Merge #1011

1011: Initial geo-traits implementation r=frewsxcv a=kylebarron

- [x] I agree to follow the project's [code of conduct](https://github.com/georust/geo/blob/main/CODE_OF_CONDUCT.md).
- [ ] I added an entry to `CHANGES.md` if knowledge of this change could be valuable to users.
---

As discussed on the discord, in https://github.com/georust/geo/discussions/838, and originally in #67, this is an initial bare-bones implementation of geometry access traits for discussion. As `@frewsxcv` suggested, for now this is a separate crate in the workspace to let us iterate on some ideas.

### Future work

#### Minimize cloning in the geo-types implementation

I got lost in lifetime errors so to get things to compile I added cloning to the geo-types implementations. I.e. for `MultiPoint` each point is cloned when accessed.

Co-authored-by: Kyle Barron <kylebarron2@gmail.com>

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = ["geo", "geo-types", "geo-postgis", "geo-test-fixtures", "jts-test-runner", "geo-bool-ops-benches"]
+members = ["geo", "geo-types", "geo-traits", "geo-postgis", "geo-test-fixtures", "jts-test-runner", "geo-bool-ops-benches"]
 
 [patch.crates-io]
 

geo-traits/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "geo-traits"
+version = "0.1.0"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/georust/geo"
+documentation = "https://docs.rs/geo-traits/"
+readme = "../README.md"
+keywords = ["gis", "geo", "geography", "geospatial"]
+description = "Geospatial traits"
+rust-version = "1.65"
+edition = "2021"
+
+[features]
+
+[dependencies]
+geo-types = "0.7.9"
+
+[dev-dependencies]
+approx = ">= 0.4.0, < 0.6.0"

geo-traits/src/coord.rs

@@ -0,0 +1,64 @@
+use geo_types::{Coord, CoordNum, Point};
+
+pub trait CoordTrait: Send + Sync {
+    type T: CoordNum + Send + Sync;
+
+    /// x component of this coord
+    fn x(&self) -> Self::T;
+
+    /// y component of this coord
+    fn y(&self) -> Self::T;
+
+    /// Returns a tuple that contains the x/horizontal & y/vertical component of the coord.
+    fn x_y(&self) -> (Self::T, Self::T) {
+        (self.x(), self.y())
+    }
+}
+
+impl<T: CoordNum + Send + Sync> CoordTrait for Point<T> {
+    type T = T;
+
+    fn x(&self) -> T {
+        self.0.x
+    }
+
+    fn y(&self) -> T {
+        self.0.y
+    }
+}
+
+impl<T: CoordNum + Send + Sync> CoordTrait for &Point<T> {
+    type T = T;
+
+    fn x(&self) -> T {
+        self.0.x
+    }
+
+    fn y(&self) -> T {
+        self.0.y
+    }
+}
+
+impl<T: CoordNum + Send + Sync> CoordTrait for Coord<T> {
+    type T = T;
+
+    fn x(&self) -> T {
+        self.x
+    }
+
+    fn y(&self) -> T {
+        self.y
+    }
+}
+
+impl<T: CoordNum + Send + Sync> CoordTrait for &Coord<T> {
+    type T = T;
+
+    fn x(&self) -> T {
+        self.x
+    }
+
+    fn y(&self) -> T {
+        self.y
+    }
+}

geo-traits/src/geometry.rs

@@ -0,0 +1,87 @@
+use geo_types::{
+    CoordNum, Geometry, GeometryCollection, LineString, MultiLineString, MultiPoint, MultiPolygon,
+    Point, Polygon,
+};
+
+use super::{
+    GeometryCollectionTrait, LineStringTrait, MultiLineStringTrait, MultiPointTrait,
+    MultiPolygonTrait, PointTrait, PolygonTrait,
+};
+
+#[allow(clippy::type_complexity)]
+pub trait GeometryTrait<'a>: Send + Sync {
+    type Point: 'a + PointTrait;
+    type LineString: 'a + LineStringTrait<'a>;
+    type Polygon: 'a + PolygonTrait<'a>;
+    type MultiPoint: 'a + MultiPointTrait<'a>;
+    type MultiLineString: 'a + MultiLineStringTrait<'a>;
+    type MultiPolygon: 'a + MultiPolygonTrait<'a>;
+    type GeometryCollection: 'a + GeometryCollectionTrait<'a>;
+
+    fn as_type(
+        &'a self,
+    ) -> GeometryType<
+        'a,
+        Self::Point,
+        Self::LineString,
+        Self::Polygon,
+        Self::MultiPoint,
+        Self::MultiLineString,
+        Self::MultiPolygon,
+        Self::GeometryCollection,
+    >;
+}
+
+#[derive(Debug)]
+pub enum GeometryType<'a, P, L, Y, MP, ML, MY, GC>
+where
+    P: 'a + PointTrait,
+    L: 'a + LineStringTrait<'a>,
+    Y: 'a + PolygonTrait<'a>,
+    MP: 'a + MultiPointTrait<'a>,
+    ML: 'a + MultiLineStringTrait<'a>,
+    MY: 'a + MultiPolygonTrait<'a>,
+    GC: 'a + GeometryCollectionTrait<'a>,
+{
+    Point(&'a P),
+    LineString(&'a L),
+    Polygon(&'a Y),
+    MultiPoint(&'a MP),
+    MultiLineString(&'a ML),
+    MultiPolygon(&'a MY),
+    GeometryCollection(&'a GC),
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> GeometryTrait<'a> for Geometry<T> {
+    type Point = Point<T>;
+    type LineString = LineString<T>;
+    type Polygon = Polygon<T>;
+    type MultiPoint = MultiPoint<T>;
+    type MultiLineString = MultiLineString<T>;
+    type MultiPolygon = MultiPolygon<T>;
+    type GeometryCollection = GeometryCollection<T>;
+
+    fn as_type(
+        &'a self,
+    ) -> GeometryType<
+        'a,
+        Point<T>,
+        LineString<T>,
+        Polygon<T>,
+        MultiPoint<T>,
+        MultiLineString<T>,
+        MultiPolygon<T>,
+        GeometryCollection<T>,
+    > {
+        match self {
+            Geometry::Point(p) => GeometryType::Point(p),
+            Geometry::LineString(p) => GeometryType::LineString(p),
+            Geometry::Polygon(p) => GeometryType::Polygon(p),
+            Geometry::MultiPoint(p) => GeometryType::MultiPoint(p),
+            Geometry::MultiLineString(p) => GeometryType::MultiLineString(p),
+            Geometry::MultiPolygon(p) => GeometryType::MultiPolygon(p),
+            Geometry::GeometryCollection(p) => GeometryType::GeometryCollection(p),
+            _ => todo!(),
+        }
+    }
+}

geo-traits/src/geometry_collection.rs

@@ -0,0 +1,53 @@
+use super::GeometryTrait;
+use geo_types::{CoordNum, Geometry, GeometryCollection};
+use std::iter::Cloned;
+use std::slice::Iter;
+
+pub trait GeometryCollectionTrait<'a>: Send + Sync {
+    type ItemType: 'a + GeometryTrait<'a>;
+    type Iter: ExactSizeIterator<Item = Self::ItemType>;
+
+    /// An iterator over the geometries in this GeometryCollection
+    fn geometries(&'a self) -> Self::Iter;
+
+    /// The number of geometries in this GeometryCollection
+    fn num_geometries(&'a self) -> usize;
+
+    /// Access to a specified geometry in this GeometryCollection
+    /// Will return None if the provided index is out of bounds
+    fn geometry(&'a self, i: usize) -> Option<Self::ItemType>;
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> GeometryCollectionTrait<'a> for GeometryCollection<T> {
+    type ItemType = Geometry<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn geometries(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_geometries(&'a self) -> usize {
+        self.0.len()
+    }
+
+    fn geometry(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> GeometryCollectionTrait<'a> for &GeometryCollection<T> {
+    type ItemType = Geometry<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn geometries(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_geometries(&'a self) -> usize {
+        self.0.len()
+    }
+
+    fn geometry(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}

geo-traits/src/lib.rs

@@ -0,0 +1,19 @@
+pub use coord::CoordTrait;
+pub use geometry::{GeometryTrait, GeometryType};
+pub use geometry_collection::GeometryCollectionTrait;
+pub use line_string::LineStringTrait;
+pub use multi_line_string::MultiLineStringTrait;
+pub use multi_point::MultiPointTrait;
+pub use multi_polygon::MultiPolygonTrait;
+pub use point::PointTrait;
+pub use polygon::PolygonTrait;
+
+mod coord;
+mod geometry;
+mod geometry_collection;
+mod line_string;
+mod multi_line_string;
+mod multi_point;
+mod multi_polygon;
+mod point;
+mod polygon;

geo-traits/src/line_string.rs

@@ -0,0 +1,54 @@
+use geo_types::{Coord, CoordNum, LineString};
+
+use super::CoordTrait;
+use std::iter::Cloned;
+use std::slice::Iter;
+
+pub trait LineStringTrait<'a>: Send + Sync {
+    type ItemType: 'a + CoordTrait;
+    type Iter: ExactSizeIterator<Item = Self::ItemType>;
+
+    /// An iterator over the coords in this LineString
+    fn coords(&'a self) -> Self::Iter;
+
+    /// The number of coords in this LineString
+    fn num_coords(&'a self) -> usize;
+
+    /// Access to a specified point in this LineString
+    /// Will return None if the provided index is out of bounds
+    fn coord(&'a self, i: usize) -> Option<Self::ItemType>;
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> LineStringTrait<'a> for LineString<T> {
+    type ItemType = Coord<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn coords(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_coords(&self) -> usize {
+        self.0.len()
+    }
+
+    fn coord(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> LineStringTrait<'a> for &LineString<T> {
+    type ItemType = Coord<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn coords(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_coords(&self) -> usize {
+        self.0.len()
+    }
+
+    fn coord(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}

geo-traits/src/multi_line_string.rs

@@ -0,0 +1,53 @@
+use super::line_string::LineStringTrait;
+use geo_types::{CoordNum, LineString, MultiLineString};
+use std::iter::Cloned;
+use std::slice::Iter;
+
+pub trait MultiLineStringTrait<'a>: Send + Sync {
+    type ItemType: 'a + LineStringTrait<'a>;
+    type Iter: ExactSizeIterator<Item = Self::ItemType>;
+
+    /// An iterator over the LineStrings in this MultiLineString
+    fn lines(&'a self) -> Self::Iter;
+
+    /// The number of lines in this MultiLineString
+    fn num_lines(&'a self) -> usize;
+
+    /// Access to a specified line in this MultiLineString
+    /// Will return None if the provided index is out of bounds
+    fn line(&'a self, i: usize) -> Option<Self::ItemType>;
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> MultiLineStringTrait<'a> for MultiLineString<T> {
+    type ItemType = LineString<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn lines(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_lines(&'a self) -> usize {
+        self.0.len()
+    }
+
+    fn line(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}
+
+impl<'a, T: CoordNum + Send + Sync + 'a> MultiLineStringTrait<'a> for &MultiLineString<T> {
+    type ItemType = LineString<T>;
+    type Iter = Cloned<Iter<'a, Self::ItemType>>;
+
+    fn lines(&'a self) -> Self::Iter {
+        self.0.iter().cloned()
+    }
+
+    fn num_lines(&'a self) -> usize {
+        self.0.len()
+    }
+
+    fn line(&'a self, i: usize) -> Option<Self::ItemType> {
+        self.0.get(i).cloned()
+    }
+}