// IoT-based Heart Rate Monitoring System for ThingSpeak
// Adapted from the soil moisture irrigation system
// ThingSpeak channel: https://thingspeak.com/channels/3034579

#include <WiFi.h>
#include "ThingSpeak.h"

const int PULSE_PIN = 34;
const int ALERT_PIN = 19;

int BPM_THRESHOLD_LOW = 60;            // Set low BPM threshold for alert
int BPM_THRESHOLD_HIGH = 100;          // Set high BPM threshold for alert
bool ALERT_STATUS = false;

char* WIFI_NAME = "Wokwi-GUEST";
char* WIFI_PASSWORD = "";
int myChannelNumber = 3034579;         // ThingSpeak channel ID
char* myApiKey = "RMLHD5UVCICTEO83";   // ThingSpeak write API key
WiFiClient client;

void setup() 
{
  Serial.begin(115200);
  WiFi.begin(WIFI_NAME, WIFI_PASSWORD);
  Serial.println("Connecting...");
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  
  Serial.println("Wi-Fi connected");
  Serial.println("Local IP: " + String(WiFi.localIP()));
  Serial.println("-------------");
  WiFi.mode(WIFI_STA);
  ThingSpeak.begin(client);

  pinMode(ALERT_PIN, OUTPUT);
}

void loop()
{
  // Sample for 10 seconds to calculate BPM
  unsigned long startTime = millis();
  int beatCount = 0;
  int threshold = 2457;  // Threshold for detecting rising edge (adjusted for signal range ~0.2-0.8 -> analog 819-3276)
  int previous = analogRead(PULSE_PIN);
  
  while (millis() - startTime < 10000) {
    int current = analogRead(PULSE_PIN);
    if (current > threshold && previous <= threshold) {
      beatCount++;
    }
    previous = current;
    delay(2);  // Sample every 2ms
  }
  
  int bpm = beatCount * 6;  // Since 10 seconds, multiply by 6 for BPM

  // Alert threshold check
  if (bpm < BPM_THRESHOLD_LOW || bpm > BPM_THRESHOLD_HIGH) {
    ALERT_STATUS = true;
    digitalWrite(ALERT_PIN, HIGH); // Turn on alert LED
  } else {
    ALERT_STATUS = false;
    digitalWrite(ALERT_PIN, LOW); // Turn off alert LED
  }

  // Print status
  Serial.print("BPM: ");
  Serial.print(bpm);
  Serial.println("");

  Serial.print("Alert: ");
  Serial.println(ALERT_STATUS ? "on" : "off");

  // Send data to ThingSpeak
  ThingSpeak.setField(1, bpm);
  ThingSpeak.setField(2, ALERT_STATUS);

  int x = ThingSpeak.writeFields(myChannelNumber, myApiKey);
  if (x == 200) {
    Serial.println("Data sent to ThingSpeak successfully");
  } else {
    Serial.println("Error sending data to ThingSpeak: " + String(x));
  }

  Serial.println("-------------");

  delay(5000); // Wait 5 seconds before next measurement (total cycle ~15s)
}