From b23337fd593af00c0d772c4ef9fbae361f2cd353 Mon Sep 17 00:00:00 2001
From: Katja Lutz <mail@katjalutz.ch>
Date: Wed, 22 Jun 2022 21:33:00 +0200
Subject: [PATCH] feat: implement localstorage helper

---
 src/localStore.ts | 85 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 src/localStore.ts

diff --git a/src/localStore.ts b/src/localStore.ts
new file mode 100644
index 0000000..60ab333
--- /dev/null
+++ b/src/localStore.ts
@@ -0,0 +1,85 @@
+import { batch, createEffect, createSignal, onMount } from "solid-js";
+import { createStore, reconcile } from "solid-js/store";
+
+export const createLocalStore = function <T extends Record<string, any>>(
+  initState: T,
+  {
+    prefix = "app",
+    serializer = (v: any) => JSON.stringify(v),
+    deserializer = (v: any) => JSON.parse(v),
+  } = {}
+) {
+  const [state, setState] = createStore(initState);
+  const [mounted, setMounted] = createSignal(false);
+  const localStorage = globalThis.localStorage;
+
+  if (localStorage) {
+    let mounts = 0;
+    let mounted_ = false;
+    const updating = {} as Record<string, any>;
+    const keys = Object.keys(state);
+    const changedBeforeMount = {} as Record<string, any>;
+
+    for (const key of keys) {
+      let storeKey = `${prefix}-${key}`;
+      let mountValue = localStorage.getItem(storeKey);
+      let initRun = true;
+      const [updatingCount, setUpdatingCount] = createSignal(0);
+
+      // TODO: Implement localStorage listener
+
+      createEffect(() => {
+        // During mounts we want to always run this effect even if the state value hasnt changed
+        // We need to run it always to reset updating[key]
+        updatingCount();
+
+        const isInitRun = initRun;
+        initRun = false;
+        const value = serializer(state[key]);
+
+        if (isInitRun && mountValue) {
+          return;
+        }
+
+        // If the key is getting mounted at the moment, we skip the localStorage set
+        if (updating[key]) {
+          updating[key] = false;
+          return;
+        }
+
+        if (!mounted_) {
+          changedBeforeMount[key] = true;
+        }
+
+        if (value === undefined) {
+          localStorage.removeItem(storeKey);
+        } else {
+          localStorage.setItem(storeKey, value);
+        }
+      });
+
+      onMount(() => {
+        if (!changedBeforeMount[key] && mountValue) {
+          updating[key] = true;
+          batch(function () {
+            setUpdatingCount(updatingCount() + 1);
+            setState(key as any, reconcile(deserializer(mountValue)));
+          });
+        }
+
+        mounts++;
+        mountValue = null;
+        if (mounts === keys.length) {
+          setMounted(true);
+          mounted_ = true;
+        }
+      });
+    }
+  }
+
+  return [state, setState, mounted] as [
+    typeof state,
+    typeof setState,
+    typeof mounted
+  ];
+};