/*
 * Copyright (C) 2021 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 android.app;

import android.annotation.IntDef;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.content.res.XmlResourceParser;
import android.os.LocaleList;
import android.util.AttributeSet;
import android.util.Slog;
import android.util.Xml;

import com.android.internal.util.XmlUtils;

import org.xmlpull.v1.XmlPullParserException;

import java.io.IOException;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.HashSet;
import java.util.Set;

/**
 * The LocaleConfig of an application.
 * Defined in an XML resource file with an {@code <locale-config>} element and
 * referenced in the manifest via {@code android:localeConfig} on
 * {@code <application>}.
 *
 * <p>For more information, see
 * <a href="https://developer.android.com/about/versions/13/features/app-languages#use-localeconfig">
 * the section on per-app language preferences</a>.
 *
 * @attr ref android.R.styleable#LocaleConfig_Locale_name
 * @attr ref android.R.styleable#AndroidManifestApplication_localeConfig
 */
public class LocaleConfig {

    private static final String TAG = "LocaleConfig";
    public static final String TAG_LOCALE_CONFIG = "locale-config";
    public static final String TAG_LOCALE = "locale";
    private LocaleList mLocales;
    private int mStatus;

    /**
     * succeeded reading the LocaleConfig structure stored in an XML file.
     */
    public static final int STATUS_SUCCESS = 0;
    /**
     * No android:localeConfig tag on <application>.
     */
    public static final int STATUS_NOT_SPECIFIED = 1;
    /**
     * Malformed input in the XML file where the LocaleConfig was stored.
     */
    public static final int STATUS_PARSING_FAILED = 2;

    /** @hide */
    @IntDef(prefix = { "STATUS_" }, value = {
            STATUS_SUCCESS,
            STATUS_NOT_SPECIFIED,
            STATUS_PARSING_FAILED
    })
    @Retention(RetentionPolicy.SOURCE)
    public @interface Status{}

    /**
     * Returns the LocaleConfig for the provided application context
     *
     * @param context the context of the application
     *
     * @see Context#createPackageContext(String, int).
     */
    public LocaleConfig(@NonNull Context context) {
        int resId = 0;
        Resources res = context.getResources();
        try {
            //Get the resource id
            resId = new ApplicationInfo(context.getApplicationInfo()).getLocaleConfigRes();
            //Get the parser to read XML data
            XmlResourceParser parser = res.getXml(resId);
            parseLocaleConfig(parser, res);
        } catch (Resources.NotFoundException e) {
            Slog.w(TAG, "The resource file pointed to by the given resource ID isn't found.");
            mStatus = STATUS_NOT_SPECIFIED;
        } catch (XmlPullParserException | IOException e) {
            Slog.w(TAG, "Failed to parse XML configuration from "
                    + res.getResourceEntryName(resId), e);
            mStatus = STATUS_PARSING_FAILED;
        }
    }

    /**
     * Parse the XML content and get the locales supported by the application
     */
    private void parseLocaleConfig(XmlResourceParser parser, Resources res)
            throws IOException, XmlPullParserException {
        XmlUtils.beginDocument(parser, TAG_LOCALE_CONFIG);
        int outerDepth = parser.getDepth();
        AttributeSet attrs = Xml.asAttributeSet(parser);
        Set<String> localeNames = new HashSet<String>();
        while (XmlUtils.nextElementWithin(parser, outerDepth)) {
            if (TAG_LOCALE.equals(parser.getName())) {
                final TypedArray attributes = res.obtainAttributes(
                        attrs, com.android.internal.R.styleable.LocaleConfig_Locale);
                String nameAttr = attributes.getString(
                        com.android.internal.R.styleable.LocaleConfig_Locale_name);
                localeNames.add(nameAttr);
                attributes.recycle();
            } else {
                XmlUtils.skipCurrentTag(parser);
            }
        }
        mStatus = STATUS_SUCCESS;
        mLocales = LocaleList.forLanguageTags(String.join(",", localeNames));
    }

    /**
     * Returns the locales supported by the specified application.
     *
     * <p><b>Note:</b> The locale format should follow the
     * <a href="https://www.rfc-editor.org/rfc/bcp/bcp47.txt">IETF BCP47 regular expression</a>
     *
     * @return the {@link LocaleList}
     */
    public @Nullable LocaleList getSupportedLocales() {
        return mLocales;
    }

    /**
     * Get the status of reading the resource file where the LocaleConfig was stored.
     *
     * <p>Distinguish "the application didn't provide the resource file" from "the application
     * provided malformed input" if {@link #getSupportedLocales()} returns {@code null}.
     *
     * @return {@code STATUS_SUCCESS} if the LocaleConfig structure existed in an XML file was
     * successfully read, or {@code STATUS_NOT_SPECIFIED} if no android:localeConfig tag on
     * <application> pointing to an XML file that stores the LocaleConfig, or
     * {@code STATUS_PARSING_FAILED} if the application provided malformed input for the
     * LocaleConfig structure.
     *
     * @see #STATUS_SUCCESS
     * @see #STATUS_NOT_SPECIFIED
     * @see #STATUS_PARSING_FAILED
     *
     */
    public @Status int getStatus() {
        return mStatus;
    }
}