/*
 * Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * 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://aws.amazon.com/apache2.0
 *
 * This file 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.amazonaws.mobileconnectors.s3.transfermanager.internal;

import com.amazonaws.event.ProgressEvent;
import com.amazonaws.event.ProgressListenerChain;
import com.amazonaws.mobileconnectors.s3.transfermanager.Transfer;
import com.amazonaws.mobileconnectors.s3.transfermanager.TransferProgress;

import java.util.Collection;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Interface for multiple file transfers
 */
public abstract class MultipleFileTransfer<T extends Transfer> extends AbstractTransfer {

    protected final Collection<? extends T> subTransfers;

    /** Whether any of the sub-transfers has started. **/
    private AtomicBoolean subTransferStarted = new AtomicBoolean(false);

    MultipleFileTransfer(String description, TransferProgress transferProgress,
            ProgressListenerChain progressListenerChain, Collection<? extends T> subTransfers) {
        super(description, transferProgress, progressListenerChain);
        this.subTransfers = subTransfers;
    }

    /**
     * Set the state based on the states of all file downloads. Assumes all file
     * downloads are done.
     * <p>
     * A single failed sub-transfer makes the entire transfer failed. If there
     * are no failed sub-transfers, a single canceled sub-transfer makes the
     * entire transfer canceled. Otherwise, we consider ourselves Completed.
     */
    public void collateFinalState() {
        boolean seenCanceled = false;
        for (T download : subTransfers) {
            if (download.getState() == TransferState.Failed) {
                setState(TransferState.Failed);
                return;
            } else if (download.getState() == TransferState.Canceled) {
                seenCanceled = true;
            }
        }
        if (seenCanceled)
            setState(TransferState.Canceled);
        else
            setState(TransferState.Completed);
    }

    /**
     * Override this method so that TransferState updates are also sent out to
     * the progress listener chain in forms of ProgressEvent.
     */
    @Override
    public void setState(TransferState state) {
        super.setState(state);

        switch (state) {
            case Waiting:
                fireProgressEvent(ProgressEvent.PREPARING_EVENT_CODE);
                break;
            case InProgress:
                if (subTransferStarted.compareAndSet(false, true)) {
                    /* The first InProgress signal */
                    fireProgressEvent(ProgressEvent.STARTED_EVENT_CODE);
                }
                /*
                 * Don't need any event code update for subsequent InProgress
                 * signals
                 */
                break;
            case Completed:
                fireProgressEvent(ProgressEvent.COMPLETED_EVENT_CODE);
                break;
            case Canceled:
                fireProgressEvent(ProgressEvent.CANCELED_EVENT_CODE);
                break;
            case Failed:
                fireProgressEvent(ProgressEvent.FAILED_EVENT_CODE);
                break;
            default:
                break;
        }
    }
}