#include <LiquidCrystal.h>

#define backlightPin 10
#define buttonPin 11
#define ledPin 12

LiquidCrystal lcd(2, 3, 4, 5, 6, 7);
String lastMsg = "";

long lastPressed = 0;
long lastMsgTime = 0;

int page = 0; //current screen page

void setup() {
    Serial.begin(9600);
    // set up the LCD's number of columns and rows:
    lcd.begin(16, 2);

    pinMode(backlightPin, OUTPUT);
    pinMode(buttonPin, INPUT);
    pinMode(ledPin, OUTPUT);
    digitalWrite(backlightPin, HIGH);
}

void loop() {
    listen();
}

void doStuff() {
    if (digitalRead(buttonPin) == LOW && (millis() - lastPressed) > 1000) {
        page ^= 1;
        show((page == 0) ? lastMsg : String(lastMsgTime)); //toggle msg/time page
        lastPressed = millis();
    }
}

void listen() {
    String string = "";
    static byte c;

    while (1) {
        doStuff();

        if (!Serial.available()) continue;

        c = Serial.read();
        if (c != '\n') string += char(c);
        else {
            lastMsg = string;
            lastMsgTime = millis() / 1000;
            Serial.println(string);
            show((page == 0) ? string : String(lastMsgTime)); //update the display
            parse(string);
            flash();
            string = "";
        }
    }
}

void show(String text) {
    lcd.clear();
    if (text.length() > 16) {
        String first = text.substring(0, 16);
        String second = text.substring(16);
        lcd.home();
        lcd.print(first);
        lcd.setCursor(0, 1);
        lcd.print(second);
    } else {
        lcd.home();
        lcd.print(text);
    }
}

void parse(String input) {
    if (input == "light on") digitalWrite(ledPin, HIGH);
    if (input == "light off") digitalWrite(ledPin, LOW);
}

void flash() {
    for (int x = 0; x < 3; x++) {
        for (int i = 255; i >= 0; i--) {
            analogWrite(backlightPin, i);
            delay(1);
        }
        for (int i = 0; i < 255; i++) {
            analogWrite(backlightPin, i);
            delay(1);
        }
    }
}