// 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 System.Collections.Generic;
using System.Text;
using Microsoft.VisualStudio.Text;
 
namespace Microsoft.CodeAnalysis.Text;
 
public static partial class Extensions
{
    public static SourceTextContainer AsTextContainer(this ITextBuffer buffer)
        => TextBufferContainer.From(buffer);
 
    public static ITextBuffer GetTextBuffer(this SourceTextContainer textContainer)
        => TryGetTextBuffer(textContainer) ?? throw new ArgumentException(TextEditorResources.textContainer_is_not_a_SourceTextContainer_that_was_created_from_an_ITextBuffer, nameof(textContainer));
 
    public static ITextBuffer? TryGetTextBuffer(this SourceTextContainer? textContainer)
        => (textContainer as TextBufferContainer)?.TryFindEditorTextBuffer();
 
    /// <summary>
    /// Returns the <see cref="ITextSnapshot"/> behind this <see cref="SourceText"/>, or null if it wasn't created from one.
    /// 
    /// Note that multiple <see cref="ITextSnapshot"/>s may map to the same <see cref="SourceText"/> instance if it's
    /// <see cref="ITextVersion.ReiteratedVersionNumber" /> doesn't change.
    /// </summary>
    /// <returns>The underlying ITextSnapshot.</returns>
    public static ITextSnapshot? FindCorrespondingEditorTextSnapshot(this SourceText? text)
        => (text as SnapshotSourceText)?.TryFindEditorSnapshot();
 
    internal static ITextImage? TryFindCorrespondingEditorTextImage(this SourceText? text)
        => (text as SnapshotSourceText)?.TextImage;
 
    internal static TextLine AsTextLine(this ITextSnapshotLine line)
        => line.Snapshot.AsText().Lines[line.LineNumber];
 
    public static SourceText AsText(this ITextSnapshot textSnapshot)
    {
        textSnapshot.TextBuffer.Properties.TryGetProperty<ITextBufferCloneService>(typeof(ITextBufferCloneService), out var textBufferCloneServiceOpt);
        return SnapshotSourceText.From(textBufferCloneServiceOpt, textSnapshot);
    }
 
    internal static SourceText AsRoslynText(this ITextSnapshot textSnapshot, ITextBufferCloneService textBufferCloneServiceOpt, Encoding? encoding, SourceHashAlgorithm checksumAlgorithm)
        => new SnapshotSourceText.ClosedSnapshotSourceText(textBufferCloneServiceOpt, ((ITextSnapshot2)textSnapshot).TextImage, encoding, checksumAlgorithm);
 
    /// <summary>
    /// Gets the workspace corresponding to the text buffer.
    /// </summary>
    public static Workspace? GetWorkspace(this ITextBuffer buffer)
    {
        var container = buffer.AsTextContainer();
        if (Workspace.TryGetWorkspace(container, out var workspace))
        {
            return workspace;
        }
 
        return null;
    }
 
    /// <summary>
    /// Gets the <see cref="Document"/>s from the corresponding <see cref="Workspace.CurrentSolution"/> that are associated with the <see cref="ITextSnapshot"/>'s buffer,
    /// updated to contain the same text as the snapshot if necessary. There may be multiple <see cref="Document"/>s associated with the buffer
    /// if the file is linked into multiple projects or is part of a Shared Project.
    /// </summary>
    public static IEnumerable<Document> GetRelatedDocumentsWithChanges(this ITextSnapshot text)
        => text.AsText().GetRelatedDocumentsWithChanges();
 
    /// <summary>
    /// Gets the <see cref="Document"/> from the corresponding <see cref="Workspace.CurrentSolution"/> that is associated with the <see cref="ITextSnapshot"/>'s buffer
    /// in its current project context, updated to contain the same text as the snapshot if necessary. There may be multiple <see cref="Document"/>s
    /// associated with the buffer if it is linked into multiple projects or is part of a Shared Project. In this case, the <see cref="Workspace"/>
    /// is responsible for keeping track of which of these <see cref="Document"/>s is in the current project context.
    /// </summary>
    public static Document? GetOpenDocumentInCurrentContextWithChanges(this ITextSnapshot text)
        => text.AsText().GetOpenDocumentInCurrentContextWithChanges();
 
    internal static TextDocument? GetOpenTextDocumentInCurrentContextWithChanges(this ITextSnapshot text)
        => text.AsText().GetOpenTextDocumentInCurrentContextWithChanges();
 
    /// <summary>
    /// Gets the <see cref="Document"/>s from the corresponding <see cref="Workspace.CurrentSolution"/> that are associated with the <see cref="ITextBuffer"/>.
    /// There may be multiple <see cref="Document"/>s associated with the buffer if it is linked into multiple projects or is part of a Shared Project. 
    /// </summary>
    public static IEnumerable<Document> GetRelatedDocuments(this ITextBuffer buffer)
        => buffer.AsTextContainer().GetRelatedDocuments();
 
    internal static bool CanApplyChangeDocumentToWorkspace(this ITextBuffer buffer)
        => Workspace.TryGetWorkspace(buffer.AsTextContainer(), out var workspace) &&
           workspace.CanApplyChange(ApplyChangesKind.ChangeDocument);
 
    /// <summary>
    /// Get the encoding used to load this <see cref="ITextBuffer"/> if possible.
    /// <para>
    /// Note that this will return <see cref="Encoding.UTF8"/> if the <see cref="ITextBuffer"/>
    /// didn't come from an <see cref="ITextDocument"/>, or if the <see cref="ITextDocument"/>
    /// is already closed.
    /// </para>
    /// </summary>
    internal static Encoding GetEncodingOrUTF8(this ITextBuffer textBuffer)
        => textBuffer.Properties.TryGetProperty(typeof(ITextDocument), out ITextDocument textDocument)
            ? textDocument.Encoding
            : Encoding.UTF8;
}