[core] Some util classes from Inceptum

src/main/java/io/gitlab/jfronny/commons/OnceSupplier.java

@@ -0,0 +1,32 @@
+package io.gitlab.jfronny.commons;
+
+import java.util.Objects;
+import java.util.function.Supplier;
+
+public final class OnceSupplier<T> implements Supplier<T> {
+    private final T value;
+    private boolean supplied = false;
+
+    public OnceSupplier(T value) {
+        this.value = value;
+    }
+
+    @Override
+    public T get() {
+        if (supplied) throw new IllegalStateException("Attempted to use already used OnceSupplier");
+        supplied = true;
+        return value;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) return true;
+        if (!(obj instanceof OnceSupplier<?> that)) return false;
+        return Objects.equals(this.value, that.value);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(value);
+    }
+}

src/main/java/io/gitlab/jfronny/commons/StreamIterable.java

@@ -0,0 +1,25 @@
+package io.gitlab.jfronny.commons;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Iterator;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+public record StreamIterable<T>(Supplier<Stream<T>> source) implements Iterable<T> {
+    public StreamIterable(Stream<T> source) {
+        this(new OnceSupplier<>(source));
+    }
+
+    @NotNull
+    @Override
+    public Iterator<T> iterator() {
+        return source.get().iterator();
+    }
+
+    @Override
+    public void forEach(Consumer<? super T> action) {
+        this.source.get().forEach(action);
+    }
+}