Implement "infinite scroll" for expenses (#95)

* Extract ExpenseCard vom ExpenseList

* Implement simple pagination of expenses (see #30)

- display only this year's entries by default
- a "Show more" button reveals all expenses

* Turn getPrisma() into constant "prisma"

- getPrisma() is not async and doesn't need to be awaited
- turn getPrisma() into exported constant "prisma"

* Select fields to be returned by getGroupExpenses()

- make JSON more concise and less redundant
- some properties were removed (i.e.instead of "expense.paidById" use "expense.paidBy.id")

* Remove "participants" from ExpenseCard

- no need to search for participant by id to get it's name
- name property is already present in expense

* Add option to fetch a slice of group expenses

- specify offset and length to get expenses for [offset, offset+length[
- add function to get total number of group expenses

* Add api route for client to fetch group expenses

* Remove "Show more" button from expense list

* Implement infinite scroll

- in server component Page
  - only load first 200 expenses max
  - pass preloaded expenses and total count

- in client component ExpenseList, if there are more expenses to show
  - test if there are more expenses
  - append preloading "skeletons" to end of list
  - fetch more expenses when last item in list comes into view
  - after each fetch increase fetch-length by factor 1.5
    - rationale: db fetch usually is not the issue here, the longer the list gets, the longer react needs to redraw

* Use server action instead of api endpoint

* Fixes

---------

Co-authored-by: Sebastien Castiel <sebastien@castiel.me>

src/lib/api.ts

@@ -1,4 +1,4 @@
-import { getPrisma } from '@/lib/prisma'
+import { prisma } from '@/lib/prisma'
 import { ExpenseFormValues, GroupFormValues } from '@/lib/schemas'
 import { Expense } from '@prisma/client'
 import { nanoid } from 'nanoid'
@@ -8,7 +8,6 @@ export function randomId() {
 }
 
 export async function createGroup(groupFormValues: GroupFormValues) {
-  const prisma = await getPrisma()
   return prisma.group.create({
     data: {
       id: randomId(),
@@ -42,7 +41,6 @@ export async function createExpense(
       throw new Error(`Invalid participant ID: ${participant}`)
   }
 
-  const prisma = await getPrisma()
   return prisma.expense.create({
     data: {
       id: randomId(),
@@ -78,7 +76,6 @@ export async function createExpense(
 }
 
 export async function deleteExpense(expenseId: string) {
-  const prisma = await getPrisma()
   await prisma.expense.delete({
     where: { id: expenseId },
     include: { paidFor: true, paidBy: true },
@@ -90,15 +87,14 @@ export async function getGroupExpensesParticipants(groupId: string) {
   return Array.from(
     new Set(
       expenses.flatMap((e) => [
-        e.paidById,
-        ...e.paidFor.map((pf) => pf.participantId),
+        e.paidBy.id,
+        ...e.paidFor.map((pf) => pf.participant.id),
       ]),
     ),
   )
 }
 
 export async function getGroups(groupIds: string[]) {
-  const prisma = await getPrisma()
   return (
     await prisma.group.findMany({
       where: { id: { in: groupIds } },
@@ -129,7 +125,6 @@ export async function updateExpense(
       throw new Error(`Invalid participant ID: ${participant}`)
   }
 
-  const prisma = await getPrisma()
   return prisma.expense.update({
     where: { id: expenseId },
     data: {
@@ -198,7 +193,6 @@ export async function updateGroup(
   const existingGroup = await getGroup(groupId)
   if (!existingGroup) throw new Error('Invalid group ID')
 
-  const prisma = await getPrisma()
   return prisma.group.update({
     where: { id: groupId },
     data: {
@@ -230,7 +224,6 @@ export async function updateGroup(
 }
 
 export async function getGroup(groupId: string) {
-  const prisma = await getPrisma()
   return prisma.group.findUnique({
     where: { id: groupId },
     include: { participants: true },
@@ -238,25 +231,43 @@ export async function getGroup(groupId: string) {
 }
 
 export async function getCategories() {
-  const prisma = await getPrisma()
   return prisma.category.findMany()
 }
 
-export async function getGroupExpenses(groupId: string) {
-  const prisma = await getPrisma()
+export async function getGroupExpenses(
+  groupId: string,
+  options?: { offset: number; length: number },
+) {
   return prisma.expense.findMany({
-    where: { groupId },
-    include: {
-      paidFor: { include: { participant: true } },
-      paidBy: true,
+    select: {
+      amount: true,
       category: true,
+      createdAt: true,
+      expenseDate: true,
+      id: true,
+      isReimbursement: true,
+      paidBy: { select: { id: true, name: true } },
+      paidFor: {
+        select: {
+          participant: { select: { id: true, name: true } },
+          shares: true,
+        },
+      },
+      splitMode: true,
+      title: true,
     },
+    where: { groupId },
     orderBy: [{ expenseDate: 'desc' }, { createdAt: 'desc' }],
+    skip: options && options.offset,
+    take: options && options.length,
   })
 }
 
+export async function getGroupExpenseCount(groupId: string) {
+  return prisma.expense.count({ where: { groupId } })
+}
+
 export async function getExpense(groupId: string, expenseId: string) {
-  const prisma = await getPrisma()
   return prisma.expense.findUnique({
     where: { id: expenseId },
     include: { paidBy: true, paidFor: true, category: true, documents: true },

src/lib/balances.ts

@@ -19,7 +19,7 @@ export function getBalances(
   const balances: Balances = {}
 
   for (const expense of expenses) {
-    const paidBy = expense.paidById
+    const paidBy = expense.paidBy.id
     const paidFors = expense.paidFor
 
     if (!balances[paidBy]) balances[paidBy] = { paid: 0, paidFor: 0, total: 0 }
@@ -31,8 +31,8 @@ export function getBalances(
     )
     let remaining = expense.amount
     paidFors.forEach((paidFor, index) => {
-      if (!balances[paidFor.participantId])
-        balances[paidFor.participantId] = { paid: 0, paidFor: 0, total: 0 }
+      if (!balances[paidFor.participant.id])
+        balances[paidFor.participant.id] = { paid: 0, paidFor: 0, total: 0 }
 
       const isLast = index === paidFors.length - 1
 
@@ -47,7 +47,7 @@ export function getBalances(
         ? remaining
         : (expense.amount * shares) / totalShares
       remaining -= dividedAmount
-      balances[paidFor.participantId].paidFor += dividedAmount
+      balances[paidFor.participant.id].paidFor += dividedAmount
     })
   }
 

src/lib/prisma.ts

@@ -1,20 +1,21 @@
 import { PrismaClient } from '@prisma/client'
 
-let prisma: PrismaClient
+declare const global: Global & { prisma?: PrismaClient }
 
-export async function getPrisma() {
+export let p: PrismaClient = undefined as any as PrismaClient
+
+if (typeof window === 'undefined') {
   // await delay(1000)
-  if (!prisma) {
-    if (process.env.NODE_ENV === 'production') {
-      prisma = new PrismaClient()
-    } else {
-      if (!(global as any).prisma) {
-        ;(global as any).prisma = new PrismaClient({
-          // log: [{ emit: 'stdout', level: 'query' }],
-        })
-      }
-      prisma = (global as any).prisma
+  if (process.env['NODE_ENV'] === 'production') {
+    p = new PrismaClient()
+  } else {
+    if (!global.prisma) {
+      global.prisma = new PrismaClient({
+        // log: [{ emit: 'stdout', level: 'query' }],
+      })
     }
+    p = global.prisma
   }
-  return prisma
 }
+
+export const prisma = p

src/lib/totals.ts

@@ -34,7 +34,7 @@ export function getTotalActiveUserShare(
 
     const paidFors = expense.paidFor
     const userPaidFor = paidFors.find(
-      (paidFor) => paidFor.participantId === activeUserId,
+      (paidFor) => paidFor.participant.id === activeUserId,
     )
 
     if (!userPaidFor) {