// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace System.Text.Json.Serialization
{
    /// <summary>
    /// This class defines how the <see cref="JsonSerializer"/> deals with references on serialization and deserialization.
    /// Defines the core behavior of preserving references on serialization and deserialization.
    /// </summary>
    public abstract class ReferenceResolver
    {
        /// <summary>
        /// Adds an entry to the bag of references using the specified id and value.
        /// This method gets called when an $id metadata property from a JSON object is read.
        /// </summary>
        /// <param name="referenceId">The identifier of the respective JSON object or array.</param>
        /// <param name="value">The value of the respective CLR reference type object that results from parsing the JSON object.</param>
        public abstract void AddReference(string referenceId, object value);
 
        /// <summary>
        /// Gets the reference identifier of the specified value if exists; otherwise a new id is assigned.
        /// This method gets called before a CLR object is written so we can decide whether to write $id and enumerate the rest of its properties or $ref and step into the next object.
        /// </summary>
        /// <param name="value">The value of the CLR reference type object to get an id for.</param>
        /// <param name="alreadyExists">When this method returns, <see langword="true"/> if a reference to value already exists; otherwise, <see langword="false"/>.</param>
        /// <returns>The reference id for the specified object.</returns>
        public abstract string GetReference(object value, out bool alreadyExists);
 
        /// <summary>
        /// Returns the CLR reference type object related to the specified reference id.
        /// This method gets called when $ref metadata property is read.
        /// </summary>
        /// <param name="referenceId">The reference id related to the returned object.</param>
        /// <returns>The reference type object related to specified reference id.</returns>
        public abstract object ResolveReference(string referenceId);
 
        // We are breaking single responsibility on this class internally.
        // In the future, if this model is required to be exposed, we can add a base class and extend this class and a new class containing below members from that base class.
        internal virtual void PopReferenceForCycleDetection() => throw new InvalidOperationException();
 
        internal virtual void PushReferenceForCycleDetection(object value) => throw new InvalidOperationException();
 
        internal virtual bool ContainsReferenceForCycleDetection(object value) => throw new InvalidOperationException();
    }
}