Add PermissionGranter to Barista (#20)

* Add PermissionGranter based on InfoJobs' app

* Add PermissionGranter's gradle dependencies

* Use BaristaSleepActions to sleep, avoiding Thread.sleep()

* Introduce PermissionGranter at README.md

* Avoid appcompat-v7 dependency to avoid dependency issues with Barista users

* Use Log.e instead of System.out

* Fix a bad message in the Log.e

* Override uiautomator version to enable Barista to work on projects below API 18

* Add the Exception to Log.e, to give more information about the issue

* Share that PermissionGranter needs API 18

README.md

@@ -92,6 +92,14 @@ assertDrawerIsClosed(R.id.drawer);
 assertThatBackButtonClosesTheApp();
 ```
 
+## Dealing with the runtime permissions dialog
+
+The new Marshmallow permissions system requires checking for permissions at runtime. As Espresso can't interact with the system dialog, Barista offers a way to allow permissions when needed.
+
+```java
+PermissionGranter.allowPermissionsIfNeeded(Manifest.permission.GET_ACCOUNTS);
+```
+
 # Download
 
 ```gradle

library/build.gradle

@@ -29,6 +29,8 @@ dependencies {
     compile('com.android.support.test.espresso:espresso-contrib:2.0') {
         exclude module: 'support-v4'
     }
+    compile 'com.android.support.test.uiautomator:uiautomator-v18:2.1.2'
+    compile 'com.android.support:support-annotations:25.1.0'
 }
 
 publish {

library/src/main/AndroidManifest.xml

@@ -1 +1,7 @@
-<manifest package="com.schibsted.spain.barista"/>
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:tools="http://schemas.android.com/tools"
+    package="com.schibsted.spain.barista">
+
+  <uses-sdk tools:overrideLibrary="android.support.test.uiautomator.v18"/>
+</manifest>

library/src/main/java/com/schibsted/spain/barista/permission/PermissionGranter.java

@@ -0,0 +1,54 @@
+package com.schibsted.spain.barista.permission;
+
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.os.Build;
+import android.support.annotation.NonNull;
+import android.support.annotation.RequiresApi;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.uiautomator.UiDevice;
+import android.support.test.uiautomator.UiObject;
+import android.support.test.uiautomator.UiObjectNotFoundException;
+import android.support.test.uiautomator.UiSelector;
+import android.util.Log;
+
+import static android.support.test.InstrumentationRegistry.getInstrumentation;
+import static com.schibsted.spain.barista.BaristaSleepActions.sleep;
+
+@RequiresApi(18)
+public class PermissionGranter {
+
+  private static final int PERMISSIONS_DIALOG_DELAY = 3000;
+  private static final int GRANT_BUTTON_INDEX = 1;
+
+  public static void allowPermissionsIfNeeded(String permissionNeeded) {
+    try {
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && !hasNeededPermission(InstrumentationRegistry.getTargetContext(),
+          permissionNeeded)) {
+        sleep(PERMISSIONS_DIALOG_DELAY);
+        UiDevice device = UiDevice.getInstance(getInstrumentation());
+        UiObject allowPermissions = device.findObject(new UiSelector()
+            .clickable(true)
+            .checkable(false)
+            .index(GRANT_BUTTON_INDEX));
+        if (allowPermissions.exists()) {
+          allowPermissions.click();
+        }
+      }
+    } catch (UiObjectNotFoundException e) {
+      Log.e("Barista", "There is no permissions dialog to interact with", e);
+    }
+  }
+
+  private static boolean hasNeededPermission(Context context, String permissionNeeded) {
+    int permissionStatus = checkSelfPermission(context, permissionNeeded);
+    return permissionStatus == PackageManager.PERMISSION_GRANTED;
+  }
+
+  private static int checkSelfPermission(@NonNull Context context, @NonNull String permission) {
+    if (permission == null) {
+      throw new IllegalArgumentException("permission is null");
+    }
+    return context.checkPermission(permission, android.os.Process.myPid(), android.os.Process.myUid());
+  }
+}