#include <ArduinoJson.h>
#include <TimeLib.h>

#define JSON_DOC_ALLOC 200

const char* fieldData = "data";
const char* fieldRefreshInterval = "ri";
const char* fieldLastRefreshed = "lr";
const char* fieldDirty = "d";
const char* fieldTimestamp = "ts";

class DataManager {
  public:
    DataManager() {}

    // Add a variable to root of type int.
    // @var: the name of the variable (document)
    // @key: the key / name
    // @val: the initial value
    // @refresh_interval: the frequency, in sec, to force update the value even if value is unchanged
    void addValueInt(const String& var, const String& key, const int val, const long refresh_interval = 0) {
      JsonObject doc = root.createNestedObject(var);
      JsonObject data = doc.createNestedObject(fieldData);
      data[key] = val;
      doc[fieldRefreshInterval] = refresh_interval;
      if (refresh_interval) {
        doc[fieldLastRefreshed] = now();
      }
      doc[fieldDirty] = 1;
    }

    // Add a variable to root of type String.
    // @var: the name of the variable (document)
    // @key: the key / name
    // @val: the initial value
    // @refresh_interval: the frequency, in sec, to force update the value even if value is unchanged
    void addValueString(const String& var, const String& key, const String& val, const long refresh_interval = 0) {
      JsonObject doc = root.createNestedObject(var);
      JsonObject data = doc.createNestedObject(fieldData);
      data[key] = val;
      doc[fieldRefreshInterval] = refresh_interval;
      if (refresh_interval) {
        doc[fieldLastRefreshed] = now();
      }
      doc[fieldDirty] = 1;
    }

    // Update an int variable.
    void updateValueInt(const String& var, const String& key, const int val) {
      JsonObject doc = root[var];
      JsonObject data = doc[fieldData];
      if (data[key] != val) {
        data[key] = val;
        if (doc[fieldRefreshInterval]) {
          doc[fieldLastRefreshed] = now();
        }
        doc[fieldDirty] = 1;
      }
    }

    // Update a String variable.
    void updateValueString(const String& var, const String& key, const String& val) {
      JsonObject doc = root[var];
      JsonObject data = doc[fieldData];
      if (data[key] != val) {
        data[key] = val;
        if (doc[fieldRefreshInterval]) {
          doc[fieldLastRefreshed] = now();
        }
        doc[fieldDirty] = 1;
      }
    }

    // Get the JSON serialized representation of var.
    // @var: the name of the variable
    // @add_timestamp: add 'ts' field with current time epoch
    // @mark_flushed: clear the 'd' dirty field of the variable value
    String serializeVar(const String& var, const bool add_timestamp = false, const bool mark_flushed = false) {
      String s;
      JsonObject doc = root[var];
      if (add_timestamp) {
        JsonObject data = doc[fieldData];
        DynamicJsonDocument d(data.memoryUsage() + 8);  // Timestamp occupies 8 spaces.
        d = data;
        d[fieldTimestamp] = now();
        serializeJson(d, s);
      } else {
        serializeJson(doc[fieldData], s);
      }
      if (mark_flushed) {
        doc[fieldDirty] = 0;
      }
      return s;
    }

    // Specifies the update callback for the object.
    // @callback: a function with arguments String var, String serialData
    void setUpdateCallback(void (*callback)(const String, const String)) {
      update_callback = callback;
    }

    // Run the periodic functions of the class.
    void poll() {
      JsonObject root_ = root.as<JsonObject>();  // Iterator is only defined for JsonObject & Array.
      for (JsonPair kv : root_) {
        const String key = String(kv.key().c_str());

        JsonObject doc = root[key];
        // Check if refresh is due.
        bool update = false;
        if (doc[fieldDirty]) {
          update = true;
        } else if (doc[fieldLastRefreshed]) {
          if (now() >= (long) doc[fieldRefreshInterval] + (long) doc[fieldLastRefreshed]) {
            update = true;
            doc[fieldLastRefreshed] = now();
          }
        }
        // Run the update.
        if (update) {
          String serialData = serializeVar(key, true, true);
          if (update_callback) {
            (*update_callback)(key, serialData);
          } else {
            Serial.println("DEBUG: " + key + "=" + serialData);
          }
        }
      }
    }

  private:
    // Root document for JSON
    // Variable name is stored at the root level. Cannot start with underscore (_).
    // `data` subfield stores the actual data
    // `ri` subfield stores the refresh interval
    // `lr` subfield stores the last refresh timestamp if refresh interval is set
    // `d` subfield indicates whether the data is dirty and needs to be flushed
    DynamicJsonDocument  root = DynamicJsonDocument(200);

    // Function pointer to send update.
    void (*update_callback)(const String, const String);
};


DataManager d;

void print_callback(const String var, const String serialData) {
  Serial.println("Sending: " + var + "=" + serialData);
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  while (!Serial);

  long t = 1678528333;  // Epoch for Mar 11 3:52AM CT
  // May be optional depending on WifiNINA implementation.
  setTime(t);
  Serial.println(now());
  // Serial.println(year());
  // Serial.println(month());
  // Serial.println(day());
  // Serial.println(hour());
  // Serial.println(minute());

  // Serial.println(root.memoryUsage());


  d.setUpdateCallback(&print_callback);
  // d.addValueInt("ktc1", "temp", 1234, 0);
  d.addValueString("ktc1", "temp", "1234", 1);

  // Serial.println(root.memoryUsage());

  // serializeJson(root, Serial);
  // Serial.println();
  d.poll();
  // String data;
  // serializeJson(doc, data);
  // Serial.println(data);
  delay(2000);
  //d.updateValueInt("ktc1", "temp", 2345);
  d.updateValueString("ktc1", "temp", "2345");

  // serializeJson(root, Serial);
  // Serial.println();
  d.poll();

  delay(2000);
  // serializeJson(root, Serial);
  // Serial.println();
  // d.updateValueInt("ktc1", "temp", 2345);
  // d.updateValueInt("ktc1", "temp", 2345);
  d.updateValueString("ktc1", "temp", "2345");
  d.updateValueString("ktc1", "temp", "2345");
  d.poll();

  Serial.println("Enter loop");
}


void loop() {
  // put your main code here, to run repeatedly:

}