/**
 * esp32_server.ino
 * Smart Gardening System - ESP32 Controller with MQTT Communication
 *
 * This code connects the ESP32 to Wi-Fi ("Wokwi-GUEST") and bridges telemetry
 * and control to the Web Dashboard via a public MQTT broker (broker.hivemq.com)
 * on port 1883.
 */

#include <WiFi.h>
#include <PubSubClient.h>

// Wi-Fi Credentials for Wokwi simulation
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// MQTT Broker Credentials
const char* mqtt_server = "broker.hivemq.com";
const int mqtt_port = 1883;

// Unique MQTT topics based on conversation ID to avoid collisions
const char* topic_moisture = "smart_gardening/495d5611/moisture";
const char* topic_pump_state = "smart_gardening/495d5611/pump_state";
const char* topic_pump_cmd = "smart_gardening/495d5611/pump_cmd";

// Hardware Pins
#define MOISTURE_PIN 34  // Analog Input (ADC1)
#define RELAY_PIN 26     // Digital Output for Relay

WiFiClient espClient;
PubSubClient client(espClient);

// Global state variables
int moisturePct = 0;
int pumpState = 0;
unsigned long lastReadTime = 0;
const unsigned long readInterval = 2000; // Read and publish moisture every 2 seconds

/**
 * Handles incoming MQTT messages from the Web Dashboard
 */
void mqttCallback(char* topic, byte* payload, unsigned int length) {
  String message = "";
  for (unsigned int i = 0; i < length; i++) {
    message += (char)payload[i];
  }
  
  Serial.print("[MQTT Callback] Message arrived on topic [");
  Serial.print(topic);
  Serial.print("]: ");
  Serial.println(message);

  // Check if topic matches the pump command topic
  if (String(topic) == topic_pump_cmd) {
    if (message == "1" || message == "ON") {
      pumpState = 1;
      digitalWrite(RELAY_PIN, HIGH); // Turn pump ON (Active High)
      Serial.println("[CONTROL] Pump turned ON (Relay HIGH)");
      // Publish confirmation state
      client.publish(topic_pump_state, "1", true);
    } else if (message == "0" || message == "OFF") {
      pumpState = 0;
      digitalWrite(RELAY_PIN, LOW); // Turn pump OFF (Relay LOW)
      Serial.println("[CONTROL] Pump turned OFF (Relay LOW)");
      // Publish confirmation state
      client.publish(topic_pump_state, "0", true);
    }
  }
}

/**
 * Reconnects to the MQTT broker if the connection is dropped
 */
void reconnectMQTT() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    
    // Generate a unique random MQTT client ID
    String clientId = "ESP32_SmartGardening_";
    clientId += String(random(0xffff), HEX);
    
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
      Serial.println("Connected to MQTT Broker!");
      
      // Subscribe to command topic
      client.subscribe(topic_pump_cmd);
      Serial.print("Subscribed to: ");
      Serial.println(topic_pump_cmd);
      
      // Publish current status immediately upon connection
      client.publish(topic_pump_state, pumpState ? "1" : "0", true);
    } else {
      Serial.print("Failed to connect, state=");
      Serial.print(client.state());
      Serial.println(" - Retrying in 5 seconds...");
      delay(5000);
    }
  }
}

void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);
  Serial.println("\n===========================================");
  Serial.println("ESP32 Smart Gardening Controller Starting (MQTT)");
  Serial.println("===========================================");

  // Pin Configuration
  pinMode(MOISTURE_PIN, INPUT);
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, LOW); // Default pump OFF

  // Connect to Wi-Fi
  Serial.print("Connecting to Wi-Fi SSID: ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWi-Fi Connected successfully!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  // Setup MQTT client
  client.setServer(mqtt_server, mqtt_port);
  client.setCallback(mqttCallback);
}

void loop() {
  // Ensure we are connected to the MQTT broker
  if (!client.connected()) {
    reconnectMQTT();
  }
  client.loop();

  // Periodically read sensor and publish to broker
  unsigned long currentTime = millis();
  if (currentTime - lastReadTime >= readInterval) {
    lastReadTime = currentTime;

    // Read 12-bit analog value (0 - 4095)
    int rawVal = analogRead(MOISTURE_PIN);
    
    // Map to percentage: 0 = Dry (0%), 4095 = Wet (100%)
    moisturePct = map(rawVal, 0, 4095, 0, 100);
    moisturePct = constrain(moisturePct, 0, 100);

    // Convert moisture to string and publish
    String moistureStr = String(moisturePct);
    client.publish(topic_moisture, moistureStr.c_str(), true);

    // Print local debug
    Serial.print("[STATUS] Moisture: ");
    Serial.print(moisturePct);
    Serial.print("% (Raw: ");
    Serial.print(rawVal);
    Serial.print("), Pump: ");
    Serial.println(pumpState ? "ON" : "OFF");
  }
}