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/**
 * 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 com.gh.bmd.jrt.android.v4.routine;

import android.content.Context;
import android.support.v4.content.AsyncTaskLoader;

import com.gh.bmd.jrt.android.invocation.AndroidInvocation;
import com.gh.bmd.jrt.builder.RoutineConfiguration;
import com.gh.bmd.jrt.builder.RoutineConfiguration.OrderType;
import com.gh.bmd.jrt.channel.OutputChannel;
import com.gh.bmd.jrt.channel.ResultChannel;
import com.gh.bmd.jrt.channel.StandaloneChannel;
import com.gh.bmd.jrt.channel.StandaloneChannel.StandaloneInput;
import com.gh.bmd.jrt.common.InvocationException;
import com.gh.bmd.jrt.common.InvocationInterruptedException;
import com.gh.bmd.jrt.log.Logger;
import com.gh.bmd.jrt.time.TimeDuration;

import java.util.List;
import java.util.concurrent.TimeUnit;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import static com.gh.bmd.jrt.builder.RoutineConfiguration.builder;

/**
 * Loader implementation performing the routine invocation.
 * 
 * Created by davide on 12/8/14.
 *
 * @param   the input data type.
 * @param  the output data type.
 */
class RoutineLoader extends AsyncTaskLoader> {

    private final List mInputs;

    private final AndroidInvocation mInvocation;

    private final Logger mLogger;

    private final OrderType mOrderType;

    private int mInvocationCount;

    private InvocationResult mResult;

    /**
     * Stores away the application context associated with context.
     * Since Loaders can be used across multiple activities it's dangerous to
     * store the context directly; always use {@link #getContext()} to retrieve
     * the Loader's Context, don't use the constructor argument directly.
     * The Context returned by {@link #getContext} is safe to use across
     * Activity instances.
     *
     * @param context    used to retrieve the application context.
     * @param invocation the invocation instance.
     * @param inputs     the input data.
     * @param order      the data order.
     * @param logger     the logger instance.
     * @throws java.lang.NullPointerException if any of the specified non-null parameters is null.
     */
    @SuppressWarnings("ConstantConditions")
    RoutineLoader(@Nonnull final Context context,
            @Nonnull final AndroidInvocation invocation,
            @Nonnull final List inputs, @Nullable final OrderType order,
            @Nonnull final Logger logger) {

        super(context);

        if (invocation == null) {

            throw new NullPointerException("the invocation instance must not be null");
        }

        if (inputs == null) {

            throw new NullPointerException("the list of input data must not be null");
        }

        mInvocation = invocation;
        mInputs = inputs;
        mOrderType = order;
        mLogger = logger.subContextLogger(this);
    }

    /**
     * Checks if the loader inputs are equal to the specified ones.
     *
     * @param inputs the input data.
     * @return whether the inputs are equal.
     */
    public boolean areSameInputs(@Nullable final List inputs) {

        return mInputs.equals(inputs);
    }

    @Override
    public void deliverResult(final InvocationResult data) {

        mLogger.dbg("delivering result: %s", data);
        mResult = data;
        super.deliverResult(data);
    }

    @Override
    protected void onStartLoading() {

        super.onStartLoading();

        mLogger.dbg("start background invocation");

        if (mResult != null) {

            deliverResult(mResult);
        }

        if (takeContentChanged() || (mResult == null)) {

            forceLoad();
        }
    }

    @Override
    protected void onReset() {

        try {

            mInvocation.onDestroy();

        } catch (final InvocationInterruptedException e) {

            throw e.interrupt();

        } catch (final Throwable t) {

            mLogger.wrn(t, "ignoring exception while destroying invocation instance");
        }

        mLogger.dbg("resetting result");
        mResult = null;
        super.onReset();
    }

    /**
     * Returns the type of the loader invocation.
     *
     * @return the invocation class.
     */
    @Nonnull
    public Class getInvocationType() {

        return mInvocation.getClass();
    }

    @Override
    public InvocationResult loadInBackground() {

        final Logger logger = mLogger;
        final AndroidInvocation invocation = mInvocation;
        final LoaderResultChannel channel =
                new LoaderResultChannel(mOrderType, logger);
        final InvocationOutputConsumer consumer =
                new InvocationOutputConsumer(this, logger);
        channel.output().bind(consumer);

        Throwable abortException = null;
        logger.dbg("running invocation");

        try {

            invocation.onInit();

            for (final INPUT input : mInputs) {

                invocation.onInput(input, channel);
            }

            invocation.onResult(channel);
            invocation.onReturn();

        } catch (final InvocationException e) {

            abortException = e.getCause();

        } catch (final Throwable t) {

            abortException = t;
        }

        if (abortException != null) {

            logger.dbg(abortException, "aborting invocation");

            try {

                invocation.onAbort(abortException);

            } catch (final InvocationException e) {

                abortException = e.getCause();

            } catch (final Throwable t) {

                abortException = t;
            }

            logger.dbg(abortException, "aborted invocation");
            channel.abort(abortException);
            return consumer.createResult();
        }

        logger.dbg("reading invocation results");
        channel.close();
        return consumer.createResult();
    }

    /**
     * Gets this loader invocation count.
     *
     * @return the invocation count.
     */
    int getInvocationCount() {

        return mInvocationCount;
    }

    /**
     * Sets the invocation count.
     *
     * @param count the invocation count.
     */
    void setInvocationCount(final int count) {

        mInvocationCount = count;
    }

    /**
     * Loader result channel.
     *
     * @param  the output data type.
     */
    private static class LoaderResultChannel implements ResultChannel {

        private final StandaloneChannel mStandaloneChannel;

        private final StandaloneInput mStandaloneInput;

        /**
         * Constructor.
         *
         * @param order  the data order.
         * @param logger the logger instance.
         */
        private LoaderResultChannel(@Nullable final OrderType order, @Nonnull final Logger logger) {

            final RoutineConfiguration configuration = builder().withOutputOrder(order)
                                                                .withOutputSize(Integer.MAX_VALUE)
                                                                .withOutputTimeout(
                                                                        TimeDuration.ZERO)
                                                                .withLog(logger.getLog())
                                                                .withLogLevel(logger.getLogLevel())
                                                                .buildConfiguration();
            mStandaloneChannel =
                    JRoutine.standalone().withConfiguration(configuration).buildChannel();
            mStandaloneInput = mStandaloneChannel.input();
        }

        @Override
        public boolean abort() {

            return mStandaloneInput.abort();
        }

        @Override
        public boolean abort(@Nullable final Throwable reason) {

            return mStandaloneInput.abort(reason);
        }

        @Override
        public boolean isOpen() {

            return mStandaloneInput.isOpen();
        }

        @Nonnull
        @Override
        public ResultChannel after(@Nonnull final TimeDuration delay) {

            mStandaloneInput.after(delay);
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel after(final long delay, @Nonnull final TimeUnit timeUnit) {

            mStandaloneInput.after(delay, timeUnit);
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel now() {

            mStandaloneInput.now();
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel pass(@Nullable final OutputChannel channel) {

            mStandaloneInput.pass(channel);
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel pass(@Nullable final Iterable outputs) {

            mStandaloneInput.pass(outputs);
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel pass(@Nullable final OUTPUT output) {

            mStandaloneInput.pass(output);
            return this;
        }

        @Nonnull
        @Override
        public ResultChannel pass(@Nullable final OUTPUT... outputs) {

            mStandaloneInput.pass(outputs);
            return this;
        }

        private void close() {

            mStandaloneInput.close();
        }

        @Nonnull
        private OutputChannel output() {

            return mStandaloneChannel.output();
        }
    }
}