WordClockESP/src/SettingsPersistence.h

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#ifndef SettingsPersistence_h
#define SettingsPersistence_h
#include <ESPAsyncWebServer.h>
#include <FS.h>
#include <ArduinoJson.h>
#include <AsyncJsonRequestWebHandler.h>
#include <AsyncArduinoJson6.h>
/**
* At the moment, not expecting settings service to have to deal with large JSON
* files this could be made configurable fairly simply, it's exposed on
* AsyncJsonRequestWebHandler with a setter.
*/
#define MAX_SETTINGS_SIZE 1024
/*
* Mixin for classes which need to save settings to/from a file on the the file system as JSON.
*/
class SettingsPersistence {
protected:
// will store and retrieve config from the file system
FS* _fs;
// the file path our settings will be saved to
char const* _filePath;
bool writeToFS() {
// create and populate a new json object
DynamicJsonDocument jsonDocument = DynamicJsonDocument(MAX_SETTINGS_SIZE);
JsonObject root = jsonDocument.to<JsonObject>();
writeToJsonObject(root);
// serialize it to filesystem
File configFile = _fs->open(_filePath, "w");
// failed to open file, return false
if (!configFile) {
return false;
}
serializeJson(jsonDocument, configFile);
configFile.close();
return true;
}
void readFromFS(){
File configFile = _fs->open(_filePath, "r");
// use defaults if no config found
if (configFile) {
// Protect against bad data uploaded to file system
// We never expect the config file to get very large, so cap it.
size_t size = configFile.size();
if (size <= MAX_SETTINGS_SIZE) {
DynamicJsonDocument jsonDocument = DynamicJsonDocument(MAX_SETTINGS_SIZE);
DeserializationError error = deserializeJson(jsonDocument, configFile);
if (error == DeserializationError::Ok && jsonDocument.is<JsonObject>()){
JsonObject root = jsonDocument.as<JsonObject>();
readFromJsonObject(root);
configFile.close();
return;
}
}
configFile.close();
}
// If we reach here we have not been successful in loading the config,
// hard-coded emergency defaults are now applied.
applyDefaultConfig();
}
// serialization routene, from local config to JsonObject
virtual void readFromJsonObject(JsonObject& root){}
virtual void writeToJsonObject(JsonObject& root){}
// We assume the readFromJsonObject supplies sensible defaults if an empty object
// is supplied, this virtual function allows that to be changed.
virtual void applyDefaultConfig(){
DynamicJsonDocument jsonDocument = DynamicJsonDocument(MAX_SETTINGS_SIZE);
JsonObject root = jsonDocument.to<JsonObject>();
readFromJsonObject(root);
}
public:
SettingsPersistence(FS* fs, char const* servicePath, char const* filePath):
_fs(fs), _filePath(filePath) {}
virtual ~SettingsPersistence() {}
};
#endif // end SettingsPersistence