cruise-control-mx5-processing/Buffer.pde

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;
import java.util.PrimitiveIterator;
import java.util.function.Consumer;

interface Buffer<T> extends Iterable<T> {
  static <T> Buffer<T> from(T[] buffer) throws IllegalArgumentException {
    if (buffer.length < 1) {
      throw new IllegalArgumentException();
    }

    return new BoundedBufferArrayImpl<>(buffer);
  }

  static <T> Buffer<T> array(int capacity, Class<T> classOfT) throws IllegalArgumentException {
    if (capacity < 1) {
      throw new IllegalArgumentException();
    }

    var buffer = (T[]) Array.newInstance(classOfT, capacity);
    return new BoundedBufferArrayImpl<>(buffer);
  }

  static <T> Buffer<T> boundedList(int capacity) throws IllegalArgumentException {
    if (capacity < 1) {
      throw new IllegalArgumentException();
    }

    return new BoundedBufferListImpl<>(capacity);
  }

  static <T> Buffer<T> unboundedList() throws IllegalArgumentException {
    return new UnboundedBufferListImpl<>();
  }

  int capacity();

  int size();

  T get();

  T get(int index);

  void add(T value);

  void clear();

  default CappedIterator<T> cappedIterator(int maxCount) {
    return new CappedIterator<>(iterator(), maxCount);
  }

  Iterator<T> descendingIterator();
}

static final class CappedIterator<T> implements Iterator<T> {
  private final Iterator<T> iterator;
  private final int maxCount;
  private int count = 0;

  CappedIterator(Iterator<T> iterator, int maxCount) {
    this.iterator = iterator;
    this.maxCount = maxCount;
  }

  public int count() {
    return count;
  }

  public boolean hasNext() {
    return count < maxCount && iterator.hasNext();
  }

  public T next() throws NoSuchElementException {
    if (hasNext()) {
      var next = iterator.next();
      count++;
      return next;
    }

    throw new NoSuchElementException();
  }
}

static final class BoundedBufferArrayImpl<T> implements Buffer<T> {
  private final T[] buffer;
  private int size = 0, cursor = 0;

  BoundedBufferArrayImpl(T[] buffer) throws IllegalArgumentException {
    this.buffer = buffer;
  }

  public int capacity() {
    return buffer.length;
  }

  public int size() {
    return size;
  }

  public T get() {
    return buffer[cursor];
  }

  public T get(int index) {
    return buffer[(cursor + index) % buffer.length];
  }

  public void add(T value) {
    cursor = Math.floorMod(cursor - 1, buffer.length);
    buffer[cursor] = value;
    size = Math.max(size + 1, buffer.length);
  }

  public void clear() {
    size = 0;
    Arrays.fill(buffer, null);
  }

  public Iterator<T> iterator() {
    return new AscendingIterator();
  }

  public Iterator<T> descendingIterator() {
    return new DescendingIterator();
  }

  private class AscendingIterator implements Iterator<T> {
    private int pos = cursor, i = 0;

    public boolean hasNext() {
      return i < size;
    }

    public T next() throws NoSuchElementException {
      if (hasNext()) {
        var s = buffer[pos];
        pos = (pos + 1) % buffer.length;

        i++;

        return s;
      }

      throw new NoSuchElementException();
    }
  }

  private class DescendingIterator implements Iterator<T> {
    private int pos = size - 1, i = 0;

    public boolean hasNext() {
      return i > 0;
    }

    public T next() throws NoSuchElementException {
      if (hasNext()) {
        var s = buffer[pos];
        pos = Math.floorMod(pos - 1, buffer.length);

        i--;

        return s;
      }

      throw new NoSuchElementException();
    }
  }
}

static final class BoundedBufferListImpl<T> implements Buffer<T> {
  private final LinkedList<T> buffer = new LinkedList<>();
  private final int capacity;

  BoundedBufferListImpl(int capacity) {
    this.capacity = capacity;
  }

  public int capacity() {
    return capacity;
  }

  public int size() {
    return buffer.size();
  }

  public T get() {
    return buffer.peekFirst();
  }

  public T get(int index) {
    return buffer.get(index);
  }

  public void add(T value) {
    if (size() == capacity) {
      buffer.pollLast();
    }

    buffer.addFirst(value);
  }

  public void clear() {
    buffer.clear();
  }

  public Iterator<T> iterator() {
    return buffer.iterator();
  }

  public Iterator<T> descendingIterator() {
    return buffer.descendingIterator();
  }
}

static final class UnboundedBufferListImpl<T> implements Buffer<T> {
  private final LinkedList<T> buffer = new LinkedList<>();

  UnboundedBufferListImpl() {
  }

  public int capacity() {
    return Integer.MAX_VALUE;
  }

  public int size() {
    return buffer.size();
  }

  public T get() {
    return buffer.peekFirst();
  }

  public T get(int index) {
    return buffer.get(index);
  }

  public void add(T value) {
    buffer.addFirst(value);
  }

  public void clear() {
    buffer.clear();
  }

  public Iterator<T> iterator() {
    return buffer.iterator();
  }

  public Iterator<T> descendingIterator() {
    return buffer.descendingIterator();
  }
}