Presence Fail

.gitignore

@@ -1,3 +1,4 @@
 *.swp
 *.DS_Store
 node_modules
+package-lock.json

README.md

@@ -2,6 +2,42 @@
 
 The JSON OT type can be used to edit arbitrary JSON documents.
 
+It has been forked from https://github.com/ottypes/json0 and modified to add Presence.
+
+## Presence
+
+(inspired by https://github.com/Teamwork/ot-rich-text#presence)
+
+The shape of our presence data is as follows:
+
+```
+{
+    u: '123', // user ID
+    c: 8, // number of changes made by this user
+    s: [ // list of selections
+        [ 1, 1 ], // collapsed selection
+        [ 5, 7 ], // forward selection
+        [ 9, 4 ] // backward selection
+    ]
+}
+```
+
+Each selection listed in `s` ends with a 2-element array containing the selection start index and the selection end index. The elements in the array preceeding the last two represent the path of a `text0` entry within the `json0` data structure.
+
+For example, the following entry in the `s` array represents the user's cursor position within the `content` field (`data.content`):
+
+```
+['content', 2, 2]
+```
+
+We can access deeply nested entries with this structure as well. For example, the following `s` entry represents a text selection in `data.files[3].text`:
+
+```
+['files', 3, 'text', 4, 7]
+```
+
+The rest of the README content is from the original repo https://github.com/ottypes/json0.
+
 ## Features
 
 The JSON OT type supports the following operations:

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": {
@@ -9,15 +9,14 @@
   "dependencies": {},
   "devDependencies": {
     "ot-fuzzer": "^1.0.0",
-    "mocha": "^1.20.1",
-    "coffee-script": "^1.7.1"
+    "mocha": "^1.20.1"
   },
   "scripts": {
     "test": "mocha"
   },
   "repository": {
     "type": "git",
-    "url": "git://github.com/ottypes/json0"
+    "url": "git://github.com/houshuang/json0"
   },
   "keywords": [
     "ot",