#include <WiFi.h>
#include <HTTPClient.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ==================================================
// WiFi Configuration
// ==================================================

String wifiSsid = "Wokwi-GUEST";
String wifiPassword = "";


// ==================================================
// API Configuration
// ==================================================

String attendanceUrl =
  "https://prathammardhekar.pythonanywhere.com/api/v1/iot/attendance?device=device01-lab&fp=1&token=zpMqrlsmT5gsQaByloKCgIHCZGkWLIxz";

String heartbeatUrl =
  "https://prathammardhekar.pythonanywhere.com/api/v1/iot/heartbeat?device=device01-lab&token=zpMqrlsmT5gsQaByloKCgIHCZGkWLIxz";


// ==================================================
// Pin Configuration
// ==================================================

const int blinkLedPin = 18;
const int greenLedPin = 4;
const int pushButtonPin = 5;


// ==================================================
// LCD Configuration
// ==================================================

const int lcdAddress = 0x27;
const int lcdColumns = 16;
const int lcdRows = 2;

LiquidCrystal_I2C lcd(
  lcdAddress,
  lcdColumns,
  lcdRows
);


// ==================================================
// Display BioTrack
// ==================================================

/**
 * Displays the default BioTrack ready screen.
 */
void displayBioTrack() {

  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("BioTrack");

  lcd.setCursor(0, 1);
  lcd.print("Ready...");
}


// ==================================================
// Display Fingerprint Triggered
// ==================================================

/**
 * Displays fingerprint trigger status.
 */
void displayFingerprintTriggered() {

  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("Fingerprint");

  lcd.setCursor(0, 1);
  lcd.print("Triggered!");
}


// ==================================================
// Extract JSON String Value
// ==================================================

/**
 * Extracts a simple string value from JSON.
 */
String extractJsonValue(String response, String key) {

  String searchKey = "\"" + key + "\":\"";

  int startPosition = response.indexOf(searchKey);

  if (startPosition < 0) {
    return "N/A";
  }

  startPosition += searchKey.length();

  int endPosition = response.indexOf(
    "\"",
    startPosition
  );

  if (endPosition < 0) {
    return "N/A";
  }

  return response.substring(
    startPosition,
    endPosition
  );
}


// ==================================================
// WiFi Connection
// ==================================================

/**
 * Connects the ESP32 to the configured WiFi network.
 */
void connectToWiFi() {

  Serial.println();
  Serial.println("Connecting to WiFi...");

  WiFi.begin(
    wifiSsid,
    wifiPassword
  );

  int retryCount = 0;

  while (
    WiFi.status() != WL_CONNECTED &&
    retryCount < 30
  ) {

    delay(500);

    Serial.print(".");

    retryCount++;
  }

  Serial.println();

  if (WiFi.status() == WL_CONNECTED) {

    Serial.println("WiFi connected");

    Serial.print("IP address: ");
    Serial.println(WiFi.localIP());

  } else {

    Serial.println("WiFi connection failed");
  }
}


// ==================================================
// Attendance API Request
// ==================================================

/**
 * Sends attendance request to the PythonAnywhere API.
 */
void sendAttendanceRequest() {

  if (WiFi.status() != WL_CONNECTED) {

    Serial.println(
      "Attendance: WiFi not connected"
    );

    return;
  }

  Serial.println();
  Serial.println("========== ATTENDANCE ==========");

  Serial.println("Request URL:");
  Serial.println(attendanceUrl);

  HTTPClient http;

  http.begin(attendanceUrl);

  int httpCode = http.GET();

  Serial.print("HTTP Code : ");
  Serial.println(httpCode);

  if (httpCode > 0) {

    String response = http.getString();

    Serial.println("Raw API Response:");
    Serial.println(response);

    if (httpCode == 200) {

      Serial.println("Status    : SUCCESS");

    } else {

      Serial.println("Status    : HTTP RESPONSE RECEIVED");
    }

  } else {

    Serial.println("Status    : REQUEST FAILED");

    Serial.print("Error     : ");
    Serial.println(
      http.errorToString(httpCode)
    );
  }

  Serial.println("================================");

  http.end();
}


// ==================================================
// Heartbeat API Request
// ==================================================

/**
 * Sends heartbeat request and formats the expected API response.
 */
void sendHeartbeatRequest() {

  if (WiFi.status() != WL_CONNECTED) {

    Serial.println(
      "Heartbeat: WiFi not connected"
    );

    return;
  }

  Serial.println();
  Serial.println("========== HEARTBEAT ==========");

  Serial.println("Request URL:");
  Serial.println(heartbeatUrl);

  HTTPClient http;

  http.begin(heartbeatUrl);

  int httpCode = http.GET();

  Serial.print("HTTP Code : ");
  Serial.println(httpCode);

  if (httpCode > 0) {

    String response = http.getString();

    Serial.println("Raw API Response:");
    Serial.println(response);

    // ------------------------------------------
    // Expected API response:
    //
    // {
    //   "code": "heartbeat",
    //   "device": "device01-lab",
    //   "ok": true,
    //   "serverTime": "2026-10-04 19:50:45",
    //   "timezone": "UTC"
    // }
    // ------------------------------------------

    String code = extractJsonValue(
      response,
      "code"
    );

    String device = extractJsonValue(
      response,
      "device"
    );

    String serverTime = extractJsonValue(
      response,
      "serverTime"
    );

    String timezone = extractJsonValue(
      response,
      "timezone"
    );


    // ------------------------------------------
    // Check actual heartbeat response
    // ------------------------------------------

    if (
      httpCode == 200 &&
      code == "heartbeat" &&
      response.indexOf("\"ok\":true") >= 0
    ) {

      Serial.println();
      Serial.println("Status    : SUCCESS");

      Serial.print("Code      : ");
      Serial.println(code);

      Serial.print("Device    : ");
      Serial.println(device);

      Serial.println("OK        : true");

      Serial.print("ServerTime: ");
      Serial.println(serverTime);

      Serial.print("Timezone  : ");
      Serial.println(timezone);

    } else {

      Serial.println();
      Serial.println("Status    : UNEXPECTED RESPONSE");

      Serial.print("Code      : ");
      Serial.println(code);

      Serial.print("Device    : ");
      Serial.println(device);

      Serial.print("ServerTime: ");
      Serial.println(serverTime);

      Serial.print("Timezone  : ");
      Serial.println(timezone);
    }

  } else {

    Serial.println("Status    : REQUEST FAILED");

    Serial.print("Error     : ");
    Serial.println(
      http.errorToString(httpCode)
    );
  }

  Serial.println("================================");

  http.end();
}


// ==================================================
// Push Button Handler
// ==================================================

/**
 * Detects button press and sends attendance once per press.
 */
void handlePushButton() {

  static bool buttonPressed = false;

  int currentButtonState =
    digitalRead(pushButtonPin);


  // ------------------------------------------
  // Button Pressed
  // ------------------------------------------

  if (currentButtonState == LOW) {

    if (!buttonPressed) {

      buttonPressed = true;

      // Green LED ON
      digitalWrite(
        greenLedPin,
        HIGH
      );

      // LCD
      displayFingerprintTriggered();

      // Serial
      Serial.println(
        "Fingerprint triggered"
      );

      // Send attendance
      sendAttendanceRequest();

      // Small debounce delay
      delay(200);
    }
  }


  // ------------------------------------------
  // Button Released
  // ------------------------------------------

  else {

    if (buttonPressed) {

      buttonPressed = false;

      // Green LED OFF
      digitalWrite(
        greenLedPin,
        LOW
      );

      // LCD
      displayBioTrack();

      // Serial
      Serial.println(
        "Fingerprint released"
      );
    }
  }
}


// ==================================================
// Setup
// ==================================================

void setup() {

  // ------------------------------------------
  // Serial
  // ------------------------------------------

  Serial.begin(115200);


  // ------------------------------------------
  // GPIO
  // ------------------------------------------

  pinMode(
    blinkLedPin,
    OUTPUT
  );

  pinMode(
    greenLedPin,
    OUTPUT
  );

  pinMode(
    pushButtonPin,
    INPUT_PULLUP
  );


  // ------------------------------------------
  // Initial LED State
  // ------------------------------------------

  digitalWrite(
    blinkLedPin,
    LOW
  );

  digitalWrite(
    greenLedPin,
    LOW
  );


  // ------------------------------------------
  // I2C
  // ------------------------------------------

  Wire.begin();


  // ------------------------------------------
  // LCD
  // ------------------------------------------

  lcd.init();

  lcd.backlight();


  // ------------------------------------------
  // Startup Screen
  // ------------------------------------------

  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("BioTrack");

  lcd.setCursor(0, 1);
  lcd.print("Starting...");


  // ------------------------------------------
  // Startup LED
  // ------------------------------------------

  delay(100);

  digitalWrite(
    blinkLedPin,
    HIGH
  );

  delay(1000);

  digitalWrite(
    blinkLedPin,
    LOW
  );

  delay(1000);


  // ------------------------------------------
  // WiFi
  // ------------------------------------------

  connectToWiFi();


  // ------------------------------------------
  // Ready
  // ------------------------------------------

  displayBioTrack();

  Serial.println();
  Serial.println("BioTrack started");
  Serial.println("Heartbeat monitoring active");
}


// ==================================================
// Main Loop
// ==================================================

void loop() {

  // ------------------------------------------
  // Check Push Button
  // ------------------------------------------

  handlePushButton();


  // ------------------------------------------
  // Heartbeat LED ON
  // ------------------------------------------

  digitalWrite(
    blinkLedPin,
    HIGH
  );


  // ------------------------------------------
  // Send Heartbeat
  // ------------------------------------------

  sendHeartbeatRequest();


  // ------------------------------------------
  // Keep LED ON
  // ------------------------------------------

  delay(500);


  // ------------------------------------------
  // Heartbeat LED OFF
  // ------------------------------------------

  digitalWrite(
    blinkLedPin,
    LOW
  );


  // ------------------------------------------
  // Wait Before Next Heartbeat
  // ------------------------------------------

  delay(10000);
}