// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \example demos/android/feature-delivery
    \title Using Play Feature Delivery
    \ingroup android-platform-extra-topics
    \brief Showcases use of Google Play Feature Delivery on Qt.
    \meta {tag}{android}
    \image summermap-view.webp
           {Map loader app with Load Map, Change Map, and Remove Map buttons}

    This document describes the functionality of the Feature Delivery example.
    The example uses features supported since Qt 6.11.
    \br
    Play Feature Delivery can be used on older Qt versions, but creating the
    application requires manual addition of Android project and copying Qt
    binaries. Instructions for that are found in chapter
    \l{Feature Delivery on pre Qt 6.11}.

    \section1 What is Feature Delivery?

    Play Feature Delivery is a capability offered by Google which essentially
    allows developers to structure their projects in a way that the Google Play
    store can split their app content into several downloadable packages. It
    also gives developers control over how the content is delivered to users.
    These split software and content packages are delivered to the Google Play
    store using Android App Bundles (AAB).
    \l{https://developer.android.com/guide/playcore/feature-delivery}{Google's developer documentation}
    details this feature.

    \section1 Example project: Feature Delivery Map Loader

    This simple app uses Play Feature Delivery to serve images to a user when
    requested. The app can be easily modified to create an app that is over
    200MB to test the app size limits and download using a large Feature
    Delivery module.

    \section2 The App

    The application consists of a draggable view and four buttons.
    \list
      \li On Startup \uicontrol {Load Map} and \uicontrol {Show Map Info} buttons
      are enabled.
      \li When clicked \uicontrol {Show Map Info} button just shows that there are
      no information available.
      \li \uicontrol {Load Map} initiates loading of the feature module:
        \list 1
          \li Download pop-up is shown, from the pop-up the download can be
            canceled.
          \li When download completes the pop-up is removed and
          \li \uicontrol {Change Map} and \uicontrol {Remove Map} buttons are
            enabled.
        \endlist
      \li \uicontrol {Remove Map} button requests feature module to be
        uninstalled, disabling enabled buttons.
      \li When \uicontrol {Change Map} is clicked it opens a view where a map
        shown can be changed. In this example feature module consists of only
        one winter-themed map image.
    \endlist

    \section2 Source folder setup
    \list
        \li \b fdwintermapmodule: Feature Module
        \li \b fdmaploader: The main app
        \li \b fdmaploader/storeloader: Feature Delivery JNI interface
    \endlist

    \section2 Feature Delivery interface

    The \c{fdmaploader/storeloader} folder contains interface class
    \c{PlayStoreLoader} for the Feature Delivery API. The API is not complete,
    but contains relevant functions for loading and removing feature modules.
    Module loading is initiated with a call to \c{PlayStoreLoader::loadModule}.
    Status of the process can be monitored with signals provided by
    \c{PlayStoreLoaderHandler}. A handle to the callbacks can be obtained with
    \c{PlayStoreLoader::getHandler} function. The example API also provides a
    way to check already installed modules with
    \c{PlayStoreLoader::getInstalledModules} function and a option to remove
    installed modules with \c{PlayStoreLoader::uninstallModules}.

    This example is designed so that a developer can easily add their own
    content to test the Feature Delivery. To exceed the Play Store maximum
    package size, map images (It does not need to be map images, but it fits the
    theme of the example.) can be added to the images folders in \c fdmaploader
    and \c fdwintermapmodule, the image names must also be added to the
    \c images.qrc file.

    \section2 Under the hood

    The API module consists of two parts. Qt interface (\c{PlayStoreLoader} and
    \c{PlayStoreLoaderHandler}) and java classes that handle calling the
    \l{Android: Google Split Install Interfaces}. Qt interface works mostly as a
    passthrough for the java classes. Qt interface simplifies the API so,
    that when feature module is being loaded, Google \c{SplitCompat} and
    \c{SplitInstall} classes and listeners are created and released
    automatically. In this example parts of the APIs are left out, such
    as \c{deferredInstall} and language support.
    \br
    Qt creates and builds package suitable for Google Play deployment using
    \c{qt6_add_android_dynamic_features} when it is defined \c{CMakeLists}.

    \snippet demos/android/feature-delivery/fdmaploader/CMakeLists.txt Enable Feature Delivery

    CMake function \c{qt6_add_android_dynamic_features} adds the specific
    dynamic library as the dynamic feature for the Android application target.
    it requires QT_USE_ANDROID_MODERN_BUNDLE feature to be enabled. That can
    be done either as a compile-time flag or set in CMakeLists. The folder where
    the Java part of the interface resides is added to the build using
    \c{qt_add_android_dynamic_feature_java_source_dir}.

    On the Example app modules are loaded using \c{storeloader} interface. Qt
    \c{PlayStoreLoader} functions and \c{PlayStoreLoaderHandler} class work as
    an intermediate between the example code and Java.

    \snippet demos/android/feature-delivery/fdmaploader/storeloader/playstoreloader.cpp Load Module Implementation

    Java classes handle calls to the \c{Split Install} API.

    \snippet demos/android/feature-delivery/fdmaploader/storeloader/java/src/main/java/io/qt/fdmaploader/PlayStoreLoader.java Call To Split Install

    \section2 Creating Binaries

    Using command line a locally testable AAB package can be built.

    Create and enter a build directory to the same level with source directory:
    \code
    mkdir build-feature-delivery/ ; cd build-feature-delivery/
    \endcode
    Configure:
    \code
    path-to-qt-version/path-to-abi/bin/qt-cmake -GNinja -B . -S ../feature-delivery/ -DQT_USE_TARGET_ANDROID_BUILD_DIR=ON -DCMAKE_BUILD_TYPE=Debug
    \endcode
    Build:
    \code
    ninja aab
    \endcode

    \section2 Testing

    The built AAB can be tested locally by using \c bundletool with
    \c --local-testing parameter.
    \l{Android: Bundletool Documentation}
    The bundletool \c{build-apks} command creates apks file which then can be
    installed on a device or emulator with \c{install-apks} command

    \section3 Bundletool commands used

    Generate APK:s from a bundle:
    \code
    bundletool build-apks --bundle=/path/to/bundle.aab --output=/path/to/apk/package.apks --local-testing
    \endcode
    Install app to the device:
    \code
    bundletool install-apks --apks=/path/to/apk/package.apks
    \endcode

    \section2 Delivering to Play Store

    In order to be able to upload the created AAB package to the Google Play
    Store the package must be signed. For that \c{jarsigner} can be used. Below
    is an example jarsigner command to sign the AAB package. See
    \l{Android: Jarsigner Documentation}

    \code
    jarsigner -verbose -sigalg SHA256withRSA -digestalg SHA-256 -keystore [path-to-keystore-file].keystore [path-to-aab-file].aab [alias]
    \endcode

    \section1 Feature Delivery on pre Qt 6.11

    Versions prior Qt 6.11 does not support Google Play Store compatible package
    generation. If you are not able to use a Qt version 6.11 or later there is a
    way to use Google Play Feature Delivery, but it requires manual creation of
    the Android project, and copying of the Qt binaries to it. Rest of the
    document have instructions how to achieve that. The instructions may not be
    1-to-1 compatible for all environments, but should give good hints to
    achieve successful Feature Delivery implementation. It is advised to use the
    example as a basis.

    \section2 Feature Module

    Feature modules are build like normal libraries.

    \list
        \li Use Qt Creator to create a C++ shared library.
        \li Implement features and add resources.
        \li Build to create .so binaries.
    \endlist

    Feature Delivery handles C++ libraries like normal shared libraries that may
    or may not be available at runtime. Before calls to a library, the
    availability of one must be checked.

    \section2 Main App (Qt)
    \list
        \li Use Qt Creator to create an app (Qt Quick project template was used
        here).
        \li Implement access to the Feature Delivery library. The central class
        in Google Play Feature Delivery Java library is \l{Android: SplitInstallManager}.
        \li Android template files can be created by using the 'Create Templates' button on QtCreator
        \uicontrol{Projects -> Build&Run -> [target ABI] -> Build Steps -> Build Android APK}.
        Templates are created in the 'android' folder in the project.
        \li Add Java files to the folder \c .../android/src/java/[package...]
        and file paths to
        \c CMakeLists.txt:
        \code
        qt_add_executable...
        ...[path]/[java-filename.java]
        ...
        \endcode
        \li In the example, a Java class was created to handle the calls and
        callbacks. The Java class would then be accessed from Qt using JNI.
        \l{Android: Request an on demand module} section in the Android documentation has
        a simple description of how to request a module.
        \li When adding Java files under the android folder in the project,
        \l QT_ANDROID_PACKAGE_SOURCE_DIR property must be added to the
        \c CMakeLists.txt:
        \code
        ...
        set_property(TARGET appFDMainApp APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
                     ${CMAKE_CURRENT_SOURCE_DIR}/android)
        ...
        \endcode
        \li Also, the main app \c build.gradle must have dependencies for the
        feature API: in the dependencies block, replace
        \code
        implementation 'androidx.core:core:1.13.1'
        \endcode
        with
        \code
        implementation("com.google.android.play:feature-delivery:2.1.0")
        \endcode
        \li Implement access to the library provided by the feature module. As
        the Feature Module may or may not be available to the main app, modules
        are not linked at build time and calls to the module must be resolved at
        runtime.
        Example:

        \snippet demos/android/feature-delivery/fdmaploader/maploader.cpp Load Map Info

        \li Implement the user interface and other required parts of the main
        app.
    \endlist

    \section2 Feature Module (Qt)

    \list
        \li Use Qt Creator to create an app (Qt C++ Library project template was
        used).
        \li Implement features the module offers.
    \endlist

    \section2 Android Project (Android)

    Creating a project for building an Android app bundle for Feature Delivery
    is based on
    Android's documentation, mainly:
    \list
        \li \l {Android: Android Feature Delivery Documentation}
    \endlist

    Create an Android project manually or using Android Studio (Using the
    'No Activity' template). The project is modified so that it contains a
    top-level project and two sub-projects, \c app and \c feature-module. The
    Android Studio template creates the \c app sub-project and the
    \c feature-module can be added using \uicontrol{File -> New -> New Module}
    template.

    The template project requires several modifications:

    \list
        \li Add Feature Delivery plugin to the main level \c build.gradle:
        \code
        plugins {
            id 'com.android.application' version '8.5.2' apply false
            id 'com.android.dynamic-feature' version '8.5.2' apply false
            id 'com.android.library' version '8.5.2' apply false
        }
        \endcode
        \li Add feature module to the \c settings.gradle, change \c rootProject.name if needed:
        \code
        ...
        rootProject.name = "name-of-the-root-project"
        include(:app)
        include(:name-of-the-feature-module)
        \endcode
    \endlist

    \section3 app - Sub-project
    \list
        \li Android project requires Qt binaries from the Main App project:
            \list
                \li Copy native libraries in Qt build: \c [build directory]/android-build/libs/[target ABI]
                to \c app/src/main/jniLibs/[target ABI]
                \li Copy jars in \c [build directory]/android-build/libs/ to \c app/libs/
            \endlist
        \li From the Qt build, also contents of the \c res folder,
        \c AndroidManifest.xml, and \c local.properties are copied to respective
        places in the Android project.
        \li Add file \c feature_names.xml to the \c app/src/main/res/values
        folder containing a string for the feature module:
        \code
        <?xml version="1.0" encoding="utf-8"?>
        <resources>
            <string name="feature_module_name">name-of-the-feature-module-here</string>
        </resources>
        \endcode
        \li Add file \c keep.xml to \c app/src/main/res/raw folder containing:
        \code
        <?xml version="1.0" encoding="utf-8"?>
        <resources xmlns:tools="http://schemas.android.com/tools"
            tools:keep="@string/feature_module_winter_map"
            tools:discard="" />
        \endcode
    \endlist

    \section2 Modifications to app sub-project build files

    Build files copied to the Android project need some modifications.

    \section3 app - Sub-project

    \section4 build.gradle
    \list
        \li Remove \c buildScript and \c repositories blocks.
        \li Android block in main app's \c build.gradle requires some
        modifications:
            \list
                \li \c defaultConfig
                \li \c packagingOptions
                \li \c dynamicFeatures
                \li \c sourceSets
                \li \c aaptOptions
                \li \c dependencies
            \endlist
    \endlist

    \code
    android {
    ...
      defaultConfig {
      ...
        applicationId "your-project-name-here"
      ...
      }
      packagingOptions.jniLibs.useLegacyPackaging true

      dynamicFeatures = [":your-dynamic-feature-name-here"]

      sourceSets {
        main {
          manifest.srcFile 'src/main/AndroidManifest.xml'
          java.srcDirs = [qtAndroidDir + '/src', 'src', 'java']
          aidl.srcDirs = [qtAndroidDir + '/src', 'src', 'aidl']
          res.srcDirs = [qtAndroidDir + '/res', 'res']
          resources.srcDirs = ['resources']
          renderscript.srcDirs = ['src']
          assets.srcDirs = ['assets']
          jniLibs.srcDirs = ['src/main/jniLibs/']
        }
      }

      // Do not compress Qt binary resources file
      aaptOptions {
        noCompress 'rcc'
      }
    ...
    }

    dependencies {
    ...
      implementation fileTree(dir: 'libs', include: ['*.jar', '*.aar'])
      implementation 'com.google.android.play:feature-delivery:2.1.0'
      implementation libs.material
    ...
    }
    \endcode

    Also add signing configuration to android block:

    \code
    android {
    ...
      signingConfigs {
        release {
          storeFile file("/absolute/path/to/the/keystore.jks")
          storePassword "myStorePassword"
          keyAlias "myKeyAlias"
          keyPassword "myKeyPassword"
        }
      }
      buildTypes {
        release {
          signingConfig signingConfigs.release
          ...
        }
      }
    ...
    }
    \endcode

    \section4 gradle.properties

    Qt has added project variables to \c gradle.properties. Change the value of
   \c androidPackageName if needed.

    \section4 AndroidManifest.xml

    \list
        \li Remove \c package:
        \code
        ...
        <manifest
        ...
          android:package... <--remove
        ...
        >
        ...
        \endcode
        \li Change \c label and \c android.app.lib_name if needed:
        \code
        ...
        <application ...
          android:label=" ...
          <activity ... >
            <meta-data android:name="android.app.lib_name" android:value=" ...
            />
        ...
        \endcode
    \endlist

    \section3 feature-module - Sub-project

    App and feature modules are created as sub-projects for the top-level
    Android project. The folder and file structure is similar to the app
    sub-project.

    \list
        \li Feature-module binaries from the Qt build are copied to the
        \c [name-of-feature-module]/src/main/jniLibs/
        \li Like in the main app, \c src/main/res/ folder should have \c xml and
        \c values folders containing \c qtprovider_paths.xml and \c libs.xml
        respectively. Both files can be copied from the app project.
        \li If \c src/main/res/ folder contains drawable or mipmap folders and
        the feature does not require them, they can be removed.
        \li In the feature module \c src/main/res/values should not contain
        \c app_name field. In simple projects where strings.xml is not needed
        for other uses, it can be removed.
        \li \c libs.xml contains only the name of the feature module:
        \code
        ...
            <array name="load_local_libs">
                <item>name-of-the-feature-module-here</item>
            </array>

            <string name="static_init_classes"></string>
            <string name="use_local_qt_libs">0</string>
            <string name="bundle_local_qt_libs">0</string>
        ...
        \endcode
        \li \c AndroidManifest.xml is added to the \c src/main/ directory:
        \code
        <?xml version="1.0" encoding="utf-8"?>
        <manifest xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:dist="http://schemas.android.com/apk/distribution">

            <dist:module
                dist:instant="false"
                dist:title="@string/feature_module_title_string">
                <dist:delivery>
                    <dist:on-demand />
                </dist:delivery>
                <dist:fusing dist:include="false" />
            </dist:module>
            <!-- This feature module does contain code. -->
            <application android:hasCode="true"/>
        </manifest>
        \endcode
        \li Feature module \c build.gradle is quite similar to the one from the
        app project, with some changes. Here's an example:
        \code
        plugins {
            id 'com.android.dynamic-feature'
        }

        dependencies {
            implementation project(':app')
            implementation fileTree(dir: 'libs', include: ['*.jar', '*.aar'])
            implementation 'com.google.android.play:feature-delivery:2.1.0'
        }

        android {

            namespace = androidPackageName
            compileSdk = androidCompileSdkVersion
            ndkVersion androidNdkVersion

            // Extract native libraries from the APK
            packagingOptions.jniLibs.useLegacyPackaging true

            defaultConfig {
                minSdkVersion qtMinSdkVersion
                targetSdkVersion qtTargetSdkVersion
            }

            sourceSets {
                main {
                    manifest.srcFile 'src/main/AndroidManifest.xml'
                    resources.srcDirs = ['resources']
                    renderscript.srcDirs = ['src']
                    assets.srcDirs = ['assets']
                    jniLibs.srcDirs = ['src/main/jniLibs/']
               }
            }

            compileOptions {
                sourceCompatibility JavaVersion.VERSION_17
                targetCompatibility JavaVersion.VERSION_17
            }

            // Do not compress Qt binary resources file
            aaptOptions {
                noCompress 'rcc'
            }
        }
        \endcode
        \li \c gradle.properties file can be copied over from the app sub-project,
        change the \c androidPackageName to the feature module package.
    \endlist

    \section2 Building and deployment
    AAB bundle can be built from the command line using gradle wrapper:
    \c ./gradlew bundle
    The produced AAB will be in \c build/outputs/bundle/release (or \c debug)
    folder. The AAB can then be copied to the Google Play Store and released
    for testing. Testing can also be done locally by using \c bundletool with
    \c --local-testing parameter.
*/
