code refactoring, backend code optimization

frontend/src/atoms/downloads.ts

@@ -1,7 +1,22 @@
-import { atom } from 'recoil'
+import * as O from 'fp-ts/Option'
+import { pipe } from 'fp-ts/lib/function'
+import { atom, selector } from 'recoil'
 import { RPCResult } from '../types'
 
-export const activeDownloadsState = atom<RPCResult[] | undefined>({
-  key: 'activeDownloadsState',
-  default: undefined
+export const downloadsState = atom<O.Option<RPCResult[]>>({
+  key: 'downloadsState',
+  default: O.none
+})
+
+export const loadingDownloadsState = selector<boolean>({
+  key: 'loadingDownloadsState',
+  get: ({ get }) => O.isNone(get(downloadsState))
+})
+
+export const activeDownloadsState = selector<RPCResult[]>({
+  key: 'activeDownloadsState',
+  get: ({ get }) => pipe(
+    get(downloadsState),
+    O.getOrElse(() => new Array<RPCResult>())
+  )
 })

frontend/src/components/Downloads.tsx

@@ -1,6 +1,6 @@
 import { useEffect } from 'react'
 import { useRecoilState, useRecoilValue } from 'recoil'
-import { activeDownloadsState } from '../atoms/downloads'
+import { loadingDownloadsState } from '../atoms/downloads'
 import { listViewState } from '../atoms/settings'
 import { loadingAtom } from '../atoms/ui'
 import DownloadsCardView from './DownloadsCardView'
@@ -8,15 +8,17 @@ import DownloadsListView from './DownloadsListView'
 
 const Downloads: React.FC = () => {
   const listView = useRecoilValue(listViewState)
-  const active = useRecoilValue(activeDownloadsState)
+  const loadingDownloads = useRecoilValue(loadingDownloadsState)
 
   const [isLoading, setIsLoading] = useRecoilState(loadingAtom)
 
   useEffect(() => {
-    if (active) {
-      setIsLoading(false)
+    if (loadingDownloads) {
+      setIsLoading(true)
+      return
     }
-  }, [active?.length, isLoading])
+    setIsLoading(false)
+  }, [loadingDownloads, isLoading])
 
   if (listView) {
     return (

frontend/src/components/DownloadsCardView.tsx

@@ -7,7 +7,7 @@ import { useRPC } from '../hooks/useRPC'
 import DownloadCard from './DownloadCard'
 
 const DownloadsCardView: React.FC = () => {
-  const downloads = useRecoilValue(activeDownloadsState) ?? []
+  const downloads = useRecoilValue(activeDownloadsState)
 
   const { i18n } = useI18n()
   const { client } = useRPC()

frontend/src/components/DownloadsListView.tsx

@@ -18,7 +18,7 @@ import { ellipsis, formatSpeedMiB, roundMiB } from "../utils"
 
 
 const DownloadsListView: React.FC = () => {
-  const downloads = useRecoilValue(activeDownloadsState) ?? []
+  const downloads = useRecoilValue(activeDownloadsState)
 
   const { client } = useRPC()
 

frontend/src/components/SocketSubscriber.tsx

@@ -1,7 +1,8 @@
+import * as O from 'fp-ts/Option'
 import { useMemo } from 'react'
 import { useRecoilState, useRecoilValue } from 'recoil'
 import { interval, share, take } from 'rxjs'
-import { activeDownloadsState } from '../atoms/downloads'
+import { downloadsState } from '../atoms/downloads'
 import { serverAddressAndPortState } from '../atoms/settings'
 import { connectedState } from '../atoms/status'
 import { useSubscription } from '../hooks/observable'
@@ -14,7 +15,7 @@ interface Props extends React.HTMLAttributes<HTMLBaseElement> { }
 
 const SocketSubscriber: React.FC<Props> = ({ children }) => {
   const [, setIsConnected] = useRecoilState(connectedState)
-  const [, setActive] = useRecoilState(activeDownloadsState)
+  const [, setDownloads] = useRecoilState(downloadsState)
 
   const serverAddressAndPort = useRecoilValue(serverAddressAndPortState)
 
@@ -38,14 +39,18 @@ const SocketSubscriber: React.FC<Props> = ({ children }) => {
       if (!isRPCResponse(event)) { return }
       if (!Array.isArray(event.result)) { return }
 
-      setActive(
-        (event.result || [])
-          .filter(f => !!f.info.url)
-          .sort((a, b) => datetimeCompareFunc(
-            b.info.created_at,
-            a.info.created_at,
-          ))
-      )
+      if (event.result) {
+        return setDownloads(
+          O.of(event.result
+            .filter(f => !!f.info.url).sort((a, b) => datetimeCompareFunc(
+              b.info.created_at,
+              a.info.created_at,
+            ))
+          )
+        )
+      }
+
+      setDownloads(O.none)
     },
     (err) => {
       console.error(err)

server/internal/process.go

@@ -17,6 +17,7 @@ import (
 	"github.com/marcopeocchi/fazzoletti/slices"
 	"github.com/marcopeocchi/yt-dlp-web-ui/server/cli"
 	"github.com/marcopeocchi/yt-dlp-web-ui/server/config"
+	"github.com/marcopeocchi/yt-dlp-web-ui/server/rx"
 )
 
 const template = `download:
@@ -81,6 +82,7 @@ func (p *Process) Start() {
 	if p.Output.Path != "" {
 		out.Path = p.Output.Path
 	}
+
 	if p.Output.Filename != "" {
 		out.Filename = p.Output.Filename + ".%(ext)s"
 	}
@@ -113,11 +115,11 @@ func (p *Process) Start() {
 
 	p.proc = cmd.Process
 
-	// ----------------- info block ----------------- //
-	// spawn a goroutine that retrieves the info for the download
-
 	// --------------- progress block --------------- //
-	// unbuffered channel connected to stdout
+	var (
+		sourceChan = make(chan []byte)
+		doneChan   = make(chan struct{})
+	)
 
 	// spawn a goroutine that does the dirty job of parsing the stdout
 	// filling the channel with as many stdout line as yt-dlp produces (producer)
@@ -125,9 +127,19 @@ func (p *Process) Start() {
 		defer func() {
 			r.Close()
 			p.Complete()
+			doneChan <- struct{}{}
+			close(sourceChan)
+			close(doneChan)
 		}()
 
 		for scan.Scan() {
+			sourceChan <- scan.Bytes()
+		}
+	}()
+
+	// Slows down the unmarshal operation to every 500ms
+	go func() {
+		rx.Sample(time.Millisecond*500, sourceChan, doneChan, func(event []byte) {
 			stdout := ProgressTemplate{}
 			err := json.Unmarshal(scan.Bytes(), &stdout)
 			if err == nil {
@@ -143,7 +155,7 @@ func (p *Process) Start() {
 					p.Url, stdout.Percentage,
 				)
 			}
-		}
+		})
 	}()
 
 	// ------------- end progress block ------------- //

server/rx/extensions.go

@@ -2,47 +2,19 @@ package rx
 
 import "time"
 
-/*
-	Package rx contains:
-	-	Definitions for common reactive programming functions/patterns
-*/
-
-// ReactiveX inspired debounce function.
-//
-// Debounce emits a string from the source channel only after a particular
-// time span determined a Go Interval
-//
-// --A--B--CD--EFG-------|>
-//
-//	-t->                 |>
-//	       -t->          |>   t is a timer tick
-//	             -t->    |>
-//
-// --A-----C-----G-------|>
-func Debounce(interval time.Duration, source chan string, f func(emit string)) {
-	var item string
-	timer := time.NewTimer(interval)
-	for {
-		select {
-		case item = <-source:
-			timer.Reset(interval)
-		case <-timer.C:
-			if item != "" {
-				f(item)
-			}
-		}
-	}
-}
-
 // ReactiveX inspired sample function.
 //
 // Debounce emits the most recently emitted value from the source
 // withing the timespan set by the span time.Duration
-func Sample[T any](span time.Duration, source chan T, cb func(emit T)) {
-	timer := time.NewTimer(span)
+func Sample[T any](span time.Duration, source chan T, done chan struct{}, fn func(e T)) {
+	ticker := time.NewTicker(span)
 	for {
-		<-timer.C
-		cb(<-source)
-		timer.Reset(span)
+		select {
+		case <-ticker.C:
+			fn(<-source)
+		case <-done:
+			ticker.Stop()
+			return
+		}
 	}
 }