//---------------------------------------------------------------------
// <copyright file="LightweightEntityWrapper.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//
// @owner       [....]
// @backupOwner [....]
//---------------------------------------------------------------------
using System.Collections;
using System.Data.Objects.DataClasses;
using System.Diagnostics;
using System.Reflection;
using System.Data.Metadata.Edm;

namespace System.Data.Objects.Internal
{
    /// <summary>
    /// Implementation of IEntityWrapper for any entity that implements IEntityWithChangeTracker, IEntityWithRelationships, 
    /// and IEntityWithKey and is not a proxy.  This is a lightweight wrapper that delegates functionality to those iterfaces.
    /// This improves the speed and memory utilization for the standard code-gen cases in materialization.
    /// </summary>
    /// <typeparam name="TEntity">The type of entity wrapped</typeparam>
    internal sealed class LightweightEntityWrapper<TEntity> : BaseEntityWrapper<TEntity>
             where TEntity : IEntityWithRelationships, IEntityWithKey, IEntityWithChangeTracker
    {
        private readonly TEntity _entity;

        /// <summary>
        /// Constructs a wrapper for the given entity.
        /// Note: use EntityWrapperFactory instead of calling this constructor directly.
        /// </summary>
        /// <param name="entity">The entity to wrap</param>
        internal LightweightEntityWrapper(TEntity entity)
        : base(entity, entity.RelationshipManager)
        {
            Debug.Assert(entity is IEntityWithChangeTracker, "LightweightEntityWrapper only works with entities that implement IEntityWithChangeTracker");
            Debug.Assert(entity is IEntityWithRelationships, "LightweightEntityWrapper only works with entities that implement IEntityWithRelationships");
            Debug.Assert(entity is IEntityWithKey, "LightweightEntityWrapper only works with entities that implement IEntityWithKey");
            Debug.Assert(!EntityProxyFactory.IsProxyType(entity.GetType()), "LightweightEntityWrapper only works with entities that are not proxies");
            _entity = entity;
        }

        /// <summary>
        /// Constructs a wrapper as part of the materialization process.  This constructor is only used
        /// during materialization where it is known that the entity being wrapped is newly constructed.
        /// This means that some checks are not performed that might be needed when thw wrapper is
        /// created at other times, and information such as the identity type is passed in because
        /// it is readily available in the materializer.
        /// </summary>
        /// <param name="entity">The entity to wrap</param>
        /// <param name="key">The key for the entity</param>
        /// <param name="entitySet">The entity set, or null if none is known</param>
        /// <param name="context">The context to which the entity should be attached</param>
        /// <param name="mergeOption">NoTracking for non-tracked entities, AppendOnly otherwise</param>
        /// <param name="identityType">The type of the entity ignoring any possible proxy type</param>
        internal LightweightEntityWrapper(TEntity entity, EntityKey key, EntitySet entitySet, ObjectContext context, MergeOption mergeOption, Type identityType)
            : base(entity, entity.RelationshipManager, entitySet, context, mergeOption, identityType)
        {
            Debug.Assert(entity is IEntityWithChangeTracker, "LightweightEntityWrapper only works with entities that implement IEntityWithChangeTracker");
            Debug.Assert(entity is IEntityWithRelationships, "LightweightEntityWrapper only works with entities that implement IEntityWithRelationships");
            Debug.Assert(entity is IEntityWithKey, "LightweightEntityWrapper only works with entities that implement IEntityWithKey");
            Debug.Assert(!EntityProxyFactory.IsProxyType(entity.GetType()), "LightweightEntityWrapper only works with entities that are not proxies");
            _entity = entity;
            _entity.EntityKey = key;
        }

        // See IEntityWrapper documentation
        public override void SetChangeTracker(IEntityChangeTracker changeTracker)
        {
            _entity.SetChangeTracker(changeTracker);
        }

        // See IEntityWrapper documentation
        public override void TakeSnapshot(EntityEntry entry)
        {
        }

        // See IEntityWrapper documentation
        public override void TakeSnapshotOfRelationships(EntityEntry entry)
        {
        }

        // See IEntityWrapper documentation
        public override EntityKey EntityKey
        {
            get
            {
                return _entity.EntityKey;
            }
            set
            {
                _entity.EntityKey = value;
            }
        }

        public override bool OwnsRelationshipManager
        {
            get { return true; }
        }

        // See IEntityWrapper documentation
        public override EntityKey GetEntityKeyFromEntity()
        {
            return _entity.EntityKey;
        }

        // See IEntityWrapper documentation
        public override void CollectionAdd(RelatedEnd relatedEnd, object value)
        {
        }

        // See IEntityWrapper documentation
        public override bool CollectionRemove(RelatedEnd relatedEnd, object value)
        {
            return false;
        }
        
        // See IEntityWrapper documentation
        public override void SetNavigationPropertyValue(RelatedEnd relatedEnd, object value)
        {
        }

        // See IEntityWrapper documentation
        public override void RemoveNavigationPropertyValue(RelatedEnd relatedEnd, object value)
        {
        }

        // See IEntityWrapper documentation
        public override void EnsureCollectionNotNull(RelatedEnd relatedEnd)
        {
        }

        // See IEntityWrapper documentation
        public override object GetNavigationPropertyValue(RelatedEnd relatedEnd)
        {
            return null;
        }

        // See IEntityWrapper documentation
        public override object Entity
        {
            get { return _entity; }
        }

        // See IEntityWrapper<TEntity> documentation
        public override TEntity TypedEntity
        {
            get { return _entity; }
        }

        // See IEntityWrapper documentation
        public override void SetCurrentValue(EntityEntry entry, StateManagerMemberMetadata member, int ordinal, object target, object value)
        {
            member.SetValue(target, value);
        }

        // See IEntityWrapper documentation
        public override void UpdateCurrentValueRecord(object value, EntityEntry entry)
        {
            // No extra work to do because we know that the entity is not a proxy and has a change tracker
            entry.UpdateRecordWithoutSetModified(value, entry.CurrentValues);
        }

        // See IEntityWrapper documentation
        public override bool RequiresRelationshipChangeTracking
        {
            get { return false; }
        }
    }
}