#include <LiquidCrystal.h>
#include <stdint.h>
#include <string.h>

constexpr uint8_t PIN_RS = 6;
constexpr uint8_t PIN_EN = 7;
constexpr uint8_t PIN_DB4 = 8;
constexpr uint8_t PIN_DB5 = 9;
constexpr uint8_t PIN_DB6 = 10;
constexpr uint8_t PIN_DB7 = 11;

constexpr unsigned long SERIAL_BAUD = 115200;
constexpr size_t LCD_COLUMNS = 16;
constexpr size_t LCD_ROWS = 2;
constexpr size_t INPUT_BUFFER_SIZE = 40;

LiquidCrystal lcd(PIN_RS, PIN_EN, PIN_DB4, PIN_DB5, PIN_DB6, PIN_DB7);

char line1[LCD_COLUMNS + 1] = "Booting...      ";
char line2[LCD_COLUMNS + 1] = "Waiting data... ";
char inputBuffer[INPUT_BUFFER_SIZE];
size_t inputPos = 0;

void copyLine(char* destination, const char* source) {
  for (size_t i = 0; i < LCD_COLUMNS; ++i) {
    if (source[i] == '\0') {
      for (size_t j = i; j < LCD_COLUMNS; ++j) {
        destination[j] = ' ';
      }
      destination[LCD_COLUMNS] = '\0';
      return;
    }
    destination[i] = source[i];
  }
  destination[LCD_COLUMNS] = '\0';
}

void renderDisplay() {
  lcd.setCursor(0, 0);
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
}

void handleMessage(const char* message) {
  if (strncmp(message, "L1:", 3) == 0) {
    copyLine(line1, message + 3);
    renderDisplay();
    return;
  }

  if (strncmp(message, "L2:", 3) == 0) {
    copyLine(line2, message + 3);
    renderDisplay();
  }
}

void readSerial() {
  while (Serial.available() > 0) {
    const char incoming = static_cast<char>(Serial.read());

    if (incoming == '\r') {
      continue;
    }

    if (incoming == '\n') {
      inputBuffer[inputPos] = '\0';
      handleMessage(inputBuffer);
      inputPos = 0;
      continue;
    }

    if (inputPos + 1 < INPUT_BUFFER_SIZE) {
      inputBuffer[inputPos++] = incoming;
    } else {
      inputPos = 0;
    }
  }
}

void setup() {
  lcd.begin(LCD_COLUMNS, LCD_ROWS);
  renderDisplay();
  Serial.begin(SERIAL_BAUD);
}

void loop() {
  readSerial();
}