/*
 * Copyright (C) 2011 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.content.pm;

import android.os.Binder;
import android.os.IBinder;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.RemoteException;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;

Transfer a large list of Parcelable objects across an IPC.  Splits into
multiple transactions if needed.
Caveat: for efficiency and security, all elements must be the same concrete type.
In order to avoid writing the class name of each object, we must ensure that
each object is the same type, or else unparceling then reparceling the data may yield
a different result if the class name encoded in the Parcelable is a Base type.
See b/17671747.
@hide
/**
 * Transfer a large list of Parcelable objects across an IPC.  Splits into
 * multiple transactions if needed.
 *
 * Caveat: for efficiency and security, all elements must be the same concrete type.
 * In order to avoid writing the class name of each object, we must ensure that
 * each object is the same type, or else unparceling then reparceling the data may yield
 * a different result if the class name encoded in the Parcelable is a Base type.
 * See b/17671747.
 *
 * @hide
 */
abstract class BaseParceledListSlice<T> implements Parcelable {
    private static String TAG = "ParceledListSlice";
    private static boolean DEBUG = false;

    /*
     * TODO get this number from somewhere else. For now set it to a quarter of
     * the 1MB limit.
     */
    private static final int MAX_IPC_SIZE = IBinder.MAX_IPC_SIZE;

    private final List<T> mList;

    private int mInlineCountLimit = Integer.MAX_VALUE;

    public BaseParceledListSlice(List<T> list) {
        mList = list;
    }

    @SuppressWarnings("unchecked")
    BaseParceledListSlice(Parcel p, ClassLoader loader) {
        final int N = p.readInt();
        mList = new ArrayList<T>(N);
        if (DEBUG) Log.d(TAG, "Retrieving " + N + " items");
        if (N <= 0) {
            return;
        }

        Parcelable.Creator<?> creator = readParcelableCreator(p, loader);
        Class<?> listElementClass = null;

        int i = 0;
        while (i < N) {
            if (p.readInt() == 0) {
                break;
            }

            final T parcelable = readCreator(creator, p, loader);
            if (listElementClass == null) {
                listElementClass = parcelable.getClass();
            } else {
                verifySameType(listElementClass, parcelable.getClass());
            }

            mList.add(parcelable);

            if (DEBUG) Log.d(TAG, "Read inline #" + i + ": " + mList.get(mList.size()-1));
            i++;
        }
        if (i >= N) {
            return;
        }
        final IBinder retriever = p.readStrongBinder();
        while (i < N) {
            if (DEBUG) Log.d(TAG, "Reading more @" + i + " of " + N + ": retriever=" + retriever);
            Parcel data = Parcel.obtain();
            Parcel reply = Parcel.obtain();
            data.writeInt(i);
            try {
                retriever.transact(IBinder.FIRST_CALL_TRANSACTION, data, reply, 0);
            } catch (RemoteException e) {
                Log.w(TAG, "Failure retrieving array; only received " + i + " of " + N, e);
                return;
            }
            while (i < N && reply.readInt() != 0) {
                final T parcelable = readCreator(creator, reply, loader);
                verifySameType(listElementClass, parcelable.getClass());

                mList.add(parcelable);

                if (DEBUG) Log.d(TAG, "Read extra #" + i + ": " + mList.get(mList.size()-1));
                i++;
            }
            reply.recycle();
            data.recycle();
        }
    }

    private T readCreator(Parcelable.Creator<?> creator, Parcel p, ClassLoader loader) {
        if (creator instanceof Parcelable.ClassLoaderCreator<?>) {
            Parcelable.ClassLoaderCreator<?> classLoaderCreator =
                    (Parcelable.ClassLoaderCreator<?>) creator;
            return (T) classLoaderCreator.createFromParcel(p, loader);
        }
        return (T) creator.createFromParcel(p);
    }

    private static void verifySameType(final Class<?> expected, final Class<?> actual) {
        if (!actual.equals(expected)) {
            throw new IllegalArgumentException("Can't unparcel type "
                    + actual.getName() + " in list of type "
                    + expected.getName());
        }
    }

    public List<T> getList() {
        return mList;
    }

    
Set a limit on the maximum number of entries in the array that will be included
inline in the initial parcelling of this object.
/**
     * Set a limit on the maximum number of entries in the array that will be included
     * inline in the initial parcelling of this object.
     */
    public void setInlineCountLimit(int maxCount) {
        mInlineCountLimit = maxCount;
    }

    
Write this to another Parcel. Note that this discards the internal Parcel
and should not be used anymore. This is so we can pass this to a Binder
where we won't have a chance to call recycle on this.
/**
     * Write this to another Parcel. Note that this discards the internal Parcel
     * and should not be used anymore. This is so we can pass this to a Binder
     * where we won't have a chance to call recycle on this.
     */
    @Override
    public void writeToParcel(Parcel dest, int flags) {
        final int N = mList.size();
        final int callFlags = flags;
        dest.writeInt(N);
        if (DEBUG) Log.d(TAG, "Writing " + N + " items");
        if (N > 0) {
            final Class<?> listElementClass = mList.get(0).getClass();
            writeParcelableCreator(mList.get(0), dest);
            int i = 0;
            while (i < N && i < mInlineCountLimit && dest.dataSize() < MAX_IPC_SIZE) {
                dest.writeInt(1);

                final T parcelable = mList.get(i);
                verifySameType(listElementClass, parcelable.getClass());
                writeElement(parcelable, dest, callFlags);

                if (DEBUG) Log.d(TAG, "Wrote inline #" + i + ": " + mList.get(i));
                i++;
            }
            if (i < N) {
                dest.writeInt(0);
                Binder retriever = new Binder() {
                    @Override
                    protected boolean onTransact(int code, Parcel data, Parcel reply, int flags)
                            throws RemoteException {
                        if (code != FIRST_CALL_TRANSACTION) {
                            return super.onTransact(code, data, reply, flags);
                        }
                        int i = data.readInt();
                        if (DEBUG) Log.d(TAG, "Writing more @" + i + " of " + N);
                        while (i < N && reply.dataSize() < MAX_IPC_SIZE) {
                            reply.writeInt(1);

                            final T parcelable = mList.get(i);
                            verifySameType(listElementClass, parcelable.getClass());
                            writeElement(parcelable, reply, callFlags);

                            if (DEBUG) Log.d(TAG, "Wrote extra #" + i + ": " + mList.get(i));
                            i++;
                        }
                        if (i < N) {
                            if (DEBUG) Log.d(TAG, "Breaking @" + i + " of " + N);
                            reply.writeInt(0);
                        }
                        return true;
                    }
                };
                if (DEBUG) Log.d(TAG, "Breaking @" + i + " of " + N + ": retriever=" + retriever);
                dest.writeStrongBinder(retriever);
            }
        }
    }

    protected abstract void writeElement(T parcelable, Parcel reply, int callFlags);

    protected abstract void writeParcelableCreator(T parcelable, Parcel dest);

    protected abstract Parcelable.Creator<?> readParcelableCreator(Parcel from, ClassLoader loader);
}