From 843329de434bb334d90927c4d22345373a388530 Mon Sep 17 00:00:00 2001
From: bculkin2442 <bjculkin@mix.wvu.edu>
Date: Tue, 2 Jul 2019 18:05:22 -0400
Subject: Rename package root

The package root is now bjc, not io.github.bculkin2442.
---
 src/main/java/bjc/esodata/PushdownMap.java | 158 +++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)
 create mode 100644 src/main/java/bjc/esodata/PushdownMap.java

(limited to 'src/main/java/bjc/esodata/PushdownMap.java')

diff --git a/src/main/java/bjc/esodata/PushdownMap.java b/src/main/java/bjc/esodata/PushdownMap.java
new file mode 100644
index 0000000..5db5f05
--- /dev/null
+++ b/src/main/java/bjc/esodata/PushdownMap.java
@@ -0,0 +1,158 @@
+package bjc.esodata;
+
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import bjc.funcdata.FunctionalMap;
+import bjc.funcdata.IList;
+import bjc.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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