// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Razor.DocumentMapping;
using Microsoft.CodeAnalysis.Razor.ProjectSystem;
using Microsoft.CodeAnalysis.Razor.Protocol;
 
namespace Microsoft.CodeAnalysis.Razor.CodeActions;
 
/// <summary>
/// Resolves and remaps the code action, without running formatting passes.
/// </summary>
internal class UnformattedRemappingCSharpCodeActionResolver(IDocumentMappingService documentMappingService) : ICSharpCodeActionResolver
{
    private readonly IDocumentMappingService _documentMappingService = documentMappingService;
 
    public string Action => LanguageServerConstants.CodeActions.UnformattedRemap;
 
    public async Task<CodeAction> ResolveAsync(
        DocumentContext documentContext,
        CodeAction codeAction,
        CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();
 
        if (codeAction.Edit?.DocumentChanges is null)
        {
            // Unable to resolve code action with server, return original code action
            return codeAction;
        }
 
        if (codeAction.Edit.DocumentChanges.Value.Count() != 1)
        {
            // We don't yet support multi-document code actions, return original code action
            Debug.Fail($"Encountered an unsupported multi-document code action edit with ${codeAction.Title}.");
            return codeAction;
        }
 
        var documentChanged = codeAction.Edit.DocumentChanges.Value.First();
        if (!documentChanged.TryGetFirst(out var textDocumentEdit))
        {
            // Only Text Document Edit changes are supported currently, return original code action
            return codeAction;
        }
 
        var textEdit = (TextEdit)textDocumentEdit.Edits.FirstOrDefault();
        if (textEdit is null)
        {
            // No text edit available
            return codeAction;
        }
 
        var codeDocument = await documentContext.Snapshot.GetGeneratedOutputAsync(cancellationToken).ConfigureAwait(false);
 
        if (!_documentMappingService.TryMapToRazorDocumentRange(codeDocument.GetRequiredCSharpDocument(), textEdit.Range, MappingBehavior.Inclusive, out var originalRange))
        {
            // Text edit failed to map
            return codeAction;
        }
 
        textEdit.Range = originalRange;
 
        var codeDocumentIdentifier = new OptionalVersionedTextDocumentIdentifier()
        {
            DocumentUri = new(documentContext.Uri),
        };
        codeAction.Edit = new WorkspaceEdit()
        {
            DocumentChanges = new[] {
                new TextDocumentEdit()
                {
                    TextDocument = codeDocumentIdentifier,
                    Edits = [textEdit],
                }
            },
        };
 
        return codeAction;
    }
}