/******************************************************************************
 *
 * File Name: Problem_4
 *
 * Author: Ahmed Abdelgleel
 *
 * Description:
 * This program simulates a traffic light system with pedestrian crossing support.
 * The system cycles through green, yellow, and red lights for vehicles.
 * Pedestrians can request to cross by pressing a button, which temporarily
 * overrides the traffic light sequence.
 *
 *******************************************************************************/

#include <TaskScheduler.h>

// TaskScheduler instance
Scheduler ts;

// Pin Definitions
const int redPin = 5;       // Red traffic light pin
const int yellowPin = 6;    // Yellow traffic light pin
const int greenPin = 7;     // Green traffic light pin
const int buttonPin = 2;    // Pedestrian button pin

// Pedestrian Request State
volatile bool pedestrianRequest = false; // Tracks if a pedestrian button is pressed

// Task Functions
/**
 * turnOnGreen:
 * Turns on the green traffic light and turns off others.
 */
void turnOnGreen() {
  digitalWrite(greenPin, HIGH);  // Green light ON
  digitalWrite(yellowPin, LOW);  // Yellow light OFF
  digitalWrite(redPin, LOW);     // Red light OFF
}

/**
 * turnOnYellow:
 * Turns on the yellow traffic light and turns off others.
 */
void turnOnYellow() {
  digitalWrite(greenPin, LOW);   // Green light OFF
  digitalWrite(yellowPin, HIGH); // Yellow light ON
  digitalWrite(redPin, LOW);     // Red light OFF
}

/**
 * turnOnRed:
 * Turns on the red traffic light and turns off others.
 */
void turnOnRed() {
  digitalWrite(greenPin, LOW);   // Green light OFF
  digitalWrite(yellowPin, LOW);  // Yellow light OFF
  digitalWrite(redPin, HIGH);    // Red light ON
}

/**
 * handlePedestrianRequest:
 * Handles pedestrian requests. When activated:
 * - The traffic light turns red.
 * - Pedestrians are given a 5-second crossing time.
 */
void handlePedestrianRequest() {
  if (pedestrianRequest) {
    turnOnRed();                  // Set traffic light to red
    delay(5000);                  // Allow 5 seconds for pedestrian crossing
    pedestrianRequest = false;    // Reset the request after handling
  }
}

// Define Tasks
Task tGreen(5000, TASK_FOREVER, &turnOnGreen, &ts);       // Green light stays for 5 seconds
Task tYellow(2000, TASK_FOREVER, &turnOnYellow, &ts);     // Yellow light stays for 2 seconds
Task tRed(5000, TASK_FOREVER, &turnOnRed, &ts);           // Red light stays for 5 seconds
Task tPedestrian(100, TASK_FOREVER, &handlePedestrianRequest, &ts); // Check pedestrian request every 100ms

void setup() {
  // Pin Setup
  pinMode(greenPin, OUTPUT);      // Set green light pin as output
  pinMode(yellowPin, OUTPUT);     // Set yellow light pin as output
  pinMode(redPin, OUTPUT);        // Set red light pin as output
  pinMode(buttonPin, INPUT_PULLUP); // Set button pin as input with internal pull-up

  // Interrupt Setup
  attachInterrupt(digitalPinToInterrupt(buttonPin), requestPedestrian, FALLING);

  // Task Initialization
  tGreen.enable();                     // Enable green light task
  tYellow.enableDelayed(5000);         // Yellow light starts after green
  tRed.enableDelayed(7000);            // Red light starts after green + yellow
  tPedestrian.enable();                // Enable pedestrian request handler
}

void loop() {
  // TaskScheduler execution
  ts.execute();
}

/**
 * requestPedestrian:
 * Interrupt Service Routine (ISR) triggered by button press.
 * Sets the pedestrianRequest flag to true.
 */
void requestPedestrian() {
  pedestrianRequest = true;
}