// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using Microsoft.AspNetCore.Razor.Language.Legacy;
using Microsoft.VisualStudio.Utilities;

namespace Microsoft.VisualStudio.Text
{
    public class StringTextSnapshot : ITextSnapshot2
    {
        private readonly List<ITextSnapshotLine> _lines;

        public StringTextSnapshot(string content)
        {
            Content = content;
            _lines = new List<ITextSnapshotLine>();

            var start = 0;
            var delimiterIndex = 0;
            while (delimiterIndex != -1)
            {
                var delimiterLength = 2;
                delimiterIndex = Content.IndexOf("\r\n", start);

                if (delimiterIndex == -1)
                {
                    delimiterLength = 1;
                    delimiterIndex = Content.IndexOfAny(ParserHelpers.NewLineCharacters, start);
                }

                var nextLineStartIndex = delimiterIndex != -1 ? delimiterIndex + delimiterLength : Content.Length;

                var lineText = Content.Substring(start, nextLineStartIndex - start);
                _lines.Add(new SnapshotLine(lineText, start, this));

                start = nextLineStartIndex;
            }
        }

        public string Content { get; }

        public char this[int position] => Content[position];

        public ITextVersion Version { get; } = new TextVersion();

        public int Length => Content.Length;

        public ITextBuffer TextBuffer { get; set; }

        public IContentType ContentType => throw new NotImplementedException();

        public int LineCount => throw new NotImplementedException();

        public IEnumerable<ITextSnapshotLine> Lines => throw new NotImplementedException();

        public ITextImage TextImage => new StringTextImage(Content);

        public void CopyTo(int sourceIndex, char[] destination, int destinationIndex, int count) => Content.CopyTo(sourceIndex, destination, destinationIndex, count);

        public string GetText(int startIndex, int length) => Content.Substring(startIndex, length);

        public string GetText() => Content;

        public char[] ToCharArray(int startIndex, int length) => Content.ToCharArray();

        public ITextSnapshotLine GetLineFromPosition(int position)
        {
            var matchingLine = _lines.FirstOrDefault(line => line.Start + line.LengthIncludingLineBreak > position);

            if (position < 0 || matchingLine == null)
            {
                throw new ArgumentOutOfRangeException();
            }

            return matchingLine;
        }

        public ITextSnapshotLine GetLineFromLineNumber(int lineNumber)
        {
            if (lineNumber < 0 || lineNumber >= _lines.Count)
            {
                throw new ArgumentOutOfRangeException(nameof(lineNumber));
            }

            return _lines[lineNumber];
        }

        public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode)
        {
            return new SnapshotTrackingPoint(position);
        }

        public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

        public ITrackingSpan CreateTrackingSpan(VisualStudio.Text.Span span, SpanTrackingMode trackingMode) => throw new NotImplementedException();

        public ITrackingSpan CreateTrackingSpan(VisualStudio.Text.Span span, SpanTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

        public ITrackingSpan CreateTrackingSpan(int start, int length, SpanTrackingMode trackingMode) => throw new NotImplementedException();

        public ITrackingSpan CreateTrackingSpan(int start, int length, SpanTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

        public int GetLineNumberFromPosition(int position) => throw new NotImplementedException();

        public string GetText(VisualStudio.Text.Span span) => throw new NotImplementedException();

        public void Write(TextWriter writer, VisualStudio.Text.Span span) => throw new NotImplementedException();

        public void Write(TextWriter writer) => throw new NotImplementedException();

        public void SaveToFile(string filePath, bool replaceFile, Encoding encoding)
        {
            throw new NotImplementedException();
        }

        private class TextVersion : ITextVersion
        {
            public INormalizedTextChangeCollection Changes { get; } = new TextChangeCollection();

            public ITextVersion Next => throw new NotImplementedException();

            public int Length => throw new NotImplementedException();

            public ITextBuffer TextBuffer => throw new NotImplementedException();

            public int VersionNumber => throw new NotImplementedException();

            public int ReiteratedVersionNumber => throw new NotImplementedException();

            public ITrackingSpan CreateCustomTrackingSpan(VisualStudio.Text.Span span, TrackingFidelityMode trackingFidelity, object customState, CustomTrackToVersion behavior) => throw new NotImplementedException();

            public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode) => throw new NotImplementedException();

            public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

            public ITrackingSpan CreateTrackingSpan(VisualStudio.Text.Span span, SpanTrackingMode trackingMode) => throw new NotImplementedException();

            public ITrackingSpan CreateTrackingSpan(VisualStudio.Text.Span span, SpanTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

            public ITrackingSpan CreateTrackingSpan(int start, int length, SpanTrackingMode trackingMode) => throw new NotImplementedException();

            public ITrackingSpan CreateTrackingSpan(int start, int length, SpanTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) => throw new NotImplementedException();

            private class TextChangeCollection : List<ITextChange>, INormalizedTextChangeCollection
            {
                public bool IncludesLineChanges => false;
            }
        }

        private class SnapshotTrackingPoint : ITrackingPoint
        {
            private readonly int _position;

            public SnapshotTrackingPoint(int position)
            {
                _position = position;
            }

            public ITextBuffer TextBuffer => throw new NotImplementedException();

            public PointTrackingMode TrackingMode => throw new NotImplementedException();

            public TrackingFidelityMode TrackingFidelity => throw new NotImplementedException();

            public char GetCharacter(ITextSnapshot snapshot) => throw new NotImplementedException();

            public SnapshotPoint GetPoint(ITextSnapshot snapshot) => throw new NotImplementedException();

            public int GetPosition(ITextSnapshot snapshot) => _position;

            public int GetPosition(ITextVersion version) => throw new NotImplementedException();
        }

        private class SnapshotLine : ITextSnapshotLine
        {
            private readonly string _contentWithLineBreak;
            private readonly string _content;

            public SnapshotLine(string contentWithLineBreak, int start, ITextSnapshot owner)
            {
                _contentWithLineBreak = contentWithLineBreak;
                _content = contentWithLineBreak;

                if (_content.EndsWith("\r\n"))
                {
                    _content = _content.Substring(0, _content.Length - 2);
                }
                else if(_content.Length > 0 && ParserHelpers.NewLineCharacters.Contains(_content[_content.Length - 1]))
                {
                    _content = _content.Substring(0, _content.Length - 1);
                }

                Start = new SnapshotPoint(owner, start);
                End = new SnapshotPoint(owner, start + _content.Length);
                Snapshot = owner;
                LineNumber = (owner as StringTextSnapshot)._lines.Count;
            }

            public ITextSnapshot Snapshot { get; }

            public SnapshotPoint Start { get; }

            public int Length => _content.Length;

            public int LengthIncludingLineBreak => _contentWithLineBreak.Length;

            public int LineBreakLength => _contentWithLineBreak.Length - _content.Length;

            public string GetText() => _content;

            public string GetLineBreakText() => _contentWithLineBreak.Substring(_content.Length);

            public string GetTextIncludingLineBreak() => _contentWithLineBreak;

            public int LineNumber { get; }

            public SnapshotPoint End { get; }

            public SnapshotSpan Extent => throw new NotImplementedException();

            public SnapshotSpan ExtentIncludingLineBreak => throw new NotImplementedException();

            public SnapshotPoint EndIncludingLineBreak => throw new NotImplementedException();
        }
    }
}