1 files changed, 106 insertions, 0 deletions
diff --git a/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
new file mode 100644
index 0000000..e9246c3
--- /dev/null
+++ b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
@@ -0,0 +1,106 @@
+package org.zwobble.mammoth.internal.util;
+
+import java.util.Iterator;
+import java.util.Optional;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class Iterables {
+    public static <T> Optional<T> tryFind(Iterable<T> iterable, Predicate<T> predicate) {
+        for (T element : iterable) {
+            if (predicate.test(element)) {
+                return Optional.of(element);
+            }
+        }
+        return Optional.empty();
+    }
+
+    public static <T, R> Iterable<R> lazyMap(Iterable<T> iterable, Function<T, R> function) {
+        return new Iterable<R>() {
+            @Override
+            public Iterator<R> iterator() {
+                return map(iterable.iterator(), function);
+            }
+        };
+    }
+
+    public static <T> T getFirst(Iterable<? extends T> iterable, T defaultValue) {
+        Iterator<? extends T> iterator = iterable.iterator();
+        if (iterator.hasNext()) {
+            return iterator.next();
+        } else {
+            return defaultValue;
+        }
+    }
+
+    public static <T, R> Iterable<R> lazyFlatMap(Iterable<T> iterable, Function<T, Iterable<R>> function) {
+        return lazyFlatten(lazyMap(iterable, function));
+    }
+
+    public static <T> Iterable<T> lazyConcat(Iterable<T> iterable1, Iterable<T> iterable2) {
+        return new Iterable<T>() {
+            @Override
+            public Iterator<T> iterator() {
+                return Stream.concat(stream(iterable1), stream(iterable2)).iterator();
+            }
+        };
+    }
+
+    public static <T> Iterable<T> lazyFlatten(Iterable<? extends Iterable<T>> iterables) {
+        return new Iterable<T>() {
+            @Override
+            public Iterator<T> iterator() {
+                return stream(iterables)
+                    .flatMap(iterable -> stream(iterable))
+                    .iterator();
+            }
+        };
+    }
+
+    public static <T> Iterable<T> lazyFilter(Iterable<T> iterables, Predicate<T> predicate) {
+        return new Iterable<T>() {
+            @Override
+            public Iterator<T> iterator() {
+                return stream(iterables)
+                    .filter(predicate)
+                    .iterator();
+            }
+        };
+    }
+
+    public static <T, R> Iterable<R> lazyFilter(Iterable<T> iterables, Class<R> clazz) {
+        return new Iterable<R>() {
+            @Override
+            @SuppressWarnings("unchecked")
+            public Iterator<R> iterator() {
+                return (Iterator<R>) stream(iterables)
+                    .filter(clazz::isInstance)
+                    .iterator();
+            }
+        };
+    }
+
+    private static <T, R> Iterator<R> map(Iterator<T> iterator, Function<T, R> function) {
+        return new Iterator<R>() {
+            @Override
+            public boolean hasNext() {
+                return iterator.hasNext();
+            }
+
+            @Override
+            public R next() {
+                return function.apply(iterator.next());
+            }
+        };
+    }
+
+    public static <T> boolean any(Iterable<T> iterable, Predicate<T> predicate) {
+        return stream(iterable).anyMatch(predicate);
+    }
+
+    public static <T> Stream<T> stream(Iterable<T> iterable) {
+        return StreamSupport.stream(iterable.spliterator(), false);
+    }
+}