/*
  Sync UNIX Time with Computer and
  LCD Display with I2C on Arduino UN0
  Rough Draft 0.1  (needs improvements)
  Neo December 2019
  https://www.unix.com
*/

// Include Wire Library for I2C
#include <Wire.h>
// Include NewLiquidCrystal Library for I2C
#include <LiquidCrystal_I2C.h>
#include <Time.h>
#include <TimeLib.h>

#define TIME_MSG_LEN 11 // time sync to PC is HEADER followed by Unix time_t as ten ASCII digits
#define TIME_HEADER 'T' // Header tag for serial time sync message
#define TIME_REQUEST 7  // ASCII bell character requests a time sync message
#define DEBUG_SKETCH false
// Define LCD pinout
const int en = 2, rw = 1, rs = 0, d4 = 4, d5 = 5, d6 = 6, d7 = 7, bl = 3;
// can be any integer greater than zero and less than recent unix time
const int time_int = 1000;
// Define I2C Address - change if reqiuired
const int i2c_addr = 0x27;
String s;
bool flag = true;
time_t t = now();
LiquidCrystal_I2C lcd(i2c_addr, en, rw, rs, d4, d5, d6, d7, bl, POSITIVE);
void setup()
{
    Serial.begin(9600);
    Wire.begin();
    time_t t = now();
    lcd.begin(16, 2);
    lcd.clear();
}

void loop()
{
    lcd.clear();
    int count = 0;
    if (Serial.available() and flag)
    {
        lcd.clear();
        lcd.setCursor(0, 1);
        lcd.print("Serial OK");
        count = processSyncMessage();
        if (DEBUG_SKETCH)
        {
               Serial.println("Serial Available: " + count);
        }
        if (count > time_int)
            flag = false;
    }

    lcd.setCursor(0, 0);
    if (timeStatus() == timeNotSet)
    {
        if (flag)
        {
            Serial.println("waiting for sync message");
            lcd.print("Arduino Time:");
        }
    }
    else
    {

        lcd.print("Unix Time:");
        if (DEBUG_SKETCH)
        {
            Serial.println("Time Synced");
        }
    }
    t = now();
    s = String(t);
    if (s != '0')
    {
        lcd.setCursor(0, 1);
        lcd.print(t);
        lcd.print(" secs");
    }
    Serial.println(s);
    delay(1000);
    lcd.clear();
}

int processSyncMessage()
{
    while (Serial.available() >= TIME_MSG_LEN)
    { // time message consists of header & 10 ASCII digits
        char c = Serial.read();
        int count = 0;
        Serial.print(c);
        time_t pctime = 0;
        if (c == TIME_HEADER)
        {
            for (int i = 0; i < TIME_MSG_LEN - 1; i++)
            {
                c = Serial.read();
                if (c >= '0' && c <= '9')
                {
                    Serial.print(c);
                    count++;
                    pctime = (10 * pctime) + (c - '0'); // convert digits to a number
                }
            }
            Serial.print("\n");
            if (DEBUG_SKETCH)
            {
                Serial.write(pctime + "\n");
                Serial.println(pctime);
            }
            setTime(pctime); // Sync Arduino clock to the time received on the serial port
        }
        return count;
    }
}