/*******************************************************************************
    * Copyright (c) 2010, 2013 Sonatype, Inc.
    * All rights reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
    * Contributors:
    *    Sonatype, Inc. - initial API and implementation
   *******************************************************************************/
  package org.eclipse.aether.graph;
  
  import java.util.AbstractSet;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  import org.eclipse.aether.artifact.Artifact;
  
  /**
   * A dependency to some artifact. <em>Note:</em> Instances of this class are immutable and the exposed mutators return
   * new objects rather than changing the current instance.
   */
  public final class Dependency
  {
  
      private final Artifact artifact;
  
      private final String scope;
  
      private final Boolean optional;
  
      private final Set<Exclusion> exclusions;
  
      /**
       * Creates a mandatory dependency on the specified artifact with the given scope.
       * 
       * @param artifact The artifact being depended on, must not be {@code null}.
       * @param scope The scope of the dependency, may be {@code null}.
       */
      public Dependency( Artifact artifact, String scope )
      {
          this( artifact, scope, false );
      }
  
      /**
       * Creates a dependency on the specified artifact with the given scope.
       * 
       * @param artifact The artifact being depended on, must not be {@code null}.
       * @param scope The scope of the dependency, may be {@code null}.
       * @param optional A flag whether the dependency is optional or mandatory, may be {@code null}.
       */
      public Dependency( Artifact artifact, String scope, Boolean optional )
      {
          this( artifact, scope, optional, null );
      }
  
      /**
       * Creates a dependency on the specified artifact with the given scope and exclusions.
       * 
       * @param artifact The artifact being depended on, must not be {@code null}.
       * @param scope The scope of the dependency, may be {@code null}.
       * @param optional A flag whether the dependency is optional or mandatory, may be {@code null}.
       * @param exclusions The exclusions that apply to transitive dependencies, may be {@code null} if none.
       */
      public Dependency( Artifact artifact, String scope, Boolean optional, Collection<Exclusion> exclusions )
      {
          this( artifact, scope, Exclusions.copy( exclusions ), optional );
      }
  
      private Dependency( Artifact artifact, String scope, Set<Exclusion> exclusions, Boolean optional )
      {
          // NOTE: This constructor assumes immutability of the provided exclusion collection, for internal use only
          if ( artifact == null )
          {
              throw new IllegalArgumentException( "no artifact specified for dependency" );
          }
          this.artifact = artifact;
          this.scope = ( scope != null ) ? scope : "";
          this.optional = optional;
          this.exclusions = exclusions;
      }
  
      /**
       * Gets the artifact being depended on.
       * 
       * @return The artifact, never {@code null}.
       */
      public Artifact getArtifact()
      {
          return artifact;
      }
  
      /**
       * Sets the artifact being depended on.
       * 
      * @param artifact The artifact, must not be {@code null}.
      * @return The new dependency, never {@code null}.
      */
     public Dependency setArtifact( Artifact artifact )
     {
         if ( this.artifact.equals( artifact ) )
         {
             return this;
         }
         return new Dependency( artifact, scope, exclusions, optional );
     }
 
     /**
      * Gets the scope of the dependency. The scope defines in which context this dependency is relevant.
      * 
      * @return The scope or an empty string if not set, never {@code null}.
      */
     public String getScope()
     {
         return scope;
     }
 
     /**
      * Sets the scope of the dependency, e.g. "compile".
      * 
      * @param scope The scope of the dependency, may be {@code null}.
      * @return The new dependency, never {@code null}.
      */
     public Dependency setScope( String scope )
     {
         if ( this.scope.equals( scope ) || ( scope == null && this.scope.length() <= 0 ) )
         {
             return this;
         }
         return new Dependency( artifact, scope, exclusions, optional );
     }
 
     /**
      * Indicates whether this dependency is optional or not. Optional dependencies can be ignored in some contexts.
      * 
      * @return {@code true} if the dependency is (definitively) optional, {@code false} otherwise.
      */
     public boolean isOptional()
     {
         return Boolean.TRUE.equals( optional );
     }
 
     /**
      * Gets the optional flag for the dependency. Note: Most clients will usually call {@link #isOptional()} to
      * determine the optional flag, this method is for advanced use cases where three-valued logic is required.
      * 
      * @return The optional flag or {@code null} if unspecified.
      */
     public Boolean getOptional()
     {
         return optional;
     }
 
     /**
      * Sets the optional flag for the dependency.
      * 
      * @param optional {@code true} if the dependency is optional, {@code false} if the dependency is mandatory, may be
      *            {@code null} if unspecified.
      * @return The new dependency, never {@code null}.
      */
     public Dependency setOptional( Boolean optional )
     {
         if ( eq( this.optional, optional ) )
         {
             return this;
         }
         return new Dependency( artifact, scope, exclusions, optional );
     }
 
     /**
      * Gets the exclusions for this dependency. Exclusions can be used to remove transitive dependencies during
      * resolution.
      * 
      * @return The (read-only) exclusions, never {@code null}.
      */
     public Collection<Exclusion> getExclusions()
     {
         return exclusions;
     }
 
     /**
      * Sets the exclusions for the dependency.
      * 
      * @param exclusions The exclusions, may be {@code null}.
      * @return The new dependency, never {@code null}.
      */
     public Dependency setExclusions( Collection<Exclusion> exclusions )
     {
         if ( hasEquivalentExclusions( exclusions ) )
         {
             return this;
         }
         return new Dependency( artifact, scope, optional, exclusions );
     }
 
     private boolean hasEquivalentExclusions( Collection<Exclusion> exclusions )
     {
         if ( exclusions == null || exclusions.isEmpty() )
         {
             return this.exclusions.isEmpty();
         }
         if ( exclusions instanceof Set )
         {
             return this.exclusions.equals( exclusions );
         }
         return exclusions.size() >= this.exclusions.size() && this.exclusions.containsAll( exclusions )
             && exclusions.containsAll( this.exclusions );
     }
 
     @Override
     public String toString()
     {
         return String.valueOf( getArtifact() ) + " (" + getScope() + ( isOptional() ? "?" : "" ) + ")";
     }
 
     @Override
     public boolean equals( Object obj )
     {
         if ( obj == this )
         {
             return true;
         }
         else if ( obj == null || !getClass().equals( obj.getClass() ) )
         {
             return false;
         }
 
         Dependency that = (Dependency) obj;
 
         return artifact.equals( that.artifact ) && scope.equals( that.scope ) && eq( optional, that.optional )
             && exclusions.equals( that.exclusions );
     }
 
     private static <T> boolean eq( T o1, T o2 )
     {
         return ( o1 != null ) ? o1.equals( o2 ) : o2 == null;
     }
 
     @Override
     public int hashCode()
     {
         int hash = 17;
         hash = hash * 31 + artifact.hashCode();
         hash = hash * 31 + scope.hashCode();
         hash = hash * 31 + ( optional != null ? optional.hashCode() : 0 );
         hash = hash * 31 + exclusions.size();
         return hash;
     }
 
     private static class Exclusions
         extends AbstractSet<Exclusion>
     {
 
         private final Exclusion[] exclusions;
 
         public static Set<Exclusion> copy( Collection<Exclusion> exclusions )
         {
             if ( exclusions == null || exclusions.isEmpty() )
             {
                 return Collections.emptySet();
             }
             return new Exclusions( exclusions );
         }
 
         private Exclusions( Collection<Exclusion> exclusions )
         {
             if ( exclusions.size() > 1 && !( exclusions instanceof Set ) )
             {
                 exclusions = new LinkedHashSet<Exclusion>( exclusions );
             }
             this.exclusions = exclusions.toArray( new Exclusion[exclusions.size()] );
         }
 
         @Override
         public Iterator<Exclusion> iterator()
         {
             return new Iterator<Exclusion>()
             {
 
                 private int cursor = 0;
 
                 public boolean hasNext()
                 {
                     return cursor < exclusions.length;
                 }
 
                 public Exclusion next()
                 {
                     try
                     {
                         Exclusion exclusion = exclusions[cursor];
                         cursor++;
                         return exclusion;
                     }
                     catch ( IndexOutOfBoundsException e )
                     {
                         throw new NoSuchElementException();
                     }
                 }
 
                 public void remove()
                 {
                     throw new UnsupportedOperationException();
                 }
 
             };
         }
 
         @Override
         public int size()
         {
             return exclusions.length;
         }
 
     }
 
 }