// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

#nullable disable

using System;
using System.Globalization;
using System.Linq;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using NuGet.Common;
using NuGet.Protocol.Core.Types;
using NuGet.Protocol.Utility;
using NuGet.Shared;

namespace NuGet.Protocol
{
    public class RepositorySignatureResourceProvider : ResourceProvider
    {
        private readonly IEnvironmentVariableReader _environmentVariableReader;

        public RepositorySignatureResourceProvider() : this(null) { }

        internal RepositorySignatureResourceProvider(IEnvironmentVariableReader environmentVariableReader)
           : base(typeof(RepositorySignatureResource),
                 nameof(RepositorySignatureResource),
                 NuGetResourceProviderPositions.Last)
        {
            _environmentVariableReader = environmentVariableReader;
        }

        public override async Task<Tuple<bool, INuGetResource>> TryCreate(SourceRepository source, CancellationToken token)
        {
            RepositorySignatureResource resource = null;
            var serviceIndex = await source.GetResourceAsync<ServiceIndexResourceV3>(token);
            if (serviceIndex != null)
            {
                var serviceEntry = serviceIndex.GetServiceEntries(ServiceTypes.RepositorySignatures).FirstOrDefault();

                if (serviceEntry != null)
                {
                    resource = await GetRepositorySignatureResourceAsync(source, serviceEntry, NullLogger.Instance, token);
                }
            }

            return new Tuple<bool, INuGetResource>(resource != null, resource);
        }

        private async Task<RepositorySignatureResource> GetRepositorySignatureResourceAsync(
            SourceRepository source,
            ServiceIndexEntry serviceEntry,
            ILogger log,
            CancellationToken token)
        {
            var repositorySignaturesResourceUri = serviceEntry.Uri;

            if (repositorySignaturesResourceUri == null
                || !string.Equals(repositorySignaturesResourceUri.Scheme, "https", StringComparison.OrdinalIgnoreCase)
                && !string.Equals(repositorySignaturesResourceUri.Scheme, "http", StringComparison.OrdinalIgnoreCase))
            {
                throw new FatalProtocolException(string.Format(CultureInfo.CurrentCulture, Strings.RepositorySignaturesResourceMustBeHttps, source.PackageSource.Source));
            }

            var httpSourceResource = await source.GetResourceAsync<HttpSourceResource>(token);
            var client = httpSourceResource.HttpSource;
            var cacheKey = GenerateCacheKey(serviceEntry);

            const int maxRetries = 3;
            for (var retry = 1; retry <= maxRetries; retry++)
            {
                using (var sourceCacheContext = new SourceCacheContext())
                {
                    var cacheContext = HttpSourceCacheContext.Create(sourceCacheContext, isFirstAttempt: retry == 1);

                    try
                    {
                        return await client.GetAsync(
                            new HttpSourceCachedRequest(
                                serviceEntry.Uri.AbsoluteUri,
                                cacheKey,
                                cacheContext)
                            {
                                EnsureValidContents = stream => HttpStreamValidation.ValidateJObject(repositorySignaturesResourceUri.AbsoluteUri, stream),
                                MaxTries = 1,
                                IsRetry = retry > 1,
                                IsLastAttempt = retry == maxRetries
                            },
                            async httpSourceResult =>
                            {
                                if (NuGetFeatureFlags.UseSystemTextJsonDeserializationFeatureSwitch
                                    || NuGetFeatureFlags.IsSystemTextJsonDeserializationEnabledByEnvironment(_environmentVariableReader))
                                {
                                    var model = await JsonSerializer.DeserializeAsync(
                                        httpSourceResult.Stream,
                                        RepositorySignatureJsonContext.Default.RepositorySignatureModel,
                                        token);
                                    return new RepositorySignatureResource(model, source);
                                }
                                else
                                {
                                    var json = await httpSourceResult.Stream.AsJObjectAsync(token);
                                    return new RepositorySignatureResource(json, source);
                                }
                            },
                            log,
                            token);
                    }
                    catch (Exception ex) when (retry < maxRetries)
                    {
                        var message = string.Format(CultureInfo.CurrentCulture, Strings.Log_RetryingRepositorySignature, repositorySignaturesResourceUri.AbsoluteUri)
                            + Environment.NewLine
                            + ExceptionUtilities.DisplayMessage(ex);
                        log.LogMinimal(message);
                    }
                    catch (Exception ex) when (retry == maxRetries)
                    {
                        var message = string.Format(CultureInfo.CurrentCulture, Strings.Log_FailedToReadRepositorySignature, repositorySignaturesResourceUri.AbsoluteUri);

                        throw new FatalProtocolException(message, ex);
                    }
                }
            }

            return null;
        }

        private static string GenerateCacheKey(ServiceIndexEntry serviceEntry)
        {
#if NETCOREAPP
            var index = serviceEntry.Type.IndexOf('/', StringComparison.Ordinal);
#else
            var index = serviceEntry.Type.IndexOf('/');
#endif
            var version = serviceEntry.Type.Substring(index + 1).Trim();

            return $"repository_signatures_{version}";
        }
    }
}