// 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.

#nullable disable

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.AddPackage;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.AddImport;

internal sealed class InstallPackageAndAddImportCodeAction : AddImportCodeAction
{
    public override string Title { get; }

    /// <summary>
    /// The operation that will actually install the nuget package.
    /// </summary>
    private readonly InstallPackageDirectlyCodeActionOperation _installOperation;

    /// <summary>
    /// This code action only works by installing a package.  As such, it requires a non document change (and is
    /// thus restricted in which hosts it can run).
    /// </summary>
    public InstallPackageAndAddImportCodeAction(
        Document originalDocument,
        AddImportFixData fixData,
        string title,
        InstallPackageDirectlyCodeActionOperation installOperation)
        : base(originalDocument, fixData, RequiresNonDocumentChangeTags)
    {
        Contract.ThrowIfFalse(fixData.Kind == AddImportFixKind.PackageSymbol);
        Title = title;
        _installOperation = installOperation;
    }

    /// <summary>
    /// For preview purposes we return all the operations in a list.  This way the 
    /// preview system stiches things together in the UI to make a suitable display.
    /// i.e. if we have a SolutionChangedOperation and some other operation with a 
    /// Title, then the UI will show that nicely to the user.
    /// </summary>
    protected override async Task<IEnumerable<CodeActionOperation>> ComputePreviewOperationsAsync(CancellationToken cancellationToken)
    {
        // Make a SolutionChangeAction.  This way we can let it generate the diff
        // preview appropriately.
        var solutionChangeAction = SolutionChangeAction.Create("", GetUpdatedSolutionAsync, "");

        using var _ = ArrayBuilder<CodeActionOperation>.GetInstance(out var result);
        result.AddRange(await solutionChangeAction.GetPreviewOperationsAsync(
            this.OriginalDocument.Project.Solution, cancellationToken).ConfigureAwait(false));
        result.Add(_installOperation);
        return result.ToImmutableAndClear();
    }

    private async Task<Solution> GetUpdatedSolutionAsync(CancellationToken cancellationToken)
    {
        var newDocument = await GetUpdatedDocumentAsync(cancellationToken).ConfigureAwait(false);
        var newRoot = await newDocument.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);

        // Suppress diagnostics on the import we create.  Because we only get here when we are 
        // adding a nuget package, it is certainly the case that in the preview this will not
        // bind properly.  It will look silly to show such an error, so we just suppress things.
        var updatedRoot = newRoot.WithAdditionalAnnotations(SuppressDiagnosticsAnnotation.Create());
        var updatedDocument = newDocument.WithSyntaxRoot(updatedRoot);

        return updatedDocument.Project.Solution;
    }

    /// <summary>
    /// However, for application purposes, we end up returning a single operation
    /// that will then apply all our sub actions in order, stopping the moment
    /// one of them fails.
    /// </summary>
    protected override async Task<IEnumerable<CodeActionOperation>> ComputeOperationsAsync(
        CancellationToken cancellationToken)
    {
        var updatedDocument = await GetUpdatedDocumentAsync(cancellationToken).ConfigureAwait(false);

        var oldText = await OriginalDocument.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
        var newText = await updatedDocument.GetValueTextAsync(cancellationToken).ConfigureAwait(false);

        return [new InstallPackageAndAddImportOperation(
                OriginalDocument.Id, oldText, newText, _installOperation)];
    }

    private sealed class InstallPackageAndAddImportOperation(
        DocumentId changedDocumentId,
        SourceText oldText,
        SourceText newText,
        InstallPackageDirectlyCodeActionOperation item2) : CodeActionOperation
    {
        private readonly DocumentId _changedDocumentId = changedDocumentId;
        private readonly SourceText _oldText = oldText;
        private readonly SourceText _newText = newText;
        private readonly InstallPackageDirectlyCodeActionOperation _installPackageOperation = item2;

        internal override bool ApplyDuringTests => _installPackageOperation.ApplyDuringTests;
        public override string Title => _installPackageOperation.Title;

        internal override async Task<bool> TryApplyAsync(
            Workspace workspace, Solution originalSolution, IProgress<CodeAnalysisProgress> progressTracker, CancellationToken cancellationToken)
        {
            var newSolution = workspace.CurrentSolution.WithDocumentText(
                _changedDocumentId, _newText);

            // First make the changes to add the import to the document.
            if (workspace.TryApplyChanges(newSolution, progressTracker))
            {
                if (await _installPackageOperation.TryApplyAsync(workspace, originalSolution, progressTracker, cancellationToken).ConfigureAwait(true))
                {
                    return true;
                }

                // Installing the nuget package failed.  Roll back the workspace.
                var rolledBackSolution = workspace.CurrentSolution.WithDocumentText(
                    _changedDocumentId, _oldText);
                workspace.TryApplyChanges(rolledBackSolution, progressTracker);
            }

            return false;
        }
    }
}