// 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 NuGet.Shared;
using NuGet.Versioning;

namespace NuGet.Packaging.Core
{
    /// <summary>
    /// Compares the Id, Version, and Version release label. Version build metadata is ignored.
    /// </summary>
    public class PackageIdentityComparer : IPackageIdentityComparer
    {
        private readonly IVersionComparer _versionComparer;

        /// <summary>
        /// Default version range comparer.
        /// </summary>
        public PackageIdentityComparer()
            : this(VersionComparer.Default)
        {
        }

        /// <summary>
        /// Compare versions with a specific VersionComparison
        /// </summary>
        public PackageIdentityComparer(VersionComparison versionComparison)
            : this(VersionComparer.Get(versionComparison))
        {
        }

        /// <summary>
        /// Compare versions with a specific IVersionComparer
        /// </summary>
        public PackageIdentityComparer(IVersionComparer versionComparer)
        {
            if (versionComparer == null)
            {
                throw new ArgumentNullException(nameof(versionComparer));
            }

            _versionComparer = versionComparer;
        }

        /// <summary>
        /// Default comparer that compares on the id, version, and version release labels.
        /// </summary>
        public static PackageIdentityComparer Default { get; } = new PackageIdentityComparer();

        internal static PackageIdentityComparer Version { get; } = new PackageIdentityComparer(VersionComparison.Version);
        internal static PackageIdentityComparer VersionRelease { get; } = new PackageIdentityComparer(VersionComparison.VersionRelease);
        internal static PackageIdentityComparer VersionReleaseMetadata { get; } = new PackageIdentityComparer(VersionComparison.VersionReleaseMetadata);

        internal static PackageIdentityComparer Get(VersionComparison versionComparison)
        {
            return versionComparison switch
            {
                VersionComparison.Default => Default,
                VersionComparison.Version => Version,
                VersionComparison.VersionRelease => VersionRelease,
                VersionComparison.VersionReleaseMetadata => VersionReleaseMetadata,
                _ => new PackageIdentityComparer(versionComparison),
            };
        }

        /// <summary>
        /// True if the package identities are the same when ignoring build metadata.
        /// </summary>
        public bool Equals(PackageIdentity? x, PackageIdentity? y)
        {
            if (ReferenceEquals(x, y))
            {
                return true;
            }

            if (ReferenceEquals(x, null)
                || ReferenceEquals(y, null))
            {
                return false;
            }

            return _versionComparer.Equals(x.Version!, y.Version!)
                && StringComparer.OrdinalIgnoreCase.Equals(x.Id, y.Id);
        }

        /// <summary>
        /// Hash code of the id and version
        /// </summary>
        public int GetHashCode(PackageIdentity obj)
        {
            if (ReferenceEquals(obj, null))
            {
                return 0;
            }

            var combiner = new HashCodeCombiner();

            combiner.AddObject(obj.Id, StringComparer.OrdinalIgnoreCase);
            combiner.AddObject(obj.Version, _versionComparer);

            return combiner.CombinedHash;
        }

        /// <summary>
        /// Compares on the Id first, then version
        /// </summary>
        public int Compare(PackageIdentity? x, PackageIdentity? y)
        {
            if (ReferenceEquals(x, y))
            {
                return 0;
            }

            if (ReferenceEquals(x, null))
            {
                return -1;
            }

            if (ReferenceEquals(y, null))
            {
                return 1;
            }

            int result = StringComparer.OrdinalIgnoreCase.Compare(x.Id, y.Id);

            if (result == 0)
            {
                result = _versionComparer.Compare(x.Version!, y.Version!);
            }

            return result;
        }
    }
}