/*
 * Copyright (C) 2012 The Guava Authors
 *
 * 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.google.common.io;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Closeable;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.logging.Level;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

A Closeable that collects Closeable resources and closes them all when it is closed. This is intended to approximately emulate the behavior of Java 7's try-with-resources statement in JDK6-compatible code. Running on Java 7, code using this
should be approximately equivalent in behavior to the same code written with try-with-resources.
Running on Java 6, exceptions that cannot be thrown must be logged rather than being added to the
thrown exception as a suppressed exception.
This class is intended to be used in the following pattern:

Closer closer = Closer.create();
try {
  InputStream in = closer.register(openInputStream());
  OutputStream out = closer.register(openOutputStream());
  // do stuff
 } catch (Throwable e) {
  // ensure that any checked exception types other than IOException that could be thrown are
  // provided here, e.g. throw closer.rethrow(e, CheckedException.class);
  throw closer.rethrow(e);
 } finally {
  closer.close();
 }

Note that this try-catch-finally block is not equivalent to a try-catch-finally block using
try-with-resources. To get the equivalent of that, you must wrap the above code in another try block in order to catch any exception that may be thrown (including from the call to 
close()). 
This pattern ensures the following:

  
Each Closeable resource that is successfully registered will be closed later. 
If a Throwable is thrown in the try block, no exceptions that occur when attempting to close resources will be thrown from the finally block. The throwable from the try block will be thrown. 
If no exceptions or errors were thrown in the try block, the first exception thrown
      by an attempt to close a resource will be thrown.
  
Any exception caught when attempting to close a resource that is not thrown (because
      another exception is already being thrown) is suppressed.

An exception that is suppressed is not thrown. The method of suppression used depends on the
version of Java the code is running on:

  
Java 7+: Exceptions are suppressed by adding them to the exception that will be thrown using Throwable.addSuppressed(Throwable). 
Java 6: Exceptions are suppressed by logging them instead.

Author:
Colin Decker
Since:
14.0/**
 * A {@link Closeable} that collects {@code Closeable} resources and closes them all when it is
 * {@linkplain #close closed}. This is intended to approximately emulate the behavior of Java 7's <a
 * href="http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html"
 * >try-with-resources</a> statement in JDK6-compatible code. Running on Java 7, code using this
 * should be approximately equivalent in behavior to the same code written with try-with-resources.
 * Running on Java 6, exceptions that cannot be thrown must be logged rather than being added to the
 * thrown exception as a suppressed exception.
 *
 * <p>This class is intended to be used in the following pattern:
 *
 * <pre>{@code
 * Closer closer = Closer.create();
 * try {
 *   InputStream in = closer.register(openInputStream());
 *   OutputStream out = closer.register(openOutputStream());
 *   // do stuff
 * } catch (Throwable e) {
 *   // ensure that any checked exception types other than IOException that could be thrown are
 *   // provided here, e.g. throw closer.rethrow(e, CheckedException.class);
 *   throw closer.rethrow(e);
 * } finally {
 *   closer.close();
 * }
 * }</pre>
 *
 * <p>Note that this try-catch-finally block is not equivalent to a try-catch-finally block using
 * try-with-resources. To get the equivalent of that, you must wrap the above code in <i>another</i>
 * try block in order to catch any exception that may be thrown (including from the call to {@code
 * close()}).
 *
 * <p>This pattern ensures the following:
 *
 * <ul>
 *   <li>Each {@code Closeable} resource that is successfully registered will be closed later.
 *   <li>If a {@code Throwable} is thrown in the try block, no exceptions that occur when attempting
 *       to close resources will be thrown from the finally block. The throwable from the try block
 *       will be thrown.
 *   <li>If no exceptions or errors were thrown in the try block, the <i>first</i> exception thrown
 *       by an attempt to close a resource will be thrown.
 *   <li>Any exception caught when attempting to close a resource that is <i>not</i> thrown (because
 *       another exception is already being thrown) is <i>suppressed</i>.
 * </ul>
 *
 * <p>An exception that is suppressed is not thrown. The method of suppression used depends on the
 * version of Java the code is running on:
 *
 * <ul>
 *   <li><b>Java 7+:</b> Exceptions are suppressed by adding them to the exception that <i>will</i>
 *       be thrown using {@code Throwable.addSuppressed(Throwable)}.
 *   <li><b>Java 6:</b> Exceptions are suppressed by logging them instead.
 * </ul>
 *
 * @author Colin Decker
 * @since 14.0
 */
// Coffee's for {@link Closer closers} only.
@Beta
@GwtIncompatible
public final class Closer implements Closeable {

  
The suppressor implementation to use for the current Java version. /** The suppressor implementation to use for the current Java version. */
  private static final Suppressor SUPPRESSOR =
      SuppressingSuppressor.isAvailable()
          ? SuppressingSuppressor.INSTANCE
          : LoggingSuppressor.INSTANCE;

  
Creates a new Closer. /** Creates a new {@link Closer}. */
  public static Closer create() {
    return new Closer(SUPPRESSOR);
  }

  @VisibleForTesting final Suppressor suppressor;

  // only need space for 2 elements in most cases, so try to use the smallest array possible
  private final Deque<Closeable> stack = new ArrayDeque<>(4);
  @MonotonicNonNull private Throwable thrown;

  @VisibleForTesting
  Closer(Suppressor suppressor) {
    this.suppressor = checkNotNull(suppressor); // checkNotNull to satisfy null tests
  }

  
Registers the given closeable to be closed when this Closer is closed. 
Returns:
the given closeable/**
   * Registers the given {@code closeable} to be closed when this {@code Closer} is {@linkplain
   * #close closed}.
   *
   * @return the given {@code closeable}
   */
  // close. this word no longer has any meaning to me.
  @CanIgnoreReturnValue
  public <C extends Closeable> C register(@Nullable C closeable) {
    if (closeable != null) {
      stack.addFirst(closeable);
    }

    return closeable;
  }

  
Stores the given throwable and rethrows it. It will be rethrown as is if it is an 
IOException, RuntimeException or Error. Otherwise, it will be rethrown wrapped in a RuntimeException. Note: Be sure to declare all of the checked exception
types your try block can throw when calling an overload of this method so as to avoid losing
the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e); to ensure the compiler knows that it will throw. 
Throws:
IOException – when the given throwable is an IOException
Returns:
this method does not return; it always throws/**
   * Stores the given throwable and rethrows it. It will be rethrown as is if it is an {@code
   * IOException}, {@code RuntimeException} or {@code Error}. Otherwise, it will be rethrown wrapped
   * in a {@code RuntimeException}. <b>Note:</b> Be sure to declare all of the checked exception
   * types your try block can throw when calling an overload of this method so as to avoid losing
   * the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e);}
   * to ensure the compiler knows that it will throw.
   *
   * @return this method does not return; it always throws
   * @throws IOException when the given throwable is an IOException
   */
  public RuntimeException rethrow(Throwable e) throws IOException {
    checkNotNull(e);
    thrown = e;
    Throwables.propagateIfPossible(e, IOException.class);
    throw new RuntimeException(e);
  }

  
Stores the given throwable and rethrows it. It will be rethrown as is if it is an 
IOException, RuntimeException, Error or a checked exception of the given type. Otherwise, it will be rethrown wrapped in a RuntimeException. Note: Be sure to
declare all of the checked exception types your try block can throw when calling an overload of
this method so as to avoid losing the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e,
...); to ensure the compiler knows that it will throw. 
Throws:
IOException – when the given throwable is an IOException
X – when the given throwable is of the declared type X
Returns:
this method does not return; it always throws/**
   * Stores the given throwable and rethrows it. It will be rethrown as is if it is an {@code
   * IOException}, {@code RuntimeException}, {@code Error} or a checked exception of the given type.
   * Otherwise, it will be rethrown wrapped in a {@code RuntimeException}. <b>Note:</b> Be sure to
   * declare all of the checked exception types your try block can throw when calling an overload of
   * this method so as to avoid losing the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e,
   * ...);} to ensure the compiler knows that it will throw.
   *
   * @return this method does not return; it always throws
   * @throws IOException when the given throwable is an IOException
   * @throws X when the given throwable is of the declared type X
   */
  public <X extends Exception> RuntimeException rethrow(Throwable e, Class<X> declaredType)
      throws IOException, X {
    checkNotNull(e);
    thrown = e;
    Throwables.propagateIfPossible(e, IOException.class);
    Throwables.propagateIfPossible(e, declaredType);
    throw new RuntimeException(e);
  }

  
Stores the given throwable and rethrows it. It will be rethrown as is if it is an 
IOException, RuntimeException, Error or a checked exception of either of the given types. Otherwise, it will be rethrown wrapped in a RuntimeException. Note:
Be sure to declare all of the checked exception types your try block can throw when calling an
overload of this method so as to avoid losing the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e,
...); to ensure the compiler knows that it will throw. 
Throws:
IOException – when the given throwable is an IOException
X1 – when the given throwable is of the declared type X1
X2 – when the given throwable is of the declared type X2
Returns:
this method does not return; it always throws/**
   * Stores the given throwable and rethrows it. It will be rethrown as is if it is an {@code
   * IOException}, {@code RuntimeException}, {@code Error} or a checked exception of either of the
   * given types. Otherwise, it will be rethrown wrapped in a {@code RuntimeException}. <b>Note:</b>
   * Be sure to declare all of the checked exception types your try block can throw when calling an
   * overload of this method so as to avoid losing the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e,
   * ...);} to ensure the compiler knows that it will throw.
   *
   * @return this method does not return; it always throws
   * @throws IOException when the given throwable is an IOException
   * @throws X1 when the given throwable is of the declared type X1
   * @throws X2 when the given throwable is of the declared type X2
   */
  public <X1 extends Exception, X2 extends Exception> RuntimeException rethrow(
      Throwable e, Class<X1> declaredType1, Class<X2> declaredType2) throws IOException, X1, X2 {
    checkNotNull(e);
    thrown = e;
    Throwables.propagateIfPossible(e, IOException.class);
    Throwables.propagateIfPossible(e, declaredType1, declaredType2);
    throw new RuntimeException(e);
  }

  
Closes all Closeable instances that have been added to this Closer. If an exception was thrown in the try block and passed to one of the exceptionThrown methods, any exceptions thrown when attempting to close a closeable will be suppressed. Otherwise, the first exception to be thrown from an attempt to close a closeable will be thrown and any
additional exceptions that are thrown after that will be suppressed.
/**
   * Closes all {@code Closeable} instances that have been added to this {@code Closer}. If an
   * exception was thrown in the try block and passed to one of the {@code exceptionThrown} methods,
   * any exceptions thrown when attempting to close a closeable will be suppressed. Otherwise, the
   * <i>first</i> exception to be thrown from an attempt to close a closeable will be thrown and any
   * additional exceptions that are thrown after that will be suppressed.
   */
  @Override
  public void close() throws IOException {
    Throwable throwable = thrown;

    // close closeables in LIFO order
    while (!stack.isEmpty()) {
      Closeable closeable = stack.removeFirst();
      try {
        closeable.close();
      } catch (Throwable e) {
        if (throwable == null) {
          throwable = e;
        } else {
          suppressor.suppress(closeable, throwable, e);
        }
      }
    }

    if (thrown == null && throwable != null) {
      Throwables.propagateIfPossible(throwable, IOException.class);
      throw new AssertionError(throwable); // not possible
    }
  }

  
Suppression strategy interface. /** Suppression strategy interface. */
  @VisibleForTesting
  interface Suppressor {
    
Suppresses the given exception (suppressed) which was thrown when attempting to close the given closeable. thrown is the exception that is actually being thrown from the method. Implementations of this method should not throw under any circumstances. /**
     * Suppresses the given exception ({@code suppressed}) which was thrown when attempting to close
     * the given closeable. {@code thrown} is the exception that is actually being thrown from the
     * method. Implementations of this method should not throw under any circumstances.
     */
    void suppress(Closeable closeable, Throwable thrown, Throwable suppressed);
  }

  
Suppresses exceptions by logging them. /** Suppresses exceptions by logging them. */
  @VisibleForTesting
  static final class LoggingSuppressor implements Suppressor {

    static final LoggingSuppressor INSTANCE = new LoggingSuppressor();

    @Override
    public void suppress(Closeable closeable, Throwable thrown, Throwable suppressed) {
      // log to the same place as Closeables
      Closeables.logger.log(
          Level.WARNING, "Suppressing exception thrown when closing " + closeable, suppressed);
    }
  }

  
Suppresses exceptions by adding them to the exception that will be thrown using JDK7's
addSuppressed(Throwable) mechanism.
/**
   * Suppresses exceptions by adding them to the exception that will be thrown using JDK7's
   * addSuppressed(Throwable) mechanism.
   */
  @VisibleForTesting
  static final class SuppressingSuppressor implements Suppressor {

    static final SuppressingSuppressor INSTANCE = new SuppressingSuppressor();

    static boolean isAvailable() {
      return addSuppressed != null;
    }

    static final Method addSuppressed = getAddSuppressed();

    private static Method getAddSuppressed() {
      try {
        return Throwable.class.getMethod("addSuppressed", Throwable.class);
      } catch (Throwable e) {
        return null;
      }
    }

    @Override
    public void suppress(Closeable closeable, Throwable thrown, Throwable suppressed) {
      // ensure no exceptions from addSuppressed
      if (thrown == suppressed) {
        return;
      }
      try {
        addSuppressed.invoke(thrown, suppressed);
      } catch (Throwable e) {
        // if, somehow, IllegalAccessException or another exception is thrown, fall back to logging
        LoggingSuppressor.INSTANCE.suppress(closeable, thrown, suppressed);
      }
    }
  }
}