more type fixes and rethinking writeStructs

src/utils/ID.js

@@ -4,6 +4,8 @@
 
 import * as decoding from 'lib0/decoding.js'
 import * as encoding from 'lib0/encoding.js'
+import * as error from 'lib0/error.js'
+import { AbstractType } from '../types/AbstractType.js' // eslint-disable-line
 
 export class ID {
   /**
@@ -46,14 +48,19 @@ export class ID {
   }
 }
 
+/**
+ * @param {ID} a
+ * @param {ID} b
+ * @return {boolean}
+ */
+export const compareIDs = (a, b) => a === b || (a !== null && b !== null && a.client === b.client && a.clock === b.clock)
+
 /**
  * @param {number} client
  * @param {number} clock
  */
 export const createID = (client, clock) => new ID(client, clock)
 
-const isNullID = 0xFFFFFF
-
 /**
  * @param {encoding.Encoder} encoder
  * @param {ID} id
@@ -63,21 +70,31 @@ export const writeID = (encoder, id) => {
   encoding.writeVarUint(encoder, id.clock)
 }
 
-/**
- * @param {encoding.Encoder} encoder
- */
-export const writeNullID = (encoder) =>
-  encoding.writeVarUint(encoder, isNullID)
-
 /**
  * Read ID.
  * * If first varUint read is 0xFFFFFF a RootID is returned.
  * * Otherwise an ID is returned
  *
  * @param {decoding.Decoder} decoder
- * @return {ID | null}
+ * @return {ID}
  */
-export const readID = decoder => {
-  const client = decoding.readVarUint(decoder)
-  return client === isNullID ? null : createID(client, decoding.readVarUint(decoder))
+export const readID = decoder =>
+  createID(decoding.readVarUint(decoder), decoding.readVarUint(decoder))
+
+/**
+ * The top types are mapped from y.share.get(keyname) => type.
+ * `type` does not store any information about the `keyname`.
+ * This function finds the correct `keyname` for `type` and throws otherwise.
+ *
+ * @param {AbstractType} type
+ * @return {string}
+ */
+export const findRootTypeKey = type => {
+  // @ts-ignore _y must be defined, otherwise unexpected case
+  for (let [key, value] of type._y.share) {
+    if (value === type) {
+      return key
+    }
+  }
+  throw error.unexpectedCase()
 }