Delay within a timer (what is the correct approach) - c

Question

I'm in a pickle regarding concepts relating to timers. How can I can I operate a "delay" inside a timer? This is the best way I can frame the question knowing full well what I'm trying to do is nonsense. The objective is: I wish to test the pinState condition 2 times (once initially and then 4 seconds later) but this all needs to happen periodically (hence a timer).
The platform is NodeMCU running a WiFi (ESP8266 chip) and coding done inside Arduino IDE.
#define BLYNK_PRINT Serial
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
BlynkTimer timer;
char auth[] = "x"; //Auth code sent via Email
char ssid[] = "x"; //Wifi name
char pass[] = "x"; //Wifi Password
int flag=0;
void notifyOnFire()
{
int pinState = digitalRead(D1);
if (pinState==0 && flag==0) {
delay(4000);
int pinStateAgain = digitalRead(D1);
if (pinStateAgain==0) {
Serial.println("Alarm has gone off");
Blynk.notify("House Alarm!!!");
flag=1;
}
}
else if (pinState==1)
{
flag=0;
}
}
void setup()
{
Serial.begin(9600);
Blynk.begin(auth, ssid, pass);
pinMode(D1,INPUT_PULLUP);
timer.setInterval(1000L,notifyOnFire);
}
void loop()
{
//Serial.println(WiFi.localIP());
Blynk.run();
timer.run();
}

Answer 1

an easy fix would be to set the periodicity of the timer to be 4000L timer.setInterval(4000L,notifyOnFire); and in notifyOnFire use a static variable and toggle its value whenever notifyOnFire is called
void notifyOnFire()
{
static char state = 0;
if( state == 0)
{
/* Write here the code you need to be executed before the 4 sec delay */
state = 1;
}
else
{
/* Write here the code you need to be executed after the 4 sec delay */
state = 0;
}
}
The nice thing about static variables is that they are initialized only once at compile time and they retain their values after the scope of code changes (In this case function notifyOnFire exits).