Automated Plant Watering

#include <Arduino.h>
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>
#include <Preferences.h>
#include <time.h>
#include "config.h"
constexpr int SOIL_PIN=0, TRIG_PIN=6, ECHO_PIN=7, RELAY_PIN=10;
constexpr uint32_t WAIT_MS=180000, RUN_MS=5000;
Preferences prefs;
bool locked=false, pending=false;
String alert;
uint32_t lastCheck=0, lastNotify=0;
bool first=true;
void lockWater(const char *why) {
  digitalWrite(RELAY_PIN, LOW);
  if (!locked) {
    locked=true; prefs.putBool("locked",true);
    alert=why; prefs.putString("reason",alert); pending=true; prefs.putBool("pending",true);
    Serial.println(alert);
  }
}
float distanceCm() {
  float a[3];
  for(int i=0;i<3;i++) {
    digitalWrite(TRIG_PIN,LOW); delayMicroseconds(3);
    digitalWrite(TRIG_PIN,HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN,LOW);
    unsigned long us=pulseIn(ECHO_PIN,HIGH,30000);
    a[i]=us/58.0f;
    if(!us || a[i]<2 || a[i]>MAX_BUCKET_CM) return -1;
    delay(65);
  }
  if(a[0]>a[1]) {float t=a[0];a[0]=a[1];a[1]=t;}
  if(a[1]>a[2]) {float t=a[1];a[1]=a[2];a[2]=t;}
  if(a[0]>a[1]) {float t=a[0];a[0]=a[1];a[1]=t;}
  return a[1];
}
bool safeWater() {
  float cm=distanceCm(); Serial.printf("Water distance %.1f cm\n",cm);
  if(cm<0) {lockWater("Watering stopped: ultrasonic sensor reading invalid. Check sensor and bucket, then reset lock.");return false;}
  if(cm>=LOW_WATER_CM) {lockWater("Watering stopped: bucket water is low. Refill bucket, then reset lock.");return false;}
  return true;
}
void notify() {
  if(!pending || WiFi.status()!=WL_CONNECTED || !strlen(NTFY_TOKEN) || !strlen(NTFY_CA_PEM)) return;
  if(time(nullptr)<1700000000) return;
  if(lastNotify && millis()-lastNotify<60000) return;
  lastNotify=millis();
  WiFiClientSecure tls; tls.setCACert(NTFY_CA_PEM); tls.setHandshakeTimeout(5);
  HTTPClient http; http.setConnectTimeout(5000); http.setTimeout(5000);
  if(!String(NTFY_URL).startsWith("https://") || !http.begin(tls,NTFY_URL)) return;
  http.addHeader("Authorization",String("Bearer ")+NTFY_TOKEN);
  http.addHeader("Title","Plant watering stopped");
  http.addHeader("Priority","high");
  int code=http.POST(alert); http.end();
  Serial.printf("ntfy HTTP status: %d\n",code);
  if(code>=200 && code<300) {pending=false; prefs.putBool("pending",false);}
}
void setup() {
  digitalWrite(RELAY_PIN,LOW); pinMode(RELAY_PIN,OUTPUT);
  pinMode(TRIG_PIN,OUTPUT); digitalWrite(TRIG_PIN,LOW); pinMode(ECHO_PIN,INPUT);
  Serial.begin(115200); analogReadResolution(12); analogSetPinAttenuation(SOIL_PIN,ADC_11db);
  prefs.begin("watering",false); locked=prefs.getBool("locked",false);
  pending=prefs.getBool("pending",false); alert=prefs.getString("reason","Watering locked. Inspect bucket and sensor.");
  WiFi.setAutoReconnect(true);
  if(strlen(WIFI_SSID)) {WiFi.begin(WIFI_SSID,WIFI_PASSWORD);configTime(0,0,"pool.ntp.org","time.nist.gov");}
  Serial.println("Pump defaults OFF. Send R over serial after refill/repair to clear safety lock. Calibration must be enabled in config.h.");
  // Full soak delay on every boot prevents rapid watering after power interruptions.
  lastCheck=millis();
}
void loop() {
  if(Serial.available() && Serial.read()=='R') {
    if(CALIBRATED && safeWater()) {locked=false;pending=false;prefs.putBool("locked",false);prefs.putBool("pending",false);lastCheck=millis();Serial.println("Lock cleared; waiting 180 seconds.");}
  }
  // All network operations happen with pump OFF.
  notify();
  if(millis()-lastCheck<WAIT_MS) {delay(10);return;}
  lastCheck=millis();
  long mv=0;for(int i=0;i<16;i++){mv+=analogReadMilliVolts(SOIL_PIN);delay(3);}mv/=16;
  Serial.printf("Soil: %ld mV\n",mv);
  if(!CALIBRATED) {Serial.println("Calibration required; pump disabled.");return;}
  if(locked) return;
  if(SOIL_DRY_MV<=SOIL_WET_MV || mv<100 || mv>3200) {lockWater("Watering stopped: check soil probe connection or calibration.");return;}
  if(!safeWater()) return;
  int moisture=constrain((SOIL_DRY_MV-mv)*100/(SOIL_DRY_MV-SOIL_WET_MV),0L,100L);
  Serial.printf("Moisture: %d percent\n",moisture);
  if(moisture<DRY_BELOW_PERCENT) {
    digitalWrite(RELAY_PIN,HIGH); // NPN pulls active-low relay input down.
    delay(RUN_MS); // No networking or measurements can extend this run.
    digitalWrite(RELAY_PIN,LOW);
    lastCheck=millis(); // At least 180 seconds from pump OFF before soil recheck.
  }
}