kui_core/

menu.rs

//! Menus as data: the rows of a context menu or the application menu bar,
//! what the window has open, and what a host still has to do after a row
//! is chosen.
//!
//! An app meets this module through `Ui::open_menu` / `Core::open_menu`
//! (a [`Menu`] over a node, usually from a `contextmenu` event), through
//! `Core::declare_menu_bar` (a [`MenuBar`] of [`BarMenu`]s), and through
//! the `menu` event a chosen row posts on the node the menu was about. A
//! host that holds the core drains [`MenuAction`]s with
//! `Core::take_menu_actions`: the clipboard work the core cannot do itself.
//! Nothing here draws; the stock renderer builds ordinary nodes into the
//! frame, and a platform that owns menus (the macOS menu bar) gets the
//! same list.
//!
//! ```rust
//! use kui_core::{
//!     Accel, BarMenu, Core, Key, Menu, MenuAction, MenuBar, MenuItem, MenuRole, Vec2,
//! };
//!
//! let bar = MenuBar::new(vec![
//!     BarMenu::new("File", vec![
//!         MenuItem::new("Open...").id("open").accel("mod+o"),
//!         MenuItem::separator(),
//!         MenuItem::new("Quit").id("quit"),
//!     ]),
//!     BarMenu::new("Edit", vec![
//!         MenuItem::role(MenuRole::Cut),
//!         MenuItem::role(MenuRole::Copy),
//!         MenuItem::role(MenuRole::Paste),
//!     ]),
//! ]);
//! let mut core = Core::new();
//! core.declare_menu_bar(bar);
//! assert_eq!(core.menu_bar().map(|b| b.menus.len()), Some(2));
//!
//! // A context menu over a node, at the point the press landed.
//! let items = vec![
//!     MenuItem::new("Inspect").id("inspect"),
//!     MenuItem::new("Delete").id("delete").enabled(false),
//! ];
//! core.open_menu(Menu::new(Key::ROOT, Vec2::new(40.0, 30.0), items));
//!
//! // After a row is chosen, the host finishes what the core cannot.
//! for action in core.take_menu_actions() {
//!     match action {
//!         MenuAction::SetClipboard { text, .. } => println!("copy {text}"),
//!         MenuAction::Paste => println!("read the clipboard"),
//!         other => println!("{other:?}"),
//!     }
//! }
//!
//! // Accelerators are display text; `Accel` parses them for a native bar.
//! let accel = Accel::parse("mod+shift+s").unwrap();
//! assert!(accel.mods.shift);
//! ```

use crate::geom::Vec2;
use crate::key::Key;
use crate::tree::OriginId;
use crate::value::Value;

/// What an item *means*, as far as anything outside the app is concerned.
///
/// The roles exist for two reasons and neither is decoration. A host with
/// a native menu maps them onto its own standard items, so Copy is the
/// platform's Copy — its wording, its accelerator, its position; and the
/// core acts on the ones it can act on without asking anybody
/// ([`MenuRole::SelectAll`]) or with one round trip through the host (the
/// clipboard three). [`MenuRole::Custom`] is an item the app invented,
/// which only the app can perform.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum MenuRole {
    /// The app's own item: choosing it posts the item's payload and the
    /// core does nothing else.
    #[default]
    Custom,
    /// A divider. Never focusable, never chosen, no payload.
    Separator,
    Cut,
    Copy,
    Paste,
    SelectAll,
    /// Show the platform's definition/Look Up panel for the selection.
    /// The core cannot draw one: with no host to answer it, the item is
    /// not offered.
    LookUp,
}

impl MenuRole {
    /// Every role, in wire order: the index a binding that spells roles as
    /// numbers sends (C's `KUI_MENU_*`), pinned there by name. Append-only,
    /// like every list a C enum restates.
    pub const ALL: [MenuRole; 7] = [
        MenuRole::Custom,
        MenuRole::Separator,
        MenuRole::Cut,
        MenuRole::Copy,
        MenuRole::Paste,
        MenuRole::SelectAll,
        MenuRole::LookUp,
    ];

    /// The role a wire name spells, for the bindings that take roles as
    /// strings: the inverse of [`Self::name`], so a binding cannot accept
    /// a spelling the event will not report back. `None` for a name that
    /// is no role.
    pub fn from_name(name: &str) -> Option<MenuRole> {
        Self::ALL.into_iter().find(|r| r.name() == name)
    }

    /// The wire name, for the bindings and the report.
    pub fn name(self) -> &'static str {
        match self {
            MenuRole::Custom => "custom",
            MenuRole::Separator => "separator",
            MenuRole::Cut => "cut",
            MenuRole::Copy => "copy",
            MenuRole::Paste => "paste",
            MenuRole::SelectAll => "selectAll",
            MenuRole::LookUp => "lookUp",
        }
    }

    /// The label the stock renderer draws when the item declares none.
    /// A native renderer ignores this and uses the platform's wording,
    /// which is the point of having a role at all.
    pub fn default_label(self) -> &'static str {
        match self {
            MenuRole::Custom | MenuRole::Separator => "",
            MenuRole::Cut => "Cut",
            MenuRole::Copy => "Copy",
            MenuRole::Paste => "Paste",
            MenuRole::SelectAll => "Select All",
            MenuRole::LookUp => "Look Up",
        }
    }

    /// The shortcut the stock renderer draws beside the row when the item
    /// declares none, spelled the way the platform spells it — Command on
    /// macOS, Control elsewhere, the same split [`KeyMods::primary`] makes
    /// for the key that produces it.
    ///
    /// Display only, like every accelerator here: the core binds nothing,
    /// and the row only names the key the host is already handling. Empty
    /// for the roles with no standard shortcut — `Custom` above all, since
    /// an app's own accelerator is the app's to declare
    /// ([`MenuItem::accel`]) — and empty for `LookUp`, whose shortcut
    /// belongs to the one platform that has the panel and draws its own
    /// menu anyway.
    ///
    /// [`KeyMods::primary`]: crate::input::KeyMods::primary
    pub fn default_accel(self) -> &'static str {
        let mac = cfg!(target_os = "macos");
        match self {
            MenuRole::Cut if mac => "⌘X",
            MenuRole::Copy if mac => "⌘C",
            MenuRole::Paste if mac => "⌘V",
            MenuRole::SelectAll if mac => "⌘A",
            MenuRole::Cut => "Ctrl+X",
            MenuRole::Copy => "Ctrl+C",
            MenuRole::Paste => "Ctrl+V",
            MenuRole::SelectAll => "Ctrl+A",
            MenuRole::Custom | MenuRole::Separator | MenuRole::LookUp => "",
        }
    }

    /// Whether the core performs this itself, or with one hand from the
    /// host. `false` is an item only the app can carry out.
    pub fn is_builtin(self) -> bool {
        !matches!(self, MenuRole::Custom | MenuRole::Separator)
    }
}

/// One row of a menu.
#[derive(Clone, Debug, PartialEq)]
pub struct MenuItem {
    /// What the row reads. Empty takes the role's default wording.
    pub label: String,
    pub role: MenuRole,
    /// A disabled row is drawn dimmed, is not focusable, and cannot be
    /// chosen — Paste with an empty clipboard, Copy with no selection.
    /// Present rather than absent on purpose: a menu whose rows move
    /// depending on what is possible is a menu nobody builds muscle
    /// memory for.
    pub enabled: bool,
    /// Posted as the event payload when the row is chosen. A `Custom`
    /// item without one posts its label.
    pub id: Option<Value>,
    /// Drawn with a checkmark, and the platform's own check state where a
    /// host renders the menu itself. A setting the row *is* rather than a
    /// command it runs — View ▸ Show Sidebar — and inert for every other
    /// row, which is why it is a flag beside the label and not a role.
    pub checked: bool,
    /// Drawn right-aligned and dimmed; the core binds nothing to it. The
    /// keyboard shortcut is the app's or the platform's, and an
    /// accelerator here only says which one it is. A standard row that
    /// declares none takes its role's ([`MenuRole::default_accel`]), the
    /// way an empty label takes the role's wording.
    pub accel: Option<String>,
    /// The rows of the menu this row opens: empty for an ordinary row. A
    /// row with a submenu is drawn with a chevron and is never chosen
    /// itself — hovering it, clicking it, Enter or the Right arrow opens
    /// its menu beside it, and Left or Escape closes it again — and what
    /// a chosen row inside posts is that row's own `menu` event, on the
    /// node the outermost menu is about (backlog F128). Nests to any
    /// depth. `MenuItem::submenu(label, items)` builds one.
    pub submenu: Vec<MenuItem>,
}

impl MenuItem {
    /// A row from plain data: a map with `label`, `role` (a wire name;
    /// absent is `custom`), `enabled` (default true), `checked` (default
    /// false), `id`, `accel` and `items` (a submenu's rows, the same maps).
    /// A custom row needs a label, since the label is what it posts when it
    /// has no `id`. Every binding funnels its rows through here —
    /// `openMenu`'s list and a menu bar's alike — so a row can never mean
    /// two things.
    pub fn from_value(v: &Value) -> Result<Self, String> {
        let Value::Map(_) = v else {
            return Err("each menu item is an object".into());
        };
        let role = match v.get_str("role") {
            None => MenuRole::Custom,
            Some(name) => MenuRole::from_name(name)
                .ok_or_else(|| format!("unknown menu item role {name:?}"))?,
        };
        let label = v.get_str("label").unwrap_or_default().to_string();
        if label.is_empty() && role == MenuRole::Custom {
            return Err("a custom menu item needs a label".into());
        }
        Ok(MenuItem {
            label,
            role,
            enabled: v.get_bool("enabled").unwrap_or(true),
            checked: v.get_bool("checked").unwrap_or(false),
            id: v.get("id").filter(|id| **id != Value::Null).cloned(),
            accel: v.get_str("accel").map(str::to_string),
            submenu: match v.get("items") {
                None | Some(Value::Null) => Vec::new(),
                Some(items) => Self::list_from_value(items)?,
            },
        })
    }

    /// A menu's rows from plain data: a list of [`Self::from_value`] maps.
    pub fn list_from_value(v: &Value) -> Result<Vec<Self>, String> {
        let Value::List(rows) = v else {
            return Err("a menu's items are an array".into());
        };
        rows.iter().map(Self::from_value).collect()
    }

    /// The keys a row map may carry — everything [`Self::from_value`]
    /// reads. A binding that drops the rest of a map on the floor checks
    /// against this first and raises [`crate::diag::unknown_menu_item_key`]
    /// for what it dropped, so `{label, disabled: true}` is not silently a
    /// row that is enabled.
    pub const KEYS: [&'static str; 7] = [
        "label", "role", "enabled", "checked", "id", "accel", "items",
    ];

    /// The name a binding reports a row's dropped keys under
    /// (`diag::unknown_prop` routes it to `diag::unknown_menu_item_key`):
    /// a row is not an element, so it is not in `schema::ELEMENTS`, and
    /// the spelling is the type's in JSX (`MenuItemInput`).
    pub const NAME: &'static str = "menuItem";

    /// A select's options from plain data (`widgets::select_items` in the
    /// bindings): a list whose entries are strings — an option by its
    /// label, posting it — or [`Self::from_value`] maps, for an option
    /// that posts an `id` of its own or is disabled. An empty list is
    /// refused: a select with nothing to choose from is a field that opens
    /// a menu of no rows, which only Escape leaves.
    pub fn options_from_value(v: &Value) -> Result<Vec<Self>, String> {
        let Value::List(rows) = v else {
            return Err("a select's options are an array".into());
        };
        if rows.is_empty() {
            return Err("a select needs at least one option".into());
        }
        rows.iter()
            .map(|row| match row {
                Value::Str(label) if !label.is_empty() => Ok(Self::new(label.as_str())),
                Value::Str(_) => Err("an option needs a label".into()),
                other => Self::from_value(other),
            })
            .collect()
    }

    /// An item of the app's own, by label.
    pub fn new(label: impl Into<String>) -> Self {
        Self {
            label: label.into(),
            role: MenuRole::Custom,
            enabled: true,
            checked: false,
            id: None,
            accel: None,
            submenu: Vec::new(),
        }
    }

    /// One of the standard items, with the role's own wording.
    pub fn role(role: MenuRole) -> Self {
        Self {
            label: String::new(),
            role,
            enabled: true,
            checked: false,
            id: None,
            accel: None,
            submenu: Vec::new(),
        }
    }

    /// A row that opens a menu of `items` beside it: "Move to ▸", "Sort
    /// by ▸". It is chosen through, never itself — see the `submenu`
    /// field — so it needs no `id`, and an `accel` on it is not drawn (the
    /// chevron is where it would go). A submenu with no rows is an ordinary
    /// row ([`Self::has_submenu`]).
    ///
    /// ```rust
    /// use kui_core::MenuItem;
    ///
    /// let sort = MenuItem::submenu("Sort by", vec![
    ///     MenuItem::new("Name").id("sort.name").checked(true),
    ///     MenuItem::new("Date modified").id("sort.date"),
    /// ]);
    /// assert!(sort.has_submenu());
    /// ```
    pub fn submenu(label: impl Into<String>, items: Vec<MenuItem>) -> Self {
        Self {
            submenu: items,
            ..Self::new(label)
        }
    }

    /// Whether the row opens a menu rather than being chosen (the
    /// `submenu` field). A row declared with an empty submenu is an
    /// ordinary row.
    pub fn has_submenu(&self) -> bool {
        !self.submenu.is_empty()
    }

    /// The row at `path` in `items`: `[2]` is the third row, `[2, 0]` the
    /// first row of the third row's submenu. `None` past the end of any
    /// level, for an empty path, and through a row with no submenu.
    pub fn at_path<'a>(items: &'a [MenuItem], path: &[usize]) -> Option<&'a MenuItem> {
        let (&last, outer) = path.split_last()?;
        let mut level = items;
        for &i in outer {
            level = &level.get(i)?.submenu;
        }
        level.get(last)
    }

    pub fn separator() -> Self {
        Self::role(MenuRole::Separator)
    }

    pub fn enabled(mut self, on: bool) -> Self {
        self.enabled = on;
        self
    }

    /// Draws a checkmark beside the row (and sets the platform's check
    /// state where a host renders the menu).
    pub fn checked(mut self, on: bool) -> Self {
        self.checked = on;
        self
    }

    pub fn id(mut self, id: impl Into<Value>) -> Self {
        self.id = Some(id.into());
        self
    }

    pub fn accel(mut self, a: impl Into<String>) -> Self {
        self.accel = Some(a.into());
        self
    }

    /// What the row reads: its own label, or the role's.
    pub fn text(&self) -> &str {
        if self.label.is_empty() {
            self.role.default_label()
        } else {
            &self.label
        }
    }

    /// The accelerator the row declares: its own, or the role's. `None` is
    /// a row with neither, which is every `Custom` one the app did not
    /// spell a shortcut for. As declared — [`Self::accel_label`] is what is
    /// drawn.
    pub fn accel_text(&self) -> Option<&str> {
        match &self.accel {
            Some(accel) => Some(accel),
            None => Some(self.role.default_accel()).filter(|a| !a.is_empty()),
        }
    }

    /// What the row draws on its right: [`Self::accel_text`] in the
    /// platform's spelling when kui can parse it (`"mod+shift+n"` reads
    /// `⇧⌘N` on a Mac and `Ctrl+Shift+N` elsewhere), and exactly as
    /// written when it cannot (`"gd"`, an app's own hint). See
    /// [`Accel::label`].
    pub fn accel_label(&self) -> Option<std::borrow::Cow<'_, str>> {
        self.accel_text().map(Accel::label)
    }

    /// Whether the row takes focus and can be chosen — or, for a row with
    /// a submenu, opened.
    pub fn selectable(&self) -> bool {
        self.enabled && self.role != MenuRole::Separator
    }

    /// Whether the row at `path` can be chosen the way the drawn menu
    /// reaches it: every row on the way enabled, the last one selectable
    /// and opening nothing. A host's report of a row the menu could not
    /// have shown it is refused rather than performed.
    pub(crate) fn choosable_at(items: &[MenuItem], path: &[usize]) -> bool {
        let mut level = items;
        for (n, &i) in path.iter().enumerate() {
            let Some(item) = level.get(i).filter(|item| item.selectable()) else {
                return false;
            };
            if n + 1 == path.len() {
                return !item.has_submenu();
            }
            level = &item.submenu;
        }
        false
    }

    /// Rewrites every accelerator in `items` that kui can parse into the
    /// platform's own spelling ([`Accel::label`]) and leaves the rest
    /// exactly as declared. What `declare_menu_bar` and `open_menu` do on
    /// the way in, so the menu a host reads back (`Core::menu`,
    /// `Core::menu_bar`) is the one the drawn menu shows, and a platform
    /// menu parses the same string into the same key.
    pub(crate) fn normalize_accels(items: &mut [MenuItem]) {
        for item in items {
            if let Some(accel) = &item.accel
                && let std::borrow::Cow::Owned(display) = Accel::label(accel)
            {
                item.accel = Some(display);
            }
            Self::normalize_accels(&mut item.submenu);
        }
    }
}

/// The menu a window has open: its items, where it opened, and what it is
/// about. One per window — opening a second closes the first, the way one
/// selection closes the last.
#[derive(Clone, Debug, PartialEq)]
pub struct Menu {
    /// The node the menu was opened over. Chosen items post their event
    /// on it, so an app reads a menu the way it reads a click.
    pub target: Key,
    /// Where it opens, logical viewport px — the press point, which is
    /// where every platform puts a context menu.
    pub at: Vec2,
    /// Who asked for it: the host, or the extension whose node it is
    /// about. Carried onto the events the items post.
    pub origin: OriginId,
    pub items: Vec<MenuItem>,
}

impl Menu {
    pub fn new(target: Key, at: Vec2, items: Vec<MenuItem>) -> Self {
        Self {
            target,
            at,
            origin: OriginId::HOST,
            items,
        }
    }

    pub fn origin(mut self, origin: OriginId) -> Self {
        self.origin = origin;
        self
    }
}

/// What choosing an item leaves for the host to do, drained with
/// [`crate::runtime::Core::take_menu_actions`] the way window and audio
/// commands are.
///
/// The clipboard is the host's in this library — the runner already reads
/// and writes it for Cmd-C/X/V — and nothing here changes that. The core
/// works out *what* to copy, which is the half it is uniquely able to do,
/// and hands over a string.
#[derive(Clone, Debug, PartialEq)]
pub enum MenuAction {
    /// Put this on the system clipboard. Both Copy and Cut produce one;
    /// Cut has already removed the text by the time it arrives.
    ///
    /// `html` is the same selection with the formatting the core knows
    /// about (bold, italic, a span's declared colour), for a host that can
    /// offer a second flavour. It is an addition to `text`, never a
    /// replacement: a clipboard whose only flavour is HTML pastes markup
    /// into every plain-text field on the machine.
    SetClipboard { text: String, html: Option<String> },
    /// Put this secret on the system clipboard the way a password manager
    /// does: the text, marked concealed and transient —
    /// `org.nspasteboard.ConcealedType` and `TransientType` on macOS,
    /// excluded from monitoring, history and the cloud clipboard on
    /// Windows, `x-kde-passwordManagerHint: secret` on Linux — so a
    /// clipboard manager neither shows nor keeps it. Queued by
    /// `Core::set_clipboard_secret`, never by a menu row. Plain text only:
    /// a secret has no formatting to offer.
    SetClipboardSecret { text: String },
    /// Read the clipboard and deliver it as `InputEvent::Paste`: a
    /// focused editor takes it as typing, the way it takes Cmd-V, and a
    /// focused key sink hears it as `{kind:"text"}` — which is how an
    /// app that owns its text gets a paste it asked for with
    /// `Core::request_paste`. The core cannot read a clipboard, so Paste
    /// is the one standard item it can only ask for. The answer carries
    /// the pasteboard's markers ([`crate::input::ClipboardMarks`]), and an
    /// answer that is a bare `InputEvent::Commit` is one that marked
    /// nothing.
    Paste,
    /// Show the platform's definition panel for `text`, anchored at
    /// `rect` (logical viewport px — the word's own box, which is what
    /// macOS's `showDefinitionForAttributedString:atPoint:` wants). Both
    /// the Look Up row and a force click over text produce one; a host
    /// that cannot show a panel drops it, and is never offered the row in
    /// the first place (`Core::set_lookup_available`).
    LookUp {
        text: String,
        /// The **baseline origin of the selection's first line**, logical
        /// viewport px — the point
        /// `showDefinitionForAttributedString:atPoint:` takes and draws
        /// the term back over. Not a box's corner: a box's bottom puts the
        /// term a line low, and a multi-run selection's union puts it
        /// under the last line while the panel shows the first.
        at: crate::geom::Vec2,
    },
}

// -- The application menu bar -----------------------------------------------
// The bar is the same rows one level up: a list of menus, each a label and
// the `MenuItem`s above, so an Edit menu's Copy is the *same item* the
// context menu's Copy is and the core performs it the same way.

/// One menu of the bar: what the bar reads, and what drops out of it.
#[derive(Clone, Debug, Default, PartialEq)]
pub struct BarMenu {
    /// What the bar shows. On macOS the first menu is the application menu
    /// and the platform titles that one with the app's own name, whatever
    /// this says.
    pub label: String,
    pub items: Vec<MenuItem>,
    /// A disabled menu is dimmed and opens nothing.
    pub enabled: bool,
}

impl BarMenu {
    pub fn new(label: impl Into<String>, items: Vec<MenuItem>) -> Self {
        Self {
            label: label.into(),
            items,
            enabled: true,
        }
    }

    pub fn enabled(mut self, on: bool) -> Self {
        self.enabled = on;
        self
    }
}

/// The application menu: what a frame declares, in order
/// (`Core::declare_menu_bar`).
///
/// Declared and not commanded, like the window title: a frame that declares
/// none leaves the last one in force, and a frame that declares an empty
/// bar takes it away. Where the platform owns a menu bar the driver hands
/// this over (macOS: `NSApp.mainMenu`); everywhere else
/// [`crate::widgets::menu_bar`] draws it, and each of its titles opens the
/// ordinary [`Menu`] machinery — so the dropdown, its keyboard, its
/// dismissal and its access tree are the ones already built for the context
/// menu.
#[derive(Clone, Debug, Default, PartialEq)]
pub struct MenuBar {
    pub menus: Vec<BarMenu>,
}

impl MenuBar {
    pub fn new(menus: Vec<BarMenu>) -> Self {
        Self { menus }
    }

    /// A bar from plain data: a list of `{ label, items, enabled? }`,
    /// whose `items` are the rows `openMenu` takes. A menu with no `items`
    /// is a shape error and not an empty menu: the two read the same on
    /// screen and only one of them was meant.
    pub fn from_value(v: &Value) -> Result<Self, String> {
        let Value::List(menus) = v else {
            return Err("menu is an array of menus".into());
        };
        let mut out = Vec::with_capacity(menus.len());
        for entry in menus {
            let Value::Map(_) = entry else {
                return Err("each menu is an object { label, items }".into());
            };
            let label = entry
                .get_str("label")
                .ok_or("each menu needs a label")?
                .to_string();
            let items = entry
                .get("items")
                .ok_or_else(|| format!("menu entry `{label}` needs `items` (a list of rows)"))?;
            out.push(BarMenu {
                label,
                items: MenuItem::list_from_value(items)?,
                enabled: entry.get_bool("enabled").unwrap_or(true),
            });
        }
        Ok(Self::new(out))
    }

    /// Nothing declared: the bar the platform is asked to take away.
    pub fn is_empty(&self) -> bool {
        self.menus.is_empty()
    }

    /// The item at `(menu, item)`, if it is there.
    pub fn item(&self, menu: usize, item: usize) -> Option<&MenuItem> {
        self.menus.get(menu)?.items.get(item)
    }

    /// The item at `path` inside menu `menu`, through its submenus
    /// ([`MenuItem::at_path`]).
    pub fn item_at(&self, menu: usize, path: &[usize]) -> Option<&MenuItem> {
        MenuItem::at_path(&self.menus.get(menu)?.items, path)
    }
}

/// A keyboard shortcut, parsed out of the string an item declares.
///
/// The core binds nothing to it and never has ([`MenuItem::accel`] is
/// display); this exists for the one consumer that needs the parts rather
/// than the words — a platform menu bar, which sets a real key equivalent
/// and then matches it before the window ever sees the key.
///
/// Both spellings parse, because both are written in the field: the
/// portable one (`"mod+shift+s"`, where `mod` is Command on macOS and
/// Control elsewhere) and the platform one a menu is read in (`"⇧⌘S"`,
/// `"Ctrl+Shift+S"`). [`Accel::display`] is the second, which is what
/// `declare_menu_bar` normalizes a declaration into so the drawn bar and
/// the platform's read the same.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Accel {
    pub code: crate::input::KeyCode,
    pub mods: crate::input::KeyMods,
}

impl Accel {
    /// Parses `"mod+s"`, `"ctrl+shift+p"`, `"f5"`, `"⇧⌘S"`. `None` for
    /// anything this vocabulary cannot name — the caller then leaves the
    /// string alone and draws it as written, since a shortcut kui cannot
    /// parse is still a shortcut the app's own keymap runs.
    pub fn parse(s: &str) -> Option<Accel> {
        use crate::input::{KeyCode, KeyMods};
        let mut mods = KeyMods::default();
        let mut rest = s.trim();
        // The glyph spelling has no separators: ⌃⌥⇧⌘ in that order, then
        // the key. Stripped first so `"⌘S"` and `"cmd+s"` land together.
        loop {
            let mut chars = rest.chars();
            match chars.next() {
                Some('\u{2303}') => mods.ctrl = true,
                Some('\u{2325}') => mods.alt = true,
                Some('\u{21e7}') => mods.shift = true,
                Some('\u{2318}') => mods.super_key = true,
                _ => break,
            }
            rest = chars.as_str();
        }
        let mut code = None;
        for part in rest.split('+') {
            let part = part.trim();
            if part.is_empty() {
                return None;
            }
            let lower = part.to_ascii_lowercase();
            match lower.as_str() {
                // The one token that is not a key on any keyboard:
                // whichever modifier this platform puts shortcuts behind.
                "mod" | "cmdorctrl" => {
                    if cfg!(target_os = "macos") {
                        mods.super_key = true;
                    } else {
                        mods.ctrl = true;
                    }
                }
                "cmd" | "command" | "super" | "meta" | "win" => mods.super_key = true,
                "ctrl" | "control" => mods.ctrl = true,
                "alt" | "option" | "opt" => mods.alt = true,
                "shift" => mods.shift = true,
                // The key, and only one of them: `"s+s"` is a typo.
                _ if code.is_some() => return None,
                // A key as `display` writes it reads back as that key, so
                // the menu that normalized `"mod+backspace"` into `⌘⌫`
                // binds Backspace and not a `⌫` no keyboard types.
                _ => {
                    code = Some(if part.chars().count() == 1 {
                        key_from_label(part).unwrap_or(KeyCode::Char(part.chars().next().unwrap()))
                    } else {
                        KeyCode::from_name(&lower).or_else(|| key_from_label(part))?
                    });
                }
            }
        }
        let code = code?;
        // A lock key turns a state rather than being a key a shortcut is
        // held against: no menu bar takes `ctrl+capslock`.
        let lock = matches!(
            code,
            KeyCode::CapsLock | KeyCode::NumLock | KeyCode::ScrollLock
        );
        (code != KeyCode::Unknown && !lock).then_some(Accel { code, mods })
    }

    /// How the platform writes it: the macOS glyph run (`⇧⌘S`, in AppKit's
    /// order, no separators) or the spelled form (`Ctrl+Shift+S`).
    pub fn display(&self) -> String {
        let key = key_label(self.code);
        if cfg!(target_os = "macos") {
            let mut out = String::new();
            for (on, glyph) in [
                (self.mods.ctrl, '\u{2303}'),
                (self.mods.alt, '\u{2325}'),
                (self.mods.shift, '\u{21e7}'),
                (self.mods.super_key, '\u{2318}'),
            ] {
                if on {
                    out.push(glyph);
                }
            }
            out.push_str(&key);
            out
        } else {
            let mut parts = Vec::new();
            for (on, name) in [
                (self.mods.ctrl, "Ctrl"),
                (self.mods.super_key, "Super"),
                (self.mods.alt, "Alt"),
                (self.mods.shift, "Shift"),
            ] {
                if on {
                    parts.push(name);
                }
            }
            parts.push(&key);
            parts.join("+")
        }
    }

    /// What a menu draws for the accelerator `spelled`: its
    /// [`Accel::display`] when it parses, and `spelled` itself when it
    /// does not — a shortcut kui cannot name is still one the app's own
    /// keymap runs, and its spelling is the app's (ADR 0018, decision 7).
    /// The drawn menu, the drawn bar and `open_menu` all read an
    /// accelerator through this, so a portable `"mod+shift+n"` never
    /// reaches the screen as written (backlog F127).
    pub fn label(spelled: &str) -> std::borrow::Cow<'_, str> {
        match Accel::parse(spelled) {
            Some(a) => std::borrow::Cow::Owned(a.display()),
            None => std::borrow::Cow::Borrowed(spelled),
        }
    }

    /// The portable spelling, the one [`Accel::parse`] reads back to the
    /// same chord on every platform: the modifiers held as `ctrl`,
    /// `super`, `alt`, `shift` in that order, then the key by its wire
    /// name (`"ctrl+shift+i"`, `"super+alt+f12"`). What a binding hands
    /// out when it reads a chord back; [`Accel::display`] is what a
    /// person reads.
    pub fn spelling(&self) -> String {
        let mut parts = Vec::new();
        for (on, name) in [
            (self.mods.ctrl, "ctrl"),
            (self.mods.super_key, "super"),
            (self.mods.alt, "alt"),
            (self.mods.shift, "shift"),
        ] {
            if on {
                parts.push(name.to_string());
            }
        }
        parts.push(match self.code {
            crate::input::KeyCode::Char(c) => c.to_ascii_lowercase().to_string(),
            code => code.name(),
        });
        parts.join("+")
    }

    /// The key equivalent an `NSMenuItem` takes: the character, lowercased
    /// (AppKit reads an uppercase one as Shift being held), or `None` for a
    /// key AppKit spells with a function-key code this does not carry.
    pub fn key_equivalent(&self) -> Option<String> {
        match self.code {
            crate::input::KeyCode::Char(c) => Some(c.to_lowercase().to_string()),
            crate::input::KeyCode::Space => Some(" ".into()),
            crate::input::KeyCode::Enter => Some("\r".into()),
            crate::input::KeyCode::Tab => Some("\t".into()),
            crate::input::KeyCode::Backspace => Some("\u{8}".into()),
            crate::input::KeyCode::Delete => Some("\u{7f}".into()),
            crate::input::KeyCode::Escape => Some("\u{1b}".into()),
            _ => None,
        }
    }
}

/// What a menu writes a key as: the macOS glyph a user reads a shortcut by
/// (`⇧`, `⌫`, `↩`), and the spelled word everywhere else. A key name is
/// wire vocabulary (`"pageup"`); this is the label beside a row.
fn key_label(code: crate::input::KeyCode) -> String {
    key_label_on(code, cfg!(target_os = "macos"))
}

/// The key [`key_label`] writes as `label`, on either platform's spelling:
/// what [`Accel::parse`] reads a displayed accelerator back through.
fn key_from_label(label: &str) -> Option<crate::input::KeyCode> {
    crate::input::KeyCode::named()
        .iter()
        .map(|(k, _)| *k)
        .find(|&k| {
            key_label_on(k, true) == label || key_label_on(k, false).eq_ignore_ascii_case(label)
        })
}

fn key_label_on(code: crate::input::KeyCode, mac: bool) -> String {
    use crate::input::KeyCode;
    match code {
        KeyCode::Char(c) => return c.to_uppercase().to_string(),
        KeyCode::F(n) => return format!("F{n}"),
        _ => {}
    }
    let s = match (code, mac) {
        (KeyCode::Left, true) => "\u{2190}",
        (KeyCode::Right, true) => "\u{2192}",
        (KeyCode::Up, true) => "\u{2191}",
        (KeyCode::Down, true) => "\u{2193}",
        (KeyCode::Home, true) => "\u{2196}",
        (KeyCode::End, true) => "\u{2198}",
        (KeyCode::PageUp, true) => "\u{21de}",
        (KeyCode::PageDown, true) => "\u{21df}",
        (KeyCode::Backspace, true) => "\u{232b}",
        (KeyCode::Delete, true) => "\u{2326}",
        (KeyCode::Enter, true) => "\u{21a9}",
        (KeyCode::Tab, true) => "\u{21e5}",
        (KeyCode::Escape, true) => "\u{238b}",
        (KeyCode::Space, true) => "\u{2423}",
        (KeyCode::Left, _) => "Left",
        (KeyCode::Right, _) => "Right",
        (KeyCode::Up, _) => "Up",
        (KeyCode::Down, _) => "Down",
        (KeyCode::Home, _) => "Home",
        (KeyCode::End, _) => "End",
        (KeyCode::PageUp, _) => "Page Up",
        (KeyCode::PageDown, _) => "Page Down",
        (KeyCode::Backspace, _) => "Backspace",
        (KeyCode::Delete, _) => "Delete",
        (KeyCode::Enter, _) => "Enter",
        (KeyCode::Tab, _) => "Tab",
        (KeyCode::Escape, _) => "Esc",
        (KeyCode::Space, _) => "Space",
        (KeyCode::Insert, _) => "Insert",
        (KeyCode::Clear, true) => "\u{2327}",
        (KeyCode::Shift, true) => "\u{21e7}",
        (KeyCode::Ctrl, true) => "\u{2303}",
        (KeyCode::Alt, true) => "\u{2325}",
        (KeyCode::Super, true) => "\u{2318}",
        (KeyCode::CapsLock, true) => "\u{21ea}",
        (KeyCode::PrintScreen, _) => "Print Screen",
        (KeyCode::Pause, _) => "Pause",
        (KeyCode::Menu, _) => "Menu",
        (KeyCode::Clear, _) => "Clear",
        (KeyCode::Shift, _) => "Shift",
        (KeyCode::Ctrl, _) => "Ctrl",
        (KeyCode::Alt, _) => "Alt",
        (KeyCode::Super, _) => "Super",
        (KeyCode::CapsLock, _) => "Caps Lock",
        (KeyCode::NumLock, _) => "Num Lock",
        (KeyCode::ScrollLock, _) => "Scroll Lock",
        (KeyCode::MediaPlay, _) => "Play",
        (KeyCode::MediaPause, _) => "Pause",
        (KeyCode::MediaPlayPause, _) => "Play/Pause",
        (KeyCode::MediaStop, _) => "Stop",
        (KeyCode::MediaNext, _) => "Next Track",
        (KeyCode::MediaPrev, _) => "Previous Track",
        (KeyCode::MediaRecord, _) => "Record",
        (KeyCode::MediaFastForward, _) => "Fast Forward",
        (KeyCode::MediaRewind, _) => "Rewind",
        (KeyCode::VolumeUp, _) => "Volume Up",
        (KeyCode::VolumeDown, _) => "Volume Down",
        (KeyCode::VolumeMute, _) => "Mute",
        // Neither reachable from a parsed accelerator nor worth a lie.
        (KeyCode::Unknown, _) | (KeyCode::Char(_), _) | (KeyCode::F(_), _) => "",
    };
    s.to_string()
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::input::{KeyCode, KeyMods};

    /// `ALL` is what C indexes, what Node's generated `MenuItemRole` is
    /// spelled from and what `from_name` searches, so a variant it lacks
    /// is one no binding can say. The match is exhaustive on purpose: a
    /// variant added to the enum fails to compile here until it is placed
    /// in `ALL` too.
    #[test]
    fn all_names_every_role_once() {
        let mut seen = 0;
        for role in MenuRole::ALL {
            match role {
                MenuRole::Custom
                | MenuRole::Separator
                | MenuRole::Cut
                | MenuRole::Copy
                | MenuRole::Paste
                | MenuRole::SelectAll
                | MenuRole::LookUp => seen += 1,
            }
            assert_eq!(MenuRole::from_name(role.name()), Some(role));
            assert_eq!(
                MenuRole::ALL.iter().filter(|r| **r == role).count(),
                1,
                "{role:?} is listed more than once"
            );
        }
        assert_eq!(seen, MenuRole::ALL.len());
    }

    #[test]
    fn mod_is_the_platform_primary() {
        let a = Accel::parse("mod+s").unwrap();
        assert_eq!(a.mods.super_key, cfg!(target_os = "macos"));
        assert_eq!(a.mods.ctrl, !cfg!(target_os = "macos"));
        assert_eq!(a.code, KeyCode::Char('s'));
    }

    #[test]
    fn the_glyph_spelling_parses_back() {
        let a = Accel::parse("\u{21e7}\u{2318}S").unwrap();
        assert_eq!(
            a,
            Accel {
                code: KeyCode::Char('S'),
                mods: KeyMods::NONE.with_shift().with_super(),
            }
        );
    }

    #[test]
    fn a_named_key_parses_and_reads_back_capitalised() {
        let a = Accel::parse("ctrl+pageup").unwrap();
        assert_eq!(a.code, KeyCode::PageUp);
        let expect = if cfg!(target_os = "macos") {
            "\u{21de}"
        } else {
            "Page Up"
        };
        assert!(a.display().ends_with(expect), "{}", a.display());
    }

    /// `spelling` is the readback a binding hands out, so it must parse
    /// to the chord it came from on every platform — including the one
    /// modifier `parse` names five ways.
    #[test]
    fn the_portable_spelling_parses_back_to_the_same_chord() {
        for s in [
            "ctrl+shift+i",
            "f12",
            "cmd+alt+d",
            "⌃⌥⇧⌘s",
            "mod+pageup",
            "shift+/",
        ] {
            let a = Accel::parse(s).unwrap();
            assert_eq!(
                Accel::parse(&a.spelling()),
                Some(a),
                "{s} -> {}",
                a.spelling()
            );
        }
        assert_eq!(
            Accel::parse("shift+ctrl+I").unwrap().spelling(),
            "ctrl+shift+i"
        );
        assert_eq!(Accel::parse("win+f12").unwrap().spelling(), "super+f12");
    }

    /// What a menu draws parses back to the chord it was drawn from: the
    /// macOS bar binds its key equivalent off the normalized text, and a
    /// `⌘⌫` read as the character `⌫` bound a key no keyboard has.
    #[test]
    fn the_displayed_spelling_parses_back_to_the_same_chord() {
        for (code, _) in KeyCode::named() {
            let mods = KeyMods::NONE.with_shift().with_super();
            let a = Accel { code: *code, mods };
            // A modifier is no shortcut's key, and Play/Pause's pause key
            // is spelled as Pause's: that one reads back as Pause.
            if code.is_modifier() || *code == KeyCode::MediaPause {
                continue;
            }
            assert_eq!(Accel::parse(&a.display()), Some(a), "{}", a.display());
            for mac in [true, false] {
                let label = key_label_on(*code, mac);
                assert_eq!(key_from_label(&label), Some(*code), "{label}");
            }
        }
        let trash = Accel::parse(&Accel::label("mod+backspace")).unwrap();
        assert_eq!(trash.code, KeyCode::Backspace);
        assert_eq!(trash.key_equivalent().as_deref(), Some("\u{8}"));
    }

    #[test]
    fn a_shortcut_kui_cannot_name_is_not_a_shortcut() {
        assert!(Accel::parse("mod+nope").is_none());
        // A lock key is no shortcut's key (backlog RG96).
        assert!(Accel::parse("ctrl+capslock").is_none());
        assert!(Accel::parse("numlock").is_none());
        assert!(Accel::parse("shift+scrolllock").is_none());
        assert!(Accel::parse("s+s").is_none());
        assert!(Accel::parse("").is_none());
    }

    #[test]
    fn a_key_equivalent_is_lowercase() {
        // AppKit reads an uppercase key equivalent as Shift being held, so
        // ⌘S must be sent as "s" with the Command flag and nothing else.
        assert_eq!(
            Accel::parse("cmd+S").unwrap().key_equivalent().as_deref(),
            Some("s")
        );
    }
}