From 859849bd47e663432fbc5c2b4e6df989b2c2fbbc Mon Sep 17 00:00:00 2001
From: Colin Henry <jchenry@users.noreply.github.com>
Date: Thu, 15 Dec 2022 22:00:51 -0800
Subject: [PATCH] stub of tiered cache

---
 cache/interface.go |  6 ++++++
 cache/tiered.go    | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 cache/interface.go
 create mode 100644 cache/tiered.go

diff --git a/cache/interface.go b/cache/interface.go
new file mode 100644
index 0000000..bfb71bf
--- /dev/null
+++ b/cache/interface.go
@@ -0,0 +1,6 @@
+package cache
+
+type Interface[K comparable, V any] interface {
+	Get(key K) V
+	Put(key K, value V)
+}
diff --git a/cache/tiered.go b/cache/tiered.go
new file mode 100644
index 0000000..e538c93
--- /dev/null
+++ b/cache/tiered.go
@@ -0,0 +1,34 @@
+package cache
+
+import "reflect"
+
+type tieredCache[K comparable, V any] struct {
+	inner Interface[K, V]
+	outer Interface[K, V]
+}
+
+func NewTieredCache[K comparable, V any](inner, outer Interface[K, V]) Interface[K, V] {
+	return &tieredCache[K, V]{
+		inner: inner,
+		outer: outer,
+	}
+}
+
+func (t *tieredCache[K, V]) Get(key K) V {
+	var zero, value V
+	value = t.inner.Get(key)
+	if reflect.DeepEqual(value, zero) {
+		value = t.outer.Get(key)
+		// if required, add value to inner cache for future requests
+	}
+	return value
+}
+
+func (t *tieredCache[K, V]) Put(key K, value V) {
+	t.inner.Put(key, value)
+
+	// add key to outer cache asynchronously
+	go func(key K) {
+		t.outer.Put(key, value)
+	}(key)
+}