feat: add loading state to wallet balance (#508)

* feat: add loading state to wallet balance

* refactor: extract the wallet balance into a provider

src/providers/WalletBalance.tsx

@@ -0,0 +1,88 @@
+import { createContext, ReactChild, ReactElement, useContext, useEffect, useState } from 'react'
+import { Context as SettingsContext } from './Settings'
+import { Context as BeeContext } from './Bee'
+import { WalletAddress } from '../utils/wallet'
+
+interface ContextInterface {
+  balance: WalletAddress | null
+  error: Error | null
+  isLoading: boolean
+  lastUpdate: number | null
+  start: (frequency?: number) => void
+  stop: () => void
+  refresh: () => Promise<void>
+}
+
+const initialValues: ContextInterface = {
+  balance: null,
+  error: null,
+  isLoading: false,
+  lastUpdate: null,
+  start: () => {}, // eslint-disable-line
+  stop: () => {}, // eslint-disable-line
+  refresh: () => Promise.reject(),
+}
+
+export const Context = createContext<ContextInterface>(initialValues)
+export const Consumer = Context.Consumer
+
+interface Props {
+  children: ReactChild
+}
+
+export function Provider({ children }: Props): ReactElement {
+  const { provider } = useContext(SettingsContext)
+  const { nodeAddresses } = useContext(BeeContext)
+  const [balance, setBalance] = useState<WalletAddress | null>(initialValues.balance)
+  const [error, setError] = useState<Error | null>(initialValues.error)
+  const [isLoading, setIsLoading] = useState<boolean>(initialValues.isLoading)
+  const [lastUpdate, setLastUpdate] = useState<number | null>(initialValues.lastUpdate)
+  const [frequency, setFrequency] = useState<number | null>(null)
+
+  useEffect(() => {
+    if (nodeAddresses?.ethereum && provider) {
+      WalletAddress.make(nodeAddresses.ethereum, provider).then(setBalance)
+    } else {
+      setBalance(null)
+    }
+  }, [nodeAddresses, provider])
+
+  const refresh = async () => {
+    // Don't want to refresh when already refreshing
+    if (isLoading) return
+
+    if (!balance) return
+
+    try {
+      setIsLoading(true)
+
+      setBalance(await balance.refresh())
+      setLastUpdate(Date.now())
+    } catch (e) {
+      setError(e as Error)
+    } finally {
+      setIsLoading(false)
+    }
+  }
+
+  const start = (freq = 30000) => setFrequency(freq)
+  const stop = () => setFrequency(null)
+
+  // Start the update loop
+  useEffect(() => {
+    refresh()
+
+    // Start autorefresh only if the frequency is set
+    if (frequency) {
+      const interval = setInterval(refresh, frequency)
+
+      return () => clearInterval(interval)
+    }
+  }, [frequency]) // eslint-disable-line react-hooks/exhaustive-deps
+
+  return (
+    <Context.Provider value={{ balance, error, isLoading, lastUpdate, start, stop, refresh }}>
+      {children}
+    </Context.Provider>
+  )
+}