// 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.Collections.Immutable;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.LanguageServer.Handler;
using Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.EditAndContinue;
 
internal static partial class EditAndContinueDiagnosticSource
{
    private sealed class OpenDocumentSource(Document document) : AbstractDocumentDiagnosticSource<Document>(document)
    {
        public override bool IsLiveSource()
            => true;
 
        public override async Task<ImmutableArray<DiagnosticData>> GetDiagnosticsAsync(RequestContext context, CancellationToken cancellationToken)
        {
            var designTimeDocument = Document;
            var designTimeSolution = designTimeDocument.Project.Solution;
            var services = designTimeSolution.Services;
 
            // Do not report EnC diagnostics for a non-host workspace, or if Hot Reload/EnC session is not active.
            if (designTimeSolution.WorkspaceKind != WorkspaceKind.Host ||
                services.GetService<IEditAndContinueWorkspaceService>()?.SessionTracker is not { IsSessionActive: true } sessionStateTracker)
            {
                return [];
            }
 
            var applyDiagnostics = sessionStateTracker.ApplyChangesDiagnostics.WhereAsArray(static (data, id) => data.DocumentId == id, designTimeDocument.Id);
 
            // Only create and synchronize compile-time solution if we need it.
            var compileTimeSolution = services.GetRequiredService<ICompileTimeSolutionProvider>().GetCompileTimeSolution(designTimeSolution);
 
            var compileTimeDocument = await CompileTimeSolutionProvider.TryGetCompileTimeDocumentAsync(designTimeDocument, compileTimeSolution, cancellationToken).ConfigureAwait(false);
            if (compileTimeDocument == null)
            {
                return applyDiagnostics;
            }
 
            // EnC services should never be called on a design-time solution.
 
            var proxy = new RemoteEditAndContinueServiceProxy(services);
            var spanLocator = services.GetService<IActiveStatementSpanLocator>();
 
            var activeStatementSpanProvider = spanLocator != null
                ? new ActiveStatementSpanProvider((documentId, filePath, cancellationToken) => spanLocator.GetSpansAsync(compileTimeSolution, documentId, filePath, cancellationToken))
                : static (_, _, _) => ValueTaskFactory.FromResult(ImmutableArray<ActiveStatementSpan>.Empty);
 
            var rudeEditDiagnostics = await proxy.GetDocumentDiagnosticsAsync(compileTimeDocument, activeStatementSpanProvider, cancellationToken).ConfigureAwait(false);
 
            // TODO: remove
            // We pretend the diagnostic is in the original document, but use the mapped line span.
            // Razor will ignore the column (which will be off because #line directives can't currently map columns) and only use the line number.
            rudeEditDiagnostics = rudeEditDiagnostics.SelectAsArray(data => (designTimeDocument != compileTimeDocument) ? RemapLocation(designTimeDocument, data) : data);
 
            return applyDiagnostics.AddRange(rudeEditDiagnostics);
        }
 
        private static DiagnosticData RemapLocation(Document designTimeDocument, DiagnosticData data)
        {
            Debug.Assert(data.DataLocation != null);
            Debug.Assert(designTimeDocument.FilePath != null);
 
            // If the location in the generated document is in a scope of user-visible #line mapping use the mapped span,
            // otherwise (if it's hidden) display the diagnostic at the start of the file.
            var span = data.DataLocation.UnmappedFileSpan != data.DataLocation.MappedFileSpan ? data.DataLocation.MappedFileSpan.Span : default;
            var location = new DiagnosticDataLocation(new FileLinePositionSpan(designTimeDocument.FilePath, span));
 
            return data.WithLocations(location, additionalLocations: []);
        }
    }
 
    public static IDiagnosticSource CreateOpenDocumentSource(Document document)
        => new OpenDocumentSource(document);
}