initial commit

lib/framework/FSPersistence.h

@@ -0,0 +1,98 @@
+#ifndef FSPersistence_h
+#define FSPersistence_h
+
+#include <StatefulService.h>
+#include <FS.h>
+
+template <class T>
+class FSPersistence {
+  public:
+    FSPersistence(JsonStateReader<T>   stateReader,
+                  JsonStateUpdater<T>  stateUpdater,
+                  StatefulService<T> * statefulService,
+                  FS *                 fs,
+                  char const *         filePath,
+                  size_t               bufferSize = DEFAULT_BUFFER_SIZE)
+        : _stateReader(stateReader)
+        , _stateUpdater(stateUpdater)
+        , _statefulService(statefulService)
+        , _fs(fs)
+        , _filePath(filePath)
+        , _bufferSize(bufferSize)
+        , _updateHandlerId(0) {
+        enableUpdateHandler();
+    }
+
+    void readFromFS() {
+        File settingsFile = _fs->open(_filePath, "r");
+
+        if (settingsFile) {
+            DynamicJsonDocument  jsonDocument = DynamicJsonDocument(_bufferSize);
+            DeserializationError error        = deserializeJson(jsonDocument, settingsFile);
+            if (error == DeserializationError::Ok && jsonDocument.is<JsonObject>()) {
+                JsonObject jsonObject = jsonDocument.as<JsonObject>();
+                _statefulService->updateWithoutPropagation(jsonObject, _stateUpdater);
+                settingsFile.close();
+                return;
+            }
+            settingsFile.close();
+        }
+        // If we reach here we have not been successful in loading the config,
+        // hard-coded emergency defaults are now applied.
+
+        applyDefaults();
+    }
+
+    bool writeToFS() {
+        // create and populate a new json object
+        DynamicJsonDocument jsonDocument = DynamicJsonDocument(_bufferSize);
+        JsonObject          jsonObject   = jsonDocument.to<JsonObject>();
+        _statefulService->read(jsonObject, _stateReader);
+
+        // serialize it to filesystem
+        File settingsFile = _fs->open(_filePath, "w");
+
+        // failed to open file, return false
+        if (!settingsFile) {
+            return false;
+        }
+
+        // serialize the data to the file
+        serializeJson(jsonDocument, settingsFile);
+        settingsFile.close();
+        return true;
+    }
+
+    void disableUpdateHandler() {
+        if (_updateHandlerId) {
+            _statefulService->removeUpdateHandler(_updateHandlerId);
+            _updateHandlerId = 0;
+        }
+    }
+
+    void enableUpdateHandler() {
+        if (!_updateHandlerId) {
+            _updateHandlerId = _statefulService->addUpdateHandler([&](const String & originId) { writeToFS(); });
+        }
+    }
+
+  private:
+    JsonStateReader<T>   _stateReader;
+    JsonStateUpdater<T>  _stateUpdater;
+    StatefulService<T> * _statefulService;
+    FS *                 _fs;
+    char const *         _filePath;
+    size_t               _bufferSize;
+    update_handler_id_t  _updateHandlerId;
+
+  protected:
+    // We assume the updater supplies sensible defaults if an empty object
+    // is supplied, this virtual function allows that to be changed.
+    virtual void applyDefaults() {
+        DynamicJsonDocument jsonDocument = DynamicJsonDocument(_bufferSize);
+        JsonObject          jsonObject   = jsonDocument.as<JsonObject>();
+        _statefulService->updateWithoutPropagation(jsonObject, _stateUpdater);
+    }
+};
+
+#endif // end FSPersistence