paged_response.hpp

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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
 
#pragma once
 
#include "azure/core/context.hpp"
#include "azure/core/http/raw_response.hpp"
#include "azure/core/nullable.hpp"
 
#include <cstdlib>
#include <string>
 
namespace Azure { namespace Core {
 
  template <class T> class PagedResponse {
  private:
    // The field used to check when the end of the response is reached. We default it true as the
    // starting point because all responses from a service will always come with a payload that
    // represents at least one page. The page might or might not contain elements in the page.
    // `m_hasPage` is then turned to `false` once `MoveToNextPage` is called on the last page.
    bool m_hasPage = true;
 
  protected:
    PagedResponse() = default;
 
    PagedResponse(PagedResponse&&) = default;
 
    PagedResponse& operator=(PagedResponse&&) = default;
 
  public:
    virtual ~PagedResponse() = default;
 
    std::string CurrentPageToken;
 
    Azure::Nullable<std::string> NextPageToken;
 
    std::unique_ptr<Azure::Core::Http::RawResponse> RawResponse;
 
    bool HasPage() const { return m_hasPage; }
 
    void MoveToNextPage(const Azure::Core::Context& context = Azure::Core::Context())
    {
      static_assert(
          std::is_base_of<PagedResponse, T>::value,
          "The template argument \"T\" should derive from PagedResponse<T>.");
 
      if (!NextPageToken.HasValue() || NextPageToken.Value().empty())
      {
        m_hasPage = false;
        return;
      }
 
      // Developer must make sure current page is kept unchanged if OnNextPage()
      // throws exception.
      static_cast<T*>(this)->OnNextPage(context);
    }
  };
 
}} // namespace Azure::Core