#include <U8g2lib.h>

U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE);




void setup() {
  // put your setup code here, to run once:
  u8g2.begin();
  u8g2.enableUTF8Print();
  Serial.begin(9600);
  //u8g2.setFont(u8g2_font_logisoso28_tn);
  u8g2.setFont(u8g2_font_haxrcorp4089_t_cyrillic);
}

#define UPDATE_PERIOD 333

#define HEIGHT 64
#define WIDTH 128


const char item0[] PROGMEM = "тестовый  текст\0";
const char item1[] PROGMEM = "тестовый  текст\0";

const char *const list[] PROGMEM = {item0, item1};

void substring(const char *str, char* result, size_t start, size_t end)
{
    // if (str == nullptr || start > end || start >= strlen(str))
    // {
    //     debugln("substring error");
    //     return nullptr;
    // }
    

    size_t substr_length = min(2*end, strlen(str)) - 2*start;

    if (substr_length < 2) 
        return nullptr;
    //char *substr = new char[substr_length + 1]; // +1 for the null terminator

    // Use memcpy to copy the substring into the new variable
    memcpy(result, str + 2*start, substr_length);

    // Don't forget to null-terminate the new string
    result[substr_length] = '\0';
    //return substr;
}

const uint8_t TEXT_LEN = 2;
const uint8_t TEXT_START = 0;

void loop() {
  
  PGM_P pstr = pgm_read_word(list);
  char buffer[strlen_P(pstr)+1];
  strcpy_P(buffer, pstr);
  u8g2.setCursor(4, 30);
  char* result[2*TEXT_LEN + 1];
  substring(result,TEXT_START, TEXT_START + TEXT_LEN)

  //Serial.println(result);
  u8g2.print(result);
  //delete

  u8g2.updateDisplay();
  delay(UPDATE_PERIOD);

}