use super::delaunay_core::Dcel;

use crate::{

    delaunay_core::bulk_load, handles::VertexHandle, HasPosition, HintGenerator, InsertionError,

    LastUsedVertexHintGenerator, NaturalNeighbor, Point2, Triangulation, TriangulationExt,

};

use alloc::vec::Vec;

use num_traits::Float;

#[cfg(feature = "serde")]

use serde::{Deserialize, Serialize};

/// A two-dimensional [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation).

///

/// A Delaunay triangulation  a triangulation that fulfills the *Delaunay Property*: No

/// vertex of the triangulation is contained in the

/// [circumcircle](https://en.wikipedia.org/wiki/Circumscribed_circle) of any triangle.

/// As a consequence, Delaunay triangulations are well suited to support interpolation

/// algorithms and nearest neighbor searches. It is often constructed in order to retrieve its dual

/// graph, the [Voronoi diagram](#voronoi-diagram).

///

#[doc = include_str!("../images/circumcircle.svg")]

///

/// *An example triangulation with a few circumcircles drawn. No circumcircle contains more than three vertices.*

///

/// Most methods on this type require the [Triangulation] trait. Refer to its documentation

/// for more details on how to use `DelaunayTriangulation`.

///

/// # Basic Usage

/// Vertices need to implement the [HasPosition] trait. Spade bundles

/// the [Point2] struct for basic use cases.

///

/// ## Basic example

///  ```

/// use spade::{DelaunayTriangulation, Triangulation, Point2, InsertionError};

///

/// fn main() -> Result<(), InsertionError> {

///

///     let mut triangulation: DelaunayTriangulation<_> = DelaunayTriangulation::new();

///

///     // Insert three vertices that span one triangle (face)

///     triangulation.insert(Point2::new(0.0, 1.0))?;

///     triangulation.insert(Point2::new(1.0, 1.0))?;

///     triangulation.insert(Point2::new(0.5, -1.0))?;

///

///     assert_eq!(triangulation.num_vertices(), 3);

///     assert_eq!(triangulation.num_inner_faces(), 1);

///     assert_eq!(triangulation.num_undirected_edges(), 3);

///     Ok(())

/// }

/// ```

/// ## Right handed and left-handed coordinate systems

/// For simplicity, all method names and their documentation assume that the underlying coordinate system

/// is right-handed (e.g. x-axis points to the right, y-axis points upwards). If a left-handed system

/// (lhs) is used, any term related to orientation needs to be reversed:

///  - "left" becomes "right" (example: the face of a directed edge is on the right side for a lhs)

///  - "counter clock wise" becomes "clockwise" (example: the vertices of a face are returned in clock wise order for a lhs)

///  

/// <table>

/// <tr><th>left-handed system</th><th>right-handed system</th></tr>

/// <tr><td>

#[doc = concat!(include_str!("../images/lhs.svg"), "</td><td>",include_str!("../images/rhs.svg"), " </td></tr></table>")]

/// # Extracting geometry information

///

/// Spade uses [handles](crate::handles) to extract the triangulation's geometry.

/// Handles are usually retrieved by inserting a vertex or by iterating.

///  

/// ## Example

/// ```

///  fn main() -> Result<(), spade::InsertionError> {

/// use crate::spade::{DelaunayTriangulation, Triangulation, Point2};

///

/// let mut triangulation: DelaunayTriangulation<Point2<f64>> = DelaunayTriangulation::new();

///

/// triangulation.insert(Point2::new(0.0, 1.0))?;

/// triangulation.insert(Point2::new(1.0, 1.0))?;

/// triangulation.insert(Point2::new(0.5, -1.0))?;

///

/// for face in triangulation.inner_faces() {

///   // face is a FaceHandle

///   // edges is an array containing 3 directed edge handles

///   let edges = face.adjacent_edges();

///   for edge in &edges {

///     let from = edge.from();

/// let to = edge.to();

///     // from and to are vertex handles

///     println!("found an edge: {:?} -> {:?}", from, to);

///   }

///

///   // vertices is an array containing 3 vertex handles

///   let vertices = face.vertices();

///   for vertex in &vertices {

///     println!("Found vertex with position {:?}", vertex.position());

///   }

/// }

/// # Ok(()) }

/// ```

///

/// # Type parameters

/// The triangulation's vertices, edges and faces can contain custom data.

/// By default, the edge and face types are set to `()`. The vertex type must

/// be specified.

///

///  * `V: HasPosition` The vertex type

///  * `DE: Default` The directed edge type.

///  * `UE: Default` The undirected edge type.

///  * `F: Default` The face type.

///

/// Only vertices can be inserted directly. Faces and edges are create via `Default::default()`.

/// Usually, edge and face data will need to be modified in a separate pass.

///

/// Setting any custom data works by calling [vertex_data_mut](Triangulation::vertex_data_mut),

/// [directed_edge_data_mut](Triangulation::directed_edge_data_mut),

/// [undirected_edge_data_mut](Triangulation::undirected_edge_data_mut) and

/// [face_data_mut](Triangulation::face_data_mut).

///  

/// ## Example

/// ```

/// fn main() -> Result<(), spade::InsertionError> {

/// use crate::spade::{DelaunayTriangulation, Triangulation, Point2};

///

/// // A custom undirected edge type used to cache the length of an edge

/// #[derive(Default)]

/// struct EdgeWithLength { length: f64 }

///

/// // Creates a new triangulation with a custom undirected edge type

/// let mut triangulation: DelaunayTriangulation<Point2<f64>, (), EdgeWithLength>

///                          = DelaunayTriangulation::new();

///

/// triangulation.insert(Point2::new(0.0, 1.0))?;

/// triangulation.insert(Point2::new(1.0, 1.0))?;

/// triangulation.insert(Point2::new(0.5, -1.0))?;

///

/// for edge in triangulation.fixed_undirected_edges() {

///   let positions = triangulation.undirected_edge(edge).positions();

///   let length = positions[0].distance_2(positions[1]).sqrt();

///   // Write length into the edge data

///   triangulation.undirected_edge_data_mut(edge).length = length;

/// }

///

/// for edge in triangulation.undirected_edges() {

///    let length = edge.data().length;

///    assert!(length > 0.0);

/// }

/// # Ok(()) }

/// ```

///

/// # Outer face

/// Every triangulation contains an *outer face* that is adjacent to all edges of the

/// triangulation's convex hull. The outer face is even present for a triangulation without

/// vertices. It is either referenced by calling [Triangulation::outer_face()] or

/// [handles::OUTER_FACE](crate::handles::OUTER_FACE)

///

#[doc = include_str!("../images/outer_faces.svg")]

///

/// # Voronoi Diagram

///

/// the dual graph of the Delaunay triangulation is the *Voronoi diagram*. The Voronoi diagram

/// subdivides the plane into several *Voronoi cells* (called `VoronoiFace` by Spade for consistency)

/// which contain all points in the plane that share a common nearest neighbor.

///

/// Keep in mind that "faces" and "vertices" are swapped - an (inner) Voronoi *vertex*

/// corresponds to a single Delaunay *face*.

/// The position of an inner voronoi vertex is the *circumcenter* of its dual Delaunay

/// face.

///

#[doc = include_str!("../images/basic_voronoi.svg")]

///

/// *A Delaunay triangulation (black lines) and its dual graph, the Voronoi diagram (blue lines)*

///

/// ## Extracting the Voronoi Diagram

/// Spade defines various functions to extract information about the Voronoi diagram:

///

/// **Types**

///  * [DirectedVoronoiEdge](crate::handles::DirectedVoronoiEdge)

///  * [UndirectedVoronoiEdge](crate::handles::UndirectedVoronoiEdge)

///  * [VoronoiVertex](crate::handles::VoronoiVertex)

///  * [VoronoiFace](crate::handles::VoronoiFace)

///

/// **Iterators**

///  * [Triangulation::directed_voronoi_edges()]

///  * [Triangulation::undirected_voronoi_edges()]

///

/// **Conversion**

///  * [DirectedVoronoiEdge::as_undirected()](crate::handles::DirectedVoronoiEdge::as_undirected())

///  * [UndirectedVoronoiEdge::as_directed()](crate::handles::UndirectedVoronoiEdge::as_directed())

///  * [DirectedEdgeHandle::as_voronoi_edge()](crate::handles::DirectedEdgeHandle::as_voronoi_edge())

///  * [DirectedVoronoiEdge::as_delaunay_edge()](crate::handles::DirectedVoronoiEdge::as_delaunay_edge())

///  * [UndirectedEdgeHandle::as_voronoi_edge()](crate::handles::UndirectedEdgeHandle::as_voronoi_edge())

///  * [UndirectedVoronoiEdge::as_delaunay_edge()](crate::handles::UndirectedVoronoiEdge::as_delaunay_edge())

///

/// ## Extracting the Voronoi Diagram (Example)

/// Extracting the geometry of the voronoi diagram can be slightly tricky as some of the voronoi

/// extend into infinity (see the dashed lines in the example above).

///

/// ```

/// use spade::handles::{VoronoiVertex::Inner, VoronoiVertex::Outer};

/// use spade::{DelaunayTriangulation, Point2, Triangulation};

///

/// // Prints out the location of all voronoi edges in a triangulation

/// fn log_voronoi_diagram(triangulation: &DelaunayTriangulation<Point2<f64>>) {

///     for edge in triangulation.undirected_voronoi_edges() {

///         match edge.vertices() {

///             [Inner(from), Inner(to)] => {

///                 // "from" and "to" are inner faces of the Delaunay triangulation

///                 println!(

///                     "Found voronoi edge between {:?} and {:?}",

///                     from.circumcenter(),

///                     to.circumcenter()

///                 );

///             }

///             [Inner(from), Outer(edge)] | [Outer(edge), Inner(from)] => {

///                 // Some lines don't have a finite end and extend into infinity.

///                 println!(

///                     "Found infinite voronoi edge going out of {:?} into the direction {:?}",

///                     from.circumcenter(),

///                     edge.direction_vector()

///                 );

///             }

///             [Outer(_), Outer(_)] => {

///                 // This case only happens if all vertices of the triangulation lie on the

///                 // same line and can probably be ignored.

///             }

///         }

///     }

/// }

/// ```

///

/// # Performance tuning

///

/// Fine-tuning a Delaunay triangulation can be more tricky from time to time. However, some will *nearly always* be

/// the right thing to do:

///

/// - Measure, don't guess. Execution times are hard to predict.

/// - If you plan to perform several random access queries (e.g. looking up the point at an arbitrary position):

///   Consider using `[HierarchyHintGenerator](crate::HierarchyHintGenerator)

/// - For data sets with uniformly distributed vertices: Use [HierarchyHintGenerator](crate::HierarchyHintGenerator) if

///   bulk loading is not applicable.

/// - For data sets where vertices are inserted in close local proximity (each vertex is not too far away from the

///   previously inserted vertex): Consider using [LastUsedVertexHintGenerator](LastUsedVertexHintGenerator).

/// - Try to avoid large custom data types for edges, vertices and faces.

/// - Using `f64` and `f32` as scalar type will usually end up roughly having the same run time performance.

/// - Prefer using [bulk_load](Triangulation::bulk_load) over [insert](Triangulation::insert).

/// - The run time of all vertex operations (insertion, removal and lookup) is roughly the same for larger triangulations.

///   

/// ## Complexity classes

///

/// This table display the average and amortized cost for inserting a vertex into a triangulation with `n` vertices.

///

/// |                             | Uniformly distributed vertices | Insertion of vertices with local proximity |

/// |-----------------------------|--------------------------------|--------------------------------------------|

/// | LastUsedVertexHintGenerator |        O(sqrt(n)) (worst case) |                  O(1) (best case), fastest |

/// | HierarchyHintGenerator      |       O(log(n)) (Average case) |                           O(1) (best case) |

///

/// # See also

/// Delaunay triangulations are closely related to [constrained Delaunay triangulations](crate::ConstrainedDelaunayTriangulation)

#[doc(alias = "Voronoi")]

#[doc(alias = "Voronoi diagram")]

#[doc(alias = "Delaunay")]

#[derive(Debug, Clone)]

#[cfg_attr(

    feature = "serde",

    derive(Serialize, Deserialize),

    serde(crate = "serde")

)]

pub struct DelaunayTriangulation<V, DE = (), UE = (), F = (), L = LastUsedVertexHintGenerator>

where

    V: HasPosition,

    DE: Default,

    UE: Default,

    F: Default,

    L: HintGenerator<<V as HasPosition>::Scalar>,

{

    pub(crate) dcel: Dcel<V, DE, UE, F>,

    pub(crate) hint_generator: L,

}

impl<V, DE, UE, F, L> DelaunayTriangulation<V, DE, UE, F, L>

where

    V: HasPosition,

    DE: Default,

    UE: Default,

    F: Default,

    L: HintGenerator<<V as HasPosition>::Scalar>,

{

    /// Returns the nearest neighbor of a given input vertex.

    ///

    /// Returns `None` if the triangulation is empty.

    ///

    /// # Runtime

    /// This method takes `O(sqrt(n))` on average where n is the number of vertices.

    pub fn nearest_neighbor(

        &self,

        position: Point2<<V as HasPosition>::Scalar>,

    ) -> Option<VertexHandle<V, DE, UE, F>> {

        if self.num_vertices() == 0 {

            return None;

        }

        let hint = self.hint_generator().get_hint(position);

        let hint = self.validate_vertex_handle(hint);

        let vertex = self.walk_to_nearest_neighbor(hint, position);

        self.hint_generator().notify_vertex_lookup(vertex.fix());

        Some(vertex)

    }

    /// Creates a new delaunay triangulation with an efficient bulk loading strategy.

    ///

    /// In contrast to [Triangulation::bulk_load], this method will create a triangulation with

    /// vertices returned *in the same order* as the input vertices.

    ///

    /// # Duplicate handling

    ///

    /// If two vertices have the same position, only one of them will be included in the final

    /// triangulation. It is undefined which of them is discarded.

    ///

    /// For example, if the input vertices are [v0, v1, v2, v1] (where v1 is duplicated), the

    /// resulting triangulation will be either

    /// [v0, v1, v2] or [v0, v2, v1]

    ///

    /// Consider checking the triangulation's size after calling this method to ensure that no

    /// duplicates were present.

    ///

    /// # Example

    /// ```

    /// # use spade::InsertionError;

    /// use spade::{DelaunayTriangulation, Point2, Triangulation};

    ///

    /// # fn main() -> Result<(), InsertionError> {

    /// let vertices = vec![

    ///      Point2::new(0.5, 1.0),

    ///      Point2::new(-0.5, 2.0),

    ///      Point2::new(0.2, 3.0),

    ///      Point2::new(0.0, 4.0),

    ///      Point2::new(-0.2, 5.0)

    /// ];

    /// let triangulation = DelaunayTriangulation::<Point2<f64>>::bulk_load_stable(vertices.clone())?;

    /// // This assert will not hold for regular bulk loading!

    /// assert_eq!(triangulation.vertices().map(|v| *v.data()).collect::<Vec<_>>(), vertices);

    ///

    /// // This is how you would check for duplicates:

    /// let duplicates_found = triangulation.num_vertices() < vertices.len();

    /// assert!(!duplicates_found);

    /// # Ok(()) }

    /// ```

    pub fn bulk_load_stable(elements: Vec<V>) -> Result<Self, InsertionError> {

        let mut result: Self = crate::delaunay_core::bulk_load_stable::<

            _,

            _,

            DelaunayTriangulation<_, _, _, _, _>,

            _,

        >(bulk_load, elements)?;

        *result.hint_generator_mut() = L::initialize_from_triangulation(&result);

        Ok(result)

    }

}

impl<V, DE, UE, F, L> Default for DelaunayTriangulation<V, DE, UE, F, L>

where

    V: HasPosition,

    DE: Default,

    UE: Default,

    F: Default,

    L: HintGenerator<<V as HasPosition>::Scalar>,

{

    fn default() -> Self {

        Self {

            dcel: Default::default(),

            hint_generator: Default::default(),

        }

    }

}

impl<V, DE, UE, F, L> DelaunayTriangulation<V, DE, UE, F, L>

where

    V: HasPosition,

    DE: Default,

    UE: Default,

    F: Default,

    V::Scalar: Float,

    L: HintGenerator<<V as HasPosition>::Scalar>,

{

    /// Allows using natural neighbor interpolation on this triangulation. Refer to the documentation

    /// of [NaturalNeighbor] for more information.

    pub fn natural_neighbor(&self) -> NaturalNeighbor<Self> {

        NaturalNeighbor::new(self)

    }

}

impl<V, DE, UE, F, L> Triangulation for DelaunayTriangulation<V, DE, UE, F, L>

where

    V: HasPosition,

    DE: Default,

    UE: Default,

    F: Default,

    L: HintGenerator<<V as HasPosition>::Scalar>,

{

    type Vertex = V;

    type DirectedEdge = DE;

    type UndirectedEdge = UE;

    type Face = F;

    type HintGenerator = L;

    fn s(&self) -> &Dcel<V, DE, UE, F> {

        &self.dcel

    }

    fn s_mut(&mut self) -> &mut Dcel<V, DE, UE, F> {

        &mut self.dcel

    }

    fn hint_generator(&self) -> &Self::HintGenerator {

        &self.hint_generator

    }

    fn hint_generator_mut(&mut self) -> &mut Self::HintGenerator {

        &mut self.hint_generator

    }

    fn from_parts(

        dcel: Dcel<Self::Vertex, Self::DirectedEdge, Self::UndirectedEdge, Self::Face>,

        hint_generator: Self::HintGenerator,

        num_constraints: usize,

    ) -> Self {

        assert_eq!(num_constraints, 0);

        Self {

            dcel,

            hint_generator,

        }

    }

    fn into_parts(

        self,

    ) -> (

        Dcel<Self::Vertex, Self::DirectedEdge, Self::UndirectedEdge, Self::Face>,

        Self::HintGenerator,

        usize,

    ) {

        (self.dcel, self.hint_generator, 0)

    }

}

#[cfg(test)]

mod test {

    use crate::test_utilities::{random_points_with_seed, SEED};

    use crate::{DelaunayTriangulation, InsertionError, Point2, Triangulation};

    #[allow(unused)]

    #[cfg(feature = "serde")]

    // Just needs to compile

    fn check_serde() {

        use serde::{Deserialize, Serialize};

        use crate::{HierarchyHintGenerator, LastUsedVertexHintGenerator, Point2};

        fn requires_serde<'de, T: Serialize + Deserialize<'de>>() {}

        type DT<L> = DelaunayTriangulation<Point2<f64>, (), (), (), L>;

        requires_serde::<DT<LastUsedVertexHintGenerator>>();

        requires_serde::<DT<HierarchyHintGenerator<f64>>>();

    }

    #[test]

    fn test_nearest_neighbor() -> Result<(), InsertionError> {

        const SIZE: usize = 54;

        let points = random_points_with_seed(SIZE, SEED);

        let d = DelaunayTriangulation::<_>::bulk_load(points.clone())?;

        let sample_points = random_points_with_seed(SIZE * 3, SEED);

        for p in sample_points {

            let nn_delaunay = d.nearest_neighbor(p);

            let nn_linear_search = points.iter().min_by(|l, r| {

                let d1 = l.distance_2(p);

                let d2 = r.distance_2(p);

                d1.partial_cmp(&d2).unwrap()

            });

            assert_eq!(nn_delaunay.map(|p| p.position()), nn_linear_search.cloned());

        }

        Ok(())

    }

    #[test]

    fn test_nearest_neighbor_small() -> Result<(), InsertionError> {

        let mut d = DelaunayTriangulation::<_>::new();

        assert_eq!(None, d.nearest_neighbor(Point2::new(0.0, 0.0)));

        d.insert(Point2::new(0.0, 0.0))?;

        assert!(d.nearest_neighbor(Point2::new(0.0, 1.0)).is_some());

        Ok(())

    }

    #[test]

    #[allow(clippy::redundant_clone)]

    #[allow(unused_must_use)]

    fn test_clone_is_implemented() {

        // Just needs to compile

        DelaunayTriangulation::<Point2<f64>>::new().clone();

    }

}