RateLimiter: Utility class that decides whether we should fetch some data or not.

Author: li2

common/src/main/java/me/li2/android/common/arch/RateLimiter.kt

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+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.
+ */
+package me.li2.android.common.arch
+
+import android.os.SystemClock
+import androidx.collection.ArrayMap
+import java.util.concurrent.TimeUnit
+
+/**
+ * Utility class that decides whether we should fetch some data or not.
+ */
+class RateLimiter<KEY>(timeout: Int, timeUnit: TimeUnit) {
+    private val timestamps = ArrayMap<KEY, Long>()
+    private val timeout: Long = timeUnit.toMillis(timeout.toLong())
+
+    @Synchronized
+    fun shouldFetch(key: KEY): Boolean {
+        val lastFetched = timestamps[key]
+        val now = now()
+        if (lastFetched == null) {
+            timestamps[key] = now
+            return true
+        }
+        if (now - lastFetched > timeout) {
+            timestamps[key] = now
+            return true
+        }
+        return false
+    }
+
+    private fun now(): Long {
+        return SystemClock.uptimeMillis()
+    }
+
+    @Synchronized
+    fun reset(key: KEY) {
+        timestamps.remove(key)
+    }
+}