com.github.tonivade.purefun.data.ImmutableSet Maven / Gradle / Ivy

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/*
 * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo 
 * Distributed under the terms of the MIT License
 */
package com.github.tonivade.purefun.data;

import static java.util.Collections.unmodifiableSet;
import static java.util.stream.Collectors.collectingAndThen;

import java.io.Serializable;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Objects;
import java.util.Set;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import com.github.tonivade.purefun.Equal;
import com.github.tonivade.purefun.Function1;
import com.github.tonivade.purefun.Kind;
import com.github.tonivade.purefun.Matcher1;

public interface ImmutableSet extends Sequence {

  Set toSet();

  @Override
  ImmutableSet append(E element);
  @Override
  ImmutableSet remove(E element);
  @Override
  ImmutableSet appendAll(Sequence other);
  @Override
  ImmutableSet removeAll(Sequence other);

  @Override
  ImmutableSet reverse();

  ImmutableSet union(ImmutableSet other);
  ImmutableSet intersection(ImmutableSet other);
  ImmutableSet difference(ImmutableSet other);

  @Override
  default  ImmutableSet map(Function1 mapper) {
    return ImmutableSet.from(stream().map(mapper::apply));
  }

  @Override
  default  ImmutableSet flatMap(Function1> mapper) {
    return ImmutableSet.from(stream().flatMap(mapper.andThen(SequenceOf::narrowK).andThen(Sequence::stream)::apply));
  }

  @Override
  default ImmutableSet filter(Matcher1 matcher) {
    return ImmutableSet.from(stream().filter(matcher::match));
  }

  @Override
  default ImmutableSet filterNot(Matcher1 matcher) {
    return filter(matcher.negate());
  }

  static  ImmutableSet from(Iterable iterable) {
    return from(Sequence.asStream(iterable.iterator()));
  }

  static  ImmutableSet from(Stream stream) {
    return new JavaBasedImmutableSet<>(stream.collect(Collectors.toCollection(LinkedHashSet::new)));
  }

  @SafeVarargs
  static  ImmutableSet of(T... elements) {
    return from(Arrays.stream(elements));
  }

  @SuppressWarnings("unchecked")
  static  ImmutableSet empty() {
    return (ImmutableSet) JavaBasedImmutableSet.EMPTY;
  }

  static  Collector> toImmutableSet() {
    return collectingAndThen(Collectors.toCollection(LinkedHashSet::new), JavaBasedImmutableSet::new);
  }

  final class JavaBasedImmutableSet implements ImmutableSet, Serializable {

    private static final long serialVersionUID = -4111867323115030715L;

    public static final ImmutableSet EMPTY = new JavaBasedImmutableSet<>(new LinkedHashSet<>());

    private static final Equal> EQUAL = 
        Equal.>of().comparing(x -> x.backend);

    private final Set backend;

    private JavaBasedImmutableSet(LinkedHashSet backend) {
      this.backend = unmodifiableSet(backend);
    }

    @Override
    public int size() {
      return backend.size();
    }

    @Override
    public boolean contains(E element) {
      return backend.contains(element);
    }

    @Override
    public ImmutableSet reverse() {
      return this;
    }

    @Override
    public ImmutableSet append(E element) {
      LinkedHashSet newSet = copy();
      newSet.add(element);
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet remove(E element) {
      LinkedHashSet newSet = copy();
      newSet.remove(element);
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet appendAll(Sequence other) {
      LinkedHashSet newSet = copy();
      newSet.addAll(other.toCollection());
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet removeAll(Sequence other) {
      LinkedHashSet newSet = copy();
      newSet.removeAll(other.toCollection());
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet union(ImmutableSet other) {
      return appendAll(other);
    }

    @Override
    public ImmutableSet intersection(ImmutableSet other) {
      LinkedHashSet newSet = copy();
      newSet.retainAll(other.toCollection());
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet difference(ImmutableSet other) {
      LinkedHashSet newSet = copy();
      newSet.removeAll(other.toCollection());
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public Iterator iterator() {
      return backend.iterator();
    }

    @Override
    public Set toSet() {
      return copy();
    }

    @Override
    public int hashCode() {
      return Objects.hash(backend);
    }

    @Override
    public boolean equals(Object obj) {
      return EQUAL.applyTo(this, obj);
    }

    @Override
    public String toString() {
      return "ImmutableSet(" + backend + ")";
    }

    private LinkedHashSet copy() {
      return new LinkedHashSet<>(backend);
    }
  }
}