using System.Diagnostics.CodeAnalysis;
using System.Text.Json.Serialization;
using StabilityMatrix.Core.Models.Database;

namespace StabilityMatrix.Core.Models;

/// <summary>
/// Model file union that may be remote or local.
/// </summary>
[SuppressMessage("ReSharper", "MemberCanBePrivate.Global")]
public record HybridModelFile
{
    /// <summary>
    /// Singleton instance of <see cref="HybridModelFile"/> that represents use of a default model.
    /// </summary>
    public static HybridModelFile Default { get; } = FromRemote("@default");
    
    /// <summary>
    /// Singleton instance of <see cref="HybridModelFile"/> that represents no model.
    /// </summary>
    public static HybridModelFile None { get; } = FromRemote("@none");
    
    private string? RemoteName { get; init; }
    
    public LocalModelFile? Local { get; init; }

    [MemberNotNullWhen(true, nameof(RemoteName))]
    [MemberNotNullWhen(false, nameof(Local))]
    [JsonIgnore]
    public bool IsRemote => RemoteName != null;
    
    [JsonIgnore]
    public string FileName => IsRemote 
        ? RemoteName : Local.FileName;

    [JsonIgnore]
    public string ShortDisplayName
    {
        get
        {
            if (IsNone)
            {
                return "None";
            }

            if (IsDefault)
            {
                return "Default";
            }
            
            return Path.GetFileNameWithoutExtension(FileName);
        }
    }

    public static HybridModelFile FromLocal(LocalModelFile local)
    {
        return new HybridModelFile
        {
            Local = local
        };
    }
    
    public static HybridModelFile FromRemote(string remoteName)
    {
        return new HybridModelFile
        {
            RemoteName = remoteName
        };
    }

    public string GetId()
    {
        return $"{FileName};{IsNone};{IsDefault}";
    }
    
    private sealed class RemoteNameLocalEqualityComparer : IEqualityComparer<HybridModelFile>
    {
        public bool Equals(HybridModelFile? x, HybridModelFile? y)
        {
            if (ReferenceEquals(x, y)) return true;
            if (ReferenceEquals(x, null)) return false;
            if (ReferenceEquals(y, null)) return false;
            if (x.GetType() != y.GetType()) return false;

            return Equals(x.FileName, y.FileName) 
                   && x.IsNone == y.IsNone 
                   && x.IsDefault == y.IsDefault;
        }

        public int GetHashCode(HybridModelFile obj)
        {
            return HashCode.Combine(obj.IsNone, obj.IsDefault, obj.FileName);
        }
    }
    
    /// <summary>
    /// Whether this instance is the default model.
    /// </summary>
    public bool IsDefault => ReferenceEquals(this, Default);
    
    /// <summary>
    /// Whether this instance is no model.
    /// </summary>
    public bool IsNone => ReferenceEquals(this, None);
    
    public static IEqualityComparer<HybridModelFile> Comparer { get; } = new RemoteNameLocalEqualityComparer();
}