// https://forum.arduino.cc/t/stair-lights-with-pir-at-either-end/1280361

#include <FastLED.h>
#define NUM_LEDS 190
#define DATA_PIN 2
#define COLOR_ORDER GRB
#define CHIPSET WS2812B
#define BRIGHTNESS 255
CRGB leds[NUM_LEDS];

#define MOTION_SENSOR_1_PIN 12  // Arduino pin connected to the OUTPUT pin of motion sensor
#define MOTION_SENSOR_2_PIN 11
int motion_state_1 = LOW;       // current  state of motion sensor's pin
int motion_state_2 = LOW;
int prev_motion_state_1 = LOW;  // previous state of motion sensor's pin
int prev_motion_state_2 = LOW;  // previous state of motion sensor's pin

void setup() {
  Serial.begin(115200);
  FastLED.addLeds<CHIPSET, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS);
  FastLED.setBrightness(BRIGHTNESS);
  pinMode(MOTION_SENSOR_1_PIN, INPUT);  // set arduino pin to input mode
  pinMode(MOTION_SENSOR_2_PIN, INPUT);
}

void loop() {
  prev_motion_state_1 = motion_state_1;               // store old state
  prev_motion_state_2 = motion_state_2;               // store old state
  motion_state_1 = digitalRead(MOTION_SENSOR_1_PIN);  // read new state
  motion_state_2 = digitalRead(MOTION_SENSOR_2_PIN);

  if (prev_motion_state_1 == LOW && motion_state_1 == HIGH) {  // pin state change: LOW -> HIGH
    Serial.println("Motion (1) detected!");
    // turn on the led strip
    for (int i = 0; i < NUM_LEDS / 2 + 1; i++) {
      leds[NUM_LEDS / 2 + i] = CRGB::White;
      leds[(NUM_LEDS / 2) - 1 - i] = CRGB::White;
      FastLED.show();
      delay(10);
    }
  } else if (prev_motion_state_1 == HIGH && motion_state_1 == LOW) {  // pin state change: HIGH -> LOW
    Serial.println("Motion (1) stopped!");
    for (int j = 0; j < 255; j++) {
      for (int i = 0; i < NUM_LEDS; i++) {
        leds[i] = CRGB(255 - j, 255 - j, 255 - j);
      }
      FastLED.show();
    }
  }

  if (prev_motion_state_2 == LOW && motion_state_2 == HIGH) {  // pin state change: LOW -> HIGH
    Serial.println("Motion (2) detected!");
    // turn on the led strip
    for (int i = 0; i < NUM_LEDS / 2 + 1; i++) {
      leds[NUM_LEDS / 2 + i] = CRGB::White;
      leds[(NUM_LEDS / 2) - 1 - i] = CRGB::White;
      FastLED.show();
      delay(10);
    }
  } else if (prev_motion_state_2 == HIGH && motion_state_2 == LOW) {  // pin state change: HIGH -> LOW
    Serial.println("Motion (2) stopped!");
    for (int j = 0; j < 255; j++) {
      for (int i = 0; i < NUM_LEDS; i++) {
        leds[i] = CRGB(255 - j, 255 - j, 255 - j);
      }
      FastLED.show();
    }
  }
}