/*
  Blink

The circuit:
 * VFD Data to digital pin 2 (blue)
 * VFD Clock to digital pin 3 (yellow)
 * VFD Chip select to digital pin 4 (green)
 * VFD VCC (power) to 5V
 * VFD Ground (power) to Ground
*/

// include the library code:
#include <SPI_VFD.h>

// initialize the library with the numbers of the interface pins
SPI_VFD vfd(2, 3, 4);

//                       |         1         2|
//                       |12345678901234567890|
String vfd_line_top =    "Booting up...       ";
String vfd_line_bottom = "Waiting for stream. ";
unsigned int vfd_line_position = 0;
bool vfd_line_print = false;
unsigned long millis_last_incoming_ping = 0;
unsigned long millis_last_outgoing_ping = 0;

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);

  Serial.begin(9600);

  // set up the VFD's number of columns and rows: 
  vfd.begin(20, 2);
  update_display();
}

void update_display() {
  vfd.setCursor(0, 0);
  vfd.print(vfd_line_top);
  vfd.setCursor(0, 1);
  vfd.print(vfd_line_bottom);
}

void check_serial() {
  while (Serial.available() > 0) {
    millis_last_incoming_ping = millis();
    int incomingByte = Serial.read();
    if (incomingByte == 0 || incomingByte == '^') {
      incomingByte = vfd_line_position = 0;
    }
    if (incomingByte < 32) {
      continue;
    }

    if (vfd_line_position < 20) {
      vfd_line_top.setCharAt(vfd_line_position, incomingByte);
    } else {
      vfd_line_bottom.setCharAt(vfd_line_position - 20, incomingByte);
    }
    vfd_line_position = (vfd_line_position + 1) % 40;
    vfd_line_print = vfd_line_position == 0;
    if (vfd_line_print) {
      break;
    }
  }
}

// the loop function runs over and over again forever
void loop() {
  // We've been running for over 50 days and wrapped to zero. Reset all our timers
  if (millis() < 10000 && (millis_last_outgoing_ping > 10000 || millis_last_incoming_ping > 10000)) {
    millis_last_outgoing_ping = 0;
    millis_last_incoming_ping = 0;
  }

  check_serial();

  // If it's been 10 seconds since last incoming data
  if (millis() - millis_last_incoming_ping > 30000) {
    //                |12345678901234567890|
    vfd_line_top =    "Error stream is down";
    vfd_line_bottom = "Verify or restart...";
    vfd_line_print = true;
    millis_last_incoming_ping = millis();
  }
  
  // Send outgoing ping every 5 seconds if we can.
  if (millis() - millis_last_outgoing_ping > 30000 && Serial.availableForWrite()) {
    Serial.write('^');
    millis_last_outgoing_ping = millis();
  }

  // If we have something to print, print it
  if (vfd_line_print) {
    vfd_line_print = false;
    update_display();
  }

  delay(100);
}