// 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.Runtime.Serialization;
using Microsoft.CodeAnalysis.Host;

namespace Microsoft.CodeAnalysis.Storage;

/// <summary>
/// Handle that can be used with <see cref="IChecksummedPersistentStorage"/> to read data for a
/// <see cref="Document"/> without needing to have the entire <see cref="Document"/> snapshot available.
/// This is useful for cases where acquiring an entire snapshot might be expensive (for example, during 
/// solution load), but querying the data is still desired.
/// </summary>
[DataContract]
internal readonly struct DocumentKey(ProjectKey project, DocumentId id, string? filePath, string name) : IEqualityComparer<DocumentKey>, IEquatable<DocumentKey>
{
    [DataMember(Order = 0)]
    public readonly ProjectKey Project = project;

    [DataMember(Order = 1)]
    public readonly DocumentId Id = id;

    [DataMember(Order = 2)]
    public readonly string? FilePath = filePath;

    [DataMember(Order = 3)]
    public readonly string Name = name;

    public static DocumentKey ToDocumentKey(Document document)
        => ToDocumentKey(ProjectKey.ToProjectKey(document.Project), document.State);

    public static DocumentKey ToDocumentKey(ProjectKey projectKey, TextDocumentState state)
        => new(projectKey, state.Id, state.FilePath, state.Name);

    public override bool Equals(object? obj)
        => obj is DocumentKey other && Equals(other);

    public bool Equals(DocumentKey other)
        => this.Id == other.Id;

    public override int GetHashCode()
        => this.Id.GetHashCode();

    public bool Equals(DocumentKey x, DocumentKey y)
        => x.Equals(y);

    public int GetHashCode(DocumentKey obj)
        => obj.GetHashCode();
}