Add UniqueQueue

Signed-off-by: Graham <gpe@openrs2.org>

util/src/main/kotlin/org/openrs2/util/collect/UniqueQueue.kt

@@ -0,0 +1,25 @@
+package org.openrs2.util.collect
+
+public class UniqueQueue<T> {
+    private val queue = ArrayDeque<T>()
+    private val set = mutableSetOf<T>()
+
+    public fun add(v: T): Boolean {
+        if (set.add(v)) {
+            queue.addLast(v)
+            return true
+        }
+
+        return false
+    }
+
+    public fun poll(): T? {
+        val v = queue.removeFirstOrNull()
+        if (v != null) {
+            set.remove(v)
+            return v
+        }
+
+        return null
+    }
+}

util/src/test/kotlin/org/openrs2/util/collect/UniqueQueueTest.kt

@@ -0,0 +1,21 @@
+package org.openrs2.util.collect
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class UniqueQueueTest {
+    @Test
+    fun testAddPoll() {
+        val queue = UniqueQueue<String>()
+        assertTrue(queue.add("a"))
+        assertTrue(queue.add("b"))
+        assertFalse(queue.add("a"))
+
+        assertEquals("a", queue.poll())
+        assertEquals("b", queue.poll())
+        assertNull(queue.poll())
+    }
+}