README.md file added

README.md

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+# react-native-session-stats
+
+Package provides context that stores information about user session. Next information is available - `timeSpent`, `sessionCount` and `lastSessionEnd`. Package can be used for internal analytics, as well as for implementing UI user will interact with. Some possible use cases are:
+- show user session time;
+- show popup, based on session count or session time;
+- log out user after specified session time;
+- send warning push notifications on session end.
+
+## Install
+
+```
+// npm usage
+npm i @kkurko/react-native-session-stats
+
+// yarn usage
+yarn add @kkurko/react-native-session-stats
+```
+
+## Usage
+
+The `SessionStats` component takes two props: `onSessionStart` is fired when the app's state changes to `active`, `onSessionEnd`, when it changes to `inactive` or `background`.
+
+```javascript
+import SessionStats from '@kkurko/react-native-session-stats';
+
+// ...
+
+<SessionStats
+  onSessionStart={({
+    timeSpent, // total time spent, in seconds
+    sessionCount, // number of sessions as of at opening the app
+    lastSessionEnd, // timestamp of the last session end
+  }) => { /* ... */ }}
+  onSessionEnd={({
+    timeSpent, // total time spent in seconds
+    sessionCount, // and number of sessions as of at closing the app
+    lastSessionEnd, // timestamp of the last session end
+    sessionDuration, // the length of the ending session, in seconds
+  }) => { /* ... */ }}
+/>
+```
+
+`SessionStats` is used as a context provider
+
+```javascript
+import SessionStats from '@kkurko/react-native-session-stats';
+
+// ...
+
+<SessionStats>
+  <App />
+<SessionStats/>
+```
+
+Values are available via `useSessionStats` hook:
+
+```javascript
+import { useSessionStats } from '@kkurko/react-native-session-stats';
+
+const SomeComponent = () => {
+    const { timeSpent, sessionCount, lastSessionEnd } = useSessionStats();
+    //...
+};
+```
+
+
+or via `sessionStatsContext` and `useContext` hook:
+
+```javascript
+import { useContext } from 'react';
+import { sessionStatsContext } from '@kkurko/react-native-session-stats';
+
+const SomeComponent = () => {
+    const { timeSpent, sessionCount, lastSessionEnd } = useContext(sessionStatsContext);
+    //...
+};
+```