First version

.gitignore

@@ -27,6 +27,7 @@ yarn-error.log*
 
 # local env files
 .env*.local
+.env
 
 # vercel
 .vercel
@@ -34,3 +35,6 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# db
+postgres-data

.prettierrc

@@ -0,0 +1,5 @@
+{
+  "semi": false,
+  "singleQuote": true,
+  "plugins": ["prettier-plugin-organize-imports"]
+}

components.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "https://ui.shadcn.com/schema.json",
+  "style": "default",
+  "rsc": true,
+  "tsx": true,
+  "tailwind": {
+    "config": "tailwind.config.js",
+    "css": "app/globals.css",
+    "baseColor": "slate",
+    "cssVariables": true
+  },
+  "aliases": {
+    "components": "@/components",
+    "utils": "@/lib/utils"
+  }
+}

package.json

@@ -6,22 +6,42 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "next lint"
+    "lint": "next lint",
+    "postinstall": "prisma migrate deploy && prisma generate"
   },
   "dependencies": {
+    "@hookform/resolvers": "^3.3.2",
+    "@prisma/client": "5.6.0",
+    "@radix-ui/react-checkbox": "^1.0.4",
+    "@radix-ui/react-label": "^2.0.2",
+    "@radix-ui/react-select": "^2.0.0",
+    "@radix-ui/react-slot": "^1.0.2",
+    "class-variance-authority": "^0.7.0",
+    "clsx": "^2.0.0",
+    "lucide-react": "^0.290.0",
+    "next": "14.0.0",
+    "prisma": "^5.6.0",
     "react": "^18",
     "react-dom": "^18",
-    "next": "14.0.0"
+    "react-hook-form": "^7.47.0",
+    "tailwind-merge": "^1.14.0",
+    "tailwindcss-animate": "^1.0.7",
+    "uuid": "^9.0.1",
+    "zod": "^3.22.4"
   },
   "devDependencies": {
-    "typescript": "^5",
+    "@total-typescript/ts-reset": "^0.5.1",
     "@types/node": "^20",
     "@types/react": "^18",
     "@types/react-dom": "^18",
+    "@types/uuid": "^9.0.6",
     "autoprefixer": "^10",
-    "postcss": "^8",
-    "tailwindcss": "^3",
     "eslint": "^8",
-    "eslint-config-next": "14.0.0"
+    "eslint-config-next": "14.0.0",
+    "postcss": "^8",
+    "prettier": "^3.0.3",
+    "prettier-plugin-organize-imports": "^3.2.3",
+    "tailwindcss": "^3",
+    "typescript": "^5"
   }
 }

prisma/migrations/20231205211834_create_models/migration.sql

@@ -0,0 +1,46 @@
+-- CreateTable
+CREATE TABLE "Group" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+
+    CONSTRAINT "Group_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Participant" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "groupId" TEXT NOT NULL,
+
+    CONSTRAINT "Participant_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Expense" (
+    "id" TEXT NOT NULL,
+    "title" TEXT NOT NULL,
+    "amount" DECIMAL(65,30) NOT NULL,
+    "paidById" TEXT NOT NULL,
+
+    CONSTRAINT "Expense_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "ExpensePaidFor" (
+    "expenseId" TEXT NOT NULL,
+    "participantId" TEXT NOT NULL,
+
+    CONSTRAINT "ExpensePaidFor_pkey" PRIMARY KEY ("expenseId","participantId")
+);
+
+-- AddForeignKey
+ALTER TABLE "Participant" ADD CONSTRAINT "Participant_groupId_fkey" FOREIGN KEY ("groupId") REFERENCES "Group"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "Expense" ADD CONSTRAINT "Expense_paidById_fkey" FOREIGN KEY ("paidById") REFERENCES "Participant"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ExpensePaidFor" ADD CONSTRAINT "ExpensePaidFor_expenseId_fkey" FOREIGN KEY ("expenseId") REFERENCES "Expense"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ExpensePaidFor" ADD CONSTRAINT "ExpensePaidFor_participantId_fkey" FOREIGN KEY ("participantId") REFERENCES "Participant"("id") ON DELETE RESTRICT ON UPDATE CASCADE;

prisma/migrations/20231205214145_add_group_to_expenses/migration.sql

@@ -0,0 +1,11 @@
+/*
+  Warnings:
+
+  - Added the required column `groupId` to the `Expense` table without a default value. This is not possible if the table is not empty.
+
+*/
+-- AlterTable
+ALTER TABLE "Expense" ADD COLUMN     "groupId" TEXT NOT NULL;
+
+-- AddForeignKey
+ALTER TABLE "Expense" ADD CONSTRAINT "Expense_groupId_fkey" FOREIGN KEY ("groupId") REFERENCES "Group"("id") ON DELETE RESTRICT ON UPDATE CASCADE;

prisma/migrations/20231205214538_change_amount_type/migration.sql

@@ -0,0 +1,8 @@
+/*
+  Warnings:
+
+  - You are about to alter the column `amount` on the `Expense` table. The data in that column could be lost. The data in that column will be cast from `Decimal(65,30)` to `Integer`.
+
+*/
+-- AlterTable
+ALTER TABLE "Expense" ALTER COLUMN "amount" SET DATA TYPE INTEGER;

prisma/migrations/migration_lock.toml

@@ -0,0 +1,3 @@
+# Please do not edit this file manually
+# It should be added in your version-control system (i.e. Git)
+provider = "postgresql"

prisma/schema.prisma

@@ -0,0 +1,48 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider  = "postgresql"
+  url       = env("POSTGRES_PRISMA_URL") // uses connection pooling
+  directUrl = env("POSTGRES_URL_NON_POOLING") // uses a direct connection
+}
+
+model Group {
+  id           String        @id
+  name         String
+  participants Participant[]
+  expenses     Expense[]
+}
+
+model Participant {
+  id              String           @id
+  name            String
+  group           Group            @relation(fields: [groupId], references: [id])
+  groupId         String
+  expensesPaidBy  Expense[]
+  expensesPaidFor ExpensePaidFor[]
+}
+
+model Expense {
+  id       String           @id
+  group    Group            @relation(fields: [groupId], references: [id])
+  title    String
+  amount   Int
+  paidBy   Participant      @relation(fields: [paidById], references: [id])
+  paidById String
+  paidFor  ExpensePaidFor[]
+  groupId  String
+}
+
+model ExpensePaidFor {
+  expense       Expense     @relation(fields: [expenseId], references: [id])
+  participant   Participant @relation(fields: [participantId], references: [id])
+  expenseId     String
+  participantId String
+
+  @@id([expenseId, participantId])
+}

reset.d.ts

@@ -0,0 +1 @@
+import '@total-typescript/ts-reset'

src/app/globals.css

@@ -2,26 +2,75 @@
 @tailwind components;
 @tailwind utilities;
 
-:root {
-  --foreground-rgb: 0, 0, 0;
-  --background-start-rgb: 214, 219, 220;
-  --background-end-rgb: 255, 255, 255;
-}
-
-@media (prefers-color-scheme: dark) {
+@layer base {
   :root {
-    --foreground-rgb: 255, 255, 255;
-    --background-start-rgb: 0, 0, 0;
-    --background-end-rgb: 0, 0, 0;
+    --background: 0 0% 100%;
+    --foreground: 222.2 84% 4.9%;
+
+    --card: 0 0% 100%;
+    --card-foreground: 222.2 84% 4.9%;
+
+    --popover: 0 0% 100%;
+    --popover-foreground: 222.2 84% 4.9%;
+
+    --primary: 222.2 47.4% 11.2%;
+    --primary-foreground: 210 40% 98%;
+
+    --secondary: 210 40% 96.1%;
+    --secondary-foreground: 222.2 47.4% 11.2%;
+
+    --muted: 210 40% 96.1%;
+    --muted-foreground: 215.4 16.3% 46.9%;
+
+    --accent: 210 40% 96.1%;
+    --accent-foreground: 222.2 47.4% 11.2%;
+
+    --destructive: 0 84.2% 60.2%;
+    --destructive-foreground: 210 40% 98%;
+
+    --border: 214.3 31.8% 91.4%;
+    --input: 214.3 31.8% 91.4%;
+    --ring: 222.2 84% 4.9%;
+
+    --radius: 0.5rem;
+  }
+
+  .dark {
+    --background: 222.2 84% 4.9%;
+    --foreground: 210 40% 98%;
+
+    --card: 222.2 84% 4.9%;
+    --card-foreground: 210 40% 98%;
+
+    --popover: 222.2 84% 4.9%;
+    --popover-foreground: 210 40% 98%;
+
+    --primary: 210 40% 98%;
+    --primary-foreground: 222.2 47.4% 11.2%;
+
+    --secondary: 217.2 32.6% 17.5%;
+    --secondary-foreground: 210 40% 98%;
+
+    --muted: 217.2 32.6% 17.5%;
+    --muted-foreground: 215 20.2% 65.1%;
+
+    --accent: 217.2 32.6% 17.5%;
+    --accent-foreground: 210 40% 98%;
+
+    --destructive: 0 62.8% 30.6%;
+    --destructive-foreground: 210 40% 98%;
+
+    --border: 217.2 32.6% 17.5%;
+    --input: 217.2 32.6% 17.5%;
+    --ring: 212.7 26.8% 83.9%;
   }
 }
 
-body {
-  color: rgb(var(--foreground-rgb));
-  background: linear-gradient(
-      to bottom,
-      transparent,
-      rgb(var(--background-end-rgb))
-    )
-    rgb(var(--background-start-rgb));
+@layer base {
+  * {
+    @apply border-border;
+  }
+  body {
+    @apply bg-background text-foreground;
+  }
 }

src/app/groups/[groupId]/edit/page.tsx

@@ -0,0 +1,36 @@
+import { GroupForm } from '@/components/group-form'
+import { Button } from '@/components/ui/button'
+import { getGroup, updateGroup } from '@/lib/api'
+import { groupFormSchema } from '@/lib/schemas'
+import { ChevronLeft } from 'lucide-react'
+import Link from 'next/link'
+import { notFound, redirect } from 'next/navigation'
+
+export default async function EditGroupPage({
+  params: { groupId },
+}: {
+  params: { groupId: string }
+}) {
+  const group = await getGroup(groupId)
+  if (!group) notFound()
+
+  async function updateGroupAction(values: unknown) {
+    'use server'
+    const groupFormValues = groupFormSchema.parse(values)
+    const group = await updateGroup(groupId, groupFormValues)
+    redirect(`/groups/${group.id}`)
+  }
+
+  return (
+    <main>
+      <div className="mb-4">
+        <Button variant="ghost" asChild>
+          <Link href={`/groups/${groupId}`}>
+            <ChevronLeft className="w-4 h-4 mr-2" /> Back to group
+          </Link>
+        </Button>
+      </div>
+      <GroupForm group={group} onSubmit={updateGroupAction} />
+    </main>
+  )
+}

src/app/groups/[groupId]/expenses/[expenseId]/edit/page.tsx

@@ -0,0 +1,42 @@
+import { ExpenseForm } from '@/components/expense-form'
+import { Button } from '@/components/ui/button'
+import { getExpense, getGroup, updateExpense } from '@/lib/api'
+import { expenseFormSchema } from '@/lib/schemas'
+import { ChevronLeft } from 'lucide-react'
+import Link from 'next/link'
+import { notFound, redirect } from 'next/navigation'
+
+export default async function EditExpensePage({
+  params: { groupId, expenseId },
+}: {
+  params: { groupId: string; expenseId: string }
+}) {
+  const group = await getGroup(groupId)
+  if (!group) notFound()
+  const expense = await getExpense(groupId, expenseId)
+  if (!expense) notFound()
+
+  async function updateExpenseAction(values: unknown) {
+    'use server'
+    const expenseFormValues = expenseFormSchema.parse(values)
+    await updateExpense(groupId, expenseId, expenseFormValues)
+    redirect(`/groups/${groupId}`)
+  }
+
+  return (
+    <main>
+      <div className="mb-4">
+        <Button variant="ghost" asChild>
+          <Link href={`/groups/${groupId}`}>
+            <ChevronLeft className="w-4 h-4 mr-2" /> Back to group
+          </Link>
+        </Button>
+      </div>
+      <ExpenseForm
+        group={group}
+        expense={expense}
+        onSubmit={updateExpenseAction}
+      />
+    </main>
+  )
+}

src/app/groups/[groupId]/expenses/create/page.tsx

@@ -0,0 +1,37 @@
+import { ExpenseForm } from '@/components/expense-form'
+import { Button } from '@/components/ui/button'
+import { createExpense, getGroup } from '@/lib/api'
+import { expenseFormSchema } from '@/lib/schemas'
+import { ChevronLeft } from 'lucide-react'
+import Link from 'next/link'
+import { notFound, redirect } from 'next/navigation'
+
+export default async function ExpensePage({
+  params: { groupId },
+}: {
+  params: { groupId: string }
+}) {
+  const group = await getGroup(groupId)
+  if (!group) notFound()
+
+  async function createExpenseAction(values: unknown) {
+    'use server'
+    const expenseFormValues = expenseFormSchema.parse(values)
+    await createExpense(expenseFormValues, groupId)
+    redirect(`/groups/${groupId}`)
+  }
+
+  return (
+    <main>
+      <div className="mb-4">
+        <Button variant="ghost" asChild>
+          <Link href={`/groups/${groupId}`}>
+            <ChevronLeft className="w-4 h-4 mr-2" /> Back to group
+          </Link>
+        </Button>
+      </div>
+
+      <ExpenseForm group={group} onSubmit={createExpenseAction} />
+    </main>
+  )
+}

src/app/groups/[groupId]/page.tsx

@@ -0,0 +1,141 @@
+import { SaveGroupLocally } from '@/app/groups/[groupId]/save-recent-group'
+import { Badge } from '@/components/ui/badge'
+import { Button } from '@/components/ui/button'
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from '@/components/ui/card'
+import {
+  Table,
+  TableBody,
+  TableCell,
+  TableHead,
+  TableHeader,
+  TableRow,
+} from '@/components/ui/table'
+import { getGroup, getGroupExpenses } from '@/lib/api'
+import { ChevronLeft, ChevronRight, Edit, Plus } from 'lucide-react'
+import Link from 'next/link'
+import { notFound } from 'next/navigation'
+
+export default async function GroupPage({
+  params: { groupId },
+}: {
+  params: { groupId: string }
+}) {
+  const group = await getGroup(groupId)
+  if (!group) notFound()
+
+  const expenses = await getGroupExpenses(groupId)
+
+  return (
+    <main>
+      <div className="mb-4 flex justify-between">
+        <Button variant="ghost" asChild>
+          <Link href="/groups">
+            <ChevronLeft className="w-4 h-4 mr-2" /> Back to recent groups
+          </Link>
+        </Button>
+        <Button variant="secondary" asChild>
+          <Link href={`/groups/${groupId}/edit`}>
+            <Edit className="w-4 h-4 mr-2" /> Edit group settings
+          </Link>
+        </Button>
+      </div>
+
+      <h1 className="font-bold mb-4">{group.name}</h1>
+
+      <Card className="mb-4">
+        <div className="flex flex-1">
+          <CardHeader className="flex-1">
+            <CardTitle>Expenses</CardTitle>
+            <CardDescription>
+              Here are the expenses that you created for your group.
+            </CardDescription>
+          </CardHeader>
+          <CardHeader>
+            <Button asChild size="icon">
+              <Link href={`/groups/${groupId}/expenses/create`}>
+                <Plus />
+              </Link>
+            </Button>
+          </CardHeader>
+        </div>
+        <CardContent className="p-0">
+          <Table className="">
+            <TableHeader>
+              <TableRow>
+                <TableHead>Title</TableHead>
+                <TableHead>Paid by</TableHead>
+                <TableHead>Paid for</TableHead>
+                <TableHead className="text-right">Amount</TableHead>
+                <TableHead className="w-0"></TableHead>
+              </TableRow>
+            </TableHeader>
+            <TableBody>
+              {expenses.map((expense) => (
+                <TableRow key={expense.id}>
+                  <TableCell>{expense.title}</TableCell>
+                  <TableCell>
+                    <Badge variant="secondary">
+                      {
+                        group.participants.find(
+                          (p) => p.id === expense.paidById,
+                        )?.name
+                      }
+                    </Badge>
+                  </TableCell>
+                  <TableCell className="flex flex-wrap gap-1">
+                    {expense.paidFor.map((paidFor, index) => (
+                      <Badge variant="secondary" key={index}>
+                        {
+                          group.participants.find(
+                            (p) => p.id === paidFor.participantId,
+                          )?.name
+                        }
+                      </Badge>
+                    ))}
+                  </TableCell>
+                  <TableCell className="text-right tabular-nums">
+                    $ {expense.amount.toFixed(2)}
+                  </TableCell>
+                  <TableCell>
+                    <Button
+                      size="icon"
+                      variant="link"
+                      className="-my-2"
+                      asChild
+                    >
+                      <Link
+                        href={`/groups/${groupId}/expenses/${expense.id}/edit`}
+                      >
+                        <ChevronRight className="w-4 h-4" />
+                      </Link>
+                    </Button>
+                  </TableCell>
+                </TableRow>
+              ))}
+            </TableBody>
+          </Table>
+        </CardContent>
+      </Card>
+
+      <Card className="mb-4">
+        <CardHeader>
+          <CardTitle>Participants</CardTitle>
+        </CardHeader>
+        <CardContent>
+          <ul>
+            {group.participants.map((participant) => (
+              <li key={participant.id}>{participant.name}</li>
+            ))}
+          </ul>
+        </CardContent>
+      </Card>
+      <SaveGroupLocally group={{ id: group.id, name: group.name }} />
+    </main>
+  )
+}

src/app/groups/[groupId]/save-recent-group.tsx

@@ -0,0 +1,18 @@
+'use client'
+import {
+  RecentGroup,
+  saveRecentGroup,
+} from '@/app/groups/recent-groups-helpers'
+import { useEffect } from 'react'
+
+type Props = {
+  group: RecentGroup
+}
+
+export function SaveGroupLocally({ group }: Props) {
+  useEffect(() => {
+    saveRecentGroup(group)
+  }, [])
+
+  return null
+}

src/app/groups/create/page.tsx

@@ -0,0 +1,29 @@
+import { GroupForm } from '@/components/group-form'
+import { Button } from '@/components/ui/button'
+import { createGroup } from '@/lib/api'
+import { groupFormSchema } from '@/lib/schemas'
+import { ChevronLeft } from 'lucide-react'
+import Link from 'next/link'
+import { redirect } from 'next/navigation'
+
+export default function CreateGroupPage() {
+  async function createGroupAction(values: unknown) {
+    'use server'
+    const groupFormValues = groupFormSchema.parse(values)
+    const group = await createGroup(groupFormValues)
+    redirect(`/groups/${group.id}`)
+  }
+
+  return (
+    <main>
+      <div className="mb-4">
+        <Button variant="ghost" asChild>
+          <Link href="/groups">
+            <ChevronLeft className="w-4 h-4 mr-2" /> Back to recent groups
+          </Link>
+        </Button>
+      </div>
+      <GroupForm onSubmit={createGroupAction} />
+    </main>
+  )
+}

src/app/groups/page.tsx

@@ -0,0 +1,14 @@
+import { RecentGroupList } from '@/app/groups/recent-group-list'
+import { Button } from '@/components/ui/button'
+import Link from 'next/link'
+
+export default async function GroupsPage() {
+  return (
+    <main>
+      <Button asChild>
+        <Link href="/groups/create">New group</Link>
+      </Button>
+      <RecentGroupList />
+    </main>
+  )
+}

src/app/groups/recent-group-list.tsx

@@ -0,0 +1,43 @@
+'use client'
+import { getRecentGroups } from '@/app/groups/recent-groups-helpers'
+import { Button } from '@/components/ui/button'
+import Link from 'next/link'
+import { useEffect, useState } from 'react'
+import { z } from 'zod'
+
+const recentGroupsSchema = z.array(
+  z.object({
+    id: z.string().min(1),
+    name: z.string(),
+  }),
+)
+type RecentGroups = z.infer<typeof recentGroupsSchema>
+
+type State = { status: 'pending' } | { status: 'success'; groups: RecentGroups }
+
+export function RecentGroupList() {
+  const [state, setState] = useState<State>({ status: 'pending' })
+
+  useEffect(() => {
+    const groupsInStorage = getRecentGroups()
+    setState({ status: 'success', groups: groupsInStorage })
+  }, [])
+
+  return (
+    <ul className="flex flex-col gap-2 mt-2">
+      {state.status === 'pending' ? (
+        <li>
+          <em>Loading recent groups…</em>
+        </li>
+      ) : (
+        state.groups.map(({ id, name }) => (
+          <li key={id}>
+            <Button asChild variant="outline">
+              <Link href={`/groups/${id}`}>{name}</Link>
+            </Button>
+          </li>
+        ))
+      )}
+    </ul>
+  )
+}

src/app/groups/recent-groups-helpers.ts

@@ -0,0 +1,30 @@
+import { z } from 'zod'
+
+export const recentGroupsSchema = z.array(
+  z.object({
+    id: z.string().min(1),
+    name: z.string(),
+  }),
+)
+
+export type RecentGroups = z.infer<typeof recentGroupsSchema>
+export type RecentGroup = RecentGroups[number]
+
+const STORAGE_KEY = 'recentGroups'
+
+export function getRecentGroups() {
+  const groupsInStorageJson = localStorage.getItem(STORAGE_KEY)
+  const groupsInStorageRaw = groupsInStorageJson
+    ? JSON.parse(groupsInStorageJson)
+    : []
+  const parseResult = recentGroupsSchema.safeParse(groupsInStorageRaw)
+  return parseResult.success ? parseResult.data : []
+}
+
+export function saveRecentGroup(group: RecentGroup) {
+  const recentGroups = getRecentGroups()
+  localStorage.setItem(
+    STORAGE_KEY,
+    JSON.stringify([group, ...recentGroups.filter((rg) => rg.id !== group.id)]),
+  )
+}

src/app/layout.tsx

@@ -1,9 +1,6 @@
 import type { Metadata } from 'next'
-import { Inter } from 'next/font/google'
 import './globals.css'
 
-const inter = Inter({ subsets: ['latin'] })
-
 export const metadata: Metadata = {
   title: 'Create Next App',
   description: 'Generated by create next app',
@@ -16,7 +13,9 @@ export default function RootLayout({
 }) {
   return (
     <html lang="en">
-      <body className={inter.className}>{children}</body>
+      <body>
+        <div className="max-w-screen-md mx-auto p-4">{children}</div>
+      </body>
     </html>
   )
 }

src/app/page.tsx

@@ -1,113 +1,12 @@
-import Image from 'next/image'
+import { Button } from '@/components/ui/button'
+import Link from 'next/link'
 
-export default function Home() {
+export default function HomePage() {
   return (
-    <main className="flex min-h-screen flex-col items-center justify-between p-24">
-      <div className="z-10 max-w-5xl w-full items-center justify-between font-mono text-sm lg:flex">
-        <p className="fixed left-0 top-0 flex w-full justify-center border-b border-gray-300 bg-gradient-to-b from-zinc-200 pb-6 pt-8 backdrop-blur-2xl dark:border-neutral-800 dark:bg-zinc-800/30 dark:from-inherit lg:static lg:w-auto  lg:rounded-xl lg:border lg:bg-gray-200 lg:p-4 lg:dark:bg-zinc-800/30">
-          Get started by editing&nbsp;
-          <code className="font-mono font-bold">src/app/page.tsx</code>
-        </p>
-        <div className="fixed bottom-0 left-0 flex h-48 w-full items-end justify-center bg-gradient-to-t from-white via-white dark:from-black dark:via-black lg:static lg:h-auto lg:w-auto lg:bg-none">
-          <a
-            className="pointer-events-none flex place-items-center gap-2 p-8 lg:pointer-events-auto lg:p-0"
-            href="https://vercel.com?utm_source=create-next-app&utm_medium=appdir-template&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            By{' '}
-            <Image
-              src="/vercel.svg"
-              alt="Vercel Logo"
-              className="dark:invert"
-              width={100}
-              height={24}
-              priority
-            />
-          </a>
-        </div>
-      </div>
-
-      <div className="relative flex place-items-center before:absolute before:h-[300px] before:w-[480px] before:-translate-x-1/2 before:rounded-full before:bg-gradient-radial before:from-white before:to-transparent before:blur-2xl before:content-[''] after:absolute after:-z-20 after:h-[180px] after:w-[240px] after:translate-x-1/3 after:bg-gradient-conic after:from-sky-200 after:via-blue-200 after:blur-2xl after:content-[''] before:dark:bg-gradient-to-br before:dark:from-transparent before:dark:to-blue-700 before:dark:opacity-10 after:dark:from-sky-900 after:dark:via-[#0141ff] after:dark:opacity-40 before:lg:h-[360px] z-[-1]">
-        <Image
-          className="relative dark:drop-shadow-[0_0_0.3rem_#ffffff70] dark:invert"
-          src="/next.svg"
-          alt="Next.js Logo"
-          width={180}
-          height={37}
-          priority
-        />
-      </div>
-
-      <div className="mb-32 grid text-center lg:max-w-5xl lg:w-full lg:mb-0 lg:grid-cols-4 lg:text-left">
-        <a
-          href="https://nextjs.org/docs?utm_source=create-next-app&utm_medium=appdir-template&utm_campaign=create-next-app"
-          className="group rounded-lg border border-transparent px-5 py-4 transition-colors hover:border-gray-300 hover:bg-gray-100 hover:dark:border-neutral-700 hover:dark:bg-neutral-800/30"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <h2 className={`mb-3 text-2xl font-semibold`}>
-            Docs{' '}
-            <span className="inline-block transition-transform group-hover:translate-x-1 motion-reduce:transform-none">
-              -&gt;
-            </span>
-          </h2>
-          <p className={`m-0 max-w-[30ch] text-sm opacity-50`}>
-            Find in-depth information about Next.js features and API.
-          </p>
-        </a>
-
-        <a
-          href="https://nextjs.org/learn?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-          className="group rounded-lg border border-transparent px-5 py-4 transition-colors hover:border-gray-300 hover:bg-gray-100 hover:dark:border-neutral-700 hover:dark:bg-neutral-800/30"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <h2 className={`mb-3 text-2xl font-semibold`}>
-            Learn{' '}
-            <span className="inline-block transition-transform group-hover:translate-x-1 motion-reduce:transform-none">
-              -&gt;
-            </span>
-          </h2>
-          <p className={`m-0 max-w-[30ch] text-sm opacity-50`}>
-            Learn about Next.js in an interactive course with&nbsp;quizzes!
-          </p>
-        </a>
-
-        <a
-          href="https://vercel.com/templates?framework=next.js&utm_source=create-next-app&utm_medium=appdir-template&utm_campaign=create-next-app"
-          className="group rounded-lg border border-transparent px-5 py-4 transition-colors hover:border-gray-300 hover:bg-gray-100 hover:dark:border-neutral-700 hover:dark:bg-neutral-800/30"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <h2 className={`mb-3 text-2xl font-semibold`}>
-            Templates{' '}
-            <span className="inline-block transition-transform group-hover:translate-x-1 motion-reduce:transform-none">
-              -&gt;
-            </span>
-          </h2>
-          <p className={`m-0 max-w-[30ch] text-sm opacity-50`}>
-            Explore the Next.js 13 playground.
-          </p>
-        </a>
-
-        <a
-          href="https://vercel.com/new?utm_source=create-next-app&utm_medium=appdir-template&utm_campaign=create-next-app"
-          className="group rounded-lg border border-transparent px-5 py-4 transition-colors hover:border-gray-300 hover:bg-gray-100 hover:dark:border-neutral-700 hover:dark:bg-neutral-800/30"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <h2 className={`mb-3 text-2xl font-semibold`}>
-            Deploy{' '}
-            <span className="inline-block transition-transform group-hover:translate-x-1 motion-reduce:transform-none">
-              -&gt;
-            </span>
-          </h2>
-          <p className={`m-0 max-w-[30ch] text-sm opacity-50`}>
-            Instantly deploy your Next.js site to a shareable URL with Vercel.
-          </p>
-        </a>
-      </div>
+    <main>
+      <Button asChild variant="link">
+        <Link href="/groups">My groups</Link>
+      </Button>
     </main>
   )
 }

src/components/expense-form.tsx

@@ -0,0 +1,186 @@
+'use client'
+import { Button } from '@/components/ui/button'
+import {
+  Card,
+  CardContent,
+  CardFooter,
+  CardHeader,
+  CardTitle,
+} from '@/components/ui/card'
+import { Checkbox } from '@/components/ui/checkbox'
+import {
+  Form,
+  FormControl,
+  FormDescription,
+  FormField,
+  FormItem,
+  FormLabel,
+  FormMessage,
+} from '@/components/ui/form'
+import { Input } from '@/components/ui/input'
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select'
+import { getExpense, getGroup } from '@/lib/api'
+import { ExpenseFormValues, expenseFormSchema } from '@/lib/schemas'
+import { zodResolver } from '@hookform/resolvers/zod'
+import { useForm } from 'react-hook-form'
+
+export type Props = {
+  group: NonNullable<Awaited<ReturnType<typeof getGroup>>>
+  expense?: NonNullable<Awaited<ReturnType<typeof getExpense>>>
+  onSubmit: (values: ExpenseFormValues) => void
+}
+
+export function ExpenseForm({ group, expense, onSubmit }: Props) {
+  const form = useForm<ExpenseFormValues>({
+    resolver: zodResolver(expenseFormSchema),
+    defaultValues: expense
+      ? {
+          title: expense.title,
+          amount: expense.amount,
+          paidBy: expense.paidById,
+          paidFor: expense.paidFor.map(({ participantId }) => participantId),
+        }
+      : { title: '', amount: 0, paidFor: [] },
+  })
+
+  return (
+    <Form {...form}>
+      <form onSubmit={form.handleSubmit((values) => onSubmit(values))}>
+        <Card>
+          <CardHeader>
+            <CardTitle>Expense information</CardTitle>
+          </CardHeader>
+          <CardContent className="grid grid-cols-2 gap-6">
+            <FormField
+              control={form.control}
+              name="title"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>Expense title</FormLabel>
+                  <FormControl>
+                    <Input placeholder="Monday evening restaurant" {...field} />
+                  </FormControl>
+                  <FormDescription>
+                    Enter a description for the expense.
+                  </FormDescription>
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+
+            <FormField
+              control={form.control}
+              name="paidBy"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>Paid by</FormLabel>
+                  <Select
+                    onValueChange={field.onChange}
+                    defaultValue={field.value}
+                  >
+                    <SelectTrigger>
+                      <SelectValue placeholder="Select a participant" />
+                    </SelectTrigger>
+                    <SelectContent>
+                      {group.participants.map(({ id, name }) => (
+                        <SelectItem key={id} value={id}>
+                          {name}
+                        </SelectItem>
+                      ))}
+                    </SelectContent>
+                  </Select>
+                  <FormDescription>
+                    Select the participant who paid the expense.
+                  </FormDescription>
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+
+            <FormField
+              control={form.control}
+              name="amount"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>Amount</FormLabel>
+                  <FormControl>
+                    <Input
+                      type="number"
+                      min={0.01}
+                      step={0.01}
+                      placeholder="0.00"
+                      {...field}
+                    />
+                  </FormControl>
+                  <FormDescription>Enter the expense amount.</FormDescription>
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+
+            <FormField
+              control={form.control}
+              name="paidFor"
+              render={() => (
+                <FormItem>
+                  <div className="mb-4">
+                    <FormLabel>Paid for</FormLabel>
+                    <FormDescription>
+                      Select who the expense was paid for.
+                    </FormDescription>
+                  </div>
+                  {group.participants.map(({ id, name }) => (
+                    <FormField
+                      key={id}
+                      control={form.control}
+                      name="paidFor"
+                      render={({ field }) => {
+                        return (
+                          <FormItem
+                            key={id}
+                            className="flex flex-row items-start space-x-3 space-y-0"
+                          >
+                            <FormControl>
+                              <Checkbox
+                                checked={field.value?.includes(id)}
+                                onCheckedChange={(checked) => {
+                                  return checked
+                                    ? field.onChange([...field.value, id])
+                                    : field.onChange(
+                                        field.value?.filter(
+                                          (value) => value !== id,
+                                        ),
+                                      )
+                                }}
+                              />
+                            </FormControl>
+                            <FormLabel className="text-sm font-normal">
+                              {name}
+                            </FormLabel>
+                          </FormItem>
+                        )
+                      }}
+                    />
+                  ))}
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+          </CardContent>
+
+          <CardFooter>
+            <Button variant="secondary" type="submit">
+              Submit
+            </Button>
+          </CardFooter>
+        </Card>
+      </form>
+    </Form>
+  )
+}

src/components/group-form.tsx

@@ -0,0 +1,136 @@
+'use client'
+import { Button } from '@/components/ui/button'
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardFooter,
+  CardHeader,
+  CardTitle,
+} from '@/components/ui/card'
+import {
+  Form,
+  FormControl,
+  FormDescription,
+  FormField,
+  FormItem,
+  FormLabel,
+  FormMessage,
+} from '@/components/ui/form'
+import { Input } from '@/components/ui/input'
+import { getGroup } from '@/lib/api'
+import { GroupFormValues, groupFormSchema } from '@/lib/schemas'
+import { zodResolver } from '@hookform/resolvers/zod'
+import { useFieldArray, useForm } from 'react-hook-form'
+
+export type Props = {
+  group?: NonNullable<Awaited<ReturnType<typeof getGroup>>>
+  onSubmit: (groupFormValues: GroupFormValues) => void
+}
+
+export function GroupForm({ group, onSubmit }: Props) {
+  const form = useForm<GroupFormValues>({
+    resolver: zodResolver(groupFormSchema),
+    defaultValues: group
+      ? {
+          name: group.name,
+          participants: group.participants,
+        }
+      : {
+          name: '',
+          participants: [{ name: 'John' }, { name: 'Jane' }, { name: 'Jack' }],
+        },
+  })
+  const { fields, append, remove } = useFieldArray({
+    control: form.control,
+    name: 'participants',
+  })
+
+  return (
+    <Form {...form}>
+      <form
+        onSubmit={form.handleSubmit((values) => {
+          onSubmit(values)
+        })}
+        className="space-y-8"
+      >
+        <Card>
+          <CardHeader>
+            <CardTitle>Group information</CardTitle>
+          </CardHeader>
+          <CardContent>
+            <FormField
+              control={form.control}
+              name="name"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>Group name</FormLabel>
+                  <FormControl>
+                    <Input placeholder="Summer vacations" {...field} />
+                  </FormControl>
+                  <FormDescription>
+                    Enter a name for your group.
+                  </FormDescription>
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+          </CardContent>
+        </Card>
+        <Card>
+          <CardHeader>
+            <CardTitle>Participants</CardTitle>
+            <CardDescription>
+              Enter the name for each participant
+            </CardDescription>
+          </CardHeader>
+          <CardContent>
+            <ul className="flex flex-col gap-4">
+              {fields.map((item, index) => (
+                <li key={item.id}>
+                  <FormField
+                    control={form.control}
+                    name={`participants.${index}.name`}
+                    render={({ field }) => (
+                      <FormItem>
+                        <FormLabel className="sr-only">
+                          Participant #{index + 1}
+                        </FormLabel>
+                        <FormControl>
+                          <div className="flex gap-2">
+                            <Input {...field} />
+                            <Button
+                              variant="destructive"
+                              onClick={() => remove(index)}
+                              type="button"
+                            >
+                              Remove
+                            </Button>
+                          </div>
+                        </FormControl>
+                        <FormMessage />
+                      </FormItem>
+                    )}
+                  />
+                </li>
+              ))}
+            </ul>
+          </CardContent>
+          <CardFooter>
+            <Button
+              variant="secondary"
+              onClick={() => {
+                append({ name: 'New' })
+              }}
+              type="button"
+            >
+              Add participant
+            </Button>
+          </CardFooter>
+        </Card>
+
+        <Button type="submit">Submit</Button>
+      </form>
+    </Form>
+  )
+}

src/components/ui/badge.tsx

@@ -0,0 +1,36 @@
+import * as React from "react"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const badgeVariants = cva(
+  "inline-flex items-center rounded-full border px-2.5 py-0.5 text-xs font-semibold transition-colors focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2",
+  {
+    variants: {
+      variant: {
+        default:
+          "border-transparent bg-primary text-primary-foreground hover:bg-primary/80",
+        secondary:
+          "border-transparent bg-secondary text-secondary-foreground hover:bg-secondary/80",
+        destructive:
+          "border-transparent bg-destructive text-destructive-foreground hover:bg-destructive/80",
+        outline: "text-foreground",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+    },
+  }
+)
+
+export interface BadgeProps
+  extends React.HTMLAttributes<HTMLDivElement>,
+    VariantProps<typeof badgeVariants> {}
+
+function Badge({ className, variant, ...props }: BadgeProps) {
+  return (
+    <div className={cn(badgeVariants({ variant }), className)} {...props} />
+  )
+}
+
+export { Badge, badgeVariants }

src/components/ui/button.tsx

@@ -0,0 +1,56 @@
+import * as React from "react"
+import { Slot } from "@radix-ui/react-slot"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const buttonVariants = cva(
+  "inline-flex items-center justify-center whitespace-nowrap rounded-md text-sm font-medium ring-offset-background transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50",
+  {
+    variants: {
+      variant: {
+        default: "bg-primary text-primary-foreground hover:bg-primary/90",
+        destructive:
+          "bg-destructive text-destructive-foreground hover:bg-destructive/90",
+        outline:
+          "border border-input bg-background hover:bg-accent hover:text-accent-foreground",
+        secondary:
+          "bg-secondary text-secondary-foreground hover:bg-secondary/80",
+        ghost: "hover:bg-accent hover:text-accent-foreground",
+        link: "text-primary underline-offset-4 hover:underline",
+      },
+      size: {
+        default: "h-10 px-4 py-2",
+        sm: "h-9 rounded-md px-3",
+        lg: "h-11 rounded-md px-8",
+        icon: "h-10 w-10",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+      size: "default",
+    },
+  }
+)
+
+export interface ButtonProps
+  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
+    VariantProps<typeof buttonVariants> {
+  asChild?: boolean
+}
+
+const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
+  ({ className, variant, size, asChild = false, ...props }, ref) => {
+    const Comp = asChild ? Slot : "button"
+    return (
+      <Comp
+        className={cn(buttonVariants({ variant, size, className }))}
+        ref={ref}
+        {...props}
+      />
+    )
+  }
+)
+Button.displayName = "Button"
+
+export { Button, buttonVariants }

src/components/ui/card.tsx

@@ -0,0 +1,79 @@
+import * as React from "react"
+
+import { cn } from "@/lib/utils"
+
+const Card = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement>
+>(({ className, ...props }, ref) => (
+  <div
+    ref={ref}
+    className={cn(
+      "rounded-lg border bg-card text-card-foreground shadow-sm",
+      className
+    )}
+    {...props}
+  />
+))
+Card.displayName = "Card"
+
+const CardHeader = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement>
+>(({ className, ...props }, ref) => (
+  <div
+    ref={ref}
+    className={cn("flex flex-col space-y-1.5 p-6", className)}
+    {...props}
+  />
+))
+CardHeader.displayName = "CardHeader"
+
+const CardTitle = React.forwardRef<
+  HTMLParagraphElement,
+  React.HTMLAttributes<HTMLHeadingElement>
+>(({ className, ...props }, ref) => (
+  <h3
+    ref={ref}
+    className={cn(
+      "text-2xl font-semibold leading-none tracking-tight",
+      className
+    )}
+    {...props}
+  />
+))
+CardTitle.displayName = "CardTitle"
+
+const CardDescription = React.forwardRef<
+  HTMLParagraphElement,
+  React.HTMLAttributes<HTMLParagraphElement>
+>(({ className, ...props }, ref) => (
+  <p
+    ref={ref}
+    className={cn("text-sm text-muted-foreground", className)}
+    {...props}
+  />
+))
+CardDescription.displayName = "CardDescription"
+
+const CardContent = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement>
+>(({ className, ...props }, ref) => (
+  <div ref={ref} className={cn("p-6 pt-0", className)} {...props} />
+))
+CardContent.displayName = "CardContent"
+
+const CardFooter = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement>
+>(({ className, ...props }, ref) => (
+  <div
+    ref={ref}
+    className={cn("flex items-center p-6 pt-0", className)}
+    {...props}
+  />
+))
+CardFooter.displayName = "CardFooter"
+
+export { Card, CardHeader, CardFooter, CardTitle, CardDescription, CardContent }

src/components/ui/checkbox.tsx

@@ -0,0 +1,30 @@
+"use client"
+
+import * as React from "react"
+import * as CheckboxPrimitive from "@radix-ui/react-checkbox"
+import { Check } from "lucide-react"
+
+import { cn } from "@/lib/utils"
+
+const Checkbox = React.forwardRef<
+  React.ElementRef<typeof CheckboxPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof CheckboxPrimitive.Root>
+>(({ className, ...props }, ref) => (
+  <CheckboxPrimitive.Root
+    ref={ref}
+    className={cn(
+      "peer h-4 w-4 shrink-0 rounded-sm border border-primary ring-offset-background focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=checked]:text-primary-foreground",
+      className
+    )}
+    {...props}
+  >
+    <CheckboxPrimitive.Indicator
+      className={cn("flex items-center justify-center text-current")}
+    >
+      <Check className="h-4 w-4" />
+    </CheckboxPrimitive.Indicator>
+  </CheckboxPrimitive.Root>
+))
+Checkbox.displayName = CheckboxPrimitive.Root.displayName
+
+export { Checkbox }

src/components/ui/form.tsx

@@ -0,0 +1,176 @@
+import * as React from "react"
+import * as LabelPrimitive from "@radix-ui/react-label"
+import { Slot } from "@radix-ui/react-slot"
+import {
+  Controller,
+  ControllerProps,
+  FieldPath,
+  FieldValues,
+  FormProvider,
+  useFormContext,
+} from "react-hook-form"
+
+import { cn } from "@/lib/utils"
+import { Label } from "@/components/ui/label"
+
+const Form = FormProvider
+
+type FormFieldContextValue<
+  TFieldValues extends FieldValues = FieldValues,
+  TName extends FieldPath<TFieldValues> = FieldPath<TFieldValues>
+> = {
+  name: TName
+}
+
+const FormFieldContext = React.createContext<FormFieldContextValue>(
+  {} as FormFieldContextValue
+)
+
+const FormField = <
+  TFieldValues extends FieldValues = FieldValues,
+  TName extends FieldPath<TFieldValues> = FieldPath<TFieldValues>
+>({
+  ...props
+}: ControllerProps<TFieldValues, TName>) => {
+  return (
+    <FormFieldContext.Provider value={{ name: props.name }}>
+      <Controller {...props} />
+    </FormFieldContext.Provider>
+  )
+}
+
+const useFormField = () => {
+  const fieldContext = React.useContext(FormFieldContext)
+  const itemContext = React.useContext(FormItemContext)
+  const { getFieldState, formState } = useFormContext()
+
+  const fieldState = getFieldState(fieldContext.name, formState)
+
+  if (!fieldContext) {
+    throw new Error("useFormField should be used within <FormField>")
+  }
+
+  const { id } = itemContext
+
+  return {
+    id,
+    name: fieldContext.name,
+    formItemId: `${id}-form-item`,
+    formDescriptionId: `${id}-form-item-description`,
+    formMessageId: `${id}-form-item-message`,
+    ...fieldState,
+  }
+}
+
+type FormItemContextValue = {
+  id: string
+}
+
+const FormItemContext = React.createContext<FormItemContextValue>(
+  {} as FormItemContextValue
+)
+
+const FormItem = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement>
+>(({ className, ...props }, ref) => {
+  const id = React.useId()
+
+  return (
+    <FormItemContext.Provider value={{ id }}>
+      <div ref={ref} className={cn("space-y-2", className)} {...props} />
+    </FormItemContext.Provider>
+  )
+})
+FormItem.displayName = "FormItem"
+
+const FormLabel = React.forwardRef<
+  React.ElementRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root>
+>(({ className, ...props }, ref) => {
+  const { error, formItemId } = useFormField()
+
+  return (
+    <Label
+      ref={ref}
+      className={cn(error && "text-destructive", className)}
+      htmlFor={formItemId}
+      {...props}
+    />
+  )
+})
+FormLabel.displayName = "FormLabel"
+
+const FormControl = React.forwardRef<
+  React.ElementRef<typeof Slot>,
+  React.ComponentPropsWithoutRef<typeof Slot>
+>(({ ...props }, ref) => {
+  const { error, formItemId, formDescriptionId, formMessageId } = useFormField()
+
+  return (
+    <Slot
+      ref={ref}
+      id={formItemId}
+      aria-describedby={
+        !error
+          ? `${formDescriptionId}`
+          : `${formDescriptionId} ${formMessageId}`
+      }
+      aria-invalid={!!error}
+      {...props}
+    />
+  )
+})
+FormControl.displayName = "FormControl"
+
+const FormDescription = React.forwardRef<
+  HTMLParagraphElement,
+  React.HTMLAttributes<HTMLParagraphElement>
+>(({ className, ...props }, ref) => {
+  const { formDescriptionId } = useFormField()
+
+  return (
+    <p
+      ref={ref}
+      id={formDescriptionId}
+      className={cn("text-sm text-muted-foreground", className)}
+      {...props}
+    />
+  )
+})
+FormDescription.displayName = "FormDescription"
+
+const FormMessage = React.forwardRef<
+  HTMLParagraphElement,
+  React.HTMLAttributes<HTMLParagraphElement>
+>(({ className, children, ...props }, ref) => {
+  const { error, formMessageId } = useFormField()
+  const body = error ? String(error?.message) : children
+
+  if (!body) {
+    return null
+  }
+
+  return (
+    <p
+      ref={ref}
+      id={formMessageId}
+      className={cn("text-sm font-medium text-destructive", className)}
+      {...props}
+    >
+      {body}
+    </p>
+  )
+})
+FormMessage.displayName = "FormMessage"
+
+export {
+  useFormField,
+  Form,
+  FormItem,
+  FormLabel,
+  FormControl,
+  FormDescription,
+  FormMessage,
+  FormField,
+}

src/components/ui/input.tsx

@@ -0,0 +1,25 @@
+import * as React from "react"
+
+import { cn } from "@/lib/utils"
+
+export interface InputProps
+  extends React.InputHTMLAttributes<HTMLInputElement> {}
+
+const Input = React.forwardRef<HTMLInputElement, InputProps>(
+  ({ className, type, ...props }, ref) => {
+    return (
+      <input
+        type={type}
+        className={cn(
+          "flex h-10 w-full rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background file:border-0 file:bg-transparent file:text-sm file:font-medium placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50",
+          className
+        )}
+        ref={ref}
+        {...props}
+      />
+    )
+  }
+)
+Input.displayName = "Input"
+
+export { Input }

src/components/ui/label.tsx

@@ -0,0 +1,26 @@
+"use client"
+
+import * as React from "react"
+import * as LabelPrimitive from "@radix-ui/react-label"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const labelVariants = cva(
+  "text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
+)
+
+const Label = React.forwardRef<
+  React.ElementRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root> &
+    VariantProps<typeof labelVariants>
+>(({ className, ...props }, ref) => (
+  <LabelPrimitive.Root
+    ref={ref}
+    className={cn(labelVariants(), className)}
+    {...props}
+  />
+))
+Label.displayName = LabelPrimitive.Root.displayName
+
+export { Label }

src/components/ui/select.tsx

@@ -0,0 +1,160 @@
+"use client"
+
+import * as React from "react"
+import * as SelectPrimitive from "@radix-ui/react-select"
+import { Check, ChevronDown, ChevronUp } from "lucide-react"
+
+import { cn } from "@/lib/utils"
+
+const Select = SelectPrimitive.Root
+
+const SelectGroup = SelectPrimitive.Group
+
+const SelectValue = SelectPrimitive.Value
+
+const SelectTrigger = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.Trigger>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.Trigger>
+>(({ className, children, ...props }, ref) => (
+  <SelectPrimitive.Trigger
+    ref={ref}
+    className={cn(
+      "flex h-10 w-full items-center justify-between rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background placeholder:text-muted-foreground focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 [&>span]:line-clamp-1",
+      className
+    )}
+    {...props}
+  >
+    {children}
+    <SelectPrimitive.Icon asChild>
+      <ChevronDown className="h-4 w-4 opacity-50" />
+    </SelectPrimitive.Icon>
+  </SelectPrimitive.Trigger>
+))
+SelectTrigger.displayName = SelectPrimitive.Trigger.displayName
+
+const SelectScrollUpButton = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.ScrollUpButton>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.ScrollUpButton>
+>(({ className, ...props }, ref) => (
+  <SelectPrimitive.ScrollUpButton
+    ref={ref}
+    className={cn(
+      "flex cursor-default items-center justify-center py-1",
+      className
+    )}
+    {...props}
+  >
+    <ChevronUp className="h-4 w-4" />
+  </SelectPrimitive.ScrollUpButton>
+))
+SelectScrollUpButton.displayName = SelectPrimitive.ScrollUpButton.displayName
+
+const SelectScrollDownButton = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.ScrollDownButton>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.ScrollDownButton>
+>(({ className, ...props }, ref) => (
+  <SelectPrimitive.ScrollDownButton
+    ref={ref}
+    className={cn(
+      "flex cursor-default items-center justify-center py-1",
+      className
+    )}
+    {...props}
+  >
+    <ChevronDown className="h-4 w-4" />
+  </SelectPrimitive.ScrollDownButton>
+))
+SelectScrollDownButton.displayName =
+  SelectPrimitive.ScrollDownButton.displayName
+
+const SelectContent = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.Content>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.Content>
+>(({ className, children, position = "popper", ...props }, ref) => (
+  <SelectPrimitive.Portal>
+    <SelectPrimitive.Content
+      ref={ref}
+      className={cn(
+        "relative z-50 max-h-96 min-w-[8rem] overflow-hidden rounded-md border bg-popover text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
+        position === "popper" &&
+          "data-[side=bottom]:translate-y-1 data-[side=left]:-translate-x-1 data-[side=right]:translate-x-1 data-[side=top]:-translate-y-1",
+        className
+      )}
+      position={position}
+      {...props}
+    >
+      <SelectScrollUpButton />
+      <SelectPrimitive.Viewport
+        className={cn(
+          "p-1",
+          position === "popper" &&
+            "h-[var(--radix-select-trigger-height)] w-full min-w-[var(--radix-select-trigger-width)]"
+        )}
+      >
+        {children}
+      </SelectPrimitive.Viewport>
+      <SelectScrollDownButton />
+    </SelectPrimitive.Content>
+  </SelectPrimitive.Portal>
+))
+SelectContent.displayName = SelectPrimitive.Content.displayName
+
+const SelectLabel = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.Label>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.Label>
+>(({ className, ...props }, ref) => (
+  <SelectPrimitive.Label
+    ref={ref}
+    className={cn("py-1.5 pl-8 pr-2 text-sm font-semibold", className)}
+    {...props}
+  />
+))
+SelectLabel.displayName = SelectPrimitive.Label.displayName
+
+const SelectItem = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.Item>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.Item>
+>(({ className, children, ...props }, ref) => (
+  <SelectPrimitive.Item
+    ref={ref}
+    className={cn(
+      "relative flex w-full cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50",
+      className
+    )}
+    {...props}
+  >
+    <span className="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
+      <SelectPrimitive.ItemIndicator>
+        <Check className="h-4 w-4" />
+      </SelectPrimitive.ItemIndicator>
+    </span>
+
+    <SelectPrimitive.ItemText>{children}</SelectPrimitive.ItemText>
+  </SelectPrimitive.Item>
+))
+SelectItem.displayName = SelectPrimitive.Item.displayName
+
+const SelectSeparator = React.forwardRef<
+  React.ElementRef<typeof SelectPrimitive.Separator>,
+  React.ComponentPropsWithoutRef<typeof SelectPrimitive.Separator>
+>(({ className, ...props }, ref) => (
+  <SelectPrimitive.Separator
+    ref={ref}
+    className={cn("-mx-1 my-1 h-px bg-muted", className)}
+    {...props}
+  />
+))
+SelectSeparator.displayName = SelectPrimitive.Separator.displayName
+
+export {
+  Select,
+  SelectGroup,
+  SelectValue,
+  SelectTrigger,
+  SelectContent,
+  SelectLabel,
+  SelectItem,
+  SelectSeparator,
+  SelectScrollUpButton,
+  SelectScrollDownButton,
+}

src/components/ui/table.tsx

@@ -0,0 +1,117 @@
+import * as React from "react"
+
+import { cn } from "@/lib/utils"
+
+const Table = React.forwardRef<
+  HTMLTableElement,
+  React.HTMLAttributes<HTMLTableElement>
+>(({ className, ...props }, ref) => (
+  <div className="relative w-full overflow-auto">
+    <table
+      ref={ref}
+      className={cn("w-full caption-bottom text-sm", className)}
+      {...props}
+    />
+  </div>
+))
+Table.displayName = "Table"
+
+const TableHeader = React.forwardRef<
+  HTMLTableSectionElement,
+  React.HTMLAttributes<HTMLTableSectionElement>
+>(({ className, ...props }, ref) => (
+  <thead ref={ref} className={cn("[&_tr]:border-b", className)} {...props} />
+))
+TableHeader.displayName = "TableHeader"
+
+const TableBody = React.forwardRef<
+  HTMLTableSectionElement,
+  React.HTMLAttributes<HTMLTableSectionElement>
+>(({ className, ...props }, ref) => (
+  <tbody
+    ref={ref}
+    className={cn("[&_tr:last-child]:border-0", className)}
+    {...props}
+  />
+))
+TableBody.displayName = "TableBody"
+
+const TableFooter = React.forwardRef<
+  HTMLTableSectionElement,
+  React.HTMLAttributes<HTMLTableSectionElement>
+>(({ className, ...props }, ref) => (
+  <tfoot
+    ref={ref}
+    className={cn(
+      "border-t bg-muted/50 font-medium [&>tr]:last:border-b-0",
+      className
+    )}
+    {...props}
+  />
+))
+TableFooter.displayName = "TableFooter"
+
+const TableRow = React.forwardRef<
+  HTMLTableRowElement,
+  React.HTMLAttributes<HTMLTableRowElement>
+>(({ className, ...props }, ref) => (
+  <tr
+    ref={ref}
+    className={cn(
+      "border-b transition-colors hover:bg-muted/50 data-[state=selected]:bg-muted",
+      className
+    )}
+    {...props}
+  />
+))
+TableRow.displayName = "TableRow"
+
+const TableHead = React.forwardRef<
+  HTMLTableCellElement,
+  React.ThHTMLAttributes<HTMLTableCellElement>
+>(({ className, ...props }, ref) => (
+  <th
+    ref={ref}
+    className={cn(
+      "h-12 px-4 text-left align-middle font-medium text-muted-foreground [&:has([role=checkbox])]:pr-0",
+      className
+    )}
+    {...props}
+  />
+))
+TableHead.displayName = "TableHead"
+
+const TableCell = React.forwardRef<
+  HTMLTableCellElement,
+  React.TdHTMLAttributes<HTMLTableCellElement>
+>(({ className, ...props }, ref) => (
+  <td
+    ref={ref}
+    className={cn("p-4 align-middle [&:has([role=checkbox])]:pr-0", className)}
+    {...props}
+  />
+))
+TableCell.displayName = "TableCell"
+
+const TableCaption = React.forwardRef<
+  HTMLTableCaptionElement,
+  React.HTMLAttributes<HTMLTableCaptionElement>
+>(({ className, ...props }, ref) => (
+  <caption
+    ref={ref}
+    className={cn("mt-4 text-sm text-muted-foreground", className)}
+    {...props}
+  />
+))
+TableCaption.displayName = "TableCaption"
+
+export {
+  Table,
+  TableHeader,
+  TableBody,
+  TableFooter,
+  TableHead,
+  TableRow,
+  TableCell,
+  TableCaption,
+}

src/lib/api.ts

@@ -0,0 +1,155 @@
+import { getPrisma } from '@/lib/prisma'
+import { ExpenseFormValues, GroupFormValues } from '@/lib/schemas'
+import { Expense } from '@prisma/client'
+import { v4 as uuidv4 } from 'uuid'
+
+export async function createGroup(groupFormValues: GroupFormValues) {
+  return getPrisma().group.create({
+    data: {
+      id: uuidv4(),
+      name: groupFormValues.name,
+      participants: {
+        createMany: {
+          data: groupFormValues.participants.map(({ name }) => ({
+            id: uuidv4(),
+            name,
+          })),
+        },
+      },
+    },
+    include: { participants: true },
+  })
+}
+
+export async function createExpense(
+  expenseFormValues: ExpenseFormValues,
+  groupId: string,
+): Promise<Expense> {
+  const group = await getGroup(groupId)
+  if (!group) throw new Error(`Invalid group ID: ${groupId}`)
+
+  for (const participant of [
+    expenseFormValues.paidBy,
+    ...expenseFormValues.paidFor,
+  ]) {
+    if (!group.participants.some((p) => p.id === participant))
+      throw new Error(`Invalid participant ID: ${participant}`)
+  }
+
+  return getPrisma().expense.create({
+    data: {
+      id: uuidv4(),
+      groupId,
+      amount: expenseFormValues.amount,
+      title: expenseFormValues.title,
+      paidById: expenseFormValues.paidBy,
+      paidFor: {
+        createMany: {
+          data: expenseFormValues.paidFor.map((paidFor) => ({
+            participantId: paidFor,
+          })),
+        },
+      },
+    },
+  })
+}
+
+export async function updateExpense(
+  groupId: string,
+  expenseId: string,
+  expenseFormValues: ExpenseFormValues,
+) {
+  const group = await getGroup(groupId)
+  if (!group) throw new Error(`Invalid group ID: ${groupId}`)
+
+  const existingExpense = await getExpense(groupId, expenseId)
+  if (!existingExpense) throw new Error(`Invalid expense ID: ${expenseId}`)
+
+  for (const participant of [
+    expenseFormValues.paidBy,
+    ...expenseFormValues.paidFor,
+  ]) {
+    if (!group.participants.some((p) => p.id === participant))
+      throw new Error(`Invalid participant ID: ${participant}`)
+  }
+
+  return getPrisma().expense.update({
+    where: { id: expenseId },
+    data: {
+      amount: expenseFormValues.amount,
+      title: expenseFormValues.title,
+      paidById: expenseFormValues.paidBy,
+      paidFor: {
+        connectOrCreate: expenseFormValues.paidFor.map((paidFor) => ({
+          where: {
+            expenseId_participantId: { expenseId, participantId: paidFor },
+          },
+          create: { participantId: paidFor },
+        })),
+        deleteMany: existingExpense.paidFor.filter(
+          (paidFor) =>
+            !expenseFormValues.paidFor.some(
+              (pf) => pf === paidFor.participantId,
+            ),
+        ),
+      },
+    },
+  })
+}
+
+export async function updateGroup(
+  groupId: string,
+  groupFormValues: GroupFormValues,
+) {
+  const existingGroup = await getGroup(groupId)
+  if (!existingGroup) throw new Error('Invalid group ID')
+
+  return getPrisma().group.update({
+    where: { id: groupId },
+    data: {
+      name: groupFormValues.name,
+      participants: {
+        deleteMany: existingGroup.participants.filter(
+          (p) => !groupFormValues.participants.some((p2) => p2.id === p.id),
+        ),
+        updateMany: groupFormValues.participants
+          .filter((participant) => participant.id !== undefined)
+          .map((participant) => ({
+            where: { id: participant.id },
+            data: {
+              name: participant.name,
+            },
+          })),
+        createMany: {
+          data: groupFormValues.participants
+            .filter((participant) => participant.id === undefined)
+            .map((participant) => ({
+              id: uuidv4(),
+              name: participant.name,
+            })),
+        },
+      },
+    },
+  })
+}
+
+export async function getGroup(groupId: string) {
+  return getPrisma().group.findUnique({
+    where: { id: groupId },
+    include: { participants: true },
+  })
+}
+
+export async function getGroupExpenses(groupId: string) {
+  return getPrisma().expense.findMany({
+    where: { groupId },
+    include: { paidFor: { include: { participant: true } }, paidBy: true },
+  })
+}
+
+export async function getExpense(groupId: string, expenseId: string) {
+  return getPrisma().expense.findUnique({
+    where: { id: expenseId },
+    include: { paidBy: true, paidFor: true },
+  })
+}

src/lib/prisma.ts

@@ -0,0 +1,17 @@
+import { PrismaClient } from '@prisma/client'
+
+let prisma: PrismaClient
+
+export function getPrisma() {
+  if (!prisma) {
+    if (process.env.NODE_ENV === 'production') {
+      prisma = new PrismaClient()
+    } else {
+      if (!(global as any).prisma) {
+        ;(global as any).prisma = new PrismaClient()
+      }
+      prisma = (global as any).prisma
+    }
+  }
+  return prisma
+}

src/lib/schemas.ts

@@ -0,0 +1,50 @@
+import * as z from 'zod'
+
+export const groupFormSchema = z
+  .object({
+    name: z
+      .string()
+      .min(2, 'Enter at least two characters.')
+      .max(50, 'Enter at most 50 characters.'),
+    participants: z
+      .array(
+        z.object({
+          id: z.string().optional(),
+          name: z
+            .string()
+            .min(2, 'Enter at least two characters.')
+            .max(50, 'Enter at most 50 characters.'),
+        }),
+      )
+      .min(1),
+  })
+  .superRefine(({ participants }, ctx) => {
+    participants.forEach((participant, i) => {
+      participants.slice(0, i).forEach((otherParticipant) => {
+        if (otherParticipant.name === participant.name) {
+          ctx.addIssue({
+            code: 'custom',
+            message: 'Another participant already has this name.',
+            path: ['participants', i, 'name'],
+          })
+        }
+      })
+    })
+  })
+
+export type GroupFormValues = z.infer<typeof groupFormSchema>
+
+export const expenseFormSchema = z.object({
+  title: z
+    .string({ required_error: 'Please enter a title.' })
+    .min(2, 'Enter at least two characters.'),
+  amount: z.coerce
+    .number({ required_error: 'You must enter an amount.' })
+    .min(0.01, 'The amount must be higher than 0.01.'),
+  paidBy: z.string({ required_error: 'You must select a participant.' }),
+  paidFor: z
+    .array(z.string())
+    .min(1, 'The expense must be paid for at least 1 participant.'),
+})
+
+export type ExpenseFormValues = z.infer<typeof expenseFormSchema>

src/lib/utils.ts

@@ -0,0 +1,6 @@
+import { type ClassValue, clsx } from "clsx"
+import { twMerge } from "tailwind-merge"
+ 
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs))
+}

start-local-db.sh

@@ -0,0 +1,11 @@
+result=$(docker ps | grep postgres)
+if [ $? -eq 0 ];
+then
+    echo "postgres is already running, doing nothing"
+else
+    echo "postgres is not running, starting it"
+    docker rm postgres --force
+    mkdir -p postgres-data
+    docker run --name postgres -d -p 5432:5432 -e POSTGRES_PASSWORD=1234 -v ./postgres-data:/var/lib/postgresql/data postgres
+    sleep 5 # Wait for postgres to start
+fi

tailwind.config.js

@@ -0,0 +1,76 @@
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+  darkMode: ["class"],
+  content: [
+    './pages/**/*.{ts,tsx}',
+    './components/**/*.{ts,tsx}',
+    './app/**/*.{ts,tsx}',
+    './src/**/*.{ts,tsx}',
+	],
+  theme: {
+    container: {
+      center: true,
+      padding: "2rem",
+      screens: {
+        "2xl": "1400px",
+      },
+    },
+    extend: {
+      colors: {
+        border: "hsl(var(--border))",
+        input: "hsl(var(--input))",
+        ring: "hsl(var(--ring))",
+        background: "hsl(var(--background))",
+        foreground: "hsl(var(--foreground))",
+        primary: {
+          DEFAULT: "hsl(var(--primary))",
+          foreground: "hsl(var(--primary-foreground))",
+        },
+        secondary: {
+          DEFAULT: "hsl(var(--secondary))",
+          foreground: "hsl(var(--secondary-foreground))",
+        },
+        destructive: {
+          DEFAULT: "hsl(var(--destructive))",
+          foreground: "hsl(var(--destructive-foreground))",
+        },
+        muted: {
+          DEFAULT: "hsl(var(--muted))",
+          foreground: "hsl(var(--muted-foreground))",
+        },
+        accent: {
+          DEFAULT: "hsl(var(--accent))",
+          foreground: "hsl(var(--accent-foreground))",
+        },
+        popover: {
+          DEFAULT: "hsl(var(--popover))",
+          foreground: "hsl(var(--popover-foreground))",
+        },
+        card: {
+          DEFAULT: "hsl(var(--card))",
+          foreground: "hsl(var(--card-foreground))",
+        },
+      },
+      borderRadius: {
+        lg: "var(--radius)",
+        md: "calc(var(--radius) - 2px)",
+        sm: "calc(var(--radius) - 4px)",
+      },
+      keyframes: {
+        "accordion-down": {
+          from: { height: 0 },
+          to: { height: "var(--radix-accordion-content-height)" },
+        },
+        "accordion-up": {
+          from: { height: "var(--radix-accordion-content-height)" },
+          to: { height: 0 },
+        },
+      },
+      animation: {
+        "accordion-down": "accordion-down 0.2s ease-out",
+        "accordion-up": "accordion-up 0.2s ease-out",
+      },
+    },
+  },
+  plugins: [require("tailwindcss-animate")],
+}