result = Trees.instance(sourceElement.fst).getElement(sourceElement.snd);

            if (result == null)

                return forElement;

            return result;

        }

        private String getResolvedDocComment(JavacTask task, TreePath el) throws IOException {

            DocTrees trees = DocTrees.instance(task);

            Element element = trees.getElement(el);

            String docComment = trees.getDocComment(el);

            if (docComment == null && element.getKind() == ElementKind.METHOD) {

                ExecutableElement executableElement = (ExecutableElement) element;

                Iterable<Element> superTypes =

                        () -> superTypeForInheritDoc(task, element.getEnclosingElement()).iterator();

                for (Element sup : superTypes) {

                   for (ExecutableElement supMethod : ElementFilter.methodsIn(sup.getEnclosedElements())) {

                       TypeElement clazz = (TypeElement) executableElement.getEnclosingElement();

                       if (task.getElements().overrides(executableElement, supMethod, clazz)) {

                           Pair<JavacTask, TreePath> source = getSourceElement(task, supMethod);

                           if (source != null) {

                               String overriddenComment = getResolvedDocComment(source.fst, source.snd);

                               if (overriddenComment != null) {

                                   return overriddenComment;

                               }

                           }

                       }

                   }

                }

            }

            DocCommentTree docCommentTree = parseDocComment(task, docComment);

            IOException[] exception = new IOException[1];

            Map<int[], String> replace = new TreeMap<>((span1, span2) -> span2[0] - span1[0]);

            new DocTreeScanner<Void, Void>() {

                private Stack<DocTree> interestingParent = new Stack<>();

                private DocCommentTree dcTree;

                private JavacTask inheritedJavacTask;

                private TreePath inheritedTreePath;

                private String inherited;

                private Map<DocTree, String> syntheticTrees = new IdentityHashMap<>();

                private long lastPos = 0;

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void visitDocComment(DocCommentTree node, Void p) {

                    dcTree = node;

                    interestingParent.push(node);

                    try {

                        scan(node.getFirstSentence(), p);

                        scan(node.getBody(), p);

                        List<DocTree> augmentedBlockTags = new ArrayList<>(node.getBlockTags());

                        if (element.getKind() == ElementKind.METHOD) {

                            ExecutableElement executableElement = (ExecutableElement) element;

                            List<String> parameters =

                                    executableElement.getParameters()

                                                     .stream()

                                                     .map(param -> param.getSimpleName().toString())

                                                     .collect(Collectors.toList());

                            List<String> throwsList =

                                    executableElement.getThrownTypes()

                                                     .stream()

                                                     .collect(Collectors.toList());

                            Set<String> missingParams = new HashSet<>(parameters);

                            Set<String> missingThrows = new HashSet<>(throwsList);

                            boolean hasReturn = false;

                            for (DocTree dt : augmentedBlockTags) {

                                switch (dt.getKind()) {

                                    case PARAM:

                                        missingParams.remove(((ParamTree) dt).getName().getName().toString());

                                        break;

                                    case THROWS:

                                        missingThrows.remove(getThrownException(task, el, docCommentTree, (ThrowsTree) dt));

                                        break;

                                    case RETURN:

                                        hasReturn = true;

                                        break;

                                }

                            }

                            for (String missingParam : missingParams) {

                                DocTree syntheticTag = parseBlockTag(task, "@param " + missingParam + " {@inheritDoc}");

                                syntheticTrees.put(syntheticTag, "@param " + missingParam + " ");

                                insertTag(augmentedBlockTags, syntheticTag, parameters, throwsList);

                            }

                            for (String missingThrow : missingThrows) {

                                DocTree syntheticTag = parseBlockTag(task, "@throws " + missingThrow + " {@inheritDoc}");

                                syntheticTrees.put(syntheticTag, "@throws " + missingThrow + " ");

                                insertTag(augmentedBlockTags, syntheticTag, parameters, throwsList);

                            }

                            if (!hasReturn) {

                                DocTree syntheticTag = parseBlockTag(task, "@return {@inheritDoc}");

                                syntheticTrees.put(syntheticTag, "@return ");

                                insertTag(augmentedBlockTags, syntheticTag, parameters, throwsList);

                            }

                        }

                        scan(augmentedBlockTags, p);

                        return null;

                    } finally {

                        interestingParent.pop();

                    }

                }

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void visitParam(ParamTree node, Void p) {

                    interestingParent.push(node);

                    try {

                        return super.visitParam(node, p);

                    } finally {

                        interestingParent.pop();

                    }

                }

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void visitThrows(ThrowsTree node, Void p) {

                    interestingParent.push(node);

                    try {

                        return super.visitThrows(node, p);

                    } finally {

                        interestingParent.pop();

                    }

                }

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void visitReturn(ReturnTree node, Void p) {

                    interestingParent.push(node);

                    try {

                        return super.visitReturn(node, p);

                    } finally {

                        interestingParent.pop();

                    }

                }

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void visitInheritDoc(InheritDocTree node, Void p) {

                    if (inherited == null) {

                        try {

                            if (element.getKind() == ElementKind.METHOD) {

                                ExecutableElement executableElement = (ExecutableElement) element;

                                Iterable<Element> superTypes = () -> superTypeForInheritDoc(task, element.getEnclosingElement()).iterator();

                                OUTER: for (Element sup : superTypes) {

                                   for (ExecutableElement supMethod : ElementFilter.methodsIn(sup.getEnclosedElements())) {

                                       if (task.getElements().overrides(executableElement, supMethod, (TypeElement) executableElement.getEnclosingElement())) {

                                           Pair<JavacTask, TreePath> source = getSourceElement(task, supMethod);

                                           if (source != null) {

                                               String overriddenComment = getResolvedDocComment(source.fst, source.snd);

                                               if (overriddenComment != null) {

                                                   inheritedJavacTask = source.fst;

                                                   inheritedTreePath = source.snd;

                                                   inherited = overriddenComment;

                                                   break OUTER;

                                               }

                                           }

                                       }

                                   }

                                }

                            }

                        } catch (IOException ex) {

                            exception[0] = ex;

                            return null;

                        }

                    }

                    if (inherited == null) {

                        return null;

                    }

                    DocCommentTree inheritedDocTree = parseDocComment(inheritedJavacTask, inherited);

                    List<List<? extends DocTree>> inheritedText = new ArrayList<>();

                    DocTree parent = interestingParent.peek();

                    switch (parent.getKind()) {

                        case DOC_COMMENT:

                            inheritedText.add(inheritedDocTree.getFullBody());

                            break;

                        case PARAM:

                            String paramName = ((ParamTree) parent).getName().getName().toString();

                            new DocTreeScanner<Void, Void>() {

                                @Override @DefinedBy(Api.COMPILER_TREE)

                                public Void visitParam(ParamTree node, Void p) {

                                    if (node.getName().getName().contentEquals(paramName)) {

                                        inheritedText.add(node.getDescription());

                                    }

                                    return super.visitParam(node, p);

                                }

                            }.scan(inheritedDocTree, null);

                            break;

                        case THROWS:

                            String thrownName = getThrownException(task, el, docCommentTree, (ThrowsTree) parent);

                            new DocTreeScanner<Void, Void>() {

                                @Override @DefinedBy(Api.COMPILER_TREE)

                                public Void visitThrows(ThrowsTree node, Void p) {

                                    if (Objects.equals(getThrownException(inheritedJavacTask, inheritedTreePath, inheritedDocTree, node), thrownName)) {

                                        inheritedText.add(node.getDescription());

                                    }

                                    return super.visitThrows(node, p);

                                }

                            }.scan(inheritedDocTree, null);

                            break;

                        case RETURN:

                            new DocTreeScanner<Void, Void>() {

                                @Override @DefinedBy(Api.COMPILER_TREE)

                                public Void visitReturn(ReturnTree node, Void p) {

                                    inheritedText.add(node.getDescription());

                                    return super.visitReturn(node, p);

                                }

                            }.scan(inheritedDocTree, null);

                            break;

                    }

                    if (!inheritedText.isEmpty()) {

                        long offset = trees.getSourcePositions().getStartPosition(null, inheritedDocTree, inheritedDocTree);

                        long start = Long.MAX_VALUE;

                        long end = Long.MIN_VALUE;

                        for (DocTree t : inheritedText.get(0)) {

                            start = Math.min(start, trees.getSourcePositions().getStartPosition(null, inheritedDocTree, t) - offset);

                            end   = Math.max(end,   trees.getSourcePositions().getEndPosition(null, inheritedDocTree, t) - offset);

                        }

                        String text = inherited.substring((int) start, (int) end);

                        if (syntheticTrees.containsKey(parent)) {

                            replace.put(new int[] {(int) lastPos + 1, (int) lastPos}, "\n" + syntheticTrees.get(parent) + text);

                        } else {

                            long inheritedStart = trees.getSourcePositions().getStartPosition(null, dcTree, node);

                            long inheritedEnd   = trees.getSourcePositions().getEndPosition(null, dcTree, node);

                            replace.put(new int[] {(int) inheritedStart, (int) inheritedEnd}, text);

                        }

                    }

                    return super.visitInheritDoc(node, p);

                }

                private boolean inSynthetic;

                @Override @DefinedBy(Api.COMPILER_TREE)

                public Void scan(DocTree tree, Void p) {

                    if (exception[0] != null) {

                        return null;

                    }

                    boolean prevInSynthetic = inSynthetic;

                    try {

                        inSynthetic |= syntheticTrees.containsKey(tree);

                        return super.scan(tree, p);

                    } finally {

                        if (!inSynthetic) {

                            lastPos = trees.getSourcePositions().getEndPosition(null, dcTree, tree);

                        }

                        inSynthetic = prevInSynthetic;

                    }

                }

                private void insertTag(List<DocTree> tags, DocTree toInsert, List<String> parameters, List<String> throwsTypes) {

                    Comparator<DocTree> comp = (tag1, tag2) -> {

                        if (tag1.getKind() == tag2.getKind()) {

                            switch (toInsert.getKind()) {

                                case PARAM: {

                                    ParamTree p1 = (ParamTree) tag1;

                                    ParamTree p2 = (ParamTree) tag2;

                                    int i1 = parameters.indexOf(p1.getName().getName().toString());

                                    int i2 = parameters.indexOf(p2.getName().getName().toString());

                                    return i1 - i2;

                                }

                                case THROWS: {

                                    ThrowsTree t1 = (ThrowsTree) tag1;

                                    ThrowsTree t2 = (ThrowsTree) tag2;

                                    int i1 = throwsTypes.indexOf(getThrownException(task, el, docCommentTree, t1));

                                    int i2 = throwsTypes.indexOf(getThrownException(task, el, docCommentTree, t2));

                                    return i1 - i2;

                                }

                            }

                        }

                        int i1 = tagOrder.indexOf(tag1.getKind());

                        int i2 = tagOrder.indexOf(tag2.getKind());

                        return i1 - i2;

                    };

                    for (int i = 0; i < tags.size(); i++) {

                        if (comp.compare(tags.get(i), toInsert) >= 0) {

                            tags.add(i, toInsert);

                            return ;

                        }

                    }

                    tags.add(toInsert);

                }

                private final List<DocTree.Kind> tagOrder = Arrays.asList(DocTree.Kind.PARAM, DocTree.Kind.THROWS, DocTree.Kind.RETURN);

            }.scan(docCommentTree, null);

            if (replace.isEmpty())

                return docComment;

            StringBuilder replacedInheritDoc = new StringBuilder(docComment);

            int offset = (int) trees.getSourcePositions().getStartPosition(null, docCommentTree, docCommentTree);

            for (Entry<int[], String> e : replace.entrySet()) {

                replacedInheritDoc.delete(e.getKey()[0] - offset, e.getKey()[1] - offset + 1);

                replacedInheritDoc.insert(e.getKey()[0] - offset, e.getValue());

            }

            return replacedInheritDoc.toString();

        }

        private Stream<Element> superTypeForInheritDoc(JavacTask task, Element type) {

            TypeElement clazz = (TypeElement) type;

            Stream<Element> result = interfaces(clazz);

            result = Stream.concat(result, interfaces(clazz).flatMap(el -> superTypeForInheritDoc(task, el)));

            if (clazz.getSuperclass().getKind() == TypeKind.DECLARED) {

                Element superClass = ((DeclaredType) clazz.getSuperclass()).asElement();

                result = Stream.concat(result, Stream.of(superClass));

                result = Stream.concat(result, superTypeForInheritDoc(task, superClass));

            }

            return result;

        }

        //where:

            private Stream<Element> interfaces(TypeElement clazz) {

                return clazz.getInterfaces()

                            .stream()

                            .filter(tm -> tm.getKind() == TypeKind.DECLARED)

                            .map(tm -> ((DeclaredType) tm).asElement());

            }

         private DocTree parseBlockTag(JavacTask task, String blockTag) {

            DocCommentTree dc = parseDocComment(task, blockTag);

            return dc.getBlockTags().get(0);

        }

        private DocCommentTree parseDocComment(JavacTask task, String javadoc) {

            DocTrees trees = DocTrees.instance(task);

            try {

                return trees.getDocCommentTree(new SimpleJavaFileObject(new URI("mem://doc.html"), javax.tools.JavaFileObject.Kind.HTML) {

                    @Override @DefinedBy(Api.COMPILER)

                    public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {

                        return "<body>" + javadoc + "</body>";

                    }

                });

            } catch (URISyntaxException ex) {

                return null;

            }

        }

        private String getThrownException(JavacTask task, TreePath rootOn, DocCommentTree comment, ThrowsTree tt) {

            DocTrees trees = DocTrees.instance(task);

            Element exc = trees.getElement(new DocTreePath(new DocTreePath(rootOn, comment), tt.getExceptionName()));