From 8e3f8d31ddfb699a5b2a136b8ccc3ba99bc97c5f Mon Sep 17 00:00:00 2001
From: pipinet <zourongchuan@handaotech.com>
Date: Fri, 24 Nov 2023 09:33:38 +0800
Subject: [PATCH] feat: add RuntimeExpiringMemoizingSupplier

---
 .../RuntimeExpiringMemoizingSupplier.java     | 46 +++++++++++++++++++
 .../java/com/qwlabs/lang/WithExpiring.java    | 24 ++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 lang/src/main/java/com/qwlabs/lang/RuntimeExpiringMemoizingSupplier.java
 create mode 100644 lang/src/main/java/com/qwlabs/lang/WithExpiring.java

diff --git a/lang/src/main/java/com/qwlabs/lang/RuntimeExpiringMemoizingSupplier.java b/lang/src/main/java/com/qwlabs/lang/RuntimeExpiringMemoizingSupplier.java
new file mode 100644
index 0000000..f2f3004
--- /dev/null
+++ b/lang/src/main/java/com/qwlabs/lang/RuntimeExpiringMemoizingSupplier.java
@@ -0,0 +1,46 @@
+package com.qwlabs.lang;
+
+import com.google.common.base.Supplier;
+
+import javax.annotation.CheckForNull;
+
+public class RuntimeExpiringMemoizingSupplier<T> implements Supplier<T> {
+    private final Supplier<WithExpiring<T>> delegate;
+    @CheckForNull
+    private transient volatile T value;
+    private transient volatile long expirationNanos;
+
+    public RuntimeExpiringMemoizingSupplier(Supplier<WithExpiring<T>> delegate) {
+        this.delegate = delegate;
+    }
+
+    @Override
+    public T get() {
+        if (expirationNanos == 0) {
+            synchronized (this) {
+                if (expirationNanos == 0) {
+                    realLoad();
+                }
+            }
+        }
+        long now = System.nanoTime();
+        if (now > expirationNanos) {
+            return this.value;
+        }
+        synchronized (this) {
+            realLoad();
+        }
+        return value;
+    }
+
+    private void realLoad() {
+        try {
+            var withExpiring = delegate.get();
+            this.value = withExpiring.getData();
+            this.expirationNanos = System.nanoTime() + withExpiring.getExpiresInNanos();
+        } catch (Exception e) {
+            this.value = null;
+            this.expirationNanos = 0;
+        }
+    }
+}
diff --git a/lang/src/main/java/com/qwlabs/lang/WithExpiring.java b/lang/src/main/java/com/qwlabs/lang/WithExpiring.java
new file mode 100644
index 0000000..08d8c34
--- /dev/null
+++ b/lang/src/main/java/com/qwlabs/lang/WithExpiring.java
@@ -0,0 +1,24 @@
+package com.qwlabs.lang;
+
+import lombok.Getter;
+
+import java.util.concurrent.TimeUnit;
+
+@Getter
+public class WithExpiring<T> {
+    private final T data;
+    private final long expiresInNanos;
+
+    private WithExpiring(T data, long expiresInNanos) {
+        this.data = data;
+        this.expiresInNanos = expiresInNanos;
+    }
+
+    public static <T> WithExpiring<T> of(T data, long expiresIn, TimeUnit timeUnit) {
+        return new WithExpiring<>(data, timeUnit.toNanos(expiresIn));
+    }
+
+    public static <T> WithExpiring<T> of(T data, long expiresInNanos) {
+        return new WithExpiring<>(data, expiresInNanos);
+    }
+}