/*
 * Copyright (c) 2011, 2017, 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 com.sun.tools.javac.tree;

import java.text.BreakIterator;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.List;
import java.util.ListIterator;

import javax.lang.model.element.Name;
import javax.tools.Diagnostic;
import javax.tools.JavaFileObject;

import com.sun.source.doctree.AttributeTree.ValueKind;
import com.sun.source.doctree.DocCommentTree;
import com.sun.source.doctree.DocTree;
import com.sun.source.doctree.DocTree.Kind;
import com.sun.source.doctree.EndElementTree;
import com.sun.source.doctree.IdentifierTree;
import com.sun.source.doctree.ReferenceTree;
import com.sun.source.doctree.StartElementTree;
import com.sun.source.doctree.TextTree;
import com.sun.source.doctree.ProvidesTree;
import com.sun.source.doctree.UsesTree;
import com.sun.source.util.DocTreeFactory;
import com.sun.tools.doclint.HtmlTag;
import com.sun.tools.javac.api.JavacTrees;
import com.sun.tools.javac.parser.ParserFactory;
import com.sun.tools.javac.parser.ReferenceParser;
import com.sun.tools.javac.parser.Tokens.Comment;
import com.sun.tools.javac.parser.Tokens.Comment.CommentStyle;
import com.sun.tools.javac.tree.DCTree.DCAttribute;
import com.sun.tools.javac.tree.DCTree.DCAuthor;
import com.sun.tools.javac.tree.DCTree.DCComment;
import com.sun.tools.javac.tree.DCTree.DCDeprecated;
import com.sun.tools.javac.tree.DCTree.DCDocComment;
import com.sun.tools.javac.tree.DCTree.DCDocRoot;
import com.sun.tools.javac.tree.DCTree.DCDocType;
import com.sun.tools.javac.tree.DCTree.DCEndElement;
import com.sun.tools.javac.tree.DCTree.DCEntity;
import com.sun.tools.javac.tree.DCTree.DCErroneous;
import com.sun.tools.javac.tree.DCTree.DCHidden;
import com.sun.tools.javac.tree.DCTree.DCIdentifier;
import com.sun.tools.javac.tree.DCTree.DCIndex;
import com.sun.tools.javac.tree.DCTree.DCInheritDoc;
import com.sun.tools.javac.tree.DCTree.DCLink;
import com.sun.tools.javac.tree.DCTree.DCLiteral;
import com.sun.tools.javac.tree.DCTree.DCParam;
import com.sun.tools.javac.tree.DCTree.DCProvides;
import com.sun.tools.javac.tree.DCTree.DCReference;
import com.sun.tools.javac.tree.DCTree.DCReturn;
import com.sun.tools.javac.tree.DCTree.DCSee;
import com.sun.tools.javac.tree.DCTree.DCSerial;
import com.sun.tools.javac.tree.DCTree.DCSerialData;
import com.sun.tools.javac.tree.DCTree.DCSerialField;
import com.sun.tools.javac.tree.DCTree.DCSince;
import com.sun.tools.javac.tree.DCTree.DCStartElement;
import com.sun.tools.javac.tree.DCTree.DCSummary;
import com.sun.tools.javac.tree.DCTree.DCText;
import com.sun.tools.javac.tree.DCTree.DCThrows;
import com.sun.tools.javac.tree.DCTree.DCUnknownBlockTag;
import com.sun.tools.javac.tree.DCTree.DCUnknownInlineTag;
import com.sun.tools.javac.tree.DCTree.DCUses;
import com.sun.tools.javac.tree.DCTree.DCValue;
import com.sun.tools.javac.tree.DCTree.DCVersion;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.DefinedBy;
import com.sun.tools.javac.util.DefinedBy.Api;
import com.sun.tools.javac.util.DiagnosticSource;
import com.sun.tools.javac.util.JCDiagnostic;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
import com.sun.tools.javac.util.ListBuffer;
import com.sun.tools.javac.util.Pair;
import com.sun.tools.javac.util.Position;

import static com.sun.tools.doclint.HtmlTag.*;

 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/**
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class DocTreeMaker implements DocTreeFactory {

    
The context key for the tree factory. /** The context key for the tree factory. */
    protected static final Context.Key<DocTreeMaker> treeMakerKey = new Context.Key<>();

    // A subset of block tags, which acts as sentence breakers, appearing
    // anywhere but the zero'th position in the first sentence.
    final EnumSet<HtmlTag> sentenceBreakTags;

    
Get the TreeMaker instance. /** Get the TreeMaker instance. */
    public static DocTreeMaker instance(Context context) {
        DocTreeMaker instance = context.get(treeMakerKey);
        if (instance == null)
            instance = new DocTreeMaker(context);
        return instance;
    }

    
The position at which subsequent trees will be created.
/** The position at which subsequent trees will be created.
     */
    public int pos = Position.NOPOS;

    
Access to diag factory for ErroneousTrees. /** Access to diag factory for ErroneousTrees. */
    private final JCDiagnostic.Factory diags;

    private final JavacTrees trees;

    
Utility class to parse reference signatures. /** Utility class to parse reference signatures. */
    private final ReferenceParser referenceParser;

    
Create a tree maker with NOPOS as initial position.
/** Create a tree maker with NOPOS as initial position.
     */
    protected DocTreeMaker(Context context) {
        context.put(treeMakerKey, this);
        diags = JCDiagnostic.Factory.instance(context);
        this.pos = Position.NOPOS;
        trees = JavacTrees.instance(context);
        referenceParser = new ReferenceParser(ParserFactory.instance(context));
        sentenceBreakTags = EnumSet.of(H1, H2, H3, H4, H5, H6, PRE, P);
    }

    
Reassign current position.
/** Reassign current position.
     */
    @Override @DefinedBy(Api.COMPILER_TREE)
    public DocTreeMaker at(int pos) {
        this.pos = pos;
        return this;
    }

    
Reassign current position.
/** Reassign current position.
     */
    public DocTreeMaker at(DiagnosticPosition pos) {
        this.pos = (pos == null ? Position.NOPOS : pos.getStartPosition());
        return this;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCAttribute newAttributeTree(javax.lang.model.element.Name name, ValueKind vkind, java.util.List<? extends DocTree> value) {
        DCAttribute tree = new DCAttribute(name, vkind, cast(value));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCAuthor newAuthorTree(java.util.List<? extends DocTree> name) {
        DCAuthor tree = new DCAuthor(cast(name));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCLiteral newCodeTree(TextTree text) {
        DCLiteral tree = new DCLiteral(Kind.CODE, (DCText) text);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCComment newCommentTree(String text) {
        DCComment tree = new DCComment(text);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCDeprecated newDeprecatedTree(List<? extends DocTree> text) {
        DCDeprecated tree = new DCDeprecated(cast(text));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCDocComment newDocCommentTree(List<? extends DocTree> fullBody, List<? extends DocTree> tags) {
        Pair<List<DCTree>, List<DCTree>> pair = splitBody(fullBody);
        List<DCTree> preamble = Collections.emptyList();
        List<DCTree> postamble = Collections.emptyList();

        return newDocCommentTree(fullBody, tags, preamble, postamble);
    }

    public DCDocComment newDocCommentTree(Comment comment,
                                          List<? extends DocTree> fullBody,
                                          List<? extends DocTree> tags,
                                          List<? extends DocTree> preamble,
                                          List<? extends DocTree> postamble) {
        Pair<List<DCTree>, List<DCTree>> pair = splitBody(fullBody);
        DCDocComment tree = new DCDocComment(comment, cast(fullBody), pair.fst, pair.snd,
                cast(tags), cast(preamble), cast(postamble));
        tree.pos = pos;
        return tree;
    }

    /*
     * Primarily to produce a DocCommenTree when given a
     * first sentence and a body, this is useful, in cases
     * where the trees are being synthesized by a tool.
     */
    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCDocComment newDocCommentTree(List<? extends DocTree> fullBody,
                                          List<? extends DocTree> tags,
                                          List<? extends DocTree> preamble,
                                          List<? extends DocTree> postamble) {
        ListBuffer<DCTree> lb = new ListBuffer<>();
        lb.addAll(cast(fullBody));
        List<DCTree> fBody = lb.toList();

        // A dummy comment to keep the diagnostics logic happy.
        Comment c = new Comment() {
            @Override
            public String getText() {
                return null;
            }

            @Override
            public int getSourcePos(int index) {
                return Position.NOPOS;
            }

            @Override
            public CommentStyle getStyle() {
                return CommentStyle.JAVADOC;
            }

            @Override
            public boolean isDeprecated() {
                return false;
            }
        };
        Pair<List<DCTree>, List<DCTree>> pair = splitBody(fullBody);
        DCDocComment tree = new DCDocComment(c, fBody, pair.fst, pair.snd, cast(tags),
                                             cast(preamble), cast(postamble));
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCDocRoot newDocRootTree() {
        DCDocRoot tree = new DCDocRoot();
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCDocType newDocTypeTree(String text) {
        DCDocType tree = new DCDocType(text);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCEndElement newEndElementTree(Name name) {
        DCEndElement tree = new DCEndElement(name);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCEntity newEntityTree(Name name) {
        DCEntity tree = new DCEntity(name);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCErroneous newErroneousTree(String text, Diagnostic<JavaFileObject> diag) {
        DCErroneous tree = new DCErroneous(text, (JCDiagnostic) diag);
        tree.pos = pos;
        return tree;
    }

    public DCErroneous newErroneousTree(String text, DiagnosticSource diagSource, String code, Object... args) {
        DCErroneous tree = new DCErroneous(text, diags, diagSource, code, args);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCThrows newExceptionTree(ReferenceTree name, List<? extends DocTree> description) {
        // TODO: verify the reference is just to a type (not a field or method)
        DCThrows tree = new DCThrows(Kind.EXCEPTION, (DCReference) name, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCHidden newHiddenTree(List<? extends DocTree> text) {
        DCHidden tree = new DCHidden(cast(text));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCIdentifier newIdentifierTree(Name name) {
        DCIdentifier tree = new DCIdentifier(name);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCIndex newIndexTree(DocTree term, List<? extends DocTree> description) {
        DCIndex tree = new DCIndex((DCTree) term, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCInheritDoc newInheritDocTree() {
        DCInheritDoc tree = new DCInheritDoc();
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCLink newLinkTree(ReferenceTree ref, List<? extends DocTree> label) {
        DCLink tree = new DCLink(Kind.LINK, (DCReference) ref, cast(label));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCLink newLinkPlainTree(ReferenceTree ref, List<? extends DocTree> label) {
        DCLink tree = new DCLink(Kind.LINK_PLAIN, (DCReference) ref, cast(label));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCLiteral newLiteralTree(TextTree text) {
        DCLiteral tree = new DCLiteral(Kind.LITERAL, (DCText) text);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCParam newParamTree(boolean isTypeParameter, IdentifierTree name, List<? extends DocTree> description) {
        DCParam tree = new DCParam(isTypeParameter, (DCIdentifier) name, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCProvides newProvidesTree(ReferenceTree name, List<? extends DocTree> description) {
        DCProvides tree = new DCProvides((DCReference) name, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCReference newReferenceTree(String signature) {
        try {
            ReferenceParser.Reference ref = referenceParser.parse(signature);
            DCReference tree = new DCReference(signature, ref.qualExpr, ref.member, ref.paramTypes);
            tree.pos = pos;
            return tree;
        } catch (ReferenceParser.ParseException e) {
            throw new IllegalArgumentException("invalid signature", e);
        }
    }

    public DCReference newReferenceTree(String signature, JCTree qualExpr, Name member, List<JCTree> paramTypes) {
        DCReference tree = new DCReference(signature, qualExpr, member, paramTypes);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCReturn newReturnTree(List<? extends DocTree> description) {
        DCReturn tree = new DCReturn(cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSee newSeeTree(List<? extends DocTree> reference) {
        DCSee tree = new DCSee(cast(reference));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSerial newSerialTree(List<? extends DocTree> description) {
        DCSerial tree = new DCSerial(cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSerialData newSerialDataTree(List<? extends DocTree> description) {
        DCSerialData tree = new DCSerialData(cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSerialField newSerialFieldTree(IdentifierTree name, ReferenceTree type, List<? extends DocTree> description) {
        DCSerialField tree = new DCSerialField((DCIdentifier) name, (DCReference) type, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSince newSinceTree(List<? extends DocTree> text) {
        DCSince tree = new DCSince(cast(text));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCStartElement newStartElementTree(Name name, List<? extends DocTree> attrs, boolean selfClosing) {
        DCStartElement tree = new DCStartElement(name, cast(attrs), selfClosing);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCSummary newSummaryTree(List<? extends DocTree> text) {
        DCSummary tree = new DCSummary(cast(text));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCText newTextTree(String text) {
        DCText tree = new DCText(text);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCThrows newThrowsTree(ReferenceTree name, List<? extends DocTree> description) {
        // TODO: verify the reference is just to a type (not a field or method)
        DCThrows tree = new DCThrows(Kind.THROWS, (DCReference) name, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCUnknownBlockTag newUnknownBlockTagTree(Name name, List<? extends DocTree> content) {
        DCUnknownBlockTag tree = new DCUnknownBlockTag(name, cast(content));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCUnknownInlineTag newUnknownInlineTagTree(Name name, List<? extends DocTree> content) {
        DCUnknownInlineTag tree = new DCUnknownInlineTag(name, cast(content));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCUses newUsesTree(ReferenceTree name, List<? extends DocTree> description) {
        DCUses tree = new DCUses((DCReference) name, cast(description));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCValue newValueTree(ReferenceTree ref) {
        // TODO: verify the reference is to a constant value
        DCValue tree = new DCValue((DCReference) ref);
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public DCVersion newVersionTree(List<? extends DocTree> text) {
        DCVersion tree = new DCVersion(cast(text));
        tree.pos = pos;
        return tree;
    }

    @Override @DefinedBy(Api.COMPILER_TREE)
    public java.util.List<DocTree> getFirstSentence(java.util.List<? extends DocTree> list) {
        Pair<List<DCTree>, List<DCTree>> pair = splitBody(list);
        return new ArrayList<>(pair.fst);
    }

    /*
     * Breaks up the body tags into the first sentence and its successors.
     * The first sentence is determined with the presence of a period,
     * block tag, or a sentence break, as returned by the BreakIterator.
     * Trailing whitespaces are trimmed.
     */
    private Pair<List<DCTree>, List<DCTree>> splitBody(Collection<? extends DocTree> list) {
        // pos is modified as we create trees, therefore
        // we save the pos and restore it later.
        final int savedpos = this.pos;
        try {
            ListBuffer<DCTree> body = new ListBuffer<>();
            // split body into first sentence and body
            ListBuffer<DCTree> fs = new ListBuffer<>();
            if (list.isEmpty()) {
                return new Pair<>(fs.toList(), body.toList());
            }
            boolean foundFirstSentence = false;
            ArrayList<DocTree> alist = new ArrayList<>(list);
            ListIterator<DocTree> itr = alist.listIterator();
            while (itr.hasNext()) {
                boolean isFirst = !itr.hasPrevious();
                DocTree dt = itr.next();
                int spos = ((DCTree) dt).pos;
                if (foundFirstSentence) {
                    body.add((DCTree) dt);
                    continue;
                }
                switch (dt.getKind()) {
                    case SUMMARY:
                        foundFirstSentence = true;
                        break;
                    case TEXT:
                        DCText tt = (DCText) dt;
                        String s = tt.getBody();
                        DocTree peekedNext = itr.hasNext()
                                ? alist.get(itr.nextIndex())
                                : null;
                        int sbreak = getSentenceBreak(s, peekedNext);
                        if (sbreak > 0) {
                            s = removeTrailingWhitespace(s.substring(0, sbreak));
                            DCText text = this.at(spos).newTextTree(s);
                            fs.add(text);
                            foundFirstSentence = true;
                            int nwPos = skipWhiteSpace(tt.getBody(), sbreak);
                            if (nwPos > 0) {
                                DCText text2 = this.at(spos + nwPos).newTextTree(tt.getBody().substring(nwPos));
                                body.add(text2);
                            }
                            continue;
                        } else if (itr.hasNext()) {
                            // if the next doctree is a break, remove trailing spaces
                            peekedNext = alist.get(itr.nextIndex());
                            boolean sbrk = isSentenceBreak(peekedNext, false);
                            if (sbrk) {
                                DocTree next = itr.next();
                                s = removeTrailingWhitespace(s);
                                DCText text = this.at(spos).newTextTree(s);
                                fs.add(text);
                                body.add((DCTree) next);
                                foundFirstSentence = true;
                                continue;
                            }
                        }
                        break;
                    default:
                        if (isSentenceBreak(dt, isFirst)) {
                            body.add((DCTree) dt);
                            foundFirstSentence = true;
                            continue;
                        }
                        break;
                }
                fs.add((DCTree) dt);
            }
            return new Pair<>(fs.toList(), body.toList());
        } finally {
            this.pos = savedpos;
        }
    }

    private boolean isTextTree(DocTree tree) {
        return tree.getKind() == Kind.TEXT;
    }

    /*
     * Computes the first sentence break, a simple dot-space algorithm.
     */
    private int defaultSentenceBreak(String s) {
        // scan for period followed by whitespace
        int period = -1;
        for (int i = 0; i < s.length(); i++) {
            switch (s.charAt(i)) {
                case '.':
                    period = i;
                    break;

                case ' ':
                case '\f':
                case '\n':
                case '\r':
                case '\t':
                    if (period >= 0) {
                        return i;
                    }
                    break;

                default:
                    period = -1;
                    break;
            }
        }
        return -1;
    }

    /*
     * Computes the first sentence, if using a default breaker,
     * the break is returned, if not then a -1, indicating that
     * more doctree elements are required to be examined.
     *
     * BreakIterator.next points to the the start of the following sentence,
     * and does not provide an easy way to disambiguate between "sentence break",
     * "possible sentence break" and "not a sentence break" at the end of the input.
     * For example, BreakIterator.next returns the index for the end
     * of the string for all of these examples,
     * using vertical bars to delimit the bounds of the example text
     * |Abc|        (not a valid end of sentence break, if followed by more text)
     * |Abc.|       (maybe a valid end of sentence break, depending on the following text)
     * |Abc. |      (maybe a valid end of sentence break, depending on the following text)
     * |"Abc." |    (maybe a valid end of sentence break, depending on the following text)
     * |Abc.  |     (definitely a valid end of sentence break)
     * |"Abc."  |   (definitely a valid end of sentence break)
     * Therefore, we have to probe further to determine whether
     * there really is a sentence break or not at the end of this run of text.
     */
    private int getSentenceBreak(String s, DocTree dt) {
        BreakIterator breakIterator = trees.getBreakIterator();
        if (breakIterator == null) {
            return defaultSentenceBreak(s);
        }
        breakIterator.setText(s);
        final int sbrk = breakIterator.next();
        // This is the last doctree, found the droid we are looking for
        if (dt == null) {
            return sbrk;
        }

        // If the break is well within the span of the string ie. not
        // at EOL, then we have a clear break.
        if (sbrk < s.length() - 1) {
            return sbrk;
        }

        if (isTextTree(dt)) {
            // Two adjacent text trees, a corner case, perhaps
            // produced by a tool synthesizing a doctree. In
            // this case, does the break lie within the first span,
            // then we have the droid, otherwise allow the callers
            // logic to handle the break in the adjacent doctree.
            TextTree ttnext = (TextTree) dt;
            String combined = s + ttnext.getBody();
            breakIterator.setText(combined);
            int sbrk2 = breakIterator.next();
            if (sbrk < sbrk2) {
                return sbrk;
            }
        }

        // Is the adjacent tree a sentence breaker ?
        if (isSentenceBreak(dt, false)) {
            return sbrk;
        }

        // At this point the adjacent tree is either a javadoc tag ({@..),
        // html tag (<..) or an entity (&..). Perform a litmus test, by
        // concatenating a sentence, to validate the break earlier identified.
        String combined = s + "Dummy Sentence.";
        breakIterator.setText(combined);
        int sbrk2 = breakIterator.next();
        if (sbrk2 <= sbrk) {
            return sbrk2;
        }
        return -1; // indeterminate at this time
    }

    private boolean isSentenceBreak(javax.lang.model.element.Name tagName) {
        return sentenceBreakTags.contains(get(tagName));
    }

    private boolean isSentenceBreak(DocTree dt, boolean isFirstDocTree) {
        switch (dt.getKind()) {
            case START_ELEMENT:
                    StartElementTree set = (StartElementTree)dt;
                    return !isFirstDocTree && ((DCTree) dt).pos > 1 && isSentenceBreak(set.getName());
            case END_ELEMENT:
                    EndElementTree eet = (EndElementTree)dt;
                    return !isFirstDocTree && ((DCTree) dt).pos > 1 && isSentenceBreak(eet.getName());
            default:
                return false;
        }
    }

    /*
     * Returns the position of the the first non-white space
     */
    private int skipWhiteSpace(String s, int start) {
        for (int i = start; i < s.length(); i++) {
            char c = s.charAt(i);
            if (!Character.isWhitespace(c)) {
                return i;
            }
        }
        return -1;
    }

    private String removeTrailingWhitespace(String s) {
        for (int i = s.length() - 1 ; i >= 0 ; i--) {
            char ch = s.charAt(i);
            if (!Character.isWhitespace(ch)) {
                return s.substring(0, i + 1);
            }
        }
        return s;
    }

    @SuppressWarnings("unchecked")
    private List<DCTree> cast(List<? extends DocTree> list) {
        return (List<DCTree>) list;
    }
}