diff --git a/devtools/hackdoc/source/source.go b/devtools/hackdoc/source/source.go
new file mode 100644
index 0000000..a79a920
--- /dev/null
+++ b/devtools/hackdoc/source/source.go
@@ -0,0 +1,10 @@
+package source
+
+type Source interface {
+	IsFile(path string) (bool, error)
+	ReadFile(path string) ([]byte, error)
+	IsDirectory(path string) (bool, error)
+
+	CacheSet(dependencies []string, key string, value interface{})
+	CacheGet(key string) interface{}
+}