Return mapping of subscription id to unique display name.

Fallback 1: if display names are the same, use the last 4 digits of a
phone number
Fallback 2: if the phone number cannot be displayed or the last 4 digits
are identical, fallback to use the subscription id

This function depends on DeviceInfoUtils for the phone number
formatting. Because DeviceInfoUtils is within SettingsLib, this function
(at least for now) is located within the Settings codebase itself.

go/unique-sub-display-names

Bug: 148303118
Bug: 150370656
Test: atest -c SubscriptionUtilTest
Change-Id: Id3e26254d4b193c13506df52fb59e97643df7a32

src/com/android/settings/network/SubscriptionUtil.java

@@ -28,19 +28,25 @@ import android.telephony.SubscriptionInfo;
 import android.telephony.SubscriptionManager;
 import android.telephony.TelephonyManager;
 import android.telephony.UiccSlotInfo;
+import android.text.TextUtils;
 import android.util.Log;
 
 import androidx.annotation.VisibleForTesting;
 
 import com.android.settings.network.telephony.DeleteEuiccSubscriptionDialogActivity;
 import com.android.settings.network.telephony.ToggleSubscriptionDialogActivity;
+import com.android.settingslib.DeviceInfoUtils;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class SubscriptionUtil {
     private static final String TAG = "SubscriptionUtil";
@@ -214,6 +220,92 @@ public class SubscriptionUtil {
         return null;
     }
 
+    /**
+     * Return a mapping of active subscription ids to diaplay names. Each display name is
+     * guaranteed to be unique in the following manner:
+     * 1) If the original display name is not unique, the last four digits of the phone number
+     *    will be appended.
+     * 2) If the phone number is not visible or the last four digits are shared with another
+     *    subscription, the subscription id will be appended to the original display name.
+     * More details can be found at go/unique-sub-display-names.
+     *
+     * @return map of active subscription ids to diaplay names.
+     */
+    @VisibleForTesting
+    public static Map<Integer, CharSequence> getUniqueSubscriptionDisplayNames(Context context) {
+        class DisplayInfo {
+            public SubscriptionInfo subscriptionInfo;
+            public CharSequence originalName;
+            public CharSequence uniqueName;
+        }
+
+        final SubscriptionManager subscriptionManager =
+                context.getSystemService(SubscriptionManager.class);
+        // Map of SubscriptionId to DisplayName
+        final Supplier<Stream<DisplayInfo>> originalInfos =
+                () -> getActiveSubscriptions(subscriptionManager)
+                .stream()
+                .map(i -> {
+                    DisplayInfo info = new DisplayInfo();
+                    info.subscriptionInfo = i;
+                    info.originalName = i.getDisplayName();
+                    return info;
+                });
+
+        // TODO(goldmanj) consider using a map of DisplayName to SubscriptionInfos.
+        // A Unique set of display names
+        Set<CharSequence> uniqueNames = new HashSet<>();
+        // Return the set of duplicate names
+        final Set<CharSequence> duplicateOriginalNames = originalInfos.get()
+                .filter(info -> !uniqueNames.add(info.originalName))
+                .map(info -> info.originalName)
+                .collect(Collectors.toSet());
+
+        // If a display name is duplicate, append the final 4 digits of the phone number.
+        // Creates a mapping of Subscription id to original display name + phone number display name
+        final Supplier<Stream<DisplayInfo>> uniqueInfos = () -> originalInfos.get().map(info -> {
+            if (duplicateOriginalNames.contains(info.originalName)) {
+                // This may return null, if the user cannot view the phone number itself.
+                final String phoneNumber = DeviceInfoUtils.getBidiFormattedPhoneNumber(context,
+                        info.subscriptionInfo);
+                String lastFourDigits = "";
+                if (phoneNumber != null) {
+                    lastFourDigits = (phoneNumber.length() > 4)
+                        ? phoneNumber.substring(phoneNumber.length() - 4) : phoneNumber;
+                }
+
+                if (TextUtils.isEmpty(lastFourDigits)) {
+                    info.uniqueName = info.originalName;
+                } else {
+                    info.uniqueName = info.originalName + " " + lastFourDigits;
+                }
+
+            } else {
+                info.uniqueName = info.originalName;
+            }
+            return info;
+        });
+
+        // Check uniqueness a second time.
+        // We might not have had permission to view the phone numbers.
+        // There might also be multiple phone numbers whose last 4 digits the same.
+        uniqueNames.clear();
+        final Set<CharSequence> duplicatePhoneNames = uniqueInfos.get()
+                .filter(info -> !uniqueNames.add(info.uniqueName))
+                .map(info -> info.uniqueName)
+                .collect(Collectors.toSet());
+
+        return uniqueInfos.get().map(info -> {
+            if (duplicatePhoneNames.contains(info.uniqueName)) {
+                info.uniqueName = info.originalName + " "
+                        + info.subscriptionInfo.getSubscriptionId();
+            }
+            return info;
+        }).collect(Collectors.toMap(
+                info -> info.subscriptionInfo.getSubscriptionId(),
+                info -> info.uniqueName));
+    }
+
     public static String getDisplayName(SubscriptionInfo info) {
         final CharSequence name = info.getDisplayName();
         if (name != null) {