#include <Arduino.h>

#define TRIG_PIN 17
#define ECHO_PIN 16

#define LED_PIN 27 // Define the pin for the LED

// Define the threshold distance for occupancy
#define OCCUPIED_THRESHOLD 130 // in centimeters

// Variables for logging
unsigned long startTime, endTime, startTimeLed, endTimeLed, LEDSignalTime, transmissionTime, detectionTime;

void setup() {
  Serial.begin(115200);
  
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  
  pinMode(LED_PIN, OUTPUT); // Initialize the LED pin
  digitalWrite(LED_PIN, LOW); // Turn off the LED initially
}

long readDistance(uint8_t trigPin, uint8_t echoPin, unsigned long &detectionTime) {
  long duration, distance;
  
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  startTime = micros();
  duration = pulseIn(echoPin, HIGH);
  endTime = micros();
  
  detectionTime = endTime - startTime;
  distance = (duration / 2) / 29.1;
  
  return distance;
}

void reportOccupancy(long distance) {
  if (distance < OCCUPIED_THRESHOLD) {
    Serial.println("Parking Spot: Occupied");
  } else {
    Serial.println("Parking Spot: Available");
  }
}

void updateLED(bool isOccupied) {
  if (isOccupied) {
    digitalWrite(LED_PIN, HIGH);  // Turn LED on if the spot is occupied
  } else {
    digitalWrite(LED_PIN, LOW);   // Turn LED off if the spot is available
  }
}

void loop() {
  long distance = readDistance(TRIG_PIN, ECHO_PIN, detectionTime);

  bool isOccupied = distance < OCCUPIED_THRESHOLD;

  startTime = micros(); // Start logging transmission time just before processing
  
  reportOccupancy(distance);

  startTimeLed = micros();
  updateLED(isOccupied);
  endTimeLed = micros();

  endTime = micros(); // Stop logging transmission time just after processing
  transmissionTime = endTime - startTime;
  LEDSignalTime = endTimeLed - startTimeLed;
  //NOTE: Time is in microseconds!

  // Log the metrics
  Serial.println("----------------");
  Serial.print("Transmission Time (us): ");
  Serial.println(transmissionTime);
  Serial.print("Detection Time (us): ");
  Serial.println(detectionTime);
  Serial.print("LED Signal Time (us): ");
  Serial.println(LEDSignalTime);
  Serial.println("========================");
  
  delay(5000);
}