1 files changed, 110 insertions, 0 deletions
diff --git a/src/main/kotlin/util/collections/WeakCache.kt b/src/main/kotlin/util/collections/WeakCache.kt
new file mode 100644
index 0000000..38f9886
--- /dev/null
+++ b/src/main/kotlin/util/collections/WeakCache.kt
@@ -0,0 +1,110 @@
+package moe.nea.firmament.util.collections
+
+import java.lang.ref.ReferenceQueue
+import java.lang.ref.WeakReference
+import moe.nea.firmament.features.debug.DebugLogger
+
+/**
+ * Cache class that uses [WeakReferences][WeakReference] to only cache values while there is still a life reference to
+ * the key. Each key can have additional extra data that is used to look up values. That extra data is not required to
+ * be a life reference. The main Key is compared using strict reference equality. This map is not synchronized.
+ */
+class WeakCache<Key : Any, ExtraKey : Any, Value : Any>(val name: String) {
+    private val queue = object : ReferenceQueue<Key>() {}
+    private val map = mutableMapOf<Ref, Value>()
+
+    val size: Int
+        get() {
+            clearOldReferences()
+            return map.size
+        }
+
+    fun clearOldReferences() {
+        var successCount = 0
+        var totalCount = 0
+        while (true) {
+            val reference = queue.poll() ?: break
+            totalCount++
+            if (map.remove(reference) != null)
+                successCount++
+        }
+        if (totalCount > 0)
+            logger.log { "Cleared $successCount/$totalCount references from queue" }
+    }
+
+    fun get(key: Key, extraData: ExtraKey): Value? {
+        clearOldReferences()
+        return map[Ref(key, extraData)]
+    }
+
+    fun put(key: Key, extraData: ExtraKey, value: Value) {
+        clearOldReferences()
+        map[Ref(key, extraData)] = value
+    }
+
+    fun getOrPut(key: Key, extraData: ExtraKey, value: (Key, ExtraKey) -> Value): Value {
+        clearOldReferences()
+        return map.getOrPut(Ref(key, extraData)) { value(key, extraData) }
+    }
+
+    fun clear() {
+        map.clear()
+    }
+
+    init {
+        allInstances.add(this)
+    }
+
+    companion object {
+        val allInstances = InstanceList<WeakCache<*, *, *>>("WeakCaches")
+        private val logger = DebugLogger("WeakCache")
+        fun <Key : Any, Value : Any> memoize(name: String, function: (Key) -> Value):
+            CacheFunction.NoExtraData<Key, Value> {
+            return CacheFunction.NoExtraData(WeakCache(name), function)
+        }
+
+        fun <Key : Any, ExtraKey : Any, Value : Any> memoize(name: String, function: (Key, ExtraKey) -> Value):
+            CacheFunction.WithExtraData<Key, ExtraKey, Value> {
+            return CacheFunction.WithExtraData(WeakCache(name), function)
+        }
+    }
+
+    inner class Ref(
+        weakInstance: Key,
+        val extraData: ExtraKey,
+    ) : WeakReference<Key>(weakInstance, queue) {
+        val hashCode = System.identityHashCode(weakInstance) * 31 + extraData.hashCode()
+        override fun equals(other: Any?): Boolean {
+            if (other !is WeakCache<*, *, *>.Ref) return false
+            return other.hashCode == this.hashCode
+                && other.get() === this.get()
+                && other.extraData == this.extraData
+        }
+
+        override fun hashCode(): Int {
+            return hashCode
+        }
+    }
+
+    interface CacheFunction {
+        val cache: WeakCache<*, *, *>
+
+        data class NoExtraData<Key : Any, Value : Any>(
+            override val cache: WeakCache<Key, Unit, Value>,
+            val wrapped: (Key) -> Value,
+        ) : CacheFunction, (Key) -> Value {
+            override fun invoke(p1: Key): Value {
+                return cache.getOrPut(p1, Unit, { a, _ -> wrapped(a) })
+            }
+        }
+
+        data class WithExtraData<Key : Any, ExtraKey : Any, Value : Any>(
+            override val cache: WeakCache<Key, ExtraKey, Value>,
+            val wrapped: (Key, ExtraKey) -> Value,
+        ) : CacheFunction, (Key, ExtraKey) -> Value {
+            override fun invoke(p1: Key, p2: ExtraKey): Value {
+                return cache.getOrPut(p1, p2, wrapped)
+            }
+        }
+    }
+}