Made it possible to skip a task if a prior task has been skipped.

This is achieved by registering a token value in the MachieneContext of the stepEngine.
When a non-skippable step is encountered the token value is cleared away.

conference-stepengine/src/main/java/org/tweetwallfx/conference/stepengine/steps/ShowTopRated.java

@@ -278,8 +278,14 @@ private Node createSpeakerImage(SpeakerImageProvider speakerImageProvider, Speak
 
     @Override
     public boolean shouldSkip(final MachineContext context) {
-        return votedTalksConverter.apply(context).isEmpty()
+        final boolean skip = votedTalksConverter.apply(context).isEmpty()
                 || null != ((WordleSkin) context.get("WordleSkin")).getNode().lookup(lookupId);
+
+        if (skip) {
+            context.put(SKIP_TOKEN, config.skipTokenValue);
+        }
+
+        return skip;
     }
 
     @Override
@@ -362,6 +368,7 @@ public static class Config extends AbstractConfig {
         public boolean compressedAvatars = true;
         public int compressedAvatarsLimit = 4;
         public boolean showTags = false;
+        public String skipTokenValue = null;
 
         /**
          * Provides the type of the Top Voted display to flip out.

stepengine-api/src/main/java/org/tweetwallfx/stepengine/api/Step.java

@@ -1,7 +1,7 @@
 /*
  * The MIT License (MIT)
  *
- * Copyright (c) 2015-2019 TweetWallFX
+ * Copyright (c) 2015-2023 TweetWallFX
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -35,6 +35,14 @@
  */
 public interface Step {
 
+    /**
+     * The token a {@link Step} may register with {@link MachineContext} to mark it
+     * has been skipped. Steps following a skipped step may take the presence and
+     * value of such a token into account wehn deciding if their step shall be
+     * skipped.
+     */
+    public static final String SKIP_TOKEN = "skip.token";
+
     /**
      * Initiates this {@link Step} prior to being included in the
      * {@link StepEngine}. This method called only after instantiation by the
@@ -147,7 +155,8 @@ interface Factory {
          * {@link DataProvider DataProviders} required by the created
          * {@link Step}
          */
-        default Collection<Class<? extends DataProvider>> getRequiredDataProviders(final StepEngineSettings.StepDefinition stepDefinition) {
+        default Collection<Class<? extends DataProvider>> getRequiredDataProviders(
+                final StepEngineSettings.StepDefinition stepDefinition) {
             return Collections.emptyList();
         }
     }

stepengine-api/src/main/java/org/tweetwallfx/stepengine/api/StepEngine.java

@@ -1,7 +1,7 @@
 /*
  * The MIT License (MIT)
  *
- * Copyright (c) 2016-2022 TweetWallFX
+ * Copyright (c) 2016-2023 TweetWallFX
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -188,7 +188,12 @@ public <T> T get(final String key, final Class<T> clazz) {
         }
 
         public Object put(final String key, final Object value) {
-            return properties.put(key, value);
+            Objects.requireNonNull(key, "key must not be null");
+            if (null == value) {
+                return properties.remove(key);
+            } else {
+                return properties.put(key, value);
+            }
         }
 
         public void proceed() {
@@ -236,6 +241,8 @@ private void process() {
                 step = stepIterator.next();
                 context.restrictAvailableDataProviders(stepIterator.getRequiredDataProviders(step));
             }
+            // found a step not being skipped. so reset the SKIP_TOKEN
+            context.put(Step.SKIP_TOKEN, null);
             final Step stepToExecute = step;
             final Duration duration = step.preferredStepDuration(context);
 

stepengine-steps/src/main/java/org/tweetwallfx/stepengine/steps/PauseStep.java

@@ -1,7 +1,7 @@
 /*
  * The MIT License (MIT)
  *
- * Copyright (c) 2015-2019 TweetWallFX
+ * Copyright (c) 2015-2023 TweetWallFX
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -35,9 +35,11 @@
 public class PauseStep implements Step {
 
     private final Duration pause;
+    private final String skipWhenSkipped;
 
-    private PauseStep(final Duration pause) {
+    private PauseStep(final Duration pause, final String skipWhenSkipped) {
         this.pause = pause;
+        this.skipWhenSkipped = skipWhenSkipped;
     }
 
     @Override
@@ -55,6 +57,13 @@ public boolean requiresPlatformThread() {
         return false;
     }
 
+    @Override
+    public boolean shouldSkip(final MachineContext context) {
+        return null == skipWhenSkipped
+                ? false
+                : skipWhenSkipped.equals(context.get(Step.SKIP_TOKEN));
+    }
+
     /**
      * Implementation of {@link Step.Factory} as Service implementation creating
      * {@link PauseStep}.
@@ -64,7 +73,7 @@ public static final class FactoryImpl implements Step.Factory {
         @Override
         public Step create(final StepEngineSettings.StepDefinition stepDefinition) {
             final Config config = stepDefinition.getConfig(Config.class);
-            return new PauseStep(config.getDuration());
+            return new PauseStep(config.getDuration(), config.getSkipWhenSkipped());
         }
 
         @Override
@@ -77,6 +86,7 @@ public static class Config {
 
         private ChronoUnit unit = ChronoUnit.SECONDS;
         private long amount = 5;
+        private String skipWhenSkipped = null;
 
         public ChronoUnit getUnit() {
             return unit;
@@ -98,12 +108,20 @@ private Duration getDuration() {
             return Duration.of(getAmount(), getUnit());
         }
 
+        public void setSkipWhenSkipped(String skipWhenSkipped) {
+            this.skipWhenSkipped = Objects.requireNonNull(skipWhenSkipped, "skipWhenSkipped must not be null!");
+        }
+
+        public String getSkipWhenSkipped() {
+            return skipWhenSkipped;
+        }
+
         @Override
         public String toString() {
             return createToString(this, map(
                     "amount", getAmount(),
-                    "unit", getUnit()
-            )) + " extends " + super.toString();
+                    "unit", getUnit(),
+                    "skipWhenSkipped", getSkipWhenSkipped()));
         }
     }
 }