Add the Rust/egui app sources

- library.rs: scans channels/<name>/ into channels + videos by filename stem
- downloader.rs: runs yt-dlp in a background thread, streams progress to the UI
- app.rs / main.rs: channel sidebar, searchable thumbnail list, detail/description
  panel, downloads panel; plays videos via mpv (falls back to xdg-open)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/app.rs

@@ -0,0 +1,511 @@
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+use eframe::egui;
+
+use crate::downloader::{Downloader, JobState};
+use crate::library::{self, Channel, Video};
+
+/// Flattened, cheap-to-clone view of one video for a single frame of rendering.
+struct Card {
+    channel_idx: usize,
+    video_idx: usize,
+    channel_name: String,
+    title: String,
+    id: String,
+    video_path: Option<PathBuf>,
+    thumb_path: Option<PathBuf>,
+    has_live_chat: bool,
+}
+
+pub struct App {
+    channels_root: PathBuf,
+    library: Vec<Channel>,
+    selected_channel: Option<usize>,
+    selected_video: Option<(usize, usize)>,
+    search: String,
+    downloader: Downloader,
+    show_downloads: bool,
+    dl_url: String,
+    dl_dir: String,
+    /// Decoded thumbnails. `None` means "tried and failed / not loadable".
+    textures: HashMap<PathBuf, Option<egui::TextureHandle>>,
+    /// How many new thumbnails we're still allowed to decode this frame.
+    decode_budget: u32,
+    desc_cache: HashMap<PathBuf, String>,
+    status: String,
+}
+
+impl App {
+    pub fn new(cc: &eframe::CreationContext<'_>) -> Self {
+        cc.egui_ctx.set_visuals(egui::Visuals::dark());
+        let cwd = std::env::current_dir().unwrap_or_else(|_| PathBuf::from("."));
+        let channels_root = cwd.join("channels");
+        let _ = std::fs::create_dir_all(&channels_root);
+        let library = library::scan_channels(&channels_root);
+        let status = format!(
+            "{} channels, {} videos",
+            library.len(),
+            library.iter().map(|c| c.videos.len()).sum::<usize>()
+        );
+        Self {
+            channels_root: channels_root.clone(),
+            library,
+            selected_channel: None,
+            selected_video: None,
+            search: String::new(),
+            downloader: Downloader::new(channels_root),
+            show_downloads: false,
+            dl_url: String::new(),
+            dl_dir: String::new(),
+            textures: HashMap::new(),
+            decode_budget: 0,
+            desc_cache: HashMap::new(),
+            status,
+        }
+    }
+
+    fn rescan(&mut self) {
+        self.library = library::scan_channels(&self.channels_root);
+        self.selected_channel = None;
+        self.selected_video = None;
+        self.desc_cache.clear();
+        self.status = format!(
+            "Rescanned: {} channels, {} videos",
+            self.library.len(),
+            self.library.iter().map(|c| c.videos.len()).sum::<usize>()
+        );
+    }
+
+    fn cards(&self) -> Vec<Card> {
+        let query = self.search.trim().to_lowercase();
+        let mut cards = Vec::new();
+        for (ci, channel) in self.library.iter().enumerate() {
+            if let Some(sel) = self.selected_channel {
+                if sel != ci {
+                    continue;
+                }
+            }
+            for (vi, v) in channel.videos.iter().enumerate() {
+                if !query.is_empty()
+                    && !v.title.to_lowercase().contains(&query)
+                    && !v.id.to_lowercase().contains(&query)
+                {
+                    continue;
+                }
+                cards.push(Card {
+                    channel_idx: ci,
+                    video_idx: vi,
+                    channel_name: channel.name.clone(),
+                    title: v.title.clone(),
+                    id: v.id.clone(),
+                    video_path: v.video_path.clone(),
+                    thumb_path: v.thumb_path.clone(),
+                    has_live_chat: v.has_live_chat,
+                });
+            }
+        }
+        cards
+    }
+
+    fn texture(&mut self, ctx: &egui::Context, path: &Path) -> Option<egui::TextureHandle> {
+        if let Some(slot) = self.textures.get(path) {
+            return slot.clone();
+        }
+        if self.decode_budget == 0 {
+            ctx.request_repaint();
+            return None;
+        }
+        self.decode_budget -= 1;
+        let handle = decode_thumbnail(ctx, path);
+        self.textures.insert(path.to_path_buf(), handle.clone());
+        handle
+    }
+
+    fn description(&mut self, video: &Video) -> String {
+        let Some(path) = &video.description_path else {
+            return "(no description file)".to_string();
+        };
+        if let Some(text) = self.desc_cache.get(path) {
+            return text.clone();
+        }
+        let text = std::fs::read_to_string(path)
+            .unwrap_or_else(|e| format!("(could not read description: {e})"));
+        self.desc_cache.insert(path.clone(), text.clone());
+        text
+    }
+
+    fn play(&mut self, path: &Path) {
+        match Command::new("mpv").arg(path).spawn() {
+            Ok(_) => self.status = format!("Playing {}", file_label(path)),
+            Err(_) => match Command::new("xdg-open").arg(path).spawn() {
+                Ok(_) => self.status = format!("Opened {} in default player", file_label(path)),
+                Err(e) => self.status = format!("Couldn't open {}: {e}", file_label(path)),
+            },
+        }
+    }
+
+    fn open_in_file_manager(&mut self, path: &Path) {
+        let target = if path.is_dir() {
+            path
+        } else {
+            path.parent().unwrap_or(path)
+        };
+        match Command::new("xdg-open").arg(target).spawn() {
+            Ok(_) => {}
+            Err(e) => self.status = format!("Couldn't open folder: {e}"),
+        }
+    }
+
+    fn top_bar(&mut self, ctx: &egui::Context) {
+        egui::TopBottomPanel::top("top_bar").show(ctx, |ui| {
+            ui.add_space(2.0);
+            ui.horizontal(|ui| {
+                ui.heading("YouTube Backup");
+                ui.separator();
+                ui.label("🔍");
+                ui.add(
+                    egui::TextEdit::singleline(&mut self.search)
+                        .hint_text("filter by title or id")
+                        .desired_width(260.0),
+                );
+                if !self.search.is_empty() && ui.button("✖").on_hover_text("clear").clicked() {
+                    self.search.clear();
+                }
+                ui.separator();
+                if ui.button("⟳ Rescan").clicked() {
+                    self.rescan();
+                }
+                let dl_label = if self.show_downloads {
+                    "⬇ Downloads ▸"
+                } else {
+                    "⬇ Downloads"
+                };
+                if ui.selectable_label(self.show_downloads, dl_label).clicked() {
+                    self.show_downloads = !self.show_downloads;
+                }
+                ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                    ui.label(egui::RichText::new(&self.status).weak());
+                });
+            });
+            ui.add_space(2.0);
+        });
+    }
+
+    fn channel_panel(&mut self, ctx: &egui::Context) {
+        egui::SidePanel::left("channels")
+            .resizable(true)
+            .default_width(230.0)
+            .show(ctx, |ui| {
+                ui.add_space(4.0);
+                ui.heading("Channels");
+                ui.separator();
+                egui::ScrollArea::vertical().show(ui, |ui| {
+                    let total: usize = self.library.iter().map(|c| c.videos.len()).sum();
+                    if ui
+                        .selectable_label(self.selected_channel.is_none(), format!("⊞ All  ({total})"))
+                        .clicked()
+                    {
+                        self.selected_channel = None;
+                        self.selected_video = None;
+                    }
+                    ui.separator();
+                    for (i, channel) in self.library.iter().enumerate() {
+                        let label = format!("{}  ({})", channel.name, channel.videos.len());
+                        if ui
+                            .selectable_label(self.selected_channel == Some(i), label)
+                            .on_hover_text(channel.path.display().to_string())
+                            .clicked()
+                        {
+                            self.selected_channel = Some(i);
+                            self.selected_video = None;
+                        }
+                    }
+                });
+            });
+    }
+
+    fn downloads_panel(&mut self, ctx: &egui::Context) {
+        egui::SidePanel::right("downloads")
+            .resizable(true)
+            .default_width(380.0)
+            .show(ctx, |ui| {
+                ui.add_space(4.0);
+                ui.heading("New download");
+                ui.label("Video, playlist, or channel URL:");
+                ui.add(
+                    egui::TextEdit::singleline(&mut self.dl_url)
+                        .hint_text("https://www.youtube.com/…")
+                        .desired_width(f32::INFINITY),
+                );
+                ui.horizontal(|ui| {
+                    ui.label("Save into  channels/");
+                    ui.add(
+                        egui::TextEdit::singleline(&mut self.dl_dir)
+                            .hint_text("folder_name")
+                            .desired_width(170.0),
+                    );
+                });
+                let ready = !self.dl_url.trim().is_empty() && !self.dl_dir.trim().is_empty();
+                if ui
+                    .add_enabled(ready, egui::Button::new("⬇  Start download"))
+                    .clicked()
+                {
+                    let url = self.dl_url.trim().to_string();
+                    let dir = self.dl_dir.trim().to_string();
+                    self.downloader.start(url, dir.clone());
+                    self.status = format!("Downloading into channels/{dir}");
+                }
+                ui.separator();
+                ui.horizontal(|ui| {
+                    ui.heading("Jobs");
+                    if !self.downloader.jobs.is_empty()
+                        && !self.downloader.any_running()
+                        && ui.button("Clear finished").clicked()
+                    {
+                        self.downloader
+                            .jobs
+                            .retain(|j| j.state == JobState::Running);
+                    }
+                });
+                if self.downloader.jobs.is_empty() {
+                    ui.label(egui::RichText::new("Nothing queued yet.").weak());
+                }
+                egui::ScrollArea::vertical().show(ui, |ui| {
+                    for job in self.downloader.jobs.iter().rev() {
+                        let (text, color) = match job.state {
+                            JobState::Running => ("running", egui::Color32::from_rgb(230, 200, 60)),
+                            JobState::Done => ("done", egui::Color32::from_rgb(110, 200, 110)),
+                            JobState::Failed => ("failed", egui::Color32::from_rgb(220, 110, 110)),
+                        };
+                        ui.group(|ui| {
+                            ui.horizontal(|ui| {
+                                ui.colored_label(color, text);
+                                ui.label(format!("→ channels/{}", job.dir_name));
+                            });
+                            ui.label(egui::RichText::new(&job.url).small().weak());
+                            if job.state == JobState::Running {
+                                ui.add(egui::ProgressBar::new(job.progress).show_percentage());
+                            }
+                            let last = job.log.last().map(String::as_str).unwrap_or("");
+                            if !last.is_empty() {
+                                ui.label(egui::RichText::new(last).small().monospace());
+                            }
+                            ui.collapsing("output log", |ui| {
+                                egui::ScrollArea::vertical()
+                                    .max_height(180.0)
+                                    .auto_shrink([false, true])
+                                    .stick_to_bottom(true)
+                                    .show(ui, |ui| {
+                                        for line in &job.log {
+                                            ui.label(
+                                                egui::RichText::new(line).small().monospace(),
+                                            );
+                                        }
+                                    });
+                            });
+                        });
+                    }
+                });
+            });
+    }
+
+    fn detail_panel(&mut self, ctx: &egui::Context) {
+        let Some((ci, vi)) = self.selected_video else {
+            return;
+        };
+        let Some(video) = self.library.get(ci).and_then(|c| c.videos.get(vi)).cloned() else {
+            self.selected_video = None;
+            return;
+        };
+        egui::TopBottomPanel::bottom("detail")
+            .resizable(true)
+            .default_height(220.0)
+            .min_height(80.0)
+            .show(ctx, |ui| {
+                ui.add_space(4.0);
+                ui.horizontal(|ui| {
+                    ui.heading(&video.title);
+                    if video.video_path.is_some() && ui.button("▶ Play").clicked() {
+                        if let Some(p) = video.video_path.clone() {
+                            self.play(&p);
+                        }
+                    }
+                    if let Some(p) = video.video_path.clone() {
+                        if ui.button("📁 Show file").clicked() {
+                            self.open_in_file_manager(&p);
+                        }
+                    }
+                    if video.has_live_chat {
+                        ui.label(egui::RichText::new("💬 has live chat").small().weak());
+                    }
+                    ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                        ui.label(egui::RichText::new(format!("id: {}", video.id)).monospace().weak());
+                        if ui.button("✖ close").clicked() {
+                            self.selected_video = None;
+                        }
+                    });
+                });
+                ui.separator();
+                let description = self.description(&video);
+                egui::ScrollArea::vertical().auto_shrink([false, false]).show(ui, |ui| {
+                    ui.add(egui::Label::new(description).wrap());
+                });
+            });
+    }
+
+    fn video_list(&mut self, ctx: &egui::Context, ui: &mut egui::Ui) {
+        let cards = self.cards();
+        let show_channel = self.selected_channel.is_none();
+        ui.horizontal(|ui| {
+            ui.label(format!("{} videos", cards.len()));
+            if !self.search.trim().is_empty() {
+                ui.label(egui::RichText::new(format!("(filtered by \"{}\")", self.search.trim())).weak());
+            }
+        });
+        ui.separator();
+        if cards.is_empty() {
+            ui.add_space(20.0);
+            ui.vertical_centered(|ui| {
+                ui.label(egui::RichText::new("Nothing here.").weak());
+                ui.label(
+                    egui::RichText::new(
+                        "Drop a yt-dlp download into channels/<name>/, or use the Downloads panel.",
+                    )
+                    .small()
+                    .weak(),
+                );
+            });
+            return;
+        }
+        egui::ScrollArea::vertical().auto_shrink([false, false]).show(ui, |ui| {
+            let thumb_size = egui::vec2(176.0, 99.0);
+            for card in &cards {
+                let selected = self.selected_video == Some((card.channel_idx, card.video_idx));
+                let mut clicked_card = false;
+                let mut play_card = false;
+                ui.horizontal(|ui| {
+                    let (rect, resp) = ui.allocate_exact_size(thumb_size, egui::Sense::click());
+                    let texture = card
+                        .thumb_path
+                        .as_ref()
+                        .and_then(|p| self.texture(ctx, p));
+                    match &texture {
+                        Some(handle) => {
+                            egui::Image::new(handle)
+                                .maintain_aspect_ratio(true)
+                                .paint_at(ui, rect);
+                        }
+                        None => {
+                            ui.painter().rect_filled(rect, 4.0, egui::Color32::from_gray(38));
+                            ui.painter().text(
+                                rect.center(),
+                                egui::Align2::CENTER_CENTER,
+                                "▶",
+                                egui::FontId::proportional(26.0),
+                                egui::Color32::from_gray(110),
+                            );
+                        }
+                    }
+                    if selected {
+                        ui.painter().rect_stroke(
+                            rect,
+                            4.0,
+                            egui::Stroke::new(2.0, egui::Color32::from_rgb(120, 170, 230)),
+                        );
+                    }
+                    if resp.clicked() {
+                        clicked_card = true;
+                    }
+                    if resp.double_clicked() {
+                        play_card = true;
+                    }
+
+                    ui.vertical(|ui| {
+                        if ui
+                            .selectable_label(selected, egui::RichText::new(&card.title).strong())
+                            .clicked()
+                        {
+                            clicked_card = true;
+                        }
+                        ui.horizontal(|ui| {
+                            if show_channel {
+                                ui.label(egui::RichText::new(&card.channel_name).small().weak());
+                                ui.label(egui::RichText::new("·").weak());
+                            }
+                            ui.label(egui::RichText::new(&card.id).small().monospace().weak());
+                            if card.has_live_chat {
+                                ui.label(egui::RichText::new("· 💬").small().weak());
+                            }
+                            if card.video_path.is_none() {
+                                ui.label(
+                                    egui::RichText::new("· no video file")
+                                        .small()
+                                        .color(egui::Color32::from_rgb(200, 140, 90)),
+                                );
+                            }
+                        });
+                        ui.horizontal(|ui| {
+                            if card.video_path.is_some() && ui.small_button("▶ Play").clicked() {
+                                play_card = true;
+                            }
+                            if ui.small_button("Details").clicked() {
+                                clicked_card = true;
+                            }
+                        });
+                    });
+                });
+                if play_card {
+                    if let Some(p) = card.video_path.clone() {
+                        self.play(&p);
+                    }
+                    self.selected_video = Some((card.channel_idx, card.video_idx));
+                } else if clicked_card {
+                    self.selected_video = Some((card.channel_idx, card.video_idx));
+                }
+                ui.separator();
+            }
+        });
+    }
+}
+
+impl eframe::App for App {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        self.downloader.poll();
+        if self.downloader.any_running() {
+            ctx.request_repaint_after(std::time::Duration::from_millis(250));
+        }
+        // Decode at most a few thumbnails per frame so scrolling stays smooth.
+        self.decode_budget = 6;
+
+        self.top_bar(ctx);
+        self.channel_panel(ctx);
+        if self.show_downloads {
+            self.downloads_panel(ctx);
+        }
+        self.detail_panel(ctx);
+        egui::CentralPanel::default().show(ctx, |ui| {
+            self.video_list(ctx, ui);
+        });
+    }
+}
+
+fn decode_thumbnail(ctx: &egui::Context, path: &Path) -> Option<egui::TextureHandle> {
+    let image = image::open(path).ok()?;
+    let image = image.thumbnail(384, 216);
+    let rgba = image.to_rgba8();
+    let (w, h) = (rgba.width() as usize, rgba.height() as usize);
+    let color_image = egui::ColorImage::from_rgba_unmultiplied([w, h], rgba.as_raw());
+    Some(ctx.load_texture(
+        path.to_string_lossy(),
+        color_image,
+        egui::TextureOptions::LINEAR,
+    ))
+}
+
+fn file_label(path: &Path) -> String {
+    path.file_name()
+        .map(|n| n.to_string_lossy().into_owned())
+        .unwrap_or_else(|| path.to_string_lossy().into_owned())
+}

src/downloader.rs

@@ -0,0 +1,146 @@
+//! Running `yt-dlp` in the background and surfacing its progress to the UI.
+
+use std::io::{BufRead, BufReader};
+use std::path::PathBuf;
+use std::process::{Command, Stdio};
+use std::sync::mpsc::{channel, Receiver};
+use std::thread;
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub enum JobState {
+    Running,
+    Done,
+    Failed,
+}
+
+enum Msg {
+    Line(String),
+    Progress(f32),
+    Finished(bool),
+}
+
+pub struct Job {
+    pub url: String,
+    pub dir_name: String,
+    pub state: JobState,
+    pub progress: f32,
+    pub log: Vec<String>,
+    rx: Receiver<Msg>,
+}
+
+impl Job {
+    fn drain(&mut self) {
+        while let Ok(msg) = self.rx.try_recv() {
+            match msg {
+                Msg::Line(line) => {
+                    self.log.push(line);
+                    if self.log.len() > 800 {
+                        let cut = self.log.len() - 800;
+                        self.log.drain(0..cut);
+                    }
+                }
+                Msg::Progress(p) => self.progress = p,
+                Msg::Finished(ok) => {
+                    self.state = if ok { JobState::Done } else { JobState::Failed };
+                }
+            }
+        }
+    }
+}
+
+pub struct Downloader {
+    pub jobs: Vec<Job>,
+    channels_root: PathBuf,
+}
+
+impl Downloader {
+    pub fn new(channels_root: PathBuf) -> Self {
+        Self {
+            jobs: Vec::new(),
+            channels_root,
+        }
+    }
+
+    pub fn start(&mut self, url: String, dir_name: String) {
+        let (tx, rx) = channel();
+        let target_dir = self.channels_root.join(&dir_name);
+        let _ = std::fs::create_dir_all(&target_dir);
+
+        let url_for_thread = url.clone();
+        thread::spawn(move || {
+            let out_template = format!("{}/%(title)s [%(id)s].%(ext)s", target_dir.display());
+            let spawn_result = Command::new("yt-dlp")
+                .arg("--newline")
+                .arg("--no-color")
+                .arg("--no-progress-bar")
+                .arg("--write-description")
+                .arg("--write-thumbnail")
+                .arg("--ignore-errors")
+                .arg("-o")
+                .arg(&out_template)
+                .arg(&url_for_thread)
+                .stdin(Stdio::null())
+                .stdout(Stdio::piped())
+                .stderr(Stdio::piped())
+                .spawn();
+
+            let mut child = match spawn_result {
+                Ok(child) => child,
+                Err(err) => {
+                    let _ = tx.send(Msg::Line(format!("could not launch yt-dlp: {err}")));
+                    let _ = tx.send(Msg::Finished(false));
+                    return;
+                }
+            };
+
+            // Forward stderr on its own thread so a full pipe can't deadlock stdout.
+            if let Some(stderr) = child.stderr.take() {
+                let tx = tx.clone();
+                thread::spawn(move || {
+                    for line in BufReader::new(stderr).lines().map_while(Result::ok) {
+                        let _ = tx.send(Msg::Line(format!("[stderr] {line}")));
+                    }
+                });
+            }
+
+            if let Some(stdout) = child.stdout.take() {
+                for line in BufReader::new(stdout).lines().map_while(Result::ok) {
+                    if let Some(p) = parse_progress(&line) {
+                        let _ = tx.send(Msg::Progress(p));
+                    }
+                    let _ = tx.send(Msg::Line(line));
+                }
+            }
+
+            let ok = child.wait().map(|s| s.success()).unwrap_or(false);
+            let _ = tx.send(Msg::Finished(ok));
+        });
+
+        self.jobs.push(Job {
+            url,
+            dir_name,
+            state: JobState::Running,
+            progress: 0.0,
+            log: Vec::new(),
+            rx,
+        });
+    }
+
+    pub fn poll(&mut self) {
+        for job in &mut self.jobs {
+            job.drain();
+        }
+    }
+
+    pub fn any_running(&self) -> bool {
+        self.jobs.iter().any(|j| j.state == JobState::Running)
+    }
+}
+
+/// Parses the percentage out of a yt-dlp `[download]  12.3% of ...` line.
+fn parse_progress(line: &str) -> Option<f32> {
+    let rest = line.trim_start().strip_prefix("[download]")?.trim_start();
+    let pct_end = rest.find('%')?;
+    let value: f32 = rest[..pct_end].trim().parse().ok()?;
+    Some((value / 100.0).clamp(0.0, 1.0))
+}

src/library.rs

@@ -0,0 +1,145 @@
+//! Scanning the `channels/` directory tree into channels and videos.
+//!
+//! yt-dlp's default output template produces files named `Title [VIDEOID].ext`,
+//! so every file that belongs to one video shares the stem `Title [VIDEOID]`.
+//! We group files by that stem.
+
+use std::collections::BTreeMap;
+use std::path::{Path, PathBuf};
+
+const VIDEO_EXTS: &[&str] = &["mkv", "mp4", "webm", "m4v", "mov", "avi"];
+const THUMB_EXTS: &[&str] = &["webp", "jpg", "jpeg", "png"];
+
+#[derive(Clone, Debug)]
+pub struct Video {
+    pub id: String,
+    pub title: String,
+    /// The shared filename stem, e.g. `Title [VIDEOID]`.
+    #[allow(dead_code)]
+    pub stem: String,
+    pub video_path: Option<PathBuf>,
+    pub thumb_path: Option<PathBuf>,
+    pub description_path: Option<PathBuf>,
+    pub has_live_chat: bool,
+}
+
+#[derive(Clone, Debug)]
+pub struct Channel {
+    pub name: String,
+    pub path: PathBuf,
+    pub videos: Vec<Video>,
+}
+
+pub fn scan_channels(root: &Path) -> Vec<Channel> {
+    let mut channels = Vec::new();
+    let Ok(entries) = std::fs::read_dir(root) else {
+        return channels;
+    };
+    for entry in entries.flatten() {
+        let path = entry.path();
+        if !path.is_dir() {
+            continue;
+        }
+        let name = entry.file_name().to_string_lossy().into_owned();
+        let videos = scan_channel_dir(&path);
+        channels.push(Channel { name, path, videos });
+    }
+    channels.sort_by_key(|c| c.name.to_lowercase());
+    channels
+}
+
+enum FileKind {
+    Video,
+    Thumb,
+    Description,
+    LiveChat,
+    Other,
+}
+
+/// Returns `(stem, kind)` for a file name, or `None` if it isn't a per-video file
+/// (e.g. yt-dlp's `archive.txt`).
+fn classify(file_name: &str) -> Option<(&str, FileKind)> {
+    // Compound suffixes first.
+    if let Some(stem) = file_name.strip_suffix(".live_chat.json") {
+        return Some((stem, FileKind::LiveChat));
+    }
+    if let Some(stem) = file_name.strip_suffix(".info.json") {
+        return Some((stem, FileKind::Other));
+    }
+    let dot = file_name.rfind('.')?;
+    let stem = &file_name[..dot];
+    if stem.is_empty() {
+        return None;
+    }
+    let ext = file_name[dot + 1..].to_lowercase();
+    let kind = if VIDEO_EXTS.contains(&ext.as_str()) {
+        FileKind::Video
+    } else if THUMB_EXTS.contains(&ext.as_str()) {
+        FileKind::Thumb
+    } else if ext == "description" {
+        FileKind::Description
+    } else {
+        FileKind::Other
+    };
+    Some((stem, kind))
+}
+
+/// Splits `Title [VIDEOID]` into `(title, id)`. Requires a trailing `[...]` group.
+fn parse_stem(stem: &str) -> Option<(String, String)> {
+    let close = stem.rfind(']')?;
+    let open = stem[..close].rfind('[')?;
+    let id = stem[open + 1..close].trim();
+    if id.is_empty() {
+        return None;
+    }
+    let title = stem[..open].trim().trim_end_matches('-').trim();
+    let title = if title.is_empty() { stem } else { title };
+    Some((title.to_string(), id.to_string()))
+}
+
+fn scan_channel_dir(dir: &Path) -> Vec<Video> {
+    let mut by_stem: BTreeMap<String, Video> = BTreeMap::new();
+    let Ok(entries) = std::fs::read_dir(dir) else {
+        return Vec::new();
+    };
+    for entry in entries.flatten() {
+        let path = entry.path();
+        if !path.is_file() {
+            continue;
+        }
+        let file_name = entry.file_name().to_string_lossy().into_owned();
+        let Some((stem, kind)) = classify(&file_name) else {
+            continue;
+        };
+        let Some((title, id)) = parse_stem(stem) else {
+            continue;
+        };
+        let video = by_stem.entry(stem.to_string()).or_insert_with(|| Video {
+            id,
+            title,
+            stem: stem.to_string(),
+            video_path: None,
+            thumb_path: None,
+            description_path: None,
+            has_live_chat: false,
+        });
+        match kind {
+            FileKind::Video => {
+                if video.video_path.is_none() {
+                    video.video_path = Some(path);
+                }
+            }
+            FileKind::Thumb => {
+                if video.thumb_path.is_none() {
+                    video.thumb_path = Some(path);
+                }
+            }
+            FileKind::Description => video.description_path = Some(path),
+            FileKind::LiveChat => video.has_live_chat = true,
+            FileKind::Other => {}
+        }
+    }
+    let mut videos: Vec<Video> = by_stem.into_values().collect();
+    videos.sort_by_key(|v| v.title.to_lowercase());
+    videos
+}

src/main.rs

@@ -0,0 +1,20 @@
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+mod app;
+mod downloader;
+mod library;
+
+fn main() -> eframe::Result<()> {
+    let native_options = eframe::NativeOptions {
+        viewport: eframe::egui::ViewportBuilder::default()
+            .with_inner_size([1280.0, 820.0])
+            .with_min_inner_size([800.0, 500.0])
+            .with_title("YouTube Backup"),
+        ..Default::default()
+    };
+    eframe::run_native(
+        "youtube-backup",
+        native_options,
+        Box::new(|cc| Ok(Box::new(app::App::new(cc)))),
+    )
+}