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

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/*
 * Copyright (c) 2018-2019, Antonio Gabriel Muñoz Conejo 
 * Distributed under the terms of the MIT License
 */
package com.github.tonivade.purefun.data;

import static java.util.Collections.emptySet;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.collectingAndThen;

import java.io.Serializable;
import java.util.Arrays;
import java.util.HashSet;
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.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(element -> mapper.apply(element).stream()));
  }

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

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

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

  @SafeVarargs
  static  ImmutableSet of(T... elements) {
    return new JavaBasedImmutableSet<>(new LinkedHashSet<>(Arrays.asList(elements)));
  }

  static  ImmutableSet empty() {
    return new JavaBasedImmutableSet<>(emptySet());
  }

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

  final class JavaBasedImmutableSet implements ImmutableSet, Serializable {

    private static final long serialVersionUID = -4111867323115030715L;

    private final Set backend;

    private JavaBasedImmutableSet(Set backend) {
      this.backend = requireNonNull(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) {
      Set newSet = toSet();
      newSet.add(element);
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet appendAll(Sequence other) {
      Set newSet = toSet();
      for (E element : other) {
        newSet.add(element);
      }
      return new JavaBasedImmutableSet<>(newSet);
    }

    @Override
    public ImmutableSet removeAll(Sequence other) {
      Set newSet = toSet();
      for (E element : other) {
        newSet.remove(element);
      }
      return new JavaBasedImmutableSet<>(newSet);
    }

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

    @Override
    public ImmutableSet union(ImmutableSet other) {
      Set newSet = toSet();
      newSet.addAll(other.toSet());
      return new JavaBasedImmutableSet<>(newSet);
    }

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

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

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

    @Override
    public Set toSet() {
      return new HashSet<>(backend);
    }

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

    @Override
    public boolean equals(Object obj) {
      return Equal.of(this)
          .append((a, b) -> Objects.equals(a.backend, b.backend))
          .applyTo(obj);
    }

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