implement RESET_OWNERS command for editable metadata

lib/metadata.js

@@ -15,9 +15,13 @@ var commands = {};
 
 // ["ADD_OWNERS", ["7eEqelGso3EBr5jHlei6av4r9w2B9XZiGGwA1EgZ-5I="], 1561623438989]
 commands.ADD_OWNERS = function (meta, args) {
+    // bail out if args isn't an array
     if (!Array.isArray(args)) {
         throw new Error('METADATA_INVALID_OWNERS');
     }
+
+    // you shouldn't be able to get here if there are no owners
+    // because only an owner should be able to change the owners
     if (!Array.isArray(meta.owners)) {
         throw new Error("METADATA_NONSENSE_OWNERS");
     }
@@ -30,19 +34,39 @@ commands.ADD_OWNERS = function (meta, args) {
 
 // ["RM_OWNERS", ["CrufexqXcY-z+eKJlEbNELVy5Sb7E-EAAEFI8GnEtZ0="], 1561623439989]
 commands.RM_OWNERS = function (meta, args) {
+    // what are you doing if you don't have owners to remove?
     if (!Array.isArray(args)) {
         throw new Error('METADATA_INVALID_OWNERS');
     }
+    // if there aren't any owners to start, this is also pointless
     if (!Array.isArray(meta.owners)) {
         throw new Error("METADATA_NONSENSE_OWNERS");
     }
 
+    // remove owners one by one
+    // we assume there are no duplicates
     args.forEach(function (owner) {
         var index = meta.owners.indexOf(owner);
+        if (index < 0) { return; }
         meta.owners.splice(index, 1);
     });
 };
 
+// ["RESET_OWNERS", ["7eEqelGso3EBr5jHlei6av4r9w2B9XZiGGwA1EgZ-5I="], 1561623439989]
+commands.RESET_OWNERS = function (meta, args) {
+    // expect a new array, even if it's empty
+    if (!Array.isArray(args)) {
+        throw new Error('METADATA_INVALID_OWNERS');
+    }
+    // assume there are owners to start
+    if (!Array.isArray(meta.owners)) {
+        throw new Error("METADATA_NONSENSE_OWNERS");
+    }
+
+    // overwrite the existing owners with the new one
+    meta.owners = args;
+};
+
 commands.UPDATE_EXPIRATION = function () {
 
 };