#if defined(ESP32)
  #include <WiFi.h>
#elif defined(ESP8266)
  #include <ESP8266WiFi.h>
#endif

#include <ESP_Mail_Client.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Fonts/FreeSansBold18pt7b.h>
#include <DHT.h>

// --- Pin Definitions ---
#define I2C_SDA          21
#define I2C_SCL          22
#define FLAME_SENSOR_PIN 15
#define GAS_SENSOR_PIN   2
#define DHT_PIN          12
#define DHT_TYPE         DHT22

// --- OLED Configuration ---
#define SCREEN_WIDTH     128
#define SCREEN_HEIGHT    64
#define OLED_RESET       -1
#define OLED_ADDRESS     0x3C 

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
DHT dht(DHT_PIN, DHT_TYPE);

// --- Network & Mail Configuration ---
#define WIFI_SSID        "Wokwi-GUEST"
#define WIFI_PASSWORD    ""

#define SMTP_HOST        "smtp.gmail.com"
#define SMTP_PORT        465

#define AUTHOR_EMAIL     "[email protected]"
#define AUTHOR_PASSWORD  "viom mfli mpkm fwol"
#define RECIPIENT_EMAIL  "[email protected]"

SMTPSession smtp;

// --- Timing Variables ---
unsigned long lastDisplayUpdate = 0;
const unsigned long displayInterval = 2000; 

unsigned long lastEmailSent = 0;
const unsigned long emailCooldown = 60000; // 60s cooldown between emails

bool displayToggle = false;

// Function Prototypes
void smtpCallback(SMTP_Status status);
void send_mail(float temp, float hum, int flame, int gas);
void updateDisplay(float temp, float hum, int flame, int gas);
void showSendingEmailScreen();
void showAlarmScreen(float temp, float hum, int flame, int gas);

void setup() {
  Serial.begin(115200);
  
  Wire.begin(I2C_SDA, I2C_SCL);

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 10);
  display.println(F("System Initializing..."));
  display.display();

  dht.begin();
  pinMode(FLAME_SENSOR_PIN, INPUT_PULLUP);
  pinMode(GAS_SENSOR_PIN, INPUT_PULLUP);

  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(300);
  }
  Serial.println("\nConnected with IP: " + WiFi.localIP().toString());

  display.clearDisplay();
  display.setCursor(0, 10);
  display.println(F("WiFi Connected!"));
  display.display();
  delay(1000);
}

void loop() {
  int flameValue = digitalRead(FLAME_SENSOR_PIN);
  int gasValue = digitalRead(GAS_SENSOR_PIN);
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  if (isnan(humidity) || isnan(temperature)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

  // Active Low for Flame/Gas Digital Outputs
  bool isAlarm = (temperature > 40.0) || (flameValue == LOW) || (gasValue == LOW);

  if (isAlarm) {
    // 1. Immediately show continuous alarm display on screen
    showAlarmScreen(temperature, humidity, flameValue, gasValue);

    // 2. Check email cooldown window
    if (millis() - lastEmailSent > emailCooldown) {
      Serial.println("Alarm condition detected! Sending email...");
      
      // Update OLED to notify user that email transmission is taking place
      showSendingEmailScreen();
      
      send_mail(temperature, humidity, flameValue, gasValue);
      lastEmailSent = millis();
    }
  } else {
    // Normal operation: Rotate page views periodically
    if (millis() - lastDisplayUpdate >= displayInterval) {
      lastDisplayUpdate = millis();
      displayToggle = !displayToggle;
      updateDisplay(temperature, humidity, flameValue, gasValue);
    }
  }
}

void showSendingEmailScreen() {
  display.clearDisplay();
  display.setFont();
  display.setTextColor(SSD1306_WHITE);
  
  // Header Box
  display.fillRect(0, 0, 128, 16, SSD1306_WHITE);
  display.setTextColor(SSD1306_BLACK);
  display.setTextSize(1);
  display.setCursor(12, 4);
  display.print(F("CRITICAL ALARM!"));

  // Body status
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(10, 30);
  display.print(F("Sending Alert Email"));
  display.setCursor(20, 48);
  display.print(F("Please Wait..."));

  display.display();
}

void showAlarmScreen(float temp, float hum, int flame, int gas) {
  display.clearDisplay();
  display.setFont();
  
  // Inverted header bar for immediate visual distinction
  display.fillRect(0, 0, 128, 16, SSD1306_WHITE);
  display.setTextColor(SSD1306_BLACK);
  display.setTextSize(1);
  display.setCursor(20, 4);
  display.print(F("** ALARM ACTIVE **"));

  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 22);
  display.printf("Temp : %.1f C %s\n", temp, (temp > 40.0) ? "[OVER]" : "");

  display.setCursor(0, 36);
  display.printf("Flame: %s\n", (flame == LOW) ? "TRIPPED!" : "OK");

  display.setCursor(0, 50);
  display.printf("Gas  : %s\n", (gas == LOW) ? "TRIPPED!" : "OK");

  display.display();
}

void updateDisplay(float temp, float hum, int flame, int gas) {
  display.clearDisplay();

  if (displayToggle) {
    // Page 1: Big Temperature Display
    display.setFont(); 
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.print(F("TEMPERATURE"));

    display.setFont(&FreeSansBold18pt7b);
    display.setCursor(5, 42);
    display.printf("%.1f", temp);
    
    display.setFont();
    display.setTextSize(1);
    display.setCursor(95, 20);
    display.print((char)247);
    display.print("C");

    display.setCursor(0, 54);
    display.printf("Humidity: %.1f%%", hum);
  } else {
    // Page 2: System Overview
    display.setFont(); 
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    
    display.setCursor(0, 0);
    display.println(F("--- SENSOR STATUS ---"));
    
    display.setCursor(0, 18);
    display.printf("Flame Sensor : %s\n", (flame == LOW) ? "ALARM!" : "OK");
    
    display.setCursor(0, 32);
    display.printf("Gas Sensor   : %s\n", (gas == LOW) ? "ALARM!" : "OK");

    display.setCursor(0, 48);
    display.printf("System Temp  : %.1f C", temp);
  }

  display.display();
}

void smtpCallback(SMTP_Status status) {
  Serial.println(status.info());

  if (status.success()) {
    Serial.println("----------------");
    ESP_MAIL_PRINTF("Message sent success: %d\n", status.completedCount());
    ESP_MAIL_PRINTF("Message sent failed: %d\n", status.failedCount());
    Serial.println("----------------\n");

    for (size_t i = 0; i < smtp.sendingResult.size(); i++) {
      SMTP_Result result = smtp.sendingResult.getItem(i);
      ESP_MAIL_PRINTF("Message No: %d\n", i + 1);
      ESP_MAIL_PRINTF("Status: %s\n", result.completed ? "success" : "failed");
      ESP_MAIL_PRINTF("Date/Time: %s\n", MailClient.Time.getDateTimeString(result.timestamp, "%B %d, %Y %H:%M:%S").c_str());
    }
    smtp.sendingResult.clear();
  }
}

void send_mail(float temp, float hum, int flame, int gas) {
  MailClient.networkReconnect(true);
  smtp.debug(0);
  smtp.callback(smtpCallback);

  Session_Config config;
  config.server.host_name = SMTP_HOST;
  config.server.port = SMTP_PORT;
  config.login.email = AUTHOR_EMAIL;
  config.login.password = AUTHOR_PASSWORD;
  config.login.user_domain = "";

  config.time.ntp_server = F("pool.ntp.org,time.nist.gov");
  config.time.gmt_offset = 3;
  config.time.day_light_offset = 0;

  SMTP_Message message;
  message.sender.name = F("ESP32 Safety System");
  message.sender.email = AUTHOR_EMAIL;
  message.subject = F("CRITICAL ALARM: Hazard Detected!");
  message.addRecipient(F("Recipient"), RECIPIENT_EMAIL);

  String textMsg = "CRITICAL ALARM DETECTED!\n\n";
  textMsg += "Temperature: " + String(temp, 1) + " C\n";
  textMsg += "Humidity: " + String(hum, 1) + " %\n";
  textMsg += "Flame Status: " + String((flame == LOW) ? "FIRE DETECTED" : "Normal") + "\n";
  textMsg += "Gas Status: " + String((gas == LOW) ? "GAS LEAK DETECTED" : "Normal") + "\n";

  message.text.content = textMsg.c_str();
  message.text.charSet = "us-ascii";
  message.text.transfer_encoding = Content_Transfer_Encoding::enc_7bit;
  
  message.priority = esp_mail_smtp_priority::esp_mail_smtp_priority_high;

  if (!smtp.connect(&config)) {
    ESP_MAIL_PRINTF("Connection error, Status Code: %d, Error Code: %d, Reason: %s\n", smtp.statusCode(), smtp.errorCode(), smtp.errorReason().c_str());
    return;
  }

  if (!MailClient.sendMail(&smtp, &message)) {
    ESP_MAIL_PRINTF("Error sending Email, Status Code: %d, Error Code: %d, Reason: %s\n", smtp.statusCode(), smtp.errorCode(), smtp.errorReason().c_str());
  }
}