com.github.tonivade.purefun.Function1 Maven / Gradle / Ivy

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/*
 * Copyright (c) 2018-2020, Antonio Gabriel Muñoz Conejo 
 * Distributed under the terms of the MIT License
 */
package com.github.tonivade.purefun;

import static com.github.tonivade.purefun.data.Sequence.listOf;

import java.util.Optional;
import java.util.stream.Stream;

import com.github.tonivade.purefun.concurrent.Future;
import com.github.tonivade.purefun.data.Sequence;
import com.github.tonivade.purefun.type.Either;
import com.github.tonivade.purefun.type.Id;
import com.github.tonivade.purefun.type.Option;
import com.github.tonivade.purefun.type.Try;

/**
 * This interface represents a function with a single parameter. Similar to {@link java.util.function.Function}.
 * The function can throws checked exceptions, but calling {@code apply()} method, the exception is sneaky thrown. So, it
 * can be used as a higher order function in {@link java.util.stream.Stream} or {@link java.util.Optional} API.
 * @param  type of function parameter
 * @param  type of return value
 */
@HigherKind
@FunctionalInterface
public interface Function1 extends Recoverable {

  default R apply(A value) {
    try {
      return run(value);
    } catch (Throwable t) {
      return sneakyThrow(t);
    }
  }

  R run(A value) throws Throwable;

  default  Function1 andThen(Function1 after) {
    return value -> after.apply(apply(value));
  }

  default  Function1 compose(Function1 before) {
    return value -> apply(before.apply(value));
  }

  default  Function1 flatMap(Function1> after) {
    return value -> after.apply(apply(value)).apply(value);
  }

  default Function1> liftOptional() {
    return value -> Optional.ofNullable(apply(value));
  }

  default Function1> liftOption() {
    return value -> Option.of(() -> apply(value));
  }

  default Function1> liftTry() {
    return value -> Try.of(() -> apply(value));
  }

  default Function1> liftId() {
    return value -> Id.of(apply(value));
  }

  default Function1> liftFuture() {
    return value -> Future.async(() -> apply(value));
  }

  default Function1> liftEither() {
    return liftTry().andThen(Try::toEither);
  }

  default  Function1> liftRight() {
    return value -> Either.right(apply(value));
  }

  default  Function1> liftLeft() {
    return value -> Either.left(apply(value));
  }

  default Function1> sequence() {
    return value -> listOf(apply(value));
  }

  default Function1> stream() {
    return value -> Stream.of(apply(value));
  }

  default Function1 memoized() {
    return new MemoizedFunction<>(this);
  }

  default PartialFunction1 partial(Matcher1 isDefined) {
    return new PartialFunction1() {
      @Override
      public boolean isDefinedAt(A value) {
        return isDefined.match(value);
      }

      @Override
      public R apply(A value) {
        return Function1.this.apply(value);
      }
    };
  }

  static  Function1 identity() {
    return value -> value;
  }

  static  Function1 cons(T cons) {
    return ignore -> cons;
  }

  static  Function1 fail(Producer supplier) {
    return ignore -> { throw supplier.get(); };
  }

  static  Function1 of(Function1 reference) {
    return reference;
  }
}