feat(lc-dapp): account balance

examples/light-client-dapp/package.json

@@ -11,10 +11,15 @@
   },
   "dependencies": {
     "@picocss/pico": "^2.0.3",
+    "@polkadot-api/client": "0.0.1-86c37582599a5aaa7c2dde1d765f8af5ef6def2a.1.0",
+    "@polkadot-api/metadata-builders": "0.0.1-86c37582599a5aaa7c2dde1d765f8af5ef6def2a.1.0",
+    "@polkadot-api/substrate-client": "0.0.1-86c37582599a5aaa7c2dde1d765f8af5ef6def2a.1.0",
     "@polkadot-api/utils": "0.0.1-86c37582599a5aaa7c2dde1d765f8af5ef6def2a.1.0",
     "@polkadot-labs/hdkd-helpers": "^0.0.5",
     "react": "^18.2.0",
-    "react-dom": "^18.2.0"
+    "react-dom": "^18.2.0",
+    "react-select": "^5.8.0",
+    "rxjs": "^7.8.1"
   },
   "devDependencies": {
     "@substrate/unstable-wallet-provider": "workspace:^",

examples/light-client-dapp/src/components/Transfer.tsx

@@ -1,7 +1,9 @@
-import { FormEvent, useCallback, useEffect, useState } from "react"
+import { FormEvent, useCallback, useEffect, useMemo, useState } from "react"
 import { ss58Decode } from "@polkadot-labs/hdkd-helpers"
 import { UnstableWallet } from "@substrate/unstable-wallet-provider"
 import { toHex } from "@polkadot-api/utils"
+import Select from "react-select"
+import { useSystemAccount } from "../hooks"
 
 type Props = {
   provider: UnstableWallet.Provider
@@ -14,6 +16,21 @@ const chainId =
 
 export const Transfer = ({ provider }: Props) => {
   const [accounts, setAccounts] = useState<UnstableWallet.Account[]>([])
+  const [selectedAccount, setSelectedAccount] = useState<{
+    value: string
+    label: string
+  } | null>(null)
+  const connect = useMemo(
+    () => provider.getChains()[chainId].connect,
+    [provider],
+  )
+  const accountStorage = useSystemAccount(
+    connect,
+    selectedAccount ? selectedAccount.value : null,
+  )
+
+  const balance = accountStorage?.data.free ?? 0n
+
   useEffect(() => {
     provider.getAccounts(chainId).then((accounts) => {
       setAccounts(accounts)
@@ -24,11 +41,15 @@ export const Transfer = ({ provider }: Props) => {
   const handleOnSubmit = useCallback(
     async (e: FormEvent) => {
       e.preventDefault()
+      if (!selectedAccount) {
+        return
+      }
+
       setIsCreatingTransaction(true)
       try {
         const tx = await provider.createTx(
           chainId,
-          toHex(ss58Decode(accounts[0].address)[0]),
+          toHex(ss58Decode(selectedAccount.value)[0]),
           "0x04030012aed8a0f7425c9f4c71e75bf087e9c68ab701b1faa23a10e4785d722d962115070010a5d4e8",
         )
         console.log({ tx })
@@ -37,12 +58,16 @@ export const Transfer = ({ provider }: Props) => {
       }
       setIsCreatingTransaction(false)
     },
-    [provider, accounts],
+    [provider, selectedAccount],
   )
 
+  const accountOptions = accounts.map((account) => ({
+    value: account.address,
+    label: account.address,
+  }))
+
   // TODO: handle form fields and submission with react
   // TODO: fetch accounts from extension
-  // TODO: fetch selected account balance
   // TODO: validate destination address
   // TODO: use PAPI to encode the transaction calldata
   // TODO: transfer should trigger an extension popup that signs the transaction
@@ -52,21 +77,19 @@ export const Transfer = ({ provider }: Props) => {
     <article>
       <header>Transfer funds</header>
       <form onSubmit={handleOnSubmit}>
-        <select defaultValue={""}>
-          <option disabled value={""}>
-            Select Account...
-          </option>
-          {accounts.map((account) => (
-            <option key={account.address} value={account.address}>
-              {account.address}
-            </option>
-          ))}
-        </select>
-        <small>Balance: 123456789</small>
+        <Select
+          defaultValue={selectedAccount}
+          onChange={setSelectedAccount}
+          options={accountOptions}
+        />
+        <small>Balance: {`${balance}`}</small>
         <input placeholder="to"></input>
         <input type="number" placeholder="amount"></input>
         <footer>
-          <button type="submit" disabled={isCreatingTransaction}>
+          <button
+            type="submit"
+            disabled={!selectedAccount || isCreatingTransaction}
+          >
             Transfer
           </button>
         </footer>

examples/light-client-dapp/src/hooks/index.ts

@@ -1 +1,2 @@
 export * from "./useProvider"
+export * from "./useSystemAccount"

examples/light-client-dapp/src/hooks/useSystemAccount.ts

@@ -0,0 +1,78 @@
+import { distinct, filter, first, map, mergeMap, tap } from "rxjs"
+import { getObservableClient } from "@polkadot-api/client"
+import { ConnectProvider, createClient } from "@polkadot-api/substrate-client"
+import { getDynamicBuilder } from "@polkadot-api/metadata-builders"
+import { useEffect, useState } from "react"
+
+export type SystemAccountStorage = {
+  consumers: number
+  data: {
+    flags: bigint
+    free: bigint
+    frozen: bigint
+    reserved: bigint
+  }
+  nonce: number
+  providers: number
+  sufficients: number
+}
+
+export const useSystemAccount = (
+  provider: ConnectProvider,
+  address: string | null,
+) => {
+  const [systemAccount, setSystemAccount] = useState<SystemAccountStorage>()
+
+  useEffect(() => {
+    if (!address) {
+      return
+    }
+
+    setSystemAccount(undefined)
+
+    const client = getObservableClient(createClient(provider))
+
+    const { metadata$, finalized$, unfollow, storage$ } = client.chainHead$()
+
+    const subscription = metadata$
+      .pipe(
+        filter(Boolean),
+        first(),
+        mergeMap((metadata) => {
+          const dynamicBuilder = getDynamicBuilder(metadata)
+          const storageAccount = dynamicBuilder.buildStorage(
+            "System",
+            "Account",
+          )
+
+          const storageQuery = finalized$.pipe(
+            mergeMap((blockInfo) =>
+              storage$(blockInfo.hash, "value", () =>
+                storageAccount.enc(address),
+              ).pipe(
+                filter(Boolean),
+                distinct(),
+                map(
+                  (value) => storageAccount.dec(value) as SystemAccountStorage,
+                ),
+              ),
+            ),
+          )
+
+          return storageQuery
+        }),
+        tap((systemAccountStorage) => {
+          setSystemAccount(systemAccountStorage)
+        }),
+      )
+      .subscribe()
+
+    return () => {
+      subscription.unsubscribe()
+      unfollow()
+      client.destroy()
+    }
+  }, [provider, address])
+
+  return systemAccount
+}