/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF 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 org.apache.logging.log4j.io;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.io.Reader;
  import java.io.UnsupportedEncodingException;
  import java.io.Writer;
  import java.nio.charset.Charset;
  
  import org.apache.logging.log4j.Level;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.LoggingException;
  import org.apache.logging.log4j.Marker;
  import org.apache.logging.log4j.spi.ExtendedLogger;
  import org.apache.logging.log4j.util.ReflectionUtil;
  
  /**
   * Builder class to wrap {@link Logger Loggers} into Java IO compatible classes.
   *
   * <p>Both the {@link InputStream}/{@link OutputStream} and {@link Reader}/{@link Writer} family of classes are
   * supported. {@link OutputStream} and {@link Writer} instances can be wrapped by a filtered version of their
   * corresponding classes ({@link java.io.FilterOutputStream} and {@link java.io.FilterWriter}) in order to log all
   * lines written to these instances. {@link InputStream} and {@link Reader} instances can be wrapped by a sort of
   * wiretapped version of their respective classes; all lines read from these instances will be logged.</p>
   *
   * <p>The main feature, however, is the ability to create a {@link PrintWriter}, {@link PrintStream}, {@link Writer},
   * {@link java.io.BufferedWriter}, {@link OutputStream}, or {@link java.io.BufferedOutputStream} that is backed by a
   * {@link Logger}. The main inspiration for this feature is the JDBC API which uses a PrintWriter to perform debug
   * logging. In order to properly integrate APIs like JDBC into Log4j, create a PrintWriter using this class.</p>
   *
   * <p>The IoBuilder support configuration of the logging {@link Level} it should use (defaults to the level of
   * the underlying Logger), and an optional {@link Marker}. The other configurable objects are explained in more
   * detail below.</p>
   *
   * @since 2.1
   */
  public class IoBuilder {
      private final ExtendedLogger logger;
      private Level level;
      private Marker marker;
      private String fqcn;
      private boolean autoFlush;
      private boolean buffered;
      private int bufferSize;
      private Charset charset;
      private Reader reader;
      private Writer writer;
      private InputStream inputStream;
      private OutputStream outputStream;
  
      /**
       * Creates a new builder for a given {@link Logger}. The Logger instance must implement {@link ExtendedLogger} or
       * an exception will be thrown.
       *
       * @param logger the Logger to wrap into a LoggerStream
       * @return a new IoBuilder
       * @throws UnsupportedOperationException if {@code logger} does not implement {@link ExtendedLogger} or if
       *                                       {@code logger} is {@code null}
       */
      public static IoBuilder forLogger(final Logger logger) {
          return new IoBuilder(logger);
      }
  
      /**
       * Creates a new builder using a Logger name. The name provided is used to get a Logger from
       * {@link LogManager#getLogger(String)} which will be wrapped into a LoggerStream.
       *
       * @param loggerName the name of the Logger to wrap into a LoggerStream
       * @return a new IoBuilder
       */
      public static IoBuilder forLogger(final String loggerName) {
          return new IoBuilder(LogManager.getLogger(loggerName));
      }
  
      /**
       * Creates a new builder using a Logger named after a given Class. The Class provided is used to get a Logger from
       * {@link LogManager#getLogger(Class)} which will be wrapped into a LoggerStream.
       *
       * @param clazz the Class to use as the Logger name to wrap into a LoggerStream
       * @return a new IoBuilder
      */
     public static IoBuilder forLogger(final Class<?> clazz) {
         return new IoBuilder(LogManager.getLogger(clazz));
     }
 
     /**
      * Creates a new builder using a Logger named after the calling Class. This is equivalent to the following:
      * <pre>
      *     IoBuilder builder = IoBuilder.forLogger(LogManager.getLogger());
      * </pre>
      *
      * @return a new IoBuilder
      */
     public static IoBuilder forLogger() {
         return new IoBuilder(LogManager.getLogger(ReflectionUtil.getCallerClass(2)));
     }
 
     /**
      * Constructs a new IoBuilder for the given Logger. This method is provided for extensibility of this builder
      * class. The static factory methods should be used normally.
      *
      * @param logger the {@link ExtendedLogger} to wrap
      */
     protected IoBuilder(final Logger logger) {
         if (!(logger instanceof ExtendedLogger)) {
             throw new UnsupportedOperationException("The provided Logger [" + String.valueOf(logger) +
                 "] does not implement " + ExtendedLogger.class.getName());
         }
         this.logger = (ExtendedLogger) logger;
     }
 
     /**
      * Specifies the {@link Level} to log at. If no Level is configured, then the Level of the wrapped Logger will be
      * used.
      *
      * @param level the Level to use for logging
      * @return {@code this}
      */
     public IoBuilder setLevel(final Level level) {
         this.level = level;
         return this;
     }
 
     /**
      * Specifies an optional {@link Marker} to use in all logging messages. If no Marker is specified, then no Marker
      * will be used.
      *
      * @param marker the Marker to associate with all logging messages
      * @return {@code this}
      */
     public IoBuilder setMarker(final Marker marker) {
         this.marker = marker;
         return this;
     }
 
     /**
      * Specifies the fully qualified class name of the IO wrapper class implementation. This method should only be
      * used when making significant extensions to the provided classes in this component and is normally unnecessary.
      *
      * @param fqcn the fully qualified class name of the IO wrapper class being built
      * @return {@code this}
      */
     public IoBuilder setWrapperClassName(final String fqcn) {
         this.fqcn = fqcn;
         return this;
     }
 
     /**
      * Indicates whether or not a built {@link PrintWriter} or {@link PrintStream} should automatically flush when
      * one of the {@code println}, {@code printf}, or {@code format} methods are invoked, or when a new line character
      * is printed.
      *
      * @param autoFlush if {@code true}, then {@code println}, {@code printf}, and {@code format} will auto flush
      * @return {@code this}
      */
     public IoBuilder setAutoFlush(final boolean autoFlush) {
         this.autoFlush = autoFlush;
         return this;
     }
 
     /**
      * Enables or disables using a buffered variant of the desired IO class. If this is set to {@code true}, then the
      * instances returned by {@link #buildReader()} and {@link #buildInputStream()} can be safely cast (if necessary)
      * to {@link java.io.BufferedReader} and {@link java.io.BufferedInputStream} respectively. This option does not
      * have any effect on the other built variants.
      *
      * @param buffered indicates whether or not a wrapped {@link InputStream} or {@link Reader} should be buffered
      * @return {@code this}
      */
     public IoBuilder setBuffered(final boolean buffered) {
         this.buffered = buffered;
         return this;
     }
 
     /**
      * Configures the buffer size to use when building a {@link java.io.BufferedReader} or
      * {@link java.io.BufferedInputStream} LoggerStream.
      *
      * @param bufferSize the buffer size to use or a non-positive integer to use the default size
      * @return {@code this}
      */
     public IoBuilder setBufferSize(final int bufferSize) {
         this.bufferSize = bufferSize;
         return this;
     }
 
     /**
      * Specifies the character set to use when building an {@link InputStream}, {@link OutputStream}, or
      * {@link PrintStream}. If no character set is specified, then {@link java.nio.charset.Charset#defaultCharset()}
      * is used.
      *
      * @param charset the character set to use when building an InputStream, OutputStream, or PrintStream
      * @return {@code this}
      */
     public IoBuilder setCharset(final Charset charset) {
         this.charset = charset;
         return this;
     }
 
     /**
      * Configures a {@link Reader} to be wiretapped when building a Reader. This must be set to a non-{@code null}
      * value in order to call {@link #buildReader()}.
      *
      * @param reader the Reader to wiretap
      * @return {@code this}
      */
     public IoBuilder filter(final Reader reader) {
         this.reader = reader;
         return this;
     }
 
     /**
      * Configures a {@link Writer} to be written to in addition to the underlying Logger. If no Writer is specified,
      * then the built Writer or PrintWriter will only write to the underlying Logger.
      *
      * @param writer the Writer to write to in addition to the Logger
      * @return {@code this}
      */
     public IoBuilder filter(final Writer writer) {
         this.writer = writer;
         return this;
     }
 
     /**
      * Configures an {@link InputStream} to be wiretapped when building an InputStream. This must be set to a
      * non-{@code null} value in order to call {@link #buildInputStream()}.
      *
      * @param inputStream the InputStream to wiretap
      * @return {@code this}
      */
     public IoBuilder filter(final InputStream inputStream) {
         this.inputStream = inputStream;
         return this;
     }
 
     /**
      * Configures an {@link OutputStream} to be written to in addition to the underlying Logger. If no OutputStream is
      * specified, then the built OutputStream or PrintStream will only write to the underlying Logger.
      *
      * @param outputStream the OutputStream to write to in addition to the Logger
      * @return {@code this}
      */
     public IoBuilder filter(final OutputStream outputStream) {
         this.outputStream = outputStream;
         return this;
     }
 
     // TODO: could this builder use generics to infer the desired IO class?
 
     /**
      * Builds a new {@link Reader} that is wiretapped by its underlying Logger. If buffering is enabled, then a
      * {@link java.io.BufferedReader} will be returned.
      *
      * @return a new Reader wiretapped by a Logger
      * @throws IllegalStateException if no Reader was configured for this builder
      */
     public Reader buildReader() {
         final Reader in = requireNonNull(this.reader, "reader");
         if (this.buffered) {
             if (this.bufferSize > 0) {
                 return new LoggerBufferedReader(in, this.bufferSize, this.logger, this.fqcn, this.level, this.marker);
             }
             return new LoggerBufferedReader(in, this.logger, this.fqcn, this.level, this.marker);
         }
         return new LoggerReader(in, this.logger, this.fqcn, this.level, this.marker);
     }
 
     /**
      * Builds a new {@link Writer} that is backed by a Logger and optionally writes to another Writer as well. If no
      * Writer is configured for this builder, then the returned Writer will only write to its underlying Logger.
      *
      * @return a new Writer or {@link java.io.FilterWriter} backed by a Logger
      */
     public Writer buildWriter() {
         if (this.writer == null) {
             return new LoggerWriter(this.logger, this.fqcn, this.level, this.marker);
         }
         return new LoggerFilterWriter(this.writer, this.logger, this.fqcn, this.level, this.marker);
     }
 
     /**
      * Builds a new {@link PrintWriter} that is backed by a Logger and optionally writes to another Writer as well. If
      * no Writer is configured for this builder, then the returned PrintWriter will only write to its underlying
      * Logger.
      *
      * @return a new PrintWriter that optionally writes to another Writer in addition to its underlying Logger
      */
     public PrintWriter buildPrintWriter() {
         if (this.writer == null) {
             return new LoggerPrintWriter(this.logger, this.autoFlush, this.fqcn, this.level, this.marker);
         }
         return new LoggerPrintWriter(this.writer, this.autoFlush, this.logger, this.fqcn, this.level, this.marker);
     }
 
     /**
      * Builds a new {@link InputStream} that is wiretapped by its underlying Logger. If buffering is enabled, then a
      * {@link java.io.BufferedInputStream} will be returned.
      *
      * @return a new InputStream wiretapped by a Logger
      * @throws IllegalStateException if no InputStream was configured for this builder
      */
     public InputStream buildInputStream() {
         final InputStream in = requireNonNull(this.inputStream, "inputStream");
         if (this.buffered) {
             if (this.bufferSize > 0) {
                 return new LoggerBufferedInputStream(in, this.charset, this.bufferSize, this.logger, this.fqcn,
                     this.level, this.marker);
             }
             return new LoggerBufferedInputStream(in, this.charset, this.logger, this.fqcn, this.level, this.marker);
         }
         return new LoggerInputStream(in, this.charset, this.logger, this.fqcn, this.level, this.marker);
     }
 
     /**
      * Builds a new {@link OutputStream} that is backed by a Logger and optionally writes to another OutputStream as
      * well. If no OutputStream is configured for this builder, then the returned OutputStream will only write to its
      * underlying Logger.
      *
      * @return a new OutputStream that optionally writes to another OutputStream in addition to its underlying Logger
      */
     public OutputStream buildOutputStream() {
         if (this.outputStream == null) {
             return new LoggerOutputStream(this.logger, this.level, this.marker, this.charset, this.fqcn);
         }
         return new LoggerFilterOutputStream(this.outputStream, this.charset, this.logger, this.fqcn, this.level,
             this.marker);
     }
 
     /**
      * Builds a new {@link PrintStream} that is backed by a Logger and optionally writes to another OutputStream as
      * well. If no OutputStream is configured for this builder, then the returned PrintStream will only write to its
      * underlying Logger.
      *
      * @return a new PrintStream that optionally writes to another OutputStream in addition to its underlying Logger
      * @throws LoggingException if the configured character set is unsupported by {@link PrintStream}
      */
     public PrintStream buildPrintStream() {
         try {
             if (this.outputStream == null) {
                 return new LoggerPrintStream(this.logger, this.autoFlush, this.charset, this.fqcn, this.level,
                     this.marker);
             }
             return new LoggerPrintStream(this.outputStream, this.autoFlush, this.charset, this.logger, this.fqcn,
                 this.level, this.marker);
         } catch (final UnsupportedEncodingException e) {
             // this exception shouldn't really happen since we use Charset and not String
             throw new LoggingException(e);
         }
     }
 
     private static <T> T requireNonNull(final T obj, final String name) {
         if (obj == null) {
             throw new IllegalStateException("The property " + name + " was not set");
         }
         return obj;
     }
 
 }