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/**
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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.opencastproject.util.data.functions;

import static org.opencastproject.util.data.Monadics.mlist;
import static org.opencastproject.util.data.Option.none;
import static org.opencastproject.util.data.Option.some;

import org.opencastproject.util.data.Effect;
import org.opencastproject.util.data.Function;
import org.opencastproject.util.data.Function0;
import org.opencastproject.util.data.Function2;
import org.opencastproject.util.data.Option;

import java.util.ArrayList;
import java.util.List;

/** {@link Option} related functions. */
public final class Options {
  private Options() {
  }

  /** m (m a) -> m a */
  public static  Option join(Option> a) {
    return a.bind(Functions.> identity());
  }

  public static  Function, List> asList() {
    return new Function, List>() {
      @Override
      public List apply(Option a) {
        return a.list();
      }
    };
  }

  public static  Function> never() {
    return new Function>() {
      @Override
      public Option apply(A a) {
        return none();
      }
    };
  }

  public static  Function0> never2() {
    return new Function0>() {
      @Override
      public Option apply() {
        return none();
      }
    };
  }

  /** Function that turns true into some(true) and false into none. */
  public static final Function> toOption = new Function>() {
    @Override
    public Option apply(Boolean a) {
      return a ? some(true) : Option. none();
    }
  };

  /** Returns some(message) if predicate is false, none otherwise. */
  public static Option toOption(boolean predicate, String message) {
    return predicate ? Option. none() : some(message);
  }

  /** Sequence a list of options. [Option a] -> Option [a] */
  public static  Option> sequenceOpt(List> as) {
    final List seq = mlist(as).foldl(new ArrayList(), new Function2, Option, List>() {
      @Override
      public List apply(List sum, Option o) {
        for (A a : o) {
          sum.add(a);
          return sum;
        }
        return sum;
      }
    });
    return some(seq);
  }

  /** Map g over the result of f. */
  public static  Function> map(final Function> f,
          final Function g) {
    return new Function>() {
      @Override
      public Option apply(A a) {
        return f.apply(a).map(g);
      }
    };
  }

  /** Apply effect e to the result of f which is then returned. */
  public static  Function> foreach(final Function> f,
          final Effect e) {
    return new Function>() {
      @Override
      public Option apply(A a) {
        return (Option) f.apply(a).foreach(e);
      }
    };
  }

  /** {@link org.opencastproject.util.data.Option#isNone()} as a function. */
  public static  Function, Boolean> isNone() {
    return new Function, Boolean>() {
      @Override
      public Boolean apply(Option a) {
        return a.isNone();
      }
    };
  }

  /** {@link org.opencastproject.util.data.Option#isSome()} as a function. */
  public static  Function, Boolean> isSome() {
    return new Function, Boolean>() {
      @Override
      public Boolean apply(Option a) {
        return a.isSome();
      }
    };
  }

  public static  Function, A> getOrElse(final A none) {
    return new Function, A>() {
      @Override public A apply(Option as) {
        return as.getOrElse(none);
      }
    };
  }

  public static  Function, A> getF() {
    return new Function, A>() {
      @Override public A apply(Option as) {
        return as.get();
      }
    };
  }
}