#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1  // Change to -1 for no reset pin
#define SCREEN_ADDRESS 0x3C

Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const char* ssid = "Wokwi-GUEST"; // Replace with your WiFi SSID
const char* password = ""; // Replace with your WiFi password

void setup() {
 Serial.begin(115200);

 // Initialize OLED display with I2C address 0x3C
 if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("Failed to start SSD1306 OLED"));
    while (1);
 }

 delay(2000);         // Wait two seconds for initializing
 oled.clearDisplay(); // Clear display

 oled.setTextSize(1);         // Set text size
 oled.setTextColor(WHITE);    // Set text color
 oled.setCursor(15, 30);       // Set position to display (x,y)
 oled.println("Welcome to APEX"); // Set text
 oled.display();              // Display on OLED
 WiFi.begin(ssid, password);

 while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
 }

 Serial.println("");
 Serial.println("WiFi connected.");
 Serial.println(WiFi.localIP());

 delay(2000); // Wait 2 seconds for loading screen

 // Loading animation during the loading screen
 for (int i = 0; i < 3; i++) {
    displayLoadingAnimation();
    delay(500);
 }

 oled.clearDisplay(); // Clear display

 // Connect to WiFi
 Serial.print("Connecting to ");
 Serial.println(ssid);
}

void displayLoadingAnimation() {
  oled.clearDisplay();
  oled.setTextSize(1);
  oled.setTextColor(WHITE);
  oled.setCursor(40, 30);
  oled.print("Loading");
  for (int i = 0; i < 3; i++) {
    oled.print(".");
    oled.display();
    delay(500);
  }
}

void loop() {
  String network = get_network();
  String battery = get_battery();

  display_battery_and_network(battery, network);
}

String sendCommand(const String &command) { // sends an AT command to a device (assumedly a modem or similar) and returns the response
  Serial2.println(command);
  delay(100);
  return Serial2.readString();
}

String get_network() { //retrieves the signal strength, and maps it to a percentage value
  String response = sendCommand("AT+CSQ");
  Serial.println(response);

  int index1 = response.indexOf(":");
  int index2 = response.indexOf(",");
  String result = response.substring(index1 + 1, index2);
  result.trim();

  int signalStrength = result.toInt();
  if (signalStrength == 99) {
    return "0";
  } else if (signalStrength >= 2 && signalStrength <= 9) {
    return "20";
  } else if (signalStrength >= 10 && signalStrength <= 14) {
    return "40";
  } else if (signalStrength >= 15 && signalStrength <= 19) {
    return "60";
  } else if (signalStrength >= 20 && signalStrength <= 31) {
    return "99";
  }

  return "0";
}

String get_battery() { // etrieves the battery level, and returns it.
  String response = sendCommand("AT+CBC");
  Serial.println(response);

  int index1 = response.indexOf(",");
  int index2 = response.indexOf(",", index1 + 1);
  String result = response.substring(index1 + 1, index2);
  result.trim();

  return result;
}

void display_battery_and_network(const String &battery, const String &network) {
  oled.clearDisplay();

  // Display Battery Indicator on the left side
  oled.setTextSize(1);
  oled.setTextColor(WHITE);
  oled.setCursor(2, 5);
  oled.print("Bat:");
  oled.print(battery);
  oled.print("%");
  oled.drawRect(14, 20, 10, 20, WHITE);
  oled.fillRect(14, 20, (int)(10 * battery.toInt() / 100), 20, WHITE);

  // Display WiFi Indicator on the right side
  oled.setTextSize(1);
  oled.setTextColor(WHITE);
  oled.setCursor(110, 5);
  oled.print("WiFi");
  int net = network.toInt() / 20;
  int x1 = 118, y1 = 20, x2 = 10, y2 = 4;
  for (int i = 1; i <= net; i++) {
    oled.fillRect(x1, y1, x2, y2, WHITE);
    y1 += 6;
    y2 += 6;
  }

  oled.display();
  delay(2000);
}