//! Workspace, file-list and git operations: opening a folder, creating,
//! renaming and deleting manuscript files, persisting order and titles, and
//! exporting the assembled manuscript to ODT.

use super::*;

impl App {
    pub(super) fn workspace(&self) -> &Path {
        &self.config.workspace
    }

    /// The project folder: the root holding the characters, the outline and the
    /// reference material alongside the draft folder.
    ///
    /// In project mode the workspace already *is* that root. Otherwise the
    /// workspace is a folder of chapters one level down, and the enclosing git
    /// work tree is the project around it — including one still awaiting the
    /// user's confirmation, since which folder to show in a file manager is a
    /// smaller question than which repository to commit to.
    ///
    /// Falls back to the workspace when there is no repository, rather than
    /// guessing at a parent: an unversioned folder of chapters has no project
    /// around it that we can point to with any confidence. Reads only cached
    /// state, because the toolbar asks for this every frame.
    pub(super) fn project_root(&self) -> &Path {
        project_root_of(
            &self.config.workspace,
            self.manuscript_dir.is_some(),
            self.repo_root.as_deref(),
            self.pending_repo.as_deref(),
        )
    }

    /// Show the project folder in the desktop's file manager.
    pub(super) fn open_project_folder(&mut self) {
        let path = self.project_root().to_path_buf();
        if !path.is_dir() {
            self.status = format!("No such folder: {}", path.display());
            return;
        }
        // xdg-open picks whichever file manager the session provides, the same
        // desktop-portal assumption the native file dialogs already make.
        let spawned = std::process::Command::new("xdg-open")
            .arg(&path)
            .stdout(std::process::Stdio::null())
            .stderr(std::process::Stdio::null())
            .spawn();
        match spawned {
            Ok(mut child) => {
                // xdg-open hands off to the file manager and exits immediately.
                // Reap it off-thread so each click does not leave a zombie behind.
                std::thread::spawn(move || {
                    let _ = child.wait();
                });
                self.status = format!("Opened {}", path.display());
            }
            Err(e) => self.status = format!("Could not open {}: {e}", path.display()),
        }
    }

    /// (Re)load the file list for the current workspace, creating the directory
    /// if needed, and refresh git status.
    pub(super) fn open_workspace(&mut self) {
        let ws = self.config.workspace.clone();
        if let Err(e) = std::fs::create_dir_all(&ws) {
            self.status = format!("Cannot create workspace: {e}");
            return;
        }
        // The project root has moved, so the export follows it.
        self.retarget_export();
        // Which folder is the manuscript has to be settled before the file
        // list is read, since it decides what counts as a chapter.
        self.manuscript_dir = self.detect_manuscript_dir(&ws);
        self.files = order::resolve_order(&ws, &self.config.hidden_folders);
        self.titles = order::read_titles(&ws);
        self.wordlist = crate::spell::read_wordlist(&ws);
        // Drop overrides for files that no longer exist.
        self.titles.retain(|name, _| self.files.contains(name));
        self.detect_repo(&ws);
        self.selected = None;
        self.buffer.clear();
        self.header_stash = None;
        self.dirty = false;
        self.pending_delete = false;
        self.clear_lt();
        self.dismissed.clear();
        self.session_start_counts = self.snapshot_counts();
        self.file_meta = self.snapshot_file_meta();
        self.rebuild_field_names();
        self.load_characters();
        self.autocomplete = None;
        self.collapsed.clear();
        if let Some(idx) = first_listed(&self.files, self.manuscript_dir.as_deref()) {
            self.select(idx);
        }
        self.persist_order();
        self.status = match &self.manuscript_dir {
            Some(dir) => {
                let chapters = self.manuscript_files().len();
                format!(
                    "{chapters} chapter(s) in {dir}, {} reference file(s) — {}",
                    self.files.len() - chapters,
                    ws.display()
                )
            }
            None => format!("{} file(s) in {}", self.files.len(), ws.display()),
        };
    }

    /// Point the export at the opened workspace, which is the project root.
    ///
    /// A file name the user picked deliberately is carried across; one that
    /// merely echoed the previous project's folder is re-derived, so exports
    /// land beside the book being worked on instead of piling up in the
    /// project left behind.
    pub(super) fn retarget_export(&mut self) {
        let path = export_path_for(&self.config.workspace, &self.config.export_path);
        if path != self.config.export_path {
            self.config.export_path = path;
            self.config.save();
        }
        self.export_input = self.config.export_path.display().to_string();
    }

    /// Work out the git situation for a freshly opened workspace.
    ///
    /// If the folder is itself a repository root it is adopted silently. If it
    /// is not, but an enclosing parent directory is a git work tree, we stash
    /// that parent in `pending_repo` and ask the user to confirm before using
    /// it (see [`repo_prompt`](Self::repo_prompt)). Otherwise the workspace is
    /// treated as having no repository.
    pub(super) fn detect_repo(&mut self, ws: &Path) {
        self.pending_repo = None;
        // A `.git` entry directly in the folder (dir, or a file for linked
        // worktrees/submodules) means this folder is the repo root.
        if ws.join(".git").exists() {
            self.is_repo = true;
            self.repo_root = Some(ws.to_path_buf());
            return;
        }
        match gitsync::repo_root(ws) {
            // A parent directory is a repository — ask before adopting it.
            Some(root) if root != ws => {
                self.is_repo = false;
                self.repo_root = None;
                self.pending_repo = Some(root);
            }
            // `--show-toplevel` reported this very folder (shouldn't happen
            // without a `.git` here, but treat it as an ordinary repo root).
            Some(root) => {
                self.is_repo = true;
                self.repo_root = Some(root);
            }
            None => {
                self.is_repo = false;
                self.repo_root = None;
            }
        }
    }

    /// Adopt the parent repository awaiting confirmation, using it for all git
    /// operations on the current workspace.
    pub(super) fn adopt_pending_repo(&mut self) {
        if let Some(root) = self.pending_repo.take() {
            self.status = format!("Using git repository at {}", root.display());
            self.is_repo = true;
            self.repo_root = Some(root);
        }
    }

    /// Decline the parent repository; the workspace stays without version
    /// control (the user can still `Init git` to create a nested repo).
    pub(super) fn decline_pending_repo(&mut self) {
        self.pending_repo = None;
        self.is_repo = false;
        self.repo_root = None;
        self.status = "Not using the enclosing git repository".to_string();
    }

    /// Work out whether the opened folder is a **project root** — a folder
    /// holding the manuscript alongside characters, outline and the rest — and
    /// if so, which of its subfolders is the manuscript.
    ///
    /// The test is simply whether it has a child folder named like the
    /// configured manuscript folder (`06-First Draft`), matched leniently by
    /// [`order::dir_matches`]. `None` means the workspace is itself the
    /// manuscript, which is how the app behaved before project mode and remains
    /// the right answer for a plain folder of chapters.
    pub(super) fn detect_manuscript_dir(&self, ws: &Path) -> Option<String> {
        order::child_dir_matching(ws, self.config.project_open_subdir.trim())
    }

    /// Whether `path` (workspace-relative) is part of the manuscript proper:
    /// ordered, numbered and exported. Everything else in a project — character
    /// sheets, outline, scratch pad — is reference material that the app will
    /// happily open and edit but leaves out of the book.
    pub(super) fn is_manuscript(&self, path: &str) -> bool {
        match &self.manuscript_dir {
            Some(dir) => is_within(path, dir),
            None => true,
        }
    }

    /// The manuscript's files, in order, paired with their chapter index.
    pub(super) fn manuscript_files(&self) -> Vec<(usize, &String)> {
        self.files
            .iter()
            .filter(|path| self.is_manuscript(path))
            .enumerate()
            .collect()
    }

    /// Read every file and return its current on-disk word count.
    pub(super) fn snapshot_counts(&self) -> HashMap<String, usize> {
        self.files
            .iter()
            .map(|name| {
                let text = std::fs::read_to_string(self.path_for(name)).unwrap_or_default();
                (name.clone(), count_words(&text))
            })
            .collect()
    }

    /// Read every file and return its cached header info (slug/POV/goal/status
    /// and prose length). Every file is cached, not only the ones with a tooltip
    /// to show, because the status column and the project word total need a
    /// figure for each.
    pub(super) fn snapshot_file_meta(&self) -> HashMap<String, FileMeta> {
        self.files
            .iter()
            .map(|name| {
                let text = std::fs::read_to_string(self.path_for(name)).unwrap_or_default();
                (
                    name.clone(),
                    FileMeta::from_markdown(&text, &self.config.draft_marker),
                )
            })
            .collect()
    }

    /// Prose words across the whole manuscript, counting the open file from the
    /// buffer so the total moves as you type.
    pub(super) fn manuscript_words(&self) -> usize {
        let open = self.selected.and_then(|i| self.files.get(i));
        self.manuscript_files()
            .into_iter()
            .map(|(_, name)| {
                if Some(name) == open {
                    let h =
                        crate::preprocess::parse(&self.document(), &self.config.draft_marker);
                    count_words(&h.body)
                } else {
                    self.file_meta.get(name).map_or(0, |m| m.prose_words)
                }
            })
            .sum()
    }

    /// Every distinct `Status:` value in the manuscript, for the filter menu.
    pub(super) fn known_statuses(&self) -> Vec<String> {
        let mut seen: Vec<String> = Vec::new();
        for name in self.files.iter() {
            let Some(status) = self.file_meta.get(name).and_then(|m| m.status.clone()) else {
                continue;
            };
            if !seen.iter().any(|s| s.eq_ignore_ascii_case(&status)) {
                seen.push(status);
            }
        }
        seen.sort_by_key(|s| s.to_lowercase());
        seen
    }

    pub(super) fn persist_order(&self) {
        let _ = order::write_order(self.workspace(), &self.files);
    }

    pub(super) fn persist_titles(&self) {
        let _ = order::write_titles(self.workspace(), &self.titles);
    }

    /// Store the title override for the selected file from `title_input`.
    /// An empty value removes the override (falls back to the auto title).
    pub(super) fn set_title_for_current(&mut self) {
        if let Some(idx) = self.selected {
            if let Some(name) = self.files.get(idx).cloned() {
                let trimmed = self.title_input.trim();
                if trimmed.is_empty() {
                    self.titles.remove(&name);
                } else {
                    self.titles.insert(name, trimmed.to_string());
                }
                self.persist_titles();
            }
        }
    }

    pub(super) fn path_for(&self, name: &str) -> PathBuf {
        self.workspace().join(name)
    }

    // ---- Collapsing the editorial header ------------------------------------

    /// The whole document: the editor's text with the collapsed header, if any,
    /// put back in front of it.
    ///
    /// While the header is collapsed it is not in `buffer` at all, which is what
    /// keeps every byte offset the editor works in — search matches, spelling
    /// underlines, the caret — pointing at what is actually on screen. Anything
    /// that wants the *file* rather than the view asks for this instead.
    pub(super) fn document(&self) -> std::borrow::Cow<'_, str> {
        match &self.header_stash {
            Some(header) => std::borrow::Cow::Owned(format!("{header}{}", self.buffer)),
            None => std::borrow::Cow::Borrowed(&self.buffer),
        }
    }

    /// Lift the header out of the buffer, leaving the prose. Does nothing for a
    /// document with no draft marker — there is nothing to collapse.
    pub(super) fn collapse_header(&mut self) {
        if self.header_stash.is_some() {
            return;
        }
        let Some((header, body)) =
            crate::preprocess::split_at_marker(&self.buffer, &self.config.draft_marker)
        else {
            return;
        };
        let (header, body) = (header.to_string(), body.to_string());
        self.header_stash = Some(header);
        self.buffer = body;
        self.after_view_change();
    }

    /// Put the header back into the buffer.
    pub(super) fn expand_header(&mut self) {
        let Some(header) = self.header_stash.take() else {
            return;
        };
        self.buffer.insert_str(0, &header);
        self.after_view_change();
    }

    /// Re-collapse or expand to match the setting, after the buffer is replaced.
    pub(super) fn apply_header_collapse(&mut self) {
        if self.config.collapse_header {
            self.collapse_header();
        } else {
            self.expand_header();
        }
    }

    /// Everything keyed to the buffer's contents has to be recomputed when the
    /// header moves in or out of it — but the file itself has not changed, so
    /// this must not mark the document dirty.
    fn after_view_change(&mut self) {
        self.find_matches.clear();
        self.find_active = 0;
        self.find_needs_refresh = true;
        self.spell_matches.clear();
        self.spell_checked_text.clear();
        self.spell_dirty = true;
        self.spell_last_edit = None;
        self.spell_menu = None;
        self.clear_lt();
        self.autocomplete = None;
    }

    /// How many header fields are hidden right now, for the toggle's label.
    pub(super) fn hidden_field_count(&self) -> usize {
        match &self.header_stash {
            Some(header) => crate::preprocess::fields(header, "").len(),
            None => 0,
        }
    }

    /// Save the in-memory buffer to disk if it has unsaved changes.
    pub(super) fn save_current(&mut self) {
        if let Some(idx) = self.selected {
            if self.dirty {
                if let Some(name) = self.files.get(idx).cloned() {
                    let path = self.path_for(&name);
                    match std::fs::write(&path, self.document().as_bytes()) {
                        Ok(_) => {
                            self.dirty = false;
                            self.status = format!("Saved {name}");
                            // Keep the file-list cache (slug/POV/goal/prose) in step.
                            let meta = FileMeta::from_markdown(
                                &self.document(),
                                &self.config.draft_marker,
                            );
                            self.file_meta.insert(name, meta);
                            self.merge_field_names_from_buffer();
                        }
                        Err(e) => self.status = format!("Save failed: {e}"),
                    }
                }
            }
        }
    }

    pub(super) fn select(&mut self, idx: usize) {
        if self.selected == Some(idx) {
            return;
        }
        self.save_current();
        self.clear_lt();
        // Matches from the previous file's buffer are meaningless now.
        self.find_matches.clear();
        self.find_active = 0;
        self.find_needs_refresh = true;
        // Re-run the live spell check on the newly loaded buffer immediately.
        self.spell_matches.clear();
        self.spell_checked_text.clear();
        self.spell_dirty = true;
        self.spell_last_edit = None;
        self.spell_menu = None;
        // Dismissals are about this file's sentences, not the next one's.
        self.dismissed.clear();
        let Some(name) = self.files.get(idx).cloned() else {
            return;
        };
        let path = self.path_for(&name);
        self.header_stash = None;
        self.buffer = std::fs::read_to_string(&path).unwrap_or_default();
        self.apply_header_collapse();
        self.selected = Some(idx);
        self.dirty = false;
        self.pending_delete = false;
        // The rename box holds the whole workspace-relative path, so it doubles
        // as the way to move a file between folders by typing.
        self.rename_input = strip_md(&name).to_string();
        self.title_input = self.titles.get(&name).cloned().unwrap_or_default();
        self.reveal(&name);
    }

    /// Expand any collapsed folders that would hide `path`, so a file that was
    /// just selected or created is actually on screen.
    pub(super) fn reveal(&mut self, path: &str) {
        self.collapsed.retain(|dir| !is_within(path, dir));
    }

    /// Move one manuscript file on disk and carry its per-file state — title
    /// override, session word baseline, cached header info — across to the new
    /// path. The caller is responsible for updating `files`; on error nothing
    /// has changed.
    fn relocate(&mut self, old: &str, new: &str) -> std::io::Result<()> {
        move_manuscript_file(self.workspace(), old, new)?;
        if let Some(title) = self.titles.remove(old) {
            self.titles.insert(new.to_string(), title);
            self.persist_titles();
        }
        if let Some(words) = self.session_start_counts.remove(old) {
            self.session_start_counts.insert(new.to_string(), words);
        }
        if let Some(meta) = self.file_meta.remove(old) {
            self.file_meta.insert(new.to_string(), meta);
        }
        Ok(())
    }

    pub(super) fn create_file(&mut self) {
        // The typed name may carry folders (`part-1/ch-01`), which is the only
        // way new folders come into being — one appears with its first file.
        let Some(name) = sanitize_rel_path(&self.new_name) else {
            self.status = "Enter a name for the new file".to_string();
            return;
        };
        let stem = strip_md(base_name(&name)).to_string();
        let seed = format!("# {stem}\n\n");
        self.insert_new_file(name, seed);
    }

    /// Create a file seeded from the configured template, naming it
    /// `untitled-N.md` so the button works without typing a name first. It lands
    /// beside the file being edited, so working inside a part folder doesn't
    /// scatter untitled files back at the workspace root.
    pub(super) fn create_file_from_template(&mut self) {
        let dir = self
            .selected
            .and_then(|i| self.files.get(i))
            .map(|path| parent_dir(path).to_string())
            .unwrap_or_default();
        let existing: std::collections::HashSet<String> =
            self.files.iter().map(|n| n.to_lowercase()).collect();
        let leaf = next_untitled_name(|candidate| {
            let full = join_rel(&dir, candidate);
            existing.contains(&full.to_lowercase()) || self.path_for(&full).exists()
        });
        let stem = strip_md(&leaf).to_string();
        let seed = render_template(
            &self.config.effective_new_file_template(),
            &stem,
            self.config.draft_marker.trim(),
            &today_utc(),
        );
        self.insert_new_file(join_rel(&dir, &leaf), seed);
        // The template's header fields should be offerable straight away.
        self.rebuild_field_names();
    }

    /// Write `contents` to a new file, add it to the manuscript order and select
    /// it. Shared by the plain and template-backed create paths.
    fn insert_new_file(&mut self, name: String, contents: String) {
        let path = self.path_for(&name);
        if path.exists() {
            self.status = format!("{name} already exists");
            return;
        }
        if let Some(parent) = path.parent() {
            if let Err(e) = std::fs::create_dir_all(parent) {
                self.status = format!("Create failed: {e}");
                return;
            }
        }
        match std::fs::write(&path, contents) {
            Ok(_) => {
                self.files.push(name.clone());
                // Folder-tree order decides where the newcomer actually lands,
                // so normalise before working out which index to select.
                self.files = order::tree_order(&self.files);
                self.persist_order();
                let idx = self.files.iter().position(|f| *f == name).unwrap_or(0);
                self.selected = None; // force reload of buffer
                self.select(idx);
                self.new_name.clear();
                self.status = format!("Created {name}");
            }
            Err(e) => self.status = format!("Create failed: {e}"),
        }
    }

    pub(super) fn delete_selected(&mut self) {
        if let Some(idx) = self.selected {
            if let Some(name) = self.files.get(idx).cloned() {
                let path = self.path_for(&name);
                match std::fs::remove_file(&path) {
                    Ok(_) => {
                        self.files.remove(idx);
                        self.titles.remove(&name);
                        self.session_start_counts.remove(&name);
                        self.file_meta.remove(&name);
                        self.persist_titles();
                        self.persist_order();
                        // The folder may have held nothing else.
                        prune_empty_dirs(self.workspace(), parent_dir(&name));
                        self.selected = None;
                        self.buffer.clear();
        self.header_stash = None;
                        self.dirty = false;
                        if let Some(next) =
                            nearest_listed(&self.files, self.manuscript_dir.as_deref(), idx)
                        {
                            self.select(next);
                        }
                        self.status = format!("Deleted {name}");
                    }
                    Err(e) => self.status = format!("Delete failed: {e}"),
                }
            }
        }
        self.pending_delete = false;
    }

    /// Move the selected file into the project's archive folder: off the
    /// manuscript, out of the panel, but still on disk.
    ///
    /// Deleting is destructive and a superseded scene is often worth keeping;
    /// the archive folder is hidden from the scan, so archiving a file makes it
    /// disappear from the tree without losing it.
    pub(super) fn archive_selected(&mut self) {
        let Some(idx) = self.selected else { return };
        let Some(name) = self.files.get(idx).cloned() else {
            return;
        };
        let archive = self.archive_dir();
        // Keep the file's shape inside the archive, so a scene from
        // `Act 1/` lands in `10-Archive/Act 1/` rather than losing its place.
        let dest = join_rel(&archive, &name);
        if self.path_for(&dest).exists() {
            self.status = format!("{dest} already exists");
            return;
        }
        self.save_current();
        if let Err(e) = self.relocate(&name, &dest) {
            self.status = format!("Archive failed: {e}");
            return;
        }
        self.files.remove(idx);
        self.persist_order();
        self.selected = None;
        self.buffer.clear();
        self.header_stash = None;
        self.dirty = false;
        if let Some(next) = nearest_listed(&self.files, self.manuscript_dir.as_deref(), idx) {
            self.select(next);
        }
        self.status = format!("Archived {name} to {archive}");
    }

    /// The archive folder's name within the workspace: whatever the project
    /// already calls it, otherwise the configured default.
    pub(super) fn archive_dir(&self) -> String {
        let configured = self.config.archive_folder.trim();
        let role = if configured.is_empty() {
            "Archive"
        } else {
            configured
        };
        order::child_dir_matching(self.workspace(), role).unwrap_or_else(|| role.to_string())
    }

    pub(super) fn rename_selected(&mut self) {
        let Some(idx) = self.selected else { return };
        // A path in the box (`part-2/ch-07`) both renames and moves the file.
        let Some(new_name) = sanitize_rel_path(&self.rename_input) else {
            self.status = "Enter a new name".to_string();
            return;
        };
        let Some(old_name) = self.files.get(idx).cloned() else {
            return;
        };
        if new_name == old_name {
            return;
        }
        if self.path_for(&new_name).exists() {
            self.status = format!("{new_name} already exists");
            return;
        }
        // Persist any pending edits under the old name first.
        self.save_current();
        match self.relocate(&old_name, &new_name) {
            Ok(_) => {
                self.files[idx] = new_name.clone();
                self.files = order::tree_order(&self.files);
                self.selected = self.files.iter().position(|f| *f == new_name);
                self.persist_order();
                self.reveal(&new_name);
                self.status = format!("Renamed to {new_name}");
            }
            Err(e) => self.status = format!("Rename failed: {e}"),
        }
    }

    pub(super) fn git_init(&mut self) {
        // Initialising creates a repository in the workspace itself, which
        // supersedes any enclosing repo we were about to ask about.
        self.pending_repo = None;
        let ws = self.workspace().to_path_buf();
        let outcome = gitsync::init(&ws);
        self.git_log = outcome.log;
        self.show_log = true;
        self.is_repo = gitsync::is_repo(&ws);
        self.repo_root = self.is_repo.then_some(ws);
        self.status = if self.is_repo {
            "Initialised git repository".to_string()
        } else {
            "git init failed (see log)".to_string()
        };
    }

    pub(super) fn git_sync(&mut self) {
        self.save_current();
        self.persist_order();
        self.persist_titles();
        let msg = format!(
            "Sync manuscript {}",
            chrono_like_timestamp()
        );
        let outcome = gitsync::sync(self.workspace(), &msg);
        self.git_log = outcome.log;
        self.show_log = true;
        self.status = if outcome.ok {
            "Sync complete".to_string()
        } else {
            "Sync finished with errors (see log)".to_string()
        };
    }

    /// Digits to zero-pad a defaulted chapter number to: the width of the largest
    /// chapter number when padding is enabled, otherwise 1 (no padding).
    pub(super) fn index_pad_width(&self) -> usize {
        if self.config.zero_pad_index {
            self.manuscript_files().len().to_string().len().max(1)
        } else {
            1
        }
    }

    /// The title a chapter at `idx` would get without a manual override: its
    /// `# Title:` header, or its 1-based position (e.g. "3."). Shown as the hint
    /// in the chapter-title field.
    pub(super) fn auto_title(&self, idx: usize, markdown: &str) -> String {
        let header = crate::preprocess::parse(markdown, &self.config.draft_marker);
        resolve_chapter_title(None, header.title.as_deref(), idx, self.index_pad_width())
    }

    /// The current file's word-count target (from its `Word Count Target:`
    /// header) paired with its current prose word count, if a target is set.
    /// Prose = the body below the draft marker, so header metadata isn't counted.
    pub(super) fn current_goal(&self) -> Option<(crate::preprocess::WordGoal, usize)> {
        self.selected?;
        let header = crate::preprocess::parse(&self.document(), &self.config.draft_marker);
        let goal = header.goal?;
        Some((goal, count_words(&header.body)))
    }

    /// Document properties for an export: the configured title, author and
    /// contact details, with the title falling back to the project folder's own
    /// name.
    pub(super) fn doc_meta(&self, chapters: &[Chapter]) -> odt::DocMeta {
        let title = match self.config.manuscript_title.trim() {
            "" => self
                .workspace()
                .file_name()
                .and_then(|n| n.to_str())
                .unwrap_or("Manuscript")
                .to_string(),
            set => set.to_string(),
        };
        odt::DocMeta {
            title,
            author: self.config.manuscript_author.trim().to_string(),
            contact: self.config.manuscript_contact.clone(),
            title_page: self.config.manuscript_title_page,
            standard_format: self.config.manuscript_standard_format,
            subject: String::new(),
            keywords: String::new(),
            word_count: chapters.iter().map(|c| count_words(&c.markdown)).sum(),
            chapter_count: chapters.len(),
        }
    }

    /// Export the manuscript as one `.odt` per chapter plus an `.odm` master
    /// that links them, which is the shape the snowflake template expects.
    ///
    /// The per-chapter files are ordinary documents and are the useful part.
    /// The master is a shell: LibreOffice does not follow its section links on
    /// load without being asked to update them, so treat it as a starting point
    /// rather than as the assembled book.
    pub(super) fn export_master(&mut self) {
        self.save_current();
        let chapters = self.collect_chapters();
        if chapters.is_empty() {
            self.status = "Nothing to export — the manuscript is empty".to_string();
            return;
        }
        let meta = self.doc_meta(&chapters);
        let out = PathBuf::from(self.export_input.trim()).with_extension("odm");
        if let Some(parent) = out.parent() {
            let _ = std::fs::create_dir_all(parent);
        }
        match odt::export_master(&chapters, &meta, &out) {
            Ok(written) => {
                self.status = format!(
                    "Wrote {} chapter file(s) beside {}",
                    written.len(),
                    out.display()
                );
            }
            Err(e) => self.status = format!("Export failed: {e}"),
        }
    }

    /// The manuscript as chapters, ready for either export path.
    fn collect_chapters(&self) -> Vec<Chapter> {
        let marker = self.config.draft_marker.clone();
        let pad_width = self.index_pad_width();
        self.manuscript_files()
            .into_iter()
            .map(|(i, name)| {
                let raw = std::fs::read_to_string(self.path_for(name)).unwrap_or_default();
                let header = crate::preprocess::parse(&raw, &marker);
                Chapter {
                    title: resolve_chapter_title(
                        self.titles.get(name).map(String::as_str),
                        header.title.as_deref(),
                        i,
                        pad_width,
                    ),
                    slug: header.slug.clone(),
                    markdown: header.body,
                }
            })
            .collect()
    }

    pub(super) fn export_odt(&mut self) {
        self.save_current();
        let marker = self.config.draft_marker.clone();
        let pad_width = self.index_pad_width();
        let mut chapters = Vec::new();
        for (i, name) in self.manuscript_files() {
            let raw = std::fs::read_to_string(self.path_for(name)).unwrap_or_default();
            // Strip comments + the editorial header, and lift out any
            // `# Title:` / `# Slug:` metadata.
            let header = crate::preprocess::parse(&raw, &marker);

            // Title priority: manual override > `# Title:` metadata > the chapter's
            // 1-based position (e.g. "3."). The body from `parse` is used as-is.
            let title = resolve_chapter_title(
                self.titles.get(name).map(String::as_str),
                header.title.as_deref(),
                i,
                pad_width,
            );
            chapters.push(Chapter {
                title,
                slug: header.slug.clone(),
                markdown: header.body,
            });
        }
        let out = PathBuf::from(self.export_input.trim());
        if let Some(parent) = out.parent() {
            let _ = std::fs::create_dir_all(parent);
        }
        let meta = self.doc_meta(&chapters);
        match odt::export(&chapters, &meta, &out) {
            Ok(_) => {
                self.config.export_path = out.clone();
                self.config.save();
                self.status = format!("Exported {} chapter(s) to {}", chapters.len(), out.display());
            }
            Err(e) => self.status = format!("Export failed: {e}"),
        }
    }

    /// Open a native folder picker to choose the workspace directory.
    pub(super) fn browse_workspace(&mut self) {
        let start = PathBuf::from(self.workspace_input.trim());
        let mut dialog = rfd::FileDialog::new().set_title("Choose workspace folder");
        if start.is_dir() {
            dialog = dialog.set_directory(&start);
        }
        if let Some(path) = dialog.pick_folder() {
            self.save_current();
            self.workspace_input = path.display().to_string();
            self.config.workspace = path;
            self.config.save();
            self.open_workspace();
        }
    }

    /// Open a native save dialog to choose the export `.odt` path.
    pub(super) fn browse_export(&mut self) {
        let current = PathBuf::from(self.export_input.trim());
        let mut dialog = rfd::FileDialog::new()
            .set_title("Choose export file")
            .add_filter("OpenDocument Text", &["odt"]);
        if let Some(parent) = current.parent().filter(|p| p.is_dir()) {
            dialog = dialog.set_directory(parent);
        }
        let name = current
            .file_name()
            .and_then(|s| s.to_str())
            .unwrap_or("manuscript.odt");
        if let Some(mut path) = dialog.set_file_name(name).save_file() {
            // Ensure the chosen path ends in .odt even if the user omitted it.
            let has_odt = path
                .extension()
                .and_then(|e| e.to_str())
                .is_some_and(|e| e.eq_ignore_ascii_case("odt"));
            if !has_odt {
                path.set_extension("odt");
            }
            self.export_input = path.display().to_string();
            self.config.export_path = path;
            self.config.save();
        }
    }

    /// Apply a file-panel drag-and-drop: move the file into the drop's folder on
    /// disk when that changed, then reposition it in the manuscript order.
    pub(super) fn apply_drop(&mut self, drop: FileDrop) {
        let FileDrop { from, to, dir } = drop;
        let Some(old) = self.files.get(from).cloned() else {
            return;
        };
        if parent_dir(&old) == dir {
            self.status = "Reordered".to_string();
        } else {
            let new = join_rel(&dir, base_name(&old));
            if self.path_for(&new).exists() {
                self.status = format!("{new} already exists");
                return;
            }
            // Flush pending edits under the old name before the file moves.
            self.save_current();
            if let Err(e) = self.relocate(&old, &new) {
                self.status = format!("Move failed: {e}");
                return;
            }
            self.files[from] = new;
            self.status = match dir.as_str() {
                "" => format!("Moved {} to the workspace root", base_name(&old)),
                dir => format!("Moved {} into {dir}", base_name(&old)),
            };
        }
        self.reorder(from, to);
    }

    /// Move the file at `from` to flat position `to`, then re-normalise into
    /// folder-tree order so the panel and the export stay in step.
    pub(super) fn reorder(&mut self, from: usize, mut to: usize) {
        if from >= self.files.len() {
            return;
        }
        // Remember the selected file by name so selection follows the move.
        let selected_name = self.selected.and_then(|i| self.files.get(i)).cloned();

        let item = self.files.remove(from);
        if from < to {
            to -= 1;
        }
        to = to.min(self.files.len());
        self.files.insert(to, item);
        self.files = order::tree_order(&self.files);
        self.persist_order();

        if let Some(name) = selected_name {
            self.selected = self.files.iter().position(|n| *n == name);
        }
    }

    /// Settings dialog for the markdown seeded into template-backed new files.
    pub(super) fn template_settings_window(&mut self, ctx: &egui::Context) {
        let mut open = self.show_template_settings;
        let mut close_clicked = false;
        egui::Window::new("New-file template")
            .open(&mut open)
            .resizable(true)
            .collapsible(false)
            .default_width(430.0)
            .show(ctx, |ui| {
                let mut save_now = false;
                ui.label(
                    egui::RichText::new(
                        "Seeded into files made with “＋ New from template” in the file list.",
                    )
                    .small()
                    .weak(),
                );
                ui.add_space(4.0);
                let r = ui.add(
                    egui::TextEdit::multiline(&mut self.config.new_file_template)
                        .code_editor()
                        .desired_width(f32::INFINITY)
                        .desired_rows(12),
                );
                save_now |= r.lost_focus();

                ui.add_space(4.0);
                ui.label(egui::RichText::new("Placeholders").strong());
                egui::Grid::new("template_placeholders")
                    .num_columns(2)
                    .spacing([10.0, 2.0])
                    .show(ui, |ui| {
                        for (token, meaning) in [
                            ("{{name}}", "the file stem, e.g. untitled-3"),
                            ("{{marker}}", "the draft marker set in the toolbar"),
                            ("{{date}}", "today's date (UTC), as YYYY-MM-DD"),
                        ] {
                            ui.label(egui::RichText::new(token).monospace());
                            ui.label(egui::RichText::new(meaning).weak());
                            ui.end_row();
                        }
                    });

                ui.add_space(4.0);
                ui.label(
                    egui::RichText::new(
                        "Leave the box empty to go back to the built-in default.",
                    )
                    .small()
                    .weak(),
                );
                ui.separator();
                ui.horizontal(|ui| {
                    if ui.button("Close").clicked() {
                        close_clicked = true;
                    }
                    if ui
                        .button("Reset to default")
                        .on_hover_text("Replace the box with the built-in template")
                        .clicked()
                    {
                        self.config.new_file_template =
                            crate::config::default_new_file_template();
                        save_now = true;
                    }
                });
                if save_now {
                    self.config.save();
                }
            });

        let now_open = open && !close_clicked;
        if self.show_template_settings && !now_open {
            self.config.save();
        }
        self.show_template_settings = now_open;
    }
}

/// Index of the first file the panel lists, which is the one to open a
/// workspace on.
///
/// In a project the panel shows the manuscript, so landing on `files[0]` would
/// open whatever sorts first across the whole project — a scratch-pad note,
/// typically — and in a file the user cannot see in the tree. Reference files
/// are still the fallback, for a project whose manuscript folder is empty.
/// Which folder to treat as the project root, from state the app already holds.
///
/// Split out from [`App::project_root`] so the choice can be exercised without
/// standing up a whole `App`.
fn project_root_of<'a>(
    workspace: &'a Path,
    in_project_mode: bool,
    repo_root: Option<&'a Path>,
    pending_repo: Option<&'a Path>,
) -> &'a Path {
    if in_project_mode {
        return workspace;
    }
    repo_root.or(pending_repo).unwrap_or(workspace)
}

pub(super) fn first_listed(files: &[String], manuscript_dir: Option<&str>) -> Option<usize> {
    let in_book = |name: &String| match manuscript_dir {
        Some(dir) => is_within(name, dir),
        None => true,
    };
    files
        .iter()
        .position(in_book)
        .or_else(|| (!files.is_empty()).then_some(0))
}

/// The listed file nearest `idx` after a removal: the next one down, else the
/// last one before it, else whatever is left.
pub(super) fn nearest_listed(
    files: &[String],
    manuscript_dir: Option<&str>,
    idx: usize,
) -> Option<usize> {
    let in_book = |i: &usize| match manuscript_dir {
        Some(dir) => is_within(&files[*i], dir),
        None => true,
    };
    (idx..files.len())
        .find(in_book)
        .or_else(|| (0..idx.min(files.len())).rev().find(in_book))
        .or_else(|| first_listed(files, manuscript_dir))
}

/// Where the manuscript exports to for `workspace`, given the `current` export
/// path.
///
/// The folder is always the workspace (the project root). The file name is kept
/// when it looks chosen — anything but the fallback `manuscript` or an echo of
/// the folder the file sits in, both of which we generate ourselves.
fn export_path_for(workspace: &Path, current: &Path) -> PathBuf {
    let stem = current.file_stem().and_then(|s| s.to_str()).unwrap_or("");
    let old_folder = current
        .parent()
        .and_then(|p| p.file_name())
        .and_then(|n| n.to_str())
        .unwrap_or("");
    let generated = stem.is_empty()
        || stem.eq_ignore_ascii_case("manuscript")
        || stem.eq_ignore_ascii_case(old_folder);
    let name = if generated {
        let folder = workspace
            .file_name()
            .and_then(|n| n.to_str())
            .unwrap_or("manuscript");
        format!("{folder}.odt")
    } else {
        current
            .file_name()
            .and_then(|n| n.to_str())
            .unwrap_or("manuscript.odt")
            .to_string()
    };
    workspace.join(name)
}

/// Delete `dir` (workspace-relative) and every parent it leaves childless, so
/// the tree stops drawing branches nothing lives in any more. `remove_dir`
/// refuses to touch a non-empty directory, which is exactly the guard wanted
/// here; an empty `dir` is the workspace itself and is left alone.
pub(super) fn prune_empty_dirs(workspace: &Path, dir: &str) {
    let mut dir = dir;
    while !dir.is_empty() {
        if std::fs::remove_dir(workspace.join(dir)).is_err() {
            break;
        }
        dir = parent_dir(dir);
    }
}

/// Move a manuscript file within the workspace, creating the destination folder
/// and pruning the source folder when the move empties it.
pub(super) fn move_manuscript_file(
    workspace: &Path,
    old: &str,
    new: &str,
) -> std::io::Result<()> {
    let new_path = workspace.join(new);
    if let Some(parent) = new_path.parent() {
        std::fs::create_dir_all(parent)?;
    }
    std::fs::rename(workspace.join(old), &new_path)?;
    prune_empty_dirs(workspace, parent_dir(old));
    Ok(())
}

/// First free `untitled-N.md`, so the template button needs no typed name.
/// `is_taken` reports names already used on disk or in the manuscript order.
pub(super) fn next_untitled_name(is_taken: impl Fn(&str) -> bool) -> String {
    for n in 1..=9_999 {
        let name = format!("untitled-{n}.md");
        if !is_taken(&name) {
            return name;
        }
    }
    // Absurdly unlikely; fall back to something guaranteed unique-ish.
    format!("untitled-{}.md", chrono_like_timestamp().trim_start_matches('@'))
}

/// Expand the template placeholders and guarantee a trailing newline.
pub(super) fn render_template(template: &str, stem: &str, marker: &str, date: &str) -> String {
    let mut out = template
        .replace("{{name}}", stem)
        .replace("{{marker}}", marker)
        .replace("{{date}}", date);
    if !out.ends_with('\n') {
        out.push('\n');
    }
    out
}

#[cfg(test)]
mod tests {
    use super::*;

    /// The folder the "open the project folder" button points at, across the
    /// shapes a workspace can take.
    #[test]
    fn the_project_root_is_the_folder_the_manuscript_sits_in() {
        let ws = Path::new("/books/My Book/06-First Draft");
        let project = Path::new("/books/My Book");

        // Project mode: the workspace already is the project root, so an
        // enclosing repository must not pull the answer above it.
        assert_eq!(
            project_root_of(project, true, Some(Path::new("/books")), None),
            project
        );

        // The draft folder opened on its own, inside an adopted repository.
        assert_eq!(project_root_of(ws, false, Some(project), None), project);

        // The same, while the repository is still awaiting confirmation:
        // showing a folder is a smaller question than committing to it.
        assert_eq!(project_root_of(ws, false, None, Some(project)), project);

        // An adopted repository wins over a stale pending one.
        assert_eq!(
            project_root_of(ws, false, Some(project), Some(Path::new("/books"))),
            project
        );

        // A plain, unversioned folder of chapters has no project around it, so
        // the workspace stands in rather than a guessed-at parent.
        assert_eq!(project_root_of(ws, false, None, None), ws);
    }

    #[test]
    fn untitled_name_fills_the_first_free_slot() {
        assert_eq!(next_untitled_name(|_| false), "untitled-1.md");
        let taken = ["untitled-1.md", "untitled-2.md"];
        assert_eq!(
            next_untitled_name(|n| taken.contains(&n)),
            "untitled-3.md"
        );
        // A gap is reused rather than skipped.
        let sparse = ["untitled-1.md", "untitled-3.md"];
        assert_eq!(
            next_untitled_name(|n| sparse.contains(&n)),
            "untitled-2.md"
        );
    }

    #[test]
    fn render_template_expands_every_placeholder() {
        let out = render_template(
            "# Title: {{name}}\n# Started: {{date}}\n\n{{marker}}\n",
            "untitled-7",
            "### Rough Draft:",
            "2026-08-22",
        );
        assert_eq!(
            out,
            "# Title: untitled-7\n# Started: 2026-08-22\n\n### Rough Draft:\n"
        );
    }

    #[test]
    fn render_template_repeats_and_leaves_unknown_tokens_alone() {
        let out = render_template("{{name}}/{{name}} {{nope}}", "a", "M", "D");
        assert_eq!(out, "a/a {{nope}}\n");
    }

    #[test]
    fn render_template_always_ends_with_a_newline() {
        assert!(render_template("no trailing newline", "n", "m", "d").ends_with('\n'));
        // An already-terminated template doesn't collect a second one.
        assert_eq!(render_template("done\n", "n", "m", "d"), "done\n");
    }

    #[test]
    fn render_template_tolerates_an_empty_marker() {
        // An empty draft_marker disables header splitting; the line goes blank.
        assert_eq!(render_template("a\n{{marker}}\nb\n", "n", "", "d"), "a\n\nb\n");
    }

    /// The point of the default template is that the app's own header parser
    /// understands what it produces — otherwise the seeded fields are just text.
    #[test]
    fn default_template_round_trips_through_the_header_parser() {
        let marker = crate::config::default_marker();
        let seeded = render_template(
            &crate::config::default_new_file_template(),
            "chapter-01",
            &marker,
            "2026-08-22",
        );
        let h = crate::preprocess::parse(&seeded, &marker);
        assert_eq!(h.title.as_deref(), Some("chapter-01"));
        // Slug/POV are seeded blank, so they parse as absent rather than empty.
        assert_eq!(h.slug, None);
        assert_eq!(h.pov, None);
        assert_eq!(h.goal, None);
        // Nothing above the marker leaks into the exported prose.
        assert_eq!(h.body.trim(), "");
    }

    /// A filled-in template parses into the fields the file list displays.
    #[test]
    fn filled_template_parses_into_header_fields() {
        let marker = crate::config::default_marker();
        let seeded = render_template(
            "# Title: {{name}}\n# Slug: the door\n# POV: Ada\n\
             # Word Count Target: 1500 - 2000\n\n{{marker}}\n\nReal prose here.\n",
            "chapter-02",
            &marker,
            "2026-08-22",
        );
        let h = crate::preprocess::parse(&seeded, &marker);
        assert_eq!(h.title.as_deref(), Some("chapter-02"));
        assert_eq!(h.slug.as_deref(), Some("the door"));
        assert_eq!(h.pov.as_deref(), Some("Ada"));
        assert!(h.goal.is_some(), "word-count target should parse");
        assert_eq!(h.body.trim(), "Real prose here.");
    }

    #[test]
    fn default_template_renders_to_a_usable_header() {
        let out = render_template(
            &crate::config::default_new_file_template(),
            "chapter-01",
            "### Rough Draft:",
            "2026-08-22",
        );
        assert!(out.starts_with("# Title: chapter-01\n"), "got {out:?}");
        assert!(out.contains("\n### Rough Draft:\n"), "got {out:?}");
        assert!(!out.contains("{{"), "placeholder left unexpanded in {out:?}");
    }

    #[test]
    fn opening_a_project_moves_a_generated_export_name_with_it() {
        let out = export_path_for(
            Path::new("/books/The Winter Gate"),
            Path::new("/books/Salt Road/Salt Road.odt"),
        );
        assert_eq!(
            out,
            PathBuf::from("/books/The Winter Gate/The Winter Gate.odt")
        );
    }

    #[test]
    fn a_chosen_export_name_survives_the_move_to_the_new_root() {
        let out = export_path_for(
            Path::new("/books/The Winter Gate"),
            Path::new("/books/Salt Road/submission draft.odt"),
        );
        assert_eq!(
            out,
            PathBuf::from("/books/The Winter Gate/submission draft.odt")
        );
    }

    #[test]
    fn the_default_export_name_is_re_derived_rather_than_kept() {
        let out = export_path_for(
            Path::new("/books/The Winter Gate"),
            Path::new("/home/writer/Manuscript/manuscript.odt"),
        );
        assert_eq!(
            out,
            PathBuf::from("/books/The Winter Gate/The Winter Gate.odt")
        );
    }

    #[test]
    fn reopening_the_same_workspace_leaves_the_export_untouched() {
        let ws = Path::new("/books/The Winter Gate");
        let current = PathBuf::from("/books/The Winter Gate/submission draft.odt");
        assert_eq!(export_path_for(ws, &current), current);
    }

    /// Build a throwaway workspace containing `files` and hand back its path.
    fn scratch_ws(tag: &str, files: &[&str]) -> PathBuf {
        let dir = std::env::temp_dir().join(format!("md_manuscript_ws_{tag}"));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        for rel in files {
            let path = dir.join(rel);
            std::fs::create_dir_all(path.parent().unwrap()).unwrap();
            std::fs::write(&path, "x").unwrap();
        }
        dir
    }

    #[test]
    fn moving_a_file_creates_the_destination_and_clears_the_source_folder() {
        let ws = scratch_ws("move", &["part-1/ch-01.md"]);
        move_manuscript_file(&ws, "part-1/ch-01.md", "part-2/ch-01.md").unwrap();
        assert!(ws.join("part-2/ch-01.md").is_file());
        assert!(!ws.join("part-1").exists(), "the emptied folder should go");
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn moving_a_file_leaves_a_folder_that_still_holds_others() {
        let ws = scratch_ws("move_keep", &["p/a.md", "p/b.md"]);
        move_manuscript_file(&ws, "p/a.md", "a.md").unwrap();
        assert!(ws.join("a.md").is_file());
        assert!(ws.join("p/b.md").is_file());
        assert!(ws.join("p").is_dir(), "a folder with files left must survive");
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn moving_into_a_folder_that_does_not_exist_yet_creates_it() {
        let ws = scratch_ws("move_new", &["a.md"]);
        move_manuscript_file(&ws, "a.md", "part-3/deep/a.md").unwrap();
        assert!(ws.join("part-3/deep/a.md").is_file());
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn moving_a_missing_file_fails_without_disturbing_the_workspace() {
        let ws = scratch_ws("move_missing", &["a.md"]);
        assert!(move_manuscript_file(&ws, "nope.md", "p/nope.md").is_err());
        assert!(ws.join("a.md").is_file());
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn pruning_walks_up_through_every_folder_it_empties() {
        let ws = scratch_ws("prune", &["a/b/c/only.md", "keep.md"]);
        std::fs::remove_file(ws.join("a/b/c/only.md")).unwrap();
        prune_empty_dirs(&ws, "a/b/c");
        assert!(!ws.join("a").exists(), "the whole empty chain should go");
        assert!(ws.join("keep.md").is_file());
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn pruning_stops_at_the_first_folder_still_holding_something() {
        let ws = scratch_ws("prune_stop", &["a/keep.md", "a/b/gone.md"]);
        std::fs::remove_file(ws.join("a/b/gone.md")).unwrap();
        prune_empty_dirs(&ws, "a/b");
        assert!(!ws.join("a/b").exists());
        assert!(ws.join("a").is_dir(), "`a` still holds keep.md");
        let _ = std::fs::remove_dir_all(&ws);
    }

    #[test]
    fn pruning_never_removes_the_workspace_itself() {
        let ws = scratch_ws("prune_root", &[]);
        prune_empty_dirs(&ws, "");
        assert!(ws.is_dir());
        let _ = std::fs::remove_dir_all(&ws);
    }

    fn v(items: &[&str]) -> Vec<String> {
        items.iter().map(|s| s.to_string()).collect()
    }

    /// The real shape of the bug: the scratch pad sorts first, so opening a
    /// project landed on a note that the panel does not even list.
    #[test]
    fn opening_a_project_lands_in_the_manuscript() {
        let files = v(&[
            "00-Scratch Pad/Generated plot points.md",
            "03-Characters/ada.md",
            "06-First Draft/Act 1/scene01.md",
            "06-First Draft/draft_v1.md",
        ]);
        assert_eq!(first_listed(&files, Some("06-First Draft")), Some(2));
    }

    #[test]
    fn a_plain_folder_still_opens_on_its_first_file() {
        let files = v(&["a.md", "b.md"]);
        assert_eq!(first_listed(&files, None), Some(0));
        assert_eq!(first_listed(&[], None), None);
    }

    /// A project whose manuscript folder holds nothing yet still has to open
    /// something rather than nothing.
    #[test]
    fn an_empty_manuscript_falls_back_to_the_first_file() {
        let files = v(&["00-Scratch Pad/note.md", "03-Characters/ada.md"]);
        assert_eq!(first_listed(&files, Some("06-First Draft")), Some(0));
    }

    #[test]
    fn after_a_removal_the_next_listed_file_is_chosen() {
        let files = v(&[
            "00-Scratch Pad/note.md",
            "06-First Draft/a.md",
            "06-First Draft/b.md",
        ]);
        // Removing index 1 leaves the following manuscript file at index 1.
        assert_eq!(nearest_listed(&files, Some("06-First Draft"), 1), Some(1));
        // Removing the last one falls back to the previous manuscript file.
        assert_eq!(nearest_listed(&files, Some("06-First Draft"), 3), Some(2));
    }

    #[test]
    fn a_removal_never_lands_on_a_reference_file() {
        let files = v(&["00-Scratch Pad/note.md", "06-First Draft/a.md"]);
        // Index 2 is past the end; the search back must skip the scratch pad.
        assert_eq!(nearest_listed(&files, Some("06-First Draft"), 2), Some(1));
    }

    #[test]
    fn removing_the_only_manuscript_file_still_selects_something() {
        let files = v(&["00-Scratch Pad/note.md"]);
        assert_eq!(nearest_listed(&files, Some("06-First Draft"), 0), Some(0));
        assert_eq!(nearest_listed(&[], Some("06-First Draft"), 0), None);
    }
}