// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Tagging;
 
namespace Microsoft.CodeAnalysis.Text.Shared.Extensions;
 
internal static partial class ITextSnapshotExtensions
{
    public static SnapshotPoint GetPoint(this ITextSnapshot snapshot, int position)
        => new SnapshotPoint(snapshot, position);
 
    public static SnapshotPoint? TryGetPoint(this ITextSnapshot snapshot, int lineNumber, int columnIndex)
    {
        var position = snapshot.TryGetPosition(lineNumber, columnIndex);
        if (position.HasValue)
        {
            return new SnapshotPoint(snapshot, position.Value);
        }
        else
        {
            return null;
        }
    }
 
    /// <summary>
    /// Convert a <see cref="LinePositionSpan"/> to <see cref="TextSpan"/>.
    /// </summary>
    public static TextSpan GetTextSpan(this ITextSnapshot snapshot, LinePositionSpan span)
    {
        return TextSpan.FromBounds(
            GetPosition(snapshot, span.Start.Line, span.Start.Character),
            GetPosition(snapshot, span.End.Line, span.End.Character));
    }
 
    public static int GetPosition(this ITextSnapshot snapshot, int lineNumber, int columnIndex)
        => TryGetPosition(snapshot, lineNumber, columnIndex) ?? throw new InvalidOperationException(TextEditorResources.The_snapshot_does_not_contain_the_specified_position);
 
    public static int? TryGetPosition(this ITextSnapshot snapshot, int lineNumber, int columnIndex)
    {
        if (lineNumber < 0 || lineNumber >= snapshot.LineCount)
        {
            return null;
        }
 
        var end = snapshot.GetLineFromLineNumber(lineNumber).Start.Position + columnIndex;
        if (end < 0 || end > snapshot.Length)
        {
            return null;
        }
 
        return end;
    }
 
    public static bool TryGetPosition(this ITextSnapshot snapshot, int lineNumber, int columnIndex, out SnapshotPoint position)
    {
        position = new SnapshotPoint();
 
        if (lineNumber < 0 || lineNumber >= snapshot.LineCount)
        {
            return false;
        }
 
        var line = snapshot.GetLineFromLineNumber(lineNumber);
        if (columnIndex < 0 || columnIndex >= line.Length)
        {
            return false;
        }
 
        var result = line.Start.Position + columnIndex;
        position = new SnapshotPoint(snapshot, result);
        return true;
    }
 
    public static SnapshotSpan GetSpan(this ITextSnapshot snapshot, int start, int length)
        => new SnapshotSpan(snapshot, new Span(start, length));
 
    public static SnapshotSpan GetSpanFromBounds(this ITextSnapshot snapshot, int start, int end)
        => new SnapshotSpan(snapshot, Span.FromBounds(start, end));
 
    public static SnapshotSpan GetSpan(this ITextSnapshot snapshot, Span span)
        => new SnapshotSpan(snapshot, span);
 
    public static TagSpan<TTag> GetTagSpan<TTag>(this ITextSnapshot snapshot, Span span, TTag tag) where TTag : ITag
        => new(new SnapshotSpan(snapshot, span), tag);
 
    public static SnapshotSpan GetSpan(this ITextSnapshot snapshot, int startLine, int startIndex, int endLine, int endIndex)
        => TryGetSpan(snapshot, startLine, startIndex, endLine, endIndex) ?? throw new InvalidOperationException(TextEditorResources.The_snapshot_does_not_contain_the_specified_span);
 
    public static SnapshotSpan? TryGetSpan(this ITextSnapshot snapshot, int startLine, int startIndex, int endLine, int endIndex)
    {
        var startPosition = snapshot.TryGetPosition(startLine, startIndex);
        var endPosition = snapshot.TryGetPosition(endLine, endIndex);
        if (startPosition == null || endPosition == null)
        {
            return null;
        }
 
        return new SnapshotSpan(snapshot, Span.FromBounds(startPosition.Value, endPosition.Value));
    }
 
    public static SnapshotSpan GetFullSpan(this ITextSnapshot snapshot)
    {
        Contract.ThrowIfNull(snapshot);
 
        return new SnapshotSpan(snapshot, new Span(0, snapshot.Length));
    }
 
    public static NormalizedSnapshotSpanCollection GetSnapshotSpanCollection(this ITextSnapshot snapshot)
    {
        Contract.ThrowIfNull(snapshot);
 
        return new NormalizedSnapshotSpanCollection(snapshot.GetFullSpan());
    }
 
    public static void GetLineAndCharacter(this ITextSnapshot snapshot, int position, out int lineNumber, out int characterIndex)
    {
        var line = snapshot.GetLineFromPosition(position);
 
        lineNumber = line.LineNumber;
        characterIndex = position - line.Start.Position;
    }
 
    /// <summary>
    /// Returns the leading whitespace of the line located at the specified position in the given snapshot.
    /// </summary>
    public static string GetLeadingWhitespaceOfLineAtPosition(this ITextSnapshot snapshot, int position)
    {
        Contract.ThrowIfNull(snapshot);
 
        var line = snapshot.GetLineFromPosition(position);
        var linePosition = line.GetFirstNonWhitespacePosition();
        if (!linePosition.HasValue)
        {
            return line.GetText();
        }
 
        var lineText = line.GetText();
        return lineText[..(linePosition.Value - line.Start)];
    }
 
    public static bool AreOnSameLine(this ITextSnapshot snapshot, int x1, int x2)
        => snapshot.GetLineNumberFromPosition(x1) == snapshot.GetLineNumberFromPosition(x2);
}