Uncompress and unprefix fetch multi (#15)

* Uncompress and unprefix fetch multi

* Pass source key to the block

lib/rails-brotli-cache/store.rb

@@ -115,8 +115,10 @@ def fetch_multi(*names)
       @core_store.fetch_multi(
         *names, options.merge(compress: false)
       ) do |name|
-        compressed(yield(name), options)
-      end
+        compressed(yield(source_cache_key(name)), options)
+      end.map do |key, val|
+        [source_cache_key(key), uncompressed(val, options)]
+      end.to_h
     end
 
     def exist?(name, options = {})

spec/rails-brotli-cache/store_spec.rb

@@ -98,9 +98,22 @@ def to_param
   end
 
   describe "fetch_multi" do
+    subject do
+      cache_store.fetch_multi(*keys) do |key|
+        big_enough_to_compress_value + key
+      end
+    end
+
+    let(:keys) { %w[key_1 key_2] }
+    let(:response) do
+      {
+        'key_1' => big_enough_to_compress_value + 'key_1',
+        'key_2' => big_enough_to_compress_value + 'key_2'
+      }
+    end
+
     it "works" do
-      cache_store.fetch_multi("key_1", "key_2", expires_in: 5.seconds) { big_enough_to_compress_value }
-      expect(cache_store.read("key_1")).to eq big_enough_to_compress_value
+      expect(subject).to eq response
     end
   end