Add share button for safety numbers

Fixes #5798
Closes #5854
// FREEBIE

res/menu/verify_identity.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+      xmlns:app="http://schemas.android.com/apk/res-auto" >
+    <item android:id="@+id/verify_identity__share"
+          android:title="@string/verify_identity__share_safety_numbers"
+          android:icon="@drawable/ic_share_white_24dp"
+          app:showAsAction="ifRoom" />
+</menu>

res/values/strings.xml

@@ -565,6 +565,9 @@
     <string name="VerifyIdentityActivity_your_contact_is_running_an_old_version_of_signal">Your contact is running an old version of Signal, please ask them to update before verifying safety numbers.</string>
     <string name="VerifyIdentityActivity_you_re_attempting_to_verify_safety_numbers_with">You\'re attempting to verify safety numbers with %1$s, but scanned %2$s instead.</string>
     <string name="VerifyIdentityActivity_the_scanned_qr_code_is_not_a_correctly_formatted_safety_number">The scanned QR code is not a correctly formatted safety number verification code.  Please try scanning again.</string>
+    <string name="VerifyIdentityActivity_share_safety_numbers_via">Share safety numbers via...</string>
+    <string name="VerifyIdentityActivity_our_signal_safety_numbers">Our Signal safety numbers:</string>
+    <string name="VerifyIdentityActivity_no_app_to_share_to">It looks like you don\'t have any apps to share to.</string>
 
     <!-- KeyExchangeInitiator -->
     <string name="KeyExchangeInitiator_initiate_despite_existing_request_question">Initiate despite existing request?</string>
@@ -936,6 +939,9 @@
     <!-- verify_display_fragment -->
     <string name="verify_display_fragment__scan_the_code_on_your_contact_s_phone_or_ask_them_to_scan_your_code_to_verify_that_your_messages_are_end_to_end_encrypted_you_can_alternately_compare_the_number_above">If you wish to verify the security of your end-to-end encryption with %s, compare the numbers above with the numbers on their device. Alternately, you can scan the code on their phone, or ask them to scan your code.</string>
     <string name="verify_display_fragment__tap_to_scan">Tap to scan</string>
+
+    <!-- verify_identity -->
+    <string name="verify_identity__share_safety_numbers">Share safety numbers</string>
     
     <!-- message_details_header -->
     <string name="message_details_header__issues_need_your_attention">Some issues need your attention.</string>

src/org/thoughtcrime/securesms/VerifyIdentityActivity.java

@@ -16,7 +16,9 @@
  */
 package org.thoughtcrime.securesms;
 
+import android.content.ActivityNotFoundException;
 import android.content.Context;
+import android.content.Intent;
 import android.content.res.Configuration;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
@@ -33,6 +35,8 @@ import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentTransaction;
 import android.util.Log;
 import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
@@ -122,10 +126,22 @@ public class VerifyIdentityActivity extends PassphraseRequiredActionBarActivity
     }
   }
 
+  @Override
+  public boolean onPrepareOptionsMenu(Menu menu) {
+    super.onPrepareOptionsMenu(menu);
+
+    menu.clear();
+    MenuInflater inflater = this.getMenuInflater();
+    inflater.inflate(R.menu.verify_identity, menu);
+
+    return true;
+  }
+
   @Override
   public boolean onOptionsItemSelected(MenuItem item) {
     switch (item.getItemId()) {
-      case android.R.id.home: finish(); return true;
+      case R.id.verify_identity__share: handleShare();  return true;
+      case android.R.id.home:           finish();       return true;
     }
 
     return false;
@@ -173,6 +189,25 @@ public class VerifyIdentityActivity extends PassphraseRequiredActionBarActivity
     }
   }
 
+  private void handleShare() {
+    String shareString =
+        getString(R.string.VerifyIdentityActivity_our_signal_safety_numbers) + "\n" +
+        displayFragment.getFormattedSafetyNumbers() + "\n";
+
+    Intent intent = new Intent();
+    intent.setAction(Intent.ACTION_SEND);
+    intent.putExtra(Intent.EXTRA_SUBJECT, getString(R.string.VerifyIdentityActivity_our_signal_safety_numbers));
+    intent.putExtra(Intent.EXTRA_TEXT, shareString);
+    intent.setType("text/plain");
+
+    try {
+      startActivity(Intent.createChooser(intent, getString(R.string.VerifyIdentityActivity_share_safety_numbers_via)));
+    } catch (ActivityNotFoundException e) {
+      Toast.makeText(VerifyIdentityActivity.this, R.string.VerifyIdentityActivity_no_app_to_share_to, Toast.LENGTH_LONG).show();
+    }
+  }
+
+
   public static class VerifyDisplayFragment extends Fragment implements Recipients.RecipientsModifiedListener {
 
     public static final String REMOTE_NUMBER   = "remote_number";
@@ -294,6 +329,21 @@ public class VerifyIdentityActivity extends PassphraseRequiredActionBarActivity
       this.clickListener = listener;
     }
 
+    public String getFormattedSafetyNumbers() {
+      StringBuilder result = new StringBuilder();
+
+      for (int i = 0; i < codes.length; i++) {
+        result.append(codes[i].getText());
+
+        if (i != codes.length - 1) {
+          if (((i+1) % 4) == 0) result.append('\n');
+          else                  result.append(' ');
+        }
+      }
+
+      return result.toString();
+    }
+
     private void setFingerprintViews(Fingerprint fingerprint) {
       String digits   = fingerprint.getDisplayableFingerprint().getDisplayText();
       int    partSize = digits.length() / codes.length;