Complete Phase C (custom commands & yt-dlp updater) and Phase D (library, UX & notifications)

Phase C had been implemented in the working tree but never committed:
named custom-command templates (CRUD + per-download override), command
preview, and the in-app yt-dlp self-updater.

Phase D adds: history search/kind-filter/multi-select/bulk-delete/
re-download; native OS notifications on completion/failure; a private/
incognito download mode that skips history; settings+template backup/
restore via JSON; and a persistent error log surfaced as a Diagnostics
report in Settings.

See ROADMAP.md for the full per-item breakdown.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/download.ts

@@ -1,19 +1,23 @@
 import { spawn, execFile, type ChildProcess } from 'child_process'
 import { existsSync } from 'fs'
 import { join } from 'path'
-import { app, type WebContents } from 'electron'
+import { app, BrowserWindow, Notification, type WebContents } from 'electron'
 import { getYtdlpPath, getBinDir, getAria2cPath } from './binaries'
 import { getSettings, getDownloadArchivePath } from './settings'
 import { getCookiesFilePath } from './cookies'
+import { listTemplates } from './templates'
 import { assertHttpUrl } from './url'
-import { buildArgs } from './buildArgs'
+import { buildArgs, parseExtraArgs, formatCommandLine } from './buildArgs'
+import { addErrorLog } from './errorlog'
 import {
   IpcChannels,
   type StartDownloadOptions,
   type StartDownloadResult,
+  type CommandPreviewResult,
   type DownloadEvent,
   type DownloadMeta,
-  type DownloadProgress
+  type DownloadProgress,
+  type Settings
 } from '@shared/ipc'
 
 interface ActiveDownload {
@@ -87,6 +91,33 @@ function send(wc: WebContents, ev: DownloadEvent): void {
   if (!wc.isDestroyed()) wc.send(IpcChannels.downloadEvent, ev)
 }
 
+/** Native OS notification on completion/failure, gated by Settings.notifyOnComplete. */
+function notify(wc: WebContents, title: string, body: string): void {
+  if (!getSettings().notifyOnComplete || !Notification.isSupported()) return
+  const n = new Notification({ title, body })
+  n.on('click', () => {
+    if (wc.isDestroyed()) return
+    const win = BrowserWindow.fromWebContents(wc)
+    if (win) {
+      if (win.isMinimized()) win.restore()
+      win.show()
+      win.focus()
+    }
+  })
+  n.show()
+}
+
+function logFailure(opts: StartDownloadOptions, title: string | undefined, error: string): void {
+  addErrorLog({
+    id: opts.id,
+    title,
+    url: opts.url,
+    kind: opts.kind,
+    error,
+    occurredAt: Date.now()
+  })
+}
+
 // --- Best-effort metadata probe (runs alongside the download) ---------------
 
 function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
@@ -122,29 +153,21 @@ function probeMeta(ytdlp: string, url: string): Promise<DownloadMeta | null> {
   })
 }
 
-// --- Public API -------------------------------------------------------------
+// --- Argv construction (shared by startDownload and the command preview) ---
 
-export function startDownload(
-  wc: WebContents,
-  opts: StartDownloadOptions
-): StartDownloadResult {
-  const ytdlp = getYtdlpPath()
-  if (!existsSync(ytdlp)) {
-    return {
-      ok: false,
-      error: `yt-dlp.exe not found at ${ytdlp}\nDrop it into resources/bin/ (see the README there).`
-    }
-  }
-  // Reject anything that isn't an http(s) URL before it reaches yt-dlp's argv.
-  try {
-    assertHttpUrl(opts.url)
-  } catch (e) {
-    return { ok: false, error: (e as Error).message }
-  }
-  if (active.has(opts.id)) {
-    return { ok: false, error: 'A download with this id is already running.' }
+// A per-download override (opts.extraArgs, even '') always wins; otherwise
+// fall back to the persisted default template when custom-command mode is on.
+function resolveExtraArgs(opts: StartDownloadOptions, settings: Settings): string[] {
+  if (opts.extraArgs !== undefined) return parseExtraArgs(opts.extraArgs)
+  if (settings.customCommandEnabled && settings.defaultTemplateId) {
+    const tpl = listTemplates().find((t) => t.id === settings.defaultTemplateId)
+    if (tpl) return parseExtraArgs(tpl.args)
   }
+  return []
+}
 
+/** Resolve settings + per-download overrides into the full yt-dlp argv. */
+export function buildCommand(opts: StartDownloadOptions): string[] {
   const settings = getSettings()
   const outDir = opts.outputDir?.trim() || settings.outputDir || app.getPath('downloads')
   const template = settings.filenameTemplate?.trim() || '%(title)s.%(ext)s'
@@ -168,12 +191,50 @@ export function startDownload(
     restrictFilenames: settings.restrictFilenames,
     downloadArchivePath: settings.downloadArchive ? getDownloadArchivePath() : undefined
   }
+  const extraArgs = resolveExtraArgs(opts, settings)
+  return buildArgs(opts, join(outDir, template), options, getBinDir(), access, extraArgs)
+}
+
+/** Build the exact command line for the current form state, without running it. */
+export function previewCommand(opts: StartDownloadOptions): CommandPreviewResult {
+  try {
+    assertHttpUrl(opts.url)
+  } catch (e) {
+    return { ok: false, error: (e as Error).message }
+  }
+  try {
+    return { ok: true, command: formatCommandLine(getYtdlpPath(), buildCommand(opts)) }
+  } catch (e) {
+    return { ok: false, error: (e as Error).message }
+  }
+}
+
+// --- Public API -------------------------------------------------------------
+
+export function startDownload(
+  wc: WebContents,
+  opts: StartDownloadOptions
+): StartDownloadResult {
+  const ytdlp = getYtdlpPath()
+  if (!existsSync(ytdlp)) {
+    return {
+      ok: false,
+      error: `yt-dlp.exe not found at ${ytdlp}\nDrop it into resources/bin/ (see the README there).`
+    }
+  }
+  // Reject anything that isn't an http(s) URL before it reaches yt-dlp's argv.
+  try {
+    assertHttpUrl(opts.url)
+  } catch (e) {
+    return { ok: false, error: (e as Error).message }
+  }
+  if (active.has(opts.id)) {
+    return { ok: false, error: 'A download with this id is already running.' }
+  }
 
   let child: ChildProcess
   try {
-    child = spawn(ytdlp, buildArgs(opts, join(outDir, template), options, getBinDir(), access), {
-      windowsHide: true
-    })
+    child = spawn(ytdlp, buildCommand(opts), { windowsHide: true })
   } catch (e) {
     return { ok: false, error: (e as Error).message }
   }
@@ -182,7 +243,11 @@ export function startDownload(
   active.set(opts.id, rec)
 
   // Fetch title/channel/duration in parallel so the card fills in quickly.
+  // Also kept locally so the completion notification/error log can show a
+  // real title instead of just the raw URL.
+  let resolvedTitle: string | undefined
   probeMeta(ytdlp, opts.url).then((meta) => {
+    if (meta?.title) resolvedTitle = meta.title
     if (meta && active.has(opts.id)) send(wc, { type: 'meta', id: opts.id, meta })
   })
 
@@ -215,7 +280,11 @@ export function startDownload(
     if (settled) return
     settled = true
     active.delete(opts.id)
-    if (!rec.canceled) send(wc, { type: 'error', id: opts.id, error: err.message })
+    if (!rec.canceled) {
+      send(wc, { type: 'error', id: opts.id, error: err.message })
+      logFailure(opts, resolvedTitle, err.message)
+      notify(wc, resolvedTitle ?? 'Download failed', err.message)
+    }
   })
 
   child.on('close', (code) => {
@@ -225,9 +294,12 @@ export function startDownload(
     if (rec.canceled) return // renderer already showed 'canceled' optimistically
     if (code === 0) {
       send(wc, { type: 'done', id: opts.id, filePath })
+      notify(wc, resolvedTitle ?? 'Download complete', 'Finished downloading.')
     } else {
       const msg = cleanError(stderrTail) || `yt-dlp exited with code ${code}`
       send(wc, { type: 'error', id: opts.id, error: msg })
+      logFailure(opts, resolvedTitle, msg)
+      notify(wc, resolvedTitle ?? 'Download failed', msg)
     }
   })