add single and singleOrNull to EntityBag

Quillraven · Oct 1, 2024 · 300b37d · 300b37d
1 parent 596bf8e
commit 300b37d
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diff --git a/src/commonMain/kotlin/com/github/quillraven/fleks/collection/entityBag.kt b/src/commonMain/kotlin/com/github/quillraven/fleks/collection/entityBag.kt
@@ -369,6 +369,30 @@ interface EntityBag {
      */
     fun randomOrNull(): Entity?
 
+    /**
+     * Returns the single [entity][Entity] of the bag, or throws an exception
+     * if the bag is empty or has more than one [entity][Entity].
+     */
+    fun single(): Entity
+
+    /**
+     * Returns the single [entity][Entity] of the bag matching the given [predicate],
+     * or throws an exception if the bag is empty or has more than one [entity][Entity].
+     */
+    fun single(predicate: (Entity) -> Boolean): Entity
+
+    /**
+     * Returns single [entity][Entity] of the bag, or null
+     * if the bag is empty or has more than one [entity][Entity].
+     */
+    fun singleOrNull(): Entity?
+
+    /**
+     * Returns the single [entity][Entity] of the bag matching the given [predicate],
+     * or null if the bag is empty or has more than one [entity][Entity].
+     */
+    fun singleOrNull(predicate: (Entity) -> Boolean): Entity?
+
     /**
      * Returns a [List] containing the first [n] [entities][Entity].
      */
@@ -1122,6 +1146,68 @@ class MutableEntityBag(
         return values[Random.Default.nextInt(size)]
     }
 
+    /**
+     * Returns the single [entity][Entity] of the bag, or throws an exception
+     * if the bag is empty or has more than one [entity][Entity].
+     */
+    override fun single(): Entity {
+        return when (size) {
+            0 -> throw NoSuchElementException("Bag is empty.")
+            1 -> values[0]
+            else -> throw IllegalArgumentException("Bag has more than one element.")
+        }
+    }
+
+    /**
+     * Returns the single [entity][Entity] of the bag matching the given [predicate],
+     * or throws an exception if the bag is empty or has more than one [entity][Entity].
+     */
+    override fun single(predicate: (Entity) -> Boolean): Entity {
+        var single: Entity? = null
+        for (i in 0 until size) {
+            val entity = values[i]
+            if (predicate(entity)) {
+                if (single != null) {
+                    throw IllegalArgumentException("Bag contains more than one matching element.")
+                }
+                single = entity
+            }
+        }
+        if (single == null) {
+            throw NoSuchElementException("Bag contains no element matching the predicate.")
+        }
+        return single
+    }
+
+    /**
+     * Returns single [entity][Entity] of the bag, or null
+     * if the bag is empty or has more than one [entity][Entity].
+     */
+    override fun singleOrNull(): Entity? {
+        return when (size) {
+            1 -> values[0]
+            else -> null
+        }
+    }
+
+    /**
+     * Returns the single [entity][Entity] of the bag matching the given [predicate],
+     * or null if the bag is empty or has more than one [entity][Entity].
+     */
+    override fun singleOrNull(predicate: (Entity) -> Boolean): Entity? {
+        var single: Entity? = null
+        for (i in 0 until size) {
+            val entity = values[i]
+            if (predicate(entity)) {
+                if (single != null) {
+                    return null
+                }
+                single = entity
+            }
+        }
+        return single
+    }
+
     /**
      * Returns a [List] containing the first [n] [entities][Entity].
      */

diff --git a/src/commonTest/kotlin/com/github/quillraven/fleks/collection/EntityBagTest.kt b/src/commonTest/kotlin/com/github/quillraven/fleks/collection/EntityBagTest.kt
@@ -12,6 +12,9 @@ class EntityBagTest {
         this += testEntity1
         this += testEntity2
     }
+    private val testBagSingle = MutableEntityBag(2).apply {
+        this += testEntity1
+    }
 
     private fun bagOf(entity: Entity) = MutableEntityBag(1).apply {
         this += entity
@@ -595,6 +598,26 @@ class EntityBagTest {
         assertTrue(actual == testEntity1 || actual == testEntity2)
     }
 
+    @Test
+    fun testSingle() {
+        assertEquals(testEntity1, testBagSingle.single())
+        assertEquals(testEntity1, testBagSingle.single { it == testEntity1 })
+        assertFailsWith<IllegalArgumentException> { testBag.single() }
+        assertFailsWith<IllegalArgumentException> { bagOf(testEntity1, testEntity1).single { it == testEntity1 } }
+        assertFailsWith<NoSuchElementException> { MutableEntityBag().single() }
+        assertFailsWith<NoSuchElementException> { testBag.single { it.id == 3 } }
+    }
+
+    @Test
+    fun testSingleOrNull() {
+        assertEquals(testEntity1, testBagSingle.singleOrNull())
+        assertEquals(testEntity1, testBagSingle.singleOrNull { it == testEntity1 })
+        assertNull(testBag.singleOrNull())
+        assertNull(bagOf(testEntity1, testEntity1).singleOrNull { it == testEntity1 })
+        assertNull(MutableEntityBag().singleOrNull())
+        assertNull(testBag.singleOrNull { it.id == 3 })
+    }
+
     @Test
     fun testTake() {
         assertTrue(testBag.take(-1).isEmpty())