implement usePromise hook

client/public/components/accounts_page.tsx

@@ -1,16 +1,12 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import rek from 'rek'
 import Head from './head.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
 
 import type { Account } from '../../../shared/types.ts'
 
 const AccountsPage: FunctionComponent = () => {
-  const [accounts, setAccounts] = useState<Account[]>([])
-
-  useEffect(() => {
-    rek('/api/accounts').then(setAccounts)
-  }, [])
+  const accounts = usePromise<Account[]>(() => rek('/api/accounts'))
 
   return (
     <section>

client/public/components/app.tsx

@@ -1,5 +1,5 @@
 import { h, type FunctionComponent } from 'preact'
-import { useCallback, useEffect } from 'preact/hooks'
+import { useCallback, useEffect, useRef } from 'preact/hooks'
 import { LocationProvider, Route, Router } from 'preact-iso'
 import { get } from 'lowline'
 import Head from './head.ts'
@@ -16,30 +16,47 @@ type Props = {
   title?: string
 }
 
-const remember = throttle(function remember() {
-  window.history.replaceState(
-    {
-      ...window.history.state,
-      scrollTop: window.scrollY,
-    },
-    '',
-    null,
-  )
-}, 100)
+const scroll = () => {
+  const offset = get(window.history, 'state.scrollTop')
+
+  window.scrollTo(0, offset || 0)
+}
 
 const App: FunctionComponent<Props> = ({ error, title }) => {
+  const loadRef = useRef<boolean>(false)
+
   useEffect(() => {
+    history.scrollRestoration = 'manual'
+
+    const remember = throttle(function remember() {
+      if (loadRef.current) return
+
+      window.history.replaceState(
+        {
+          ...window.history.state,
+          scrollTop: window.scrollY,
+        },
+        '',
+        null,
+      )
+    }, 100)
+
     addEventListener('scroll', remember)
 
     return () => removeEventListener('scroll', remember)
-  })
+  }, [])
+
+  const onLoadStart = useCallback(() => {
+    loadRef.current = true
+  }, [])
+
+  const onLoadEnd = useCallback(() => {
+    scroll()
+    loadRef.current = false
+  }, [])
 
   const onRouteChange = useCallback(() => {
-    const offset = get(window.history, 'state.scrollTop')
-
-    setTimeout(() => {
-      window.scrollTo(0, offset || 0)
-    }, 100)
+    if (!loadRef.current) scroll()
   }, [])
 
   return (
@@ -55,7 +72,7 @@ const App: FunctionComponent<Props> = ({ error, title }) => {
           {error ? (
             <ErrorPage error={error} />
           ) : (
-            <Router onRouteChange={onRouteChange}>
+            <Router onLoadStart={onLoadStart} onLoadEnd={onLoadEnd} onRouteChange={onRouteChange}>
               {routes.map((route) => (
                 <Route key={route.path} path={route.path} component={route.component} />
               ))}

client/public/components/balances_page.tsx

@@ -1,21 +1,20 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import cn from 'classnames'
 import rek from 'rek'
 import Head from './head.ts'
 import { formatNumber } from '../utils/format_number.ts'
 import s from './balances_page.module.scss'
+import usePromise from '../../shared/hooks/use_promise.ts'
 
 import type { Balance, FinancialYear } from '../../../shared/types.ts'
 
 const BalancesPage: FunctionComponent = () => {
-  const [balances, setBalances] = useState<Balance[]>([])
-  const [years, setYears] = useState<number[]>([])
-
-  useEffect(() => {
-    rek(`/api/balances`).then(setBalances)
-    rek(`/api/financial-years`).then((financialYears: FinancialYear[]) => setYears(financialYears.map((fy) => fy.year)))
-  }, [])
+  const [balances, years] = usePromise<[Balance[], number[]]>(() =>
+    Promise.all([
+      rek(`/api/balances`),
+      rek(`/api/financial-years`).then((financialYears: FinancialYear[]) => financialYears.map((fy) => fy.year)),
+    ]),
+  )
 
   return (
     <section>

client/public/components/entry_page.tsx

@@ -1,22 +1,14 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import { useRoute } from 'preact-iso'
-import { formatNumber } from '../utils/format_number.ts'
 import rek from 'rek'
-
 import { type Entry } from '../../../shared/types.ts'
-
+import usePromise from '../../shared/hooks/use_promise.ts'
+import { formatNumber } from '../utils/format_number.ts'
 import Head from './head.ts'
 
 const EntryPage: FunctionComponent = () => {
-  const [entry, setEntry] = useState<Entry | null>(null)
   const route = useRoute()
-
-  useEffect(() => {
-    rek(`/api/entries/${route.params.id}`).then(setEntry)
-  }, [])
-
-  if (!entry) return
+  const entry = usePromise<Entry>(() => rek(`/api/entries/${route.params.id}`))
 
   return (
     <section>

client/public/components/invoice_page.tsx

@@ -1,20 +1,15 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import { useRoute } from 'preact-iso'
 import rek from 'rek'
-import Head from './head.ts'
-import { formatNumber } from '../utils/format_number.ts'
-
 import type { Invoice } from '../../../shared/types.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
+import { formatNumber } from '../utils/format_number.ts'
+import Head from './head.ts'
 
 const InvoicePage: FunctionComponent = () => {
-  const [invoice, setInvoice] = useState<Invoice | null>(null)
+  const invoice = usePromise<Invoice>(() => rek(`/api/invoices/${route.params.id}`))
   const route = useRoute()
 
-  useEffect(() => {
-    rek(`/api/invoices/${route.params.id}`).then(setInvoice)
-  }, [])
-
   return (
     <section>
       <Head>

client/public/components/invoices_by_supplier_page.tsx

@@ -1,26 +1,24 @@
 import { h, type FunctionComponent } from 'preact'
 // @ts-ignore
 import Format from 'easy-tz/format'
-import { useEffect, useState } from 'preact/hooks'
 import { useRoute } from 'preact-iso'
 import rek from 'rek'
 import Head from './head.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
 import type { Invoice, Supplier } from '../../../shared/types.ts'
 
 const format = Format.bind(null, null, 'YYYY.MM.DD')
 
 const InvoicesPage: FunctionComponent = () => {
-  const [supplier, setSupplier] = useState<Supplier | null>(null)
-  const [invoices, setInvoices] = useState<Invoice[]>([])
-  const [totalAmount, setTotalAmount] = useState<number | null>(null)
-
   const route = useRoute()
 
-  useEffect(() => {
-    rek(`/api/suppliers/${route.params.supplier}`).then(setSupplier)
-    rek(`/api/invoices?supplier=${route.params.supplier}`).then(setInvoices)
-    rek(`/api/invoices/total-amount?supplier=${route.params.supplier}`).then(setTotalAmount)
-  }, [route.params.supplier])
+  const [supplier, invoices, totalAmount] = usePromise<[Supplier, Invoice[], number]>(() =>
+    Promise.all([
+      rek(`/api/suppliers/${route.params.supplier}`),
+      rek(`/api/invoices?supplier=${route.params.supplier}`),
+      rek(`/api/invoices/total-amount?supplier=${route.params.supplier}`),
+    ]),
+  )
 
   return (
     <section>

client/public/components/invoices_page.tsx

@@ -1,16 +1,12 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import rek from 'rek'
 import Head from './head.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
 
 import type { Supplier } from '../../../shared/types.ts'
 
 const InvoicesPage: FunctionComponent = () => {
-  const [suppliers, setSuppliers] = useState<Supplier[]>([])
-
-  useEffect(() => {
-    rek('/api/suppliers').then(setSuppliers)
-  }, [])
+  const suppliers = usePromise<Supplier[]>(() => rek('/api/suppliers'))
 
   return (
     <section>

client/public/components/objects_page.tsx

@@ -1,19 +1,16 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
+import { useState } from 'preact/hooks'
 import rek from 'rek'
+import type { Object as ObjectType } from '../../../shared/types.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
 import Head from './head.ts'
 import Object from './object.tsx'
 import s from './results_page.module.scss'
-import type { Object as ObjectType } from '../../../shared/types.ts'
 
 const ObjectsPage: FunctionComponent = () => {
-  const [objects, setObjects] = useState<ObjectType[]>([])
+  const objects = usePromise<ObjectType[]>(() => rek('/api/objects'))
   const [currentObject, setCurrentObject] = useState<ObjectType | null>(null)
 
-  useEffect(() => {
-    rek('/api/objects').then((objects: ObjectType[]) => setObjects(objects))
-  }, [])
-
   return (
     <section>
       <Head>

client/public/components/results_page.tsx

@@ -1,21 +1,19 @@
 import { h, type FunctionComponent } from 'preact'
-import { useEffect, useState } from 'preact/hooks'
 import cn from 'classnames'
 import rek from 'rek'
-import Head from './head.ts'
+import type { FinancialYear, Result } from '../../../shared/types.ts'
 import { formatNumber } from '../utils/format_number.ts'
+import usePromise from '../../shared/hooks/use_promise.ts'
+import Head from './head.ts'
 import s from './results_page.module.scss'
 
-import type { FinancialYear, Result } from '../../../shared/types.ts'
-
 const ResultsPage: FunctionComponent = () => {
-  const [results, setResults] = useState<Result[]>([])
-  const [years, setYears] = useState<number[]>([])
-
-  useEffect(() => {
-    rek(`/api/results`).then((results: Result[]) => setResults(results))
-    rek(`/api/financial-years`).then((financialYears: FinancialYear[]) => setYears(financialYears.map((fy) => fy.year)))
-  }, [])
+  const [results, years] = usePromise<[Result[], number[]]>(() =>
+    Promise.all([
+      rek(`/api/results`),
+      rek(`/api/financial-years`).then((financialYears: FinancialYear[]) => financialYears.map((fy) => fy.year)),
+    ]),
+  )
 
   return (
     <section>

client/shared/hooks/use_promise.ts

@@ -0,0 +1,17 @@
+import { useRef, useState } from 'preact/hooks'
+
+export default function usePromise<R = any, E = Error>(fn: () => Promise<R>) {
+  const [result, setResult] = useState<R | null>(null)
+  const [error, setError] = useState<E | null>(null)
+  const promiseRef = useRef<Promise<void> | null>(null)
+
+  if (!promiseRef.current) {
+    throw (promiseRef.current = fn().then(setResult, setError))
+  } else if (result) {
+    return result
+  } else if (error) {
+    throw error
+  } else {
+    throw promiseRef.current
+  }
+}

package.json

@@ -40,7 +40,7 @@
     "pg": "^8.16.3",
     "pg-protocol": "^1.10.3",
     "pino-abstract-transport": "^3.0.0",
-    "preact": "^10.27.2",
+    "preact": "^10.28.0",
     "preact-iso": "^2.11.0",
     "rek": "^0.8.1"
   },

pnpm-lock.yaml

@@ -60,11 +60,11 @@ importers:
         specifier: ^3.0.0
         version: 3.0.0
       preact:
-        specifier: ^10.27.2
-        version: 10.27.2
+        specifier: ^10.28.0
+        version: 10.28.0
       preact-iso:
         specifier: ^2.11.0
-        version: 2.11.0(preact-render-to-string@6.6.3(preact@10.27.2))(preact@10.27.2)
+        version: 2.11.0(preact-render-to-string@6.6.3(preact@10.28.0))(preact@10.28.0)
       rek:
         specifier: ^0.8.1
         version: 0.8.1
@@ -74,10 +74,10 @@ importers:
         version: 7.28.5
       '@preact/preset-vite':
         specifier: ^2.10.1
-        version: 2.10.2(@babel/core@7.28.5)(preact@10.27.2)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))
+        version: 2.10.2(@babel/core@7.28.5)(preact@10.28.0)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))
       '@testing-library/preact':
         specifier: ^3.2.4
-        version: 3.2.4(preact@10.27.2)
+        version: 3.2.4(preact@10.28.0)
       '@types/d3-dsv':
         specifier: ^3.0.7
         version: 3.0.7
@@ -1895,8 +1895,8 @@ packages:
     peerDependencies:
       preact: '>=10 || >= 11.0.0-0'
 
-  preact@10.27.2:
-    resolution: {integrity: sha512-5SYSgFKSyhCbk6SrXyMpqjb5+MQBgfvEKE/OC+PujcY34sOpqtr+0AZQtPYx5IA6VxynQ7rUPCtKzyovpj9Bpg==}
+  preact@10.28.0:
+    resolution: {integrity: sha512-rytDAoiXr3+t6OIP3WGlDd0ouCUG1iCWzkcY3++Nreuoi17y6T5i/zRhe6uYfoVcxq6YU+sBtJouuRDsq8vvqA==}
 
   prettier@3.6.2:
     resolution: {integrity: sha512-I7AIg5boAr5R0FFtJ6rCfD+LFsWHp81dolrFD8S79U9tb8Az2nGrJncnMSnys+bpQJfRUzqs9hnA81OAA3hCuQ==}
@@ -2830,12 +2830,12 @@ snapshots:
 
   '@pinojs/redact@0.4.0': {}
 
-  '@preact/preset-vite@2.10.2(@babel/core@7.28.5)(preact@10.27.2)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))':
+  '@preact/preset-vite@2.10.2(@babel/core@7.28.5)(preact@10.28.0)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))':
     dependencies:
       '@babel/core': 7.28.5
       '@babel/plugin-transform-react-jsx': 7.27.1(@babel/core@7.28.5)
       '@babel/plugin-transform-react-jsx-development': 7.27.1(@babel/core@7.28.5)
-      '@prefresh/vite': 2.4.11(preact@10.27.2)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))
+      '@prefresh/vite': 2.4.11(preact@10.28.0)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))
       '@rollup/pluginutils': 4.2.1
       babel-plugin-transform-hook-names: 1.0.2(@babel/core@7.28.5)
       debug: 4.4.3
@@ -2848,20 +2848,20 @@ snapshots:
 
   '@prefresh/babel-plugin@0.5.2': {}
 
-  '@prefresh/core@1.5.9(preact@10.27.2)':
+  '@prefresh/core@1.5.9(preact@10.28.0)':
     dependencies:
-      preact: 10.27.2
+      preact: 10.28.0
 
   '@prefresh/utils@1.2.1': {}
 
-  '@prefresh/vite@2.4.11(preact@10.27.2)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))':
+  '@prefresh/vite@2.4.11(preact@10.28.0)(vite@7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1))':
     dependencies:
       '@babel/core': 7.28.5
       '@prefresh/babel-plugin': 0.5.2
-      '@prefresh/core': 1.5.9(preact@10.27.2)
+      '@prefresh/core': 1.5.9(preact@10.28.0)
       '@prefresh/utils': 1.2.1
       '@rollup/pluginutils': 4.2.1
-      preact: 10.27.2
+      preact: 10.28.0
       vite: 7.2.4(@types/node@24.10.1)(sass@1.94.2)(yaml@2.8.1)
     transitivePeerDependencies:
       - supports-color
@@ -2948,10 +2948,10 @@ snapshots:
       lz-string: 1.5.0
       pretty-format: 27.5.1
 
-  '@testing-library/preact@3.2.4(preact@10.27.2)':
+  '@testing-library/preact@3.2.4(preact@10.28.0)':
     dependencies:
       '@testing-library/dom': 8.20.1
-      preact: 10.27.2
+      preact: 10.28.0
 
   '@types/aria-query@5.0.4': {}
 
@@ -3942,16 +3942,16 @@ snapshots:
     dependencies:
       xtend: 4.0.2
 
-  preact-iso@2.11.0(preact-render-to-string@6.6.3(preact@10.27.2))(preact@10.27.2):
+  preact-iso@2.11.0(preact-render-to-string@6.6.3(preact@10.28.0))(preact@10.28.0):
     dependencies:
-      preact: 10.27.2
-      preact-render-to-string: 6.6.3(preact@10.27.2)
+      preact: 10.28.0
+      preact-render-to-string: 6.6.3(preact@10.28.0)
 
-  preact-render-to-string@6.6.3(preact@10.27.2):
+  preact-render-to-string@6.6.3(preact@10.28.0):
     dependencies:
-      preact: 10.27.2
+      preact: 10.28.0
 
-  preact@10.27.2: {}
+  preact@10.28.0: {}
 
   prettier@3.6.2: {}