// esp32_i2c_lcd_scroll.ino
// Simple scrolling text on a 16x2 I2C LCD using LiquidCrystal_I2C

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ----- CONFIG -----
#define LCD_ADDR 0x27       // change to 0x3F if your module uses that address
#define LCD_COLS 16
#define LCD_ROWS 2

LiquidCrystal_I2C lcd(LCD_ADDR, LCD_COLS, LCD_ROWS);

// The text to scroll (can be long)
const char scrollText[] = "Hello from ESP32! This is a scrolling demo on a 16x2 I2C LCD.   ";
// extra spaces at end give a gap between repeats

// Optional static second-line text (set empty "" to keep blank)
const char secondLine[] = "ESP32 I2C LCD";

const unsigned long scrollDelayMs = 100; // speed: smaller = faster

void setup() {
  Serial.begin(115200);
  delay(50);
  Serial.println("LCD scroll demo starting...");

  lcd.init();        // initialize LCD
  lcd.backlight();   // switch backlight on (if supported)

  // If second line is used, print it (trim to LCD_COLS)
  if (strlen(secondLine) > 0) {
    char tmp[LCD_COLS + 1];
    strncpy(tmp, secondLine, LCD_COLS);
    tmp[LCD_COLS] = '\0';
    lcd.setCursor(0, 1);
    lcd.print(tmp);
  }
}

void loop() {
  scrollLine(scrollText, LCD_COLS, scrollDelayMs);
}

// Scrolls a string across a single LCD line (row 0).
// If text length <= cols, just prints it centered/left.
void scrollLine(const char *text, uint8_t cols, unsigned long delayMs) {
  size_t len = strlen(text);

  // If fits in display width, just show and pause
  if (len <= cols) {
    lcd.setCursor(0, 0);
    lcd.print(text);
    // fill rest with spaces to clear any old chars
    for (uint8_t i = len; i < cols; ++i) lcd.print(' ');
    delay(delayMs * 2); // keep visible a bit
    return;
  }

  // For longer text, slide window of width 'cols' across the string,
  // and wrap around so it continuously scrolls.
  // We'll create a buffer of text repeated twice with spaces for smooth wrap.
  String s = String(text);
  // Append enough spaces at the end to create visible gap already included in text variable.
  // To ease wrap, make a doubled string:
  String doubled = s + s;

  for (size_t offset = 0; offset < s.length(); ++offset) {
    // Extract substring of length cols starting at offset
    String window = doubled.substring(offset, offset + cols);
    lcd.setCursor(0, 0);
    lcd.print(window);
    delay(delayMs);
  }
}