/*
 * Copyright (C) 2017 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.provider;

import static java.lang.annotation.RetentionPolicy.SOURCE;

import android.annotation.IntDef;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.PackageManager;
import android.content.pm.ProviderInfo;
import android.content.pm.Signature;
import android.database.Cursor;
import android.graphics.Typeface;
import android.graphics.fonts.FontVariationAxis;
import android.net.Uri;
import android.os.Bundle;
import android.os.CancellationSignal;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.ParcelFileDescriptor;
import android.os.Process;
import android.os.ResultReceiver;
import android.util.ArraySet;
import android.util.Log;
import android.util.LruCache;

import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.Preconditions;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;

Utility class to deal with Font ContentProviders.
/**
 * Utility class to deal with Font ContentProviders.
 */
public class FontsContract {
    private static final String TAG = "FontsContract";

    
Defines the constants used in a response from a Font Provider. The cursor returned from the
query should have the ID column populated with the content uri ID for the resulting font.
This should point to a real file or shared memory, as the client will mmap the given file
descriptor. Pipes, sockets and other non-mmap-able file descriptors will fail to load in the
client application.
/**
     * Defines the constants used in a response from a Font Provider. The cursor returned from the
     * query should have the ID column populated with the content uri ID for the resulting font.
     * This should point to a real file or shared memory, as the client will mmap the given file
     * descriptor. Pipes, sockets and other non-mmap-able file descriptors will fail to load in the
     * client application.
     */
    public static final class Columns implements BaseColumns {

        // Do not instantiate.
        private Columns() {}

        
Constant used to request data from a font provider. The cursor returned from the query
may populate this column with a long for the font file ID. The client will request a file
descriptor to "file/FILE_ID" with this ID immediately under the top-level content URI. If
not present, the client will request a file descriptor to the top-level URI with the
given base font ID. Note that several results may return the same file ID, e.g. for TTC
files with different indices.
/**
         * Constant used to request data from a font provider. The cursor returned from the query
         * may populate this column with a long for the font file ID. The client will request a file
         * descriptor to "file/FILE_ID" with this ID immediately under the top-level content URI. If
         * not present, the client will request a file descriptor to the top-level URI with the
         * given base font ID. Note that several results may return the same file ID, e.g. for TTC
         * files with different indices.
         */
        public static final String FILE_ID = "file_id";
        
Constant used to request data from a font provider. The cursor returned from the query
should have this column populated with an int for the ttc index for the resulting font.
/**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated with an int for the ttc index for the resulting font.
         */
        public static final String TTC_INDEX = "font_ttc_index";
        
Constant used to request data from a font provider. The cursor returned from the query
may populate this column with the font variation settings String information for the
font.
/**
         * Constant used to request data from a font provider. The cursor returned from the query
         * may populate this column with the font variation settings String information for the
         * font.
         */
        public static final String VARIATION_SETTINGS = "font_variation_settings";
        
Constant used to request data from a font provider. The cursor returned from the query
should have this column populated with the int weight for the resulting font. This value
should be between 100 and 900. The most common values are 400 for regular weight and 700
for bold weight.
/**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated with the int weight for the resulting font. This value
         * should be between 100 and 900. The most common values are 400 for regular weight and 700
         * for bold weight.
         */
        public static final String WEIGHT = "font_weight";
        
Constant used to request data from a font provider. The cursor returned from the query
should have this column populated with the int italic for the resulting font. This should
be 0 for regular style and 1 for italic.
/**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated with the int italic for the resulting font. This should
         * be 0 for regular style and 1 for italic.
         */
        public static final String ITALIC = "font_italic";
        
Constant used to request data from a font provider. The cursor returned from the query should have this column populated to indicate the result status of the query. This will be checked before any other data in the cursor. Possible values are RESULT_CODE_OK, RESULT_CODE_FONT_NOT_FOUND, RESULT_CODE_MALFORMED_QUERY and RESULT_CODE_FONT_UNAVAILABLE for system defined values. You may also define your own values in the 0x000010000..0xFFFF0000 range. If not present, RESULT_CODE_OK will be assumed. /**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated to indicate the result status of the
         * query. This will be checked before any other data in the cursor. Possible values are
         * {@link #RESULT_CODE_OK}, {@link #RESULT_CODE_FONT_NOT_FOUND},
         * {@link #RESULT_CODE_MALFORMED_QUERY} and {@link #RESULT_CODE_FONT_UNAVAILABLE} for system
         * defined values. You may also define your own values in the 0x000010000..0xFFFF0000 range.
         * If not present, {@link #RESULT_CODE_OK} will be assumed.
         */
        public static final String RESULT_CODE = "result_code";

        
Constant used to represent a result was retrieved successfully. The given fonts will be attempted to retrieve immediately via ContentProvider.openFile(Uri, String). See RESULT_CODE. /**
         * Constant used to represent a result was retrieved successfully. The given fonts will be
         * attempted to retrieve immediately via
         * {@link android.content.ContentProvider#openFile(Uri, String)}. See {@link #RESULT_CODE}.
         */
        public static final int RESULT_CODE_OK = 0;
        
Constant used to represent a result was not found. See RESULT_CODE. /**
         * Constant used to represent a result was not found. See {@link #RESULT_CODE}.
         */
        public static final int RESULT_CODE_FONT_NOT_FOUND = 1;
        
Constant used to represent a result was found, but cannot be provided at this moment. Use this to indicate, for example, that a font needs to be fetched from the network. See RESULT_CODE. /**
         * Constant used to represent a result was found, but cannot be provided at this moment. Use
         * this to indicate, for example, that a font needs to be fetched from the network. See
         * {@link #RESULT_CODE}.
         */
        public static final int RESULT_CODE_FONT_UNAVAILABLE = 2;
        
Constant used to represent that the query was not in a supported format by the provider. See RESULT_CODE. /**
         * Constant used to represent that the query was not in a supported format by the provider.
         * See {@link #RESULT_CODE}.
         */
        public static final int RESULT_CODE_MALFORMED_QUERY = 3;
    }

    private static final Object sLock = new Object();
    @GuardedBy("sLock")
    private static Handler sHandler;
    @GuardedBy("sLock")
    private static HandlerThread sThread;
    @GuardedBy("sLock")
    private static Set<String> sInQueueSet;

    private volatile static Context sContext;  // set once in setApplicationContextForResources

    private static final LruCache<String, Typeface> sTypefaceCache = new LruCache<>(16);

    private FontsContract() {
    }

    
@hide
/** @hide */
    public static void setApplicationContextForResources(Context context) {
        sContext = context.getApplicationContext();
    }

    
Object represent a font entry in the family returned from fetchFonts. /**
     * Object represent a font entry in the family returned from {@link #fetchFonts}.
     */
    public static class FontInfo {
        private final Uri mUri;
        private final int mTtcIndex;
        private final FontVariationAxis[] mAxes;
        private final int mWeight;
        private final boolean mItalic;
        private final int mResultCode;

        /**
         * Creates a Font with all the information needed about a provided font.
         * @param uri A URI associated to the font file.
         * @param ttcIndex If providing a TTC_INDEX file, the index to point to. Otherwise, 0.
         * @param axes If providing a variation font, the settings for it. May be null.
         * @param weight An integer that indicates the font weight.
         * @param italic A boolean that indicates the font is italic style or not.
         * @param resultCode A boolean that indicates the font contents is ready.
         */
        
@hide
/** @hide */
        public FontInfo(@NonNull Uri uri, @IntRange(from = 0) int ttcIndex,
                @Nullable FontVariationAxis[] axes, @IntRange(from = 1, to = 1000) int weight,
                boolean italic, int resultCode) {
            mUri = Preconditions.checkNotNull(uri);
            mTtcIndex = ttcIndex;
            mAxes = axes;
            mWeight = weight;
            mItalic = italic;
            mResultCode = resultCode;
        }

        
Returns a URI associated to this record.
/**
         * Returns a URI associated to this record.
         */
        public @NonNull Uri getUri() {
            return mUri;
        }

        
Returns the index to be used to access this font when accessing a TTC file.
/**
         * Returns the index to be used to access this font when accessing a TTC file.
         */
        public @IntRange(from = 0) int getTtcIndex() {
            return mTtcIndex;
        }

        
Returns the list of axes associated to this font.
/**
         * Returns the list of axes associated to this font.
         */
        public @Nullable FontVariationAxis[] getAxes() {
            return mAxes;
        }

        
Returns the weight value for this font.
/**
         * Returns the weight value for this font.
         */
        public @IntRange(from = 1, to = 1000) int getWeight() {
            return mWeight;
        }

        
Returns whether this font is italic.
/**
         * Returns whether this font is italic.
         */
        public boolean isItalic() {
            return mItalic;
        }

        
Returns result code. Columns.RESULT_CODE /**
         * Returns result code.
         *
         * {@link FontsContract.Columns#RESULT_CODE}
         */
        public int getResultCode() {
            return mResultCode;
        }
    }

    
Object returned from fetchFonts. /**
     * Object returned from {@link #fetchFonts}.
     */
    public static class FontFamilyResult {
        
Constant represents that the font was successfully retrieved. Note that when this value is set and getFonts returns an empty array, it means there were no fonts matching the given query. /**
         * Constant represents that the font was successfully retrieved. Note that when this value
         * is set and {@link #getFonts} returns an empty array, it means there were no fonts
         * matching the given query.
         */
        public static final int STATUS_OK = 0;

        
Constant represents that the given certificate was not matched with the provider's signature. getFonts returns null if this status was set. /**
         * Constant represents that the given certificate was not matched with the provider's
         * signature. {@link #getFonts} returns null if this status was set.
         */
        public static final int STATUS_WRONG_CERTIFICATES = 1;

        
Constant represents that the provider returns unexpected data. getFonts returns null if this status was set. For example, this value is set when the font provider gives invalid format of variation settings. /**
         * Constant represents that the provider returns unexpected data. {@link #getFonts} returns
         * null if this status was set. For example, this value is set when the font provider
         * gives invalid format of variation settings.
         */
        public static final int STATUS_UNEXPECTED_DATA_PROVIDED = 2;

        
Constant represents that the fetching font data was rejected by system. This happens if
the passed context is restricted.
/**
         * Constant represents that the fetching font data was rejected by system. This happens if
         * the passed context is restricted.
         */
        public static final int STATUS_REJECTED = 3;

        
@hide
/** @hide */
        @IntDef(prefix = { "STATUS_" }, value = {
                STATUS_OK,
                STATUS_WRONG_CERTIFICATES,
                STATUS_UNEXPECTED_DATA_PROVIDED
        })
        @Retention(RetentionPolicy.SOURCE)
        @interface FontResultStatus {}

        private final @FontResultStatus int mStatusCode;
        private final FontInfo[] mFonts;

        
@hide
/** @hide */
        public FontFamilyResult(@FontResultStatus int statusCode, @Nullable FontInfo[] fonts) {
            mStatusCode = statusCode;
            mFonts = fonts;
        }

        public @FontResultStatus int getStatusCode() {
            return mStatusCode;
        }

        public @NonNull FontInfo[] getFonts() {
            return mFonts;
        }
    }

    private static final int THREAD_RENEWAL_THRESHOLD_MS = 10000;

    private static final long SYNC_FONT_FETCH_TIMEOUT_MS = 500;

    // We use a background thread to post the content resolving work for all requests on. This
    // thread should be quit/stopped after all requests are done.
    // TODO: Factor out to other class. Consider to switch MessageQueue.IdleHandler.
    private static final Runnable sReplaceDispatcherThreadRunnable = new Runnable() {
        @Override
        public void run() {
            synchronized (sLock) {
                if (sThread != null) {
                    sThread.quitSafely();
                    sThread = null;
                    sHandler = null;
                }
            }
        }
    };

    
@hide
/** @hide */
    public static Typeface getFontSync(FontRequest request) {
        final String id = request.getIdentifier();
        Typeface cachedTypeface = sTypefaceCache.get(id);
        if (cachedTypeface != null) {
            return cachedTypeface;
        }

        // Unfortunately the typeface is not available at this time, but requesting from the font
        // provider takes too much time. For now, request the font data to ensure it is in the cache
        // next time and return.
        synchronized (sLock) {
            if (sHandler == null) {
                sThread = new HandlerThread("fonts", Process.THREAD_PRIORITY_BACKGROUND);
                sThread.start();
                sHandler = new Handler(sThread.getLooper());
            }
            final Lock lock = new ReentrantLock();
            final Condition cond = lock.newCondition();
            final AtomicReference<Typeface> holder = new AtomicReference<>();
            final AtomicBoolean waiting = new AtomicBoolean(true);
            final AtomicBoolean timeout = new AtomicBoolean(false);

            sHandler.post(() -> {
                try {
                    FontFamilyResult result = fetchFonts(sContext, null, request);
                    if (result.getStatusCode() == FontFamilyResult.STATUS_OK) {
                        Typeface typeface = buildTypeface(sContext, null, result.getFonts());
                        if (typeface != null) {
                            sTypefaceCache.put(id, typeface);
                        }
                        holder.set(typeface);
                    }
                } catch (NameNotFoundException e) {
                    // Ignore.
                }
                lock.lock();
                try {
                    if (!timeout.get()) {
                      waiting.set(false);
                      cond.signal();
                    }
                } finally {
                    lock.unlock();
                }
            });
            sHandler.removeCallbacks(sReplaceDispatcherThreadRunnable);
            sHandler.postDelayed(sReplaceDispatcherThreadRunnable, THREAD_RENEWAL_THRESHOLD_MS);

            long remaining = TimeUnit.MILLISECONDS.toNanos(SYNC_FONT_FETCH_TIMEOUT_MS);
            lock.lock();
            try {
                if (!waiting.get()) {
                    return holder.get();
                }
                for (;;) {
                    try {
                        remaining = cond.awaitNanos(remaining);
                    } catch (InterruptedException e) {
                        // do nothing.
                    }
                    if (!waiting.get()) {
                        return holder.get();
                    }
                    if (remaining <= 0) {
                        timeout.set(true);
                        Log.w(TAG, "Remote font fetch timed out: " +
                                request.getProviderAuthority() + "/" + request.getQuery());
                        return null;
                    }
                }
            } finally {
                lock.unlock();
            }
        }
    }

    
Interface used to receive asynchronously fetched typefaces.
/**
     * Interface used to receive asynchronously fetched typefaces.
     */
    public static class FontRequestCallback {
        
Constant returned by onTypefaceRequestFailed(int) signaling that the given provider was not found on the device. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the given
         * provider was not found on the device.
         */
        public static final int FAIL_REASON_PROVIDER_NOT_FOUND = -1;
        
Constant returned by onTypefaceRequestFailed(int) signaling that the given provider must be authenticated and the given certificates do not match its signature. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the given
         * provider must be authenticated and the given certificates do not match its signature.
         */
        public static final int FAIL_REASON_WRONG_CERTIFICATES = -2;
        
Constant returned by onTypefaceRequestFailed(int) signaling that the font returned by the provider was not loaded properly. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the font
         * returned by the provider was not loaded properly.
         */
        public static final int FAIL_REASON_FONT_LOAD_ERROR = -3;
        
Constant returned by onTypefaceRequestFailed(int) signaling that the font provider did not return any results for the given query. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the font
         * provider did not return any results for the given query.
         */
        public static final int FAIL_REASON_FONT_NOT_FOUND = Columns.RESULT_CODE_FONT_NOT_FOUND;
        
Constant returned by onTypefaceRequestFailed(int) signaling that the font provider found the queried font, but it is currently unavailable. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the font
         * provider found the queried font, but it is currently unavailable.
         */
        public static final int FAIL_REASON_FONT_UNAVAILABLE = Columns.RESULT_CODE_FONT_UNAVAILABLE;
        
Constant returned by onTypefaceRequestFailed(int) signaling that the given query was not supported by the provider. /**
         * Constant returned by {@link #onTypefaceRequestFailed(int)} signaling that the given
         * query was not supported by the provider.
         */
        public static final int FAIL_REASON_MALFORMED_QUERY = Columns.RESULT_CODE_MALFORMED_QUERY;

        
@hide
/** @hide */
        @IntDef(prefix = { "FAIL_" }, value = {
                FAIL_REASON_PROVIDER_NOT_FOUND,
                FAIL_REASON_FONT_LOAD_ERROR,
                FAIL_REASON_FONT_NOT_FOUND,
                FAIL_REASON_FONT_UNAVAILABLE,
                FAIL_REASON_MALFORMED_QUERY
        })
        @Retention(RetentionPolicy.SOURCE)
        @interface FontRequestFailReason {}

        public FontRequestCallback() {}

        
Called then a Typeface request done via requestFonts is complete. Note that this method will not be called if onTypefaceRequestFailed(int) is called instead. 
Params:
typeface –  The Typeface object retrieved./**
         * Called then a Typeface request done via {@link #requestFonts} is complete. Note that this
         * method will not be called if {@link #onTypefaceRequestFailed(int)} is called instead.
         * @param typeface  The Typeface object retrieved.
         */
        public void onTypefaceRetrieved(Typeface typeface) {}

        
Called when a Typeface request done via requestFonts} fails. 
Params:
reason – One of FAIL_REASON_PROVIDER_NOT_FOUND, FAIL_REASON_FONT_NOT_FOUND, FAIL_REASON_FONT_LOAD_ERROR, FAIL_REASON_FONT_UNAVAILABLE or FAIL_REASON_MALFORMED_QUERY if returned by the system. May also be a positive value greater than 0 defined by the font provider as an additional error code. Refer to the provider's documentation for more information on possible returned error codes./**
         * Called when a Typeface request done via {@link #requestFonts}} fails.
         * @param reason One of {@link #FAIL_REASON_PROVIDER_NOT_FOUND},
         *               {@link #FAIL_REASON_FONT_NOT_FOUND},
         *               {@link #FAIL_REASON_FONT_LOAD_ERROR},
         *               {@link #FAIL_REASON_FONT_UNAVAILABLE} or
         *               {@link #FAIL_REASON_MALFORMED_QUERY} if returned by the system. May also be
         *               a positive value greater than 0 defined by the font provider as an
         *               additional error code. Refer to the provider's documentation for more
         *               information on possible returned error codes.
         */
        public void onTypefaceRequestFailed(@FontRequestFailReason int reason) {}
    }

    
Create a typeface object given a font request. The font will be asynchronously fetched, therefore the result is delivered to the given callback. See FontRequest. Only one of the methods in callback will be invoked, depending on whether the request succeeds or fails. These calls will happen on the caller thread. Note that the result Typeface may be cached internally and the same instance will be returned the next time you call this method with the same request. If you want to bypass this cache, use fetchFonts and buildTypeface instead. 
Params:
context – A context to be used for fetching from font provider.
request – A FontRequest object that identifies the provider and query for the request. May not be null.
handler – A handler to be processed the font fetching.
cancellationSignal – A signal to cancel the operation in progress, or null if none. If the operation is canceled, then OperationCanceledException will be thrown.
callback – A callback that will be triggered when results are obtained. May not be null./**
     * Create a typeface object given a font request. The font will be asynchronously fetched,
     * therefore the result is delivered to the given callback. See {@link FontRequest}.
     * Only one of the methods in callback will be invoked, depending on whether the request
     * succeeds or fails. These calls will happen on the caller thread.
     *
     * Note that the result Typeface may be cached internally and the same instance will be returned
     * the next time you call this method with the same request. If you want to bypass this cache,
     * use {@link #fetchFonts} and {@link #buildTypeface} instead.
     *
     * @param context A context to be used for fetching from font provider.
     * @param request A {@link FontRequest} object that identifies the provider and query for the
     *                request. May not be null.
     * @param handler A handler to be processed the font fetching.
     * @param cancellationSignal A signal to cancel the operation in progress, or null if none. If
     *                           the operation is canceled, then {@link
     *                           android.os.OperationCanceledException} will be thrown.
     * @param callback A callback that will be triggered when results are obtained. May not be null.
     */
    public static void requestFonts(@NonNull Context context, @NonNull FontRequest request,
            @NonNull Handler handler, @Nullable CancellationSignal cancellationSignal,
            @NonNull FontRequestCallback callback) {

        final Handler callerThreadHandler = new Handler();
        final Typeface cachedTypeface = sTypefaceCache.get(request.getIdentifier());
        if (cachedTypeface != null) {
            callerThreadHandler.post(() -> callback.onTypefaceRetrieved(cachedTypeface));
            return;
        }

        handler.post(() -> {
            FontFamilyResult result;
            try {
                result = fetchFonts(context, cancellationSignal, request);
            } catch (NameNotFoundException e) {
                callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                        FontRequestCallback.FAIL_REASON_PROVIDER_NOT_FOUND));
                return;
            }

            // Same request might be dispatched during fetchFonts. Check the cache again.
            final Typeface anotherCachedTypeface = sTypefaceCache.get(request.getIdentifier());
            if (anotherCachedTypeface != null) {
                callerThreadHandler.post(() -> callback.onTypefaceRetrieved(anotherCachedTypeface));
                return;
            }

            if (result.getStatusCode() != FontFamilyResult.STATUS_OK) {
                switch (result.getStatusCode()) {
                    case FontFamilyResult.STATUS_WRONG_CERTIFICATES:
                        callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                                FontRequestCallback.FAIL_REASON_WRONG_CERTIFICATES));
                        return;
                    case FontFamilyResult.STATUS_UNEXPECTED_DATA_PROVIDED:
                        callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                                FontRequestCallback.FAIL_REASON_FONT_LOAD_ERROR));
                        return;
                    default:
                        // fetchFont returns unexpected status type. Fallback to load error.
                        callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                                FontRequestCallback.FAIL_REASON_FONT_LOAD_ERROR));
                        return;
                }
            }

            final FontInfo[] fonts = result.getFonts();
            if (fonts == null || fonts.length == 0) {
                callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                        FontRequestCallback.FAIL_REASON_FONT_NOT_FOUND));
                return;
            }
            for (final FontInfo font : fonts) {
                if (font.getResultCode() != Columns.RESULT_CODE_OK) {
                    // We proceed if all font entry is ready to use. Otherwise report the first
                    // error.
                    final int resultCode = font.getResultCode();
                    if (resultCode < 0) {
                        // Negative values are reserved for internal errors. Fallback to load error.
                        callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                                FontRequestCallback.FAIL_REASON_FONT_LOAD_ERROR));
                    } else {
                        callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                                resultCode));
                    }
                    return;
                }
            }

            final Typeface typeface = buildTypeface(context, cancellationSignal, fonts);
            if (typeface == null) {
                // Something went wrong during reading font files. This happens if the given font
                // file is an unsupported font type.
                callerThreadHandler.post(() -> callback.onTypefaceRequestFailed(
                        FontRequestCallback.FAIL_REASON_FONT_LOAD_ERROR));
                return;
            }

            sTypefaceCache.put(request.getIdentifier(), typeface);
            callerThreadHandler.post(() -> callback.onTypefaceRetrieved(typeface));
        });
    }

    
Fetch fonts given a font request.
Params:
context – A Context to be used for fetching fonts.
cancellationSignal – A signal to cancel the operation in progress, or null if none. If the operation is canceled, then OperationCanceledException will be thrown when the query is executed.
request – A FontRequest object that identifies the provider and query for the request.
Throws:
NameNotFoundException – If requested package or authority was not found in system.
Returns:
FontFamilyResult/**
     * Fetch fonts given a font request.
     *
     * @param context A {@link Context} to be used for fetching fonts.
     * @param cancellationSignal A signal to cancel the operation in progress, or null if none. If
     *                           the operation is canceled, then {@link
     *                           android.os.OperationCanceledException} will be thrown when the
     *                           query is executed.
     * @param request A {@link FontRequest} object that identifies the provider and query for the
     *                request.
     *
     * @return {@link FontFamilyResult}
     *
     * @throws NameNotFoundException If requested package or authority was not found in system.
     */
    public static @NonNull FontFamilyResult fetchFonts(
            @NonNull Context context, @Nullable CancellationSignal cancellationSignal,
            @NonNull FontRequest request) throws NameNotFoundException {
        if (context.isRestricted()) {
            // TODO: Should we allow if the peer process is system or myself?
            return new FontFamilyResult(FontFamilyResult.STATUS_REJECTED, null);
        }
        ProviderInfo providerInfo = getProvider(context.getPackageManager(), request);
        if (providerInfo == null) {
            return new FontFamilyResult(FontFamilyResult.STATUS_WRONG_CERTIFICATES, null);

        }
        try {
            FontInfo[] fonts = getFontFromProvider(
                    context, request, providerInfo.authority, cancellationSignal);
            return new FontFamilyResult(FontFamilyResult.STATUS_OK, fonts);
        } catch (IllegalArgumentException e) {
            return new FontFamilyResult(FontFamilyResult.STATUS_UNEXPECTED_DATA_PROVIDED, null);
        }
    }

    
Build a Typeface from an array of FontInfo Results that are marked as not ready will be skipped. 
Params:
context – A Context that will be used to fetch the font contents.
cancellationSignal – A signal to cancel the operation in progress, or null if none. If the operation is canceled, then OperationCanceledException will be thrown.
fonts – An array of FontInfo to be used to create a Typeface.
Returns:
A Typeface object. Returns null if typeface creation fails./**
     * Build a Typeface from an array of {@link FontInfo}
     *
     * Results that are marked as not ready will be skipped.
     *
     * @param context A {@link Context} that will be used to fetch the font contents.
     * @param cancellationSignal A signal to cancel the operation in progress, or null if none. If
     *                           the operation is canceled, then {@link
     *                           android.os.OperationCanceledException} will be thrown.
     * @param fonts An array of {@link FontInfo} to be used to create a Typeface.
     * @return A Typeface object. Returns null if typeface creation fails.
     */
    public static Typeface buildTypeface(@NonNull Context context,
            @Nullable CancellationSignal cancellationSignal, @NonNull FontInfo[] fonts) {
        if (context.isRestricted()) {
            // TODO: Should we allow if the peer process is system or myself?
            return null;
        }
        final Map<Uri, ByteBuffer> uriBuffer =
                prepareFontData(context, fonts, cancellationSignal);
        if (uriBuffer.isEmpty()) {
            return null;
        }
        return new Typeface.Builder(fonts, uriBuffer).build();
    }

    
A helper function to create a mapping from Uri to ByteBuffer. Skip if the file contents is not ready to be read. 
Params:
context – A Context to be used for resolving content URI in FontInfo.
fonts – An array of FontInfo.
Returns:
A map from Uri to ByteBuffer./**
     * A helper function to create a mapping from {@link Uri} to {@link ByteBuffer}.
     *
     * Skip if the file contents is not ready to be read.
     *
     * @param context A {@link Context} to be used for resolving content URI in
     *                {@link FontInfo}.
     * @param fonts An array of {@link FontInfo}.
     * @return A map from {@link Uri} to {@link ByteBuffer}.
     */
    private static Map<Uri, ByteBuffer> prepareFontData(Context context, FontInfo[] fonts,
            CancellationSignal cancellationSignal) {
        final HashMap<Uri, ByteBuffer> out = new HashMap<>();
        final ContentResolver resolver = context.getContentResolver();

        for (FontInfo font : fonts) {
            if (font.getResultCode() != Columns.RESULT_CODE_OK) {
                continue;
            }

            final Uri uri = font.getUri();
            if (out.containsKey(uri)) {
                continue;
            }

            ByteBuffer buffer = null;
            try (final ParcelFileDescriptor pfd =
                    resolver.openFileDescriptor(uri, "r", cancellationSignal)) {
                if (pfd != null) {
                    try (final FileInputStream fis =
                            new FileInputStream(pfd.getFileDescriptor())) {
                        final FileChannel fileChannel = fis.getChannel();
                        final long size = fileChannel.size();
                        buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, size);
                    } catch (IOException e) {
                        // ignore
                    }
                }
            } catch (IOException e) {
                // ignore
            }

            // TODO: try other approach?, e.g. read all contents instead of mmap.

            out.put(uri, buffer);
        }
        return Collections.unmodifiableMap(out);
    }

    
@hide
/** @hide */
    @VisibleForTesting
    public static @Nullable ProviderInfo getProvider(
            PackageManager packageManager, FontRequest request) throws NameNotFoundException {
        String providerAuthority = request.getProviderAuthority();
        ProviderInfo info = packageManager.resolveContentProvider(providerAuthority, 0);
        if (info == null) {
            throw new NameNotFoundException("No package found for authority: " + providerAuthority);
        }

        if (!info.packageName.equals(request.getProviderPackage())) {
            throw new NameNotFoundException("Found content provider " + providerAuthority
                    + ", but package was not " + request.getProviderPackage());
        }
        // Trust system apps without signature checks
        if (info.applicationInfo.isSystemApp()) {
            return info;
        }

        List<byte[]> signatures;
        PackageInfo packageInfo = packageManager.getPackageInfo(info.packageName,
                PackageManager.GET_SIGNATURES);
        signatures = convertToByteArrayList(packageInfo.signatures);
        Collections.sort(signatures, sByteArrayComparator);

        List<List<byte[]>> requestCertificatesList = request.getCertificates();
        for (int i = 0; i < requestCertificatesList.size(); ++i) {
            // Make a copy so we can sort it without modifying the incoming data.
            List<byte[]> requestSignatures = new ArrayList<>(requestCertificatesList.get(i));
            Collections.sort(requestSignatures, sByteArrayComparator);
            if (equalsByteArrayList(signatures, requestSignatures)) {
                return info;
            }
        }
        return null;
    }

    private static final Comparator<byte[]> sByteArrayComparator = (l, r) -> {
        if (l.length != r.length) {
            return l.length - r.length;
        }
        for (int i = 0; i < l.length; ++i) {
            if (l[i] != r[i]) {
                return l[i] - r[i];
            }
        }
        return 0;
    };

    private static boolean equalsByteArrayList(
            List<byte[]> signatures, List<byte[]> requestSignatures) {
        if (signatures.size() != requestSignatures.size()) {
            return false;
        }
        for (int i = 0; i < signatures.size(); ++i) {
            if (!Arrays.equals(signatures.get(i), requestSignatures.get(i))) {
                return false;
            }
        }
        return true;
    }

    private static List<byte[]> convertToByteArrayList(Signature[] signatures) {
        List<byte[]> shas = new ArrayList<>();
        for (int i = 0; i < signatures.length; ++i) {
            shas.add(signatures[i].toByteArray());
        }
        return shas;
    }

    
@hide
/** @hide */
    @VisibleForTesting
    public static @NonNull FontInfo[] getFontFromProvider(
            Context context, FontRequest request, String authority,
            CancellationSignal cancellationSignal) {
        ArrayList<FontInfo> result = new ArrayList<>();
        final Uri uri = new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT)
                .authority(authority)
                .build();
        final Uri fileBaseUri = new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT)
                .authority(authority)
                .appendPath("file")
                .build();
        try (Cursor cursor = context.getContentResolver().query(uri, new String[] { Columns._ID,
                        Columns.FILE_ID, Columns.TTC_INDEX, Columns.VARIATION_SETTINGS,
                        Columns.WEIGHT, Columns.ITALIC, Columns.RESULT_CODE },
                "query = ?", new String[] { request.getQuery() }, null, cancellationSignal);) {
            // TODO: Should we restrict the amount of fonts that can be returned?
            // TODO: Write documentation explaining that all results should be from the same family.
            if (cursor != null && cursor.getCount() > 0) {
                final int resultCodeColumnIndex = cursor.getColumnIndex(Columns.RESULT_CODE);
                result = new ArrayList<>();
                final int idColumnIndex = cursor.getColumnIndexOrThrow(Columns._ID);
                final int fileIdColumnIndex = cursor.getColumnIndex(Columns.FILE_ID);
                final int ttcIndexColumnIndex = cursor.getColumnIndex(Columns.TTC_INDEX);
                final int vsColumnIndex = cursor.getColumnIndex(Columns.VARIATION_SETTINGS);
                final int weightColumnIndex = cursor.getColumnIndex(Columns.WEIGHT);
                final int italicColumnIndex = cursor.getColumnIndex(Columns.ITALIC);
                while (cursor.moveToNext()) {
                    int resultCode = resultCodeColumnIndex != -1
                            ? cursor.getInt(resultCodeColumnIndex) : Columns.RESULT_CODE_OK;
                    final int ttcIndex = ttcIndexColumnIndex != -1
                            ? cursor.getInt(ttcIndexColumnIndex) : 0;
                    final String variationSettings = vsColumnIndex != -1
                            ? cursor.getString(vsColumnIndex) : null;

                    Uri fileUri;
                    if (fileIdColumnIndex == -1) {
                        long id = cursor.getLong(idColumnIndex);
                        fileUri = ContentUris.withAppendedId(uri, id);
                    } else {
                        long id = cursor.getLong(fileIdColumnIndex);
                        fileUri = ContentUris.withAppendedId(fileBaseUri, id);
                    }
                    int weight;
                    boolean italic;
                    if (weightColumnIndex != -1 && italicColumnIndex != -1) {
                        weight = cursor.getInt(weightColumnIndex);
                        italic = cursor.getInt(italicColumnIndex) == 1;
                    } else {
                        weight = Typeface.Builder.NORMAL_WEIGHT;
                        italic = false;
                    }
                    FontVariationAxis[] axes =
                            FontVariationAxis.fromFontVariationSettings(variationSettings);
                    result.add(new FontInfo(fileUri, ttcIndex, axes, weight, italic, resultCode));
                }
            }
        }
        return result.toArray(new FontInfo[0]);
    }
}