AyCode.Core/AyCode.Core/Serializers/AcSerializerContextBase.cs

using AyCode.Core.Serializers.Jsons;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace AyCode.Core.Serializers;

/// <summary>
/// Base class for all serializer contexts.
/// Provides GetWrapper for type metadata access with per-context tracking state.
/// GlobalMetadataCache stores metadata (thread-safe), wrappers store per-context tracking.
/// </summary>
/// <typeparam name="TMetadata">The concrete metadata type.</typeparam>
public abstract class AcSerializerContextBase<TMetadata> where TMetadata : TypeMetadataBase
{
    public byte MaxDepth { get; private set; }
    public ReferenceHandlingMode ReferenceHandling { get; internal set; }
    /// <summary>
    /// Global shared cache for metadata (thread-safe, shared across all contexts).
    /// Generic specialization ensures separate cache per TMetadata type.
    /// </summary>
    private static readonly ConcurrentDictionary<Type, TMetadata> GlobalMetadataCache = new();

    /// <summary>
    /// Per-context wrappers containing metadata + tracking state.
    /// </summary>
    private readonly Dictionary<Type, TypeMetadataWrapper<TMetadata>> _wrappers = new();

    /// <summary>
    /// Factory function to create metadata. Implemented by derived class.
    /// </summary>
    protected abstract Func<Type, TMetadata> MetadataFactory { get; }

    #region Wrapper Access

    /// <summary>
    /// Gets or creates a wrapper for the specified type.
    /// The wrapper contains metadata (from GlobalMetadataCache) + per-context tracking state.
    /// </summary>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public TypeMetadataWrapper<TMetadata> GetWrapper(Type type)
    {
        if (_wrappers.TryGetValue(type, out var wrapper))
            return wrapper;

        return GetWrapperSlow(type);
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    private TypeMetadataWrapper<TMetadata> GetWrapperSlow(Type type)
    {
        // Get metadata from global cache (thread-safe)
        var metadata = GlobalMetadataCache.GetOrAdd(type, MetadataFactory);

        // Create wrapper with metadata + tracking state (per-context)
        var wrapper = new TypeMetadataWrapper<TMetadata>(metadata);
        _wrappers[type] = wrapper;
        return wrapper;
    }

    #endregion

    #region Tracking API - int

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool TryGetValue(TypeMetadataWrapper<TMetadata> wrapper, int refId, out object? instance)
    {
        return wrapper.TryGetValue(refId, out instance);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool TryGetValue(TypeMetadataWrapper<TMetadata> wrapper, long refId, out object? instance)
    {
        return wrapper.TryGetValue(refId, out instance);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool TryGetValue(TypeMetadataWrapper<TMetadata> wrapper, Guid refId, out object? instance)
    {
        return wrapper.TryGetValue(refId, out instance);
    }

    /// <summary>
    /// For deserialization: checks if an object with this Id was already seen.
    /// If yes, returns the existing object. If no, stores this object and returns it.
    /// Uses IdentityMap.TryGetOrAddValue - single Dictionary operation!
    /// </summary>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public object TryGetOrStoreInt32(TypeMetadataWrapper<TMetadata> wrapper, object newObj, int id)
    {
        return id == 0 ? newObj : wrapper.TryGetOrStoreId(id, newObj);
    }

    /// <summary>
    /// For deserialization: checks if an object with this Id was already seen (long version).
    /// </summary>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public object TryGetOrStoreLong(TypeMetadataWrapper<TMetadata> wrapper, object newObj, long id)
    {
        return id == 0 ? newObj : wrapper.TryGetOrStoreId(id, newObj);
    }

    /// <summary>
    /// For deserialization: checks if an object with this Id was already seen (Guid version).
    /// </summary>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public object TryGetOrStoreGuid(TypeMetadataWrapper<TMetadata> wrapper, object newObj, Guid id)
    {
        return id == Guid.Empty ? newObj : wrapper.TryGetOrStoreId(id, newObj);
    }

    #endregion

    #region Reset

    /// <summary>
    /// Resets all wrapper tracking states for reuse.
    /// Does not remove wrappers - keeps them for next operation.
    /// </summary>
    public virtual void Reset(in AcSerializerOptions? options)
    {
        foreach (var wrapper in _wrappers.Values)
        {
            wrapper.ResetTracking();
        }

        if (options == null) return;

        MaxDepth = options.MaxDepth;
        ReferenceHandling = options.ReferenceHandling;
    }

    #endregion
}