// 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;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.Serialization;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis;
 
#pragma warning disable CA1200 // Avoid using cref tags with a prefix
/// <summary>
/// An identifier that can be used to refer to the same <see cref="Project"/> across versions.
/// </summary>
/// <remarks>
/// This supports the general message-pack <see cref="DataContractAttribute"/> of being serializable.  However, in
/// practice, this is not serialized directly, but through the use of a custom formatter <see
/// cref="T:Microsoft.CodeAnalysis.Remote.MessagePackFormatters.ProjectIdFormatter"/>
/// </remarks>
#pragma warning restore CA1200 // Avoid using cref tags with a prefix
[DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
[DataContract]
public sealed class ProjectId : IEquatable<ProjectId>, IComparable<ProjectId>
{
    /// <summary>
    /// Checksum of this ProjectId, built only from <see cref="Id"/>.
    /// </summary>
    private SingleInitNullable<Checksum> _lazyChecksum;
 
    /// <summary>
    /// The system generated unique id.
    /// </summary>
    [DataMember(Order = 0)]
    public Guid Id { get; }
 
    /// <summary>
    /// An optional name to show <em>only</em> for debugger-display purposes.  This must not be used for any other
    /// purpose.  Importantly, it must not be part of the equality/hashing/comparable contract of this type (including
    /// <see cref="_lazyChecksum"/>).
    /// </summary>
    [DataMember(Order = 1)]
    private readonly string? _debugName;
 
    private ProjectId(Guid guid, string? debugName)
    {
        this.Id = guid;
        _debugName = debugName;
    }
 
    /// <summary>
    /// Create a new ProjectId instance.
    /// </summary>
    /// <param name="debugName">An optional name to make this id easier to recognize while debugging.</param>
    public static ProjectId CreateNewId(string? debugName = null)
        => new(Guid.NewGuid(), debugName);
 
    public static ProjectId CreateFromSerialized(Guid id, string? debugName = null)
    {
        if (id == Guid.Empty)
        {
            throw new ArgumentException(nameof(id));
        }
 
        return new ProjectId(id, debugName);
    }
 
    internal string? DebugName => _debugName;
 
    private string GetDebuggerDisplay()
        => string.Format("({0}, #{1} - {2})", this.GetType().Name, this.Id, _debugName);
 
    public override string ToString()
        => GetDebuggerDisplay();
 
    public override bool Equals(object? obj)
        => this.Equals(obj as ProjectId);
 
    public bool Equals(ProjectId? other)
        => other is not null &&
            this.Id == other.Id;
 
    public static bool operator ==(ProjectId? left, ProjectId? right)
        => EqualityComparer<ProjectId?>.Default.Equals(left, right);
 
    public static bool operator !=(ProjectId? left, ProjectId? right)
        => !(left == right);
 
    public override int GetHashCode()
        => this.Id.GetHashCode();
 
    internal void WriteTo(ObjectWriter writer)
    {
        writer.WriteGuid(Id);
        writer.WriteString(DebugName);
    }
 
    internal static ProjectId ReadFrom(ObjectReader reader)
    {
        var guid = reader.ReadGuid();
        var debugName = reader.ReadString();
 
        return CreateFromSerialized(guid, debugName);
    }
 
    internal Checksum Checksum
        => _lazyChecksum.Initialize(static @this => Checksum.Create(@this,
            static (@this, writer) =>
            {
                // Combine "ProjectId" string and guid.  That way in the off chance that something in the stack uses
                // the same Guid for something like a Solution or Document, that we'll still consider the checksums
                // different.
                writer.WriteString(nameof(ProjectId));
                writer.WriteGuid(@this.Id);
            }), this);
 
    int IComparable<ProjectId>.CompareTo(ProjectId? other)
    {
        if (other is null)
            return 1;
 
        return this.Id.CompareTo(other.Id);
    }
}