/// <summary>
/// Merges a collection of view models with a list of models
/// </summary>
public static void MergeCollection <TViewModel, TModel>(
this ICollection <TViewModel> collection,
IReadOnlyList <TModel> updated,
IMergeStrategy <TModel, TViewModel> strategy)
where TViewModel : IIdentifiableObject
where TModel : IIdentifiableObject
{
// Remove those without id or not existing in the updated collection
var removed = collection.Where(r => r.Id == 0 || updated.All(u => u.Id != r.Id)).ToList();
foreach (var obj in removed)
{
collection.Remove(obj);
}
foreach (var updatedModel in updated)
{
var match = collection.FirstOrDefault(r => r.Id == updatedModel.Id);
if (match != null)
{
strategy.UpdateModel(match, updatedModel);
}
else
{
var vm = strategy.FromModel(updatedModel);
collection.Add(vm);
}
}
}
/// <summary>
/// Merge a recursive model structure into an existing observable view model structure
/// </summary>
public static void MergeTree <TModel>(
this Collection <TreeItemViewModel> current,
IReadOnlyList <TModel> updated,
IMergeStrategy <TModel, TreeItemViewModel> strategy)
where TModel : class, ITreeItemModel <TModel>
{
// Use 'for'-loop, because it is modification tolerant
int currentIndex = 0, updatedIndex = 0;
while (currentIndex < current.Count || updatedIndex < updated.Count)
{
var currentItem = GetItem(current, currentIndex);
var updatedItem = GetItem(updated, updatedIndex);
// Default: Update the model if it matches
if (currentItem != null && currentItem.Id == updatedItem?.Id)
{
strategy.UpdateModel(currentItem, updatedItem);
currentIndex++;
updatedIndex++;
MergeTree(currentItem.Children, updatedItem.Children, strategy);
}
// Item was appended or inserted
else if (currentItem == null || HasId(updated, currentItem.Id, updatedIndex))
{
currentItem = strategy.FromModel(updatedItem);
current.Insert(currentIndex, currentItem);
currentIndex++;
updatedIndex++;
MergeTree(currentItem.Children, updatedItem.Children, strategy);
}
// In any other case: Remove
else
{
current.RemoveAt(currentIndex);
updatedIndex++;
}
}
}