/**
* Adds an element to the start of the array.
*
* @param elem element to add
* @return self reference for convenience
*/
public ArrayBuilder prepend(final Value elem) {
if (inLeft < Array.MAX_DIGIT) {
// just insert the element
vals[(mid - inLeft + CAP - 1) % CAP] = elem;
inLeft++;
} else if (tree.isEmpty() && inRight < Array.MAX_DIGIT) {
// move the middle to the left
mid = (mid + CAP - 1) % CAP;
vals[(mid - inLeft + CAP) % CAP] = elem;
inRight++;
} else {
// push leaf node into the tree
final Value[] leaf = new Value[NODE_SIZE];
final int start = (mid - NODE_SIZE + CAP) % CAP;
for (int i = 0; i < NODE_SIZE; i++) leaf[i] = vals[(start + i) % CAP];
tree.prepend(new LeafNode(leaf));
// move rest of the nodes to the right
final int rest = inLeft - NODE_SIZE;
final int p0 = (mid - inLeft + CAP) % CAP;
for (int i = 0; i < rest; i++) {
final int from = (p0 + i) % CAP, to = (from + NODE_SIZE) % CAP;
vals[to] = vals[from];
}
// insert the element
vals[(mid - rest + CAP - 1) % CAP] = elem;
inLeft = rest + 1;
}
return this;
}
