From 0a3946e579a0c358a13aa1621fecc3e220cd6e38 Mon Sep 17 00:00:00 2001
From: Ben Culkin <scorpress@gmail.com>
Date: Wed, 25 Oct 2023 19:33:02 -0400
Subject: Tweaks

---
 src/main/java/bjc/data/FlatMapIterator.java |  52 +++++++++++
 src/main/java/bjc/functypes/MapBuilder.java | 132 ++++++++++++++++++++++++++++
 2 files changed, 184 insertions(+)
 create mode 100644 src/main/java/bjc/data/FlatMapIterator.java
 create mode 100644 src/main/java/bjc/functypes/MapBuilder.java

diff --git a/src/main/java/bjc/data/FlatMapIterator.java b/src/main/java/bjc/data/FlatMapIterator.java
new file mode 100644
index 0000000..47bc06c
--- /dev/null
+++ b/src/main/java/bjc/data/FlatMapIterator.java
@@ -0,0 +1,52 @@
+package bjc.data;
+
+import java.util.*;
+import java.util.function.Function;
+
+/**
+ * Create an iterator that applies a flat-map function
+ * 
+ * @author bjcul
+ * 
+ * @param <T1> The source type
+ * @param <T2> The output type
+ *
+ */
+public class FlatMapIterator<T1, T2> implements Iterator<T2> {
+	private Function<T1, Iterator<T2>> action;
+
+	private Iterator<T1> source;
+	private Iterator<T2> output;
+	/**
+	 * Create a new flat-map iterator
+	 * 
+	 * @param source The source iterator
+	 * @param action The action to apply to the iterator
+	 */
+	public FlatMapIterator(Iterator<T1> source, Function<T1, Iterator<T2>> action) {
+		this.source = source;
+		this.action = action;
+		
+	}
+	
+	@Override
+	public boolean hasNext() {
+		if (output != null && output.hasNext()) return true;
+		while (source.hasNext()) {
+			output = action.apply(source.next());
+			if (output.hasNext()) return true;
+		}
+		return false;
+	}
+
+	@Override
+	public T2 next() {
+		if (output != null && output.hasNext()) return output.next();
+		while (source.hasNext()) {
+			output = action.apply(source.next());
+			if (output.hasNext()) return output.next();
+		}
+		throw new NoSuchElementException();
+	}
+
+}
diff --git a/src/main/java/bjc/functypes/MapBuilder.java b/src/main/java/bjc/functypes/MapBuilder.java
new file mode 100644
index 0000000..1fa98e2
--- /dev/null
+++ b/src/main/java/bjc/functypes/MapBuilder.java
@@ -0,0 +1,132 @@
+package bjc.functypes;
+
+import java.util.*;
+import java.util.function.Function;
+
+import bjc.funcdata.Freezable;
+import bjc.funcdata.ObjectFrozen;
+
+/**
+ * Functional interface for a generic builder using a map
+ * 
+ * @author bjcul
+ *
+ * @param <K> Key type of the map
+ * @param <V> Value type of the map
+ * @param <R> Result type of the builder
+ */
+public interface MapBuilder<K, V, R> extends Freezable<MapBuilder<K, V, R>> {
+	/**
+	 * Build an instance using the current map
+	 * 
+	 * @return An instance constructed using the map
+	 */
+	R build();
+	
+	/**
+	 * Add a value to the map
+	 * 
+	 * @param key The key to add
+	 * @param value The value to add
+	 * 
+	 * @return The builder, for chaining
+	 */
+	MapBuilder<K, V, R> add(K key, V value);
+	
+	/**
+	 * Remove a value from the map
+	 * 
+	 * @param key The key to remove
+	 * 
+	 * @return The removed value
+	 */
+	V remove(K key);
+	
+	/**
+	 * Clear the contents of the map
+	 */
+	void clear();
+	
+	/**
+	 * Get the internal map.
+	 * 
+	 * @return The internal map
+	 */
+	Map<K, V> getMap();
+	
+	/**
+	 * Create a new map-builder from a function
+	 * 
+	 * @param <K> The key type of the map
+	 * @param <V> The value type of the map
+	 * @param <R> The result of the builder
+	 * 
+	 * @param f The building function
+	 * 
+	 * @return A map-builder using the function
+	 */
+	static <K, V, R> MapBuilder<K, V, R> from(Function<Map<K, V>, R> f) {
+		return new FunctionalMapBuilder<>(f);
+	}
+}
+
+final class FunctionalMapBuilder<K, V, R> implements MapBuilder<K, V, R> {
+	private final Function<Map<K, V>, R> f;
+	private Map<K, V> mep = new HashMap<>();
+
+	private boolean frozen = false;
+	
+	FunctionalMapBuilder(Function<Map<K, V>, R> f) {
+		this.f = f;
+	}
+
+	@Override
+	public R build() {
+		return f.apply(mep);
+	}
+
+	@Override
+	public MapBuilder<K, V, R> add(K key, V value) {
+		if (frozen) throw new ObjectFrozen();
+		
+		mep.put(key, value);
+		return this;
+	}
+
+	@Override
+	public V remove(K key) {
+		if (frozen) throw new ObjectFrozen();
+		
+		return mep.remove(key);
+	}
+
+	@Override
+	public void clear() {
+		if (frozen) throw new ObjectFrozen();
+		
+		mep.clear();
+	}
+
+	@Override
+	public Map<K, V> getMap() {
+		if (frozen) return Collections.unmodifiableMap(mep);
+		return mep;
+	}
+
+	@Override
+	public boolean freeze() {
+		frozen = true;
+		return true;
+	}
+
+	@Override
+	public boolean thaw() {
+		frozen = false;
+		return true;
+	}
+
+	@Override
+	public boolean isFrozen() {
+		return frozen;
+	}
+}
\ No newline at end of file
-- 
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