// /* ============================================================================
// Copyright 2014 Hewlett Packard
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ============================================================================ */

namespace Openstack.Common.ServiceLocation
{
    using System;
    using System.Globalization;

    /// <inheritdoc/>
    internal abstract class ServiceLocationManager : IServiceLocationManager
    {
        /// <inheritdoc/>
        public void RegisterServiceInstance<TService>(TService instance)
        {
            this.RegisterServiceInstance(typeof(TService),
                                  instance);
        }

        /// <inheritdoc/>
        public abstract void RegisterServiceInstance(Type type, object instance);

        /// <inheritdoc/>
        public void RegisterServiceType<T>(Type registrationValue)
        {
            this.RegisterServiceType(typeof(T),
                              registrationValue);
        }

        /// <inheritdoc/>
        public void RegisterServiceType<TInterface, TConcreate>() where TConcreate : class, TInterface
        {
            this.RegisterServiceType(typeof(TInterface), typeof(TConcreate));
        }

        /// <inheritdoc/>
        public void RegisterServiceType(Type type, Type registrationValue)
        {
            ThrowIfInvalidRegistration(type, registrationValue);
            
            var obj = Activator.CreateInstance(registrationValue);
            
            this.RegisterServiceInstance(type, obj);
        }

        /// <summary>
        /// Throws an exception if the type or implementation are null.
        /// </summary>
        /// <param name="type">A Type object.</param>
        /// <param name="implementation">The implementation of the given Type.</param>
        internal static void ThrowIfNullInstance(Type type, object implementation)
        {
            if (ReferenceEquals(type, null))
            {
                var msg = string.Format(CultureInfo.InvariantCulture,
                                           "Cannot register a null service.");
                throw new InvalidOperationException(msg);
            }

            if (ReferenceEquals(implementation, null))
            {
                var msg = string.Format(
                    CultureInfo.InvariantCulture,
                    "A service cannot have a null implementation '{0}'",
                    type.FullName);
                throw new InvalidOperationException(msg);
            }
        }

        /// <summary>
        /// Throws an exception if the given Type and implementation represent an invalid registration. 
        /// An invalid registration is one where the given Type is of a restricted type, is not an interface, or the given implementation does not inherit from the given Type.
        /// </summary>
        /// <param name="type">A Type object.</param>
        /// <param name="implementation">The implementation of the given Type.</param>
        internal static void ThrowIfInvalidRegistration(Type type, Type implementation)
        {
            ThrowIfNullInstance(type,
                                implementation);
            if (type == typeof(IServiceLocationRuntimeManager) || 
                type == typeof(IServiceLocationOverrideManager) || 
                type == typeof(IServiceLocationManager) || 
                type == typeof(IServiceLocator))
            {
                var msg = string.Format(
                    CultureInfo.InvariantCulture,
                    "Service location services cannot be registered or overriden: '{0}'",
                    type.FullName);
                throw new InvalidOperationException(msg);
            }
            if (!type.IsInterface)
            {
                var msg = string.Format(
                    CultureInfo.InvariantCulture,
                    "The following type: '{0}' is not an interface",
                    type.FullName);
                throw new InvalidOperationException(msg);
            }
            if (!type.IsAssignableFrom(implementation))
            {
                var msg = string.Format(
                    CultureInfo.InvariantCulture,
                    "Cannot register or ovverride the service '{0}' for the type '{1}' which is not derived from the service",
                    implementation.FullName,
                    type.FullName);
                throw new InvalidOperationException(msg);
            }
        }
    }
}