adapting code to work with LDR

Hi,

I'm new to the arduino and I am trying to use the arduino UNO to open and close a gate, based on the amount of light.
So I found this code:

and I want to change the code so it will open and close by reading the value of a LDR.

I am still waiting for my arduino UNO to arrive, but thought I might as well do some coding up front, when it arrives
I think I best start with some examples found in the IDE program, but doing some of the code might help me learn faster.

I made some changes to the code and was wondering if anyone could check it to see if it will work the way I want to.
I replaced (or at least tried to..) the button-switch with code for the LDR.
here's the code I changed, please someone look over it and tell me where I've gone wrong, or not.

const int activate = 2; //D2 pin on arduino
const int gateOpen = 3; //D3 pin on arduino
const int gateClosed = 4; //D4 pin on arduino
const int bridgeOneA = 5; //D5 pin on arduino
const int bridgeTwoA = 6; //D6 pin on arduino
const int enable = 7; //A0 pin on arduino
const int statLED = 13; //D13 pin on arduino
const int ldr_pin = 0; //A0 pin on arduino
int ldr_value;
int ldr_cutoff = 400;  //ADC value, change from light to dark, vice versa
unsigned long currentTime = 0;
boolean gateState = false; //false = closed true = open
void setup() {
  Serial.begin(9600);
  pinMode(activate, INPUT); //set up I/O
  pinMode(gateOpen, INPUT);
  pinMode(gateClosed, INPUT);
  pinMode(bridgeOneA, OUTPUT);
  pinMode(bridgeTwoA, OUTPUT);
  pinMode(enable, OUTPUT);
  digitalWrite(enable, LOW); //make sure H-Bridge is off
  pinMode(statLED, OUTPUT); //setup our status LED
}
void loop() {
  ldr_value=analogRead(ldr_pin);
    if (ldr_value<ldr_cutoff) {
      (digitalRead(activate) == HIGH && gateState == false) { //check to see if the button is pressed and the gate is closed
      digitalWrite(enable, HIGH); //enable h-bridge
      digitalWrite(bridgeOneA, HIGH); //configure for CW rotation
      digitalWrite(bridgeTwoA, LOW);
      while(1){ //run motor until switch is tripped
        if (digitalRead(gateOpen) == LOW) { //check switch state
          gateState = true;
          digitalWrite(statLED, LOW); //turn off LED
          digitalWrite(enable, LOW); //disable h-bridge
          digitalWrite(bridgeOneA, LOW); //reset h-bridge config
          break;
        }
        if (millis() > currentTime + 500) { //flash status LED once
          digitalWrite(statLED, HIGH);
          delay(500);
          currentTime = millis();
        }
        else {
          digitalWrite(statLED, LOW);
        }
      }
    }
  }
  ldr_value=analogRead(ldr_pin);
    if (ldr_value>ldr_cutoff) {
      (digitalRead(activate) == HIGH && gateState == true) { //check to see if the button is pressed and the gate is open
      digitalWrite(enable, HIGH);
      digitalWrite(bridgeOneA, LOW); //configure for CCW rotation
      digitalWrite(bridgeTwoA, HIGH);
      while(1){
        if (digitalRead(gateOpen) == LOW) {
          gateState = false;
          digitalWrite(statLED, LOW);
          digitalWrite(enable, LOW);
          digitalWrite(bridgeTwoA, LOW);
          break;
        }
        if (millis() > currentTime + 500) { //flash status LED once
          digitalWrite(statLED, HIGH);
          delay(500);
          currentTime = millis();
        }
        else {
          digitalWrite(statLED, LOW);
        }
      }
    }
  }
}

Thanks for reading, and I hope someone can help me with verifying the code.

Do you expect people to somehow analyse your program to see if it will work ?

Wait until you get your Uno, and try it and see.

One comment: You need a different cutoff value for opening and closing. Otherwise, when the light is exactly at that value, it will try to open and close too often.

So if the light level is falling, you want to close the gate at 390 a/d counts, and don't open it until it rises to 410 counts.

No, I do not expect people to completely analyse my program, I'm already very happy you read my post and gave me a pointer about the cutoff value.
I know I have to wait for my UNO and test it myself, I already got my breadboard wired up and ready to go XD
but I am afraid that if the code has some serious errors I might blow up my new UNO, so just a quick look over is all I am asking for.

Thanks!