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package bjc.utils.esodata;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import bjc.utils.funcdata.FunctionalMap;
import bjc.utils.funcdata.IList;
import bjc.utils.funcdata.IMap;
/**
* A variant of a map where inserting a duplicate key shadows the existing value
* instead of replacing it.
*
* This could be useful for things like variable scopes.
*
* @author EVE
*
* @param <KeyType>
* The key of the map.
*
* @param <ValueType>
* The values in the map.
*/
public class PushdownMap<KeyType, ValueType> implements IMap<KeyType, ValueType> {
/* Our backing storage. */
private final IMap<KeyType, Stack<ValueType>> backing;
/** Create a new empty stack-based map. */
public PushdownMap() {
backing = new FunctionalMap<>();
}
/** Create a new empty stack-based map using the specified backing. */
private PushdownMap(final IMap<KeyType, Stack<ValueType>> back) {
backing = back;
}
@Override
public void clear() {
backing.clear();
}
@Override
public boolean containsKey(final KeyType key) {
return backing.containsKey(key);
}
@Override
public IMap<KeyType, ValueType> extend() {
return new PushdownMap<>(backing.extend());
}
@Override
public void forEach(final BiConsumer<KeyType, ValueType> action) {
backing.forEach((key, stk) -> action.accept(key, stk.top()));
}
@Override
public void forEachKey(final Consumer<KeyType> action) {
backing.forEachKey(action);
}
@Override
public void forEachValue(final Consumer<ValueType> action) {
backing.forEachValue(stk -> action.accept(stk.top()));
}
@Override
public ValueType get(final KeyType key) {
return backing.get(key).top();
}
@Override
public int size() {
return backing.size();
}
@Override
public IList<KeyType> keyList() {
return backing.keyList();
}
@Override
public <V2> IMap<KeyType, V2> transform(final Function<ValueType, V2> transformer) {
/*
* @NOTE Can and should we support this? More to the point,
* maybe this should be a map sub-type that does what it needs
* to?
*/
throw new UnsupportedOperationException("Cannot transform pushdown maps.");
}
@Override
public ValueType put(final KeyType key, final ValueType val) {
if(backing.containsKey(key)) {
final Stack<ValueType> stk = backing.get(key);
final ValueType vl = stk.top();
stk.push(val);
return vl;
}
final Stack<ValueType> stk = new SimpleStack<>();
stk.push(val);
return null;
}
@Override
public ValueType remove(final KeyType key) {
final Stack<ValueType> stk = backing.get(key);
if(stk.size() > 1) {
return stk.pop();
}
return backing.remove(key).top();
}
@Override
public IList<ValueType> valueList() {
return backing.valueList().map(Stack::top);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (backing == null ? 0 : backing.hashCode());
return result;
}
@Override
public boolean equals(final Object obj) {
if(this == obj) return true;
if(obj == null) return false;
if(!(obj instanceof PushdownMap<?, ?>)) return false;
final PushdownMap<?, ?> other = (PushdownMap<?, ?>) obj;
if(backing == null) {
if(other.backing != null) return false;
} else if(!backing.equals(other.backing)) return false;
return true;
}
@Override
public String toString() {
return String.format("PushdownMap [backing=%s]", backing);
}
}
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