/// <summary>
/// Computes the differences between two DataModels.
/// </summary>
/// <param name="originalModel">The original model.</param>
/// <param name="newModel">The new model.</param>
/// <returns>Collection of DataModel differences</returns>
internal static ModuleCollectionChange ComputeDifferences(DataModel originalModel, DataModel newModel)
{
DataModelModuleCollection originalModules = originalModel.Modules;
DataModelModuleCollection newModules = newModel.Modules;
// All the comparisons are based on data model item Id values. It is thus important
// to make all Id properties on the data model items internal so that once an item
// is assigned an Id, that cannot change in its entire life.
// Assumption: Earlier validations ensure that all the items are present within this
// model and are not shared between data models. For example, there is no possibility
// that an association present in this data model has one of its navigation properties
// in this model but the other navigation property in some other model. Likewise, it
// should not be possible for two data models to reach the same resource type while
// enumerating the hosted types. An example source code is shown below. Here, it may
// be possible to reach 'Resource' resource type from module2 but its Parent property
// points to module1.
//var module1 = new ZentityContext().Core.Modules[0];
//var module2 = new ZentityContext().Core.Modules[0];
//module1.ResourceTypes.Add(module2.ResourceTypes["Resource"]);
ModuleCollectionChange changes = new ModuleCollectionChange();
CompareDataModelModules(changes, originalModules, newModules);
CompareResourceTypes(changes, originalModules, newModules);
CompareScalarProperties(changes, originalModules, newModules);
CompareNavigationProperties(changes, originalModules, newModules);
CompareAssociations(changes, originalModules, newModules);
return(changes);
}