/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License
 */

package com.android.systemui.doze;

import android.os.Handler;
import android.view.Display;

/**
 * Controls the screen when dozing.
 */
public class DozeScreenState implements DozeMachine.Part {
    private final DozeMachine.Service mDozeService;
    private final Handler mHandler;
    private final Runnable mApplyPendingScreenState = this::applyPendingScreenState;

    private int mPendingScreenState = Display.STATE_UNKNOWN;

    public DozeScreenState(DozeMachine.Service service, Handler handler) {
        mDozeService = service;
        mHandler = handler;
    }

    @Override
    public void transitionTo(DozeMachine.State oldState, DozeMachine.State newState) {
        int screenState = newState.screenState();

        if (newState == DozeMachine.State.FINISH) {
            // Make sure not to apply the screen state after DozeService was destroyed.
            mPendingScreenState = Display.STATE_UNKNOWN;
            mHandler.removeCallbacks(mApplyPendingScreenState);

            applyScreenState(screenState);
            return;
        }

        if (screenState == Display.STATE_UNKNOWN) {
            // We'll keep it in the existing state
            return;
        }

        boolean messagePending = mHandler.hasCallbacks(mApplyPendingScreenState);
        if (messagePending || oldState == DozeMachine.State.INITIALIZED) {
            // During initialization, we hide the navigation bar. That is however only applied after
            // a traversal; setting the screen state here is immediate however, so it can happen
            // that the screen turns on again before the navigation bar is hidden. To work around
            // that, wait for a traversal to happen before applying the initial screen state.
            mPendingScreenState = screenState;
            if (!messagePending) {
                mHandler.post(mApplyPendingScreenState);
            }
            return;
        }
        applyScreenState(screenState);
    }

    private void applyPendingScreenState() {
        applyScreenState(mPendingScreenState);
        mPendingScreenState = Display.STATE_UNKNOWN;
    }

    private void applyScreenState(int screenState) {
        if (screenState != Display.STATE_UNKNOWN) {
            mDozeService.setDozeScreenState(screenState);
            mPendingScreenState = Display.STATE_UNKNOWN;
        }
    }
}