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General structure to easily create dynamic logic via MethodHandles and others.
package org.fiolino.common.container;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.Supplier;
/**
* Contains various values based on some Schema.
*/
public class Container implements ReadOnlyContainer {
private static final Container EMPTY = new Schema("").createContainer();
private final Schema owner;
private Object[] values;
Container(Schema owner, int size) {
this.owner = owner;
values = new Object[size];
}
public static Container empty() {
return EMPTY;
}
private final class Startup implements ReadOnlyContainer {
@Override
public E get(Selector selector) {
TemporaryFunction cycleDetector = new TemporaryFunction();
return cycleDetector.get(selector);
}
}
private static final ReadOnlyContainer ALL_NULL = new ReadOnlyContainer() {
@Override
public E get(Selector selector) {
return null;
}
};
private final ReadOnlyContainer startup = new Startup();
private final class TemporaryFunction implements ReadOnlyContainer {
private final Set> used = new HashSet<>();
@Override
public E get(Selector selector) {
if (!used.add(selector)) {
throw new IllegalStateException("Cyclic aliases detected!");
}
return Container.this.get(selector, this);
}
}
@Override
public E get(Selector selector) {
return get(selector, startup);
}
public E getDirectOnly(Selector selector) {
return get(selector, ALL_NULL);
}
Object getDirectly(Selector selector) {
int pos = owner.getIndex(selector);
if (!withinRange(pos))
return null;
return values[pos];
}
private E get(Selector selector, ReadOnlyContainer caller) {
Object val = getDirectly(selector);
return selector.castOrDefault(val, caller);
}
public E getOrCreate(Selector selector, Supplier factory) {
int pos = owner.getIndex(selector);
Object val;
if (!checkLength(pos) || (val = values[pos]) == null) {
E newVal = factory.get();
if (newVal == null) {
throw new NullPointerException("Factory " + factory + " returned null!");
}
selector.checkWriteAccess(null);
values[pos] = newVal;
return newVal;
}
return selector.cast(val);
}
public void set(Selector selector, E value) {
if (value == null) {
return;
}
int pos = owner.getIndex(selector);
checkLength(pos);
selector.checkWriteAccess(() -> values[pos]);
values[pos] = value;
}
/**
* Sets the value if it was not set before.
*
* @return The existing valuem, which will be null if not set before
*/
public E putIfAbsent(Selector selector, E value) {
int pos = owner.getIndex(selector);
Object previous = checkLength(pos) ? values[pos] : null;
if (previous == null) {
selector.checkWriteAccess(() -> null);
values[pos] = value;
return null;
}
return selector.cast(previous);
}
/**
* Gets the value, or the default value,
* Does not take aliases and such into account.
*/
public E getOrDefault(Selector selector, E value) {
E result = getDirectOnly(selector);
return result == null ? value : result;
}
private boolean withinRange(int pos) {
return pos < values.length;
}
private boolean checkLength(int pos) {
if (!withinRange(pos)) {
values = Arrays.copyOf(values, pos + 1);
return false;
}
return true;
}
public E getAndSet(Selector selector, E value) {
int pos = owner.getIndex(selector);
checkLength(pos);
E previous = selector.castOrDefault(values[pos], startup);
//selector.checkWriteAccess(previous);
values[pos] = value;
return previous;
}
public E remove(Selector selector) {
int pos = owner.getIndex(selector);
if (pos < values.length) {
selector.checkWriteAccess(() -> values[pos]);
E previous = selector.cast(values[pos]);
values[pos] = null;
return previous;
}
return null;
}
/**
* If there is a value assigned, then execute the Consumer and return true.
* Otherwise simply return false.
*/
public boolean ifValid(Selector selector, Consumer action) {
E val = get(selector);
if (val != null) {
action.accept(val);
return true;
}
return false;
}
/**
* If there is a value assigned, then return the result of the Predicate.
* Otherwise simply return false.
*/
public boolean ifValidAnd(Selector selector, Predicate action) {
E val = get(selector);
return val != null && action.test(val);
}
@Override
public boolean equals(Object obj) {
return obj == this ||
obj != null && obj.getClass().equals(getClass()) &&
((Container) obj).owner.equals(owner) && Arrays.equals(((Container) obj).values, values);
}
@Override
public int hashCode() {
return owner.hashCode() * 31 + Arrays.hashCode(values);
}
@Override
public String toString() {
return "Container of " + owner;
}
public Container createSubContainer() {
return new SubContainer(this);
}
private static final class SubContainer extends Container {
private final Container parent;
SubContainer(Container parent) {
super(parent.owner, parent.values.length);
this.parent = parent;
}
@Override
Object getDirectly(Selector selector) {
Object val = super.getDirectly(selector);
return val == null ? selector.getDirectlyFromParent(parent) : val;
}
@Override
public E getDirectOnly(Selector selector) {
Object value = super.getDirectly(selector);
return value == null ? null : selector.cast(value);
}
@Override
public boolean equals(Object obj) {
return super.equals(obj) && parent.equals(((SubContainer) obj).parent);
}
@Override
public int hashCode() {
return parent.hashCode() * 31 + super.hashCode();
}
@Override
public String toString() {
return super.toString() + " --- in parent " + parent.toString();
}
}
}