#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <DHTesp.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define DHT_PIN 1
#define SD_CS   5

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

DHTesp dht;
File logFile;

unsigned long lastRead = 0;
const unsigned long interval = 2000; // 2 seconds

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

  // I2C OLED
  Wire.begin(21, 22);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED not found");
    while (true);
  }

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("Starting...");
  display.display();

  // DHT22
  dht.setup(DHT_PIN, DHTesp::DHT22);

  // SD card
  SPI.begin(18, 19, 23, SD_CS);
  if (!SD.begin(SD_CS)) {
    Serial.println("SD card init failed");
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("SD init failed");
    display.display();
    while (true);
  }

  Serial.println("SD card ready");

  // Create file header if file does not exist
  if (!SD.exists("/temp.csv")) {
    logFile = SD.open("/temp.csv", FILE_WRITE);
    if (logFile) {
      logFile.println("time_ms,temperature_c,humidity_percent");
      logFile.close();
    }
  }
}

void loop() {
  if (millis() - lastRead >= interval) {
    lastRead = millis();

    TempAndHumidity data = dht.getTempAndHumidity();

    if (isnan(data.temperature) || isnan(data.humidity)) {
      Serial.println("Failed to read from DHT sensor");
      showError("Sensor read failed");
      return;
    }

    Serial.print("Temp: ");
    Serial.print(data.temperature);
    Serial.print(" C  Humidity: ");
    Serial.print(data.humidity);
    Serial.println(" %");

    // OLED display
    display.clearDisplay();
    display.setTextSize(1);
    display.setCursor(0, 0);
    display.println("Temperature Logger");
    display.println("------------------");
    display.print("Temp: ");
    display.print(data.temperature, 1);
    display.println(" C");
    display.print("Humidity: ");
    display.print(data.humidity, 1);
    display.println(" %");
    display.print("Time: ");
    display.print(millis() / 1000);
    display.println(" s");
    display.display();

    // Log to SD card
    logFile = SD.open("/temp.csv", FILE_APPEND);
    if (logFile) {
      logFile.print(millis());
      logFile.print(",");
      logFile.print(data.temperature, 1);
      logFile.print(",");
      logFile.println(data.humidity, 1);
      logFile.close();
      Serial.println("Logged to SD");
    } else {
      Serial.println("Failed to open log file");
    }
  }
}

void showError(const char* msg) {
  display.clearDisplay();
  display.setCursor(0, 0);
  display.println("ERROR");
  display.println(msg);
  display.display();
}