feat: Add ODP LRU Cache (#777)

Author: opti-jnguyen

packages/optimizely-sdk/lib/core/odp/index.ts

@@ -0,0 +1,15 @@
+/**
+ * Copyright 2022, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */

packages/optimizely-sdk/lib/core/odp/lru_cache/CacheElement.tests.ts

@@ -0,0 +1,53 @@
+/**
+ * Copyright 2022, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { assert } from 'chai'
+import { CacheElement } from './CacheElement';
+
+const sleep = async (ms: number) => {
+    return await new Promise(r => setTimeout(r, ms))
+}
+
+describe('/odp/lru_cache/CacheElement', () => {
+    let element: CacheElement<string>
+
+    beforeEach(() => {
+        element = new CacheElement('foo')
+    })
+
+    it('should initialize a valid CacheElement', () => {
+        assert.exists(element)
+        assert.equal(element.value, 'foo')
+        assert.isNotNull(element.time)
+        assert.doesNotThrow(() => element.is_stale(0))
+    })
+
+    it('should return false if not stale based on timeout', () => {
+        const timeoutLong = 1000
+        assert.equal(element.is_stale(timeoutLong), false)
+    })
+
+    it('should return false if not stale because timeout is less than or equal to 0', () => {
+        const timeoutNone = 0
+        assert.equal(element.is_stale(timeoutNone), false)
+    })
+
+    it('should return true if stale based on timeout', async () => {
+        await sleep(100)
+        const timeoutShort = 1
+        assert.equal(element.is_stale(timeoutShort), true)
+    })
+})

packages/optimizely-sdk/lib/core/odp/lru_cache/CacheElement.ts

@@ -0,0 +1,38 @@
+/**
+ * Copyright 2022, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * CacheElement represents an individual generic item within the LRUCache
+ */
+export class CacheElement<V> {
+    private _value: V | null
+    private _time: number
+
+    get value(): V | null { return this._value }
+    get time(): number { return this._time }
+
+    constructor(value: V | null = null) {
+        this._value = value
+        this._time = Date.now()
+    }
+
+    public is_stale(timeout: number): boolean {
+        if (timeout <= 0) return false
+        return Date.now() - this._time >= timeout
+    }
+}
+
+export default CacheElement