1 files changed, 18 insertions, 0 deletions
diff --git a/common/entities.js b/common/entities.js
index 60a7e2d..b70661f 100644
--- a/common/entities.js
+++ b/common/entities.js
@@ -54,6 +54,24 @@ const parse_version = ver_str => ver_str.split(".").map(n => parseInt(n));
  * No version normalization is performed.
  */
 const version_string = (ver, rev=0) => ver.join(".") + (rev ? `-${rev}` : "");
+#EXPORT version_string
+
+/*
+ * This function overloads on the number of arguments. If one argument is
+ * passed, it is an item definition (it need not be complete, only identifier,
+ * version and, if applicable, revision properties are relevant). If two or
+ * three arguments are given, they are in order: item identifier, item version
+ * and item revision.
+ * Returned is a string identifying this version of item.
+ */
+function item_id_string(...args) {
+    let def = args[0]
+    if (args.length > 1)
+	def = {identifier: args[0], version: args[1], revision: args[2]};
+    return !Array.isArray(def.version) ? def.identifier :
+	`${def.identifier}-${version_string(def.version, def.revision)}`;
+}
+#EXPORT item_id_string
 
 /* vers should be an array of comparable values. Return the greatest one. */
 const max = vals => Array.reduce(vals, (v1, v2) => v1 > v2 ? v1 : v2);