// 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.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Completion;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.VisualStudio.InteractiveWindow.Commands;
 
namespace Microsoft.CodeAnalysis.Interactive;
 
/// <summary>
/// Provides completion items for Interactive Window commands (such as #help, #cls, etc.) at the start of a language buffer.
/// </summary>
internal abstract class AbstractInteractiveWindowCommandCompletionProvider : LSPCompletionProvider
{
    protected abstract bool ShouldDisplayCommandCompletions(SyntaxTree tree, int position, CancellationToken cancellationToken);
    protected abstract string GetCompletionString(string commandName);
 
    public override async Task ProvideCompletionsAsync(CompletionContext context)
    {
        var document = context.Document;
        var position = context.Position;
        var cancellationToken = context.CancellationToken;
 
        // the provider might be invoked in non-interactive context:
        var sourceText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
        if (Workspace.TryGetWorkspace(sourceText.Container, out var workspace))
        {
            if (workspace is InteractiveWindowWorkspace interactiveWorkspace)
            {
                var window = interactiveWorkspace.Window;
                if (window != null)
                {
                    var tree = await document.GetRequiredSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
 
                    if (ShouldDisplayCommandCompletions(tree, position, cancellationToken))
                    {
                        var commands = window.GetInteractiveCommands();
                        if (commands != null)
                        {
                            foreach (var command in commands.GetCommands())
                            {
                                foreach (var commandName in command.Names)
                                {
                                    var completion = GetCompletionString(commandName);
                                    context.AddItem(CommonCompletionItem.Create(
                                        completion, displayTextSuffix: "", CompletionItemRules.Default, description: command.Description.ToSymbolDisplayParts(), glyph: Glyph.Intrinsic));
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}