/*
    * Copyright 2013 The Netty Project
    *
    * The Netty Project licenses this file to you 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 io.netty.channel.oio;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.Channel;
  import io.netty.channel.FileRegion;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.channels.Channels;
  import java.nio.channels.ClosedChannelException;
  import java.nio.channels.NotYetConnectedException;
  import java.nio.channels.WritableByteChannel;
  
  /**
   * Abstract base class for OIO Channels that are based on streams.
   */
  public abstract class OioByteStreamChannel extends AbstractOioByteChannel {
  
      private static final InputStream CLOSED_IN = new InputStream() {
          @Override
          public int read() {
              return -1;
          }
      };
  
      private static final OutputStream CLOSED_OUT = new OutputStream() {
          @Override
          public void write(int b) throws IOException {
              throw new ClosedChannelException();
          }
      };
  
      private InputStream is;
      private OutputStream os;
      private WritableByteChannel outChannel;
  
      /**
       * Create a new instance
       *
       * @param parent    the parent {@link Channel} which was used to create this instance. This can be null if the
       *                  {@link} has no parent as it was created by your self.
       */
      protected OioByteStreamChannel(Channel parent) {
          super(parent);
      }
  
      /**
       * Activate this instance. After this call {@link #isActive()} will return {@code true}.
       */
      protected final void activate(InputStream is, OutputStream os) {
          if (this.is != null) {
              throw new IllegalStateException("input was set already");
          }
          if (this.os != null) {
              throw new IllegalStateException("output was set already");
          }
          if (is == null) {
              throw new NullPointerException("is");
          }
          if (os == null) {
              throw new NullPointerException("os");
          }
          this.is = is;
          this.os = os;
      }
  
      @Override
      public boolean isActive() {
          InputStream is = this.is;
          if (is == null || is == CLOSED_IN) {
              return false;
          }
  
          OutputStream os = this.os;
          return !(os == null || os == CLOSED_OUT);
      }
  
      @Override
      protected int available() {
          try {
              return is.available();
          } catch (IOException ignored) {
             return 0;
         }
     }
 
     @Override
     protected int doReadBytes(ByteBuf buf) throws Exception {
         int length = Math.max(1, Math.min(available(), buf.maxWritableBytes()));
         return buf.writeBytes(is, length);
     }
 
     @Override
     protected void doWriteBytes(ByteBuf buf) throws Exception {
         OutputStream os = this.os;
         if (os == null) {
             throw new NotYetConnectedException();
         }
         buf.readBytes(os, buf.readableBytes());
     }
 
     @Override
     protected void doWriteFileRegion(FileRegion region) throws Exception {
         OutputStream os = this.os;
         if (os == null) {
             throw new NotYetConnectedException();
         }
         if (outChannel == null) {
             outChannel = Channels.newChannel(os);
         }
 
         long written = 0;
         for (;;) {
             long localWritten = region.transferTo(outChannel, written);
             if (localWritten == -1) {
                 checkEOF(region);
                 return;
             }
             written += localWritten;
 
             if (written >= region.count()) {
                 return;
             }
         }
     }
 
     private static void checkEOF(FileRegion region) throws IOException {
         if (region.transfered() < region.count()) {
             throw new EOFException("Expected to be able to write " + region.count() + " bytes, " +
                                    "but only wrote " + region.transfered());
         }
     }
 
     @Override
     protected void doClose() throws Exception {
         InputStream is = this.is;
         OutputStream os = this.os;
         this.is = CLOSED_IN;
         this.os = CLOSED_OUT;
 
         try {
             if (is != null) {
                 is.close();
             }
         } finally {
             if (os != null) {
                 os.close();
             }
         }
     }
 }