modify useStickyState to allow for retrieving and modifying the saved state on initialization

src/components/phrase-builder/PhraseBuilder.tsx

@@ -1,4 +1,3 @@
-import { useState } from "react";
 import NPPicker from "../np-picker/NPPicker";
 import VerbPicker from "../VerbPicker";
 import TensePicker from "../TensePicker";
@@ -38,8 +37,12 @@ export function PhraseBuilder(props: {
 }) {
     const [subject, setSubject] = useStickyState<NPSelection | undefined>(undefined, "subjectNPSelection");
     const [mode, setMode] = useStickyState<"charts" | "phrases">("phrases", "verbExplorerMode");
-    const [verb, setVerb] = useState<VerbSelection | undefined>(
-        props.verb ? makeVerbSelection(props.verb, setSubject, undefined) : undefined,
+    const passedVerb = props.verb;
+    const [verb, setVerb] = useStickyState<VerbSelection | undefined>(
+        passedVerb
+            ? (old) => makeVerbSelection(passedVerb, setSubject, old)
+            : undefined,
+        "verbExplorerVerb",
     );
     const textOpts = props.opts || defaultTextOptions;
     function handleSubjectChange(subject: NPSelection | undefined, skipPronounConflictCheck?: boolean) {

src/useStickyState.ts

@@ -1,18 +1,42 @@
 import { useEffect, useState } from "react";
 
-export default function useStickyState<T>(defaultValue: T, key: string): [
+/**
+ * replacement from the React useState hook that will persist the state in local storage
+ * 
+ * @param defaultValue The default value to use if there was nothing saved previously OR
+ * a function that will take the saved value and return a modified new value to start with
+ * @param key a key for saving the state in locolStorage
+ * @returns 
+ */
+export default function useStickyState<T extends string | object | boolean | undefined | null>(
+  defaultValue: T | ((old: T | undefined) => T),
+  key: string
+): [
     value: T,
     setValue: React.Dispatch<React.SetStateAction<T>>,
 ] {
   const [value, setValue] = useState<T>(() => {
-    const stickyValue = window.localStorage.getItem(key);
-    if (stickyValue === null) return defaultValue;
-    try {
-      return JSON.parse(stickyValue) as T;
-    } catch(e) {
-      console.error(e);
+    const v = window.localStorage.getItem(key);
+    // nothing saved
+    if (v === null) {
+      if (typeof defaultValue === "function") {
+        return defaultValue(undefined);
+      }
       return defaultValue;
     }
+    // something saved before
+    try {
+      const old = JSON.parse(v) as T;
+      if (typeof defaultValue === "function") {
+        return defaultValue(old);
+      }
+      return defaultValue;
+    } catch (e) {
+      console.error("error parsting saved state from stickState");
+      return (typeof defaultValue === "function")
+        ? defaultValue(undefined)
+        : defaultValue;
+    }
   });
 
   useEffect(() => {