Refactoring AWS level 2 data provider, pushing up common functions

wxdata/include/scwx/provider/nexrad_data_provider.hpp

@@ -0,0 +1,107 @@
+#pragma once
+
+#include <scwx/wsr88d/nexrad_file.hpp>
+
+#include <chrono>
+#include <memory>
+#include <string>
+
+namespace scwx
+{
+namespace provider
+{
+
+class NexradDataProvider
+{
+public:
+   explicit NexradDataProvider();
+   ~NexradDataProvider();
+
+   NexradDataProvider(const NexradDataProvider&) = delete;
+   NexradDataProvider& operator=(const NexradDataProvider&) = delete;
+
+   NexradDataProvider(NexradDataProvider&&) noexcept;
+   NexradDataProvider& operator=(NexradDataProvider&&) noexcept;
+
+   virtual size_t cache_size() const = 0;
+
+   /**
+    * Gets the last modified time. This is equal to the most recent object's
+    * modification time. If there are no objects, the epoch is returned.
+    *
+    * @return Last modified time
+    */
+   virtual std::chrono::system_clock::time_point last_modified() const = 0;
+
+   /**
+    * Gets the current update period. This is equal to the difference between
+    * the last two objects' modification times. If there are less than two
+    * objects, an update period of 0 is returned.
+    *
+    * @return Update period
+    */
+   virtual std::chrono::seconds update_period() const = 0;
+
+   /**
+    * Finds the most recent key in the cache, no later than the time provided.
+    *
+    * @param time Upper-bound time for the key search
+    *
+    * @return NEXRAD data key
+    */
+   virtual std::string FindKey(std::chrono::system_clock::time_point time) = 0;
+
+   /**
+    * Finds the most recent key in the cache.
+    *
+    * @return NEXRAD data key
+    */
+   virtual std::string FindLatestKey() = 0;
+
+   /**
+    * Lists NEXRAD objects for the date supplied, and adds them to the cache.
+    *
+    * @param date Date for which to list objects
+    *
+    * @return - New objects found for the given date
+    *         - Total objects found for the given date
+    */
+   virtual std::pair<size_t, size_t>
+   ListObjects(std::chrono::system_clock::time_point date) = 0;
+
+   /**
+    * Loads a NEXRAD file object by the given key.
+    *
+    * @param key NEXRAD data key
+    *
+    * @return NEXRAD data
+    */
+   virtual std::shared_ptr<wsr88d::NexradFile>
+   LoadObjectByKey(const std::string& key) = 0;
+
+   /**
+    * Lists NEXRAD objects for the current date, and adds them to the cache. If
+    * no objects have been added to the cache for the current date, the previous
+    * date is also queried for data.
+    *
+    * @return New objects found
+    */
+   virtual size_t Refresh() = 0;
+
+   /**
+    * Convert the object key to a time point.
+    *
+    * @key NEXRAD data key
+    *
+    * @return NEXRAD data time point
+    */
+   virtual std::chrono::system_clock::time_point
+   GetTimePointByKey(const std::string& key) const = 0;
+
+private:
+   class Impl;
+   std::unique_ptr<Impl> p;
+};
+
+} // namespace provider
+} // namespace scwx