[kotlin-tooling-core] Implement generic Interner

^KT-55475 Verification Pending

libraries/tools/kotlin-tooling-core/api/kotlin-tooling-core.api

@@ -142,6 +142,17 @@ public abstract interface class org/jetbrains/kotlin/tooling/core/HasMutableExtr
 	public abstract fun getExtras ()Lorg/jetbrains/kotlin/tooling/core/MutableExtras;
 }
 
+public abstract interface class org/jetbrains/kotlin/tooling/core/Interner {
+	public abstract fun getOrPut (Ljava/lang/Object;)Ljava/lang/Object;
+}
+
+public final class org/jetbrains/kotlin/tooling/core/InternerKt {
+	public static final fun Interner (Ljava/util/concurrent/locks/Lock;)Lorg/jetbrains/kotlin/tooling/core/Interner;
+	public static synthetic fun Interner$default (Ljava/util/concurrent/locks/Lock;ILjava/lang/Object;)Lorg/jetbrains/kotlin/tooling/core/Interner;
+	public static final fun WeakInterner (Ljava/util/concurrent/locks/Lock;)Lorg/jetbrains/kotlin/tooling/core/Interner;
+	public static synthetic fun WeakInterner$default (Ljava/util/concurrent/locks/Lock;ILjava/lang/Object;)Lorg/jetbrains/kotlin/tooling/core/Interner;
+}
+
 public final class org/jetbrains/kotlin/tooling/core/KotlinToolingVersion : java/io/Serializable, java/lang/Comparable {
 	public fun <init> (IIILjava/lang/String;)V
 	public synthetic fun compareTo (Ljava/lang/Object;)I

libraries/tools/kotlin-tooling-core/src/main/kotlin/org/jetbrains/kotlin/tooling/core/Interner.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("FunctionName")
+
+package org.jetbrains.kotlin.tooling.core
+
+import org.jetbrains.kotlin.tooling.core.InternerImpl.Store.Strong
+import org.jetbrains.kotlin.tooling.core.InternerImpl.Store.Weak
+import java.lang.ref.WeakReference
+import java.util.*
+import java.util.concurrent.locks.Lock
+import kotlin.concurrent.withLock
+
+fun WeakInterner(lock: Lock? = null): Interner = InternerImpl(Weak(), lock)
+
+fun Interner(lock: Lock? = null): Interner = InternerImpl(Strong(), lock)
+
+interface Interner {
+    fun <T : Any> getOrPut(value: T): T
+}
+
+private class InternerImpl(
+    private val store: Store,
+    private val lock: Lock? = null
+) : Interner {
+
+    interface Store {
+        fun <T : Any> getOrPut(value: T): T
+
+        class Weak : Store {
+            private val references = WeakHashMap<Any, WeakReference<Any>>()
+            override fun <T : Any> getOrPut(value: T): T {
+                @Suppress("unchecked_cast")
+                return (references.getOrPut(value) { WeakReference(value) }.get() ?: run {
+                    references[value] = WeakReference(value)
+                    value
+                }) as T
+            }
+        }
+
+        @Suppress("UNCHECKED_CAST")
+        class Strong : Store {
+            private val references = hashMapOf<Any, Any>()
+            override fun <T : Any> getOrPut(value: T): T {
+                return references.getOrPut(value) { value } as T
+            }
+        }
+    }
+
+    override fun <T : Any> getOrPut(value: T): T {
+        return lock?.withLock { store.getOrPut(value) } ?: store.getOrPut(value)
+    }
+}

libraries/tools/kotlin-tooling-core/src/test/kotlin/org/jetbrains/kotlin/tooling/core/InternerTest.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("UNUSED_VALUE")
+
+package org.jetbrains.kotlin.tooling.core
+
+import org.junit.Test
+import kotlin.test.assertSame
+
+class InternerTest {
+
+    data class Sample(val value: Int)
+
+    @Test
+    fun `test - weak interner`() {
+        doTest(WeakInterner())
+    }
+
+    @Test
+    fun `test - strong interner`() {
+        doTest(Interner())
+    }
+
+    private fun doTest(interner: Interner) {
+        val sample0A = Sample(0)
+        val sample0B = Sample(0)
+        val sample1A = Sample(1)
+        val sample1B = Sample(1)
+
+        assertSame(sample0A, interner.getOrPut(sample0A))
+        assertSame(sample0A, interner.getOrPut(sample0B))
+        assertSame(sample1A, interner.getOrPut(sample1A))
+        assertSame(sample1A, interner.getOrPut(sample1B))
+        assertSame(sample0A, interner.getOrPut(sample0A))
+        assertSame(sample0A, interner.getOrPut(sample0B))
+    }
+}