Support add/remove objects from presets and tasks

lib/default-provisions.js

@@ -18,6 +18,7 @@
 
 const config = require("./config");
 const common = require("./common");
+const device = require("./device");
 
 const MAX_DEPTH = config.get("MAX_DEPTH");
 
@@ -79,9 +80,34 @@ function download(sessionData, provision, declarations, startRevision, endRevisi
 }
 
 
+function instances(sessionData, provision, declarations, startRevision, endRevision) {
+  let count = Number(provision[2]);
+
+  if (Number.isNaN(count))
+    return true;
+
+  let path = common.parsePath(provision[1]);
+
+  if (provision[2][0] === "+" || provision[2][0] === "-") {
+    declarations.push([path, 1]);
+
+    if (endRevision === startRevision)
+      return false;
+
+    let unpacked = device.unpack(sessionData.deviceData, path, startRevision + 1);
+    count = Math.max(0, unpacked.length + count);
+  }
+
+  declarations.push([path, 1, null, count]);
+
+  return true;
+}
+
+
 exports.refresh = refresh;
 exports.value = value;
 exports.tag = tag;
 exports.reboot = reboot;
 exports.reset = reset;
 exports.download = download;
+exports.instances = instances;