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namespace JavaLanguageService
{
    using System.Collections.Generic;
    using System.ComponentModel.Composition;
    using CustomLanguageService.Text;
    using Microsoft.VisualStudio.Text;
    using Microsoft.VisualStudio.Text.Classification;
    using Microsoft.VisualStudio.Text.Editor;
    using Microsoft.VisualStudio.Text.Tagging;
    using Microsoft.VisualStudio.Utilities;
 
    [Export(typeof(IViewTaggerProvider))]
    [ContentType(Constants.JavaContentType)]
    [TagType(typeof(TextMarkerTag))]
    public sealed class JavaBraceMatchingTaggerProvider : IViewTaggerProvider
    {
        [Import]
        public IClassifierAggregatorService AggregatorService;
 
        public ITagger<T> CreateTagger<T>(ITextView textView, ITextBuffer buffer) where T : ITag
        {
            if (textView == null)
                return null;
 
            var aggregator = AggregatorService.GetClassifier(buffer);
            var pairs = new KeyValuePair<char, char>[]
                {
                    new KeyValuePair<char, char>('(', ')'),
                    new KeyValuePair<char, char>('{', '}'),
                    new KeyValuePair<char, char>('[', ']')
                };
            return new BraceMatchingTagger(textView, buffer, aggregator, pairs) as ITagger<T>;
        }
    }
}

namespace CustomLanguageService.Text
{
    using System;
    using System.Collections.Generic;
    using System.Collections.ObjectModel;
    using System.Diagnostics.Contracts;
    using System.Linq;
    using Microsoft.VisualStudio.Language.StandardClassification;
    using Microsoft.VisualStudio.Text;
    using Microsoft.VisualStudio.Text.Classification;
    using Microsoft.VisualStudio.Text.Editor;
    using Microsoft.VisualStudio.Text.Tagging;
 
    internal sealed class BraceMatchingTagger : ITagger<TextMarkerTag>
    {
        public event EventHandler<SnapshotSpanEventArgs> TagsChanged;
 
        public BraceMatchingTagger(ITextView textView, ITextBuffer sourceBuffer, IClassifier aggregator, IEnumerable<KeyValuePair<char, char>> matchingCharacters)
        {
            Contract.Requires<ArgumentNullException>(textView != null);
            Contract.Requires<ArgumentNullException>(sourceBuffer != null);
            Contract.Requires<ArgumentNullException>(aggregator != null);
            Contract.Requires<ArgumentNullException>(matchingCharacters != null);
 
            this.TextView = textView;
            this.SourceBuffer = sourceBuffer;
            this.Aggregator = aggregator;
            this.MatchingCharacters = matchingCharacters.ToList().AsReadOnly();
 
            this.TextView.Caret.PositionChanged += Caret_PositionChanged;
            this.TextView.LayoutChanged += TextView_LayoutChanged;
        }
 
        public ITextView TextView
        {
            get;
            private set;
        }
 
        public ITextBuffer SourceBuffer
        {
            get;
            private set;
        }
 
        public IClassifier Aggregator
        {
            get;
            private set;
        }
 
        public ReadOnlyCollection<KeyValuePair<char, char>> MatchingCharacters
        {
            get;
            private set;
        }
 
        private SnapshotPoint? CurrentChar
        {
            get;
            set;
        }
 
        private static bool IsInCommentOrLiteral(IClassifier aggregator, SnapshotPoint point, PositionAffinity affinity)
        {
            Contract.Requires(aggregator != null);
 
            // TODO: handle affinity
            SnapshotSpan span = new SnapshotSpan(point, 1);
 
            var classifications = aggregator.GetClassificationSpans(span);
            var relevant = classifications.FirstOrDefault(classificationSpan => classificationSpan.Span.Contains(point));
            if (relevant == null || relevant.ClassificationType == null)
                return false;
 
            return relevant.ClassificationType.IsOfType(PredefinedClassificationTypeNames.Comment)
                || relevant.ClassificationType.IsOfType(PredefinedClassificationTypeNames.Literal);
        }
 
        private bool IsMatchStartCharacter(char c)
        {
            return MatchingCharacters.Any(pair => pair.Key == c);
        }
 
        private bool IsMatchCloseCharacter(char c)
        {
            return MatchingCharacters.Any(pair => pair.Value == c);
        }
 
        private char GetMatchCloseCharacter(char c)
        {
            return MatchingCharacters.First(pair => pair.Key == c).Value;
        }
 
        private char GetMatchOpenCharacter(char c)
        {
            return MatchingCharacters.First(pair => pair.Value == c).Key;
        }
 
        private static bool FindMatchingCloseChar(SnapshotPoint start, IClassifier aggregator, char open, char close, int maxLines, out SnapshotSpan pairSpan)
        {
            pairSpan = new SnapshotSpan(start.Snapshot, 1, 1);
            ITextSnapshotLine line = start.GetContainingLine();
            string lineText = line.GetText();
            int lineNumber = line.LineNumber;
            int offset = start.Position - line.Start.Position + 1;
 
            int stopLineNumber = start.Snapshot.LineCount - 1;
            if (maxLines > 0)
                stopLineNumber = Math.Min(stopLineNumber, lineNumber + maxLines);
 
            int openCount = 0;
            while (true)
            {
                while (offset < line.Length)
                {
                    char currentChar = lineText[offset];
                    // TODO: is this the correct affinity
                    if (currentChar == close && !IsInCommentOrLiteral(aggregator, new SnapshotPoint(start.Snapshot, offset + line.Start.Position), PositionAffinity.Successor))
                    {
                        if (openCount > 0)
                        {
                            openCount--;
                        }
                        else
                        {
                            pairSpan = new SnapshotSpan(start.Snapshot, line.Start + offset, 1);
                            return true;
                        }
                    }
                    // TODO: is this the correct affinity
                    else if (currentChar == open && !IsInCommentOrLiteral(aggregator, new SnapshotPoint(start.Snapshot, offset + line.Start.Position), PositionAffinity.Successor))
                    {
                        openCount++;
                    }
 
                    offset++;
                }
 
                // move on to the next line
                lineNumber++;
                if (lineNumber > stopLineNumber)
                    break;
 
                line = line.Snapshot.GetLineFromLineNumber(lineNumber);
                lineText = line.GetText();
                offset = 0;
            }
 
            return false;
        }
 
        private static bool FindMatchingOpenChar(SnapshotPoint start, IClassifier aggregator, char open, char close, int maxLines, out SnapshotSpan pairSpan)
        {
            pairSpan = new SnapshotSpan(start, start);
            ITextSnapshotLine line = start.GetContainingLine();
            int lineNumber = line.LineNumber;
            int offset = start - line.Start - 1;
 
            // if the offset is negative, move to the previous line
            if (offset < 0)
            {
                lineNumber--;
                line = line.Snapshot.GetLineFromLineNumber(lineNumber);
                offset = line.Length - 1;
            }
 
            string lineText = line.GetText();
 
            int stopLineNumber = 0;
            if (maxLines > 0)
                stopLineNumber = Math.Max(stopLineNumber, lineNumber - maxLines);
 
            int closeCount = 0;
            while (true)
            {
                while (offset >= 0)
                {
                    char currentChar = lineText[offset];
                    // TODO: is this the correct affinity
                    if (currentChar == open && !IsInCommentOrLiteral(aggregator, new SnapshotPoint(start.Snapshot, offset + line.Start.Position), PositionAffinity.Successor))
                    {
                        if (closeCount > 0)
                        {
                            closeCount--;
                        }
                        else
                        {
                            pairSpan = new SnapshotSpan(line.Start + offset, 1);
                            return true;
                        }
                    }
                    // TODO: is this the correct affinity
                    else if (currentChar == close && !IsInCommentOrLiteral(aggregator, new SnapshotPoint(start.Snapshot, offset + line.Start.Position), PositionAffinity.Successor))
                    {
                        closeCount++;
                    }
 
                    offset--;
                }
 
                // move to the previous line
                lineNumber--;
                if (lineNumber < stopLineNumber)
                    break;
 
                line = line.Snapshot.GetLineFromLineNumber(lineNumber);
                lineText = line.GetText();
                offset = line.Length - 1;
            }
 
            return false;
        }
 
        public IEnumerable<ITagSpan<TextMarkerTag>> GetTags(NormalizedSnapshotSpanCollection spans)
        {
            if (spans.Count == 0)
                yield break;
 
            // don't do anything if the current SnapshotPoint is not initialized or at the end of the buffer
            if (!CurrentChar.HasValue || CurrentChar.Value.Position >= CurrentChar.Value.Snapshot.Length)
                yield break;
 
            // hold on to a snapshot of the current character
            var currentChar = CurrentChar.Value;
 
            if (IsInCommentOrLiteral(Aggregator, currentChar, TextView.Caret.Position.Affinity))
                yield break;
 
            // if the requested snapshot isn't the same as the one the brace is on, translate our spans to the expected snapshot
            currentChar = currentChar.TranslateTo(spans[0].Snapshot, PointTrackingMode.Positive);
 
            // get the current char and the previous char
            char currentText = currentChar.GetChar();
            // if current char is 0 (beginning of buffer), don't move it back
            SnapshotPoint lastChar = currentChar == 0 ? currentChar : currentChar - 1;
            char lastText = lastChar.GetChar();
            SnapshotSpan pairSpan = new SnapshotSpan();
 
            if (IsMatchStartCharacter(currentText))
            {
                char closeChar = GetMatchCloseCharacter(currentText);
                /* TODO: Need to improve handling of larger blocks. this won't highlight if the matching brace is more
                 *       than 1 screen's worth of lines away. Changing this to 10 * TextView.TextViewLines.Count seemed
                 *       to improve the situation.
                 */
                if (BraceMatchingTagger.FindMatchingCloseChar(currentChar, Aggregator, currentText, closeChar, TextView.TextViewLines.Count, out pairSpan))
                {
                    yield return new TagSpan<TextMarkerTag>(new SnapshotSpan(currentChar, 1), PredefinedTextMarkerTags.BraceHighlight);
                    yield return new TagSpan<TextMarkerTag>(pairSpan, PredefinedTextMarkerTags.BraceHighlight);
                }
            }
            else if (IsMatchCloseCharacter(lastText))
            {
                var open = GetMatchOpenCharacter(lastText);
                if (BraceMatchingTagger.FindMatchingOpenChar(lastChar, Aggregator, open, lastText, TextView.TextViewLines.Count, out pairSpan))
                {
                    yield return new TagSpan<TextMarkerTag>(new SnapshotSpan(lastChar, 1), PredefinedTextMarkerTags.BraceHighlight);
                    yield return new TagSpan<TextMarkerTag>(pairSpan, PredefinedTextMarkerTags.BraceHighlight);
                }
            }
        }
 
        private void UpdateAtCaretPosition(CaretPosition caretPosition)
        {
            CurrentChar = caretPosition.Point.GetPoint(SourceBuffer, caretPosition.Affinity);
            if (!CurrentChar.HasValue)
                return;
 
            var t = TagsChanged;
            if (t != null)
                t(this, new SnapshotSpanEventArgs(new SnapshotSpan(SourceBuffer.CurrentSnapshot, 0, SourceBuffer.CurrentSnapshot.Length)));
        }
 
        private void TextView_LayoutChanged(object sender, TextViewLayoutChangedEventArgs e)
        {
            if (e.NewSnapshot != e.OldSnapshot)
                UpdateAtCaretPosition(TextView.Caret.Position);
        }
 
        private void Caret_PositionChanged(object sender, CaretPositionChangedEventArgs e)
        {
            UpdateAtCaretPosition(e.NewPosition);
        }
    }
}