Add a ContentProvider so other apps can access (with permission) the openScale data.

This could be used for e.g. syncing weight logs to a third-party service such as Google Fit,
without the openScale app having to do so; with this, a 'connector' app could be written that
reads this data and does the push to a third-party service (or, indeed, an HTTP RPC connector,
an MQTT connector, SMS notifications, or anything else) without openScale needing this
functionality (or additional permissions).

android_app/app/src/main/AndroidManifest.xml

@@ -9,6 +9,15 @@
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
 
+    <!-- Permission to allow read of data from the database through a ContentProvider.
+         Marked "dangerous" so that explicit user approval is required to read this data, not
+         just the permission implied from installing the app from the Play Store. -->
+    <permission
+        android:name="com.health.openscale.READ_DATA"
+        android:description="@string/permission_read_data_description"
+        android:label="@string/permission_read_data_label"
+        android:protectionLevel="dangerous" />
+
     <uses-feature android:name="android.hardware.bluetooth_le" android:required="false"/>
 
     <application
@@ -59,6 +68,13 @@
                 android:name="android.support.FILE_PROVIDER_PATHS"
                 android:resource="@xml/file_provider_paths" />
         </provider>
+        <provider
+            android:name=".core.export.OpenScaleContentProvider"
+            android:authorities="com.health.openscale.provider"
+            android:enabled="true"
+            android:exported="true"
+            android:readPermission="com.health.openscale.READ_DATA">
+        </provider>
     </application>
 
 </manifest>

android_app/app/src/main/java/com/health/openscale/core/OpenScale.java

@@ -606,4 +606,19 @@ public class OpenScale {
             }
         }
     }
+
+    // As getScaleUserList(), but as a Cursor for export via a Content Provider.
+    public Cursor getScaleUserListCursor() {
+        return userDAO.selectAll();
+    }
+
+    // As getScaleUser(), but as a Cursor for export via a Content Provider.
+    public Cursor getScaleUserCursor(int userId) {
+        return userDAO.select(userId);
+    }
+
+    // As getScaleMeasurementList(), but as a Cursor for export via a Content Provider.
+    public Cursor getScaleMeasurementListCursor(int userId) {
+        return measurementDAO.selectAll(userId);
+    }
 }

android_app/app/src/main/java/com/health/openscale/core/database/ScaleMeasurementDAO.java

@@ -21,6 +21,7 @@ import android.arch.persistence.room.Insert;
 import android.arch.persistence.room.OnConflictStrategy;
 import android.arch.persistence.room.Query;
 import android.arch.persistence.room.Update;
+import android.database.Cursor;
 
 import com.health.openscale.core.datatypes.ScaleMeasurement;
 
@@ -64,4 +65,8 @@ public interface ScaleMeasurementDAO {
 
     @Query("DELETE FROM scaleMeasurements WHERE userId = :userId")
     void deleteAll(int userId);
+
+    // selectAll() is equivalent to getAll(), but returns a Cursor, for exposing via a ContentProvider.
+    @Query("SELECT * FROM scaleMeasurements WHERE userId = :userId AND enabled = 1 ORDER BY datetime DESC")
+    Cursor selectAll(int userId);
 }

android_app/app/src/main/java/com/health/openscale/core/database/ScaleUserDAO.java

@@ -21,6 +21,7 @@ import android.arch.persistence.room.Delete;
 import android.arch.persistence.room.Insert;
 import android.arch.persistence.room.Query;
 import android.arch.persistence.room.Update;
+import android.database.Cursor;
 
 import com.health.openscale.core.datatypes.ScaleUser;
 
@@ -45,4 +46,13 @@ public interface ScaleUserDAO {
 
     @Delete
     void delete(ScaleUser user);
+
+    // selectAll() and select() are equivalent to getall() and get(), but return a Cursor,
+    // for exposing via a ContentProvider.
+    @Query("SELECT * FROM scaleUsers")
+    Cursor selectAll();
+
+    @Query("SELECT * FROM scaleUsers WHERE id = :id")
+    Cursor select(int id);
+
 }

android_app/app/src/main/java/com/health/openscale/core/export/OpenScaleContentProvider.java

@@ -0,0 +1,129 @@
+/* Copyright (C) 2018 Paul Cowan <paul@custardsource.com>
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>
+ */package com.health.openscale.core.export;
+
+import android.content.ContentProvider;
+import android.content.ContentUris;
+import android.content.ContentValues;
+import android.content.Context;
+import android.content.UriMatcher;
+import android.database.Cursor;
+import android.net.Uri;
+import android.text.TextUtils;
+import android.util.Log;
+
+import com.health.openscale.core.OpenScale;
+
+/**
+ * Exposes the user and measurement data from openScale via
+ * <a href="https://developer.android.com/guide/topics/providers/content-providers">Android
+ * Content Providers</a>. This allows other apps to access the openScale data for their own purposes
+ * (e.g. syncing to third-party services like Google Fit, Fitbit API, etc) without openScale itself
+ * needing to do so or request additional permissions. <br />
+ *
+ * This access is gated by the com.health.openscale.READ_DATA permission, which is defined in the
+ * manifest; it is not accessible to any other app without user confirmation.<br />
+ *
+ * The following URIs are supported:
+ * <ul>
+ *     <li><code>content://com.health.openscale.provider/user</code>: list all users.</li>
+ *     <li><code>content://com.health.openscale.provider/user/$ID</code>: retrieve single user
+ *         by ID.</li>
+ *     <li><code>content://com.health.openscale.provider/user/$ID/measurements</code>:
+ *         retrieve all measurements for the supplied user ID.</li>
+ * </ul>
+ */
+public class OpenScaleContentProvider extends ContentProvider {
+    private static final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
+
+    private static final String AUTHORITY = "com.health.openscale.provider";
+
+    private static final int MATCH_TYPE_USER_LIST = 1;
+    private static final int MATCH_TYPE_USER_ENTRY = 2;
+    private static final int MATCH_TYPE_USER_MEASUREMENTS = 3;
+
+
+    static {
+        uriMatcher.addURI(AUTHORITY, "user", MATCH_TYPE_USER_LIST);
+        uriMatcher.addURI(AUTHORITY, "user/#", MATCH_TYPE_USER_ENTRY);
+        uriMatcher.addURI(AUTHORITY, "user/#/measurements", MATCH_TYPE_USER_MEASUREMENTS);
+    }
+
+    @Override
+    public String getType(Uri uri) {
+        switch (uriMatcher.match(uri)) {
+            case MATCH_TYPE_USER_LIST:
+                return "vnd.android.cursor.dir/vnd.com.health.openscale.provider.user";
+
+            case MATCH_TYPE_USER_ENTRY:
+                return "vnd.android.cursor.item/vnd.com.health.openscale.provider.user";
+
+            case MATCH_TYPE_USER_MEASUREMENTS:
+                return "vnd.android.cursor.item/vnd.com.health.openscale.provider.measurement";
+
+            default:
+                return null;
+        }
+    }
+
+    @Override
+    public boolean onCreate() {
+        return true;
+    }
+
+    @Override
+    public Cursor query(Uri uri, String[] projection, String selection,
+                        String[] selectionArgs, String sortOrder) {
+        final Context context = getContext();
+        Cursor cursor;
+
+        switch (uriMatcher.match(uri)) {
+            case MATCH_TYPE_USER_LIST:
+                cursor = OpenScale.getInstance().getScaleUserListCursor();
+                break;
+
+            case MATCH_TYPE_USER_ENTRY:
+                cursor = OpenScale.getInstance().getScaleUserCursor(Integer.valueOf(uri.getPathSegments().get(1)));
+                break;
+
+            case MATCH_TYPE_USER_MEASUREMENTS:
+                cursor = OpenScale.getInstance().getScaleMeasurementListCursor(Integer.valueOf(uri.getPathSegments().get(1)));
+                break;
+
+            default:
+                throw new IllegalArgumentException("Unknown URI: " + uri);
+        }
+
+        cursor.setNotificationUri(context.getContentResolver(), uri);
+        return cursor;
+    }
+
+
+    @Override
+    public int delete(Uri uri, String selection, String[] selectionArgs) {
+        throw new UnsupportedOperationException("Not yet implemented");
+    }
+
+    @Override
+    public Uri insert(Uri uri, ContentValues values) {
+        throw new UnsupportedOperationException("Not yet implemented");
+    }
+
+    @Override
+    public int update(Uri uri, ContentValues values, String selection,
+                      String[] selectionArgs) {
+        throw new UnsupportedOperationException("Not yet implemented");
+    }
+}

android_app/app/src/main/res/values/strings.xml

@@ -190,6 +190,8 @@
     <string name="permission_not_granted">Permission not granted</string>
     <string name="permission_bluetooth_info">Coarse location permission needed to search for Bluetooth devices. It can be revoked after the device is found.</string>
     <string name="permission_bluetooth_info_title">Info</string>
+    <string name="permission_read_data_description">read openScale data, including user information and all saved measurements</string>
+    <string name="permission_read_data_label">Read openScale Data</string>
     <string name="label_next">Next</string>
     <string name="label_long_press_drag_reorder">Long press and drag measurement to reorder</string>
     <string name="label_click_measurement_configure">Click measurement to configure</string>