feat: 🎸 implement Log.clone() method

Author: streamich

src/json-crdt/log/Log.ts

@@ -2,6 +2,7 @@ import {AvlMap} from 'sonic-forest/lib/avl/AvlMap';
 import {first, next, prev} from 'sonic-forest/lib/util';
 import {printTree} from 'tree-dump/lib/printTree';
 import {listToUint8} from '@jsonjoy.com/util/lib/buffers/concat';
+import {cloneBinary} from '@jsonjoy.com/util/lib/json-clone/cloneBinary';
 import {Model} from '../model';
 import {toSchema} from '../schema/toSchema';
 import {
@@ -198,6 +199,23 @@ export class Log<N extends JsonNode = JsonNode<any>, Metadata extends Record<str
     };
   }
 
+  /**
+   * Finds the latest patch for a given session ID.
+   *
+   * @param sid Session ID to find the latest patch for.
+   * @return The latest patch for the given session ID, or `undefined` if no
+   *     such patch exists.
+   */
+  public findMax(sid: number): Patch | undefined {
+    let curr = this.patches.max;
+    while (curr) {
+      if (curr.k.sid === sid) return curr.v;
+      curr = prev(curr);
+    }
+    return;
+  }
+
+
   /**
    * Creates a patch which reverts the given patch. The RGA insertion operations
    * are reversed just by deleting the inserted values. All other operations

src/json-crdt/log/__tests__/Log.spec.ts

@@ -1,3 +1,4 @@
+import {deepEqual} from '@jsonjoy.com/util/lib/json-equal/deepEqual';
 import {type DelOp, type InsStrOp, s} from '../../../json-crdt-patch';
 import {Model} from '../../model';
 import {Log} from '../Log';
@@ -143,6 +144,89 @@ describe('.findMax()', () => {
   });
 });
 
+describe('.clone()', () => {
+  const setup = () => {
+    const model = Model.create({foo: 'bar'});
+    const log1 = Log.fromNewModel(model);
+    log1.metadata = {time: 123};
+    log1.end.api.obj([]).set({x: 1});
+    log1.end.api.flush();
+    log1.end.api.obj([]).set({y: 2});
+    log1.end.api.flush();
+    log1.end.api.obj([]).set({foo: 'baz'});
+    log1.end.api.flush();
+    const log2 = log1.clone();
+    return {log1, log2};
+  };
+
+  test('start model has the same view and clock', () => {
+    const {log1, log2} = setup();
+    expect(log1.start()).not.toBe(log2.start());
+    expect(deepEqual(log1.start().view(), log2.start().view())).toBe(true);
+    expect(log1.start().clock.sid).toEqual(log2.start().clock.sid);
+    expect(log1.start().clock.time).toEqual(log2.start().clock.time);
+  });
+
+  test('end model has the same view and clock', () => {
+    const {log1, log2} = setup();
+    expect(log1.end).not.toBe(log2.end);
+    expect(deepEqual(log1.end.view(), log2.end.view())).toBe(true);
+    expect(log1.end.clock.sid).toEqual(log2.end.clock.sid);
+    expect(log1.end.clock.time).toEqual(log2.end.clock.time);
+  });
+
+  test('metadata is the same but has different identity', () => {
+    const {log1, log2} = setup();
+    expect(log1.metadata).not.toBe(log2.metadata);
+    expect(deepEqual(log1.metadata, log2.metadata)).toBe(true);
+  });
+
+  test('patch log is the same', () => {
+    const {log1, log2} = setup();
+    expect(log1.patches.size()).toBe(log2.patches.size());
+    expect(log1.patches.min!.v.toBinary()).toEqual(log2.patches.min!.v.toBinary());
+    expect(log1.patches.max!.v.toBinary()).toEqual(log2.patches.max!.v.toBinary());
+    expect(log1.patches.min!.v).not.toBe(log2.patches.min!.v);
+    expect(log1.patches.max!.v).not.toBe(log2.patches.max!.v);
+  });
+
+  test('can evolve logs independently', () => {
+    const {log1, log2} = setup();
+    log1.end.api.obj([]).set({a: 1});
+    log1.end.api.flush();
+    expect(log1.end.view()).toEqual({foo: 'baz', x: 1, y: 2, a: 1});
+    expect(log2.end.view()).toEqual({foo: 'baz', x: 1, y: 2});
+    log2.end.api.obj([]).set({b: 2});
+    log2.end.api.flush();
+    expect(log1.end.view()).toEqual({foo: 'baz', x: 1, y: 2, a: 1});
+    expect(log2.end.view()).toEqual({foo: 'baz', x: 1, y: 2, b: 2});
+  });
+});
+
+describe('.rebase()', () => {
+  test('can advance the log from start', () => {
+    const model = Model.create();
+    const sid0 = model.clock.sid;
+    const sid1 = Model.sid();
+    model.api.set({foo: 'bar'});
+    const log = Log.fromNewModel(model);
+    log.end.api.obj([]).set({x: 1});
+    const patch1 = log.end.api.flush();
+    log.end.setSid(sid1);
+    log.end.api.obj([]).set({y: 2});
+    const patch2 = log.end.api.flush();
+    log.end.setSid(sid0);
+    log.end.api.obj([]).set({foo: 'baz'});
+    const patch3 = log.end.api.flush();
+    const found0 = log.findMax(sid0);
+    const found1 = log.findMax(sid1);
+    const found2 = log.findMax(12345);
+    expect(found0).toBe(patch3);
+    expect(found1).toBe(patch2);
+    expect(found2).toBe(void 0);
+  });
+});
+
 describe('.undo()', () => {
   describe('RGA', () => {
     describe('str', () => {