// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Collections.Generic;
using Microsoft.VisualStudio.Text;
 
namespace Microsoft.VisualStudio.LanguageServer.ContainedLanguage;
 
internal class DefaultLSPDocument : LSPDocument
{
    private LSPDocumentSnapshot? _currentSnapshot;
    private IReadOnlyList<VirtualDocument> _virtualDocuments;
 
    public DefaultLSPDocument(
        Uri uri,
        ITextBuffer textBuffer,
        IReadOnlyList<VirtualDocument> virtualDocuments)
    {
        if (uri is null)
        {
            throw new ArgumentNullException(nameof(uri));
        }
 
        if (textBuffer is null)
        {
            throw new ArgumentNullException(nameof(textBuffer));
        }
 
        if (virtualDocuments is null)
        {
            throw new ArgumentNullException(nameof(virtualDocuments));
        }
 
        Uri = uri;
        TextBuffer = textBuffer;
        _virtualDocuments = virtualDocuments;
    }
 
    public override int Version => TextBuffer.CurrentSnapshot.Version.VersionNumber;
 
    public override Uri Uri { get; }
 
    public override ITextBuffer TextBuffer { get; }
 
    public override IReadOnlyList<VirtualDocument> VirtualDocuments => _virtualDocuments;
 
    public override LSPDocumentSnapshot CurrentSnapshot
    {
        get
        {
            if (TextBuffer.CurrentSnapshot.ContentType.IsOfType(InertContentType.Instance.TypeName))
            {
                // TextBuffer is tearing itself down, return last known snapshot to avoid generating
                // a snapshot for an invalid TextBuffer
                return _currentSnapshot!;
            }
 
            if (_currentSnapshot?.Snapshot != TextBuffer.CurrentSnapshot)
            {
                _currentSnapshot = UpdateSnapshot();
            }
 
            return _currentSnapshot;
        }
    }
 
    internal override void SetVirtualDocuments(IReadOnlyList<VirtualDocument> virtualDocuments)
    {
        _virtualDocuments = virtualDocuments;
 
        _currentSnapshot = UpdateSnapshot();
    }
 
    public override LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(IReadOnlyList<ITextChange> changes, int hostDocumentVersion, object? state)
    {
        if (!TryGetVirtualDocument<TVirtualDocument>(out var virtualDocument))
        {
            throw new InvalidOperationException($"Cannot update virtual document of type {typeof(TVirtualDocument)} because LSP document {Uri} does not contain a virtual document of that type.");
        }
 
        return UpdateVirtualDocument<TVirtualDocument>(virtualDocument, changes, hostDocumentVersion, state);
    }
 
    public override LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(TVirtualDocument virtualDocument, IReadOnlyList<ITextChange> changes, int hostDocumentVersion, object? state)
    {
        virtualDocument.Update(changes, hostDocumentVersion, state);
 
        _currentSnapshot = UpdateSnapshot();
 
        return CurrentSnapshot;
    }
 
    private DefaultLSPDocumentSnapshot UpdateSnapshot()
    {
        var virtualDocumentSnapshots = new VirtualDocumentSnapshot[VirtualDocuments.Count];
        for (var i = 0; i < VirtualDocuments.Count; i++)
        {
            virtualDocumentSnapshots[i] = VirtualDocuments[i].CurrentSnapshot;
        }
 
        return new DefaultLSPDocumentSnapshot(Uri, TextBuffer.CurrentSnapshot, virtualDocumentSnapshots, Version);
    }
 
    private class DefaultLSPDocumentSnapshot : LSPDocumentSnapshot
    {
        public DefaultLSPDocumentSnapshot(
            Uri uri,
            ITextSnapshot snapshot,
            IReadOnlyList<VirtualDocumentSnapshot> virtualDocuments,
            int version)
        {
            if (uri is null)
            {
                throw new ArgumentNullException(nameof(uri));
            }
 
            if (snapshot is null)
            {
                throw new ArgumentNullException(nameof(snapshot));
            }
 
            if (virtualDocuments is null)
            {
                throw new ArgumentNullException(nameof(virtualDocuments));
            }
 
            Uri = uri;
            Snapshot = snapshot;
            VirtualDocuments = virtualDocuments;
            Version = version;
        }
 
        public override Uri Uri { get; }
 
        public override ITextSnapshot Snapshot { get; }
 
        public override IReadOnlyList<VirtualDocumentSnapshot> VirtualDocuments { get; }
 
        public override int Version { get; }
    }
}