/*
  ESP32-C3 Super Mini + MAX7219 (4x cascaded 8x8, 32x8 total)
  IoT Clock for India — NTP synced to IST (UTC +5:30)

  Board:   ESP32-C3 Super Mini
  Display: MAX7219 dot matrix, 4 modules cascaded (32 columns x 8 rows)

  Wiring (MAX7219 -> ESP32-C3 Super Mini):
    VCC -> 5V (or 3V3 if module regulator allows; prefer 5V from USB)
    GND -> GND
    DIN -> GPIO7
    CS  -> GPIO10
    CLK -> GPIO4

  Library required: MD_MAX72XX by majicDesigns
           (Sketch > Include Library > Manage Libraries > search "MD_MAX72XX")
           Also needs MD_Parola (optional, used here for text/scroll) and SPI (built-in)

  Author signature block preserved per house style:
  Arvind Patil / AI Centre Nandurbar / Ysz4 / HansaScript
*/

#include <WiFi.h>
#include <time.h>
#include <SPI.h>
#include <MD_MAX72xx.h>
#include <MD_Parola.h>

// ---------- WiFi credentials ----------
const char* WIFI_SSID     = "Airtel_arvi_6035";
const char* WIFI_PASSWORD = "air26289";

// ---------- NTP / IST settings ----------
const char* NTP_SERVER      = "pool.ntp.org";
const long  GMT_OFFSET_SEC  = 5 * 3600 + 1800;  // IST = UTC +5:30
const int   DST_OFFSET_SEC  = 0;                // India does not observe DST

// ---------- MAX7219 wiring ----------
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
#define MAX_DEVICES   4      // 4 x 8x8 = 32x8

#define CLK_PIN   4    // GPIO4  -> CLK
#define DATA_PIN  7    // GPIO7  -> DIN
#define CS_PIN    10   // GPIO10 -> CS

MD_Parola display = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

// ---------- Display modes ----------
enum ClockMode { MODE_TIME, MODE_DATE, MODE_SCROLL };
ClockMode currentMode = MODE_TIME;
bool use24h = true;

unsigned long lastSwitch = 0;
const unsigned long MODE_INTERVAL_MS = 8000; // auto-cycle every 8s (set to 0 to disable)

char buf[64];

void connectWiFi() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to WiFi");
  unsigned long start = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - start < 20000) {
    delay(400);
    Serial.print(".");
  }
  Serial.println();
  if (WiFi.status() == WL_CONNECTED) {
    Serial.print("WiFi connected. IP: ");
    Serial.println(WiFi.localIP());
  } else {
    Serial.println("WiFi connect failed — will keep retrying in background.");
  }
}

void syncNTP() {
  configTime(GMT_OFFSET_SEC, DST_OFFSET_SEC, NTP_SERVER);
  Serial.print("Waiting for NTP time sync");
  struct tm timeinfo;
  int attempts = 0;
  while (!getLocalTime(&timeinfo) && attempts < 20) {
    Serial.print(".");
    delay(500);
    attempts++;
  }
  Serial.println();
  if (attempts < 20) {
    Serial.println("NTP sync OK (IST).");
  } else {
    Serial.println("NTP sync failed — check WiFi/internet.");
  }
}

void formatTimeString(struct tm &t, char *out, size_t outLen) {
  int h = t.tm_hour;
  const char *suffix = "";
  if (!use24h) {
    suffix = (h >= 12) ? " P" : " A";
    h = h % 12;
    if (h == 0) h = 12;
  }
  if (use24h) {
    snprintf(out, outLen, "%02d:%02d:%02d", h, t.tm_min, t.tm_sec);
  } else {
    snprintf(out, outLen, "%02d:%02d:%02d%s", h, t.tm_min, t.tm_sec, suffix);
  }
}

void formatDateString(struct tm &t, char *out, size_t outLen) {
  snprintf(out, outLen, "%02d-%02d-%04d", t.tm_mday, t.tm_mon + 1, t.tm_year + 1900);
}

void updateDisplay() {
  struct tm timeinfo;
  if (!getLocalTime(&timeinfo)) {
    display.displayText("NO SYNC", PA_CENTER, 0, 0, PA_PRINT, PA_NO_EFFECT);
    display.displayAnimate();
    return;
  }

  if (currentMode == MODE_TIME) {
    formatTimeString(timeinfo, buf, sizeof(buf));
    display.displayText(buf, PA_CENTER, 0, 0, PA_PRINT, PA_NO_EFFECT);
    display.displayAnimate();
  } else if (currentMode == MODE_DATE) {
    formatDateString(timeinfo, buf, sizeof(buf));
    display.displayText(buf, PA_CENTER, 0, 0, PA_PRINT, PA_NO_EFFECT);
    display.displayAnimate();
  } else if (currentMode == MODE_SCROLL) {
    char t1[16], t2[16];
    formatTimeString(timeinfo, t1, sizeof(t1));
    formatDateString(timeinfo, t2, sizeof(t2));
    snprintf(buf, sizeof(buf), "%s   %s   ", t1, t2);
    if (display.displayAnimate()) {
      display.displayText(buf, PA_LEFT, 60, 0, PA_SCROLL_LEFT, PA_SCROLL_LEFT);
    }
  }
}

void setup() {
  Serial.begin(115200);
  delay(300);
  Serial.println("\nESP32-C3 Super Mini + MAX7219 — IST IoT Clock");
  Serial.println("Arvind Patil / AI Centre Nandurbar / Ysz4 / HansaScript");

  display.begin();
  display.setIntensity(6);      // 0 (dim) - 15 (max brightness)
  display.displayClear();
  display.displayText("BOOT", PA_CENTER, 0, 0, PA_PRINT, PA_NO_EFFECT);
  display.displayAnimate();

  connectWiFi();
  syncNTP();

  display.displayClear();
}

void loop() {
  // Re-attempt WiFi reconnect silently if dropped
  if (WiFi.status() != WL_CONNECTED) {
    WiFi.reconnect();
  }

  // Auto-cycle display modes (optional)
  if (MODE_INTERVAL_MS > 0 && millis() - lastSwitch > MODE_INTERVAL_MS) {
    lastSwitch = millis();
    currentMode = (ClockMode)((currentMode + 1) % 3);
    display.displayClear();
  }

  updateDisplay();
  delay(currentMode == MODE_SCROLL ? 20 : 200);
}