Don't blow up if OSX database is missing data table

lib/desktop.rb

@@ -1,5 +1,6 @@
 require 'desktop/cli'
 require 'desktop/local_image'
-require 'desktop/osx'
 require 'desktop/version'
 require 'desktop/web_image'
+
+require 'desktop/osx/osx'

lib/desktop/osx/database.rb

@@ -0,0 +1,42 @@
+require 'sqlite3'
+
+module Desktop
+  class OSX
+    class Database
+      attr_reader :connection
+
+      def initialize(connection = nil)
+        @connection = connection || default_connection
+      end
+
+      def clear_desktop_image
+        clear_data if data?
+      end
+
+      def close
+        connection.close
+      end
+
+      private
+
+      def data?
+        connection.execute(
+          "SELECT name FROM sqlite_master WHERE type='table' AND name='data'"
+        ).any?
+      end
+
+      def clear_data
+        connection.execute 'DELETE FROM data'
+        connection.execute 'VACUUM data'
+      end
+
+      def default_connection
+        SQLite3::Database.new path
+      end
+
+      def path
+        File.expand_path '~/Library/Application Support/Dock/desktoppicture.db'
+      end
+    end
+  end
+end

lib/desktop/osx.rb → lib/desktop/osx/osx.rb

@@ -1,4 +1,4 @@
-require 'sqlite3'
+require 'desktop/osx/database'
 
 module Desktop
   class OSX
@@ -58,9 +58,8 @@ def write_default_desktop(image)
     end
 
     def clear_custom_desktop_image
-      db = SQLite3::Database.new(desktop_image_db_path)
-      db.execute 'DELETE FROM data'
-      db.execute 'VACUUM data'
+      db = Database.new
+      db.clear_desktop_image
       db.close
     end
 
@@ -71,9 +70,5 @@ def reload_desktop
     def default_desktop_image_path
       '/System/Library/CoreServices/DefaultDesktop.jpg'
     end
-
-    def desktop_image_db_path
-      File.expand_path '~/Library/Application Support/Dock/desktoppicture.db'
-    end
   end
 end

test/desktop/osx/database_test.rb

@@ -0,0 +1,38 @@
+require 'test_helper'
+require 'desktop/osx/database'
+
+module Desktop
+  describe OSX::Database do
+    def with_connection
+      connection = SQLite3::Database.new ':memory:'
+      yield connection
+    ensure
+      connection.close
+    end
+
+    describe '#clear_desktop_image' do
+      it 'clears contents of data table' do
+        with_connection do |connection|
+          connection.execute("CREATE TABLE data (FileName STRING)")
+          connection.execute("INSERT INTO data VALUES ('mydesktop.png')")
+
+          refute_empty connection.execute("SELECT * FROM data")
+
+          OSX::Database.new(connection).clear_desktop_image
+
+          assert_empty connection.execute("SELECT * FROM data")
+        end
+      end
+
+      it 'does not blow up if data table does not exist' do
+        with_connection do |connection|
+          assert_empty connection.execute(
+            "SELECT name FROM sqlite_master WHERE type='table' AND name='data'"
+          )
+
+          OSX::Database.new(connection).clear_desktop_image
+        end
+      end
+    end
+  end
+end

test/desktop/osx_test.rb → test/desktop/osx/osx_test.rb

@@ -1,5 +1,5 @@
 require 'test_helper'
-require 'desktop/osx'
+require 'desktop/osx/osx'
 require 'desktop/local_image'
 
 module Desktop