Adding presence to ot-json0

lib/json0.js

@@ -133,6 +133,63 @@ function convertToText(c) {
   delete c.o;
 }
 
+// not checking anything here, we should probably check that u: exists
+// (only thing we care about at json0 top level), and then delegate
+// to any subtypes if there is already subtype presence data
+json.createPresence = function(presence) {
+  return presence;
+};
+
+// this needs more thinking/testing, looking a bit more carefully at
+// how this is implemented in ot-rich-text, etc.
+json.comparePresence = function(pres1, pres2) {
+  if (!pres1 || !pres2) {
+    return false;
+  }
+  if (!pres1.p || !pres2.p) {
+    return false;
+  }
+  if (pres1.t !== pres2.t) {
+    return false;
+  }
+  if (pres1.t && subtypes[pres1.t]) {
+    if (pres1.p[0] === pres2.p[0]) {
+      return subtypes[pres1.t].comparePresence(pres1, pres2);
+    }
+  } else return pres1 === pres2;
+};
+
+// this is the key function, always run client-side, both on
+// the client that creates a text-change, and on the clients
+// that receive text-changes (ops). if there are no ops, just
+// return presence, if there are ops, delegate to the subtype
+// responsible for those ops (currently only ot-rich-text).
+// I am making assumptions many places that all ops will be
+// of the same subtype, not sure if this is a given.
+// We're only concerned about the first level of object/array,
+// not sure if the spec allows nesting of subtypes.
+json.transformPresence = function(presence, op, isOwn) {
+  if (op.length < 1) {
+    return presence;
+  }
+  const representativeOp = op[0];
+  const opType = op[0].t;
+  const path = representativeOp.p && representativeOp.p[0]
+  if (opType && subtypes[opType] && path) {
+    if (!presence.p || !presence.p[0] || presence.p[0] !== path) {
+      return presence
+    }
+    // return result of running the subtype's transformPresence,
+    // but add path and type, which the subtype will not include
+    presence = {
+      ...subtypes[opType].transformPresence(presence, op, isOwn),
+      p: op[0].p,
+      t: op[0].t
+    };
+  }
+  return presence;
+};
+
 json.apply = function(snapshot, op) {
   json.checkValidOp(op);
 

package.json

@@ -1,6 +1,6 @@
 {
-  "name": "ot-json0",
-  "version": "1.1.0",
+  "name": "@houshuang/ot-json0",
+  "version": "1.2.0",
   "description": "JSON OT type",
   "main": "lib/index.js",
   "directories": {
@@ -17,7 +17,7 @@
   },
   "repository": {
     "type": "git",
-    "url": "git://github.com/ottypes/json0"
+    "url": "git://github.com/houshuang/json0"
   },
   "keywords": [
     "ot",