// 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.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using NuGet.Protocol.Core.Types;
using NuGet.Versioning;

namespace NuGet.Protocol
{
    public static class V2FeedUtilities
    {
        public static IPackageSearchMetadata CreatePackageSearchResult(
          V2FeedPackageInfo package,
          MetadataReferenceCache metadataCache,
          SearchFilter filter,
          V2FeedParser feedParser,
          Common.ILogger log,
          CancellationToken cancellationToken)
        {
            var metadata = new PackageSearchMetadataV2Feed(package, metadataCache);
            return metadata
                .WithVersions(() => GetVersions(package, metadataCache, filter, feedParser, log, cancellationToken));
        }

        private static async Task<IEnumerable<VersionInfo>> GetVersions(
            V2FeedPackageInfo package,
            MetadataReferenceCache metadataCache,
            SearchFilter filter,
            V2FeedParser feedParser,
            Common.ILogger log,
            CancellationToken cancellationToken)
        {
            cancellationToken.ThrowIfCancellationRequested();

            using (var sourceCacheContext = new SourceCacheContext())
            {
                // Update http source cache context MaxAge so that it can always go online to fetch
                // latest version of packages.
                sourceCacheContext.MaxAge = DateTimeOffset.UtcNow;

                // apply the filters to the version list returned
                var packages = await feedParser.FindPackagesByIdAsync(
                    package.Id,
                    filter.IncludeDelisted,
                    filter.IncludePrerelease,
                    sourceCacheContext,
                    log,
                    cancellationToken);

                var uniqueVersions = new HashSet<NuGetVersion>();
                var results = new List<VersionInfo>();

                foreach (var versionPackage in packages.OrderByDescending(p => p.Version))
                {
                    if (uniqueVersions.Add(versionPackage.Version))
                    {
                        var versionInfo = new VersionInfo(versionPackage.Version, versionPackage.DownloadCount)
                        {
                            PackageSearchMetadata = new PackageSearchMetadataV2Feed(versionPackage, metadataCache)
                        };

                        results.Add(versionInfo);
                    }
                }
                return results;
            }
        }
    }
}