com.spotify.mobius.extras.connections.DisconnectOnNullDimapConnection Maven / Gradle / Ivy

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/*
 * -\-\-
 * Mobius
 * --
 * Copyright (c) 2017-2020 Spotify AB
 * --
 * Licensed under the Apache 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://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 com.spotify.mobius.extras.connections;

import static com.spotify.mobius.internal_util.Preconditions.checkNotNull;

import com.spotify.mobius.Connectable;
import com.spotify.mobius.Connection;
import com.spotify.mobius.extras.NullValuedFunction;
import com.spotify.mobius.functions.Consumer;
import com.spotify.mobius.functions.Function;

/** A {@link Connection} that implements dimap. */
public class DisconnectOnNullDimapConnection implements Connection {

  public static  Connection create(
      NullValuedFunction aToB,
      Function cToD,
      Connectable connectable,
      Consumer output) {
    return new DisconnectOnNullDimapConnection<>(
        checkNotNull(aToB), checkNotNull(cToD), checkNotNull(connectable), checkNotNull(output));
  }

  private final NullValuedFunction aToB;
  private final Function cToD;
  private final Connectable connectable;
  private final Consumer output;
  private Connection currentDelegate;

  private DisconnectOnNullDimapConnection(
      NullValuedFunction aToB,
      Function cToD,
      Connectable connectable,
      Consumer output) {
    this.aToB = aToB;
    this.cToD = cToD;
    this.connectable = connectable;
    this.output = output;
  }

  @Override
  public void accept(A a) {
    B b = aToB.apply(a);
    if (b != null) {
      if (currentDelegate == null) {
        currentDelegate =
            connectable.connect(
                new Consumer() {
                  @Override
                  public void accept(C c) {
                    final D d = cToD.apply(c);
                    output.accept(d);
                  }
                });
      }
      currentDelegate.accept(b);
    } else if (currentDelegate != null) {
      currentDelegate.dispose();
      currentDelegate = null;
    }
  }

  @Override
  public void dispose() {
    if (currentDelegate != null) {
      currentDelegate.dispose();
    }
  }
}