feat: add Tracker class

packages/core/src/Tracker.ts

@@ -0,0 +1,42 @@
+import { Transaction } from 'prosemirror-state'
+
+export interface TrackerResult {
+  position: number,
+  deleted: boolean,
+}
+
+export class Tracker {
+
+  transaction: Transaction
+
+  currentStep: number
+
+  constructor(transaction: Transaction) {
+    this.transaction = transaction
+    this.currentStep = this.transaction.steps.length
+  }
+
+  map(position: number): TrackerResult {
+    let deleted = false
+
+    const mappedPosition = this.transaction.steps
+      .slice(this.currentStep)
+      .reduce((newPosition, step) => {
+        const mapResult = step
+          .getMap()
+          .mapResult(newPosition)
+
+        if (mapResult.deleted) {
+          deleted = true
+        }
+
+        return mapResult.pos
+      }, position)
+
+    return {
+      position: mappedPosition,
+      deleted,
+    }
+  }
+
+}

packages/core/src/index.ts

@@ -3,6 +3,7 @@ export * from './Extension'
 export * from './Node'
 export * from './Mark'
 export * from './NodeView'
+export * from './Tracker'
 export * from './types'
 
 export { default as nodeInputRule } from './inputRules/nodeInputRule'