aspnetcore/src/Microsoft.AspNetCore.Razor.Language/RazorLanguageVersion.cs

// 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.Diagnostics;

namespace Microsoft.AspNetCore.Razor.Language
{
    [DebuggerDisplay("{" + nameof(DebuggerToString) + "(),nq}")]
    public sealed class RazorLanguageVersion : IEquatable<RazorLanguageVersion>, IComparable<RazorLanguageVersion>
    {
        public static readonly RazorLanguageVersion Version_1_0 = new RazorLanguageVersion(1, 0);

        public static readonly RazorLanguageVersion Version_1_1 = new RazorLanguageVersion(1, 1);

        public static readonly RazorLanguageVersion Version_2_0 = new RazorLanguageVersion(2, 0);

        public static readonly RazorLanguageVersion Version_2_1 = new RazorLanguageVersion(2, 1);

        public static readonly RazorLanguageVersion Latest = Version_2_1;

        public static readonly RazorLanguageVersion Experimental = new RazorLanguageVersion(1337, 1337);

        public static bool TryParse(string languageVersion, out RazorLanguageVersion version)
        {
            if (languageVersion == null)
            {
                throw new ArgumentNullException(nameof(languageVersion));
            }

            if (string.Equals(languageVersion, "latest", StringComparison.OrdinalIgnoreCase))
            {
                version = Version_2_1;
                return true;
            }
            else if (string.Equals(languageVersion, "experimental", StringComparison.OrdinalIgnoreCase))
            {
                version = Experimental;
                return true;
            }
            else if (languageVersion == "2.1")
            {
                version = Version_2_1;
                return true; 
            }
            else if (languageVersion == "2.0")
            {
                version = Version_2_0;
                return true;
            }
            else if (languageVersion == "1.1")
            {
                version = Version_1_1;
                return true;
            }
            else if (languageVersion == "1.0")
            {
                version = Version_1_0;
                return true;
            }

            version = null;
            return false;
        }

        public static RazorLanguageVersion Parse(string languageVersion)
        {
            if (languageVersion == null)
            {
                throw new ArgumentNullException(nameof(languageVersion));
            }

            if (TryParse(languageVersion, out var parsed))
            {
                return parsed;
            }

            throw new ArgumentException(
                Resources.FormatRazorLanguageVersion_InvalidVersion(languageVersion), 
                nameof(languageVersion));
        }

        // Don't want anyone else constructing language versions.
        private RazorLanguageVersion(int major, int minor)
        {
            Major = major;
            Minor = minor;
        }

        public int Major { get; }

        public int Minor { get; }

        public int CompareTo(RazorLanguageVersion other)
        {
            if (other == null)
            {
                throw new ArgumentNullException(nameof(other));
            }

            var result = Major.CompareTo(other.Major);
            if (result != 0)
            {
                return result;
            }

            return Minor.CompareTo(other.Minor);
        }

        public bool Equals(RazorLanguageVersion other)
        {
            if (other == null)
            {
                return false;
            }

            // We're the only one who can create RazorLanguageVersions so reference equality is sufficient.
            return ReferenceEquals(this, other);
        }

        public override int GetHashCode()
        {
            // We don't need to do anything special for our hash code since reference equality is what we're going for.
            return base.GetHashCode();
        }
        
        public override string ToString() => $"{Major}.{Minor}";

        private string DebuggerToString() => $"Razor '{Major}.{Minor}'";
    }
}