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

// OLED display TWI address
#define OLED_ADDR   0x3C
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

// Declaration for SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// WiFi credentials
const char* ssid     = "Wokwi-GUEST";
const char* password = "";

// CoinGecko API URL
const char* apiURL = "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=eur";

void setup() {
  Serial.begin(115200);
  // Initialize OLED
  if(!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

  // Connect to WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("WiFi connected");

  display.display();
  delay(2000); // Pause for 2 seconds
  display.clearDisplay();
}

void loop() {
  static float lastPrice = 0.0;
  static float lastChange = 0.0;

  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    http.begin(apiURL);
    int httpCode = http.GET();

    if (httpCode > 0) {
      String payload = http.getString();
      float price = parsePrice(payload);
      float change = calculateChange(price, lastPrice);
      lastPrice = price;
      lastChange = change;

      // Now display the price and change
      displayPriceChange(price, change);
    } else {
      Serial.println("Error on HTTP request");
    }
    http.end(); // Free the resources
  }

  delay(5000); // Update every 5 seconds
}

float parsePrice(const String& payload) {
  // Parse the JSON payload for the price
  int startIndex = payload.indexOf("eur\":") + 5;
  int endIndex = payload.indexOf("}", startIndex);
  return payload.substring(startIndex, endIndex).toFloat();
}

float calculateChange(float newPrice, float lastPrice) {
  // Calculate the percentage change
  if (lastPrice == 0) return 0;
  return ((newPrice - lastPrice) / lastPrice) * 100;
}

void displayPriceChange(float price, float change) {
  display.clearDisplay();
  display.setTextSize(2); // Large text for the price
  display.setTextColor(WHITE);

  // Display the price
  display.setCursor(0, 16);
  display.print('$'); // Display the currency symbol
  display.print(price, 2); // Two decimal places

  // Display the percentage change
  display.setTextSize(1); // Smaller text for the percentage
  display.setCursor(0, 0);
  if(change >= 0) {
    display.print("+");
  }
  display.print(change, 2);
  display.print("%");

  //dispay currency types
  display.setTextSize(1);
  display.setCursor(100, 40);
  display.print("LIVE");

  // Display the label "BITCOIN" at the bottom
  display.setTextSize(1);
  display.setCursor((SCREEN_WIDTH - (6 * 7)) / 2, 56); // Center the text
  display.print("BITCOIN");

  display.display(); // Update the display with all the new graphics
}