Add fool-proofed duration check

core/src/main/java/com/github/skjolber/packing/deadline/PackagerInterruptSupplierBuilder.java

@@ -7,7 +7,8 @@
 
 public class PackagerInterruptSupplierBuilder {
 
-	public static final NegativePackagerInterruptSupplier NOOP = new NegativePackagerInterruptSupplier();
+	public static final NegativePackagerInterruptSupplier NEGATIVE = new NegativePackagerInterruptSupplier();
+	public static final PositivePackagerInterruptSupplier POSITIVE = new PositivePackagerInterruptSupplier();
 
 	private long deadline = Long.MAX_VALUE;
 	private BooleanSupplier interrupt = null;
@@ -33,27 +34,33 @@ public PackagerInterruptSupplierBuilder withScheduledThreadPoolExecutor(Schedule
 	}
 
 	public PackagerInterruptSupplier build() {
+
 		if(deadline == Long.MAX_VALUE || deadline == -1L) {
 			// no deadline
 			if(interrupt != null) {
 				return new DefaultPackagerInterrupt(interrupt);
 			}
-			return NOOP;
+			return NEGATIVE;
 		}
-
+
+		long delay = deadline - System.currentTimeMillis();
+		if(delay <= 0) {
+			return POSITIVE; // i.e. time is already up
+		}
+
 		if(scheduledThreadPoolExecutor == null) {
 			throw new IllegalStateException("Expected scheduler");
 		}
-
+				
 		if(interrupt == null) {
 			DeadlineCheckPackagerInterruptSupplier supplier = new DeadlineCheckPackagerInterruptSupplier();
-			ScheduledFuture<?> schedule = scheduledThreadPoolExecutor.schedule(supplier, deadline - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
+			ScheduledFuture<?> schedule = scheduledThreadPoolExecutor.schedule(supplier, delay, TimeUnit.MILLISECONDS);
 			supplier.setFuture(schedule);
 			return supplier;
 		}
 
 		DelegateDeadlineCheckPackagerInterruptSupplier supplier = new DelegateDeadlineCheckPackagerInterruptSupplier(interrupt);
-		ScheduledFuture<?> schedule = scheduledThreadPoolExecutor.schedule(supplier, deadline - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
+		ScheduledFuture<?> schedule = scheduledThreadPoolExecutor.schedule(supplier, delay, TimeUnit.MILLISECONDS);
 		supplier.setFuture(schedule);
 		return supplier;
 	}

core/src/main/java/com/github/skjolber/packing/deadline/PositivePackagerInterruptSupplier.java

@@ -0,0 +1,10 @@
+package com.github.skjolber.packing.deadline;
+
+public class PositivePackagerInterruptSupplier implements PackagerInterruptSupplier {
+
+	@Override
+	public boolean getAsBoolean() {
+		return true;
+	}
+
+}

core/src/main/java/com/github/skjolber/packing/packer/AbstractPackager.java

@@ -135,7 +135,7 @@ protected P packSingle(List<Integer> containerItemIndexes, PackagerAdapter<P> ad
 	}
 
 	public List<Container> packList(List<StackableItem> products, List<ContainerItem> containers, int limit) {
-		return pack(products, containers, limit, PackagerInterruptSupplierBuilder.NOOP);
+		return pack(products, containers, limit, PackagerInterruptSupplierBuilder.NEGATIVE);
 	}
 
 	/**