package org.apache.archiva.common;
   
   /*
    * 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.
   */
  
  import java.util.function.Function;
  
  /**
   * This is a class that can be used for the Try monad
   *
   * The Try monad is able to collect exceptions during processing
   * of a stream.
   *
   *
   *
   */
  public abstract class Try<V> {
  
      private Try() {
  
      }
  
      public abstract Boolean isSuccess();
  
      public abstract Boolean isFailure();
  
      public abstract void throwException();
  
      /**
       * Returns the value if this is a success instance. Otherwise throws
       * a runtime exception with the stored throwable as cause.
       *
       * @return The value
       */
      public abstract V get();
  
      /**
       * Returns the throwable that is stored in the failure.
       *
       * @return The Throwable or null.
       */
      public abstract Throwable getError();
  
  
      /**
       * A mapping method for mapping the current instance to a new type.
       *
       * @param fn
       * @param <U>
       * @return
       */
      public <U> Try<U> map(Function<? super V, U> fn) {
          try {
              return Try.success(fn.apply(get()));
          } catch (Throwable e) {
              return Try.failure(e);
          }
      }
  
      /**
       * This is the bind method.
       * If this instance is success the function will be applied. If any error occurs
       * a failure instance will be returned.
       * If this instance is failure a new failure will be returned.
       *
       * @param fn
       * @param <U>
       * @return
       */
      public <U> Try<U> flatMap(Function<? super V, Try<U>> fn) {
          try {
              return fn.apply(get());
          } catch (Throwable t) {
              return Try.failure(t);
          }
      }
  
      public static <V> Try<V> failure(String message) {
  
          return new Failure<>(message);
  
      }
  
     public static <V> Try<V> failure(String message, Throwable e) {
 
         return new Failure<>(message, e);
 
     }
 
     /**
      * If you need type coercion, you should call this method as
      *  Try.&lt;YOUR_TYPE&gt;failure(e)
      *
      *
      *
      * @param e The exception that is thrown
      * @param <V> The generic type this monad keeps
      * @return A new Try instance that represents a failure.
      */
     public static <V> Try<V> failure(Throwable e) {
 
         return new Failure<>(e);
 
     }
 
 
     /**
      * Returns a instance for the success case.
      *
      * @param value The value that should be stored.
      * @param <V> The return type
      * @return A new Try instance with the given value
      */
     public static <V> Try<V> success(V value) {
 
         return new Success<>(value);
 
     }
 
     private static class Failure<V> extends Try<V> {
 
         private Throwable exception;
 
         public Failure(String message) {
 
             super();
 
             this.exception = new IllegalStateException(message);
 
         }
 
         public Failure(String message, Throwable e) {
 
             super();
 
             this.exception = new IllegalStateException(message, e);
 
         }
 
         public Failure(Throwable e) {
 
             super();
 
             this.exception = new IllegalStateException(e);
 
         }
 
         @Override
 
         public Boolean isSuccess() {
 
             return false;
 
         }
 
         @Override
 
         public Boolean isFailure() {
 
             return true;
 
         }
 
         @Override
 
         public void throwException() {
 
             throw new RuntimeException(this.exception);
 
         }
 
         @Override
         public V get() {
             throw new RuntimeException(this.exception);
         }
 
         @Override
         public Throwable getError() {
             return exception;
         }
     }
 
     private static class Success<V> extends Try<V> {
 
         private V value;
 
         public Success(V value) {
 
             super();
 
             this.value = value;
 
         }
 
         @Override
 
         public Boolean isSuccess() {
 
             return true;
 
         }
 
         @Override
 
         public Boolean isFailure() {
 
             return false;
 
         }
 
         @Override
 
         public void throwException() {
 
             //log.error("Method throwException() called on a Success instance");
 
         }
 
         @Override
         public V get() {
             return value;
         }
 
         @Override
         public Throwable getError() {
             return null;
         }
     }
 
     // various method such as map an flatMap
 
 
     @Override
     public String toString() {
         return isSuccess() ? "true: "+get() : "false: "+ getError().getMessage();
     }
 }