Code to run the APIs

server_utils.h

#include "memory_utils.h"
#include <ArduinoJson.h>

StaticJsonDocument<250> responseJson;
char buffer[250];

void createJson(String message) {
  responseJson.clear();
  responseJson["message"] = message;
  serializeJson(responseJson, buffer);
}

void getServerMessage(){
  Serial.println("Getting message");
  String message = readMessage("");
  createJson(message);
  server.send(200, "application/json", buffer);
}

void updateServerMessage(){
  Serial.println("Updating message");
  if (server.hasArg("plain") == false) {
    Serial.println("Wrong json body!");
    server.send(400, "application/json", "{}");
  }
  String body = server.arg("plain");
  deserializeJson(responseJson, body);
  if(!responseJson.containsKey("message")){
    Serial.println("Wrong json body! Missing message field.");
    server.send(400, "application/json", "Request missing message key.");
    return;
  }
  else{
    if(updateMessage(responseJson["message"])){
      Serial.println("Setting message");
      server.send(200, "application/json", "{}");
    }
    else{
      Serial.println("Last read message is the same, not updating it in memory");
      server.send(200, "application/json", "Last read message is the same, not updating it in memory.");
    }
  }
}

void setupRouting() {
  //Sets a server routing so that each endpoint is assigned to an handler
  // Message
  server.on("/message", getServerMessage);
  server.on("/message/set", HTTP_POST, updateServerMessage);
  // start server
  server.begin();
}