using System;
using CeresSharp.Native;

namespace CeresSharp.Native.SafeHandles;

/// <summary>
/// Safe handle for Ceres CostFunction.
/// </summary>
internal sealed class CostFunctionHandle : BaseSafeHandle
{
    private volatile bool _ownedByProblem = false;

    private CostFunctionHandle() : base()
    {
    }

    private CostFunctionHandle(IntPtr handle, bool ownsHandle) : base(handle, ownsHandle)
    {
    }

    public static CostFunctionHandle Create(IntPtr handle)
    {
        if (handle == IntPtr.Zero)
        {
            throw new Exceptions.CeresException(Exceptions.CeresErrorCode.NullPointer, "Cost function handle is null");
        }
        return new CostFunctionHandle(handle, true);
    }

    /// <summary>
    /// Marks this cost function as owned by a Problem.
    /// When owned by Problem, the native handle should NOT be freed here
    /// because Problem/Ceres will free it when Problem is destroyed.
    /// </summary>
    internal void MarkOwnedByProblem() => _ownedByProblem = true;

    protected override void ReleaseNativeHandle(IntPtr handle)
    {
        if (_ownedByProblem)
        {
            // Problem owns this cost function - Ceres will delete it when Problem is freed.
            // Do NOT free here to avoid double-free.
            return;
        }
        // Standalone cost function - we must free it ourselves
        CeresNative.ceres_wrapper_free_autodiff_cost_function(handle);
    }
}