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/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.esodata;
import java.util.*;
import java.util.function.*;
import bjc.data.*;
import bjc.funcdata.*;
/**
* 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 MapEx<KeyType, ValueType> {
/* Our backing storage. */
private final MapEx<KeyType, Stack<ValueType>> backing;
private boolean isFrozen = false;
private boolean thawEnabled = true;
/** Create a new empty stack-based map. */
public PushdownMap() {
backing = new FunctionalMap<>();
}
@Override
public void clear() {
if (isFrozen) throw new ObjectFrozen("Can't clear frozen map");
backing.clear();
}
@Override
public boolean containsKey(final KeyType key) {
return backing.containsKey(key);
}
@Override
public void forEach(final BiConsumer<KeyType, ValueType> action) {
backing.forEach((key, stk) -> action.accept(key, stk.top()));
}
@Override
public Optional<ValueType> get(final KeyType key) {
return backing.get(key).map((stack) -> stack.top());
}
@Override
public int size() {
return backing.size();
}
@Override
public ListEx<KeyType> keyList() {
return backing.keyList();
}
@Override
public ValueType put(final KeyType key, final ValueType val) {
if (isFrozen) throw new ObjectFrozen("Can't insert key " + key + " into frozen map");
if (backing.containsKey(key)) {
final Stack<ValueType> stk = backing.get(key).get();
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) {
if (isFrozen) throw new ObjectFrozen("Can't remove key " + key + " from frozen map");
Holder<ValueType> result = Holder.of(null);
backing.get(key).ifPresent((stk) -> {
if (stk.size() > 1) {
result.replace(stk.pop());
} else {
result.replace(backing.remove(key).top());
}
});
return result.getValue();
}
@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);
}
@Override
public boolean freeze() {
isFrozen = true;
return true;
}
@Override
public boolean thaw() {
if (thawEnabled) {
isFrozen = false;
return true;
} else {
return false;
}
}
@Override
public boolean deepFreeze() {
thawEnabled = true;
return freeze();
}
@Override
public boolean canFreeze() {
return true;
}
@Override
public boolean canThaw() {
return thawEnabled;
}
@Override
public boolean isFrozen() {
return isFrozen;
}
}
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