/*
 * Copyright 2018 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.lifecycle;

import static androidx.lifecycle.AbstractSavedStateViewModelFactory.TAG_SAVED_STATE_HANDLE_CONTROLLER;
import static androidx.lifecycle.SavedStateHandleController.attachHandleIfNeeded;

import android.annotation.SuppressLint;
import android.app.Application;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.savedstate.SavedStateRegistry;
import androidx.savedstate.SavedStateRegistryOwner;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.Arrays;

/**
 * {@link androidx.lifecycle.ViewModelProvider.Factory} that can create ViewModels accessing and
 * contributing to a saved state via {@link SavedStateHandle} received in a constructor.
 * If {@code defaultArgs} bundle was passed into the constructor, it will provide default
 * values in {@code SavedStateHandle}.
 * <p>
 * If ViewModel is instance of {@link androidx.lifecycle.AndroidViewModel}, it looks for a
 * constructor that receives an {@link Application} and {@link SavedStateHandle} (in this order),
 * otherwise it looks for a constructor that receives {@link SavedStateHandle} only.
 * {@link androidx.lifecycle.AndroidViewModel} is only supported if you pass a non-null
 * {@link Application} instance.
 */
public final class SavedStateViewModelFactory extends ViewModelProvider.KeyedFactory {
    private final Application mApplication;
    private final ViewModelProvider.Factory mFactory;
    private final Bundle mDefaultArgs;
    private final Lifecycle mLifecycle;
    private final SavedStateRegistry mSavedStateRegistry;

    /**
     * Creates {@link SavedStateViewModelFactory}.
     * <p>
     * {@link androidx.lifecycle.ViewModel} created with this factory can access to saved state
     * scoped to the given {@code activity}.
     *
     * @param application an application.  If null, {@link AndroidViewModel} instances will not be
     *                    supported.
     * @param owner       {@link SavedStateRegistryOwner} that will provide restored state for
     *                                                   created
     *                    {@link androidx.lifecycle.ViewModel ViewModels}
     */
    public SavedStateViewModelFactory(@Nullable  Application application,
            @NonNull SavedStateRegistryOwner owner) {
        this(application, owner, null);
    }

    /**
     * Creates {@link SavedStateViewModelFactory}.
     * <p>
     * {@link androidx.lifecycle.ViewModel} created with this factory can access to saved state
     * scoped to the given {@code activity}.
     *
     * @param application an application. If null, {@link AndroidViewModel} instances will not be
     *                   supported.
     * @param owner       {@link SavedStateRegistryOwner} that will provide restored state for
     *                                                   created
     *                    {@link androidx.lifecycle.ViewModel ViewModels}
     * @param defaultArgs values from this {@code Bundle} will be used as defaults by
     *                    {@link SavedStateHandle} if there is no previously saved state or
     *                    previously saved state
     *                    misses a value by such key.
     */
    @SuppressLint("LambdaLast")
    public SavedStateViewModelFactory(@Nullable Application application,
            @NonNull SavedStateRegistryOwner owner,
            @Nullable Bundle defaultArgs) {
        mSavedStateRegistry = owner.getSavedStateRegistry();
        mLifecycle = owner.getLifecycle();
        mDefaultArgs = defaultArgs;
        mApplication = application;
        mFactory = application != null
                ? ViewModelProvider.AndroidViewModelFactory.getInstance(application)
                : ViewModelProvider.NewInstanceFactory.getInstance();
    }

    @NonNull
    @Override
    public <T extends ViewModel> T create(@NonNull String key, @NonNull Class<T> modelClass) {
        boolean isAndroidViewModel = AndroidViewModel.class.isAssignableFrom(modelClass);
        Constructor<T> constructor;
        if (isAndroidViewModel && mApplication != null) {
            constructor = findMatchingConstructor(modelClass, ANDROID_VIEWMODEL_SIGNATURE);
        } else {
            constructor = findMatchingConstructor(modelClass, VIEWMODEL_SIGNATURE);
        }
        // doesn't need SavedStateHandle
        if (constructor == null) {
            return mFactory.create(modelClass);
        }

        SavedStateHandleController controller = SavedStateHandleController.create(
                mSavedStateRegistry, mLifecycle, key, mDefaultArgs);
        try {
            T viewmodel;
            if (isAndroidViewModel && mApplication != null) {
                viewmodel = constructor.newInstance(mApplication, controller.getHandle());
            } else {
                viewmodel = constructor.newInstance(controller.getHandle());
            }
            viewmodel.setTagIfAbsent(TAG_SAVED_STATE_HANDLE_CONTROLLER, controller);
            return viewmodel;
        } catch (IllegalAccessException e) {
            throw new RuntimeException("Failed to access " + modelClass, e);
        } catch (InstantiationException e) {
            throw new RuntimeException("A " + modelClass + " cannot be instantiated.", e);
        } catch (InvocationTargetException e) {
            throw new RuntimeException("An exception happened in constructor of "
                    + modelClass, e.getCause());
        }
    }

    @NonNull
    @Override
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
        // ViewModelProvider calls correct create that support same modelClass with different keys
        // If a developer manually calls this method, there is no "key" in picture, so factory
        // simply uses classname internally as as key.
        String canonicalName = modelClass.getCanonicalName();
        if (canonicalName == null) {
            throw new IllegalArgumentException("Local and anonymous classes can not be ViewModels");
        }
        return create(canonicalName, modelClass);
    }

    private static final Class<?>[] ANDROID_VIEWMODEL_SIGNATURE = new Class[]{Application.class,
            SavedStateHandle.class};
    private static final Class<?>[] VIEWMODEL_SIGNATURE = new Class[]{SavedStateHandle.class};

    @SuppressWarnings("unchecked")
    private static <T> Constructor<T> findMatchingConstructor(Class<T> modelClass,
            Class<?>[] signature) {
        for (Constructor<?> constructor : modelClass.getConstructors()) {
            Class<?>[] parameterTypes = constructor.getParameterTypes();
            if (Arrays.equals(signature, parameterTypes)) {
                return (Constructor<T>) constructor;
            }
        }
        return null;
    }

    @Override
    void onRequery(@NonNull ViewModel viewModel) {
        attachHandleIfNeeded(viewModel, mSavedStateRegistry, mLifecycle);
    }
}