/*
   ESP32 Moon Phase Calculator with OLED Display-CircuitSchools
   Hardware Required:
   - ESP32 Development Board
   - SSD1306 OLED Display (128x64, I2C)
   Wiring (I2C):
   - OLED SDA -> GPIO 21
   - OLED SCL -> GPIO 22
   - OLED VCC -> 3.3V
   - OLED GND -> GND
   Libraries Required:
   - Adafruit SSD1306
   - Adafruit GFX Library
   - WiFi (built-in)
   - time.h (built-in)
*/
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>
#include <time.h>
// OLED Display Settings
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
#define SCREEN_ADDRESS 0x3C

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
// WiFi Credentials - CHANGE THESE!
const char* ssid = "Wokwi-GUEST";
const char* password = "";
// NTP Server Settings
const char* ntpServer = "pool.ntp.org";
const long gmtOffset_sec = 19800;  // GMT+5:30 for India (change as needed)
const int daylightOffset_sec = 0;
// Moon phase names
const char* moonPhaseNames[] = {
  "New Moon",
  "Waxing Crescent",
  "First Quarter",
  "Waxing Gibbous",
  "Full Moon",
  "Waning Gibbous",
  "Last Quarter",
  "Waning Crescent"
};

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

  // Initialize OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println(F("Moon Phase Calc"));
  display.println(F("Connecting WiFi..."));
  display.display();
  // Connect to WiFi
  WiFi.begin(ssid, password);
  int attempts = 0;
  while (WiFi.status() != WL_CONNECTED && attempts < 20) {
    delay(500);
    Serial.print(".");
    attempts++;
  }

  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("\nWiFi connected");
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println(F("WiFi Connected!"));
    display.display();
    delay(1000);
    // Initialize time
    configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
    delay(2000);
  } else {
    Serial.println("\nWiFi connection failed");
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println(F("WiFi Failed!"));
    display.println(F("Check credentials"));
    display.display();
    delay(3000);
  }
}

void loop() {
  struct tm timeinfo;
  if (!getLocalTime(&timeinfo)) {
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println(F("Failed to get time"));
    display.display();
    delay(5000);
    return;
  }
  // Calculate moon phase
  float phase = calculateMoonPhase(timeinfo.tm_year + 1900, timeinfo.tm_mon + 1, timeinfo.tm_mday);
  int phaseIndex = (int)((phase / 29.53) * 8) % 8;
  // Display moon phase
  displayMoonPhase(phase, phaseIndex, timeinfo);
// Update every minute
  delay(60000); 
}

float calculateMoonPhase(int year, int month, int day) {
  // Julian date calculation
  if (month < 3) {
    year--;
    month += 12;
  }
  int a = year / 100;
  int b = a / 4;
  int c = 2 - a + b;
  float e = floor(365.25 * (year + 4716));
  float f = floor(30.6001 * (month + 1));
  float jd = c + day + e + f - 1524.5;
  // Days since known new moon (Jan 6, 2000)
  float daysSinceNew = jd - 2451549.5;
  // Number of new moons since Jan 6, 2000
  float newMoons = daysSinceNew / 29.53;
  // Current phase (0-29.53 days)
  float phase = (newMoons - (int)newMoons) * 29.53;

  return phase;
}

void displayMoonPhase(float phase, int phaseIndex, struct tm timeinfo) {
  display.clearDisplay();
  // Display date and time
  display.setTextSize(1);
  display.setCursor(0, 0);
  char dateStr[20];
  sprintf(dateStr, "%02d/%02d/%04d", timeinfo.tm_mday, timeinfo.tm_mon + 1, timeinfo.tm_year + 1900);
  display.println(dateStr);

  char timeStr[10];
  sprintf(timeStr, "%02d:%02d:%02d", timeinfo.tm_hour, timeinfo.tm_min, timeinfo.tm_sec);
  display.println(timeStr);
  // Draw moon
  int centerX = 32;
  int centerY = 42;
  int radius = 15;
  // Draw moon circle
  display.fillCircle(centerX, centerY, radius, SSD1306_WHITE);
  // Calculate illumination percentage
  float illumination = (1 - cos((phase / 29.53) * 2 * PI)) / 2;
  // Draw shadow for moon phase
  if (phase < 14.765) {
    // Waxing - shadow on left
    int shadowWidth = (int)(radius * 2 * (1 - illumination));
    for (int i = -radius; i <= radius; i++) {
      int h = sqrt(radius * radius - i * i);
      for (int j = -h; j < -h + shadowWidth; j++) {
        display.drawPixel(centerX + j, centerY + i, SSD1306_BLACK);
      }
    }
  } else {
    // Waning - shadow on right
    int shadowWidth = (int)(radius * 2 * illumination);
    for (int i = -radius; i <= radius; i++) {
      int h = sqrt(radius * radius - i * i);
      for (int j = h - shadowWidth; j <= h; j++) {
        display.drawPixel(centerX + j, centerY + i, SSD1306_BLACK);
      }
    }
  }
  // Display phase name
  display.setCursor(64, 25);
  display.setTextSize(1);
  display.println(moonPhaseNames[phaseIndex]);
  // Display illumination percentage
  display.setCursor(64, 38);
  char illumStr[15];
  sprintf(illumStr, "%.1f%% lit", illumination * 100);
  display.println(illumStr);
  // Display age
  display.setCursor(64, 50);
  char ageStr[15];
  sprintf(ageStr, "Day %.1f", phase);
  display.println(ageStr);

  display.display();
}