#include <WiFi.h>
#include <esp_now.h>

//we have this value to multipy to our time to sleep 
//as the esp lib be using time as uS 
#define uS_TO_S_FACTOR 1000000

// The leader's STUDENT CODE IS 10947943.
// So that the time to sleep would be 48s
#define TIME_TO_SLEEP  48 //Sleep for 48 seconds


RTC_DATA_ATTR int bootCount = 0;

//The ultrasonic physical pins connecting to esp phisical pins
const int trigPin = 5;
const int echoPin = 18;

//define sound speed in cm/uS
#define SOUND_SPEED 0.034

//These are variables that we will be using for
// measuring distance with ultrasonic
long duration;
float distance;

// MAC receiver
uint8_t broadcastAddress[] = {0x8C, 0xAA, 0xB5, 0x84, 0xFB, 0x90};
esp_now_peer_info_t peerInfo;

// Defining function for each part of the code

void Deep_sleep(){
 //this function will set the time to sleep and
 // also turn the esp in deep sleep mode
 
  Serial.println("Going to sleep now");
  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);
  Serial.println("ESP32 sleep every " + String(TIME_TO_SLEEP) + "seconds");

  Serial.flush(); 
  esp_deep_sleep_start();
}

void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
 //Checking if the sink node is sending data 
  Serial.print("Send Status: ");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Ok" : "Error");
}


void OnDataRecv(const uint8_t * mac, const uint8_t *data, int len) {
  //in this function the message from sink node
  // is recievied by the main esp and then it will be printed
  Serial.print("Message received: ");
  char receivedString[len];
  memcpy(receivedString, data, len);
  Serial.println(String(receivedString));
}

int ultra_function () {
//this function is calculating and returning the distance using ultrasonic
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  
  // Calculate the distance
  distance = duration * SOUND_SPEED/2;
  delay(1000);
  return distance;
}


void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200); // Starts the serial communication

  //ultra setup

  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT); // Sets the echoPin as an Input


  //2 esp talking setup

  WiFi.mode(WIFI_STA);
  esp_now_init();
  //send callback
  esp_now_register_send_cb(OnDataSent);
  //receive callback
  esp_now_register_recv_cb(OnDataRecv);
  // Peer Registration
  memcpy(peerInfo.peer_addr, broadcastAddress, 6);
  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
  esp_now_add_peer(&peerInfo);
 

}

void loop() {
 //In our main loop firstly, we call the ultrasonic function
 // to get the distance value
  
ultra_function();
delay(10); // this speeds up the simulation

//Then, we check the distance value. 
//If it is more than 50cm, it means that our parking space is not occupied
//so, the message that has to be sent to the main esp is "FREE" and 
//after that we call the deep sleep function and
// the sink esp will be go in sleep mode for 48s
//the 1ms delay is for esp to process the ultra sonic function and if function.
//if we dont put it here, the esp will not be able to function 
//as it goes to deep sleep mode immediately

if(distance> 50){
  String message = "FREE";
  esp_now_send(broadcastAddress, (uint8_t*)message.c_str(), message.length() + 1);
  delay(1);
  Deep_sleep();
  
}

//If the distance is less than or egual to 50, 
//it means that the parking space is occupied
//the rest is the same as above.
else {
  String message = "OCCUPIED";
  esp_now_send(broadcastAddress, (uint8_t*)message.c_str(), message.length() + 1);
  delay(1);
  Deep_sleep();
}

}