lib/framework/SettingsService.h

#ifndef SettingsService_h
#define SettingsService_h

#if defined(ESP8266)
#include <ESP8266WiFi.h>
#include <ESPAsyncTCP.h>
#elif defined(ESP_PLATFORM)
#include <WiFi.h>
#include <AsyncTCP.h>
#endif

#include <SecurityManager.h>
#include <SettingsPersistence.h>
#include <ESPAsyncWebServer.h>
#include <ArduinoJson.h>
#include <AsyncJsonWebHandler.h>
#include <AsyncJson.h>
#include <AsyncJsonCallbackResponse.h>

/*
* Abstraction of a service which stores it's settings as JSON in a file system.
*/
class SettingsService : public SettingsPersistence {

  public:

    SettingsService(AsyncWebServer* server, FS* fs, char const* servicePath, char const* filePath): SettingsPersistence(fs, filePath), _servicePath(servicePath) {
      server->on(_servicePath, HTTP_GET, std::bind(&SettingsService::fetchConfig, this, std::placeholders::_1));    

      _updateHandler.setUri(servicePath);
      _updateHandler.setMethod(HTTP_POST);
      _updateHandler.setMaxContentLength(MAX_SETTINGS_SIZE);
      _updateHandler.onRequest(std::bind(&SettingsService::updateConfig, this, std::placeholders::_1, std::placeholders::_2));
      server->addHandler(&_updateHandler);     
    }

    virtual ~SettingsService() {}

    void begin() {
      // read the initial data from the file system
      readFromFS();
    }

protected:
  char const* _servicePath;
  AsyncJsonWebHandler _updateHandler;

  virtual void fetchConfig(AsyncWebServerRequest *request) {
    // handle the request
    AsyncJsonResponse * response = new AsyncJsonResponse(false, MAX_SETTINGS_SIZE);
    JsonObject jsonObject = response->getRoot();  
    writeToJsonObject(jsonObject);
    response->setLength();
    request->send(response);
  }

  virtual void updateConfig(AsyncWebServerRequest *request, JsonDocument &jsonDocument) {
    // handle the request
    if (jsonDocument.is<JsonObject>()){
      JsonObject newConfig = jsonDocument.as<JsonObject>();
      readFromJsonObject(newConfig);
      writeToFS();

      // write settings back with a callback to reconfigure the wifi
      AsyncJsonCallbackResponse * response = new AsyncJsonCallbackResponse([this] () {onConfigUpdated();}, false, MAX_SETTINGS_SIZE);
      JsonObject jsonObject = response->getRoot();   
      writeToJsonObject(jsonObject);
      response->setLength();
      request->send(response);
    } else {
      request->send(400);
    }
  }

  // implement to perform action when config has been updated
  virtual void onConfigUpdated(){}

};

#endif // end SettingsService