From 487a130f841ec0ec2546b6bc68d9b0701702cc44 Mon Sep 17 00:00:00 2001
From: Luca Pezzolla <me@lucapezzolla.com>
Date: Thu, 23 Nov 2023 13:20:58 +0100
Subject: [PATCH] refactor(preferences): allow to perform partial key update
 via update callback

Refs #375
---
 src/core/contexts/PreferencesContext.ts       | 29 ++++++++--
 src/core/providers/PreferencesProvider.tsx    | 56 +++++++++++++------
 .../screens/CourseIconPickerScreen.tsx        |  4 +-
 src/features/user/screens/SettingsScreen.tsx  |  6 +-
 4 files changed, 66 insertions(+), 29 deletions(-)

diff --git a/src/core/contexts/PreferencesContext.ts b/src/core/contexts/PreferencesContext.ts
index 76ca597a..c7d42037 100644
--- a/src/core/contexts/PreferencesContext.ts
+++ b/src/core/contexts/PreferencesContext.ts
@@ -42,8 +42,8 @@ export type CoursesPreferences = {
   [courseId: number | string]: CoursePreferencesProps;
 };
 
-export interface PreferencesContextBase {
-  lastInstalledVersion: string | null;
+export interface EditablePreferences {
+  lastInstalledVersion?: string;
   username: string;
   campusId?: string;
   colorScheme: 'light' | 'dark' | 'system';
@@ -76,10 +76,27 @@ export interface PreferencesContextBase {
   };
 }
 
-export interface PreferencesContextProps extends PreferencesContextBase {
-  updatePreference: <T extends PreferenceKey>(
-    key: T,
-    value: PreferencesContextBase[T],
+/**
+ * A callback that receives the previous value of the preference and returns the next one
+ */
+type UpdatePreferenceCallback<
+  K extends PreferenceKey,
+  V extends EditablePreferences[K],
+> = (prev: V | undefined) => V | undefined;
+
+/**
+ * The value of a preference can be:
+ * - a value of the type of the preference
+ * - a callback that receives the previous value of the preference and returns the next one
+ */
+export type UpdatePreferenceValue<K extends PreferenceKey> =
+  | EditablePreferences[K]
+  | UpdatePreferenceCallback<K, EditablePreferences[K]>;
+
+export interface PreferencesContextProps extends EditablePreferences {
+  updatePreference: <K extends PreferenceKey>(
+    key: K,
+    value: UpdatePreferenceValue<K>,
   ) => void;
 }
 
diff --git a/src/core/providers/PreferencesProvider.tsx b/src/core/providers/PreferencesProvider.tsx
index 1cc56121..a4236935 100644
--- a/src/core/providers/PreferencesProvider.tsx
+++ b/src/core/providers/PreferencesProvider.tsx
@@ -3,9 +3,11 @@ import { PropsWithChildren, useEffect, useRef, useState } from 'react';
 import AsyncStorage from '@react-native-async-storage/async-storage';
 
 import {
+  EditablePreferences,
   PreferenceKey,
   PreferencesContext,
   PreferencesContextProps,
+  UpdatePreferenceValue,
   editablePreferenceKeys,
   objectPreferenceKeys,
 } from '../contexts/PreferencesContext';
@@ -15,7 +17,7 @@ export const PreferencesProvider = ({ children }: PropsWithChildren) => {
   const deviceLanguage = useDeviceLanguage();
   const [preferencesContext, setPreferencesContext] =
     useState<PreferencesContextProps>({
-      lastInstalledVersion: null,
+      lastInstalledVersion: undefined,
       username: '',
       colorScheme: 'system',
       courses: {},
@@ -38,35 +40,52 @@ export const PreferencesProvider = ({ children }: PropsWithChildren) => {
 
   const preferencesInitialized = useRef<boolean>(false);
 
-  const updatePreference = (key: PreferenceKey, value: unknown) => {
-    const stringKey = key.toString();
-    if (value === null) {
-      AsyncStorage.removeItem(stringKey).then(() =>
-        setPreferencesContext(oldP => ({
-          ...oldP,
-          [stringKey]: value,
-        })),
-      );
-    } else {
+  // Initialize preferences from AsyncStorage
+  useEffect(() => {
+    const updatePreference = <K extends PreferenceKey>(
+      key: K,
+      value: UpdatePreferenceValue<K>,
+    ) => {
+      const stringKey = key.toString();
+
+      // if value is undefined, remove the preference
+      if (value === undefined) {
+        AsyncStorage.removeItem(stringKey).then(() =>
+          setPreferencesContext(oldP => ({
+            ...oldP,
+            [stringKey]: value,
+          })),
+        );
+
+        return;
+      }
+
       let storageValue: string;
+      let nextValue: EditablePreferences[PreferenceKey];
 
+      // if value is a callback, call it with the current value
+      if (typeof value === 'function') {
+        const currentValue = preferencesContext[key];
+        nextValue = value(currentValue);
+      } else {
+        nextValue = value;
+      }
+
+      // if value is an object, stringify it
       if (objectPreferenceKeys.includes(key)) {
-        storageValue = JSON.stringify(value);
+        storageValue = JSON.stringify(nextValue);
       } else {
-        storageValue = value as string;
+        storageValue = nextValue as string;
       }
 
       AsyncStorage.setItem(stringKey, storageValue).then(() =>
         setPreferencesContext(oldP => ({
           ...oldP,
-          [stringKey]: value,
+          [stringKey]: nextValue,
         })),
       );
-    }
-  };
+    };
 
-  // Initialize preferences from AsyncStorage
-  useEffect(() => {
     AsyncStorage.multiGet(editablePreferenceKeys).then(storagePreferences => {
       const preferences: Partial<PreferencesContextProps> = {
         updatePreference,
@@ -90,6 +109,7 @@ export const PreferencesProvider = ({ children }: PropsWithChildren) => {
         return { ...oldP, ...preferences };
       });
     });
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- only on mount
   }, []);
 
   // Preferences are loaded
diff --git a/src/features/courses/screens/CourseIconPickerScreen.tsx b/src/features/courses/screens/CourseIconPickerScreen.tsx
index 1c3d5080..3e292906 100644
--- a/src/features/courses/screens/CourseIconPickerScreen.tsx
+++ b/src/features/courses/screens/CourseIconPickerScreen.tsx
@@ -9,7 +9,7 @@ import { NativeStackScreenProps } from '@react-navigation/native-stack';
 
 import { BottomBarSpacer } from '../../../core/components/BottomBarSpacer';
 import {
-  PreferencesContextBase,
+  EditablePreferences,
   usePreferencesContext,
 } from '../../../core/contexts/PreferencesContext';
 import { useSafeAreaSpacing } from '../../../core/hooks/useSafeAreaSpacing';
@@ -96,7 +96,7 @@ export const CourseIconPickerScreen = ({ navigation, route }: Props) => {
                 ...coursePrefs,
                 icon: null,
               },
-            } as PreferencesContextBase['courses']);
+            } as EditablePreferences['courses']);
             navigation.goBack();
           }}
         />
diff --git a/src/features/user/screens/SettingsScreen.tsx b/src/features/user/screens/SettingsScreen.tsx
index b3827ed3..9dab92b9 100644
--- a/src/features/user/screens/SettingsScreen.tsx
+++ b/src/features/user/screens/SettingsScreen.tsx
@@ -37,7 +37,7 @@ import { version } from '../../../../package.json';
 import { BottomBarSpacer } from '../../../core/components/BottomBarSpacer';
 import { useFeedbackContext } from '../../../core/contexts/FeedbackContext';
 import {
-  PreferencesContextBase,
+  EditablePreferences,
   usePreferencesContext,
 } from '../../../core/contexts/PreferencesContext';
 import { useConfirmationDialog } from '../../../core/hooks/useConfirmationDialog';
@@ -178,7 +178,7 @@ const VisualizationListItem = () => {
       onPressAction={({ nativeEvent: { event } }) => {
         updatePreference(
           'colorScheme',
-          event as PreferencesContextBase['colorScheme'],
+          event as EditablePreferences['colorScheme'],
         );
       }}
     >
@@ -247,7 +247,7 @@ const Notifications = () => {
       updatePreference('notifications', {
         ...notifications,
         [notificationType]: value,
-      } as PreferencesContextBase['notifications']);
+      } as EditablePreferences['notifications']);
     };
 
   return (