rustial-engine 0.0.1

//! Input event protocol for the map engine.
//!
//! [`InputEvent`] is the **sole** channel through which external input
//! reaches the engine camera.  It is consumed by:
//!
//! - [`CameraController::handle_event`](crate::CameraController) --
//!   dispatches to `pan`, `zoom`, `rotate`, or viewport resize.
//! - [`MapState::handle_input`](crate::MapState) -- convenience
//!   forwarding wrapper used by host applications.
//! - The Bevy renderer (`map_input::handle_default_input`) -- translates
//!   mouse / keyboard Bevy events into `InputEvent` values.
//! - Pure WGPU host applications -- translate winit events manually.
//!
//! # Design
//!
//! - **Framework-agnostic**: no dependency on winit, Bevy, or any
//!   windowing crate.  The host is responsible for producing events.
//! - **Value semantics**: `Copy + Clone + PartialEq + Debug` -- cheap
//!   to pass, compare, and log.
//! - **Units are documented per variant**: pixels for spatial deltas,
//!   radians for rotation, multiplicative factor for zoom.
//! - Convenience constructors (`pan`, `zoom_in`, `zoom_out`, `rotate`,
//!   `resize`) are provided so callers do not need to write the struct
//!   literal syntax.

use std::fmt;

// ---------------------------------------------------------------------------
// Touch types
// ---------------------------------------------------------------------------

/// Phase of a touch contact's lifecycle.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum TouchPhase {
    /// A new finger has made contact with the screen.
    Started,
    /// An existing touch has moved.
    Moved,
    /// The finger has lifted from the screen.
    Ended,
    /// The OS cancelled the touch (e.g. palm rejection).
    Cancelled,
}

/// A single touch contact point.
///
/// The `id` field uniquely identifies a finger across its lifecycle
/// (started → moved → ended).  Coordinates are in **logical pixels**.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct TouchContact {
    /// Unique identifier for this finger (stable across phases).
    pub id: u64,
    /// Phase of the touch event.
    pub phase: TouchPhase,
    /// X position in logical pixels.
    pub x: f64,
    /// Y position in logical pixels.
    pub y: f64,
}

// ---------------------------------------------------------------------------
// InputEvent
// ---------------------------------------------------------------------------

/// An input event that can be dispatched to the engine.
///
/// All spatial values are in **logical pixels** unless otherwise noted.
/// Rotation values are in **radians**.
///
/// # Examples
///
/// ```
/// use rustial_engine::InputEvent;
///
/// // Drag the map 10 px right and 5 px down.
/// let pan = InputEvent::pan(10.0, 5.0);
///
/// // Zoom in by 10 %.
/// let zoom = InputEvent::zoom_in(1.1);
///
/// // Tilt the camera 5 degrees (? 0.087 rad).
/// let rotate = InputEvent::rotate(0.0, 0.087);
///
/// // Viewport resized.
/// let resize = InputEvent::resize(1920, 1080);
/// ```
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum InputEvent {
    /// Pan the camera by a screen-space delta.
    ///
    /// Positive `dx` moves the viewport to the **right** (map moves left).
    /// Positive `dy` moves the viewport **down** (map moves up).
    Pan {
        /// Horizontal pixel delta (positive = right).
        dx: f64,
        /// Vertical pixel delta (positive = down).
        dy: f64,
        /// Cursor's X position in logical pixels (where the drag started or currently is).
        x: Option<f64>,
        /// Cursor's Y position in logical pixels.
        y: Option<f64>,
    },

    /// Zoom by a multiplicative factor.
    ///
    /// - `factor > 1.0` zooms **in** (closer to the ground).
    /// - `0 < factor < 1.0` zooms **out**.
    /// - `factor <= 0`, `NaN`, or `+/-Inf` are silently ignored by the
    ///   [`CameraController`](crate::CameraController).
    Zoom {
        /// Multiplicative zoom factor.
        factor: f64,
        /// Cursor X position in logical pixels used as the zoom anchor.
        x: Option<f64>,
        /// Cursor Y position in logical pixels used as the zoom anchor.
        y: Option<f64>,
    },

    /// Rotate the camera by delta yaw and delta pitch.
    ///
    /// - `delta_yaw` rotates the bearing (positive = clockwise when
    ///   viewed from above).
    /// - `delta_pitch` tilts the camera (positive = toward horizon).
    Rotate {
        /// Change in yaw (bearing) in radians.
        delta_yaw: f64,
        /// Change in pitch (tilt) in radians.
        delta_pitch: f64,
    },

    /// Notify the engine of a viewport resize.
    ///
    /// The engine uses logical pixel dimensions (not physical) so that
    /// zoom-level calculations match the standard slippy-map convention.
    Resize {
        /// New viewport width in logical pixels.
        width: u32,
        /// New viewport height in logical pixels.
        height: u32,
    },

    /// A raw touch contact event.
    ///
    /// The host application emits one `Touch` per finger per phase
    /// change.  The engine's [`GestureRecognizer`](crate::gesture::GestureRecognizer)
    /// accumulates these into high-level `Pan` / `Zoom` / `Rotate`
    /// events.
    Touch(TouchContact),
}

// ---------------------------------------------------------------------------
// Convenience constructors
// ---------------------------------------------------------------------------

impl InputEvent {
    /// Create a [`Pan`](Self::Pan) event.
    #[inline]
    pub fn pan(dx: f64, dy: f64) -> Self {
        Self::Pan {
            dx,
            dy,
            x: None,
            y: None,
        }
    }

    /// Create a [`Pan`](Self::Pan) event at a specific cursor location.
    #[inline]
    pub fn pan_at(dx: f64, dy: f64, x: f64, y: f64) -> Self {
        Self::Pan {
            dx,
            dy,
            x: Some(x),
            y: Some(y),
        }
    }

    /// Create a [`Zoom`](Self::Zoom) event that zooms **in**.
    ///
    /// `factor` should be `> 1.0`.  Values ? 0 will be ignored by the
    /// controller.
    #[inline]
    pub fn zoom_in(factor: f64) -> Self {
        Self::Zoom {
            factor,
            x: None,
            y: None,
        }
    }

    /// Create a [`Zoom`](Self::Zoom) event around a specific cursor location.
    #[inline]
    pub fn zoom_at(factor: f64, x: f64, y: f64) -> Self {
        Self::Zoom {
            factor,
            x: Some(x),
            y: Some(y),
        }
    }

    /// Create a [`Zoom`](Self::Zoom) event that zooms **out**.
    ///
    /// `factor` should be `> 1.0`; the reciprocal is stored so
    /// the controller sees a value in `(0, 1)`.
    #[inline]
    pub fn zoom_out(factor: f64) -> Self {
        Self::Zoom {
            factor: if factor > 0.0 { 1.0 / factor } else { 0.0 },
            x: None,
            y: None,
        }
    }

    /// Create a [`Rotate`](Self::Rotate) event.
    #[inline]
    pub fn rotate(delta_yaw: f64, delta_pitch: f64) -> Self {
        Self::Rotate {
            delta_yaw,
            delta_pitch,
        }
    }

    /// Create a [`Resize`](Self::Resize) event.
    #[inline]
    pub fn resize(width: u32, height: u32) -> Self {
        Self::Resize { width, height }
    }

    /// Create a [`Touch`](Self::Touch) event.
    #[inline]
    pub fn touch(id: u64, phase: TouchPhase, x: f64, y: f64) -> Self {
        Self::Touch(TouchContact { id, phase, x, y })
    }
}

// ---------------------------------------------------------------------------
// Classification helpers
// ---------------------------------------------------------------------------

impl InputEvent {
    /// Returns `true` if this is a [`Pan`](Self::Pan) event.
    #[inline]
    pub fn is_pan(&self) -> bool {
        matches!(self, Self::Pan { .. })
    }

    /// Returns `true` if this is a [`Zoom`](Self::Zoom) event.
    #[inline]
    pub fn is_zoom(&self) -> bool {
        matches!(self, Self::Zoom { .. })
    }

    /// Returns `true` if this is a [`Rotate`](Self::Rotate) event.
    #[inline]
    pub fn is_rotate(&self) -> bool {
        matches!(self, Self::Rotate { .. })
    }

    /// Returns `true` if this is a [`Resize`](Self::Resize) event.
    #[inline]
    pub fn is_resize(&self) -> bool {
        matches!(self, Self::Resize { .. })
    }

    /// Returns `true` if this is a [`Touch`](Self::Touch) event.
    #[inline]
    pub fn is_touch(&self) -> bool {
        matches!(self, Self::Touch(_))
    }
}

// ---------------------------------------------------------------------------
// Display
// ---------------------------------------------------------------------------

impl fmt::Display for InputEvent {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Pan { dx, dy, x, y } => {
                if let (Some(px), Some(py)) = (x, y) {
                    write!(f, "Pan(dx={dx:.1}, dy={dy:.1}, at={px:.1},{py:.1})")
                } else {
                    write!(f, "Pan(dx={dx:.1}, dy={dy:.1})")
                }
            }
            Self::Zoom { factor, x, y } => {
                if let (Some(px), Some(py)) = (x, y) {
                    write!(f, "Zoom(factor={factor:.3}, at={px:.1},{py:.1})")
                } else {
                    write!(f, "Zoom(factor={factor:.3})")
                }
            }
            Self::Rotate {
                delta_yaw,
                delta_pitch,
            } => write!(f, "Rotate(yaw={delta_yaw:.4}, pitch={delta_pitch:.4})"),
            Self::Resize { width, height } => {
                write!(f, "Resize({width}x{height})")
            }
            Self::Touch(c) => {
                write!(
                    f,
                    "Touch(id={}, {:?}, {:.1},{:.1})",
                    c.id, c.phase, c.x, c.y
                )
            }
        }
    }
}

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

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

    // -- Construction -----------------------------------------------------

    #[test]
    fn pan_constructor() {
        let e = InputEvent::pan(10.0, -5.0);
        assert_eq!(
            e,
            InputEvent::Pan {
                dx: 10.0,
                dy: -5.0,
                x: None,
                y: None,
            }
        );
    }

    #[test]
    fn zoom_in_constructor() {
        let e = InputEvent::zoom_in(2.0);
        assert_eq!(
            e,
            InputEvent::Zoom {
                factor: 2.0,
                x: None,
                y: None,
            }
        );
    }

    #[test]
    fn zoom_at_constructor() {
        let e = InputEvent::zoom_at(2.0, 10.0, 20.0);
        assert_eq!(
            e,
            InputEvent::Zoom {
                factor: 2.0,
                x: Some(10.0),
                y: Some(20.0),
            }
        );
    }

    #[test]
    fn zoom_out_constructor() {
        let e = InputEvent::zoom_out(2.0);
        assert_eq!(
            e,
            InputEvent::Zoom {
                factor: 0.5,
                x: None,
                y: None,
            }
        );
    }

    #[test]
    fn zoom_out_zero_factor() {
        let e = InputEvent::zoom_out(0.0);
        assert_eq!(
            e,
            InputEvent::Zoom {
                factor: 0.0,
                x: None,
                y: None,
            }
        );
    }

    #[test]
    fn rotate_constructor() {
        let e = InputEvent::rotate(0.1, 0.2);
        assert_eq!(
            e,
            InputEvent::Rotate {
                delta_yaw: 0.1,
                delta_pitch: 0.2
            }
        );
    }

    #[test]
    fn resize_constructor() {
        let e = InputEvent::resize(1920, 1080);
        assert_eq!(
            e,
            InputEvent::Resize {
                width: 1920,
                height: 1080
            }
        );
    }

    // -- Classification ---------------------------------------------------

    #[test]
    fn is_pan() {
        assert!(InputEvent::pan(1.0, 2.0).is_pan());
        assert!(!InputEvent::zoom_in(1.0).is_pan());
    }

    #[test]
    fn is_zoom() {
        assert!(InputEvent::zoom_in(1.0).is_zoom());
        assert!(!InputEvent::pan(0.0, 0.0).is_zoom());
    }

    #[test]
    fn is_rotate() {
        assert!(InputEvent::rotate(0.0, 0.0).is_rotate());
        assert!(!InputEvent::resize(0, 0).is_rotate());
    }

    #[test]
    fn is_resize() {
        assert!(InputEvent::resize(800, 600).is_resize());
        assert!(!InputEvent::rotate(0.0, 0.0).is_resize());
    }

    // -- Display ----------------------------------------------------------

    #[test]
    fn display_pan() {
        let s = format!("{}", InputEvent::pan(10.0, -5.0));
        assert!(s.contains("Pan"));
        assert!(s.contains("10.0"));
    }

    #[test]
    fn display_zoom() {
        let s = format!("{}", InputEvent::zoom_in(1.5));
        assert!(s.contains("Zoom"));
        assert!(s.contains("1.5"));
    }

    #[test]
    fn display_rotate() {
        let s = format!("{}", InputEvent::rotate(0.1, 0.2));
        assert!(s.contains("Rotate"));
    }

    #[test]
    fn display_resize() {
        let s = format!("{}", InputEvent::resize(1920, 1080));
        assert!(s.contains("1920"));
        assert!(s.contains("1080"));
    }

    // -- Equality / Copy --------------------------------------------------

    #[test]
    fn copy_semantics() {
        let a = InputEvent::pan(1.0, 2.0);
        let b = a; // Copy
        assert_eq!(a, b);
    }

    #[test]
    fn clone_eq() {
        let a = InputEvent::zoom_in(3.0);
        #[allow(clippy::clone_on_copy)]
        let b = a.clone();
        assert_eq!(a, b);
    }

    #[test]
    fn different_variants_not_equal() {
        assert_ne!(InputEvent::pan(0.0, 0.0), InputEvent::zoom_in(1.0));
    }
}