fix(json-ot): 🐛 make compose() hand-crafted tests pass

Author: streamich

src/json-ot/types/ot-string/StringType.ts

@@ -144,9 +144,10 @@ export const apply = (str: string, op: StringTypeOp): string => {
 export const compose = (op1: StringTypeOp, op2: StringTypeOp): StringTypeOp => {
   const op3: StringTypeOp = [];
   const len1 = op1.length;
+  const len2 = op2.length;
   let off1 = 0;
   let i1 = 0;
-  for (let i2 = 0; i2 < op2.length; i2++) {
+  for (let i2 = 0; i2 < len2; i2++) {
     const comp2 = op2[i2];
     let doDelete = false;
     switch (typeof comp2) {
@@ -196,25 +197,31 @@ export const compose = (op1: StringTypeOp, op2: StringTypeOp): StringTypeOp => {
         const comp1 = i1 >= len1 ? remaining : op1[i1];
         const length1 = componentLength(comp1);
         const isDelete = idDeleteComponent(comp1);
-        if (remaining >= length1) {
-          i1++;
-          off1 = 0;
-          const end = off2 + length1;
-          if (isDelete) append(op3, copyComponent(comp1));
-          else {
+        if (remaining >= (length1 - off1)) {
+          if (isDelete) {
+            append(op3, copyComponent(comp1));
+            i1++;
+            off1 = 0;
+          } else {
+            const end = off2 + (length1 - off1);
             switch (typeof comp1) {
               case 'number': append(op3, isReversible ? [comp2[0].substring(off2, end)] : -length1); break;
-              case 'string': off2 += length1; break;
+              case 'string': {
+                off2 += (length1 - off1);
+                break;
+              }
             }
+            i1++;
+            off1 = 0;
+            off2 = end;
           }
-          if (!isDelete) off2 = end;
         } else {
           if (isDelete) {
-           append(op3, copyComponent(comp1));
+            append(op3, copyComponent(comp1));
           } else {
             switch (typeof comp1) {
               case 'number': append(op3, isReversible ? [comp2[0].substring(off2)] : -remaining); break;
-              case 'string': off2 += remaining; break;
+              // case 'string': break;
             }
           }
           off1 += remaining;

src/json-ot/types/ot-string/__tests__/StringOtFuzzer.ts

@@ -1,6 +1,6 @@
 import {RandomJson} from "../../../../json-random";
 import {Fuzzer} from "../../../../util/Fuzzer";
-import {append} from "../StringType";
+import {append, normalize} from "../StringType";
 import {StringTypeOp} from "../types";
 
 export class StringOtFuzzer extends Fuzzer {
@@ -10,7 +10,7 @@ export class StringOtFuzzer extends Fuzzer {
 
   genOp(str: string): StringTypeOp {
     if (!str) return [this.genString()];
-    const op: StringTypeOp = [];
+    let op: StringTypeOp = [];
     let off = 0;
     let remaining = str.length;
     while (remaining > 0) {
@@ -24,7 +24,7 @@ export class StringOtFuzzer extends Fuzzer {
           if (Math.random() < 0.5) {
             append(op, -len);
           } else {
-            append(op, [str.substr(off, len)]);
+            append(op, [str.substring(off, off + len)]);
           }
           off += len;
         },
@@ -35,6 +35,7 @@ export class StringOtFuzzer extends Fuzzer {
       fn();
       remaining = str.length - off;
     }
+    op = normalize(op);
     if (op.length === 1 && typeof op[0] === 'number' && op[0] > 0) return [this.genString()];
     return op;
   }

src/json-ot/types/ot-string/__tests__/StringType.spec.ts

@@ -104,6 +104,7 @@ describe('compose()', () => {
     ['insert in previous insert', 'aabb', [2, '1111'], [4, '22'], 'aa112211bb'],
     ['fuzzer bug #1', 'd6', ['}B'], [['}'], ';0q', 2, ['6']], ';0qBd'],
     ['fuzzer bug #2', 'Ai', [['A'], '#', -1], [-1], ''],
+    ['fuzzer bug #3', 'M}', ['!y1'], ["'/*s", 2, ',/@', -2, ['}']], "'/*s!y,/@"],
   ];
 
   describe('can compose', () => {