Add dynamic config feature and adjust default endpoint to api2 (#247)

* Add dynamic config feature and adjust default endpoint to api2

* Revert change on test file

* Minor format change

src/main/java/com/amplitude/api/AmplitudeClient.java

@@ -161,6 +161,7 @@ public class AmplitudeClient {
     private boolean flushEventsOnClose = true;
     private String libraryName = Constants.LIBRARY;
     private String libraryVersion = Constants.VERSION;
+    private boolean useDynamicConfig = false;
 
     private AtomicBoolean updateScheduled = new AtomicBoolean(false);
     /**
@@ -269,6 +270,15 @@ public synchronized AmplitudeClient initialize(final Context context, final Stri
                         AmplitudeClient.upgradePrefs(context);
                         AmplitudeClient.upgradeSharedPrefsToDB(context);
                     }
+
+                    if (useDynamicConfig) {
+                        ConfigManager.getInstance().refresh(new ConfigManager.RefreshListener() {
+                            @Override
+                            public void onFinished() {
+                                url = ConfigManager.getInstance().getIngestionEndpoint();
+                            }
+                        });
+                    }
                     httpClient = new OkHttpClient();
                     deviceInfo = new DeviceInfo(context, this.locationListening);
                     deviceId = initializeDeviceId();
@@ -671,6 +681,19 @@ public AmplitudeClient trackSessionEvents(boolean trackingSessionEvents) {
         return this;
     }
 
+    /**
+     * Turning this flag on will find the best server url automatically based on users' geo location.
+     * Note:
+     * 1. If you have your own proxy server and use `setServerUrl` API, please leave this off.
+     * 2. If you have users in China Mainland, we suggest you turn this on.
+     *
+     * @param useDynamicConfig whether to enable dynamic config
+     * @return the AmplitudeClient
+     */
+    public AmplitudeClient setUseDynamicConfig(boolean useDynamicConfig) {
+        this.useDynamicConfig = useDynamicConfig;
+        return this;
+    }
     /**
      * Set foreground tracking to true.
      */
@@ -1329,6 +1352,14 @@ public void run() {
                 if (Utils.isEmptyString(apiKey)) {
                     return;
                 }
+                if (useDynamicConfig) {
+                    ConfigManager.getInstance().refresh(new ConfigManager.RefreshListener() {
+                        @Override
+                        public void onFinished() {
+                            url = ConfigManager.getInstance().getIngestionEndpoint();
+                        }
+                    });
+                }
                 startNewSessionIfNeeded(timestamp);
                 inForeground = true;
             }

src/main/java/com/amplitude/api/ConfigManager.java

@@ -0,0 +1,71 @@
+package com.amplitude.api;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.URL;
+
+public class ConfigManager {
+    private static String KEY_INGESTION_ENDPOINT = "ingestionEndpoint";
+
+    private static ConfigManager instance = null;
+
+    private String ingestionEndpoint = Constants.EVENT_LOG_URL;
+
+    public String getIngestionEndpoint() {
+        return ingestionEndpoint;
+    }
+
+    private ConfigManager() {
+    }
+
+    public void refresh(RefreshListener listener) {
+        try {
+            URL obj = new URL(Constants.DYNAMIC_CONFIG_URL);
+            HttpURLConnection con = (HttpURLConnection) obj.openConnection();
+
+            int responseCode = con.getResponseCode();
+
+            if (responseCode == 200) {
+                BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
+                String inputLine;
+                StringBuffer response = new StringBuffer();
+
+                while ((inputLine = in.readLine()) != null) {
+                    response.append(inputLine);
+                }
+                in.close();
+
+                JSONObject json = new JSONObject(response.toString());
+                if (json.has(KEY_INGESTION_ENDPOINT)) {
+                    this.ingestionEndpoint = "https://" + json.getString(KEY_INGESTION_ENDPOINT);
+                }
+            }
+        } catch (MalformedURLException e) {
+
+        } catch (IOException e) {
+
+        } catch (JSONException e) {
+
+        }
+
+        listener.onFinished();
+    }
+
+    public static ConfigManager getInstance() {
+        if (instance == null) {
+            instance = new ConfigManager();
+        }
+
+        return instance;
+    }
+
+    interface RefreshListener {
+        void onFinished();
+    }
+}

src/main/java/com/amplitude/api/Constants.java

@@ -10,7 +10,8 @@ public class Constants {
     public static final String VERSION_UNKNOWN = "unknown-version";
     public static final String PLATFORM = "Android";
 
-    public static final String EVENT_LOG_URL = "https://api.amplitude.com/";
+    public static final String EVENT_LOG_URL = "https://api2.amplitude.com/";
+    public static final String DYNAMIC_CONFIG_URL = "https://regionconfig.amplitude.com/";
 
     public static final String PACKAGE_NAME = "com.amplitude.api";