crcbl-input 0.2.0

//! Device-agnostic action system: gameplay and UI code consume **actions**,
//! never raw devices. Keyboard, mouse, gamepad and on-screen controls are
//! interchangeable binding sources behind one config layer.
//!
//! # Contexts
//!
//! Every action belongs to one named context: [`ActionMap::declare`] puts it in
//! [`GAMEPLAY_CONTEXT`], which is always active, and [`ActionMap::declare_in`]
//! names another. [`ActionMap::push_context`] and [`ActionMap::pop_context`]
//! stack contexts over it — [`ActionMap::push_context_modal`] one that passes
//! nothing it does not bind — [`GLOBAL_CONTEXT`] stays above them all, and
//! **the topmost active context that binds an input consumes it** — `context.rs` has the rules, including what happens to a key
//! held while the stack changes, and what [`ActionMap::suppress_held`] and
//! [`ActionMap::suppress_held_action`] withhold on request. [`ui`] declares the
//! engine's reserved `ui`
//! context, [`text`] the `text` context a text field pushes over it, and
//! [`list`] the `list` context an open pop-up list pushes over it.
//!
//! # Patterns and devices
//!
//! [`ActionMap::set_repeat`] attaches a [`Repeat`] to an action, and
//! [`ActionMap::set_tap`], [`ActionMap::set_hold`] and
//! [`ActionMap::set_double_tap`] attach a [`Tap`], a [`Hold`] and a
//! [`DoubleTap`], all evaluated on the clock [`ActionMap::begin_tick`] advances
//! (`repeat.rs`, and `patterns.rs` for how the last three share a press and
//! what [`ActionMap::cancel_patterns`] cancels). [`ActionMap::set_emits`] makes
//! one of the last three press a named button action when it fires
//! (`emit.rs`).
//! [`ActionMap::last_device`] names the kind of [`Device`] that last spoke,
//! [`ActionMap::last_device_changed`] says it just changed, and
//! [`ActionMap::hint`] how an action's binding is shown to the player on it
//! ([`hint`]).
//!
//! # Why an input did what it did
//!
//! [`ActionMap::set_tracing`] records, for each press, the context that
//! consumed it and every binding that read it — or that a modal context
//! stopped it, or that nothing binds it — in a bounded ring an input
//! inspector reads ([`trace`]).
//!
//! # Gamepads
//!
//! Every pad backend emits [`GamepadEvent`]s, by the conventions `gamepad.rs`
//! states — positional buttons, sticks with +Y up, triggers 0…1, raw axes. A
//! game reads them directly, or feeds [`ActionMap::gamepad_event`], where
//! [`Binding::PadButton`], [`Binding::PadDpad`], [`Binding::PadStick`] and
//! [`Binding::PadTrigger`] read them. The Windows backend is `xinput`,
//! compiled on Windows only, the Linux one is `evdev`, compiled on Linux only,
//! the macOS one is `game_controller`, compiled on macOS only, and the browser
//! one is `web_gamepad`, compiled on `wasm32` only: no other target has a
//! backend yet, and none has a stand-in that would report "no pads" as though
//! it had looked.

mod active_pad;
pub mod binding_asset;
pub mod binding_text;
mod context;
mod device;
mod eight_way;
mod emit;
// Linux-only: the `evdev` backend. Compiled into every target's tests too, so
// its mapping, normalisation, layouts and poller run on the Windows and macOS
// runners; only the device access is Linux-only.
#[cfg(any(target_os = "linux", test))]
pub mod evdev;
#[cfg(test)]
mod ffi_layout;
// The clamp for pad values that arrive as floats, which the browser and
// GameController backends share.
#[cfg(any(target_arch = "wasm32", target_os = "macos", test))]
mod float_axis;
// macOS-only: the GameController.framework backend. Compiled into every
// target's tests too, so its mapping, classification and poller run on the
// Windows and Linux runners; only the framework access is macOS-only.
#[cfg(any(target_os = "macos", test))]
pub mod game_controller;
mod gamepad;
pub mod hint;
pub mod list;
mod overrides;
mod patterns;
// The name match the browser and GameController backends name a pad's family
// from when they have no USB ids.
#[cfg(any(target_arch = "wasm32", target_os = "macos", test))]
mod product_name;
mod repeat;
pub mod text;
pub mod trace;
pub mod ui;
// The vendor and product ids the evdev and browser backends name a pad's
// family from; only those two read them.
#[cfg(any(target_os = "linux", target_arch = "wasm32", test))]
mod usb;
// wasm32-only: the Web Gamepad API backend. Compiled into every target's tests
// too, so its mapping, poller and shim entry points run on the native runners;
// only the symbols a page calls are exported, and only from a wasm32 build.
#[cfg(any(target_arch = "wasm32", test))]
pub mod web_gamepad;
// Compiled into every target's tests too, so the mapping and the layouts are
// checked on the Linux and macOS runners; only the loader is Windows-only.
#[cfg(any(windows, test))]
pub mod xinput;

pub use active_pad::{ActivePad, StickUpdate};
pub use binding_asset::{AssetRefusal, AssetWriteError, BindingAssetError};
pub use binding_text::BindingParseError;
pub use context::{GAMEPLAY_CONTEXT, GLOBAL_CONTEXT};
pub use device::Device;
pub use eight_way::{EIGHT_WAY_SECTOR, eight_way};
pub use emit::Pattern;
pub use gamepad::{
    GamepadEvent, GamepadId, GamepadSnapshot, PAD_ACTIVITY_THRESHOLD, PadAxis, PadButton,
    PadButtons, PadKind, Stick, Trigger, radial_deadzone,
};
pub use hint::{DefaultLabels, Hint, HintLabels};
pub use overrides::{ActionOverride, OverrideRefusal};
pub use patterns::{DOUBLE_TAP_WINDOW, DoubleTap, HOLD_TIME, Hold, TAP_TIME, Tap};
pub use repeat::{Cardinal, REPEAT_DELAY, REPEAT_INTERVAL, Repeat};
pub use trace::{Outcome, RESOLUTION_TRACE_CAP, TraceEntry, TracedInput, TracedRead};

use context::{Routes, Suppressed, View};
use crcbl_core::input::{KeyCode, PointerButton};
use patterns::PatternState;
use repeat::RepeatState;
use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};

/// Every connected pad and what it last reported, ordered by id so a sum over
/// them runs in the same order every run.
type Pads = BTreeMap<GamepadId, GamepadSnapshot>;

/// Every key held down, with the serial of the press that put it there — a
/// later press has a larger one, which is how a [`Binding::ScrollChord`] finds
/// the most recently pressed key.
type HeldKeys = HashMap<KeyCode, u64>;

// ---------------------------------------------------------------------------
// Action primitives
// ---------------------------------------------------------------------------

/// A digital action: pressed / released / held with duration.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum ButtonState {
    /// The button just went down this tick (or is being pressed for the first time).
    Pressed,
    /// The button came up this tick.
    Released,
    /// The button has been held for `duration` seconds.
    Held {
        /// Seconds since the button first went down.
        duration: f32,
    },
}

/// Button action with edge-detection flags.
///
/// `just_pressed` and `just_released` are true only on the tick the transition
/// occurred. They are cleared by [`ActionMap::begin_tick`] (and may also be
/// cleared earlier by the consumer via [`ActionMap::action_mut`]).
#[derive(Debug, Clone)]
pub struct ButtonAction {
    /// Current button state.
    pub state: ButtonState,
    /// True on the tick the button went down.
    pub just_pressed: bool,
    /// True on the tick the button came up.
    pub just_released: bool,
}

impl ButtonAction {
    fn reset_edges(&mut self) {
        self.just_pressed = false;
        self.just_released = false;
    }
}

impl Default for ButtonAction {
    fn default() -> Self {
        Self {
            state: ButtonState::Released,
            just_pressed: false,
            just_released: false,
        }
    }
}

/// 1-D analog axis: −1.0 … 1.0 (triggers, scroll wheels, an absolute pointer
/// coordinate).
#[derive(Debug, Clone, Copy, Default, PartialEq)]
pub struct Axis1Action {
    /// Current axis value.
    pub value: f32,
    /// True on the tick a [`Binding::PointerPosition`] on this action reported a
    /// coordinate different from the one it was holding.
    ///
    /// The edge an *absolute* source has and a relative one does not. A scroll
    /// axis returns to zero every [`ActionMap::begin_tick`], so a non-zero value
    /// already means "this moved"; a pointer axis holds its position across
    /// ticks — that is the whole point of it — so its value says where the
    /// pointer is and nothing about whether the player just asked for anything.
    ///
    /// Cleared by [`ActionMap::begin_tick`], like [`ButtonAction::just_pressed`].
    /// A consumer that drives one thing from both a pointer and the keyboard
    /// reads this to decide which spoke most recently — see the
    /// [`Binding::PointerPosition`] docs.
    pub pointer_moved: bool,
}

/// 2-D analog axis (WASD composite, stick, mouse motion).
///
/// Key-driven composites are normalized to at most unit length; mouse motion is
/// a raw pixel delta and is not.
#[derive(Debug, Clone, Copy, Default, PartialEq)]
pub struct Axis2Action {
    /// Horizontal component.
    pub x: f32,
    /// Vertical component.
    pub y: f32,
}

/// A unified action value — one variant per action kind.
#[derive(Debug, Clone)]
pub enum ActionValue {
    /// A button action.
    Button(ButtonAction),
    /// A 1-D axis action.
    Axis1(Axis1Action),
    /// A 2-D axis action.
    Axis2(Axis2Action),
}

// ---------------------------------------------------------------------------
// Bindings
// ---------------------------------------------------------------------------

/// Which coordinate of the pointer a [`Binding::PointerPosition`] reads.
///
/// One binding with an axis rather than a `PointerX`/`PointerY` pair: the two
/// would be the same variant twice, and a rebind menu listing both as unrelated
/// sources is a menu that has to explain why.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PointerAxis {
    /// Horizontal: −1.0 at the left edge of the surface, +1.0 at the right.
    X,
    /// Vertical: −1.0 at the **bottom** edge, +1.0 at the top.
    Y,
}

/// The modifier a [`Binding::Chord`] or a [`Binding::ButtonChord`] waits for:
/// either of its two keys.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum Modifier {
    /// [`KeyCode::ShiftLeft`] or [`KeyCode::ShiftRight`].
    Shift,
    /// [`KeyCode::ControlLeft`] or [`KeyCode::ControlRight`].
    Control,
    /// [`KeyCode::AltLeft`] or [`KeyCode::AltRight`].
    Alt,
    /// [`KeyCode::SuperLeft`] or [`KeyCode::SuperRight`].
    Super,
}

impl Modifier {
    /// The left and the right key of this modifier.
    #[must_use]
    pub const fn keys(self) -> [KeyCode; 2] {
        match self {
            Self::Shift => [KeyCode::ShiftLeft, KeyCode::ShiftRight],
            Self::Control => [KeyCode::ControlLeft, KeyCode::ControlRight],
            Self::Alt => [KeyCode::AltLeft, KeyCode::AltRight],
            Self::Super => [KeyCode::SuperLeft, KeyCode::SuperRight],
        }
    }

    /// The modifier `key` is one side of, if it is one.
    #[must_use]
    pub const fn of(key: KeyCode) -> Option<Self> {
        match key {
            KeyCode::ShiftLeft | KeyCode::ShiftRight => Some(Self::Shift),
            KeyCode::ControlLeft | KeyCode::ControlRight => Some(Self::Control),
            KeyCode::AltLeft | KeyCode::AltRight => Some(Self::Alt),
            KeyCode::SuperLeft | KeyCode::SuperRight => Some(Self::Super),
            _ => None,
        }
    }

    /// Whether either side is in `held`.
    fn held(self, held: &HeldKeys) -> bool {
        self.keys().iter().any(|key| held.contains_key(key))
    }
}

/// A binding source: what raw input triggers this action.
///
/// Keyboard, mouse, gamepad and on-screen controls. A game
/// played with **one** finger needs nothing touch-specific — the platforms
/// deliver the primary contact as an ordinary pointer, so
/// [`Binding::MouseButton`] and [`Binding::PointerPosition`] are what a phone
/// plays it through. [`Binding::Virtual`] is what a game needs when one finger
/// is not enough.
///
/// `PartialEq` and not `Eq`: a pad binding's dead zone is an `f32`.
///
/// Its `Display` and `FromStr` are a stable text form, `KeyR` or `Pad:South`,
/// for a player's saved rebinds; [`binding_text`] has the spelling of each.
#[derive(Debug, Clone, PartialEq)]
pub enum Binding {
    /// A single key.
    Key(KeyCode),
    /// A mouse button.
    MouseButton(PointerButton),
    /// Mouse motion (delta in pixels).
    MouseMotion,
    /// Mouse scroll wheel.
    MouseScroll,
    /// Where the pointer **is**, normalised to the surface it is over: −1.0 at
    /// one edge, +1.0 at the other, with +X right and +Y up.
    ///
    /// Drives an [`ActionKind::Axis1`], whose −1…1 range is already exactly a
    /// normalised coordinate. Feeding an `Axis2` instead would put a *place* in
    /// the same value as [`Binding::Wasd`]'s *direction*, and a consumer handed
    /// `(0.5, 0.0)` could not tell "half way to the right edge" from "moving
    /// right at half speed"; a fourth [`ActionKind`] for one binding would be a
    /// whole value shape for a case `Axis1` already covers. Any other kind
    /// ignores this binding, as [`Binding::MouseMotion`] does on a button.
    ///
    /// **Normalised, not pixels**, because pixels are the surface's business:
    /// a device-pixel coordinate makes every consumer redo the DPI arithmetic
    /// the windowing layer already did, and get it wrong on exactly the displays
    /// nobody develops on. What the consumer still owns is the step from the
    /// surface to its own world — a camera's half width is not the map's to
    /// know.
    ///
    /// **A pointer that leaves keeps its last position.** Leaving is not a
    /// command: the platform reports it with no coordinate at all, so there is
    /// nothing to resolve, and an axis that recentred itself would walk a
    /// paddle to the middle of the field every time a finger lifted.
    ///
    /// **On an axis that also has a relative source** — a [`Binding::KeyAxis`],
    /// a [`Binding::MouseScroll`] — this one wins whenever the pointer has a
    /// position, because summing them would add a place to a rate and produce
    /// neither. That is a resolution, not an arbitration: a consumer whose
    /// keyboard means something genuinely different from its pointer (a paddle
    /// driven left at a speed, versus a paddle put at a coordinate) declares two
    /// actions and picks between them with
    /// [`Axis1Action::pointer_moved`].
    PointerPosition {
        /// Which coordinate this action reads.
        axis: PointerAxis,
    },
    /// Two keys driving one 1-D axis: `negative` contributes −1.0, `positive`
    /// +1.0, and both at once cancel.
    ///
    /// A single [`Binding::Key`] on an `Axis1` can only ever push the axis
    /// positive, so a keyboard-driven throttle or zoom needs this.
    KeyAxis {
        /// Key for the −1.0 direction.
        negative: KeyCode,
        /// Key for the +1.0 direction.
        positive: KeyCode,
    },
    /// A key that counts only while a [`Modifier`] is held — Shift+Tab.
    ///
    /// **The more specific binding takes the key.** While the modifier is
    /// held, every plain [`Binding::Key`], [`Binding::KeyAxis`] and
    /// [`Binding::Wasd`] on the same key, in the context that owns the key,
    /// reads it as up — so `ui_next` on Tab and `ui_prev` on Shift+Tab never
    /// both fire. Holding Tab and then pressing Shift therefore releases the
    /// one and presses the other.
    ///
    /// **The modifier is read, not consumed**: a chord owns its `key` and
    /// nothing else, so a Shift+Tab in a pushed context leaves a sprint bound
    /// to Shift in the context beneath it alone.
    Chord {
        /// The modifier that must be held.
        modifier: Modifier,
        /// The key the chord owns.
        key: KeyCode,
    },
    /// A mouse button that counts only while a [`Modifier`] is held —
    /// Alt+right click beside a plain right click. The mouse's
    /// [`Binding::Chord`], on the same two rules, and read as
    /// [`Binding::MouseButton`] is: down on an [`ActionKind::Button`], inert
    /// on the other kinds.
    ///
    /// **The more specific binding takes the button.** While the modifier is
    /// held, every plain [`Binding::MouseButton`] on the same button, in the
    /// context that owns the button, reads it as up — so an aim on the right
    /// button and a zoom on Alt+right never both fire. Holding the button and
    /// then pressing the modifier releases the one and presses the other;
    /// letting the modifier go first hands the button back.
    ///
    /// **The modifier is read, not consumed**: a button chord owns its
    /// `button` and nothing else, so a lean bound to Alt still sees every
    /// press of Alt, chorded or not.
    ButtonChord {
        /// The modifier that must be held.
        modifier: Modifier,
        /// The mouse button the chord owns.
        button: PointerButton,
    },
    /// The mouse wheel, read only while `held` is down — Z+wheel, Ctrl+wheel.
    ///
    /// Read as [`Binding::MouseScroll`] is: the vertical delta on an
    /// [`ActionKind::Axis1`], inert on the other kinds. It reads the wheel as
    /// one, too, so it takes the wheel for its context as a `MouseScroll`
    /// would.
    ///
    /// **The more specific binding takes the wheel**, as it takes the key for a
    /// [`Binding::Chord`]: while the `held` key of any scroll chord in the
    /// context that owns the wheel is down, every plain `MouseScroll` in that
    /// context reads zero. **With several of those keys down, the most recently
    /// pressed one takes the wheel** and the chords on the others read zero,
    /// so letting go of it hands the wheel back to the one pressed before. An
    /// OS auto-repeat of a key already down is not a press and takes nothing.
    ///
    /// **The held key is read, not consumed**, as a chord's modifier is: a
    /// scroll chord owns the wheel and nothing else, so a [`Binding::Key`] on
    /// Z still sees Z — a game that also taps Z cancels that tap with
    /// [`ActionMap::cancel_patterns`] when the wheel turns. A held key
    /// withheld from its owner (see `context.rs`) is up for this read too.
    ///
    /// **Only an enabled action's scroll chord competes.** A key whose action
    /// is disabled ([`ActionMap::set_enabled`]) takes the wheel from nothing
    /// and silences no plain `MouseScroll`, however recently it was pressed:
    /// Ctrl held for one chord keeps the wheel when Alt goes down for a chord
    /// that cannot act right now. Enabling it again restores its place by
    /// when its key went down, not by when it was enabled.
    ScrollChord {
        /// The key that must be down; any key, modifiers included.
        held: KeyCode,
    },
    /// An **on-screen control**, by the id the widget drawing it was given.
    ///
    /// The touch row of a binding table, and the one binding whose device is a
    /// piece of the game's own UI: a `crcbl-ui` control hit-tests the raw
    /// contacts, decides what its geometry makes of them, and reports the
    /// result here through [`ActionMap::virtual_button`] or
    /// [`ActionMap::virtual_stick`]. From this side it is a device like any
    /// other — the same action can carry a key, a mouse button and one of
    /// these, and nothing downstream can tell which of them spoke.
    ///
    /// That split is deliberate and it is why there is no binding on a raw
    /// contact. A finger reports a *place on the glass*; what it means is a
    /// question only the thing drawn under it can answer, and an [`ActionMap`]
    /// that hit-tested widgets would have to be told where every control was
    /// drawn this frame.
    ///
    /// **A control is a button or a stick, and an action reads whichever
    /// matches its own kind**: an [`ActionKind::Button`] is down while the
    /// named control is held, an [`ActionKind::Axis2`] takes the named
    /// control's deflection, and an [`ActionKind::Axis1`] takes **nothing** —
    /// reducing a stick to one axis is a choice the control would have to make
    /// and none of them makes it. A binding whose kind does not match is inert,
    /// the way [`Binding::MouseMotion`] is on a button.
    ///
    /// The vector arrives already inside the unit disc, and is clamped to it
    /// again here: a control with a longer throw than its own radius is a
    /// broken control, not a player asking to run faster.
    Virtual(String),
    /// WASD composite: four keys mapped to a 2-D axis.
    ///
    /// The composite is normalized, so a diagonal is a unit vector rather than
    /// `(1, 1)` — otherwise diagonal movement is 41% faster than cardinal.
    Wasd {
        /// Key for the +Y direction (forward / up).
        up: KeyCode,
        /// Key for the −Y direction (back / down).
        down: KeyCode,
        /// Key for the −X direction (left).
        left: KeyCode,
        /// Key for the +X direction (right).
        right: KeyCode,
    },
    /// A pad button, by position — see [`PadButton`].
    ///
    /// Read like a [`Binding::Key`]: down on an [`ActionKind::Button`], +1.0 on
    /// an [`ActionKind::Axis1`], nothing on an [`ActionKind::Axis2`] — the
    /// d-pad's `Axis2` is [`Binding::PadDpad`]. Down while any connected pad
    /// holds it.
    PadButton(PadButton),
    /// The d-pad as one 2-D axis: [`Binding::Wasd`] over
    /// [`PadButton::DpadUp`], [`PadButton::DpadDown`], [`PadButton::DpadLeft`]
    /// and [`PadButton::DpadRight`], +Y up.
    ///
    /// Resolved exactly as `Wasd` is: into the same unit disc as the keys and
    /// the sticks on the action, so a diagonal is a unit vector and opposite
    /// directions cancel; down on an [`ActionKind::Button`] while any of the
    /// four is held; inert on an [`ActionKind::Axis1`]. It owns the four
    /// buttons for routing, as `Wasd` owns its four keys.
    PadDpad,
    /// A pad stick's deflection, +Y up, through a **scaled radial** dead zone:
    /// zero within `deadzone` of centre, rescaled so the zone's edge reads 0
    /// and full throw reads 1.
    ///
    /// Drives an [`ActionKind::Axis2`], into the same unit disc as a
    /// [`Binding::Wasd`] or a [`Binding::Virtual`] stick on the action, so a
    /// stick and a key pushed together ask for one direction. Inert on the
    /// other kinds, as a [`Binding::Virtual`] stick is on an `Axis1`.
    PadStick {
        /// Which stick.
        stick: Stick,
        /// The dead zone's radius, in `0.0..1.0`; anything else is refused
        /// with [`ActionMapError::InvalidDeadzone`].
        deadzone: f32,
    },
    /// A pad button that counts only while another pad button is held — a
    /// held shoulder giving the face buttons a second layer. The pad's
    /// [`Binding::Chord`], on the same two rules:
    ///
    /// **The more specific binding takes the button.** While `modifier` is
    /// held, every plain [`Binding::PadButton`] on `button` (and a
    /// [`Binding::PadDpad`] reading it), in the context that owns the button,
    /// reads it as up — so a jump on South and a vault on LB+South never both
    /// fire. Holding South and then pressing LB releases the one and presses
    /// the other. A chord in a context beneath the owner reads nothing,
    /// unless its action is marked with [`ActionMap::set_pad_chords_outrank`]:
    /// then it takes the button from the contexts above while `modifier` is
    /// held (`context.rs`).
    ///
    /// **The modifier is read, not consumed**: a pad chord owns its `button`
    /// and nothing else, so `modifier` can still carry a plain binding of its
    /// own, which sees every press of it, chorded or not.
    PadChord {
        /// The pad button that must be held.
        modifier: PadButton,
        /// The pad button the chord owns.
        button: PadButton,
    },
    /// A pad trigger past a threshold.
    ///
    /// On an [`ActionKind::Button`], down while the pull is past `threshold`;
    /// on an [`ActionKind::Axis1`], the pull rescaled so the threshold reads 0
    /// and full pull reads 1. Inert on an [`ActionKind::Axis2`].
    PadTrigger {
        /// Which trigger.
        trigger: Trigger,
        /// The threshold, in `0.0..1.0`; anything else is refused with
        /// [`ActionMapError::InvalidDeadzone`].
        threshold: f32,
    },
}

impl Binding {
    /// Calls `visit` with every key this binding owns — the keys a context
    /// consumes by binding it. A [`Binding::Chord`]'s modifier is not one, and
    /// neither is a [`Binding::ScrollChord`]'s held key.
    pub fn visit_keys(&self, mut visit: impl FnMut(KeyCode)) {
        match self {
            Self::Key(key) | Self::Chord { key, .. } => visit(*key),
            Self::KeyAxis { negative, positive } => {
                visit(*negative);
                visit(*positive);
            }
            Self::Wasd {
                up,
                down,
                left,
                right,
            } => {
                visit(*up);
                visit(*down);
                visit(*left);
                visit(*right);
            }
            Self::MouseButton(_)
            | Self::ButtonChord { .. }
            | Self::MouseMotion
            | Self::MouseScroll
            | Self::ScrollChord { .. }
            | Self::PointerPosition { .. }
            | Self::Virtual(_)
            | Self::PadButton(_)
            | Self::PadChord { .. }
            | Self::PadDpad
            | Self::PadStick { .. }
            | Self::PadTrigger { .. } => {}
        }
    }

    /// Whether this binding reads the mouse wheel.
    const fn reads_wheel(&self) -> bool {
        matches!(self, Self::MouseScroll | Self::ScrollChord { .. })
    }

    /// The mouse button this binding owns, if it reads one: a
    /// [`Binding::ButtonChord`]'s button as much as a
    /// [`Binding::MouseButton`]'s.
    const fn mouse_button(&self) -> Option<PointerButton> {
        match *self {
            Self::MouseButton(button) | Self::ButtonChord { button, .. } => Some(button),
            _ => None,
        }
    }

    /// Whether this binding reads a gamepad.
    #[must_use]
    pub const fn reads_gamepad(&self) -> bool {
        matches!(
            self,
            Self::PadButton(_)
                | Self::PadChord { .. }
                | Self::PadDpad
                | Self::PadStick { .. }
                | Self::PadTrigger { .. }
        )
    }

    /// Whether this binding's dead zone or threshold is usable, if it has one.
    fn deadzone_is_valid(&self) -> bool {
        match *self {
            Self::PadStick { deadzone, .. } => gamepad::valid_deadzone(deadzone),
            Self::PadTrigger { threshold, .. } => gamepad::valid_deadzone(threshold),
            _ => true,
        }
    }

    /// Whether this binding reads the keyboard at all.
    fn reads_keyboard(&self) -> bool {
        let mut any = false;
        self.visit_keys(|_| any = true);
        any
    }

    /// Whether this binding owns `key`.
    #[must_use]
    pub fn owns_key(&self, key: KeyCode) -> bool {
        let mut owns = false;
        self.visit_keys(|owned| owns |= owned == key);
        owns
    }
}

// ---------------------------------------------------------------------------
// Action declaration
// ---------------------------------------------------------------------------

/// What kind of value an action produces.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ActionKind {
    /// A digital on/off action with edge detection.
    Button,
    /// A 1-D analog axis.
    Axis1,
    /// A 2-D analog axis.
    Axis2,
}

/// A declared action: name + kind + bindings.
#[derive(Debug, Clone)]
pub struct ActionDecl {
    /// Human-readable name, used as the lookup key in [`ActionMap`].
    pub name: String,
    /// What kind of value this action produces.
    pub kind: ActionKind,
    /// The raw inputs that drive this action.
    pub bindings: Vec<Binding>,
}

// ---------------------------------------------------------------------------
// Internal per-action state
// ---------------------------------------------------------------------------

/// Tracks the resolved value and edge-transition bookkeeping for one action.
#[derive(Debug, Clone)]
struct ActionSlot {
    decl: ActionDecl,
    /// The bindings it was declared with, which [`ActionMap::rebind`] leaves
    /// alone: the defaults a player's overrides are a diff over.
    defaults: Vec<Binding>,
    /// Index into [`ActionMap::contexts`] of the context this action is in.
    context: usize,
    /// The repeat pattern, if one is attached — see [`ActionMap::set_repeat`].
    repeat: Option<RepeatState>,
    /// The tap, hold and double-tap patterns — see [`ActionMap::set_tap`].
    patterns: PatternState,
    /// Whether a pattern emitting this action fired since the last
    /// [`ActionMap::begin_tick`], which holds it down until then — see
    /// `emit.rs`.
    emitted: bool,
    /// The current resolved value.
    value: ActionValue,
    /// True when at least one binding for this action is "down" (key held,
    /// button held, etc.). Used to detect press / release edges.
    active: bool,
    /// Accumulated time at which the action became active (None when inactive).
    /// Used to compute `Held { duration }`.
    hold_start: Option<f64>,
    /// Whether this action reacts to input at all.
    ///
    /// A flag on the slot rather than a `HashSet<String>` on the map: the set
    /// was hashed once per slot per raw event, and `set_enabled` on a name that
    /// was never declared grew it forever.
    enabled: bool,
    /// Whether its pad chords take their button from a context above — see
    /// [`ActionMap::set_pad_chords_outrank`].
    pad_chords_outrank: bool,
}

impl ActionSlot {
    fn new(decl: ActionDecl, context: usize) -> Self {
        let value = match decl.kind {
            ActionKind::Button => ActionValue::Button(ButtonAction::default()),
            ActionKind::Axis1 => ActionValue::Axis1(Axis1Action::default()),
            ActionKind::Axis2 => ActionValue::Axis2(Axis2Action::default()),
        };
        Self {
            defaults: decl.bindings.clone(),
            decl,
            context,
            repeat: None,
            patterns: PatternState::default(),
            emitted: false,
            value,
            active: false,
            hold_start: None,
            enabled: true,
            pad_chords_outrank: false,
        }
    }

    /// Returns the declared kind.
    fn kind(&self) -> ActionKind {
        self.decl.kind
    }

    /// Force the action back to its idle value and drop any hold state.
    fn reset(&mut self) {
        self.active = false;
        self.hold_start = None;
        if let Some(repeat) = &mut self.repeat {
            repeat.reset();
        }
        self.patterns.reset();
        self.emitted = false;
        match &mut self.value {
            ActionValue::Button(a) => {
                a.state = ButtonState::Released;
                a.just_pressed = false;
                a.just_released = false;
            }
            ActionValue::Axis1(a) => {
                a.value = 0.0;
                a.pointer_moved = false;
            }
            ActionValue::Axis2(a) => {
                a.x = 0.0;
                a.y = 0.0;
            }
        }
    }
}

// ---------------------------------------------------------------------------
// Errors
// ---------------------------------------------------------------------------

/// What can go wrong when mutating an [`ActionMap`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ActionMapError {
    /// An action with this name is already declared.
    DuplicateName(String),
    /// No action with this name has been declared.
    UnknownAction(String),
    /// No context with this name has been declared.
    UnknownContext(String),
    /// [`ActionMap::push_context`] was asked for a context already active —
    /// [`GAMEPLAY_CONTEXT`] and [`GLOBAL_CONTEXT`] always are.
    ContextAlreadyActive(String),
    /// [`ActionMap::pop_context`] was asked for a context that is not the
    /// topmost pushed one — [`GAMEPLAY_CONTEXT`] and [`GLOBAL_CONTEXT`] are
    /// never pushed.
    ContextNotOnTop(String),
    /// A [`Binding::PadStick`]'s dead zone or a [`Binding::PadTrigger`]'s
    /// threshold on the named action is not finite and in `0.0..1.0`.
    InvalidDeadzone(String),
    /// [`ActionMap::set_emits`] was asked to make a pattern emit an action
    /// that is not an [`ActionKind::Button`].
    NotAButton(String),
    /// [`ActionMap::set_emits`] was asked to make a pattern emit the action it
    /// is attached to.
    EmitsItself(String),
}

impl std::fmt::Display for ActionMapError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::DuplicateName(name) => write!(f, "duplicate action name: {name}"),
            Self::UnknownAction(name) => write!(f, "no such action: {name}"),
            Self::UnknownContext(name) => write!(f, "no such context: {name}"),
            Self::ContextAlreadyActive(name) => write!(f, "context already active: {name}"),
            Self::ContextNotOnTop(name) => {
                write!(f, "context is not the topmost pushed one: {name}")
            }
            Self::InvalidDeadzone(name) => {
                write!(f, "dead zone or threshold not in 0..1: {name}")
            }
            Self::NotAButton(name) => {
                write!(f, "a pattern can emit only a button action: {name}")
            }
            Self::EmitsItself(name) => {
                write!(f, "a pattern cannot emit the action it is on: {name}")
            }
        }
    }
}

impl std::error::Error for ActionMapError {}

// ---------------------------------------------------------------------------
// ActionMap
// ---------------------------------------------------------------------------

/// Resolves raw input events to action values.
///
/// Bindings are declared once via [`ActionMap::declare`] and then driven by
/// feeding raw events (`key_event`, `mouse_button`, `mouse_motion`,
/// `mouse_scroll`).  Per-tick bookkeeping is done with [`ActionMap::begin_tick`].
pub struct ActionMap {
    /// All declared actions, in registration order.
    slots: Vec<ActionSlot>,
    /// name → index into `slots`.
    name_to_idx: HashMap<String, usize>,

    // Contexts ---------------------------------------------------------------
    /// Every declared context's name, in declaration order;
    /// [`GAMEPLAY_CONTEXT`] is index 0 and [`GLOBAL_CONTEXT`] index 1.
    contexts: Vec<String>,
    /// The pushable stack as indices into `contexts`, bottom first. Never
    /// empty: index 0 is the base and is never popped. [`GLOBAL_CONTEXT`] is
    /// always active and is not on it.
    stack: Vec<usize>,
    /// The contexts on `stack` that were pushed modal.
    modal: Vec<usize>,
    /// Which active context owns each bound input, rebuilt whenever the stack
    /// or a binding changes.
    routes: Routes,
    /// Held inputs withheld from their owner until released, because the
    /// stack changed under them.
    suppressed: Suppressed,
    /// Every kind of device that has spoken, most recent first and each
    /// once — see [`ActionMap::last_device`], and `hint.rs` for why the ones
    /// behind it are kept.
    devices: Vec<Device>,
    /// The family of the pad that last spoke — see
    /// [`ActionMap::last_pad_kind`].
    last_pad_kind: Option<PadKind>,
    /// Whether the front of `devices` changed since the last
    /// [`ActionMap::begin_tick`] — see [`ActionMap::last_device_changed`].
    device_changed: bool,
    /// The resolution trace, while [`ActionMap::set_tracing`] has it on — see
    /// `trace.rs`.
    trace: Option<VecDeque<TraceEntry>>,

    // Raw input state -------------------------------------------------------
    held_keys: HeldKeys,
    /// The serial of the last key press — see [`HeldKeys`].
    key_presses: u64,
    held_buttons: HashSet<PointerButton>,
    /// On-screen controls currently held — see [`Binding::Virtual`].
    held_controls: HashSet<String>,
    /// Where each on-screen stick is deflected to, inside the unit disc.
    ///
    /// A *level*, like [`ActionMap::pointer`] and unlike the two deltas below:
    /// a finger resting on a stick reports nothing on the frames it does not
    /// move, so a value cleared by [`ActionMap::begin_tick`] would centre the
    /// stick under a finger that never let go.
    control_sticks: HashMap<String, (f32, f32)>,
    /// Every connected pad's last snapshot — a level, like `control_sticks`.
    /// See `gamepad.rs`.
    pads: Pads,
    /// Every button some pad holds, as one set for routing to read.
    held_pad_buttons: PadButtons,
    mouse_delta: (f32, f32),
    scroll_delta: (f32, f32),
    /// Where the pointer is, normalised to the surface, or `None` until one has
    /// ever reported a position.
    ///
    /// Not cleared by [`ActionMap::begin_tick`] and not cleared when the pointer
    /// leaves — unlike the two deltas above, this is a *level* and it is the
    /// last thing the player actually asked for. See
    /// [`Binding::PointerPosition`].
    pointer: Option<(f32, f32)>,
    /// Slots a pattern fired an emission at, waiting to be pressed — see
    /// `emit.rs`. Empty between calls.
    pending_emits: Vec<usize>,

    /// Seconds elapsed since creation (advanced by `begin_tick`).
    ///
    /// `f64` rather than `f32`: an `f32` accumulator quantizes `Held`
    /// durations after a few hours of uptime and stops advancing entirely
    /// after about nineteen days, which is well inside a dedicated server's
    /// lifetime.
    elapsed: f64,
}

impl ActionMap {
    /// Create an empty action map.
    #[must_use]
    pub fn new() -> Self {
        Self {
            slots: Vec::new(),
            name_to_idx: HashMap::new(),
            contexts: vec![GAMEPLAY_CONTEXT.to_owned(), GLOBAL_CONTEXT.to_owned()],
            stack: vec![0],
            modal: Vec::new(),
            routes: Routes::default(),
            suppressed: Suppressed::default(),
            devices: Vec::new(),
            last_pad_kind: None,
            device_changed: false,
            trace: None,
            held_keys: HeldKeys::new(),
            key_presses: 0,
            held_buttons: HashSet::new(),
            held_controls: HashSet::new(),
            control_sticks: HashMap::new(),
            pads: Pads::new(),
            held_pad_buttons: PadButtons::EMPTY,
            mouse_delta: (0.0, 0.0),
            scroll_delta: (0.0, 0.0),
            pointer: None,
            pending_emits: Vec::new(),
            elapsed: 0.0,
        }
    }

    /// Register an action in [`GAMEPLAY_CONTEXT`].  Actions are enabled by
    /// default.
    ///
    /// # Panics
    /// Panics if an action with the same name has already been declared. Use
    /// [`ActionMap::try_declare`] when the declaration comes from a user config
    /// file, where a duplicate is a message rather than a crash.
    pub fn declare(&mut self, decl: ActionDecl) {
        if let Err(error) = self.try_declare(decl) {
            panic!("{error}");
        }
    }

    /// Register an action, reporting a duplicate name rather than panicking.
    ///
    /// # Errors
    /// [`ActionMapError::DuplicateName`] if the name is already declared.
    pub fn try_declare(&mut self, decl: ActionDecl) -> Result<(), ActionMapError> {
        self.try_declare_in(GAMEPLAY_CONTEXT, decl)
    }

    /// Register an action in the named context, declaring the context on first
    /// use.
    ///
    /// # Panics
    /// Panics on a duplicate action name, as [`ActionMap::declare`] does.
    pub fn declare_in(&mut self, context: &str, decl: ActionDecl) {
        if let Err(error) = self.try_declare_in(context, decl) {
            panic!("{error}");
        }
    }

    /// Register an action in the named context, reporting a duplicate name
    /// rather than panicking. Action names are unique across every context.
    ///
    /// An action declared into an active context with its input already held
    /// reports it at once, as [`ActionMap::rebind`] does.
    ///
    /// # Errors
    /// [`ActionMapError::DuplicateName`] if the name is already declared,
    /// [`ActionMapError::InvalidDeadzone`] if a pad binding's dead zone or
    /// threshold is unusable.
    pub fn try_declare_in(
        &mut self,
        context: &str,
        decl: ActionDecl,
    ) -> Result<(), ActionMapError> {
        if self.name_to_idx.contains_key(&decl.name) {
            return Err(ActionMapError::DuplicateName(decl.name));
        }
        if !decl.bindings.iter().all(Binding::deadzone_is_valid) {
            return Err(ActionMapError::InvalidDeadzone(decl.name));
        }
        let context = match self.contexts.iter().position(|name| name == context) {
            Some(index) => index,
            None => {
                self.contexts.push(context.to_owned());
                self.contexts.len() - 1
            }
        };
        let idx = self.slots.len();
        self.name_to_idx.insert(decl.name.clone(), idx);
        self.slots.push(ActionSlot::new(decl, context));
        self.reroute();
        Ok(())
    }

    /// Replace an action's bindings in place — the rebind path.
    ///
    /// Keeps the action's registration order and enabled flag, and resets its
    /// value and hold state (the old bindings' "is it down" answer says nothing
    /// about the new ones). Rebuilding the whole map instead, which was the
    /// only option before, lost both.
    ///
    /// # Errors
    /// [`ActionMapError::UnknownAction`] if nothing with that name is declared,
    /// [`ActionMapError::InvalidDeadzone`] if a pad binding's dead zone or
    /// threshold is unusable — and then the old bindings stay.
    pub fn rebind(&mut self, name: &str, bindings: Vec<Binding>) -> Result<(), ActionMapError> {
        let Some(&idx) = self.name_to_idx.get(name) else {
            return Err(ActionMapError::UnknownAction(name.to_owned()));
        };
        if !bindings.iter().all(Binding::deadzone_is_valid) {
            return Err(ActionMapError::InvalidDeadzone(name.to_owned()));
        }
        let slot = &mut self.slots[idx];
        slot.decl.bindings = bindings;
        slot.reset();
        // Every live action, not only this one: the new bindings can take an
        // input from a context beneath, or give one back.
        self.reroute();
        Ok(())
    }

    /// The bindings currently driving an action, or `None` if it is not
    /// declared.
    #[must_use]
    pub fn bindings(&self, name: &str) -> Option<&[Binding]> {
        let &idx = self.name_to_idx.get(name)?;
        Some(&self.slots[idx].decl.bindings)
    }

    /// Whether an action is enabled. `None` if it is not declared.
    #[must_use]
    pub fn is_enabled(&self, name: &str) -> Option<bool> {
        let &idx = self.name_to_idx.get(name)?;
        Some(self.slots[idx].enabled)
    }

    /// Enable or disable an action by name.  Disabled actions always return
    /// their default (idle) value and do not react to input — including across
    /// [`ActionMap::begin_tick`], which used to re-read the held-key set and
    /// re-press a disabled action on the very next tick.
    ///
    /// An action with a [`Binding::ScrollChord`] also leaves or rejoins the
    /// wheel's competition, and the wheel is re-read at once.
    ///
    /// Has no effect if the named action does not exist.
    pub fn set_enabled(&mut self, name: &str, enabled: bool) {
        let Some(&idx) = self.name_to_idx.get(name) else {
            return;
        };
        let slot = &mut self.slots[idx];
        let changed = slot.enabled != enabled;
        slot.enabled = enabled;
        if !enabled {
            // Reset the action to idle so it doesn't stick.
            slot.reset();
        }
        // Only an enabled scroll chord competes for the wheel, so turning one
        // on or off can hand the wheel to another binding.
        let scroll_chord = slot
            .decl
            .bindings
            .iter()
            .any(|binding| matches!(binding, Binding::ScrollChord { .. }));
        if changed && scroll_chord {
            self.reroute();
        }
    }

    // -- feeding raw events --------------------------------------------------

    /// Feed a key event. `pressed` → key-down, `!pressed` → key-up.
    ///
    /// A press makes [`Device::Keyboard`] the last device; a release does not,
    /// since letting go of a key after reaching for the mouse is not the
    /// keyboard speaking.
    pub fn key_event(&mut self, key: KeyCode, pressed: bool) {
        // An OS auto-repeat of a key already down keeps its first serial: it
        // is not a new press, and the trace does not record it again.
        let fresh = pressed && !self.held_keys.contains_key(&key);
        if pressed {
            if fresh {
                self.key_presses += 1;
                self.held_keys.insert(key, self.key_presses);
            }
            self.spoke(Device::Keyboard);
        } else {
            self.held_keys.remove(&key);
            self.suppressed.keys.remove(&key);
        }
        // A scroll chord's key can hand the wheel from one binding to another.
        let wheel = self.routes.is_scroll_chord_key(key);
        if Modifier::of(key).is_some() {
            // A modifier can press or release any chord, and shadow or unshadow
            // any plain key or mouse button a chord shares.
            self.resolve_matching(|b| {
                b.reads_keyboard() || b.mouse_button().is_some() || (wheel && b.reads_wheel())
            });
        } else {
            self.resolve_matching(|b| b.owns_key(key) || (wheel && b.reads_wheel()));
        }
        if fresh {
            self.traced(|| TracedInput::Key(key));
        }
    }

    /// Feed a mouse-button event.
    pub fn mouse_button(&mut self, button: PointerButton, pressed: bool) {
        let mut fresh = false;
        if pressed {
            fresh = self.held_buttons.insert(button);
            self.spoke(Device::Pointer);
        } else {
            self.held_buttons.remove(&button);
            self.suppressed.buttons.remove(&button);
        }
        self.resolve_matching(|b| b.mouse_button() == Some(button));
        if fresh {
            self.traced(|| TracedInput::MouseButton(button));
        }
    }

    /// Feed mouse motion (delta in pixels since the last event).
    ///
    /// Non-finite deltas are dropped: a `NaN` from a driver or a divide-by-zero
    /// sensitivity would otherwise propagate straight into an action value and
    /// poison every comparison downstream.
    pub fn mouse_motion(&mut self, dx: f32, dy: f32) {
        if !dx.is_finite() || !dy.is_finite() {
            return;
        }
        if dx != 0.0 || dy != 0.0 {
            self.spoke(Device::Pointer);
        }
        self.mouse_delta.0 += dx;
        self.mouse_delta.1 += dy;
        self.resolve_matching(|b| matches!(b, Binding::MouseMotion));
    }

    /// Feed scroll input (delta in detents or pixels — caller normalises).
    ///
    /// Non-finite deltas are dropped, as for [`ActionMap::mouse_motion`];
    /// `f32::clamp` returns `NaN` for a `NaN` input, so the clamp downstream is
    /// no defence.
    pub fn mouse_scroll(&mut self, dx: f32, dy: f32) {
        if !dx.is_finite() || !dy.is_finite() {
            return;
        }
        let turned = dx != 0.0 || dy != 0.0;
        if turned {
            self.spoke(Device::Pointer);
        }
        self.scroll_delta.0 += dx;
        self.scroll_delta.1 += dy;
        self.resolve_matching(Binding::reads_wheel);
        if turned {
            self.traced(|| TracedInput::Wheel);
        }
    }

    /// Feed the pointer's position, normalised to the surface: −1.0 at one edge
    /// and +1.0 at the other, +X right and +Y up.
    ///
    /// The caller does the conversion because the caller is the only thing that
    /// knows the surface — see [`Binding::PointerPosition`], which also says why
    /// a pointer that *leaves* is not reported here at all.
    ///
    /// A coordinate equal to the one already held is dropped, so
    /// [`Axis1Action::pointer_moved`] means the pointer moved rather than that
    /// an event arrived. Non-finite coordinates are dropped like
    /// [`ActionMap::mouse_motion`]'s deltas: a `NaN` would poison every
    /// comparison downstream of the axis.
    pub fn pointer_position(&mut self, x: f32, y: f32) {
        if !x.is_finite() || !y.is_finite() {
            return;
        }
        let moved = Some((x, y));
        if self.pointer == moved {
            return;
        }
        self.pointer = moved;
        self.spoke(Device::Pointer);

        for i in 0..self.slots.len() {
            let slot = &self.slots[i];
            let drives = slot
                .decl
                .bindings
                .iter()
                .any(|b| matches!(b, Binding::PointerPosition { .. }));
            // The owner only: a consumed pointer has not moved for anyone else.
            if !self.is_live(i) || !drives || self.routes.pointer != Some(slot.context) {
                continue;
            }
            self.resolve_one(i);
            // Set here rather than in `resolve_one`, which also runs from
            // `begin_tick`: an edge raised by re-resolving an unchanged value
            // would be raised on every tick forever.
            if let ActionValue::Axis1(axis) = &mut self.slots[i].value {
                axis.pointer_moved = true;
            }
        }
    }

    /// Feed an on-screen **button**: the control named by `control` is held, or
    /// it is not.
    ///
    /// The widget decides what "held" means for its own geometry — which
    /// contact owns it, and whether a lift over it commits or cancels. What
    /// arrives here is the answer, and it drives every
    /// [`Binding::Virtual`] with this id on an [`ActionKind::Button`] exactly as
    /// a key event drives a [`Binding::Key`], edges included.
    pub fn virtual_button(&mut self, control: &str, pressed: bool) {
        // `contains` first so a control that is already held costs no
        // allocation: this runs once per frame per held control.
        let fresh = pressed && !self.held_controls.contains(control);
        if pressed {
            if fresh {
                self.held_controls.insert(control.to_owned());
            }
            self.spoke(Device::Touch);
        } else {
            self.held_controls.remove(control);
            self.suppressed.controls.remove(control);
        }
        self.resolve_matching(|b| matches!(b, Binding::Virtual(id) if id == control));
        if fresh {
            self.traced(|| TracedInput::Control(control.to_owned()));
        }
    }

    /// Feed an on-screen **stick**: where the control named by `control` is
    /// deflected to, with +X right and +Y up.
    ///
    /// A *level*, not a delta — a stick held still reports the same value every
    /// frame, and a stick nobody is touching reports `(0.0, 0.0)`. The magnitude
    /// belongs to the widget's own radius, so a control at its edge reports 1.0
    /// and the value is clamped to the unit disc when it is resolved.
    ///
    /// Non-finite coordinates are dropped like [`ActionMap::mouse_motion`]'s
    /// deltas: a `NaN` would poison every comparison downstream of the axis.
    pub fn virtual_stick(&mut self, control: &str, x: f32, y: f32) {
        if !x.is_finite() || !y.is_finite() {
            return;
        }
        let deflected = x != 0.0 || y != 0.0;
        if deflected {
            self.spoke(Device::Touch);
        }
        let before = if let Some(held) = self.control_sticks.get_mut(control) {
            std::mem::replace(held, (x, y))
        } else {
            self.control_sticks.insert(control.to_owned(), (x, y));
            (0.0, 0.0)
        };
        // Centred is a stick's release: what lifts a suppress.
        if !deflected {
            self.suppressed.control_sticks.remove(control);
        }
        self.resolve_matching(|b| matches!(b, Binding::Virtual(id) if id == control));
        if deflected && before == (0.0, 0.0) {
            self.traced(|| TracedInput::ControlStick(control.to_owned()));
        }
    }

    /// Called at the start of each server tick.
    ///
    /// - Resets per-frame edge flags (`just_pressed`, `just_released` on every
    ///   button action, `pointer_moved` on every 1-D axis, what
    ///   [`ActionMap::repeated`], [`ActionMap::tapped`],
    ///   [`ActionMap::hold_fired`] and [`ActionMap::double_tapped`] read, and
    ///   [`ActionMap::last_device_changed`]).
    /// - Zeroes accumulated mouse-motion and scroll deltas.
    /// - Releases every action a pattern emitted since the last tick, and
    ///   presses the ones a pattern emits as this tick begins — see `emit.rs`.
    /// - Advances the internal clock by `dt` seconds so that [`ButtonState::Held`]
    ///   durations are up-to-date next time a button action is resolved.
    pub fn begin_tick(&mut self, dt: f32) {
        // A negative dt would move the clock backwards and report negative
        // `Held` durations; only forward time is meaningful here.
        if dt.is_finite() && dt >= 0.0 {
            self.elapsed += f64::from(dt);
        }
        self.mouse_delta = (0.0, 0.0);
        self.scroll_delta = (0.0, 0.0);
        self.device_changed = false;
        // Every slot, live or not: one taken off the stack while pressed must
        // not come back pressed.
        for slot in &mut self.slots {
            slot.emitted = false;
        }

        // Reset edge flags and re-resolve every action so that Held durations
        // and axis values reflect the new elapsed time and cleared deltas.
        //
        // Disabled actions are skipped entirely. Resolving them here re-read
        // `held_keys` and re-pressed them — so disabling "jump" while Space was
        // held cleared it, and the next tick emitted `just_pressed` again.
        for i in 0..self.slots.len() {
            if !self.is_live(i) {
                continue;
            }
            if let Some(repeat) = &mut self.slots[i].repeat {
                repeat.fired = false;
            }
            self.slots[i].patterns.clear_fired();
            match &mut self.slots[i].value {
                ActionValue::Button(a) => a.reset_edges(),
                ActionValue::Axis1(a) => a.pointer_moved = false,
                ActionValue::Axis2(_) => {}
            }
            // Re-resolve to update Held duration and zero out axis deltas.
            // Not `resolve_one`: what a pattern emits now waits for the loop
            // to finish, so the edges do not depend on declaration order.
            self.resolve_slot(i);
        }
        self.drain_emits();
    }

    // -- reading resolved state ----------------------------------------------

    /// Get the current value of an action by name.
    ///
    /// Returns `None` if no action with that name was declared.
    #[must_use]
    pub fn action(&self, name: &str) -> Option<&ActionValue> {
        let &idx = self.name_to_idx.get(name)?;
        Some(&self.slots[idx].value)
    }

    /// Get a mutable reference to the current value of an action.
    ///
    /// The caller can use this to clear edge flags after consuming them
    /// (e.g. setting `just_pressed = false` after a jump was processed).
    #[must_use]
    pub fn action_mut(&mut self, name: &str) -> Option<&mut ActionValue> {
        let &idx = self.name_to_idx.get(name)?;
        Some(&mut self.slots[idx].value)
    }

    /// All declared action names, in registration order.
    pub fn action_names(&self) -> impl Iterator<Item = &str> {
        self.slots.iter().map(|s| s.decl.name.as_str())
    }

    /// Whether a button action is down — pressed this tick or still held.
    ///
    /// An action that was never declared, or that is not a button, is `false`
    /// rather than an error: a caller asking whether a button is down has no
    /// better answer to give, and every game was already collapsing both cases
    /// that way.
    ///
    /// The state is matched positively rather than as "not
    /// [`Released`](ButtonState::Released)". The two agree while
    /// [`ButtonState`] has three variants, and would stop agreeing the day it
    /// gains a fourth — silently, and only for whoever wrote the negation.
    #[must_use]
    pub fn button_held(&self, name: &str) -> bool {
        self.button(name).is_some_and(|button| {
            matches!(
                button.state,
                ButtonState::Pressed | ButtonState::Held { .. }
            )
        })
    }

    /// Whether a button action went down on this tick.
    ///
    /// The edge, not the level: true only for the tick of the transition, and
    /// cleared by [`ActionMap::begin_tick`]. This is what a jump or a flap
    /// reads, so that holding the key does not repeat it.
    #[must_use]
    pub fn just_pressed(&self, name: &str) -> bool {
        self.button(name).is_some_and(|button| button.just_pressed)
    }

    /// Whether a button action came up on this tick.
    #[must_use]
    pub fn just_released(&self, name: &str) -> bool {
        self.button(name).is_some_and(|button| button.just_released)
    }

    /// A 1-D axis action's value, or `0.0` if it is absent or another kind.
    #[must_use]
    pub fn axis1(&self, name: &str) -> f32 {
        match self.action(name) {
            Some(ActionValue::Axis1(axis)) => axis.value,
            _ => 0.0,
        }
    }

    /// A 2-D axis action's value, or `(0.0, 0.0)` if it is absent or another
    /// kind.
    ///
    /// Key-driven composites arrive normalised to at most unit length, so a
    /// diagonal is not faster than a cardinal; mouse motion is a raw pixel
    /// delta and is not normalised.
    #[must_use]
    pub fn axis2(&self, name: &str) -> (f32, f32) {
        match self.action(name) {
            Some(ActionValue::Axis2(axis)) => (axis.x, axis.y),
            _ => (0.0, 0.0),
        }
    }

    // -- reading raw input --------------------------------------------------

    /// Every key held down, in the order they were pressed — what an input
    /// inspector shows beside the actions they drive. Raw: a key no context
    /// binds, or one withheld, is listed as much as any other.
    #[must_use]
    pub fn held_keys(&self) -> Vec<KeyCode> {
        let mut held: Vec<(u64, KeyCode)> = self
            .held_keys
            .iter()
            .map(|(&key, &serial)| (serial, key))
            .collect();
        held.sort_unstable();
        held.into_iter().map(|(_, key)| key).collect()
    }

    /// Every pointer button held down, in [`PointerButton`]'s order. Raw, as
    /// [`ActionMap::held_keys`] is.
    #[must_use]
    pub fn held_mouse_buttons(&self) -> Vec<PointerButton> {
        let mut held: Vec<PointerButton> = self.held_buttons.iter().copied().collect();
        held.sort_unstable();
        held
    }

    /// Where the pointer last was, normalised to the surface as
    /// [`ActionMap::pointer_position`] takes it, or `None` before it reported
    /// a position.
    #[must_use]
    pub const fn pointer(&self) -> Option<(f32, f32)> {
        self.pointer
    }

    /// The button behind `name`, if it is declared and is one.
    fn button(&self, name: &str) -> Option<&ButtonAction> {
        match self.action(name)? {
            ActionValue::Button(button) => Some(button),
            _ => None,
        }
    }

    // -- internal resolution -------------------------------------------------

    /// Re-resolve every enabled action with a binding `matches` accepts.
    ///
    /// One helper rather than four near-identical bodies, and no `Vec<usize>`
    /// per event: the enabled flag lives on the slot, so nothing here allocates
    /// or hashes a `String`.
    fn resolve_matching(&mut self, matches: impl Fn(&Binding) -> bool) {
        for i in 0..self.slots.len() {
            let slot = &self.slots[i];
            if self.is_live(i) && slot.decl.bindings.iter().any(&matches) {
                self.resolve_one(i);
            }
        }
    }

    /// Compute the current value of a single action slot from raw state, and
    /// press whatever its patterns emitted on the way.
    fn resolve_one(&mut self, idx: usize) {
        self.resolve_slot(idx);
        self.drain_emits();
    }

    /// Compute the current value of a single action slot from raw state,
    /// queueing what its patterns emit for [`ActionMap::drain_emits`].
    ///
    /// Reads raw input only through the slot's context's [`View`], which is
    /// where consumption happens.
    fn resolve_slot(&mut self, idx: usize) {
        let control_sticks = &self.control_sticks;
        let pads = &self.pads;
        let mouse_delta = self.mouse_delta;
        let scroll_delta = self.scroll_delta;
        let pointer = self.pointer;
        let elapsed = self.elapsed;

        let slot = &mut self.slots[idx];
        let view = View {
            context: slot.context,
            routes: &self.routes,
            suppressed: &self.suppressed,
            held_keys: &self.held_keys,
            held_buttons: &self.held_buttons,
            held_controls: &self.held_controls,
            held_pad_buttons: self.held_pad_buttons,
        };
        let kind = slot.kind();
        let bindings = &slot.decl.bindings;

        match kind {
            ActionKind::Button => {
                let down = slot.emitted
                    || bindings.iter().any(|b| match b {
                        Binding::Key(k) => view.key(*k),
                        Binding::Chord { modifier, key } => view.chord(*modifier, *key),
                        Binding::MouseButton(b) => view.button(*b),
                        Binding::ButtonChord { modifier, button } => {
                            view.button_chord(*modifier, *button)
                        }
                        Binding::Virtual(id) => view.control(id),
                        Binding::PadButton(button) => view.pad_button(*button),
                        Binding::PadChord { modifier, button } => {
                            view.pad_chord(*modifier, *button)
                        }
                        Binding::PadDpad => PadButton::DPAD.iter().any(|&b| view.pad_button(b)),
                        Binding::PadTrigger { trigger, threshold } => {
                            view.trigger(*trigger)
                                && gamepad::pad_trigger(pads, *trigger) > *threshold
                        }
                        Binding::MouseMotion
                        | Binding::MouseScroll
                        | Binding::ScrollChord { .. }
                        | Binding::PointerPosition { .. }
                        | Binding::PadStick { .. } => false,
                        Binding::KeyAxis { negative, positive } => {
                            view.key(*negative) || view.key(*positive)
                        }
                        Binding::Wasd {
                            up,
                            down: w_down,
                            left,
                            right,
                        } => {
                            view.key(*up)
                                || view.key(*w_down)
                                || view.key(*left)
                                || view.key(*right)
                        }
                    });

                let was_active = slot.active;
                slot.active = down;

                let action = match &mut slot.value {
                    ActionValue::Button(a) => a,
                    _ => unreachable!(),
                };

                match (was_active, down) {
                    (false, true) => {
                        action.state = ButtonState::Pressed;
                        action.just_pressed = true;
                        slot.hold_start = Some(elapsed);
                    }
                    (true, true) => {
                        let duration = (elapsed - slot.hold_start.unwrap_or(elapsed)) as f32;
                        action.state = ButtonState::Held { duration };
                    }
                    (true, false) => {
                        action.state = ButtonState::Released;
                        action.just_released = true;
                        slot.hold_start = None;
                    }
                    (false, false) => {
                        action.state = ButtonState::Released;
                    }
                }
            }
            ActionKind::Axis1 => {
                // The absolute source, if this action has one and a pointer has
                // ever reported a position. It **replaces** the relative
                // contributions below rather than adding to them: a place and a
                // rate do not sum. See [`Binding::PointerPosition`].
                let absolute = pointer.filter(|_| view.pointer()).and_then(|(px, py)| {
                    bindings.iter().find_map(|binding| match binding {
                        Binding::PointerPosition { axis } => Some(match axis {
                            PointerAxis::X => px,
                            PointerAxis::Y => py,
                        }),
                        _ => None,
                    })
                });

                let mut value: f32 = absolute.unwrap_or(0.0);

                if absolute.is_none() {
                    for binding in bindings {
                        match binding {
                            Binding::MouseScroll if view.scroll() => {
                                value += scroll_delta.1;
                            }
                            Binding::ScrollChord { held } if view.scroll_chord(*held) => {
                                value += scroll_delta.1;
                            }
                            Binding::Key(k) if view.key(*k) => {
                                value += 1.0;
                            }
                            Binding::Chord { modifier, key } if view.chord(*modifier, *key) => {
                                value += 1.0;
                            }
                            Binding::PadButton(button) if view.pad_button(*button) => {
                                value += 1.0;
                            }
                            Binding::PadChord { modifier, button }
                                if view.pad_chord(*modifier, *button) =>
                            {
                                value += 1.0;
                            }
                            Binding::PadTrigger { trigger, threshold }
                                if view.trigger(*trigger) =>
                            {
                                value += gamepad::trigger_past(
                                    gamepad::pad_trigger(pads, *trigger),
                                    *threshold,
                                );
                            }
                            Binding::KeyAxis { negative, positive } => {
                                if view.key(*negative) {
                                    value -= 1.0;
                                }
                                if view.key(*positive) {
                                    value += 1.0;
                                }
                            }
                            _ => {}
                        }
                    }
                }

                // The surface's edge is the axis's end, whatever the caller
                // passed: a coordinate outside it is a pointer outside the
                // window, not a stronger command.
                value = value.clamp(-1.0, 1.0);

                let action = match &mut slot.value {
                    ActionValue::Axis1(a) => a,
                    _ => unreachable!(),
                };
                action.value = value;
            }
            ActionKind::Axis2 => {
                // The *direction* sources and the pointer delta are accumulated
                // separately: a direction is bounded by the unit disc, so a
                // diagonal is a unit vector rather than 1.414 long and a stick
                // pushed past its own radius is still all the way over. A
                // pointer delta is a pixel count, and normalizing it would
                // throw away the speed.
                let mut dir_x: f32 = 0.0;
                let mut dir_y: f32 = 0.0;
                let mut x: f32 = 0.0;
                let mut y: f32 = 0.0;

                for binding in bindings {
                    match binding {
                        Binding::Wasd {
                            up,
                            down: w_down,
                            left,
                            right,
                        } => {
                            if view.key(*up) {
                                dir_y += 1.0;
                            }
                            if view.key(*w_down) {
                                dir_y -= 1.0;
                            }
                            if view.key(*left) {
                                dir_x -= 1.0;
                            }
                            if view.key(*right) {
                                dir_x += 1.0;
                            }
                        }
                        Binding::PadDpad => {
                            if view.pad_button(PadButton::DpadUp) {
                                dir_y += 1.0;
                            }
                            if view.pad_button(PadButton::DpadDown) {
                                dir_y -= 1.0;
                            }
                            if view.pad_button(PadButton::DpadLeft) {
                                dir_x -= 1.0;
                            }
                            if view.pad_button(PadButton::DpadRight) {
                                dir_x += 1.0;
                            }
                        }
                        // Into the same accumulator as the keys, so a player
                        // pushing a stick *and* holding a key asks for one
                        // direction rather than for twice the speed.
                        Binding::Virtual(id) if view.stick(id) => {
                            if let Some((sx, sy)) = control_sticks.get(id.as_str()) {
                                dir_x += sx;
                                dir_y += sy;
                            }
                        }
                        // Each pad through its own dead zone, then into the
                        // same accumulator as the keys.
                        Binding::PadStick { stick, deadzone } if view.pad_stick(*stick) => {
                            for pad in pads.values() {
                                let (sx, sy) =
                                    gamepad::radial_deadzone(pad.stick(*stick), *deadzone);
                                dir_x += sx;
                                dir_y += sy;
                            }
                        }
                        Binding::MouseMotion if view.motion() => {
                            x += mouse_delta.0;
                            y += mouse_delta.1;
                        }
                        _ => {}
                    }
                }

                let len = (dir_x * dir_x + dir_y * dir_y).sqrt();
                if len > 1.0 {
                    dir_x /= len;
                    dir_y /= len;
                }
                x += dir_x;
                y += dir_y;

                let action = match &mut slot.value {
                    ActionValue::Axis2(a) => a,
                    _ => unreachable!(),
                };
                action.x = x;
                action.y = y;
            }
        }

        if let Some(repeat) = &mut slot.repeat {
            repeat.update(&slot.value, elapsed);
        }
        let before = slot.patterns.fired();
        slot.patterns.update(&slot.value, elapsed);
        slot.patterns.queue_emits(before, &mut self.pending_emits);
    }
}

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

impl std::fmt::Debug for ActionMap {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ActionMap")
            .field(
                "actions",
                &self.slots.iter().map(|s| &s.decl.name).collect::<Vec<_>>(),
            )
            .field("held_keys", &self.held_keys.len())
            .field("held_buttons", &self.held_buttons.len())
            .field("held_controls", &self.held_controls)
            .field("control_sticks", &self.control_sticks)
            .field("pads", &self.pads)
            .field("contexts", &self.active_contexts().collect::<Vec<_>>())
            .field("devices", &self.devices)
            .field("last_pad_kind", &self.last_pad_kind)
            .field("pointer", &self.pointer)
            .field("elapsed", &self.elapsed)
            .finish_non_exhaustive()
    }
}

// ---------------------------------------------------------------------------
// InputTickState
// ---------------------------------------------------------------------------

/// The input state for one server tick.
///
/// The client builds one per tick with [`InputTickState::capture`], sends it to
/// the server, which applies it before running the tick.
#[derive(Debug, Clone, Default)]
pub struct InputTickState {
    /// Active actions and their values at this tick.
    pub actions: Vec<(String, ActionValue)>,
}

impl InputTickState {
    /// Create an empty tick state.
    #[must_use]
    pub fn new() -> Self {
        Self {
            actions: Vec::new(),
        }
    }

    /// Capture the current state of every declared action from `map`.
    ///
    /// This snapshots enabled and disabled actions alike; disabled actions will
    /// be in their idle state, and so are the actions of a context that is not
    /// on the stack. An action whose input a context above it consumed is
    /// captured as that input left it — which is exactly what the active
    /// contexts let through, and all the simulation should see.
    pub fn capture(map: &ActionMap) -> Self {
        let actions = map
            .slots
            .iter()
            .map(|slot| (slot.decl.name.clone(), slot.value.clone()))
            .collect();
        Self { actions }
    }

    /// Look up an action value by name.
    #[must_use]
    pub fn get(&self, name: &str) -> Option<&ActionValue> {
        self.actions.iter().find(|(n, _)| n == name).map(|(_, v)| v)
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

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

    // -- helpers ------------------------------------------------------------

    fn decl_button(name: &str, binding: Binding) -> ActionDecl {
        ActionDecl {
            name: name.to_owned(),
            kind: ActionKind::Button,
            bindings: vec![binding],
        }
    }

    fn decl_axis2_wasd(
        name: &str,
        up: KeyCode,
        down: KeyCode,
        left: KeyCode,
        right: KeyCode,
    ) -> ActionDecl {
        ActionDecl {
            name: name.to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![Binding::Wasd {
                up,
                down,
                left,
                right,
            }],
        }
    }

    fn decl_axis2_mouse(name: &str) -> ActionDecl {
        ActionDecl {
            name: name.to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![Binding::MouseMotion],
        }
    }

    fn decl_axis1_scroll(name: &str) -> ActionDecl {
        ActionDecl {
            name: name.to_owned(),
            kind: ActionKind::Axis1,
            bindings: vec![Binding::MouseScroll],
        }
    }

    // -- typed accessors ----------------------------------------------------

    /// One tick at sixty hertz, which is what `begin_tick` wants — a delta,
    /// not a timestamp.
    const TICK: f32 = 1.0 / 60.0;

    /// Held is down, and so is the tick the key went down on.
    ///
    /// Both, not just the second: a game reading "is the thrust on" during the
    /// very tick the key arrived would otherwise see it off for one tick and
    /// stutter.
    #[test]
    fn a_button_is_held_while_it_is_down_and_not_after() {
        let mut map = ActionMap::new();
        map.declare(decl_button("thrust", Binding::Key(KeyCode::KeyW)));

        assert!(!map.button_held("thrust"), "nothing is down yet");

        map.begin_tick(TICK);
        map.key_event(KeyCode::KeyW, true);
        assert!(map.button_held("thrust"), "the tick the key arrives counts");

        map.begin_tick(TICK);
        assert!(
            matches!(
                map.action("thrust"),
                Some(ActionValue::Button(ButtonAction {
                    state: ButtonState::Held { .. },
                    ..
                }))
            ),
            "a second tick with the key still down is Held, which is the other \
             state that must read as down"
        );
        assert!(map.button_held("thrust"));

        map.key_event(KeyCode::KeyW, false);
        assert!(!map.button_held("thrust"), "released is not down");
    }

    /// The edges are one tick wide, and they are not the level.
    #[test]
    fn the_edges_fire_once_each() {
        let mut map = ActionMap::new();
        map.declare(decl_button("flap", Binding::Key(KeyCode::Space)));

        map.begin_tick(TICK);
        map.key_event(KeyCode::Space, true);
        assert!(map.just_pressed("flap"));
        assert!(!map.just_released("flap"));

        map.begin_tick(TICK);
        assert!(
            !map.just_pressed("flap"),
            "holding the key does not press it again — this is the whole \
             reason a flap reads the edge and not the level"
        );
        assert!(map.button_held("flap"), "still down, though");

        map.key_event(KeyCode::Space, false);
        assert!(map.just_released("flap"));
        map.begin_tick(TICK);
        assert!(
            !map.just_released("flap"),
            "the release edge is one tick too"
        );
    }

    /// An axis answers with its value, and a composite is not longer than one.
    #[test]
    fn the_axis_accessors_read_the_value() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));
        map.declare(decl_axis1_scroll("zoom"));

        assert_eq!(map.axis2("move"), (0.0, 0.0));
        assert_eq!(map.axis1("zoom"), 0.0);

        map.begin_tick(TICK);
        map.key_event(KeyCode::KeyD, true);
        let (x, y) = map.axis2("move");
        assert!((x - 1.0).abs() < 1e-6, "right alone is +1 on x, got {x}");
        assert!(y.abs() < 1e-6, "and nothing on y, got {y}");

        map.key_event(KeyCode::KeyW, true);
        let (x, y) = map.axis2("move");
        let length = x.hypot(y);
        assert!(
            (length - 1.0).abs() < 1e-6,
            "a diagonal is normalised, or it is 41% faster than a cardinal: \
             got length {length}"
        );

        map.mouse_scroll(0.0, 3.0);
        assert_ne!(map.axis1("zoom"), 0.0, "the scroll reached the axis");
    }

    /// Asking the wrong kind, or a name nobody declared, is the idle value.
    ///
    /// Every game collapsed both cases this way already. Worth pinning because
    /// the alternative — a panic, or `true` — would turn a typo into a stuck
    /// input rather than a dead one.
    #[test]
    fn the_wrong_kind_and_the_wrong_name_are_idle() {
        let mut map = ActionMap::new();
        map.declare(decl_button("fire", Binding::Key(KeyCode::Space)));
        map.declare(decl_axis1_scroll("zoom"));

        map.begin_tick(TICK);
        map.key_event(KeyCode::Space, true);

        assert!(!map.button_held("zoom"), "an axis is not a held button");
        assert!(!map.just_pressed("zoom"));
        assert!(!map.just_released("zoom"));
        assert_eq!(map.axis1("fire"), 0.0, "a button is not an axis");
        assert_eq!(map.axis2("fire"), (0.0, 0.0));

        assert!(!map.button_held("nonesuch"));
        assert!(!map.just_pressed("nonesuch"));
        assert_eq!(map.axis1("nonesuch"), 0.0);
        assert_eq!(map.axis2("nonesuch"), (0.0, 0.0));
    }

    // -- ButtonState / ButtonAction -----------------------------------------

    #[test]
    fn button_action_default_is_released() {
        let a = ButtonAction::default();
        assert!(matches!(a.state, ButtonState::Released));
        assert!(!a.just_pressed);
        assert!(!a.just_released);
    }

    #[test]
    fn reset_edges_clears_flags() {
        let mut a = ButtonAction {
            state: ButtonState::Pressed,
            just_pressed: true,
            just_released: true,
        };
        a.reset_edges();
        assert!(!a.just_pressed);
        assert!(!a.just_released);
        // state is untouched by reset_edges.
        assert!(matches!(a.state, ButtonState::Pressed));
    }

    // -- ActionMap: key binding ---------------------------------------------

    #[test]
    fn key_press_and_release() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));

        // Initially released.
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                just_pressed: false,
                just_released: false,
            })
        ));

        // Press space.
        map.key_event(KeyCode::Space, true);
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                just_released: false,
            })
        ));

        // Next tick: edges cleared, still held → Held { duration }.
        map.begin_tick(1.0 / 60.0);
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Held { .. },
                just_pressed: false,
                just_released: false,
            })
        ));

        // Release space.
        map.key_event(KeyCode::Space, false);
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                just_pressed: false,
                just_released: true,
            })
        ));
    }

    #[test]
    fn a_key_still_down_after_a_tick_reports_held_with_how_long_it_has_been() {
        let mut map = ActionMap::new();
        map.declare(decl_button("fire", Binding::Key(KeyCode::KeyF)));

        map.key_event(KeyCode::KeyF, true);
        // Advance 2 seconds.
        map.begin_tick(2.0);

        let v = map.action("fire").unwrap();
        if let ActionValue::Button(a) = v {
            if let ButtonState::Held { duration } = a.state {
                assert!(
                    (duration - 2.0).abs() < 0.001,
                    "expected ~2s, got {duration}"
                );
            } else {
                panic!("expected Held, got {:?}", a.state);
            }
        } else {
            panic!("expected Button, got {:?}", v);
        }
    }

    // -- ActionMap: mouse-button binding ------------------------------------

    #[test]
    fn mouse_button_press_and_release() {
        let mut map = ActionMap::new();
        map.declare(decl_button(
            "shoot",
            Binding::MouseButton(PointerButton::Left),
        ));

        map.mouse_button(PointerButton::Left, true);
        let v = map.action("shoot").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                just_released: false,
            })
        ));

        map.begin_tick(0.016);
        map.mouse_button(PointerButton::Left, false);
        let v = map.action("shoot").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                just_pressed: false,
                just_released: true,
            })
        ));
    }

    // -- ActionMap: WASD composite -------------------------------------------

    #[test]
    fn a_wasd_composite_stays_a_unit_vector_from_idle_through_every_diagonal() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));

        // Idle.
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, 0.0, 0.0);

        // Press W → (0, 1).
        map.key_event(KeyCode::KeyW, true);
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, 0.0, 1.0);

        // Press D as well → a *unit* diagonal, not (1, 1).
        map.key_event(KeyCode::KeyD, true);
        let v = map.action("move").unwrap();
        let diag = std::f32::consts::FRAC_1_SQRT_2;
        assert_eq_axis2(v, diag, diag);

        // Release W and D, then press S and A → the opposite unit diagonal.
        map.key_event(KeyCode::KeyW, false);
        map.key_event(KeyCode::KeyD, false);
        map.key_event(KeyCode::KeyA, true);
        map.key_event(KeyCode::KeyS, true);
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, -diag, -diag);

        // Release all.
        map.key_event(KeyCode::KeyD, false);
        map.key_event(KeyCode::KeyA, false);
        map.key_event(KeyCode::KeyS, false);
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, 0.0, 0.0);
    }

    #[test]
    fn wasd_opposing_keys_cancel() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));

        // W + S simultaneously → (0, 0).
        map.key_event(KeyCode::KeyW, true);
        map.key_event(KeyCode::KeyS, true);
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, 0.0, 0.0);

        // A + D simultaneously → (0, 0).
        map.key_event(KeyCode::KeyA, true);
        map.key_event(KeyCode::KeyD, true);
        let v = map.action("move").unwrap();
        assert_eq_axis2(v, 0.0, 0.0);
    }

    // -- ActionMap: mouse motion --------------------------------------------

    #[test]
    fn mouse_motion_accumulates_within_a_tick_and_begin_tick_clears_it() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_mouse("look"));

        // Accumulate delta over several events in one tick.
        map.mouse_motion(5.0, -3.0);
        map.mouse_motion(2.0, 1.0);
        let v = map.action("look").unwrap();
        assert_eq_axis2(v, 7.0, -2.0);

        // begin_tick resets deltas.
        map.begin_tick(0.016);
        let v = map.action("look").unwrap();
        assert_eq_axis2(v, 0.0, 0.0);
    }

    // -- ActionMap: mouse scroll --------------------------------------------

    #[test]
    fn scroll_sums_positive_and_negative_notches_and_resets_on_the_next_tick() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_scroll("zoom"));

        map.mouse_scroll(0.0, 1.0);
        let v = map.action("zoom").unwrap();
        assert_eq_axis1(v, 1.0);

        map.mouse_scroll(0.0, -0.5);
        let v = map.action("zoom").unwrap();
        assert_eq_axis1(v, 0.5);

        // begin_tick resets.
        map.begin_tick(0.016);
        let v = map.action("zoom").unwrap();
        assert_eq_axis1(v, 0.0);
    }

    #[test]
    fn scroll_clamped_to_range() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_scroll("zoom"));

        map.mouse_scroll(0.0, 5.0);
        let v = map.action("zoom").unwrap();
        assert_eq_axis1(v, 1.0);

        map.begin_tick(0.016);
        map.mouse_scroll(0.0, -5.0);
        let v = map.action("zoom").unwrap();
        assert_eq_axis1(v, -1.0);
    }

    // -- ActionMap: absolute pointer position --------------------------------

    fn decl_axis1_pointer(name: &str, axis: PointerAxis) -> ActionDecl {
        ActionDecl {
            name: name.to_owned(),
            kind: ActionKind::Axis1,
            bindings: vec![Binding::PointerPosition { axis }],
        }
    }

    /// **Each axis reads its own coordinate, at the value it was given.**
    ///
    /// Two actions on one map and asymmetric coordinates, because that is what
    /// a swapped axis fails: a pointer at `(0.5, 0.5)` puts the right answer on
    /// both of them.
    #[test]
    fn a_pointer_position_lands_on_the_axis_it_is_bound_to() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_pointer("aim_x", PointerAxis::X));
        map.declare(decl_axis1_pointer("aim_y", PointerAxis::Y));

        assert_eq!(
            map.axis1("aim_x"),
            0.0,
            "an axis nothing has pointed at yet is idle, not at the left edge",
        );

        map.begin_tick(TICK);
        map.pointer_position(-0.75, 0.25);

        assert_eq_axis1(map.action("aim_x").unwrap(), -0.75);
        assert_eq_axis1(map.action("aim_y").unwrap(), 0.25);
    }

    /// **The position is a level: it survives ticks, unlike a scroll delta.**
    ///
    /// This is also what "a pointer that leaves keeps its last position" means
    /// mechanically — leaving reports no coordinate, so nothing here is fed and
    /// the axis is exactly where the last real position put it.
    #[test]
    fn an_absolute_axis_holds_its_position_across_ticks() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_pointer("aim", PointerAxis::X));
        map.declare(decl_axis1_scroll("zoom"));

        map.begin_tick(TICK);
        map.pointer_position(0.6, 0.0);
        map.mouse_scroll(0.0, 1.0);
        assert_eq_axis1(map.action("aim").unwrap(), 0.6);
        assert_eq_axis1(map.action("zoom").unwrap(), 1.0);

        map.begin_tick(TICK);
        assert_eq_axis1(map.action("zoom").unwrap(), 0.0);
        assert_eq_axis1(map.action("aim").unwrap(), 0.6);
    }

    /// **`pointer_moved` is an edge, and it is about the pointer moving.**
    ///
    /// A tick that re-sends the coordinate the axis already holds raises
    /// nothing: a consumer arbitrating between the pointer and the keyboard
    /// reads this as "the player just asked for this", and a browser that
    /// re-reports a resting cursor would otherwise hold the keyboard off
    /// forever.
    #[test]
    fn the_pointer_edge_is_one_tick_wide_and_only_for_a_new_position() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_pointer("aim", PointerAxis::X));

        let moved = |map: &ActionMap| match map.action("aim") {
            Some(ActionValue::Axis1(axis)) => axis.pointer_moved,
            other => panic!("expected Axis1, got {other:?}"),
        };

        map.begin_tick(TICK);
        assert!(!moved(&map), "nothing has pointed anywhere yet");
        map.pointer_position(0.2, 0.0);
        assert!(moved(&map), "the pointer moved on this tick");

        map.begin_tick(TICK);
        assert!(!moved(&map), "the edge is one tick wide");
        assert_eq_axis1(map.action("aim").unwrap(), 0.2);

        map.pointer_position(0.2, 0.0);
        assert!(
            !moved(&map),
            "the same coordinate again is not the player asking for anything",
        );
        map.pointer_position(0.2, 0.9);
        assert!(
            moved(&map),
            "the other coordinate changing is still the pointer moving",
        );
    }

    /// **An absolute source replaces the relative ones on the same axis.**
    ///
    /// Summing them would add a place to a rate. The keyboard drives the axis
    /// while no pointer has ever reported a position, and stops the moment one
    /// has — which is the documented reason a game whose keys mean something
    /// *different* from its pointer declares two actions instead of one.
    #[test]
    fn an_absolute_binding_replaces_the_relative_ones_on_the_same_axis() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "slide".to_owned(),
            kind: ActionKind::Axis1,
            bindings: vec![
                Binding::KeyAxis {
                    negative: KeyCode::ArrowLeft,
                    positive: KeyCode::ArrowRight,
                },
                Binding::PointerPosition {
                    axis: PointerAxis::X,
                },
            ],
        });

        map.begin_tick(TICK);
        map.key_event(KeyCode::ArrowRight, true);
        assert_eq_axis1(map.action("slide").unwrap(), 1.0);

        map.pointer_position(-0.5, 0.0);
        assert_eq_axis1(map.action("slide").unwrap(), -0.5);
    }

    /// **The surface's edge is the end of the axis.**
    #[test]
    fn a_pointer_outside_the_surface_is_clamped_to_its_edge() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_pointer("aim", PointerAxis::X));

        map.pointer_position(4.0, 0.0);
        assert_eq_axis1(map.action("aim").unwrap(), 1.0);

        map.pointer_position(-4.0, 0.0);
        assert_eq_axis1(map.action("aim").unwrap(), -1.0);
    }

    /// **A pointer binding joins the keys on a button, it does not replace
    /// them.**
    ///
    /// The flap that a phone taps and a keyboard presses is one action with
    /// both bindings on it, and each still fires on its own. A binding list
    /// that had been overwritten rather than appended to passes every test that
    /// only ever presses the pointer.
    #[test]
    fn a_pointer_button_joins_the_keys_bound_to_the_same_action() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "flap".to_owned(),
            kind: ActionKind::Button,
            bindings: vec![
                Binding::Key(KeyCode::Space),
                Binding::MouseButton(PointerButton::Left),
            ],
        });

        map.begin_tick(TICK);
        map.key_event(KeyCode::Space, true);
        assert!(map.just_pressed("flap"), "the key still flaps");
        map.key_event(KeyCode::Space, false);

        map.begin_tick(TICK);
        map.mouse_button(PointerButton::Left, true);
        assert!(map.just_pressed("flap"), "and so does the tap");
        map.mouse_button(PointerButton::Left, false);
        assert!(map.just_released("flap"));
    }

    // -- begin_tick resets edges and deltas ----------------------------------

    #[test]
    fn begin_tick_resets_just_pressed_and_just_released() {
        let mut map = ActionMap::new();
        map.declare(decl_button("a", Binding::Key(KeyCode::KeyA)));

        map.key_event(KeyCode::KeyA, true);
        assert!(matches!(
            map.action("a").unwrap(),
            ActionValue::Button(ButtonAction {
                just_pressed: true,
                ..
            })
        ));

        map.begin_tick(0.016);
        assert!(matches!(
            map.action("a").unwrap(),
            ActionValue::Button(ButtonAction {
                just_pressed: false,
                just_released: false,
                ..
            })
        ));

        map.key_event(KeyCode::KeyA, false);
        assert!(matches!(
            map.action("a").unwrap(),
            ActionValue::Button(ButtonAction {
                just_released: true,
                ..
            })
        ));

        map.begin_tick(0.016);
        assert!(matches!(
            map.action("a").unwrap(),
            ActionValue::Button(ButtonAction {
                just_released: false,
                ..
            })
        ));
    }

    // -- enable / disable ---------------------------------------------------

    #[test]
    fn disabled_action_returns_idle() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));

        map.key_event(KeyCode::Space, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));

        map.set_enabled("jump", false);
        // Disabled → Released and edges cleared.
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                just_pressed: false,
                just_released: false,
            })
        ));

        // Re-enable: key is still held, so it becomes pressed again.
        map.set_enabled("jump", true);
        map.key_event(KeyCode::Space, true); // need to re-trigger resolution
        let v = map.action("jump").unwrap();
        assert!(matches!(
            v,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                ..
            })
        ));
    }

    #[test]
    fn disabled_wasd_returns_zero() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));
        map.key_event(KeyCode::KeyW, true);
        assert_eq_axis2(map.action("move").unwrap(), 0.0, 1.0);

        map.set_enabled("move", false);
        assert_eq_axis2(map.action("move").unwrap(), 0.0, 0.0);

        // …and it must stay zero across ticks. `begin_tick` used to re-resolve
        // every slot with no enabled check, so the still-held W came straight
        // back on the next tick.
        for tick in 0..3 {
            map.begin_tick(1.0 / 60.0);
            assert_eq_axis2(map.action("move").unwrap(), 0.0, 0.0);
            assert!(tick < 3);
        }
    }

    /// The same bug for a Button action: disabling "jump" while Space is held
    /// cleared it, and the very next `begin_tick` re-emitted
    /// `state: Pressed, just_pressed: true` — a menu opened with gameplay
    /// disabled still jumped.
    #[test]
    fn a_disabled_button_does_not_re_press_itself_on_the_next_tick() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));

        map.key_event(KeyCode::Space, true);
        map.set_enabled("jump", false);

        for _ in 0..3 {
            map.begin_tick(1.0 / 60.0);
            let v = map.action("jump").unwrap();
            assert!(
                matches!(
                    v,
                    ActionValue::Button(ButtonAction {
                        state: ButtonState::Released,
                        just_pressed: false,
                        just_released: false,
                    })
                ),
                "a disabled action fired anyway: {v:?}"
            );
        }

        // Re-enabling with the key still held presses it again, which is the
        // intended behaviour.
        map.set_enabled("jump", true);
        map.begin_tick(1.0 / 60.0);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                ..
            })
        ));
    }

    /// `set_enabled` on a name that was never declared used to insert into a
    /// `HashSet<String>` that nothing ever pruned.
    #[test]
    fn set_enabled_on_an_unknown_action_is_a_no_op() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        map.set_enabled("typo-in-the-profile", true);
        map.set_enabled("typo-in-the-profile", false);
        assert_eq!(map.is_enabled("typo-in-the-profile"), None);
        assert_eq!(map.is_enabled("jump"), Some(true));
        assert_eq!(map.action_names().count(), 1);
    }

    // -- declare / rebind ---------------------------------------------------

    #[test]
    fn try_declare_reports_a_duplicate_rather_than_aborting() {
        let mut map = ActionMap::new();
        assert!(
            map.try_declare(decl_button("jump", Binding::Key(KeyCode::Space)))
                .is_ok()
        );
        assert_eq!(
            map.try_declare(decl_button("jump", Binding::Key(KeyCode::KeyJ))),
            Err(ActionMapError::DuplicateName("jump".to_owned()))
        );
        // The first declaration is untouched.
        assert_eq!(
            map.bindings("jump"),
            Some(&[Binding::Key(KeyCode::Space)][..])
        );
    }

    #[test]
    fn rebind_replaces_bindings_and_keeps_the_enabled_flag() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        map.set_enabled("jump", false);

        map.rebind("jump", vec![Binding::Key(KeyCode::KeyJ)])
            .expect("declared");
        assert_eq!(
            map.bindings("jump"),
            Some(&[Binding::Key(KeyCode::KeyJ)][..])
        );
        assert_eq!(
            map.is_enabled("jump"),
            Some(false),
            "the rebind must not silently re-enable the action"
        );

        map.set_enabled("jump", true);
        map.key_event(KeyCode::KeyJ, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));
        // The old key no longer does anything.
        map.begin_tick(0.016);
        map.key_event(KeyCode::KeyJ, false);
        map.begin_tick(0.016);
        map.key_event(KeyCode::Space, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                ..
            })
        ));
    }

    #[test]
    fn rebind_an_unknown_action_errors() {
        let mut map = ActionMap::new();
        assert_eq!(
            map.rebind("nope", vec![]),
            Err(ActionMapError::UnknownAction("nope".to_owned()))
        );
    }

    /// A rebind while the new key is already held resolves immediately.
    #[test]
    fn rebind_resolves_against_the_current_held_keys() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        map.key_event(KeyCode::KeyJ, true);
        map.rebind("jump", vec![Binding::Key(KeyCode::KeyJ)])
            .expect("declared");
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                ..
            })
        ));
    }

    // -- Axis1 key pairs ----------------------------------------------------

    /// A single `Key` binding can only ever add +1.0, so a keyboard axis could
    /// not go negative at all.
    #[test]
    fn key_axis_reaches_both_ends_of_the_range() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "throttle".into(),
            kind: ActionKind::Axis1,
            bindings: vec![Binding::KeyAxis {
                negative: KeyCode::KeyS,
                positive: KeyCode::KeyW,
            }],
        });

        assert_eq_axis1(map.action("throttle").unwrap(), 0.0);

        map.key_event(KeyCode::KeyW, true);
        assert_eq_axis1(map.action("throttle").unwrap(), 1.0);

        // Both held → cancel.
        map.key_event(KeyCode::KeyS, true);
        assert_eq_axis1(map.action("throttle").unwrap(), 0.0);

        map.key_event(KeyCode::KeyW, false);
        assert_eq_axis1(map.action("throttle").unwrap(), -1.0);
    }

    /// A `KeyAxis` on a `Button` action is "either key is down".
    #[test]
    fn key_axis_drives_a_button_from_either_key() {
        let mut map = ActionMap::new();
        map.declare(decl_button(
            "any",
            Binding::KeyAxis {
                negative: KeyCode::KeyS,
                positive: KeyCode::KeyW,
            },
        ));
        map.key_event(KeyCode::KeyS, true);
        assert!(matches!(
            map.action("any").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));
    }

    // -- non-finite input ---------------------------------------------------

    /// `mouse_motion(NAN, 1.0)` used to write `Axis2 { x: NaN, y: 1.0 }`
    /// straight through, and `f32::clamp` returns `NaN` for a `NaN` scroll, so
    /// the clamp downstream was no defence either.
    #[test]
    fn non_finite_deltas_are_dropped_at_the_ingest_boundary() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_mouse("look"));
        map.declare(decl_axis1_scroll("zoom"));

        for bad in [f32::NAN, f32::INFINITY, f32::NEG_INFINITY] {
            map.mouse_motion(bad, 1.0);
            map.mouse_motion(1.0, bad);
            map.mouse_scroll(0.0, bad);
        }

        match map.action("look").unwrap() {
            ActionValue::Axis2(a) => assert!(
                a.x.is_finite() && a.y.is_finite(),
                "look went non-finite: {a:?}"
            ),
            other => panic!("expected Axis2, got {other:?}"),
        }
        match map.action("zoom").unwrap() {
            ActionValue::Axis1(a) => {
                assert!(a.value.is_finite(), "zoom went non-finite: {a:?}");
            }
            other => panic!("expected Axis1, got {other:?}"),
        }

        // Good deltas still land.
        map.begin_tick(0.016);
        map.mouse_motion(3.0, -4.0);
        assert_eq_axis2(map.action("look").unwrap(), 3.0, -4.0);
    }

    /// A non-finite pointer coordinate must not become the axis a paddle is
    /// positioned from — and must not evict the last good position either.
    #[test]
    fn a_non_finite_pointer_position_is_dropped_and_the_last_one_survives() {
        let mut map = ActionMap::new();
        map.declare(decl_axis1_pointer("aim", PointerAxis::X));

        map.pointer_position(0.4, 0.0);
        for bad in [f32::NAN, f32::INFINITY, f32::NEG_INFINITY] {
            map.pointer_position(bad, 0.0);
            map.pointer_position(0.0, bad);
        }

        assert_eq_axis1(map.action("aim").unwrap(), 0.4);
    }

    /// A non-finite `dt` must not poison the clock every `Held` duration is
    /// measured against.
    #[test]
    fn a_non_finite_dt_does_not_poison_hold_durations() {
        let mut map = ActionMap::new();
        map.declare(decl_button("fire", Binding::Key(KeyCode::KeyF)));
        map.key_event(KeyCode::KeyF, true);
        map.begin_tick(f32::NAN);
        map.begin_tick(2.0);

        let ActionValue::Button(a) = map.action("fire").unwrap() else {
            panic!("expected Button");
        };
        let ButtonState::Held { duration } = a.state else {
            panic!("expected Held, got {:?}", a.state);
        };
        assert!((duration - 2.0).abs() < 0.001, "got {duration}");
    }

    /// A negative `dt` used to move the clock backwards, so a key held across
    /// it reported a negative `Held` duration — and the lost time then made the
    /// next tick measure the hold as though it had never been held.
    #[test]
    fn a_negative_dt_does_not_report_a_negative_hold_duration() {
        let mut map = ActionMap::new();
        map.declare(decl_button("fire", Binding::Key(KeyCode::KeyF)));
        map.key_event(KeyCode::KeyF, true);

        map.begin_tick(-1.0);
        let ActionValue::Button(a) = map.action("fire").unwrap() else {
            panic!("expected Button");
        };
        let ButtonState::Held { duration } = a.state else {
            panic!("expected Held, got {:?}", a.state);
        };
        assert!(
            duration >= 0.0,
            "a negative dt must not report a negative hold duration, got {duration}"
        );

        // The negative tick was dropped rather than absorbed: a real 1s tick
        // measures a full second, not the second minus the backwards one.
        map.begin_tick(1.0);
        let ActionValue::Button(a) = map.action("fire").unwrap() else {
            panic!("expected Button");
        };
        let ButtonState::Held { duration } = a.state else {
            panic!("expected Held, got {:?}", a.state);
        };
        assert!(
            (duration - 1.0).abs() < 0.001,
            "with the negative tick dropped the hold measures normally, got {duration}"
        );
    }

    // -- action_mut ---------------------------------------------------------

    #[test]
    fn action_mut_lets_caller_clear_edges() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));

        map.key_event(KeyCode::Space, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                just_pressed: true,
                ..
            })
        ));

        // Consume the edge mid-tick.
        if let Some(ActionValue::Button(a)) = map.action_mut("jump") {
            a.just_pressed = false;
        }

        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                just_pressed: false,
                ..
            })
        ));
    }

    // -- multiple bindings per action ---------------------------------------

    #[test]
    fn multiple_bindings_any_triggers() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "jump".into(),
            kind: ActionKind::Button,
            bindings: vec![
                Binding::Key(KeyCode::Space),
                Binding::MouseButton(PointerButton::Left),
            ],
        });

        // Either binding triggers.
        map.key_event(KeyCode::Space, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));

        map.begin_tick(0.016);
        map.key_event(KeyCode::Space, false);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                ..
            })
        ));

        map.begin_tick(0.016);
        map.mouse_button(PointerButton::Left, true);
        assert!(matches!(
            map.action("jump").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));
    }

    #[test]
    fn multiple_bindings_stays_held_until_all_released() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "crouch".into(),
            kind: ActionKind::Button,
            bindings: vec![
                Binding::Key(KeyCode::ControlLeft),
                Binding::Key(KeyCode::KeyC),
            ],
        });

        map.key_event(KeyCode::ControlLeft, true);
        assert!(matches!(
            map.action("crouch").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                ..
            })
        ));

        map.begin_tick(0.016);
        map.key_event(KeyCode::KeyC, true);
        // Still held (via ControlLeft).
        assert!(matches!(
            map.action("crouch").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Held { .. },
                ..
            })
        ));

        // Release one, still held via the other.
        map.key_event(KeyCode::ControlLeft, false);
        assert!(matches!(
            map.action("crouch").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Held { .. },
                ..
            })
        ));

        // Release both → released.
        map.key_event(KeyCode::KeyC, false);
        assert!(matches!(
            map.action("crouch").unwrap(),
            ActionValue::Button(ButtonAction {
                state: ButtonState::Released,
                just_released: true,
                ..
            })
        ));
    }

    // -- action_names -------------------------------------------------------

    #[test]
    fn action_names_returns_in_order() {
        let mut map = ActionMap::new();
        map.declare(decl_button("a", Binding::Key(KeyCode::KeyA)));
        map.declare(decl_button("b", Binding::Key(KeyCode::KeyB)));
        map.declare(decl_button("c", Binding::Key(KeyCode::KeyC)));

        let names: Vec<&str> = map.action_names().collect();
        assert_eq!(names, vec!["a", "b", "c"]);
    }

    // -- InputTickState -----------------------------------------------------

    #[test]
    fn tick_state_capture_and_get() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));

        map.key_event(KeyCode::Space, true);
        map.key_event(KeyCode::KeyW, true);

        let tick = InputTickState::capture(&map);
        assert_eq!(tick.actions.len(), 2);

        // jump should be pressed.
        let jump = tick.get("jump").unwrap();
        assert!(matches!(
            jump,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                just_released: false,
            })
        ));

        // move should be (0, 1).
        let mv = tick.get("move").unwrap();
        assert_eq_axis2(mv, 0.0, 1.0);

        // Unknown name → None.
        assert!(tick.get("nope").is_none());
    }

    #[test]
    fn tick_state_new_is_empty() {
        let tick = InputTickState::new();
        assert!(tick.actions.is_empty());
        assert!(tick.get("anything").is_none());
    }

    // -- edge case: multiple actions with overlapping bindings ---------------

    #[test]
    fn two_actions_bound_to_one_key_both_report_pressed() {
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        map.declare(decl_button("fire", Binding::Key(KeyCode::Space)));

        map.key_event(KeyCode::Space, true);

        // Both should be pressed independently.
        let jump = map.action("jump").unwrap();
        let fire = map.action("fire").unwrap();
        assert!(matches!(
            jump,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                ..
            })
        ));
        assert!(matches!(
            fire,
            ActionValue::Button(ButtonAction {
                state: ButtonState::Pressed,
                just_pressed: true,
                ..
            })
        ));
    }

    // -- edge case: non-existent action -------------------------------------

    #[test]
    fn unknown_action_returns_none() {
        let mut map = ActionMap::new();
        assert!(map.action("nope").is_none());
        assert!(map.action_mut("nope").is_none());
    }

    // -- Debug implementations ----------------------------------------------

    #[test]
    fn every_input_type_debug_prints_without_panicking() {
        // Just make sure they don't panic.
        let mut map = ActionMap::new();
        map.declare(decl_button("jump", Binding::Key(KeyCode::Space)));
        let _ = format!("{map:?}");

        let tick = InputTickState::capture(&map);
        let _ = format!("{tick:?}");

        let _ = format!("{:?}", ButtonAction::default());
        let _ = format!("{:?}", ButtonState::Pressed);
        let _ = format!("{:?}", ActionKind::Button);
        let _ = format!(
            "{:?}",
            Binding::Wasd {
                up: KeyCode::KeyW,
                down: KeyCode::KeyS,
                left: KeyCode::KeyA,
                right: KeyCode::KeyD,
            }
        );
    }

    // -- Default impls ------------------------------------------------------

    #[test]
    fn axis_defaults_are_zero() {
        assert_eq!(
            Axis1Action::default(),
            Axis1Action {
                value: 0.0,
                pointer_moved: false,
            }
        );
        assert_eq!(Axis2Action::default(), Axis2Action { x: 0.0, y: 0.0 });
    }

    #[test]
    fn input_tick_state_default_is_empty() {
        let tick = InputTickState::default();
        assert!(tick.actions.is_empty());
    }

    // -- WASD with non-standard keys ----------------------------------------

    #[test]
    fn wasd_with_arrow_keys() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::ArrowUp,
            KeyCode::ArrowDown,
            KeyCode::ArrowLeft,
            KeyCode::ArrowRight,
        ));

        map.key_event(KeyCode::ArrowRight, true);
        map.key_event(KeyCode::ArrowUp, true);
        let diag = std::f32::consts::FRAC_1_SQRT_2;
        assert_eq_axis2(map.action("move").unwrap(), diag, diag);
    }

    /// The docs promised a unit vector and the code never normalized, so a
    /// diagonal was 1.414 long — 41% faster than a cardinal direction.
    #[test]
    fn wasd_diagonal_is_not_faster_than_a_cardinal_direction() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_wasd(
            "move",
            KeyCode::KeyW,
            KeyCode::KeyS,
            KeyCode::KeyA,
            KeyCode::KeyD,
        ));

        map.key_event(KeyCode::KeyW, true);
        let cardinal = axis2_len(map.action("move").unwrap());
        assert!((cardinal - 1.0).abs() < 0.001, "got {cardinal}");

        map.key_event(KeyCode::KeyD, true);
        let diagonal = axis2_len(map.action("move").unwrap());
        assert!(
            (diagonal - 1.0).abs() < 0.001,
            "diagonal magnitude {diagonal} should be 1.0"
        );
    }

    /// Mouse motion is a pixel delta, not a direction: normalizing it would
    /// throw away how far the pointer actually moved.
    #[test]
    fn mouse_motion_is_not_normalized() {
        let mut map = ActionMap::new();
        map.declare(decl_axis2_mouse("look"));
        map.mouse_motion(30.0, 40.0);
        assert_eq_axis2(map.action("look").unwrap(), 30.0, 40.0);
    }

    // -- on-screen controls --------------------------------------------------

    /// An on-screen stick and the keyboard drive the **same** action, and the
    /// action cannot tell which of them spoke.
    ///
    /// The whole claim of [`Binding::Virtual`]: one `move`, two devices, and a
    /// game that reads `axis2` and never asks where the value came from.
    #[test]
    fn a_stick_and_a_keyboard_drive_one_action() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "move".to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![
                Binding::Wasd {
                    up: KeyCode::KeyW,
                    down: KeyCode::KeyS,
                    left: KeyCode::KeyA,
                    right: KeyCode::KeyD,
                },
                Binding::Virtual("stick_move".to_owned()),
            ],
        });

        assert_eq!(map.axis2("move"), (0.0, 0.0), "nothing is touching it yet");

        map.virtual_stick("stick_move", -0.5, 0.25);
        assert_eq_axis2(map.action("move").unwrap(), -0.5, 0.25);

        // A partial deflection is a partial value, which is the thing four
        // buttons could not say — and it survives the tick boundary, because a
        // finger resting on the glass reports nothing.
        map.begin_tick(TICK);
        assert_eq_axis2(map.action("move").unwrap(), -0.5, 0.25);

        // A key *and* a stick is one direction, not twice the speed: the two
        // sum to (-1.5, 0.25) and the sum is scaled back onto the disc, so the
        // heading survives and the magnitude does not exceed one.
        map.key_event(KeyCode::KeyA, true);
        let (x, y) = map.axis2("move");
        let len = x.hypot(y);
        assert!((len - 1.0).abs() < 0.001, "magnitude {len} left the disc");
        assert!(
            (y / x - 0.25 / -1.5).abs() < 0.001,
            "the summed heading was not kept, got ({x}, {y})",
        );

        map.virtual_stick("stick_move", 0.0, 0.0);
        map.key_event(KeyCode::KeyA, false);
        assert_eq!(map.axis2("move"), (0.0, 0.0), "both let go");
    }

    /// A stick reported past its own radius is still only all the way over,
    /// **and keeps its direction**.
    #[test]
    fn a_stick_past_its_radius_is_clamped_to_the_disc() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "move".to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![Binding::Virtual("stick_move".to_owned())],
        });

        // 3-4-5: a length of 5, so the clamped value is the exact (0.6, 0.8)
        // rather than a number that only looks about right.
        map.virtual_stick("stick_move", 3.0, 4.0);
        assert_eq_axis2(map.action("move").unwrap(), 0.6, 0.8);
        let len = axis2_len(map.action("move").unwrap());
        assert!((len - 1.0).abs() < 0.001, "got {len}");
    }

    /// A control drives a button action with the same edges a key does.
    #[test]
    fn a_virtual_button_has_the_edges_a_key_has() {
        let mut map = ActionMap::new();
        map.declare(decl_button(
            "pause",
            Binding::Virtual("btn_pause".to_owned()),
        ));

        map.begin_tick(TICK);
        map.virtual_button("btn_pause", true);
        assert!(map.just_pressed("pause"));
        assert!(map.button_held("pause"));

        map.begin_tick(TICK);
        assert!(
            !map.just_pressed("pause"),
            "holding the control does not press it again",
        );
        assert!(map.button_held("pause"));

        map.virtual_button("btn_pause", false);
        assert!(map.just_released("pause"));
        assert!(!map.button_held("pause"));
    }

    /// Ids name different controls: a second control does not drive the first
    /// one's action.
    #[test]
    fn a_control_drives_only_the_action_that_names_it() {
        let mut map = ActionMap::new();
        map.declare(decl_button("pause", Binding::Virtual("btn_pause".into())));
        map.declare(ActionDecl {
            name: "move".to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![Binding::Virtual("stick_move".to_owned())],
        });

        map.virtual_button("btn_other", true);
        map.virtual_stick("stick_other", 1.0, 0.0);
        assert!(!map.button_held("pause"), "another control's press");
        assert_eq!(map.axis2("move"), (0.0, 0.0), "another control's stick");

        map.virtual_button("btn_pause", true);
        map.virtual_stick("stick_move", 1.0, 0.0);
        assert!(map.button_held("pause"));
        assert_eq!(map.axis2("move"), (1.0, 0.0));
    }

    /// A stick fed to a 1-D axis reads nothing, and the docs say so: reducing a
    /// vector to one axis is a choice no control makes.
    ///
    /// The inert case pinned deliberately — a `Virtual` that silently drove
    /// `Axis1` off its `x` would be a value nobody chose.
    #[test]
    fn a_stick_on_a_one_dimensional_axis_reads_nothing() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "throttle".to_owned(),
            kind: ActionKind::Axis1,
            bindings: vec![Binding::Virtual("stick_move".to_owned())],
        });

        map.virtual_stick("stick_move", 1.0, 1.0);
        assert_eq!(map.axis1("throttle"), 0.0);
    }

    /// A non-finite deflection is dropped rather than stored, like a `NaN`
    /// mouse delta: one would poison every comparison downstream of the axis.
    #[test]
    fn a_non_finite_deflection_is_dropped() {
        let mut map = ActionMap::new();
        map.declare(ActionDecl {
            name: "move".to_owned(),
            kind: ActionKind::Axis2,
            bindings: vec![Binding::Virtual("stick_move".to_owned())],
        });

        map.virtual_stick("stick_move", 0.5, 0.5);
        map.virtual_stick("stick_move", f32::NAN, 0.0);
        assert_eq_axis2(map.action("move").unwrap(), 0.5, 0.5);
        map.virtual_stick("stick_move", 0.0, f32::INFINITY);
        assert_eq_axis2(map.action("move").unwrap(), 0.5, 0.5);
    }

    // -- assert helpers -----------------------------------------------------

    fn assert_eq_axis2(v: &ActionValue, x: f32, y: f32) {
        match v {
            ActionValue::Axis2(a) => {
                assert!(
                    (a.x - x).abs() < 0.001 && (a.y - y).abs() < 0.001,
                    "expected Axis2({x}, {y}), got Axis2({}, {})",
                    a.x,
                    a.y
                );
            }
            other => panic!("expected Axis2, got {other:?}"),
        }
    }

    fn axis2_len(v: &ActionValue) -> f32 {
        match v {
            ActionValue::Axis2(a) => (a.x * a.x + a.y * a.y).sqrt(),
            other => panic!("expected Axis2, got {other:?}"),
        }
    }

    fn assert_eq_axis1(v: &ActionValue, val: f32) {
        match v {
            ActionValue::Axis1(a) => {
                assert!(
                    (a.value - val).abs() < 0.001,
                    "expected Axis1({val}), got Axis1({})",
                    a.value
                );
            }
            other => panic!("expected Axis1, got {other:?}"),
        }
    }
}