PagedApi Test

Scenario

You are working on a project which must integrate heavily with a 3rd party API. The 3rd party have provided you with a client library to access this API, contained within the PagedApi project.

The API currently exposes the ability to retreive Foo and Bar items, which are represented by the ItemTypeId.Foo and ItemTypeId.Bar enum respectively.

Fetching items works using a statefull 'request' model. The caller must first establish a request for a particular type of item by calling int BeginPagesRequest(ItemTypeId itemTypeId), which returns a unique RequestId for the given ItemTypeId.

Items are then fetched one page at a time, by passing the RequestId to Page GetNextPage(int requestId). The size of each page is determined by the API. The returned Page object will contain the collection of items for this page, and a boolean indicating if there are more pages to follow.

Once all desired items have been retrieved, the caller should call void EndPagesRequest(int requestId), signalling to the API that it may now clean up any resources associated with the request.

Task

The IPagedApiCollection interface has been proposed by your team as a way of simplifing access to IPagedApi throughout the project. Designed to wrap IPagedApi, it contains only a single method: GetItems<>().

Complete the implementation of MyPagedApiCollection.

Considerations

Consider the following points when designing your implementation. You should attempt to address at least 2 of them.

• The API call IPagedApi.GetNextPage() may take a long time to complete. If the consumer only enumerates the first few items of the IPagedApiCollection.GetItems() response, ensure IPagedApi.GetNextPage() is called as few times as possible.
• If the consumer never enumerates the response from IPagedApiCollection.GetItems(), ensure IPagedApi.BeginPagesRequest() is not unnecessarily called.
• Once the consumer is finished with the request, ensure IPagedApi.EndPagesRequest() is called.
• You discover a quirk concerning IPagedApi.GetNextPage(), where sometimes the returned Page.Items collection can be empty. Ensure this is gracefully handled within your implementation.
• What happens when the response from IPagedApiCollection.GetItems() is enumeratad by the consumer multiple times?
• What happens when the response from IPagedApiCollection.GetItems() is enumerated after it has been disposed?