// 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.Collections.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;

namespace Microsoft.CodeAnalysis.AddImport;

internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
{
    /// <summary>
    /// Code action we use when just adding a using, possibly with a project or
    /// metadata reference.  We don't use the standard code action types because
    /// we want to do things like show a glyph if this will do more than just add
    /// an import.
    /// </summary>
    private abstract class SymbolReferenceCodeAction : AddImportCodeAction
    {
        protected SymbolReferenceCodeAction(
            Document originalDocument,
            AddImportFixData fixData,
            ImmutableArray<string> additionalTags)
            : base(originalDocument, fixData, additionalTags)
        {
        }

        protected override async Task<IEnumerable<CodeActionOperation>> ComputePreviewOperationsAsync(CancellationToken cancellationToken)
        {
            var operation = await GetChangeSolutionOperationAsync(isPreview: true, cancellationToken).ConfigureAwait(false);
            return operation is null ? [] : [operation];
        }

        protected override async Task<ImmutableArray<CodeActionOperation>> ComputeOperationsAsync(
            IProgress<CodeAnalysisProgress> progress, CancellationToken cancellationToken)
        {
            var operation = await GetChangeSolutionOperationAsync(isPreview: false, cancellationToken).ConfigureAwait(false);
            if (operation is null)
            {
                return [];
            }

            return [operation];
        }

        private async Task<CodeActionOperation?> GetChangeSolutionOperationAsync(bool isPreview, CancellationToken cancellationToken)
        {
            var updatedDocument = await GetUpdatedDocumentAsync(cancellationToken).ConfigureAwait(false);

            // Defer to subtype to add any p2p or metadata refs as appropriate. If no changes to project references
            // are necessary, the call to 'UpdateProjectAsync' will return null, in which case we fall back to just
            // returning the updated document with its text changes.
            var updatedProject = await UpdateProjectAsync(updatedDocument.Project, isPreview, cancellationToken).ConfigureAwait(false);
            return updatedProject ?? new ApplyChangesOperation(updatedDocument.Project.Solution);
        }

        protected abstract Task<CodeActionOperation?> UpdateProjectAsync(Project project, bool isPreview, CancellationToken cancellationToken);
    }
}