/*
 * Copyright 2009-2010 by The Regents of the University of California
 * 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 from
 * 
 *     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 edu.uci.ics.hyracks.control.nc.io;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Executor;

import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.api.exceptions.HyracksException;
import edu.uci.ics.hyracks.api.io.FileHandle;
import edu.uci.ics.hyracks.api.io.FileReference;
import edu.uci.ics.hyracks.api.io.IIOFuture;
import edu.uci.ics.hyracks.api.io.IIOManager;
import edu.uci.ics.hyracks.api.io.IODeviceHandle;

public class IOManager implements IIOManager {
    private final List<IODeviceHandle> ioDevices;

    private final Executor executor;

    private final List<IODeviceHandle> workAreaIODevices;

    private int workAreaDeviceIndex;

    public IOManager(List<IODeviceHandle> devices, Executor executor) throws HyracksException {
        this.ioDevices = Collections.unmodifiableList(devices);
        this.executor = executor;
        workAreaIODevices = new ArrayList<IODeviceHandle>();
        for (IODeviceHandle d : ioDevices) {
            if (d.getWorkAreaPath() != null) {
                new File(d.getPath(), d.getWorkAreaPath()).mkdirs();
                workAreaIODevices.add(d);
            }
        }
        if (workAreaIODevices.isEmpty()) {
            throw new HyracksException("No devices with work areas found");
        }
        workAreaDeviceIndex = 0;
    }

    @Override
    public List<IODeviceHandle> getIODevices() {
        return ioDevices;
    }

    @Override
    public FileHandle open(FileReference fileRef, FileReadWriteMode rwMode, FileSyncMode syncMode)
            throws HyracksDataException {
        FileHandle fHandle = new FileHandle(fileRef);
        try {
            fHandle.open(rwMode, syncMode);
        } catch (IOException e) {
            throw new HyracksDataException(e);
        }
        return fHandle;
    }

    @Override
    public int syncWrite(FileHandle fHandle, long offset, ByteBuffer data) throws HyracksDataException {
        try {
            int n = 0;
            int remaining = data.remaining();
            while (remaining > 0) {
                int len = fHandle.getFileChannel().write(data, offset);
                if (len < 0) {
                    throw new HyracksDataException("Error writing to file: " + fHandle.getFileReference().toString());
                }
                remaining -= len;
                offset += len;
                n += len;
            }
            return n;
        } catch (HyracksDataException e) {
            throw e;
        } catch (IOException e) {
            throw new HyracksDataException(e);
        }
    }

    @Override
    public int syncRead(FileHandle fHandle, long offset, ByteBuffer data) throws HyracksDataException {
        try {
            int n = 0;
            int remaining = data.remaining();
            while (remaining > 0) {
                int len = fHandle.getFileChannel().read(data, offset);
                if (len < 0) {
                    return -1;
                }
                remaining -= len;
                offset += len;
                n += len;
            }
            return n;
        } catch (HyracksDataException e) {
            throw e;
        } catch (IOException e) {
            throw new HyracksDataException(e);
        }
    }

    @Override
    public IIOFuture asyncWrite(FileHandle fHandle, long offset, ByteBuffer data) {
        AsyncWriteRequest req = new AsyncWriteRequest(fHandle, offset, data);
        executor.execute(req);
        return req;
    }

    @Override
    public IIOFuture asyncRead(FileHandle fHandle, long offset, ByteBuffer data) {
        AsyncReadRequest req = new AsyncReadRequest(fHandle, offset, data);
        executor.execute(req);
        return req;
    }

    @Override
    public void close(FileHandle fHandle) throws HyracksDataException {
        try {
            fHandle.close();
        } catch (IOException e) {
            throw new HyracksDataException(e);
        }
    }

    public synchronized FileReference createWorkspaceFile(String prefix) throws HyracksDataException {
        IODeviceHandle dev = workAreaIODevices.get(workAreaDeviceIndex);
        workAreaDeviceIndex = (workAreaDeviceIndex + 1) % workAreaIODevices.size();
        String waPath = dev.getWorkAreaPath();
        File waf;
        try {
            waf = File.createTempFile(prefix, ".waf", new File(dev.getPath(), waPath));
        } catch (IOException e) {
            throw new HyracksDataException(e);
        }
        return dev.createFileReference(waPath + File.separator + waf.getName());
    }

    private abstract class AsyncRequest implements IIOFuture, Runnable {
        protected final FileHandle fHandle;
        protected final long offset;
        protected final ByteBuffer data;
        private boolean complete;
        private HyracksDataException exception;
        private int result;

        private AsyncRequest(FileHandle fHandle, long offset, ByteBuffer data) {
            this.fHandle = fHandle;
            this.offset = offset;
            this.data = data;
            complete = false;
            exception = null;
        }

        @Override
        public void run() {
            HyracksDataException hde = null;
            int res = -1;
            try {
                res = performOperation();
            } catch (HyracksDataException e) {
                hde = e;
            }
            synchronized (this) {
                exception = hde;
                result = res;
                complete = true;
                notifyAll();
            }
        }

        protected abstract int performOperation() throws HyracksDataException;

        @Override
        public synchronized int synchronize() throws HyracksDataException, InterruptedException {
            while (!complete) {
                wait();
            }
            if (exception != null) {
                throw exception;
            }
            return result;
        }

        @Override
        public synchronized boolean isComplete() {
            return complete;
        }
    }

    private class AsyncReadRequest extends AsyncRequest {
        private AsyncReadRequest(FileHandle fHandle, long offset, ByteBuffer data) {
            super(fHandle, offset, data);
        }

        @Override
        protected int performOperation() throws HyracksDataException {
            return syncRead(fHandle, offset, data);
        }
    }

    private class AsyncWriteRequest extends AsyncRequest {
        private AsyncWriteRequest(FileHandle fHandle, long offset, ByteBuffer data) {
            super(fHandle, offset, data);
        }

        @Override
        protected int performOperation() throws HyracksDataException {
            return syncWrite(fHandle, offset, data);
        }
    }
}