#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

const char* LED_GREEN = 12;
const char* LED_RED = 13;

/* Display */
LiquidCrystal_I2C lcd(0x27, 20, 4);

/* Keypad setup */
const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 4;
byte rowPins[KEYPAD_ROWS] = {5, 4, 3, 2};
byte colPins[KEYPAD_COLS] = {A3, A2, A1, A0};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'.', '0', '.', 'D'}
};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, KEYPAD_ROWS, KEYPAD_COLS);

float min_weight;
float max_weight;

String readKeypad(int col, int row) {
  String key_cache;
  int index = 0;
  lcd.setCursor(col, row);
  while (true) {
    char key = keypad.getKey();
    String _key = String(key);
    if (key) {
      if (key_cache.length() <= 4 && _key != "A" && _key != "B" && _key != "C" && _key != "D") {
        if (key_cache.indexOf(".") == -1 ) {
          key_cache += String(_key);
          lcd.setCursor(col + index, row);
          lcd.print(key_cache[index]);
          index++;
        } else if (_key != ".") {
          key_cache += String(_key);
          lcd.setCursor(col + index, row);
          lcd.print(key_cache[index]);
          index++;
        }
      } else if (_key == "D" && index > 0) {
        lcd.noBlink();
        key_cache = key_cache.substring(0, key_cache.length() - 1);
        index -= 1;
        lcd.setCursor((col + index), row);
        lcd.print(key_cache[index] + " ");
        lcd.setCursor((col + index), row);
        lcd.blink();
      } else if (_key == "C") {
        return key_cache;
      } else if (_key == "B") {
        return "";
      }
    }

    // Serial.println("index: " + String(index) + "key_cache: " + key_cache);
  }
}

void setMinMax() {
  lcd.clear();
  lcd.setCursor(1, 0);
  lcd.print("SET MIN-MAX WEIGHT");
  lcd.setCursor(0, 3);
  lcd.print("MIN:");
  lcd.setCursor(10, 3);
  lcd.print("MAX:");
  lcd.blink();

  String min_weight_str = "";
  String max_weight_str = "";
  while (min_weight_str == "" || max_weight_str == "") {
    min_weight_str = "";
    max_weight_str = "";
    lcd.setCursor(14, 3);
    lcd.print("     ");
    lcd.setCursor(4, 3);
    lcd.print("     ");
    min_weight_str = readKeypad(4, 3);

    if (min_weight_str == "") {
      continue;
    } else {
      max_weight_str = readKeypad(14, 3);
      if (max_weight_str.toFloat() < min_weight_str.toFloat())
        max_weight_str = "";
    }
  }

  min_weight = min_weight_str.toFloat();
  max_weight = max_weight_str.toFloat();
}

void setup() {
  Serial.begin(115200);
  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_RED, OUTPUT);
  lcd.init();
  lcd.backlight();
  lcd.clear();
  if (!min_weight && !max_weight) {
    setMinMax();
    lcd.clear();
  }
}

bool scr_main_state = false;
void loop() {
  if (!scr_main_state) {
    lcd.noBlink();
    lcd.setCursor(4, 0);
    lcd.print("<< READY >>");
    lcd.setCursor(0, 1);
    lcd.print("TOTAL: " + String(12056) + " PCS");
    lcd.setCursor(0, 2);
    lcd.print("MIN:" + String(min_weight));
    lcd.setCursor(10, 2);
    lcd.print("MAX:" + String(max_weight));
    lcd.setCursor(0, 3);
    lcd.print("WEIGHING: ");
    scr_main_state = !scr_main_state;
    lcd.blink();
  }

  lcd.setCursor(10, 3);
  lcd.print("          ");
  float current_weight = readKeypad(10, 3).toFloat();
  lcd.noBlink();
  lcd.setCursor(7, 0);
  lcd.print("Wait...");
  if (current_weight < min_weight || current_weight > max_weight)
    alert();
  else
    digitalWrite(LED_GREEN, HIGH);

  delay(200);
  digitalWrite(LED_GREEN, LOW);
  scr_main_state = !scr_main_state;
}

void alert() {
  for (int i = 0; i < 10; i++) {
    digitalWrite(LED_RED, HIGH);
    lcd.noBacklight();
    delay(100);
    lcd.backlight();
    digitalWrite(LED_RED, LOW);
    delay(100);
  }
}