Queue downloads seperately so we don't overwhelm the app

src/components/App.tsx

@@ -11,6 +11,7 @@ import {
 } from '@react-navigation/native';
 import { useColorScheme } from 'react-native';
 import { ColorSchemeContext, themes } from './Colors';
+import DownloadManager from './DownloadManager';
 // import ErrorReportingAlert from 'utility/ErrorReportingAlert';
 
 export default function App(): JSX.Element {
@@ -41,6 +42,7 @@ export default function App(): JSX.Element {
                 <ColorSchemeContext.Provider value={theme}>
                     <NavigationContainer theme={colorScheme === 'dark' ? DarkTheme : DefaultTheme}>
                         <Routes />
+                        <DownloadManager />
                     </NavigationContainer>
                 </ColorSchemeContext.Provider>
             </PersistGate>

src/components/DownloadIcon.tsx

@@ -1,12 +1,14 @@
 import React, { useEffect, useMemo, useRef } from 'react';
 import { useTypedSelector } from 'store';
 import CloudIcon from 'assets/cloud.svg';
+import CloudDownArrow from 'assets/cloud-down-arrow.svg';
 import CloudExclamationMarkIcon from 'assets/cloud-exclamation-mark.svg';
 import InternalDriveIcon from 'assets/internal-drive.svg';
 import useDefaultStyles from './Colors';
 import { EntityId } from '@reduxjs/toolkit';
 import Svg, { Circle, CircleProps } from 'react-native-svg';
 import { Animated, Easing } from 'react-native';
+import styled from 'styled-components/native';
 
 interface DownloadIconProps {
     trackId: EntityId;
@@ -14,6 +16,17 @@ interface DownloadIconProps {
     fill?: string;
 }
 
+const DownloadContainer = styled.View`
+    position: relative;
+`;
+
+const IconOverlay = styled.View`
+    position: absolute;
+    top: 0;
+    left: 0;
+    transform: scale(0.5);
+`;
+
 function DownloadIcon({ trackId, size = 16, fill }: DownloadIconProps) {
     // determine styles
     const defaultStyles = useDefaultStyles();
@@ -21,6 +34,7 @@ function DownloadIcon({ trackId, size = 16, fill }: DownloadIconProps) {
 
     // Get download icon from state
     const entity = useTypedSelector((state) => state.downloads.entities[trackId]);
+    const isQueued = useTypedSelector((state) => state.downloads.queued.includes(trackId));
 
     // Memoize calculations for radius and circumference of the circle
     const radius = useMemo(() => size / 2, [size]);
@@ -52,28 +66,27 @@ function DownloadIcon({ trackId, size = 16, fill }: DownloadIconProps) {
         return () => offsetAnimation.removeListener(subscription);
     }, [offsetAnimation]);
 
-    if (!entity) {
+    if (!entity && !isQueued) {
         return (
             <CloudIcon width={size} height={size} fill={iconFill} />
         );
     }
 
-    const { isComplete, isFailed } = entity;
+    if (entity?.isComplete) {
-
-    if (isComplete) {
         return (
             <InternalDriveIcon width={size} height={size} fill={iconFill} />
         );
     }
 
-    if (isFailed) {
+    if (entity?.isFailed) {
         return (
             <CloudExclamationMarkIcon width={size} height={size} fill={iconFill} />
         );
     }
 
-    if (!isComplete && !isFailed) {
+    if (isQueued || (!entity?.isFailed && !entity?.isComplete)) {
         return (
+            <DownloadContainer>
                 <Svg width={size} height={size} transform={[{ rotate: '-90deg' }]}>
                     <Circle
                         cx={radius}
@@ -89,6 +102,10 @@ function DownloadIcon({ trackId, size = 16, fill }: DownloadIconProps) {
                         fill='transparent'
                     />
                 </Svg>
+                <IconOverlay>
+                    <CloudDownArrow width={size} height={size} fill={iconFill} />
+                </IconOverlay>
+            </DownloadContainer>
         );
     }
 

src/components/DownloadManager.ts

@@ -0,0 +1,110 @@
+import { EntityId } from '@reduxjs/toolkit';
+import { xor } from 'lodash';
+import { useEffect, useRef, useState } from 'react';
+import { DocumentDirectoryPath, readDir } from 'react-native-fs';
+import { useDispatch } from 'react-redux';
+import { useTypedSelector } from 'store';
+import { completeDownload, downloadTrack } from 'store/downloads/actions';
+
+/**
+ * The maximum number of concurrent downloads we allow to take place at once.
+ * This is hardcoded at 5 for now, but might be extracted to a setting later.
+ */
+const MAX_CONCURRENT_DOWNLOADS = 5;
+
+/**
+ * This is a component that tracks queued downloads, and starts them one-by-one,
+ * so that we don't overload react-native-fs, as well as the render performance.
+ */
+function DownloadManager () {
+    // Retrieve store helpers
+    const { queued, ids } = useTypedSelector((state) => state.downloads);
+    const rehydrated = useTypedSelector((state) => state._persist.rehydrated);
+    const dispatch = useDispatch();
+    
+    // Keep state for the currently active downloads (i.e. the downloads that
+    // have actually been pushed out to react-native-fs).
+    const [hasRehydratedOrphans, setHasRehydratedOrphans] = useState(false);
+    const activeDownloads = useRef(new Set<EntityId>());
+
+    useEffect(() => {
+        // GUARD: Check if the queue is empty
+        if (!queued.length) {
+            // If so, clear any current downloads
+            activeDownloads.current.clear();
+            return;
+        }
+
+        // Apparently, the queue has changed, and we need to manage
+        // First, we pick the first n downloads
+        const queue = queued.slice(0, MAX_CONCURRENT_DOWNLOADS);
+
+        // We then filter for new downloads
+        queue.filter((id) => !activeDownloads.current.has(id))
+            .forEach((id) => {
+                // We dispatch the actual call to start downloading
+                dispatch(downloadTrack(id));
+                // And add it to the active downloads
+                activeDownloads.current.add(id);
+            });
+
+        // Lastly, if something isn't part of the queue, but is of active
+        // downloads, we can assume the download completed.
+        xor(Array.from(activeDownloads.current), queue)
+            .forEach((id) => activeDownloads.current.delete(id));
+
+    }, [queued, dispatch, activeDownloads]);
+
+    useEffect(() => {
+        // GUARD: We only run this functino once
+        if (hasRehydratedOrphans) {
+            return;
+        }
+
+        // GUARD: If the state has not been rehydrated, we cannot check against
+        // the store ids.
+        if (!rehydrated) {
+            return;
+        }
+
+        console.log(ids);
+
+        /**
+         * Whenever the store is cleared, existing downloads get "lost" because
+         * the only reference we have is the store. This function checks for
+         * those lost downloads and adds them to the store
+         */
+        async function hydrateOrphanedDownloads() {
+            // Retrieve all files for this app
+            const files = await readDir(DocumentDirectoryPath);
+
+            // Loop through the mp3 files
+            files.filter((file) => file.isFile() && file.name.endsWith('.mp3'))
+                .forEach((file) => {
+                    const id = file.name.replace('.mp3', '');
+                    console.log(id, ids.includes(id));
+
+                    // GUARD: If the id is already in the store, there's nothing
+                    // left for us to do.
+                    if (ids.includes(id)) {
+                        return;
+                    }
+
+                    // Add the download to the store
+                    dispatch(completeDownload({ 
+                        id,
+                        location: file.path,
+                        size: Number.parseInt(file.size),
+                    }));
+                });
+        }
+        
+        hydrateOrphanedDownloads();
+        setHasRehydratedOrphans(true);
+    }, [rehydrated, ids, hasRehydratedOrphans, dispatch]);
+
+
+    return null;
+}
+
+export default DownloadManager;

src/localisation/lang/nl/locale.json

@@ -51,7 +51,7 @@
     "download-playlist": "Download Playlist",
     "no-downloads": "Je hebt nog geen nummers gedownload",
     "delete-track": "Verwijder Track",
-    "delete-all-tracks": "Verwijder alle nummbers",
+    "delete-all-tracks": "Verwijder alle nummers",
     "delete-album": "Verwijder Album",
     "delete-playlist": "Verwijder Playlist",
     "total-download-size": "Totale grootte downloads",

src/screens/Downloads/index.tsx

@@ -10,7 +10,7 @@ import ArrowClockwise from 'assets/arrow-clockwise.svg';
 import { THEME_COLOR } from 'CONSTANTS';
 import { useDispatch } from 'react-redux';
 import { EntityId } from '@reduxjs/toolkit';
-import { downloadTrack, removeDownloadedTrack } from 'store/downloads/actions';
+import { queueTrackForDownload, removeDownloadedTrack } from 'store/downloads/actions';
 import Button from 'components/Button';
 import { t } from 'i18n-js';
 import DownloadIcon from 'components/DownloadIcon';
@@ -51,7 +51,7 @@ function Downloads() {
 
     // Retry a single failed track
     const retryTrack = useCallback((id: EntityId) => {
-        dispatch(downloadTrack(id));
+        dispatch(queueTrackForDownload(id));
     }, [dispatch]);
 
     // Retry all failed tracks

src/screens/Music/stacks/components/TrackListView.tsx

@@ -20,7 +20,7 @@ import DownloadIcon from 'components/DownloadIcon';
 import CloudDownArrow from 'assets/cloud-down-arrow.svg';
 import Trash from 'assets/trash.svg';
 import { useDispatch } from 'react-redux';
-import { downloadTrack, removeDownloadedTrack } from 'store/downloads/actions';
+import { queueTrackForDownload, removeDownloadedTrack } from 'store/downloads/actions';
 import { selectDownloadedTracks } from 'store/downloads/selectors';
 
 const Screen = Dimensions.get('screen');
@@ -111,7 +111,7 @@ const TrackListView: React.FC<TrackListViewProps> = ({
         navigation.navigate('TrackPopupMenu', { trackId: trackIds[index] }); 
     }, [navigation, trackIds]);
     const downloadAllTracks = useCallback(() => {
-        trackIds.forEach((trackId) => dispatch(downloadTrack(trackId)));
+        trackIds.forEach((trackId) => dispatch(queueTrackForDownload(trackId)));
     }, [dispatch, trackIds]);
     const deleteAllTracks = useCallback(() => {
         downloadedTracks.forEach((trackId) => dispatch(removeDownloadedTrack(trackId)));

src/screens/modals/TrackPopupMenu.tsx

@@ -13,7 +13,7 @@ import TrashIcon from 'assets/trash.svg';
 import Text from 'components/Text';
 import { WrappableButton, WrappableButtonRow } from 'components/WrappableButtonRow';
 import { useDispatch } from 'react-redux';
-import { downloadTrack, removeDownloadedTrack } from 'store/downloads/actions';
+import { queueTrackForDownload, removeDownloadedTrack } from 'store/downloads/actions';
 import usePlayTracks from 'utility/usePlayTracks';
 import { selectIsDownloaded } from 'store/downloads/selectors';
 
@@ -57,7 +57,7 @@ function TrackPopupMenu() {
 
     // Callback for downloading the track
     const handleDownload = useCallback(() => {
-        dispatch(downloadTrack(trackId));
+        dispatch(queueTrackForDownload(trackId));
         closeModal();
     }, [trackId, dispatch, closeModal]);
 

src/store/downloads/actions.ts

@@ -8,6 +8,7 @@ export const downloadAdapter = createEntityAdapter<DownloadEntity>({
     selectId: (entity) => entity.id,
 });
 
+export const queueTrackForDownload = createAction<EntityId>('download/queue');
 export const initializeDownload = createAction<{ id: EntityId, size?: number, jobId?: number }>('download/initialize');
 export const progressDownload = createAction<{ id: EntityId, progress: number, jobId?: number }>('download/progress');
 export const completeDownload = createAction<{ id: EntityId, location: string, size?: number }>('download/complete');
@@ -46,7 +47,7 @@ export const downloadTrack = createAsyncThunk(
 );
 
 export const removeDownloadedTrack = createAsyncThunk(
-    '/downloads/track/remove',
+    '/downloads/remove/track',
     async(id: EntityId) => {
         return unlink(`${DocumentDirectoryPath}/${id}.mp3`);
     }

src/store/downloads/index.ts

@@ -1,15 +1,25 @@
 import { createSlice, Dictionary, EntityId } from '@reduxjs/toolkit';
-import { completeDownload, downloadAdapter, failDownload, initializeDownload, progressDownload, removeDownloadedTrack } from './actions';
+import {
+    completeDownload,
+    downloadAdapter,
+    failDownload,
+    initializeDownload,
+    progressDownload,
+    queueTrackForDownload,
+    removeDownloadedTrack
+} from './actions';
 import { DownloadEntity } from './types';
 
 interface State {
     entities: Dictionary<DownloadEntity>;
     ids: EntityId[];
+    queued: EntityId[];
 }
 
 export const initialState: State = {
     entities: {},
     ids: [],
+    queued: [],
 };
 
 const downloads = createSlice({
@@ -32,6 +42,7 @@ const downloads = createSlice({
             });
         });
         builder.addCase(completeDownload, (state, action) => {
+            // Update the item to be completed
             downloadAdapter.updateOne(state, {
                 id: action.payload.id,
                 changes: {
@@ -40,6 +51,11 @@ const downloads = createSlice({
                     isComplete: true,
                 }
             });
+
+            // Remove the item from the queue
+            const newSet = new Set(state.queued);
+            newSet.delete(action.payload.id);
+            state.queued = Array.from(newSet);
         });
         builder.addCase(failDownload, (state, action) => {
             downloadAdapter.updateOne(state, {
@@ -52,7 +68,17 @@ const downloads = createSlice({
             });
         });
         builder.addCase(removeDownloadedTrack.fulfilled, (state, action) => {
+            // Remove the download if it exists
             downloadAdapter.removeOne(state, action.meta.arg);
+
+            // Remove the item from the queue if it is in there
+            const newSet = new Set(state.queued);
+            newSet.delete(action.meta.arg);
+            state.queued = Array.from(newSet);
+        });
+        builder.addCase(queueTrackForDownload, (state, action) => {
+            const newSet = new Set(state.queued).add(action.payload);
+            state.queued = Array.from(newSet);
         });
     },
 });

src/store/index.ts

@@ -9,10 +9,10 @@ import music, { initialState as musicInitialState } from './music';
 import downloads, { initialState as downloadsInitialState } from './downloads';
 import { PersistState } from 'redux-persist/es/types';
 
-const persistConfig: PersistConfig<AppState> = {
+const persistConfig: PersistConfig<Omit<AppState, '_persist'>> = {
     key: 'root',
     storage: AsyncStorage,
-    version: 1,
+    version: 2,
     stateReconciler: autoMergeLevel2,
     migrate: createMigrate({
         // @ts-expect-error migrations are poorly typed
@@ -23,6 +23,16 @@ const persistConfig: PersistConfig<AppState> = {
                 downloads: downloadsInitialState,
                 music: musicInitialState
             };
+        },
+        // @ts-expect-error migrations are poorly typed
+        2: (state: AppState) => {
+            return {
+                ...state,
+                downloads: {
+                    ...state.downloads,
+                    queued: []
+                }
+            };
         }
     })
 };
@@ -48,7 +58,7 @@ const store = configureStore({
     ),
 });
 
-export type AppState = ReturnType<typeof reducers>;
+export type AppState = ReturnType<typeof reducers> & { _persist: PersistState };
 export type AppDispatch = typeof store.dispatch;
 export type AsyncThunkAPI = { state: AppState, dispatch: AppDispatch };
 export const useTypedSelector: TypedUseSelectorHook<AppState> = useSelector;