Proposal – Add support for presences

lib/json1.ts

@@ -20,8 +20,8 @@
 // import log from './log'
 import deepEqual from './deepEqual.js'
 import deepClone from './deepClone.js'
-import {ReadCursor, WriteCursor, readCursor, writeCursor, advancer, eachChildOf, isValidPathItem} from './cursor.js'
-import { Doc, JSONOpComponent, Path, Key, JSONOp, JSONOpList, Conflict, ConflictType } from './types.js'
+import { ReadCursor, WriteCursor, readCursor, writeCursor, advancer, eachChildOf, isValidPathItem } from './cursor.js'
+import { Doc, JSONOpComponent, Path, Presence, Key, JSONOp, JSONOpList, Conflict, ConflictType } from './types.js'
 
 const RELEASE_MODE = process.env.JSON1_RELEASE_MODE
 const log: (...args: any) => void = RELEASE_MODE ? (() => {}) : require('./log').default
@@ -57,6 +57,7 @@ export const type = {
 
   apply,
   transformPosition,
+  transformPresence,
   compose,
   tryTransform,
   transform,
@@ -688,7 +689,11 @@ function transformPosition(path: Path, op: JSONOp): Path | null {
       if (et) {
         const e = getEdit(c!)
         log('Embedded edit', e, et)
-        if (et.transformPosition) path[i] = et.transformPosition(path[i], e)
+        if (et.transformPosition) {
+            path[i] = et.transformPosition(path[i], e)
+        } else if (et.transformCursor) {
+            path[i] = et.transformCursor(path[i], e)
+        }
         // Its invalid for the operation to have drops inside the embedded edit here.
         break
       }
@@ -721,6 +726,25 @@ function transformPosition(path: Path, op: JSONOp): Path | null {
   return path
 }
 
+function transformPresence(presence: Presence | null, op: JSONOp, isOwnOperation: boolean): Presence | null {
+    if (!presence || !presence.start || !presence.end) {
+        return null
+    }
+
+    const start = transformPosition(presence.start, op)
+    const end = transformPosition(presence.end, op)
+
+    if (start && end) {
+        return { ...presence, start, end }
+    } else if (start) {
+        return { ...presence, start, end: start }
+    } else if (end) {
+        return { ...presence, start: end, end }
+    }
+
+    return null
+}
+
 
 // ****** Compose
 

lib/types.ts

@@ -57,6 +57,11 @@ export type JSONOp = null | JSONOpList
 
 export type Key = number | string
 export type Path = Key[]
+export type Presence = {
+    start: Path,
+    end: Path,
+    [key: string]: any
+}
 
 /**
  * JSON documents must be able to round-trip through JSON.stringify /

package.json

@@ -12,6 +12,7 @@
     "mocha": "^7.1.1",
     "ot-fuzzer": "1.3",
     "ot-simple": "^1.0.0",
+    "rich-text": "^4.1.0",
     "terser": "^4.6.7",
     "typescript": "^3.9.5"
   },

test/presence.js

@@ -0,0 +1,95 @@
+const assert = require("assert");
+const Delta = require("quill-delta");
+const { type } = require("../dist/json1.release");
+
+type.registerSubtype(require("rich-text"));
+
+describe("presences", () => {
+  it("transforms json1 only presences", () => {
+    const op = ["z", 0, { i: "hello" }];
+    const presenceBefore = { start: ["z", 0], end: ["z", 1] };
+    const presenceAfter = { start: ["z", 1], end: ["z", 2] };
+
+    assert.deepStrictEqual(
+      type.transformPresence(presenceBefore, op),
+      presenceAfter
+    );
+  });
+
+  it("transforms json1 + text-unicode presences", () => {
+    const op = ["z", [0, { i: "hello" }], [2, { es: ["hi"] }]];
+    const presenceBefore = { start: ["z", 1, 1], end: ["z", 2, 0] };
+    const presenceAfter = { start: ["z", 2, 3], end: ["z", 3, 0] };
+
+    assert.deepStrictEqual(
+      type.transformPresence(presenceBefore, op),
+      presenceAfter
+    );
+  });
+
+  it("transforms json1 + rich-text presences", () => {
+    const op = [
+      "z",
+      [0, { i: "hello" }],
+      [4, { et: "rich-text", e: new Delta([{ insert: "bye" }]) }],
+    ];
+    const presenceBefore = { start: ["z", 3, 1], end: ["z", 4, 0] };
+    const presenceAfter = { start: ["z", 4, 4], end: ["z", 5, 0] };
+
+    assert.deepStrictEqual(
+      type.transformPresence(presenceBefore, op),
+      presenceAfter
+    );
+  });
+
+  it("does nothing on null presences", () => {
+    const op = ["z", 0, { i: "hello" }];
+
+    assert.deepStrictEqual(type.transformPresence(null, op), null);
+  });
+
+  it("returns null on missing start or end", () => {
+    const op = ["z", 0, { i: "hello" }];
+
+    assert.deepStrictEqual(
+      type.transformPresence({ start: null, end: [] }, op),
+      null
+    );
+
+    assert.deepStrictEqual(
+      type.transformPresence({ start: [], end: null }, op),
+      null
+    );
+  });
+
+  it("returns collapsed presence when start container is removed", () => {
+    const op = ["z", 0, { r: true }];
+    const presenceBefore = { start: ["z", 0], end: ["z", 1] };
+    const presenceAfter = { start: ["z", 0], end: ["z", 0] };
+
+    assert.deepStrictEqual(
+      type.transformPresence(presenceBefore, op),
+      presenceAfter
+    );
+  });
+
+  it("returns collapsed presence when end container is removed", () => {
+    const op = ["z", 1, { r: true }];
+    const presenceBefore = { start: ["z", 0], end: ["z", 1] };
+    const presenceAfter = { start: ["z", 0], end: ["z", 0] };
+
+    assert.deepStrictEqual(
+      type.transformPresence(presenceBefore, op),
+      presenceAfter
+    );
+  });
+
+  it("allows arbitrary data in presences", () => {
+    const op = ["z", 0, { i: "hello" }];
+    const data = { user: "John Doe", color: "blue" };
+    const presenceBefore = { start: ["z", 0], end: ["z", 1], data };
+    const presenceAfter = type.transformPresence(presenceBefore, op);
+
+    assert.ok(presenceBefore.data === presenceAfter.data);
+  });
+});

yarn.lock

@@ -217,6 +217,11 @@ esprima@^4.0.0:
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-4.0.1.tgz#13b04cdb3e6c5d19df91ab6987a8695619b0aa71"
   integrity sha512-eGuFFw7Upda+g4p+QHvnW0RyTX/SVeJBDM/gCtMARO0cLuT2HcEKnTPvhjV6aGeqrCB/sbNop0Kszm0jsaWU4A==
 
+[email protected]:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/fast-diff/-/fast-diff-1.2.0.tgz#73ee11982d86caaf7959828d519cfe927fac5f03"
+  integrity sha512-xJuoT5+L99XlZ8twedaRf6Ax2TgQVxvgZOYoPKqZufmJib0tL2tegPBOZb1pVNgIhlqDlA0eO0c3wBvQcmzx4w==
+
 fill-range@^7.0.1:
   version "7.0.1"
   resolved "https://registry.yarnpkg.com/fill-range/-/fill-range-7.0.1.tgz#1919a6a7c75fe38b2c7c77e5198535da9acdda40"
@@ -396,6 +401,16 @@ locate-path@^3.0.0:
     p-locate "^3.0.0"
     path-exists "^3.0.0"
 
+lodash.clonedeep@^4.5.0:
+  version "4.5.0"
+  resolved "https://registry.yarnpkg.com/lodash.clonedeep/-/lodash.clonedeep-4.5.0.tgz#e23f3f9c4f8fbdde872529c1071857a086e5ccef"
+  integrity sha1-4j8/nE+Pvd6HJSnBBxhXoIblzO8=
+
+lodash.isequal@^4.5.0:
+  version "4.5.0"
+  resolved "https://registry.yarnpkg.com/lodash.isequal/-/lodash.isequal-4.5.0.tgz#415c4478f2bcc30120c22ce10ed3226f7d3e18e0"
+  integrity sha1-QVxEePK8wwEgwizhDtMib30+GOA=
+
 lodash@^4.17.15:
   version "4.17.19"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.19.tgz#e48ddedbe30b3321783c5b4301fbd353bc1e4a4b"
@@ -569,6 +584,15 @@ picomatch@^2.0.4:
   resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.2.2.tgz#21f333e9b6b8eaff02468f5146ea406d345f4dad"
   integrity sha512-q0M/9eZHzmr0AulXyPwNfZjtwZ/RBZlbN3K3CErVrk50T2ASYI7Bye0EvekFY3IP1Nt2DHu0re+V2ZHIpMkuWg==
 
+quill-delta@^4.2.1:
+  version "4.2.2"
+  resolved "https://registry.yarnpkg.com/quill-delta/-/quill-delta-4.2.2.tgz#015397d046e0a3bed087cd8a51f98c11a1b8f351"
+  integrity sha512-qjbn82b/yJzOjstBgkhtBjN2TNK+ZHP/BgUQO+j6bRhWQQdmj2lH6hXG7+nwwLF41Xgn//7/83lxs9n2BkTtTg==
+  dependencies:
+    fast-diff "1.2.0"
+    lodash.clonedeep "^4.5.0"
+    lodash.isequal "^4.5.0"
+
 readdirp@~3.2.0:
   version "3.2.0"
   resolved "https://registry.yarnpkg.com/readdirp/-/readdirp-3.2.0.tgz#c30c33352b12c96dfb4b895421a49fd5a9593839"
@@ -586,6 +610,13 @@ require-main-filename@^2.0.0:
   resolved "https://registry.yarnpkg.com/require-main-filename/-/require-main-filename-2.0.0.tgz#d0b329ecc7cc0f61649f62215be69af54aa8989b"
   integrity sha512-NKN5kMDylKuldxYLSUfrbo5Tuzh4hd+2E8NPPX02mZtn1VuREQToYe/ZdlJy+J3uCpfaiGF05e7B8W0iXbQHmg==
 
+rich-text@^4.1.0:
+  version "4.1.0"
+  resolved "https://registry.yarnpkg.com/rich-text/-/rich-text-4.1.0.tgz#8b4c0e48a84fbb535dd692998f1e39eaaf0451a8"
+  integrity sha512-zQg80us6AfopS7s2YPsU+jfLX1RJaOdd6w26Jz4Al1G73AMzqDLTIZSnr0I7HTdCIU1gcGSMDlhq2v4IfoKfbg==
+  dependencies:
+    quill-delta "^4.2.1"
+
 seedrandom@^2.4.4:
   version "2.4.4"
   resolved "https://registry.yarnpkg.com/seedrandom/-/seedrandom-2.4.4.tgz#b25ea98632c73e45f58b77cfaa931678df01f9ba"