Double-sided tapes and tape changers

1 files changed, 108 insertions, 69 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/esodata/Tape.java b/BJC-Utils2/src/main/java/bjc/utils/esodata/Tape.java
index 9d50b63..d08feb1 100644
--- a/BJC-Utils2/src/main/java/bjc/utils/esodata/Tape.java
+++ b/BJC-Utils2/src/main/java/bjc/utils/esodata/Tape.java
@@ -2,73 +2,112 @@ package bjc.utils.esodata;
 
 import java.util.ArrayList;
 
-public class Tape<T> {
-	private ArrayList<T> backing;
-	private int pos;
-
-	public Tape() {
-		backing = new ArrayList<>();
-	}
-
-	public T item() {
-		return backing.get(pos);
-	}
-
-	public int size() {
-		return backing.size();
-	}
-
-	public void item(T itm) {
-		backing.set(pos, itm);
-	}
-
-	public void append(T itm) {
-		backing.add(itm);
-	}
-
-	// Add an item before the current
-	public void insert(T itm) {
-		backing.add(pos, itm);
-	}
-
-	public T remove() {
-		if(pos != 0) pos -= 1;
-		return backing.remove(pos);
-	}
-
-	public void first() {
-		pos = 0;
-	}
-
-	public void last() {
-		pos = backing.size() - 1;
-	}
-
-	public boolean left() {
-		if(pos == 0) return false;
-		
-		pos -= 1;
-		return true;
-	}
-
-	public boolean left(int amt) {
-		if((pos - amt) < 0) return false;
-
-		pos -= amt;
-		return true;
-	}
-
-	public boolean right() {
-		if(pos == (backing.size() - 1)) return false;
-
-		pos += 1;
-		return true;
-	}
-
-	public boolean right(int amt) {
-		if((pos + amt) >= (backing.size() - 1)) return false;
-
-		pos += amt;
-		return true;
-	}
+/**
+ * Interface for something that acts like a tape.
+ *
+ * A tape is essentially a 1D array with a cursor attached to it, and you can only
+ * affect elements at that cursor. The size of the array is theoretically unbounded
+ * to the right, but in practice bounded by available memory.
+ *
+ * @param T The element type of the tape.
+ * @author bjculkin
+ */
+public interface Tape<T> {
+	/**
+	 * Get the item the tape is currently on.
+	 *
+	 * @return The item the tape is on.
+	 */
+	T item();
+
+	/**
+	 * Set the item the tape is currently on.
+	 *
+	 * @param itm The new value for the tape item.
+	 */
+	void item(T itm);
+
+	/**
+	 * Get the current number of elements in the tape.
+	 *
+	 * @return The current number of elements in the tape.
+	 */
+	int size();
+
+	/**
+	 * Insert an element before the current item.
+	 *
+	 * @param itm The item to add.
+	 */
+	void insertBefore(T itm);
+
+	/**
+	 * Insert an element after the current item.
+	 */
+	void insertAfter(T itm);
+
+	/**
+	 * Remove the current element.
+	 * 
+	 * Also moves the cursor back one step if possible to maintain
+	 * relative position.
+	 *
+	 * @return The removed item.
+	 */
+	T remove();
+
+	/**
+	 * Move the cursor to the left-most position.
+	 */
+	void first();
+
+	/**
+	 * Move the cursor the right-most position.
+	 */
+	void last();
+
+	/**
+	 * Move the cursor one space left.
+	 *
+	 * The cursor can't go past zero.
+	 *
+	 * @return True if the cursor was moved left.
+	 */
+	boolean left();
+
+	/**
+	 * Move the cursor the specified amount left.
+	 *
+	 * The cursor can't go past zero.
+	 * Attempts to move the cursor by amounts that would exceed zero
+	 * don't move the cursor at all.
+	 *
+	 * @param amt The amount to attempt to move the cursor left.
+	 *
+	 * @return True if the cursor was moved left.
+	 */
+	boolean left(int amt);
+
+	/**
+	 * Move the cursor one space right.
+	 *
+	 * @return Whether the cursor was moved right.
+	 */
+	boolean right();
+
+	/**
+	 * Move the cursor the specified amount right.
+	 *
+	 * @param amt The amount to move the cursor right by.
+	 *
+	 * @return Whether the cursor was moved right.
+	 */
+	boolean right(int amt);
+
+	/**
+	 * Is this tape double sided?
+	 *
+	 * @return Whether or not this tape is double-sided.
+	 */
+	boolean isDoubleSided();
 }