MediaMetrics: Add device-based actions for Bluetooth

Log summary group statistics by device.

Test: adb shell dumpsys media.metrics
Bug: 149850236
Change-Id: I31fef89fa020de175e59784049ef4741914f3a2c
diff --git a/services/mediametrics/TimedAction.h b/services/mediametrics/TimedAction.h
new file mode 100644
index 0000000..c7ef585
--- /dev/null
+++ b/services/mediametrics/TimedAction.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma once
+
+#include <android-base/thread_annotations.h>
+#include <chrono>
+#include <map>
+#include <mutex>
+#include <thread>
+
+namespace android::mediametrics {
+
+class TimedAction {
+public:
+    TimedAction() : mThread{[this](){threadLoop();}} {}
+
+    ~TimedAction() {
+        quit();
+    }
+
+    // TODO: return a handle for cancelling the action?
+    template <typename T> // T is in units of std::chrono::duration.
+    void postIn(const T& time, std::function<void()> f) {
+        postAt(std::chrono::steady_clock::now() + time, f);
+    }
+
+    template <typename T> // T is in units of std::chrono::time_point
+    void postAt(const T& targetTime, std::function<void()> f) {
+        std::lock_guard l(mLock);
+        if (mQuit) return;
+        if (mMap.empty() || targetTime < mMap.begin()->first) {
+            mMap.emplace_hint(mMap.begin(), targetTime, std::move(f));
+            mCondition.notify_one();
+        } else {
+            mMap.emplace(targetTime, std::move(f));
+        }
+    }
+
+    void clear() {
+        std::lock_guard l(mLock);
+        mMap.clear();
+    }
+
+    void quit() {
+        {
+            std::lock_guard l(mLock);
+            if (mQuit) return;
+            mQuit = true;
+            mMap.clear();
+            mCondition.notify_all();
+        }
+        mThread.join();
+    }
+
+    size_t size() const {
+        std::lock_guard l(mLock);
+        return mMap.size();
+    }
+
+private:
+    void threadLoop() NO_THREAD_SAFETY_ANALYSIS { // thread safety doesn't cover unique_lock
+        std::unique_lock l(mLock);
+        while (!mQuit) {
+            auto sleepUntilTime = std::chrono::time_point<std::chrono::steady_clock>::max();
+            if (!mMap.empty()) {
+                sleepUntilTime = mMap.begin()->first;
+                if (sleepUntilTime <= std::chrono::steady_clock::now()) {
+                    auto node = mMap.extract(mMap.begin()); // removes from mMap.
+                    l.unlock();
+                    node.mapped()();
+                    l.lock();
+                    continue;
+                }
+            }
+            mCondition.wait_until(l, sleepUntilTime);
+        }
+    }
+
+    mutable std::mutex mLock;
+    std::condition_variable mCondition GUARDED_BY(mLock);
+    bool mQuit GUARDED_BY(mLock) = false;
+    std::multimap<std::chrono::time_point<std::chrono::steady_clock>, std::function<void()>>
+            mMap GUARDED_BY(mLock); // multiple functions could execute at the same time.
+
+    // needs to be initialized after the variables above, done in constructor initializer list.
+    std::thread mThread;
+};
+
+} // namespace android::mediametrics