/*
 * Copyright (C) 2015 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#import "config.h"
#import "ApplicationStateTracker.h"

#if PLATFORM(IOS_FAMILY)

#import "AssertionServicesSPI.h"
#import "SandboxUtilities.h"
#import "UIKitSPI.h"
#import <wtf/ObjCRuntimeExtras.h>
#import <wtf/cocoa/Entitlements.h>
#import <wtf/spi/cocoa/SecuritySPI.h>

@interface UIWindow (WKDetails)
- (BOOL)_isHostedInAnotherProcess;
@end

namespace WebKit {

enum class ApplicationType {
    Application,
    ViewService,
    Extension,
};

static ApplicationType applicationType(UIWindow *window)
{
    ASSERT(window);

    if (_UIApplicationIsExtension())
        return ApplicationType::Extension;

    if (WTF::processHasEntitlement("com.apple.UIKit.vends-view-services") && window._isHostedInAnotherProcess)
        return ApplicationType::ViewService;

    return ApplicationType::Application;
}

static bool isBackgroundState(BKSApplicationState state)
{
    switch (state) {
    case BKSApplicationStateBackgroundRunning:
    case BKSApplicationStateBackgroundTaskSuspended:
        return true;

    default:
        return false;
    }
}

ApplicationStateTracker::ApplicationStateTracker(UIView *view, SEL didEnterBackgroundSelector, SEL didFinishSnapshottingAfterEnteringBackgroundSelector, SEL willEnterForegroundSelector)
    : m_view(view)
    , m_didEnterBackgroundSelector(didEnterBackgroundSelector)
    , m_didFinishSnapshottingAfterEnteringBackgroundSelector(didFinishSnapshottingAfterEnteringBackgroundSelector)
    , m_willEnterForegroundSelector(willEnterForegroundSelector)
    , m_isInBackground(true)
    , m_didEnterBackgroundObserver(nullptr)
    , m_didFinishSnapshottingAfterEnteringBackgroundObserver(nullptr)
    , m_willEnterForegroundObserver(nullptr)
{
    ASSERT([m_view.get() respondsToSelector:m_didEnterBackgroundSelector]);
    ASSERT([m_view.get() respondsToSelector:m_didFinishSnapshottingAfterEnteringBackgroundSelector]);
    ASSERT([m_view.get() respondsToSelector:m_willEnterForegroundSelector]);

    UIWindow *window = [m_view.get() window];
    ASSERT(window);

    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
    UIApplication *application = [UIApplication sharedApplication];

    auto weakThis = makeWeakPtr(*this);

    m_didFinishSnapshottingAfterEnteringBackgroundObserver = [notificationCenter addObserverForName:@"_UIApplicationDidFinishSuspensionSnapshotNotification" object:application queue:nil usingBlock:[weakThis](NSNotification *) {
        auto applicationStateTracker = weakThis.get();
        if (!applicationStateTracker)
            return;
        applicationStateTracker->applicationDidFinishSnapshottingAfterEnteringBackground();
    }];

    switch (applicationType(window)) {
    case ApplicationType::Application: {
        m_isInBackground = application.applicationState == UIApplicationStateBackground;

#if HAVE(UISCENE)
        m_didEnterBackgroundObserver = [notificationCenter addObserverForName:UISceneDidEnterBackgroundNotification object:window.windowScene queue:nil usingBlock:[this](NSNotification *) {
#else
        m_didEnterBackgroundObserver = [notificationCenter addObserverForName:UIApplicationDidEnterBackgroundNotification object:application queue:nil usingBlock:[this](NSNotification *) {
#endif
            applicationDidEnterBackground();
        }];

#if HAVE(UISCENE)
        m_willEnterForegroundObserver = [notificationCenter addObserverForName:UISceneWillEnterForegroundNotification object:window.windowScene queue:nil usingBlock:[this](NSNotification *) {
#else
        m_willEnterForegroundObserver = [notificationCenter addObserverForName:UIApplicationWillEnterForegroundNotification object:application queue:nil usingBlock:[this](NSNotification *) {
#endif
            applicationWillEnterForeground();
        }];
        break;
    }

    case ApplicationType::ViewService: {
        UIViewController *serviceViewController = nil;

        for (UIView *view = m_view.get().get(); view; view = view.superview) {
            UIViewController *viewController = [UIViewController viewControllerForView:view];

            if (viewController._hostProcessIdentifier) {
                serviceViewController = viewController;
                break;
            }
        }

        ASSERT(serviceViewController);

        pid_t applicationPID = serviceViewController._hostProcessIdentifier;
        ASSERT(applicationPID);

        auto applicationStateMonitor = adoptNS([[BKSApplicationStateMonitor alloc] init]);
        m_isInBackground = isBackgroundState([applicationStateMonitor mostElevatedApplicationStateForPID:applicationPID]);
        [applicationStateMonitor invalidate];

        // Workaround for <rdar://problem/34028921>. If the host application is StoreKitUIService then it is also a ViewService
        // and is always in the background. We need to treat StoreKitUIService as foreground for the purpose of process suspension
        // or its ViewServices will get suspended.
        if ([serviceViewController._hostApplicationBundleIdentifier isEqualToString:@"com.apple.ios.StoreKitUIService"])
            m_isInBackground = false;

        m_didEnterBackgroundObserver = [notificationCenter addObserverForName:@"_UIViewServiceHostDidEnterBackgroundNotification" object:serviceViewController queue:nil usingBlock:[this](NSNotification *) {
            applicationDidEnterBackground();
        }];
        m_willEnterForegroundObserver = [notificationCenter addObserverForName:@"_UIViewServiceHostWillEnterForegroundNotification" object:serviceViewController queue:nil usingBlock:[this](NSNotification *) {
            applicationWillEnterForeground();
        }];

        break;
    }

    case ApplicationType::Extension: {
        m_applicationStateMonitor = adoptNS([[BKSApplicationStateMonitor alloc] init]);

        m_isInBackground = isBackgroundState([m_applicationStateMonitor mostElevatedApplicationStateForPID:getpid()]);

        [m_applicationStateMonitor setHandler:[weakThis](NSDictionary *userInfo) {
            pid_t pid = [userInfo[BKSApplicationStateProcessIDKey] integerValue];
            if (pid != getpid())
                return;

            BKSApplicationState newState = (BKSApplicationState)[userInfo[BKSApplicationStateMostElevatedStateForProcessIDKey] unsignedIntValue];
            bool newInBackground = isBackgroundState(newState);

            dispatch_async(dispatch_get_main_queue(), [weakThis, newInBackground] {
                auto applicationStateTracker = weakThis.get();
                if (!applicationStateTracker)
                    return;

                if (!applicationStateTracker->m_isInBackground && newInBackground)
                    applicationStateTracker->applicationDidEnterBackground();
                else if (applicationStateTracker->m_isInBackground && !newInBackground)
                    applicationStateTracker->applicationWillEnterForeground();
            });
        }];
    }
    }
}

ApplicationStateTracker::~ApplicationStateTracker()
{
    if (m_applicationStateMonitor) {
        [m_applicationStateMonitor invalidate];
        return;
    }

    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
    [notificationCenter removeObserver:m_didEnterBackgroundObserver];
    [notificationCenter removeObserver:m_didFinishSnapshottingAfterEnteringBackgroundObserver];
    [notificationCenter removeObserver:m_willEnterForegroundObserver];
}

void ApplicationStateTracker::applicationDidEnterBackground()
{
    m_isInBackground = true;

    if (auto view = m_view.get())
        wtfObjCMsgSend<void>(view.get(), m_didEnterBackgroundSelector);
}

void ApplicationStateTracker::applicationDidFinishSnapshottingAfterEnteringBackground()
{
    if (auto view = m_view.get())
        wtfObjCMsgSend<void>(view.get(), m_didFinishSnapshottingAfterEnteringBackgroundSelector);
}

void ApplicationStateTracker::applicationWillEnterForeground()
{
    m_isInBackground = false;

    if (auto view = m_view.get())
        wtfObjCMsgSend<void>(view.get(), m_willEnterForegroundSelector);
}

}

#endif