From 7dd59dbf2ab139f6e0fd8f1cfee296b3d5c69512 Mon Sep 17 00:00:00 2001
From: Lev Shagalov <lllewik@gmail.com>
Date: Fri, 15 Jul 2022 09:05:57 +0300
Subject: [PATCH] LruCache

---
 .../kotlin/centre/sciprog/maps/LruCache.kt    | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 src/commonMain/kotlin/centre/sciprog/maps/LruCache.kt

diff --git a/src/commonMain/kotlin/centre/sciprog/maps/LruCache.kt b/src/commonMain/kotlin/centre/sciprog/maps/LruCache.kt
new file mode 100644
index 0000000..9619eb0
--- /dev/null
+++ b/src/commonMain/kotlin/centre/sciprog/maps/LruCache.kt
@@ -0,0 +1,61 @@
+package centre.sciprog.maps
+
+import kotlin.jvm.Synchronized
+
+
+class LruCache<K, V>(
+    private var capacity: Int,
+) {
+
+    private val cache = mutableMapOf<K, V>()
+    private val order = mutableListOf<K>()
+
+    @Synchronized
+    fun getCache() = cache.toMap()
+
+    @Synchronized
+    fun getOrder() = order.toList()
+
+    @Synchronized
+    fun put(key: K, value: V) = internalPut(key, value)
+
+    @Synchronized
+    operator fun get(key: K) = internalGet(key)
+
+    @Synchronized
+    fun remove(key: K) {
+        cache.remove(key)
+        order.remove(key)
+    }
+
+    @Synchronized
+    fun getOrPut(key: K, callback: () -> V): V {
+        val internalGet = internalGet(key)
+        return internalGet ?: callback().also { internalPut(key, it) }
+    }
+
+    @Synchronized
+    fun clear(newCapacity: Int? = null) {
+        cache.clear()
+        order.clear()
+        capacity = newCapacity ?: capacity
+    }
+
+    private fun internalGet(key: K): V? {
+        val value = cache[key]
+        if (value != null) {
+            order.remove(key)
+            order.add(key)
+        }
+        return value
+    }
+
+    private fun internalPut(key: K, value: V) {
+        if (cache.size >= capacity) {
+            cache.remove(order.removeAt(0))
+        }
+        cache[key] = value
+        order.add(key)
+    }
+
+}