Implement more flows ops methods part 2

* interleave
* mapConcat
* mapPar
* mapParUnordered
* sliding
* alsoTo
* alsoToTap

flows/src/main/java/com/softwaremill/jox/flows/Flows.java

@@ -1,18 +1,26 @@
 package com.softwaremill.jox.flows;
 
-import com.softwaremill.jox.Source;
-import com.softwaremill.jox.structured.Fork;
+import static com.softwaremill.jox.structured.Scopes.unsupervised;
 
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
 import java.util.function.Supplier;
 
+import com.softwaremill.jox.Channel;
+import com.softwaremill.jox.ChannelClosed;
+import com.softwaremill.jox.ChannelDone;
+import com.softwaremill.jox.ChannelError;
+import com.softwaremill.jox.Source;
+import com.softwaremill.jox.structured.Fork;
+
 public final class Flows {
 
     private Flows() {}
@@ -222,4 +230,82 @@ public static <T> Flow<T> failed(Exception t) {
             throw t;
         });
     }
+
+    /**
+     * Sends a given number of elements (determined by `segmentSize`) from each flow in `flows` to the returned flow and repeats. The order
+     * of elements in all flows is preserved.
+     * <p>
+     * If any of the flows is done before the others, the behavior depends on the `eagerComplete` flag. When set to `true`, the returned flow
+     * is completed immediately, otherwise the interleaving continues with the remaining non-completed flows. Once all but one flows are
+     * complete, the elements of the remaining non-complete flow are emitted by the returned flow.
+     * <p>
+     * The provided flows are run concurrently and asynchronously.
+     *
+     * @param flows
+     *   The flows whose elements will be interleaved.
+     * @param segmentSize
+     *   The number of elements sent from each flow before switching to the next one.
+     * @param eagerComplete
+     *   If `true`, the returned flow is completed as soon as any of the flows completes. If `false`, the interleaving continues with the
+     *   remaining non-completed flows.
+     */
+    public static <T> Flow<T> interleaveAll(List<Flow<T>> flows, int segmentSize, boolean eagerComplete, int bufferCapacity) {
+        if (flows.isEmpty()) {
+            return Flows.empty();
+        } else if (flows.size() == 1) {
+            return flows.getFirst();
+        } else {
+            return usingEmit(emit -> {
+                Channel<T> results = new Channel<>(bufferCapacity);
+                unsupervised(scope -> {
+                    scope.forkUnsupervised(() -> {
+                        List<Source<T>> availableSources = new ArrayList<>(flows.stream()
+                                .map(flow -> flow.runToChannel(scope))
+                                .toList());
+                        int currentSourceIndex = 0;
+                        int elementsRead = 0;
+
+                        while (true) {
+                            var received = availableSources.get(currentSourceIndex).receiveOrClosed();
+                            if (received instanceof ChannelDone done) {
+                                ///  channel is done, remove it from the list of available sources
+                                availableSources.remove(currentSourceIndex);
+                                currentSourceIndex = currentSourceIndex == 0 ? availableSources.size() - 1 : currentSourceIndex - 1;
+
+                                // if all sources are done, or eagerComplete break the loop
+                                if (eagerComplete || availableSources.isEmpty()) {
+                                    results.doneOrClosed();
+                                    break;
+                                } else {
+                                    // switch to the next source
+                                    currentSourceIndex = (currentSourceIndex + 1) % availableSources.size();
+                                    elementsRead = 0;
+                                }
+                            } else if (received instanceof ChannelError(Throwable cause)) {
+                                // if any source fails, propagate the error
+                                results.errorOrClosed(cause);
+                                break;
+                            } else {
+                                elementsRead++;
+
+                                // switch to the next source when segmentSize is reached and there are more sources available
+                                if (elementsRead == segmentSize && availableSources.size() > 1) {
+                                    currentSourceIndex = (currentSourceIndex + 1) % availableSources.size();
+                                    elementsRead = 0;
+                                }
+                                //noinspection unchecked
+                                Object result = results.sendOrClosed((T) received);
+                                if (result instanceof ChannelClosed) {
+                                    break;
+                                }
+                            }
+                        }
+                        return null;
+                    });
+                    FlowEmit.channelToEmit(results, emit);
+                    return null;
+                });
+            });
+        }
+    }
 }

flows/src/test/java/com/softwaremill/jox/flows/FlowAlsoToTest.java

@@ -0,0 +1,244 @@
+package com.softwaremill.jox.flows;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.lessThan;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.stream.IntStream;
+
+import com.softwaremill.jox.Channel;
+import com.softwaremill.jox.ChannelClosedException;
+import com.softwaremill.jox.ChannelDone;
+import com.softwaremill.jox.ChannelError;
+import com.softwaremill.jox.structured.Scopes;
+import org.junit.jupiter.api.Test;
+
+public class FlowAlsoToTest {
+
+    @Test
+    void alsoTo_shouldSendToBothSinks() throws Exception {
+        // given
+        var c = new Channel<Integer>(10);
+
+        // when
+        List<Integer> result = Flows.fromValues(1, 2, 3)
+                .alsoTo(c)
+                .runToList();
+
+        // then
+        assertEquals(List.of(1, 2, 3), result);
+        assertEquals(List.of(1, 2, 3), c.toList());
+    }
+
+    @Test
+    void alsoTo_shouldSendToBothSinksAndNotHangWhenOtherSinkIsRendezvousChannel() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var c = new Channel<Integer>();
+            var f = scope.fork(c::toList);
+
+            // when
+            List<Integer> result = Flows.fromValues(1, 2, 3, 4, 5)
+                    .alsoTo(c)
+                    .runToList();
+
+            // then
+            assertEquals(List.of(1, 2, 3, 4, 5), result);
+            assertEquals(List.of(1, 2, 3, 4, 5), f.join());
+            return null;
+        });
+    }
+
+    @Test
+    void alsoTo_shouldCloseMainFlowWhenOtherCloses() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var c = new Channel<Integer>();
+            scope.fork(() -> {
+                var list = List.of(c.receiveOrClosed(), c.receiveOrClosed(), c.receiveOrClosed());
+                c.doneOrClosed();
+                // a send() from the main thread might be waiting - we need to consume that, and only then the main thread
+                // will discover that the channel is closed
+                c.receiveOrClosed();
+                return list;
+            });
+            Flow<Integer> flow = Flows.iterate(1, i -> i + 1)
+                    .take(100)
+                    .alsoTo(c);
+
+            // when & then
+            assertThrows(ChannelClosedException.class, flow::runToList);
+            return null;
+        });
+    }
+
+    @Test
+    void alsoTo_shouldCloseMainFlowWithErrorWhenOtherErrors() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var c = new Channel<Integer>(1);
+            var f = scope.fork(() -> {
+                c.receiveOrClosed();
+                c.receiveOrClosed();
+                c.receiveOrClosed();
+                c.errorOrClosed(new IllegalStateException());
+                return null;
+            });
+
+            Flow<Integer> flow = Flows.iterate(1, i -> i + 1)
+                    .take(100)
+                    .alsoTo(c);
+
+            // when & then
+            assertThrows(ChannelClosedException.class, flow::runToList);
+            f.join();
+            return null;
+        });
+    }
+
+    @Test
+    void alsoTo_shouldCloseOtherChannelWithErrorWhenMainErrors() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var other = new Channel<Integer>(0);
+            var forkOther = scope.forkUnsupervised(other::toList);
+
+            Flow<Integer> flow = Flows.iterate(1, i -> i + 1)
+                    .take(100)
+                    .concat(Flows.failed(new IllegalStateException()))
+                    .alsoTo(other);
+
+            // when & then
+            assertThrows(IllegalStateException.class, flow::runToList);
+            assertThrows(ExecutionException.class, forkOther::join);
+            return null;
+        });
+    }
+
+    @Test
+    void alsoToTap_shouldSendToBothSinksWhenOtherIsFaster() throws Exception {
+        // given
+        var other = new Channel<Integer>(10);
+        Flow<Integer> flow = Flows
+                .fromValues(1, 2, 3)
+                .alsoToTap(other)
+                .tap(v -> {
+                    try {
+                        Thread.sleep(50);
+                    } catch (InterruptedException e) {
+                        throw new RuntimeException(e);
+                    }
+                });
+
+        // when & then
+        assertEquals(List.of(1, 2, 3), flow.runToList());
+        assertEquals(List.of(1, 2, 3), other.toList());
+    }
+
+    @Test
+    void alsoTapTo_shouldSendToBothSinksWhenOtherIsSlower() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var other = new Channel<Integer>();
+            var slowConsumerFork = scope.fork(() -> {
+                var consumed = new LinkedList<>();
+                while (true) {
+                    Thread.sleep(100);
+                    var result = other.receiveOrClosed();
+                    if (result instanceof ChannelDone || result instanceof ChannelError) {
+                        break;
+                    } else {
+                        consumed.add(result);
+                    }
+                }
+                return consumed;
+            });
+            var main = new Channel<Integer>();
+            scope.fork(() -> {
+                for (int i = 1; i <= 20; i++) {
+                    main.send(i);
+                    Thread.sleep(10);
+                }
+                main.done();
+                return null;
+            });
+
+            // when
+            List<Integer> result = Flows.fromSource(main).alsoToTap(other).runToList();
+
+            // then
+            assertEquals(IntStream.rangeClosed(1, 20).boxed().toList(), result);
+            assertThat(slowConsumerFork.join(), hasSize(lessThan(10)));
+            return null;
+        });
+    }
+
+    @Test
+    void alsoTapTo_shouldNotFailTheFlowWhenTheOtherSinkFails() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var other = new Channel<Integer>();
+            var f = scope.fork(() -> {
+                var v = other.receiveOrClosed();
+                other.error(new RuntimeException("boom!"));
+                return v;
+            });
+
+            // when
+            List<Integer> result = Flows
+                    .iterate(1, i -> i + 1)
+                    .take(10)
+                    .tap(v -> {
+                        try {
+                            Thread.sleep(10);
+                        } catch (InterruptedException e) {
+                            throw new RuntimeException(e);
+                        }
+                    })
+                    .alsoToTap(other)
+                    .runToList();
+
+            // then
+            assertEquals(IntStream.rangeClosed(1, 10).boxed().toList(), result);
+            assertEquals(1, f.join());
+            return null;
+        });
+    }
+
+    @Test
+    void alsoTapTo_shouldNotCloseTheFlowWhenTheOtherSinkCloses() throws Exception {
+        Scopes.supervised(scope -> {
+            // given
+            var other = new Channel<Integer>();
+            var f = scope.fork(() -> {
+                var v = other.receiveOrClosed();
+                other.done();
+                return v;
+            });
+
+            // when
+            List<Integer> result = Flows
+                    .iterate(1, i -> i + 1)
+                    .take(10)
+                    .tap(v -> {
+                        try {
+                            Thread.sleep(10);
+                        } catch (InterruptedException e) {
+                            throw new RuntimeException(e);
+                        }
+                    })
+                    .alsoToTap(other)
+                    .runToList();
+
+            // then
+            assertEquals(IntStream.rangeClosed(1, 10).boxed().toList(), result);
+            assertEquals(1, f.join());
+            return null;
+        });
+    }
+}