package com.cleverthis.interview;

import com.cleverthis.interview.padlock.PadlockImpl;

/**
 * The concrete implementation of PadlockAdapter that communicates with the padlock directly through a Java
 * class. This implementation also contains a cache that it keeps in sync with the underlying API, as a front-line
 * optimization against unnecessary write operations.
 */
public class PadlockJavaAdapter extends PadlockImpl implements PadlockAdapter {
    /**
     * Intermediate cache between the underlying padlock API and any code that interfaces with the PadlockAdapter
     * API.
     */
    private final Integer[] inputBufferState;

    /**
     * Create a padlock instance.
     *
     * @param numpadSize The number of buttons on the numpad of this lock.
     */
    public PadlockJavaAdapter(int numpadSize) {
        super(numpadSize);

        inputBufferState = new Integer[numpadSize];

        for(int i = 0; i < this.getNumpadSize(); i++) {
            inputBufferState[i] = i;
            super.writeInputBuffer(i, i);
        }
    }

    /**
     * Writes to the underlying input buffer, but only if the cache shows that the write is necessary
     * @param address The position / index of the button that is pressed. For example, address 0 is the first button pressed.
     * @param keyIndex The value of the button that is pressed. Cannot be greater than the numpad size, as the buttons increment
     *                 sequentially
     * @return The old value that was replaced, which is the same as keyIndex if a write operation doesn't actually occur.
     */
    @Override
    public Integer writeInputBuffer(int address, int keyIndex) {
        if(inputBufferState[address] != keyIndex) {
            inputBufferState[address] = keyIndex;
            return super.writeInputBuffer(address, keyIndex);
        } else {
            return keyIndex;
        }
    }
}