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119 changes: 119 additions & 0 deletions
119
src/main/java/org/neo4j/gis/spatial/pipes/impl/AbstractPipe.java
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|---|---|---|
| @@ -0,0 +1,119 @@ | ||
| package org.neo4j.gis.spatial.pipes.impl; | ||
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| import java.util.ArrayList; | ||
| import java.util.Iterator; | ||
| import java.util.List; | ||
| import java.util.NoSuchElementException; | ||
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| /** | ||
| * An AbstractPipe provides most of the functionality that is repeated in every instance of a Pipe. | ||
| * Any subclass of AbstractPipe should simply implement processNextStart(). The standard model is | ||
| * <pre> | ||
| * protected E processNextStart() throws NoSuchElementException { | ||
| * S s = this.starts.next(); | ||
| * E e = // do something with the S to yield an E | ||
| * return e; | ||
| * } | ||
| * </pre> | ||
| * If the current incoming S is not to be emitted and there are no other S objects to process and emit, then throw a NoSuchElementException. | ||
| * | ||
| * @author Marko A. Rodriguez (http://markorodriguez.com) | ||
| */ | ||
| public abstract class AbstractPipe<S, E> implements Pipe<S, E> { | ||
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| protected Iterator<S> starts; | ||
| private E nextEnd; | ||
| protected E currentEnd; | ||
| private boolean available = false; | ||
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| public void setStarts(final Pipe<?, S> starts) { | ||
| this.starts = starts; | ||
| } | ||
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| public void setStarts(final Iterator<S> starts) { | ||
| if (starts instanceof Pipe) | ||
| this.starts = starts; | ||
| else | ||
| this.starts = new LastElementIterator<S>(starts); | ||
| } | ||
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| public void setStarts(final Iterable<S> starts) { | ||
| this.setStarts(starts.iterator()); | ||
| } | ||
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| public void reset() { | ||
| if (this.starts instanceof Pipe) { | ||
| ((Pipe) this.starts).reset(); | ||
| } | ||
| this.nextEnd = null; | ||
| this.currentEnd = null; | ||
| this.available = false; | ||
| } | ||
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| public List getPath() { | ||
| final List pathElements = getPathToHere(); | ||
| final int size = pathElements.size(); | ||
| // do not repeat filters as they dup the object | ||
| if (size == 0 || pathElements.get(size - 1) != this.currentEnd) { | ||
| pathElements.add(this.currentEnd); | ||
| } | ||
| return pathElements; | ||
| } | ||
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| public void remove() { | ||
| throw new UnsupportedOperationException(); | ||
| } | ||
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| public E next() { | ||
| if (this.available) { | ||
| this.available = false; | ||
| return (this.currentEnd = this.nextEnd); | ||
| } else { | ||
| return (this.currentEnd = this.processNextStart()); | ||
| } | ||
| } | ||
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| public boolean hasNext() { | ||
| if (this.available) | ||
| return true; | ||
| else { | ||
| try { | ||
| this.nextEnd = this.processNextStart(); | ||
| return (this.available = true); | ||
| } catch (final NoSuchElementException e) { | ||
| return (this.available = false); | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * The iterator method of Iterable is not faithful to the Java semantics of iterator(). | ||
| * This method simply returns the pipe itself (which is an iterator) and thus, is useful only for foreach iteration. | ||
| * | ||
| * @return the pipe from the perspective of an iterator | ||
| */ | ||
| public Iterator<E> iterator() { | ||
| return this; | ||
| } | ||
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| public String toString() { | ||
| return getClass().getSimpleName(); | ||
| } | ||
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| protected abstract E processNextStart() throws NoSuchElementException; | ||
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| protected List getPathToHere() { | ||
| if (this.starts instanceof Pipe) { | ||
| return ((Pipe) this.starts).getPath(); | ||
| } else if (this.starts instanceof LastElementIterator) { | ||
| final List list = new ArrayList(); | ||
| list.add(((LastElementIterator) starts).lastElement()); | ||
| return list; | ||
| } else { | ||
| return new ArrayList(); | ||
| } | ||
| } | ||
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| } | ||
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