package com.evsuite.abrp;

/**
 * Spots a double press of one steering-wheel key from the head unit's key broadcasts.
 *
 * The broadcast format is not documented, so this copes with all the shapes it could take:
 *  - no up/down information at all: every broadcast is one press;
 *  - separate down and up broadcasts: only releases count. If the meaning of the action field
 *    is the other way round, downs count instead — still exactly one per press, so a double
 *    press is found either way;
 *  - a long press resets, so holding the key never opens anything.
 *
 * Android-free and unit-tested; the window is longer than the stock 300 ms, because a
 * deliberate double press on a steering wheel is slower than one on a touch screen.
 */
final class DoublePressDetector {

    static final long WINDOW_MS = 500;

    private final int keyCode;
    private long lastPressAt = Long.MIN_VALUE;

    DoublePressDetector(int keyCode) {
        this.keyCode = keyCode;
    }

    /**
     * @param down true for a key-down, false for a release, null when the broadcast does not say
     * @param longPress true when the broadcast marks a long press
     * @return true exactly once per double press
     */
    synchronized boolean accept(int code, Boolean down, boolean longPress, long atMillis) {
        if (code != keyCode) return false;
        if (longPress) {
            lastPressAt = Long.MIN_VALUE;
            return false;
        }
        if (Boolean.TRUE.equals(down)) return false;
        if (lastPressAt != Long.MIN_VALUE && atMillis - lastPressAt <= WINDOW_MS) {
            lastPressAt = Long.MIN_VALUE; // a third press starts over
            return true;
        }
        lastPressAt = atMillis;
        return false;
    }
}