kimun_notes/app_screen/

panel_set.rs

//! `PanelOrder` — the pure focus/order/visibility state machine for the
//! editor screen's persistent **Panels**. Keyed only on `PanelKind`, so it
//! carries no vault or heavy component state and is testable in isolation.
//! `PanelSet` (below) composes it with the concrete panels.

use std::sync::Arc;

use crate::server_client::RagClient;
use ratatui::Frame;
use ratatui::crossterm::event::{MouseButton, MouseEventKind};
use ratatui::layout::{Constraint, Direction, Layout, Position, Rect};

use crate::components::Component;
use crate::components::activity_rail::{ActivityRail, RAIL_WIDTH, RailCaps};
use crate::components::ask_thread::ThreadPanel;
use crate::components::attachment_view::AttachmentView;
use crate::components::drawer::{DrawerHost, DrawerView};
use crate::components::event_state::EventState;
use crate::components::events::{AppTx, InputEvent};
use crate::components::panel::{PanelKind, panel_block};
use crate::components::query_panel::QueryPanel;
use crate::components::sidebar::SidebarComponent;
use crate::components::text_editor::TextEditorComponent;
use crate::settings::themes::Theme;

/// Default drawer width in columns. Resizable at runtime by dragging the
/// drawer↔editor divider.
const DEFAULT_DRAWER_WIDTH: u16 = 34;
/// Narrowest the drawer can be dragged.
const MIN_DRAWER_WIDTH: u16 = 20;
/// Columns that must always remain for the editor when dragging the divider.
const MIN_EDITOR_WIDTH: u16 = 20;

struct Slot {
    kind: PanelKind,
    visible: bool,
}

/// Ordered panels + which one is focused. The layout is fixed left→right:
/// rail → drawer → editor. The rail and the editor are always visible; the
/// drawer toggles. Focus tracks a panel by kind and cycles over the visible
/// panels, wrapping at both ends.
pub struct PanelOrder {
    slots: Vec<Slot>,
    focus: usize,
}

impl PanelOrder {
    /// Default layout: rail → drawer (visible) → editor (focused).
    pub fn new() -> Self {
        let slots = vec![
            Slot {
                kind: PanelKind::Rail,
                visible: true,
            },
            Slot {
                kind: PanelKind::Drawer,
                visible: true,
            },
            Slot {
                kind: PanelKind::Editor,
                visible: true,
            },
        ];
        let focus = slots
            .iter()
            .position(|s| s.kind == PanelKind::Editor)
            .expect("editor slot present");
        Self { slots, focus }
    }

    /// The currently focused panel.
    pub fn focused(&self) -> PanelKind {
        self.slots[self.focus].kind
    }

    /// The visible panel one step left of focus, wrapping at the left end.
    pub fn prev_kind(&self) -> Option<PanelKind> {
        self.step(|i, n| (i + n - 1) % n)
    }

    /// The visible panel one step right of focus, wrapping at the right end.
    pub fn next_kind(&self) -> Option<PanelKind> {
        self.step(|i, n| (i + 1) % n)
    }

    /// Step through the *visible* panels from the focused one.
    fn step(&self, advance: impl Fn(usize, usize) -> usize) -> Option<PanelKind> {
        let visible = self.visible_in_order();
        let n = visible.len();
        if n < 2 {
            return None;
        }
        let i = visible.iter().position(|&k| k == self.focused())?;
        Some(visible[advance(i, n)])
    }

    /// Move focus to `kind`. No-op if the kind is not present.
    pub fn focus(&mut self, kind: PanelKind) {
        if let Some(i) = self.slots.iter().position(|s| s.kind == kind) {
            self.focus = i;
        }
    }

    /// Whether `kind` is currently visible.
    pub fn is_visible(&self, kind: PanelKind) -> bool {
        self.slots
            .iter()
            .find(|s| s.kind == kind)
            .is_some_and(|s| s.visible)
    }

    /// Reveal `kind`.
    pub fn show(&mut self, kind: PanelKind) {
        if let Some(s) = self.slots.iter_mut().find(|s| s.kind == kind) {
            s.visible = true;
        }
    }

    /// Hide `kind`. The rail and the editor are always visible, so hiding
    /// them is a no-op.
    pub fn hide(&mut self, kind: PanelKind) {
        if kind == PanelKind::Editor || kind == PanelKind::Rail {
            return;
        }
        if let Some(s) = self.slots.iter_mut().find(|s| s.kind == kind) {
            s.visible = false;
        }
        // If focus was on the panel we just hid, move it to the nearest
        // visible panel (the editor is always visible, so a target exists).
        if !self.slots[self.focus].visible {
            self.focus = self.nearest_visible(self.focus);
        }
    }

    /// The visible panels in their current left→right order. Drives the
    /// render layout: each panel contributes one column in this sequence.
    pub fn visible_in_order(&self) -> Vec<PanelKind> {
        self.slots
            .iter()
            .filter(|s| s.visible)
            .map(|s| s.kind)
            .collect()
    }

    /// Index of the nearest visible slot, searching outward from `from`.
    /// Falls back to `from` if somehow nothing is visible (cannot happen —
    /// the editor is always visible).
    fn nearest_visible(&self, from: usize) -> usize {
        let n = self.slots.len();
        (1..n)
            .flat_map(|d| [from.checked_sub(d), Some(from + d).filter(|&i| i < n)])
            .flatten()
            .find(|&i| self.slots[i].visible)
            .unwrap_or(from)
    }
}

impl Default for PanelOrder {
    fn default() -> Self {
        Self::new()
    }
}

/// Column width a panel occupies when laid out. The rail is fixed, the
/// drawer is runtime-resizable, and the editor fills the remainder.
fn panel_column(kind: PanelKind, drawer_width: u16) -> Constraint {
    match kind {
        PanelKind::Rail => Constraint::Length(RAIL_WIDTH),
        PanelKind::Drawer => Constraint::Length(drawer_width),
        PanelKind::Editor => Constraint::Min(0),
    }
}

/// Lay `visible` out left→right as one column per panel. Shared by `render`
/// and mouse hit-testing so clicks are always tested against the same rects
/// the panels were drawn into.
fn layout_columns(visible: &[PanelKind], area: Rect, drawer_width: u16) -> Vec<(PanelKind, Rect)> {
    let constraints: Vec<Constraint> = visible
        .iter()
        .map(|k| panel_column(*k, drawer_width))
        .collect();
    let columns = Layout::default()
        .direction(Direction::Horizontal)
        .constraints(constraints)
        .split(area);
    visible
        .iter()
        .copied()
        .zip(columns.iter().copied())
        .collect()
}

/// The panel whose column contains the given screen cell, if any.
fn kind_at(columns: &[(PanelKind, Rect)], column: u16, row: u16) -> Option<PanelKind> {
    columns
        .iter()
        .find(|(_, rect)| rect.contains(Position::new(column, row)))
        .map(|(kind, _)| *kind)
}

/// Which content the editor *area* currently shows — a pure selector, not a
/// container. The heavy stateful panels are
/// permanent residents of `PanelSet`: the note editor is `PanelSet::editor`
/// and the Ask workspace's conversation thread is `PanelSet::ask`, each living
/// for the whole screen lifetime regardless of which content is selected — so
/// their state (a live nvim backend, undo history, the conversation) survives
/// switching the area away and back. Only the read-only attachment view is
/// owned by its arm here, since it carries no state worth preserving. Exactly
/// one variant is active at a time.
enum EditorAreaContent {
    Note,
    // Boxed: `AttachmentView` can hold a full text-file preview plus
    // icons/key bindings — boxing keeps the enum from ballooning to the size
    // of that arm.
    Attachment(Box<AttachmentView>),
    /// Selects the resident `PanelSet::ask` for display (unit — the thread
    /// panel itself lives on `PanelSet`, not in this variant).
    Ask,
}

/// The editor screen's persistent **Panels** — the activity rail, the single
/// drawer, and the editor — plus the `PanelOrder` that decides visibility and
/// which one is focused. Routes input and render to the focused / visible
/// panels; the host (`EditorScreen`) reaches a specific drawer view through
/// the typed accessors for view-specific calls.
pub struct PanelSet {
    order: PanelOrder,
    rail: ActivityRail,
    drawer: DrawerHost,
    /// The note editor. Retained for the whole screen lifetime — including
    /// while an attachment or the Ask workspace is shown — so its backend
    /// (e.g. a live nvim process) and undo history survive the round trip.
    editor: TextEditorComponent,
    /// The Ask workspace's conversation thread + composer. Like `editor`, a
    /// permanent resident: retained for the whole screen lifetime so the
    /// conversation survives switching the editor area to another view and
    /// back, the same way the note editor does. Owns its own `RagClient`. Shown only
    /// when `content` is `EditorAreaContent::Ask`.
    ask: ThreadPanel,
    /// Which content the editor *area* currently shows: the note editor
    /// (resident `editor`), a read-only attachment view, or the Ask workspace
    /// (resident `ask`). See `EditorAreaContent`.
    content: EditorAreaContent,
    /// Current drawer width in columns (divider-draggable).
    drawer_width: u16,
    /// Whether a divider drag is in progress.
    dragging_divider: bool,
    /// The column each visible panel was drawn into on the last render —
    /// the single source of truth for mouse hit-testing. Empty until the
    /// first render.
    column_rects: Vec<(PanelKind, Rect)>,
}

impl PanelSet {
    pub fn from_panels(
        drawer: DrawerHost,
        editor: TextEditorComponent,
        icons: crate::settings::icons::Icons,
        key_bindings: crate::keys::KeyBindings,
        rail_caps: RailCaps,
    ) -> Self {
        let mut ask = ThreadPanel::new();
        ask.set_icons(icons.clone());
        Self {
            order: PanelOrder::new(),
            rail: ActivityRail::new(key_bindings, icons, rail_caps),
            drawer,
            editor,
            ask,
            content: EditorAreaContent::Note,
            drawer_width: DEFAULT_DRAWER_WIDTH,
            dragging_divider: false,
            column_rects: Vec::new(),
        }
    }

    /// Rebuild the activity rail with fresh feature visibility — the runtime
    /// path for SEM/ASK appearing or disappearing (RAG status change). Keeps
    /// the rail cursor on the drawer's active view so navigation continues
    /// from there.
    pub fn rebuild_rail(
        &mut self,
        key_bindings: crate::keys::KeyBindings,
        icons: crate::settings::icons::Icons,
        rail_caps: RailCaps,
    ) {
        let active = self.drawer.active_view();
        self.ask.set_icons(icons.clone());
        self.rail = ActivityRail::new(key_bindings, icons, rail_caps);
        self.rail.set_cursor(active);
    }

    /// Whether the activity rail currently shows `view` (feature gate on).
    #[cfg(test)]
    pub fn rail_shows(&self, view: DrawerView) -> bool {
        self.rail.shows(view)
    }

    /// The single injection point for the live RAG client: hands it to the
    /// resident Ask panel, which derives its composer-enabled state from the
    /// client's presence (a present client enables submission,
    /// `None` disables it without evicting the thread). Because the panel is
    /// resident, one call keeps it correct whether or not Ask is on screen.
    pub fn set_ask_client(&mut self, client: Option<Arc<RagClient>>) {
        self.ask.set_client(client);
    }

    // ── Order / focus / visibility (delegate to PanelOrder) ─────────────────

    pub fn focused(&self) -> PanelKind {
        self.order.focused()
    }

    /// Status-bar label for the focused panel; the drawer resolves to its
    /// active view's label.
    pub fn focused_label(&self) -> &'static str {
        match self.order.focused() {
            PanelKind::Drawer => self.drawer.active_view().label(),
            // The editor area showing the Ask workspace reads as ASK, not
            // EDITOR — mirrors the panel frame's "Ask" title.
            PanelKind::Editor if self.is_showing_ask() => DrawerView::Ask.label(),
            kind => kind.label(),
        }
    }

    pub fn prev_kind(&self) -> Option<PanelKind> {
        self.order.prev_kind()
    }

    pub fn next_kind(&self) -> Option<PanelKind> {
        self.order.next_kind()
    }

    pub fn is_visible(&self, kind: PanelKind) -> bool {
        self.order.is_visible(kind)
    }

    pub fn show(&mut self, kind: PanelKind) {
        self.order.show(kind);
    }

    pub fn hide(&mut self, kind: PanelKind) {
        self.order.hide(kind);
    }

    /// Move focus to `kind`. Any transition away from the editor closes its
    /// autocomplete popup so it doesn't linger while another panel owns input.
    pub fn focus(&mut self, kind: PanelKind) {
        if kind != PanelKind::Editor {
            self.editor.close_autocomplete();
        }
        self.order.focus(kind);
    }

    // ── Drawer view control ─────────────────────────────────────────────────

    pub fn active_drawer_view(&self) -> DrawerView {
        self.drawer.active_view()
    }

    /// Whether the drawer's active view is a text-input context (status-bar
    /// ⌨/≣ indicator).
    pub fn drawer_is_text_input(&self) -> bool {
        self.drawer.is_text_input()
    }

    /// Grow/shrink the drawer by `delta` columns (leader window commands),
    /// clamped to the same bounds the divider drag enforces.
    pub fn adjust_drawer_width(&mut self, delta: i16) {
        // Before the first render there are no rects to clamp against —
        // skip rather than allow an unbounded grow.
        let Some(right) = self.column_rects.iter().map(|(_, r)| r.right()).max() else {
            return;
        };
        let new = self.drawer_width.saturating_add_signed(delta);
        let max_width = right.saturating_sub(RAIL_WIDTH + MIN_EDITOR_WIDTH);
        self.drawer_width = new.clamp(MIN_DRAWER_WIDTH, max_width.max(MIN_DRAWER_WIDTH));
    }

    /// Switch the drawer's active `view` and rail cursor *without* changing
    /// its visibility — for paths that must not force-reveal a drawer the user
    /// explicitly hid (e.g. leaving the Ask workspace when a note opens).
    pub fn switch_drawer_view(&mut self, view: DrawerView) {
        self.drawer.set_view(view);
        self.rail.set_cursor(view);
    }

    /// Switch the drawer to `view` and reveal it. Keeps the rail cursor in
    /// step so keyboard navigation continues from the active item.
    pub fn open_drawer_view(&mut self, view: DrawerView) {
        self.switch_drawer_view(view);
        self.order.show(PanelKind::Drawer);
    }

    // ── Typed accessors for panel-specific calls ───────────────────────────

    pub fn sidebar(&self) -> &SidebarComponent {
        self.drawer.sidebar()
    }
    pub fn sidebar_mut(&mut self) -> &mut SidebarComponent {
        self.drawer.sidebar_mut()
    }
    /// The note editor, or `None` while an attachment or the Ask workspace is
    /// shown in its place. Callers reaching for the editor cross a mode
    /// boundary and must handle that case.
    pub fn editor(&self) -> Option<&TextEditorComponent> {
        matches!(self.content, EditorAreaContent::Note).then_some(&self.editor)
    }
    pub fn editor_mut(&mut self) -> Option<&mut TextEditorComponent> {
        if !matches!(self.content, EditorAreaContent::Note) {
            return None;
        }
        Some(&mut self.editor)
    }

    /// Show `view` in the editor area, replacing any prior attachment/Ask
    /// content and hiding the note editor. Closes the editor's autocomplete
    /// so it can't linger under the attachment, and focuses the editor panel.
    pub fn show_attachment(&mut self, view: AttachmentView) {
        self.editor.close_autocomplete();
        self.content = EditorAreaContent::Attachment(Box::new(view));
        self.order.focus(PanelKind::Editor);
    }

    /// Return the editor area to the note editor, discarding any attachment.
    /// No-op when already showing the editor, and — unlike `hide_ask` — a
    /// no-op when showing the Ask workspace too: this method's contract is
    /// specifically about attachments, so it leaves Ask content alone (use
    /// `hide_ask` for that).
    pub fn clear_attachment(&mut self) {
        if matches!(self.content, EditorAreaContent::Attachment(_)) {
            self.content = EditorAreaContent::Note;
        }
    }

    /// Whether the editor area is currently showing an attachment.
    pub fn is_showing_attachment(&self) -> bool {
        matches!(self.content, EditorAreaContent::Attachment(_))
    }

    /// The vault path of the attachment on show, if any — used to open it with
    /// the OS default program.
    pub fn attachment_path(&self) -> Option<&kimun_core::nfs::VaultPath> {
        match &self.content {
            EditorAreaContent::Attachment(view) => Some(view.path()),
            _ => None,
        }
    }

    /// Select the resident Ask workspace as the editor-area content, hiding
    /// the note editor. Mirrors `show_attachment`: closes the editor's
    /// autocomplete and focuses the editor panel. The thread persists by
    /// residency — this only flips the selector.
    pub fn show_ask(&mut self) {
        self.editor.close_autocomplete();
        self.content = EditorAreaContent::Ask;
        self.order.focus(PanelKind::Editor);
    }

    /// Return the editor area to the note editor when it's showing Ask. The
    /// resident thread panel is untouched — its conversation survives. No-op
    /// for any other content (mirrors `clear_attachment`'s scoping).
    pub fn hide_ask(&mut self) {
        if matches!(self.content, EditorAreaContent::Ask) {
            self.content = EditorAreaContent::Note;
        }
    }

    /// The resident Ask panel (always present; shown only when `content` is
    /// `Ask`).
    pub fn ask(&self) -> &ThreadPanel {
        &self.ask
    }
    /// The resident Ask panel, mutably.
    pub fn ask_mut(&mut self) -> &mut ThreadPanel {
        &mut self.ask
    }

    /// Whether the editor area is currently showing the Ask workspace.
    pub fn is_showing_ask(&self) -> bool {
        matches!(self.content, EditorAreaContent::Ask)
    }

    /// The active editor-area content as a `Component` — the attachment view
    /// or Ask panel when one is shown, otherwise the note editor. Lets
    /// input/hint routing dispatch once instead of branching on
    /// `self.content` at each site. (Render stays separate: it wraps the
    /// editor in its own dirty-title block.)
    fn editor_area(&self) -> &dyn Component {
        match &self.content {
            EditorAreaContent::Attachment(view) => view.as_ref(),
            EditorAreaContent::Ask => &self.ask,
            EditorAreaContent::Note => &self.editor,
        }
    }
    pub fn query(&self) -> &QueryPanel {
        self.drawer.query()
    }
    pub fn query_mut(&mut self) -> &mut QueryPanel {
        self.drawer.query_mut()
    }
    pub fn semantic_mut(&mut self) -> &mut crate::components::semantic_search::SemanticPanel {
        self.drawer.semantic_mut()
    }
    pub fn ask_sources_mut(&mut self) -> &mut crate::components::ask_sources::SourcesPanel {
        self.drawer.ask_sources_mut()
    }
    pub fn tags_mut(&mut self) -> &mut crate::components::drawer_views::TagsPanel {
        self.drawer.tags_mut()
    }
    pub fn links_mut(&mut self) -> &mut crate::components::drawer_views::LinksPanel {
        self.drawer.links_mut()
    }
    pub fn outline_mut(&mut self) -> &mut crate::components::drawer_views::OutlinePanel {
        self.drawer.outline_mut()
    }
    /// Bring the OUTLINE in step with the editor buffer for `note` — empty
    /// while no note editor is shown. Parses only when the buffer revision
    /// moved; see [`OutlinePanel::sync`].
    ///
    /// [`OutlinePanel::sync`]: crate::components::drawer_views::OutlinePanel::sync
    pub fn sync_outline(&mut self, note: &kimun_core::nfs::VaultPath, tx: &AppTx) {
        let editor = matches!(self.content, EditorAreaContent::Note).then_some(&self.editor);
        let revision = editor.map(|e| e.content_revision());
        self.drawer.outline_mut().sync(
            note,
            revision,
            || editor.map(|e| e.get_text()).unwrap_or_default(),
            tx,
        );
    }
    pub fn drawer_set_config_info(&mut self, info: crate::components::drawer::ConfigInfo) {
        self.drawer.set_config_info(info);
    }

    // ── Routing ────────────────────────────────────────────────────────────

    /// Footer hints for the focused panel.
    pub fn focused_hints(&self) -> Vec<(String, String)> {
        match self.order.focused() {
            PanelKind::Rail => self.rail.hint_shortcuts(),
            PanelKind::Drawer => self.drawer.hint_shortcuts(),
            PanelKind::Editor => self.editor_area().hint_shortcuts(),
        }
    }

    /// Route an input event to the focused panel.
    pub fn handle_input(&mut self, event: &InputEvent, tx: &AppTx) -> EventState {
        match self.order.focused() {
            PanelKind::Rail => self.rail.handle_input(event, tx),
            PanelKind::Drawer => self.drawer.handle_input(event, tx),
            PanelKind::Editor => self.editor_area_handle_input(event, tx),
        }
    }

    /// Deliver an input event to the editor-area content. The Ask arm calls
    /// the resident panel's inherent `ThreadPanel::handle_input` (it derives
    /// submission from its own client); the others use the trait. Each arm
    /// borrows a distinct field, disjoint from `content`.
    fn editor_area_handle_input(&mut self, event: &InputEvent, tx: &AppTx) -> EventState {
        match &mut self.content {
            EditorAreaContent::Ask => self.ask.handle_input(event, tx),
            EditorAreaContent::Attachment(view) => view.handle_input(event, tx),
            EditorAreaContent::Note => self.editor.handle_input(event, tx),
        }
    }

    /// Whether a press on this cell points *at* somewhere in the note buffer.
    ///
    /// Three conditions, and only the first is about geometry:
    ///
    /// - **Inside the editor component itself.** Asked of the component, not of
    ///   `Self::column_rects`, because the column is wider than the buffer: it
    ///   also holds the frame `render` draws around the component (and, to its
    ///   left, the divider that [`Self::handle_mouse`] claims before any panel
    ///   sees it). A press on either is out of the component's bounds, so it
    ///   returns `NotConsumed` and the cursor never moves.
    /// - **The editor area is showing the note.** It may instead hold an
    ///   attachment preview or the Ask workspace, neither of which has a cursor
    ///   or a link under the pointer — an attachment would launch an external
    ///   program and Ask would swallow the press.
    /// - **The mouse drives the cursor.** False under the **nvim** backend,
    ///   where a press never moves the cursor at all, so anything reading the
    ///   cursor afterwards reads wherever the *keyboard* left it.
    ///
    /// Every one of them is the same question asked of a different layer: did
    /// this press *place the cursor*? Anything that answers a press by reading
    /// the cursor — following a link, most obviously — has to ask all three, or
    /// it acts on a position the press never set. The column alone was the
    /// original gate, and each of the others was a defect before it was a
    /// condition. Callers that only want the column should not reuse this.
    pub fn is_note_buffer_cell(&self, column: u16, row: u16) -> bool {
        matches!(self.content, EditorAreaContent::Note)
            && self.editor.mouse_drives_cursor()
            && self.editor.covers(column, row)
    }

    /// Whether a mouse event at this cell belongs to the editor column — the
    /// region an **editor claim** may own. False mid divider-drag, so a drag
    /// that sweeps across the editor keeps resizing the drawer.
    pub fn pointer_on_editor(&self, column: u16, row: u16) -> bool {
        !self.dragging_divider
            && kind_at(&self.column_rects, column, row) == Some(PanelKind::Editor)
    }

    /// The divider hit zone: the drawer's right border column (the cell
    /// between drawer content and editor).
    fn on_divider(&self, column: u16, row: u16) -> bool {
        self.column_rects
            .iter()
            .find(|(kind, _)| *kind == PanelKind::Drawer)
            .is_some_and(|(_, rect)| {
                rect.height > 0
                    && column == rect.right().saturating_sub(1)
                    && row >= rect.y
                    && row < rect.bottom()
            })
    }

    /// Apply a divider drag: the drawer's new width follows the cursor,
    /// clamped so both the drawer and the editor keep a usable minimum.
    fn drag_divider_to(&mut self, column: u16) {
        let Some((_, drawer_rect)) = self
            .column_rects
            .iter()
            .find(|(kind, _)| *kind == PanelKind::Drawer)
        else {
            return;
        };
        let total_right = self
            .column_rects
            .iter()
            .map(|(_, r)| r.right())
            .max()
            .unwrap_or(drawer_rect.right());
        let max_width = total_right
            .saturating_sub(drawer_rect.x)
            .saturating_sub(MIN_EDITOR_WIDTH);
        let new_width = column.saturating_sub(drawer_rect.x).saturating_add(1);
        self.drawer_width = new_width.clamp(MIN_DRAWER_WIDTH, max_width.max(MIN_DRAWER_WIDTH));
    }

    /// Route a mouse event by hit-testing the panel columns from the last
    /// render. Dragging the drawer↔editor divider resizes the drawer. A
    /// button-down click focuses the panel under the cursor — the one
    /// consistent click-to-focus rule for every panel — and the event is
    /// then forwarded to that panel for its internal behavior (cursor
    /// placement, list selection, scrolling). Events outside every column
    /// (or before the first render) are not consumed.
    pub fn handle_mouse(&mut self, event: &InputEvent, tx: &AppTx) -> EventState {
        let InputEvent::Mouse(mouse) = event else {
            return EventState::NotConsumed;
        };

        // Divider drag lifecycle.
        match mouse.kind {
            MouseEventKind::Down(MouseButton::Left) if self.on_divider(mouse.column, mouse.row) => {
                self.dragging_divider = true;
                return EventState::Consumed;
            }
            MouseEventKind::Drag(MouseButton::Left) if self.dragging_divider => {
                self.drag_divider_to(mouse.column);
                return EventState::Consumed;
            }
            MouseEventKind::Up(MouseButton::Left) if self.dragging_divider => {
                self.dragging_divider = false;
                return EventState::Consumed;
            }
            _ => {}
        }

        let Some(kind) = kind_at(&self.column_rects, mouse.column, mouse.row) else {
            return EventState::NotConsumed;
        };
        if matches!(mouse.kind, MouseEventKind::Down(_)) {
            self.focus(kind);
        }
        match kind {
            PanelKind::Rail => {
                self.rail.handle_input(event, tx);
            }
            PanelKind::Drawer => {
                self.drawer.handle_mouse(event, tx);
            }
            PanelKind::Editor => {
                self.editor_area_handle_input(event, tx);
            }
        }
        EventState::Consumed
    }

    /// Lay the visible panels out left→right and render each. `show_focus`
    /// is false while an overlay is open, so no panel draws its focused
    /// highlight under the overlay.
    pub fn render(&mut self, f: &mut Frame, area: Rect, theme: &Theme, show_focus: bool) {
        let visible = self.order.visible_in_order();
        if visible.is_empty() {
            return;
        }
        let columns = layout_columns(&visible, area, self.drawer_width);
        self.column_rects = columns.clone();

        let focused = self.order.focused();
        let drawer_view = self
            .is_visible(PanelKind::Drawer)
            .then(|| self.drawer.active_view());
        for (kind, rect) in &columns {
            let is_focused = show_focus && *kind == focused;
            let rect = *rect;
            match kind {
                PanelKind::Rail => self.rail.render(f, rect, theme, is_focused, drawer_view),
                PanelKind::Drawer => self.drawer.render(f, rect, theme, is_focused),
                PanelKind::Editor => {
                    // The editor area's frame is drawn here (not by the
                    // component) so the dirty marker and focus border live with
                    // the layout. The frame title reflects which content the
                    // area is showing — the note editor, an attachment, or Ask.
                    match &mut self.content {
                        EditorAreaContent::Attachment(view) => {
                            let block = panel_block("Attachment", theme, is_focused);
                            let inner = block.inner(rect);
                            f.render_widget(block, rect);
                            view.render(f, inner, theme, is_focused);
                        }
                        EditorAreaContent::Ask => {
                            let block = panel_block("Ask", theme, is_focused);
                            let inner = block.inner(rect);
                            f.render_widget(block, rect);
                            self.ask.render(f, inner, theme, is_focused);
                        }
                        EditorAreaContent::Note => {
                            let title = if self.editor.is_dirty() {
                                "Editor [+]"
                            } else {
                                "Editor"
                            };
                            let block = panel_block(title, theme, is_focused);
                            let inner = block.inner(rect);
                            f.render_widget(block, rect);
                            self.editor.render(f, inner, theme, is_focused);
                        }
                    }
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::settings::AppSettings;
    use crate::test_support::{mouse_down_at, temp_vault};
    use ratatui::crossterm::event::{KeyModifiers, MouseEvent, MouseEventKind};
    use tokio::sync::mpsc::unbounded_channel;

    async fn make_panel_set() -> PanelSet {
        let vault = temp_vault("panelset").await;
        vault.validate_and_init().await.unwrap();
        let settings = AppSettings::default();
        let sidebar = SidebarComponent::new(
            settings.key_bindings.clone(),
            vault.clone(),
            settings.icons(),
            &settings,
        );
        let editor = TextEditorComponent::new(settings.key_bindings.clone(), &settings);
        let query = QueryPanel::new(
            vault.clone(),
            settings.key_bindings.clone(),
            settings.icons(),
        );
        let tags = crate::components::drawer_views::TagsPanel::new(
            vault.clone(),
            settings.icons(),
            settings.yank_combos(),
        );
        let links = crate::components::drawer_views::LinksPanel::new(
            vault.clone(),
            settings.icons(),
            settings.yank_combos(),
        );
        let semantic = crate::components::semantic_search::SemanticPanel::new(
            vault.clone(),
            std::sync::Arc::new(std::sync::RwLock::new(settings.clone())),
            settings.icons(),
            settings.yank_combos(),
        );
        let outline = crate::components::drawer_views::OutlinePanel::new(
            settings.icons(),
            settings.yank_combos(),
        );
        let drawer = DrawerHost::new(
            vault,
            &settings.key_bindings,
            sidebar,
            query,
            semantic,
            tags,
            links,
            outline,
        );
        PanelSet::from_panels(
            drawer,
            editor,
            settings.icons(),
            settings.key_bindings,
            RailCaps {
                semantic: true,
                ask: true,
            },
        )
    }

    /// Lay the visible panels out over a fixed area by actually rendering them.
    ///
    /// Assigning `column_rects` directly would be shorter and wrong: the hit
    /// tests read the editor component's own rect too, and only `render`
    /// assigns that. A layout that sets one and not the other describes a frame
    /// that never existed.
    fn lay_out(panels: &mut PanelSet) {
        let area = Rect::new(0, 0, 120, 40);
        let theme = crate::settings::themes::Theme::default();
        let mut term =
            ratatui::Terminal::new(ratatui::backend::TestBackend::new(area.width, area.height))
                .unwrap();
        term.draw(|f| panels.render(f, area, &theme, true)).unwrap();
    }

    /// A cell in the middle of the editor column, as laid out.
    fn editor_cell(panels: &PanelSet) -> (u16, u16) {
        let (_, rect) = panels
            .column_rects
            .iter()
            .find(|(kind, _)| *kind == PanelKind::Editor)
            .expect("the editor is always visible");
        (rect.x + rect.width / 2, rect.y + rect.height / 2)
    }

    /// The gate is not merely geometric. It read as "the editor column" once,
    /// and a double-click in the Ask workspace was swallowed while one in an
    /// attachment preview spawned an external viewer — the same cell, three
    /// different things underneath it.
    #[tokio::test]
    async fn the_note_buffer_gate_tracks_what_the_editor_area_shows() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (col, row) = editor_cell(&panels);
        assert!(
            panels.is_note_buffer_cell(col, row),
            "the note buffer is what the gate is for"
        );

        panels.show_ask();
        assert!(
            !panels.is_note_buffer_cell(col, row),
            "the Ask workspace has no cursor to point at"
        );

        panels.hide_ask();
        assert!(panels.is_note_buffer_cell(col, row), "and back again");
    }

    /// A divider press is claimed before any panel sees it and never changes
    /// focus, so it must not count as pointing at the buffer either.
    #[tokio::test]
    async fn the_note_buffer_gate_rejects_the_divider_and_other_columns() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (_, drawer) = panels
            .column_rects
            .iter()
            .find(|(kind, _)| *kind == PanelKind::Drawer)
            .expect("the drawer is visible by default");
        let (divider_col, row) = (drawer.right().saturating_sub(1), drawer.y + 1);
        assert!(panels.on_divider(divider_col, row), "precondition");
        assert!(!panels.is_note_buffer_cell(divider_col, row));
        assert!(
            !panels.is_note_buffer_cell(drawer.x + 1, row),
            "and the drawer is not the editor"
        );
    }

    /// The editor *column* is not the editor *buffer*: `PanelSet::render` draws
    /// a bordered frame around the component and hands it only the interior.
    /// A press on the frame is out of the component's bounds, so it returns
    /// `NotConsumed` and the cursor never moves — counting those cells let two
    /// clicks on the `─ Editor` title bar follow whichever link the cursor was
    /// parked on, a note the user never pointed at.
    #[tokio::test]
    async fn the_note_buffer_gate_rejects_the_editor_frame() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (_, rect) = panels
            .column_rects
            .iter()
            .find(|(kind, _)| *kind == PanelKind::Editor)
            .expect("the editor is always visible");
        let rect = *rect;
        let (mid_col, mid_row) = (rect.x + rect.width / 2, rect.y + rect.height / 2);
        assert!(
            panels.is_note_buffer_cell(mid_col, mid_row),
            "precondition: the interior still counts"
        );
        assert!(
            !panels.is_note_buffer_cell(mid_col, rect.y),
            "the title row is frame"
        );
        assert!(
            !panels.is_note_buffer_cell(mid_col, rect.bottom() - 1),
            "so is the bottom border"
        );
        assert!(
            !panels.is_note_buffer_cell(rect.x, mid_row),
            "so is the left border"
        );
        assert!(
            !panels.is_note_buffer_cell(rect.right() - 1, mid_row),
            "so is the right border"
        );
    }

    fn scroll_at(col: u16, row: u16) -> InputEvent {
        InputEvent::Mouse(MouseEvent {
            kind: MouseEventKind::ScrollDown,
            column: col,
            row,
            modifiers: KeyModifiers::NONE,
        })
    }

    fn drag_at(col: u16, row: u16) -> InputEvent {
        InputEvent::Mouse(MouseEvent {
            kind: MouseEventKind::Drag(MouseButton::Left),
            column: col,
            row,
            modifiers: KeyModifiers::NONE,
        })
    }

    fn up_at(col: u16, row: u16) -> InputEvent {
        InputEvent::Mouse(MouseEvent {
            kind: MouseEventKind::Up(MouseButton::Left),
            column: col,
            row,
            modifiers: KeyModifiers::NONE,
        })
    }

    /// A button-down click focuses the panel whose column it lands in — for
    /// every panel, in any prior focus state.
    #[tokio::test]
    async fn click_focuses_panel_under_cursor() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (tx, _rx) = unbounded_channel();

        assert_eq!(panels.focused(), PanelKind::Editor);
        // Rail (0..7) | Drawer (7..41) | Editor (41..120).
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(3, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.focused(), PanelKind::Rail);
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(20, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.focused(), PanelKind::Drawer);
        // Regression: a click on the editor must focus it even while another
        // panel is focused.
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(60, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.focused(), PanelKind::Editor);
    }

    /// Before the first render no rects exist, and clicks outside every
    /// column must not move focus.
    #[tokio::test]
    async fn click_outside_panels_changes_nothing() {
        let mut panels = make_panel_set().await;
        let (tx, _rx) = unbounded_channel();

        // No render yet → no rects → nothing to hit.
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(10, 10), &tx),
            EventState::NotConsumed
        );
        assert_eq!(panels.focused(), PanelKind::Editor);

        lay_out(&mut panels);
        // Cells outside the laid-out area miss.
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(10, 50), &tx),
            EventState::NotConsumed
        );
        assert_eq!(panels.focused(), PanelKind::Editor);
    }

    /// Scrolling routes to the panel under the cursor without stealing focus.
    #[tokio::test]
    async fn scroll_does_not_change_focus() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (tx, _rx) = unbounded_channel();

        assert_eq!(
            panels.handle_mouse(&scroll_at(20, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.focused(), PanelKind::Editor);
    }

    /// Dragging the drawer↔editor divider resizes the drawer, clamped to the
    /// minimum widths on both sides.
    #[tokio::test]
    async fn divider_drag_resizes_drawer() {
        let mut panels = make_panel_set().await;
        lay_out(&mut panels);
        let (tx, _rx) = unbounded_channel();

        // Drawer occupies 7..41; the divider is its right border column (40).
        assert_eq!(
            panels.handle_mouse(&mouse_down_at(40, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(
            panels.handle_mouse(&drag_at(60, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.drawer_width, 54); // 60 - 7 + 1
        // Dragging far left clamps to the minimum drawer width.
        assert_eq!(
            panels.handle_mouse(&drag_at(0, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.drawer_width, MIN_DRAWER_WIDTH);
        // Dragging far right clamps so the editor keeps its minimum.
        assert_eq!(
            panels.handle_mouse(&drag_at(200, 5), &tx),
            EventState::Consumed
        );
        assert_eq!(panels.drawer_width, 120 - 7 - MIN_EDITOR_WIDTH);
        // Release ends the drag: further drags are plain panel events.
        assert_eq!(
            panels.handle_mouse(&up_at(80, 5), &tx),
            EventState::Consumed
        );
        let width_before = panels.drawer_width;
        panels.handle_mouse(&drag_at(50, 5), &tx);
        assert_eq!(panels.drawer_width, width_before);
    }

    #[test]
    fn default_focus_is_editor() {
        let order = PanelOrder::new();
        assert_eq!(order.focused(), PanelKind::Editor);
    }

    #[test]
    fn focus_cycle_wraps_over_visible_panels() {
        let mut order = PanelOrder::new();
        // Focus = editor (right end); next wraps to the rail.
        assert_eq!(order.next_kind(), Some(PanelKind::Rail));
        assert_eq!(order.prev_kind(), Some(PanelKind::Drawer));

        order.focus(PanelKind::Rail);
        assert_eq!(order.prev_kind(), Some(PanelKind::Editor)); // wrap left
        assert_eq!(order.next_kind(), Some(PanelKind::Drawer));
    }

    #[test]
    fn focus_cycle_skips_hidden_drawer() {
        let mut order = PanelOrder::new();
        order.hide(PanelKind::Drawer);
        assert_eq!(order.next_kind(), Some(PanelKind::Rail));
        order.focus(PanelKind::Rail);
        assert_eq!(order.next_kind(), Some(PanelKind::Editor));
    }

    #[test]
    fn show_hide_toggles_visibility_except_rail_and_editor() {
        let mut order = PanelOrder::new();
        assert!(order.is_visible(PanelKind::Drawer));

        order.hide(PanelKind::Drawer);
        assert!(!order.is_visible(PanelKind::Drawer));
        order.show(PanelKind::Drawer);
        assert!(order.is_visible(PanelKind::Drawer));

        // The rail and the editor cannot be hidden.
        order.hide(PanelKind::Editor);
        assert!(order.is_visible(PanelKind::Editor));
        order.hide(PanelKind::Rail);
        assert!(order.is_visible(PanelKind::Rail));
    }

    #[test]
    fn hiding_focused_panel_moves_focus_to_visible() {
        let mut order = PanelOrder::new();
        order.focus(PanelKind::Drawer);
        order.hide(PanelKind::Drawer);
        // Focus cannot stay on a hidden panel.
        assert!(order.is_visible(order.focused()));
    }

    #[test]
    fn layout_columns_splits_area_in_panel_order() {
        let area = Rect::new(0, 0, 120, 40);
        let visible = [PanelKind::Rail, PanelKind::Drawer, PanelKind::Editor];
        let columns = layout_columns(&visible, area, DEFAULT_DRAWER_WIDTH);

        assert_eq!(columns.len(), 3);
        // Rail fixed, drawer at its width, editor takes the rest.
        assert_eq!(columns[0].0, PanelKind::Rail);
        assert_eq!(columns[0].1.width, RAIL_WIDTH);
        assert_eq!(columns[1].0, PanelKind::Drawer);
        assert_eq!(columns[1].1.width, DEFAULT_DRAWER_WIDTH);
        assert_eq!(columns[2].0, PanelKind::Editor);
        assert_eq!(columns[2].1.width, 120 - RAIL_WIDTH - DEFAULT_DRAWER_WIDTH);
        // Columns tile the area left→right.
        assert_eq!(columns[0].1.x, 0);
        assert_eq!(columns[1].1.x, RAIL_WIDTH);
        assert_eq!(columns[2].1.x, RAIL_WIDTH + DEFAULT_DRAWER_WIDTH);
    }

    #[test]
    fn hidden_drawer_gives_width_to_editor() {
        let area = Rect::new(0, 0, 120, 40);
        let visible = [PanelKind::Rail, PanelKind::Editor];
        let columns = layout_columns(&visible, area, DEFAULT_DRAWER_WIDTH);

        assert_eq!(columns.len(), 2);
        assert_eq!(columns[1].0, PanelKind::Editor);
        assert_eq!(columns[1].1.width, 120 - RAIL_WIDTH);
    }

    #[test]
    fn kind_at_hit_tests_panel_columns() {
        let area = Rect::new(0, 0, 120, 40);
        let visible = [PanelKind::Rail, PanelKind::Drawer, PanelKind::Editor];
        let columns = layout_columns(&visible, area, DEFAULT_DRAWER_WIDTH);

        assert_eq!(kind_at(&columns, 0, 0), Some(PanelKind::Rail));
        assert_eq!(kind_at(&columns, 6, 10), Some(PanelKind::Rail));
        assert_eq!(kind_at(&columns, 7, 10), Some(PanelKind::Drawer));
        assert_eq!(kind_at(&columns, 40, 39), Some(PanelKind::Drawer));
        assert_eq!(kind_at(&columns, 41, 0), Some(PanelKind::Editor));
        assert_eq!(kind_at(&columns, 119, 39), Some(PanelKind::Editor));
        // Outside the laid-out area.
        assert_eq!(kind_at(&columns, 120, 10), None);
        assert_eq!(kind_at(&columns, 10, 40), None);
        // No columns yet (before the first render).
        assert_eq!(kind_at(&[], 10, 10), None);
    }

    #[test]
    fn open_drawer_view_reveals_and_switches() {
        let mut order = PanelOrder::new();
        order.hide(PanelKind::Drawer);
        assert!(!order.is_visible(PanelKind::Drawer));
        order.show(PanelKind::Drawer);
        assert!(order.is_visible(PanelKind::Drawer));
    }

    fn test_attachment_view() -> AttachmentView {
        let details = kimun_core::AttachmentDetails {
            path: kimun_core::nfs::VaultPath::new("a.png"),
            size: 0,
            modified_secs: 0,
            extension: Some("png".to_string()),
            content: kimun_core::AttachmentContent::Binary,
        };
        AttachmentView::new(
            details,
            crate::settings::icons::Icons::new(false),
            crate::keys::KeyBindings::empty(),
        )
    }

    #[tokio::test]
    async fn ask_content_hides_the_editor_and_leaving_restores_it() {
        let mut ps = make_panel_set().await;
        assert!(ps.editor().is_some());
        ps.show_ask();
        assert!(ps.editor().is_none());
        assert!(ps.is_showing_ask());
        // Leaving Ask returns the note editor; the resident thread survives.
        ps.hide_ask();
        assert!(!ps.is_showing_ask());
        assert!(ps.editor().is_some());
    }

    /// `set_ask_client` is the single injection point: it drives the resident
    /// Ask panel's client, which is its composer-enabled signal. No client ⇒
    /// disabled (never a forever-`Thinking` turn); a present client ⇒ enabled.
    #[tokio::test]
    async fn set_ask_client_drives_the_resident_panels_client() {
        let mut ps = make_panel_set().await;
        ps.set_ask_client(None);
        assert!(!ps.ask().has_client());
        // Handing a client back enables it. (A bare client over a throwaway
        // vault id is fine — it's never called here.)
        let client = std::sync::Arc::new(crate::server_client::RagClient::new(
            "http://localhost:0".to_string(),
            None,
            "vault".to_string(),
        ));
        ps.set_ask_client(Some(client));
        assert!(ps.ask().has_client());
    }

    #[tokio::test]
    async fn showing_an_attachment_replaces_ask() {
        let mut ps = make_panel_set().await;
        ps.show_ask();
        ps.show_attachment(test_attachment_view());
        assert!(!ps.is_showing_ask());
        assert!(ps.is_showing_attachment());
    }

    #[test]
    fn visible_in_order_skips_hidden() {
        let mut order = PanelOrder::new();
        assert_eq!(
            order.visible_in_order(),
            vec![PanelKind::Rail, PanelKind::Drawer, PanelKind::Editor]
        );
        order.hide(PanelKind::Drawer);
        assert_eq!(
            order.visible_in_order(),
            vec![PanelKind::Rail, PanelKind::Editor]
        );
    }
}