From 3eb20bb9add9f10df4d8d78b4651403d0600a432 Mon Sep 17 00:00:00 2001
From: bouzuya <m@bouzuya.net>
Date: Thu, 30 Mar 2023 10:48:55 +0900
Subject: [PATCH] Fix undefined access error

---
 app/accounts/[id]/settings.tsx |  8 ++++++--
 components/AccountContext.tsx  |  2 +-
 lib/account.ts                 | 13 +++++++++++--
 tsconfig.json                  |  1 +
 4 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/app/accounts/[id]/settings.tsx b/app/accounts/[id]/settings.tsx
index 8c086d7..b45dabd 100644
--- a/app/accounts/[id]/settings.tsx
+++ b/app/accounts/[id]/settings.tsx
@@ -5,7 +5,11 @@ import { Divider, List, Text } from "react-native-paper";
 import { useAccount } from "../../../components/AccountContext";
 import { DeleteAccountDialog } from "../../../components/DeleteAccountDialog";
 import { Screen } from "../../../components/Screen";
-import { getLastEventId, listCategory } from "../../../lib/account";
+import {
+  getLastEvent,
+  getLastEventId,
+  listCategory,
+} from "../../../lib/account";
 import { deleteAccountFromLocal } from "../../../lib/account-local-storage";
 
 export default function Settings(): JSX.Element {
@@ -58,7 +62,7 @@ export default function Settings(): JSX.Element {
         <Divider style={{ width: "100%" }} />
         <List.Item
           title="Last updated"
-          description={`${account.events[account.events.length - 1].at}`}
+          description={`${getLastEvent(account).at}`}
           style={{ width: "100%" }}
         />
         <Divider style={{ width: "100%" }} />
diff --git a/components/AccountContext.tsx b/components/AccountContext.tsx
index 178fab0..dfc608b 100644
--- a/components/AccountContext.tsx
+++ b/components/AccountContext.tsx
@@ -51,5 +51,5 @@ export function useAccount(
         .then((account) => setAccount(account));
     }
   }, deps);
-  return [accounts[accountId], setAccount];
+  return [accounts[accountId] ?? null, setAccount];
 }
diff --git a/lib/account.ts b/lib/account.ts
index 2900032..4e3d6f9 100644
--- a/lib/account.ts
+++ b/lib/account.ts
@@ -115,9 +115,16 @@ export const deleteTransaction = (
   return [applyEvent(self, event), event];
 };
 
+// query
+export function getLastEvent(self: Account): AccountEvent {
+  const lastEvent = self.events[self.events.length - 1];
+  if (lastEvent === undefined) throw new Error("assertion error");
+  return lastEvent;
+}
+
 // query
 export const getLastEventId = (self: Account): string => {
-  return self.events[self.events.length - 1].id;
+  return getLastEvent(self).id;
 };
 
 // query
@@ -136,11 +143,13 @@ export const listCategory = (
 
 export const restoreAccount = (events: AccountEvent[]): Account => {
   if (events.length === 0) throw new Error("events is empty");
+  const firstEvent = events[0];
+  if (firstEvent === undefined) throw new Error("assertion error");
   return events
     .slice(1)
     .reduce(
       (state, event) => applyEvent(state, event),
-      applyEvent(null, events[0])
+      applyEvent(null, firstEvent)
     );
 };
 
diff --git a/tsconfig.json b/tsconfig.json
index b9567f6..9437926 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,6 +1,7 @@
 {
   "extends": "expo/tsconfig.base",
   "compilerOptions": {
+    "noUncheckedIndexedAccess": true,
     "strict": true
   }
 }