using System;

namespace OpenMacroBoard.SDK.Internals
{
    internal static class ConstrainedContext
    {
        /// <summary>
        /// Creates a context which might depend on the provided item or a clone of that item.
        /// </summary>
        /// <remarks>
        /// <para>This is useful in situation where you only want to do an expensive operation
        /// for <see cref="IDisposable"/> types when needed. The <see cref="ConditionalDisposable{T}"/>
        /// makes sure that elements that depend on the parent (borrow, no copy) will not be disposed
        /// but cloned (owned copies) will be disposed.</para>
        /// </remarks>
        /// <typeparam name="TInput">Input type.</typeparam>
        /// <typeparam name="TOutput">Output type.</typeparam>
        public static ConditionalDisposable<TOutput> For<TInput, TOutput>(
            TInput item,
            Func<TInput, TOutput> borrow,
            Func<TInput, TOutput> ownedCopy
        )
            where TInput : class, IDisposable
            where TOutput : class, IDisposable
        {
            var borrowedResult = borrow(item);

            if (borrowedResult is not null)
            {
                return new ConditionalDisposable<TOutput>(borrowedResult, false);
            }

            var ownedResult = ownedCopy(item);

            return new ConditionalDisposable<TOutput>(ownedResult, true);
        }
    }
}