using System;
using System.Collections.Generic;
using LinFu.Reflection;

namespace LinFu.AOP.Interfaces
{
    /// <summary>
    ///     Represents a registry class that bootstraps components into memory when the application starts.
    /// </summary>
    public sealed class BootStrapRegistry
    {
        private readonly IList<IBootStrappedComponent> _components = new List<IBootStrappedComponent>();

        private BootStrapRegistry()
        {
            Initialize();
        }

        /// <summary>
        ///     Gets the value indicating the BootStrapRegistry instance.
        /// </summary>
        public static BootStrapRegistry Instance => NestedLoader.Instance;

        /// <summary>
        ///     Initializes the BootStrapRegistry.
        /// </summary>
        private void Initialize()
        {
            lock (_components)
            {
                _components.LoadFrom(AppDomain.CurrentDomain.BaseDirectory, "*.dll");
                foreach (var component in _components)
                    try
                    {
                        component.Initialize();
                    }
                    catch (Exception ex)
                    {
                        var componentName = component != null ? component.GetType().Name : "(unknown)";
                        var message = string.Format("{0} Error: Unable to load component '{1}' - {2}",
                            GetType().FullName,
                            componentName, ex);

                        throw new BootstrapException(message, ex);
                    }
            }
        }

        /// <summary>
        ///     Returns the list of components that have been initialized by the bootstrapper.
        /// </summary>
        /// <returns></returns>
        public IEnumerable<IBootStrappedComponent> GetComponents()
        {
            return _components;
        }


        private class NestedLoader
        {
            internal static readonly BootStrapRegistry Instance;

            // Explicit static constructor to tell C# compiler
            // not to mark type as beforefieldinit
            static NestedLoader()
            {
                Instance = new BootStrapRegistry();
            }
        }
    }
}