using System;

namespace Umbraco.Core.Scoping
{
    /// <summary>
    /// Provides a base class for scope contextual objects.
    /// </summary>
    /// <remarks>
    /// <para>A scope contextual object is enlisted in the current scope context,
    /// if any, and released when the context exists. It must be used in a 'using'
    /// block, and will be released when disposed, if not part of a scope.</para>
    /// </remarks>
    public abstract class ScopeContextualBase : IDisposable
    {
        private bool _scoped;

        /// <summary>
        /// Gets a contextual object.
        /// </summary>
        /// <typeparam name="T">The type of the object.</typeparam>
        /// <param name="scopeProvider">A scope provider.</param>
        /// <param name="key">A context key for the object.</param>
        /// <param name="ctor">A function producing the contextual object.</param>
        /// <returns>The contextual object.</returns>
        /// <remarks>
        /// <para></para>
        /// </remarks>
        public static T Get<T>(IScopeProvider scopeProvider, string key, Func<bool, T> ctor)
            where T : ScopeContextualBase
        {
            // no scope context = create a non-scoped object
            var scopeContext = scopeProvider.Context;
            if (scopeContext == null)
                return ctor(false);

            // create & enlist the scoped object
            var w = scopeContext.Enlist("ScopeContextualBase_" + key,
                () => ctor(true),
                (completed, item) => { item.Release(completed); });

            w._scoped = true;

            return w;
        }

        /// <inheritdoc />
        /// <remarks>
        /// <para>If not scoped, then this releases the contextual object.</para>
        /// </remarks>
        public void Dispose()
        {
            if (_scoped == false)
                Release(true);
        }

        /// <summary>
        /// Releases the contextual object.
        /// </summary>
        /// <param name="completed">A value indicating whether the scoped operation completed.</param>
        public abstract void Release(bool completed);
    }
}