From 5f4611d65e40eae3ca6191a15f68d69ea5a1c4cb Mon Sep 17 00:00:00 2001
From: Kirill Rogovoy <kirill@rogovoy.me>
Date: Tue, 20 Jul 2021 21:24:52 +0300
Subject: WIP

---
 util/persistant-state.ts | 59 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 util/persistant-state.ts

(limited to 'util')

diff --git a/util/persistant-state.ts b/util/persistant-state.ts
new file mode 100644
index 0000000..5e7e35e
--- /dev/null
+++ b/util/persistant-state.ts
@@ -0,0 +1,59 @@
+import { useState, useEffect } from 'react'
+
+export function usePersistantState<V>(
+  storageKey: string,
+  defaultValue: V,
+  options: {
+    storage?: Storage
+  } = {},
+): [V, (v: V | ((v: V) => V)) => void] {
+  const storage = getStorage<V | undefined>(storageKey, options.storage ?? localStorage)
+
+  const storageValue = storage.get()
+  const calculatedDefaultValue = storageValue !== undefined ? storageValue : defaultValue
+  if (calculatedDefaultValue !== storageValue) {
+    storage.update(calculatedDefaultValue)
+  }
+
+  const [value, setValue] = useState<V>(calculatedDefaultValue)
+
+  // change state gracefully when changing the storageKey
+  useEffect(() => {
+    if (value !== calculatedDefaultValue) {
+      setValue(calculatedDefaultValue)
+    }
+  }, [storageKey])
+  const set = (newValueOrFn: V | ((v: V) => V)) => {
+    if (newValueOrFn instanceof Function) {
+      setValue((oldValue) => {
+        const newValue = newValueOrFn(oldValue)
+        storage.update(newValue)
+        return newValue
+      })
+      return
+    }
+    setValue(newValueOrFn)
+    storage.update(newValueOrFn)
+  }
+
+  return [value, set]
+}
+
+export function getStorage<T>(key: string, storage: Storage) {
+  return {
+    get(): T | undefined {
+      const value = storage.getItem(key)
+      if (value && value !== 'undefined') {
+        return JSON.parse(value)
+      }
+
+      return undefined
+    },
+    update(updatedState: T) {
+      storage.setItem(key, JSON.stringify(updatedState))
+    },
+    remove() {
+      storage.removeItem(key)
+    },
+  }
+}
-- 
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