Added arn to the main repository

arn/HasLikes.go

@@ -0,0 +1,43 @@
+package arn
+
+// HasLikes implements common like and unlike methods.
+type hasLikes struct {
+	Likes []string `json:"likes"`
+}
+
+// Like makes the given user ID like the object.
+func (obj *hasLikes) Like(userID UserID) {
+	for _, id := range obj.Likes {
+		if id == userID {
+			return
+		}
+	}
+
+	obj.Likes = append(obj.Likes, userID)
+}
+
+// Unlike makes the given user ID unlike the object.
+func (obj *hasLikes) Unlike(userID UserID) {
+	for index, id := range obj.Likes {
+		if id == userID {
+			obj.Likes = append(obj.Likes[:index], obj.Likes[index+1:]...)
+			return
+		}
+	}
+}
+
+// LikedBy checks to see if the user has liked the object.
+func (obj *hasLikes) LikedBy(userID UserID) bool {
+	for _, id := range obj.Likes {
+		if id == userID {
+			return true
+		}
+	}
+
+	return false
+}
+
+// CountLikes returns the number of likes the object has received.
+func (obj *hasLikes) CountLikes() int {
+	return len(obj.Likes)
+}