/*
 * Copyright 2020 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 androidx.car.app;

import static androidx.annotation.RestrictTo.Scope.LIBRARY;
import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;

import static java.util.Objects.requireNonNull;

import android.os.IInterface;
import android.os.RemoteException;
import android.util.Log;

import androidx.annotation.MainThread;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.car.app.CarContext.CarServiceType;
import androidx.car.app.constraints.IConstraintHost;
import androidx.car.app.media.IMediaPlaybackHost;
import androidx.car.app.navigation.INavigationHost;
import androidx.car.app.suggestion.ISuggestionHost;
import androidx.car.app.utils.LogTags;
import androidx.car.app.utils.RemoteUtils;
import androidx.car.app.utils.ThreadUtils;

import java.security.InvalidParameterException;

/**
 * Dispatches calls to the host and manages possible exceptions.
 */
@RestrictTo(LIBRARY_GROUP) // Restrict to testing library
public final class HostDispatcher {
    @Nullable
    private ICarHost mCarHost;
    @Nullable
    private IAppHost mAppHost;
    @Nullable
    private IConstraintHost mConstraintHost;
    @Nullable
    private INavigationHost mNavigationHost;
    @Nullable
    private ISuggestionHost mSuggestionHost;
    @Nullable
    private IMediaPlaybackHost mPlaybackMediaHost;

    /**
     * Dispatches the {@code call} to the host for the given {@code hostType}.
     *
     * @param hostType the service to dispatch to
     * @param callName the name of the call for logging purposes
     * @param call     the request to dispatch
     * @throws SecurityException if the host has thrown it
     * @throws HostException     if the host throws any exception other than
     *                           {@link SecurityException}
     */
    @Nullable
    @SuppressWarnings({"unchecked", "cast.unsafe"}) // Cannot check if instanceof ServiceT
    public <ServiceT, ReturnT> ReturnT dispatchForResult(
            @CarServiceType @NonNull String hostType, @NonNull String callName,
            @NonNull HostCall<ServiceT, ReturnT> call) throws RemoteException {
        return RemoteUtils.dispatchCallToHostForResult(callName, () -> {
            IInterface service = getHost(hostType);
            if (service == null) {
                Log.e(LogTags.TAG_DISPATCH,
                        "Could not retrieve host while dispatching call " + callName);
                return null;
            }
            return call.dispatch((ServiceT) service);
        });
    }

    /**
     * Dispatches the {@code call} to the host for the given {@code hostType}.
     *
     * @param hostType the service to dispatch to
     * @param callName the name of the call for logging purposes
     * @param call     the request to dispatch
     * @throws SecurityException if the host has thrown it
     * @throws HostException     if the host throws any exception other than
     *                           {@link SecurityException}
     */
    @SuppressWarnings({"unchecked", "cast.unsafe"}) // Cannot check if instanceof ServiceT
    public <ServiceT, ReturnT> void dispatch(
            @CarServiceType @NonNull String hostType, @NonNull String callName,
            @NonNull HostCall<ServiceT, ReturnT> call) {
        RemoteUtils.dispatchCallToHost(callName, () -> {
            IInterface service = getHost(hostType);
            if (service == null) {
                Log.e(LogTags.TAG_DISPATCH,
                        "Could not retrieve host while dispatching call " + callName);
                return null;
            }
            call.dispatch((ServiceT) service);
            return null;
        });
    }

    @MainThread
    public void setCarHost(@NonNull ICarHost carHost) {
        ThreadUtils.checkMainThread();

        resetHosts();
        mCarHost = carHost;
    }

    /** Removes references to remote services which are no longer valid. */
    @MainThread
    void resetHosts() {
        ThreadUtils.checkMainThread();

        mCarHost = null;
        mAppHost = null;
        mNavigationHost = null;
    }

    /**
     * Retrieves the {@link IInterface} for the given {@code hostType}.
     *
     * @throws RemoteException if the host is unresponsive
     */
    @SuppressWarnings({
            "UnsafeOptInUsageError"})
    @RestrictTo(LIBRARY)
    @Nullable
    IInterface getHost(@CarServiceType String hostType) throws RemoteException {
        if (mCarHost == null) {
            Log.e(LogTags.TAG_DISPATCH, "Host is not bound when attempting to retrieve host "
                    + "service");
            return null;
        }

        IInterface host;
        try {
            switch (hostType) {
                case CarContext.APP_SERVICE:
                    if (mAppHost == null) {
                        mAppHost =
                                RemoteUtils.dispatchCallToHostForResult("getHost(App)", () ->
                                        IAppHost.Stub.asInterface(requireNonNull(mCarHost).getHost(
                                                CarContext.APP_SERVICE)));
                    }
                    host = mAppHost;
                    break;
                case CarContext.CONSTRAINT_SERVICE:
                    if (mConstraintHost == null) {
                        mConstraintHost =
                                RemoteUtils.dispatchCallToHostForResult(
                                        "getHost(Constraints)", () ->
                                            IConstraintHost.Stub.asInterface(
                                                    requireNonNull(mCarHost).getHost(
                                                            CarContext.CONSTRAINT_SERVICE)));
                    }
                    host = mConstraintHost;
                    break;
                case CarContext.SUGGESTION_SERVICE:
                    if (mSuggestionHost == null) {
                        mSuggestionHost =
                                RemoteUtils.dispatchCallToHostForResult(
                                        "getHost(Suggestion)", () ->
                                                ISuggestionHost.Stub.asInterface(
                                                        requireNonNull(mCarHost).getHost(
                                                                CarContext.SUGGESTION_SERVICE))
                                );
                    }
                    host = mSuggestionHost;
                    break;
                case CarContext.MEDIA_PLAYBACK_SERVICE:
                    if (mPlaybackMediaHost == null) {
                        mPlaybackMediaHost =
                                RemoteUtils.dispatchCallToHostForResult(
                                        "getHost(Media)", () ->
                                                IMediaPlaybackHost.Stub.asInterface(
                                                        requireNonNull(mCarHost).getHost(
                                                                CarContext.MEDIA_PLAYBACK_SERVICE))
                                );
                    }
                    host = mPlaybackMediaHost;
                    break;
                case CarContext.NAVIGATION_SERVICE:
                    if (mNavigationHost == null) {
                        mNavigationHost =
                                RemoteUtils.dispatchCallToHostForResult(
                                        "getHost(Navigation)", () ->
                                                INavigationHost.Stub.asInterface(
                                                        requireNonNull(mCarHost).getHost(
                                                                CarContext.NAVIGATION_SERVICE))
                                );
                    }
                    host = mNavigationHost;
                    break;
                case CarContext.CAR_SERVICE:
                    host = mCarHost;
                    break;
                default:
                    throw new InvalidParameterException("Invalid host type: " + hostType);
            }
        } catch (HostException e) {
            Log.e(LogTags.TAG_DISPATCH, "Host threw an exception when attempting to retrieve "
                    + "host service");
            return null;
        }

        return host;
    }
}