/*
 * Copyright (C) 2024 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.os.flagging;

import static android.aconfig.storage.TableUtils.StorageFilesBundle;

import android.aconfig.storage.AconfigStorageException;
import android.aconfig.storage.FlagValueList;
import android.aconfig.storage.PackageTable;
import android.annotation.NonNull;
import android.compat.annotation.UnsupportedAppUsage;

/**
 * An {@code aconfig} package containing the enabled state of its flags.
 *
 * <p><strong>Note: this is intended only to be used by generated code. To determine if a given flag
 * is enabled in app code, the generated android flags should be used.</strong>
 *
 * <p>This class is not part of the public API and should be used by Acnofig Flag internally </b> It
 * is intended for internal use only and will be changed or removed without notice.
 *
 * <p>This class is used to read the flag from Aconfig Package.Each instance of this class will
 * cache information related to one package. To read flags from a different package, a new instance
 * of this class should be {@link #load loaded}.
 *
 * @hide
 */
public class AconfigPackageInternal {

    private final FlagValueList mFlagValueList;
    private final int mPackageBooleanStartOffset;

    private AconfigPackageInternal(
            @NonNull FlagValueList flagValueList, int packageBooleanStartOffset) {
        this.mFlagValueList = flagValueList;
        this.mPackageBooleanStartOffset = packageBooleanStartOffset;
    }

    /**
     * Loads an Aconfig package from the specified container and verifies its fingerprint.
     *
     * <p>This method is intended for internal use only and may be changed or removed without
     * notice.
     *
     * @param packageName The name of the Aconfig package.
     * @param packageFingerprint The expected fingerprint of the package.
     * @return An instance of {@link AconfigPackageInternal} representing the loaded package.
     * @hide
     */
    @UnsupportedAppUsage
    public static @NonNull AconfigPackageInternal load(
            @NonNull String packageName, long packageFingerprint) {
        StorageFilesBundle files = AconfigPackage.sStorageFilesCache.get(packageName);
        if (files == null) {
            throw new AconfigStorageException(
                    AconfigStorageException.ERROR_PACKAGE_NOT_FOUND,
                    "package " + packageName + " cannot be found on the device");
        }
        PackageTable.Node pNode = files.packageTable.get(packageName);
        FlagValueList vList = files.flagValueList;

        if (pNode.hasPackageFingerprint() && packageFingerprint != pNode.getPackageFingerprint()) {
            throw new AconfigStorageException(
                    AconfigStorageException.ERROR_FILE_FINGERPRINT_MISMATCH,
                    "package " + packageName + "fingerprint doesn't match the one on device");
        }

        return new AconfigPackageInternal(vList, pNode.getBooleanStartIndex());
    }

    /**
     * Retrieves the value of a boolean flag using its index.
     *
     * <p>This method is intended for internal use only and may be changed or removed without
     * notice.
     *
     * <p>This method retrieves the value of a flag within the loaded Aconfig package using its
     * index. The index is generated at build time and may vary between builds.
     *
     * @param index The index of the flag within the package.
     * @return The boolean value of the flag.
     * @hide
     */
    @UnsupportedAppUsage
    public boolean getBooleanFlagValue(int index) {
        return mFlagValueList.getBoolean(index + mPackageBooleanStartOffset);
    }
}