// Waveshare 1.54” ePaper display (GDEH0154D67)
// https://www.waveshare.com/wiki/1.54inch_e-Paper_Module_(B)


#include <GxEPD2_BW.h>
#include <GxEPD2_3C.h>
#include <SPI.h>
#include <Fonts/FreeMonoBold9pt7b.h>
#include <Fonts/FreeMonoBold12pt7b.h>
#include <Wire.h>

// === Pin Definitions ===
#define EPD_CS     17   // Chip Select
#define EPD_DC     16   // Data/Command
#define EPD_RST    23   // Reset
#define EPD_BUSY   22   // Busy

// SPI pins (custom mapping if needed)
#define EPD_MOSI  18   // SPI MOSI (DIN)
#define EPD_SCK    19   // SPI Clock (CLK)

// Optional: define MISO if your board or library needs it (not used by display)
#define EPD_MISO  -1   // ePaper doesn't use MISO


// === GxEPD2 Display object (1.54" 200x200) ===
// GxEPD2_BW<GxEPD2_154_D67, GxEPD2_154_D67::HEIGHT> display(GxEPD2_154_D67(
//   EPD_CS, EPD_DC, EPD_RST, EPD_BUSY));
// 3-color 1.54" e-paper class (200x200 resolution)
// GxEPD2_3C<GxEPD2_154c, GxEPD2_154c::HEIGHT> display(GxEPD2_154c(EPD_CS, EPD_DC, EPD_RST, EPD_BUSY));
GxEPD2_3C<GxEPD2_154c, GxEPD2_154c::HEIGHT> display(
  GxEPD2_154c(EPD_CS, EPD_DC, EPD_RST, EPD_BUSY));



// Optional: replace with RTC if available (e.g. DS3231 via RTClib)
unsigned long lastUpdate = 0;
unsigned long refreshInterval = 30000; // 30 seconds
int counter = 0;

// Timekeeping
unsigned long bootMillis;
int hours = 12, minutes = 0, seconds = 0;

// Helper: format two digits
String formatDigits(int digits) {
  if (digits < 10) return "0" + String(digits);
  return String(digits);
}


// ====== 🔧 Wait for BUSY Pin Helper ======
void waitWhileBusy(const char* label) {
  Serial.print("🕒 Waiting for BUSY (");
  Serial.print(label);
  Serial.println(")...");
  uint32_t start = millis();
  while (digitalRead(EPD_BUSY)) {
    if (millis() - start > 10000) {
      Serial.println("⛔ BUSY Timeout!");
      break;
    }
    delay(10);
  }
  Serial.println("✅ BUSY cleared.");
}

// Setup the screen with initial static content
void drawInitialScreen() {
  Serial.println("🖥️ Drawing initial screen...");
  display.setFullWindow();
  Serial.println("debug 0");
  display.firstPage();
  do {
    Serial.println("debug 1");
    display.fillScreen(GxEPD_WHITE);
    Serial.println("debug 2");
    display.setFont(&FreeMonoBold12pt7b);
    Serial.println("debug 3");
    display.setTextColor(GxEPD_BLACK);
    Serial.println("debug 4");
    display.setCursor(30, 60);
    display.print("Counter:");
  } while (display.nextPage());
  Serial.println("✅ Initial screen drawn.");
}

// Draw the counter value with partial refresh
void drawCounter() {
  Serial.print("🔢 Updating counter to: ");
  Serial.println(counter);

  char buffer[16];
  snprintf(buffer, sizeof(buffer), "%d", counter);

  // Define the area to refresh
  display.setPartialWindow(30, 80, 140, 40);
  display.firstPage();
  do {
    display.fillRect(30, 80, 140, 40, GxEPD_WHITE);  // Clear previous text
    display.setCursor(30, 110);
    display.setTextColor(GxEPD_RED); // Use red for the counter
    display.print(buffer);
  } while (display.nextPage());

  Serial.println("✅ Counter updated.");
}

void setup() {
  Serial.begin(115200);
  delay(100);
  delay(2000);
  Serial.println("🚀 Starting ePaper test...");


  pinMode(EPD_BUSY, INPUT);
  pinMode(EPD_RST, OUTPUT);
  pinMode(EPD_DC, OUTPUT);
  pinMode(EPD_CS, OUTPUT);


  // Initialize SPI with custom pins BEFORE display.init()
  SPI.begin(EPD_SCK, EPD_MISO, EPD_MOSI, EPD_CS); // SCK, MISO, MOSI, SS


  Serial.println("🔌 Initializing display...");
  display.init(115200);  // optional: set SPI frequency
  display.setRotation(1);
  display.setFont(&FreeMonoBold12pt7b);
  // display.setTextColor(GxEPD_BLACK);

  Serial.println("🖼️ Display initialized");
  waitWhileBusy("post-init");
  
  drawInitialScreen();
  // drawTime();  // first time display
  drawCounter();
  lastUpdate = millis();

}

void loop() {
  if (millis() - lastUpdate >= refreshInterval) {
    counter++;
    drawCounter();
    lastUpdate = millis();
  }
}