//! The [`Point2D`] data type: an observed 2D feature in an image.
//!
//! Mirrors COLMAP's `colmap/scene/point2d.h`. A 2D point stores its pixel
//! location and, when it has been triangulated, the id of the 3D point it
//! observes (otherwise [`INVALID_POINT3D_ID`]).

use crate::math::Vec2;
use crate::types::{Point3DId, INVALID_POINT3D_ID};

/// A 2D observation in an image, optionally linked to a triangulated 3D point.
#[derive(Debug, Clone, Copy, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Point2D {
    /// The pixel coordinates of the observation.
    pub xy: Vec2,
    /// The id of the observed 3D point, or [`INVALID_POINT3D_ID`] if none.
    pub point3d_id: Point3DId,
}

impl Default for Point2D {
    /// A point at the origin with no associated 3D point.
    #[inline]
    fn default() -> Self {
        Self {
            xy: Vec2::zeros(),
            point3d_id: INVALID_POINT3D_ID,
        }
    }
}

impl Point2D {
    /// Creates a 2D point at `xy` that is not yet linked to a 3D point.
    #[inline]
    pub fn new(xy: Vec2) -> Self {
        Self {
            xy,
            point3d_id: INVALID_POINT3D_ID,
        }
    }

    /// Returns `true` if this observation is linked to a valid 3D point.
    #[inline]
    pub fn has_point3d(&self) -> bool {
        self.point3d_id != INVALID_POINT3D_ID
    }
}

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

    #[test]
    fn new_has_no_point3d() {
        let p = Point2D::new(Vec2::new(1.0, 2.0));
        assert!(!p.has_point3d());
        assert_eq!(p.xy, Vec2::new(1.0, 2.0));
    }

    #[test]
    fn default_is_unlinked_origin() {
        let p = Point2D::default();
        assert_eq!(p.xy, Vec2::zeros());
        assert!(!p.has_point3d());
    }

    #[test]
    fn linking_sets_flag() {
        let mut p = Point2D::new(Vec2::new(0.0, 0.0));
        p.point3d_id = 42;
        assert!(p.has_point3d());
    }
}