import org.openjdk.jmh.annotations.Benchmark;

public class StackWalkerExtraction {

    private static Object call(int depth, Callable<?> result) throws Exception {
        if (depth == 0) {
            return result.call();
        } else {
            return call(depth - 1, result);
        }
    }

    @Benchmark
    public Object snapshot() throws Exception {
        return call(100, () -> StackWalker.getInstance().walk(new InstanaWalker(35, 0)));
    }

    @Benchmark
    public Object complete() throws Exception {
        return call(100, () -> StackWalker.getInstance().walk(new InstanaWalker(35, 0)));
    }

    private class RawWalker implements Function<Stream<StackWalker.StackFrame>, StackWalker.StackFrame[]> {

        private final int stackDepth, startFrame;

        RawWalker(int stackDepth, int startFrame) {
            this.stackDepth = stackDepth;
            this.startFrame = startFrame;
        }

        @Override
        public StackWalker.StackFrame[] apply(Stream<StackWalker.StackFrame> stackFrameStream) {
            StackWalker.StackFrame[] elements = new StackWalker.StackFrame[stackDepth];
            Iterator<StackWalker.StackFrame> it = stackFrameStream.skip(startFrame).limit(stackDepth).iterator();
            int index = 0;
            while (it.hasNext()) {
                elements[index++] = it.next();
            }
            return elements;
        }
    }


    private class TransformingWalker implements Function<Stream<StackWalker.StackFrame>, StackWalker.StackFrame[]> {

        private final int stackDepth, startFrame;

        TransformingWalker(int stackDepth, int startFrame) {
            this.stackDepth = stackDepth;
            this.startFrame = startFrame;
        }

        @Override
        public StackFrameElement[] apply(Stream<StackWalker.StackFrame> stackFrameStream) {
            StackFrameElement[] elements = new StackWalker.StackFrame[stackDepth];
            Iterator<StackWalker.StackFrame> it = stackFrameStream.skip(startFrame).limit(stackDepth).iterator();
            int index = 0;
            while (it.hasNext()) {
                elements[index++] = it.next().toStackFrameElement();
            }
            return elements;
        }
    }
}