// SPDX-FileCopyrightText: 2024 Topola contributors
//
// SPDX-License-Identifier: MIT

use std::collections::BTreeMap;

use derive_getters::Getters;
use enum_dispatch::enum_dispatch;
use geo::Point;
use petgraph::{
    data::DataMap,
    graph::UnGraph,
    stable_graph::NodeIndex,
    visit::{
        Data, EdgeRef, GraphBase, IntoEdgeReferences, IntoEdges, IntoNeighbors,
        IntoNodeIdentifiers, NodeIndexable,
    },
};
use spade::{HasPosition, InsertionError, Point2};
use thiserror::Error;

use crate::{
    drawing::{
        bend::{FixedBendIndex, LooseBendIndex},
        dot::{DotIndex, FixedDotIndex},
        gear::{GearIndex, GetNextGear},
        graph::{GetMaybeNet, MakePrimitive, PrimitiveIndex},
        primitive::{GetCore, GetJoints, MakePrimitiveShape, Primitive},
        rules::AccessRules,
        seg::{FixedSegIndex, LoneLooseSegIndex, SegIndex, SeqLooseSegIndex},
        Drawing,
    },
    geometry::{shape::AccessShape, GetLayer},
    graph::{GetPetgraphIndex, MakeRef},
    layout::Layout,
    math::RotationSense,
    router::thetastar::MakeEdgeRef,
    triangulation::{GetTrianvertexNodeIndex, Triangulation},
};

use super::RouterOptions;

#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]
pub struct NavnodeIndex(pub NodeIndex<usize>);

impl core::fmt::Debug for NavnodeIndex {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "NavnodeIndex({})", self.0.index())
    }
}

impl GetPetgraphIndex for NavnodeIndex {
    fn petgraph_index(&self) -> NodeIndex<usize> {
        self.0
    }
}

/// A binavnode is a pair of navnodes, one clockwise and the other
/// counterclockwise. Unlike their constituents, binavnodes are themselves
/// not considered navnodes.
#[enum_dispatch(GetPetgraphIndex, MakePrimitive)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum BinavnodeNodeIndex {
    FixedDot(FixedDotIndex),
    FixedBend(FixedBendIndex),
    LooseBend(LooseBendIndex),
}

impl From<BinavnodeNodeIndex> for PrimitiveIndex {
    fn from(vertex: BinavnodeNodeIndex) -> Self {
        match vertex {
            BinavnodeNodeIndex::FixedDot(dot) => PrimitiveIndex::FixedDot(dot),
            BinavnodeNodeIndex::FixedBend(bend) => PrimitiveIndex::FixedBend(bend),
            BinavnodeNodeIndex::LooseBend(bend) => PrimitiveIndex::LooseBend(bend),
        }
    }
}

impl From<BinavnodeNodeIndex> for GearIndex {
    fn from(vertex: BinavnodeNodeIndex) -> Self {
        match vertex {
            BinavnodeNodeIndex::FixedDot(dot) => GearIndex::FixedDot(dot),
            BinavnodeNodeIndex::FixedBend(bend) => GearIndex::FixedBend(bend),
            BinavnodeNodeIndex::LooseBend(bend) => GearIndex::LooseBend(bend),
        }
    }
}

/// Trianvertices are the vertices of the triangulation before it is converted
/// to the navmesh by multiplying each of them into more vertices (called
/// navnodes). Every trianvertex corresponds to one or more binavnodes on
/// the navmesh.
///
/// The name "trianvertex" is a shortening of "triangulation vertex".
#[enum_dispatch(GetPetgraphIndex, MakePrimitive)]
#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub enum TrianvertexNodeIndex {
    FixedDot(FixedDotIndex),
    FixedBend(FixedBendIndex),
}

impl From<TrianvertexNodeIndex> for BinavnodeNodeIndex {
    fn from(trianvertex: TrianvertexNodeIndex) -> Self {
        match trianvertex {
            TrianvertexNodeIndex::FixedDot(dot) => BinavnodeNodeIndex::FixedDot(dot),
            TrianvertexNodeIndex::FixedBend(bend) => BinavnodeNodeIndex::FixedBend(bend),
        }
    }
}

#[derive(Debug, Clone, Copy)]
pub struct TrianvertexWeight {
    pub node: TrianvertexNodeIndex,
    pub pos: Point,
}

impl TrianvertexWeight {
    fn new_from_fixed_dot(layout: &Layout<impl AccessRules>, dot: FixedDotIndex) -> Self {
        Self {
            node: dot.into(),
            pos: dot.primitive(layout.drawing()).shape().center(),
        }
    }

    fn new_from_fixed_bend(layout: &Layout<impl AccessRules>, bend: FixedBendIndex) -> Self {
        Self {
            node: bend.into(),
            pos: bend.primitive(layout.drawing()).shape().center(),
        }
    }
}

impl GetTrianvertexNodeIndex<TrianvertexNodeIndex> for TrianvertexWeight {
    fn node_index(&self) -> TrianvertexNodeIndex {
        self.node
    }
}

impl HasPosition for TrianvertexWeight {
    type Scalar = f64;
    fn position(&self) -> Point2<Self::Scalar> {
        Point2::new(self.pos.x(), self.pos.y())
    }
}

#[derive(Clone)]
pub struct NavmeshTriangulationConstraint(pub TrianvertexWeight, pub TrianvertexWeight);

impl NavmeshTriangulationConstraint {
    fn new_from_fixed_dot_pair(
        layout: &Layout<impl AccessRules>,
        from_dot: FixedDotIndex,
        to_dot: FixedDotIndex,
    ) -> Self {
        Self(
            TrianvertexWeight::new_from_fixed_dot(layout, from_dot),
            TrianvertexWeight::new_from_fixed_dot(layout, to_dot),
        )
    }

    fn new_from_lone_loose_seg(layout: &Layout<impl AccessRules>, seg: LoneLooseSegIndex) -> Self {
        let (from_dot, to_dot) = layout.drawing().primitive(seg).joints();
        Self::new_from_fixed_dot_pair(layout, from_dot, to_dot)
    }

    fn new_from_seq_loose_seg(layout: &Layout<impl AccessRules>, seg: SeqLooseSegIndex) -> Self {
        let (from_joint, to_joint) = layout.drawing().primitive(seg).joints();

        let from_dot = match from_joint {
            DotIndex::Fixed(dot) => dot,
            DotIndex::Loose(dot) => {
                let bend = layout.drawing().primitive(dot).bend();

                layout.drawing().primitive(bend).core()
            }
        };

        let to_bend = layout.drawing().primitive(to_joint).bend();
        let to_dot = layout.drawing().primitive(to_bend).core();
        Self::new_from_fixed_dot_pair(layout, from_dot, to_dot)
    }

    fn new_from_fixed_seg(layout: &Layout<impl AccessRules>, seg: FixedSegIndex) -> Self {
        let (from_dot, to_dot) = layout.drawing().primitive(seg).joints();
        Self::new_from_fixed_dot_pair(layout, from_dot, to_dot)
    }
}

/// The terms "navnode" and "navmesh vertex", "navmesh node", "navigation
/// vertex", "navigation node" are all equivalent.
///
/// See the following blog post for more information and a visualization of the navmesh
/// during autorouting: <https://topola.dev/blog/2024/07/20/junejuly-2024-development-update/#advanced-debug-visualization>
#[derive(Debug, Clone)]
pub struct NavnodeWeight {
    pub node: BinavnodeNodeIndex,

    /// There are two navnodes for each navigable node:
    /// one is clockwise (`Some(true)`), the other counterclockwise (`Some(false)`).
    /// The origin and destination nodes however have
    /// only one corresponding navmesh vertex each (`None`).
    pub maybe_sense: Option<RotationSense>,
}

#[derive(Error, Debug, Clone)]
pub enum NavmeshError {
    #[error("failed to insert vertex in navmesh")]
    Insertion(#[from] InsertionError),
}

type NavmeshTriangulation = Triangulation<TrianvertexNodeIndex, TrianvertexWeight, ()>;

/// The navmesh holds the entire Topola's search space represented as a graph.
/// Topola's routing works by navigating over this graph with a pathfinding
/// algorithm such as A* while drawing a track segment (always a cane except
/// when going directly to destination) on the layout for each leap and
/// along-edge crossing.
///
/// The name "navmesh" is a blend of "navigation mesh".
#[derive(Clone, Getters)]
pub struct Navmesh {
    graph: UnGraph<NavnodeWeight, (), usize>,
    #[getter(skip)]
    origin: FixedDotIndex,
    #[getter(skip)]
    origin_navnode: NavnodeIndex,
    #[getter(skip)]
    destination: FixedDotIndex,
    #[getter(skip)]
    destination_navnode: NavnodeIndex,

    /// Original triangulation stored for debugging purposes.
    // XXX: Maybe have a way to compile this out in release?
    triangulation: NavmeshTriangulation,
    // Original triangulation constraints stored for debugging purposes.
    // XXX: Maybe have a way to compile this out in release?
    constraints: Vec<NavmeshTriangulationConstraint>,
}

impl Navmesh {
    /// Creates a new navmesh.
    pub fn new(
        layout: &Layout<impl AccessRules>,
        origin: FixedDotIndex,
        destination: FixedDotIndex,
        options: RouterOptions,
    ) -> Result<Self, NavmeshError> {
        let mut triangulation: NavmeshTriangulation =
            NavmeshTriangulation::new(layout.drawing().geometry().graph().node_bound());
        let mut constraints = vec![];

        let layer = layout.drawing().primitive(origin).layer();
        let maybe_net = layout.drawing().primitive(origin).maybe_net();

        for node in layout.drawing().layer_primitive_nodes(layer) {
            let primitive = node.primitive(layout.drawing());

            if let Some(primitive_net) = primitive.maybe_net() {
                if node == origin.into()
                    || node == destination.into()
                    || Some(primitive_net) != maybe_net
                {
                    match node {
                        PrimitiveIndex::FixedDot(dot) => {
                            triangulation
                                .add_vertex(TrianvertexWeight::new_from_fixed_dot(layout, dot))?;
                        }
                        PrimitiveIndex::LoneLooseSeg(seg) => {
                            Self::add_constraint(
                                &mut triangulation,
                                &mut constraints,
                                NavmeshTriangulationConstraint::new_from_lone_loose_seg(
                                    layout, seg,
                                ),
                            )?;
                        }
                        PrimitiveIndex::SeqLooseSeg(seg) => {
                            Self::add_constraint(
                                &mut triangulation,
                                &mut constraints,
                                NavmeshTriangulationConstraint::new_from_seq_loose_seg(layout, seg),
                            )?;
                        }
                        PrimitiveIndex::FixedBend(bend) => {
                            triangulation
                                .add_vertex(TrianvertexWeight::new_from_fixed_bend(layout, bend))?;
                        }
                        _ => (),
                    }
                }
            }
        }

        for node in layout.drawing().layer_primitive_nodes(layer) {
            let primitive = node.primitive(layout.drawing());

            if let Some(primitive_net) = primitive.maybe_net() {
                if node == origin.into()
                    || node == destination.into()
                    || Some(primitive_net) != maybe_net
                {
                    // If you have a band that was routed from a polygonal pad,
                    // when you will start a new routing some of the constraint
                    // edges created from the loose segs of a band will
                    // intersect some of the constraint edges created from the
                    // fixed segs constituting the pad boundary.
                    //
                    // Such constraint intersections are erroneous and cause
                    // Spade to throw a panic at runtime. So, to prevent this
                    // from occuring, we iterate over the layout for the second
                    // time, after all the constraint edges from bands have been
                    // placed, and only then add constraint edges created from
                    // fixed segs that do not cause an intersection.
                    match node {
                        PrimitiveIndex::FixedSeg(seg) => {
                            let constraint =
                                NavmeshTriangulationConstraint::new_from_fixed_seg(layout, seg);

                            if !triangulation.intersects_constraint(&constraint.0, &constraint.1) {
                                Self::add_constraint(
                                    &mut triangulation,
                                    &mut constraints,
                                    constraint,
                                );
                            }
                        }
                        _ => (),
                    }
                }
            }
        }

        Self::new_from_triangulation(
            layout,
            triangulation,
            origin,
            destination,
            constraints,
            options,
        )
    }

    fn add_constraint(
        triangulation: &mut NavmeshTriangulation,
        constraints: &mut Vec<NavmeshTriangulationConstraint>,
        constraint: NavmeshTriangulationConstraint,
    ) -> Result<(), InsertionError> {
        triangulation.add_constraint_edge(constraint.0, constraint.1)?;
        constraints.push(constraint);
        Ok(())
    }

    fn new_from_triangulation(
        layout: &Layout<impl AccessRules>,
        triangulation: NavmeshTriangulation,
        origin: FixedDotIndex,
        destination: FixedDotIndex,
        constraints: Vec<NavmeshTriangulationConstraint>,
        options: RouterOptions,
    ) -> Result<Self, NavmeshError> {
        let mut graph: UnGraph<NavnodeWeight, (), usize> = UnGraph::default();
        let mut origin_navnode = None;
        let mut destination_navnode = None;

        let mut map = BTreeMap::new();

        for trianvertex in triangulation.node_identifiers() {
            if trianvertex == origin.into() {
                let navnode = graph.add_node(NavnodeWeight {
                    node: trianvertex.into(),
                    maybe_sense: None,
                });

                origin_navnode = Some(navnode);
                map.insert(trianvertex, vec![(navnode, navnode)]);
            } else if trianvertex == destination.into() {
                let navnode = graph.add_node(NavnodeWeight {
                    node: trianvertex.into(),
                    maybe_sense: None,
                });

                destination_navnode = Some(navnode);
                map.insert(trianvertex, vec![(navnode, navnode)]);
            } else {
                map.insert(trianvertex, vec![]);

                let mut gear =
                    Into::<GearIndex>::into(Into::<BinavnodeNodeIndex>::into(trianvertex));

                if options.squeeze_through_under_bends {
                    Self::add_trianvertex_to_graph_and_map_as_binavnode(
                        &mut graph,
                        &mut map,
                        trianvertex,
                        trianvertex.into(),
                    );

                    if options.wrap_around_bands {
                        while let Some(bend) = gear.ref_(layout.drawing()).next_gear() {
                            Self::add_trianvertex_to_graph_and_map_as_binavnode(
                                &mut graph,
                                &mut map,
                                trianvertex,
                                bend.into(),
                            );
                            gear = bend.into();
                        }
                    }
                } else if let Some(first_bend) = gear.ref_(layout.drawing()).next_gear() {
                    let mut bend = first_bend;

                    while let Some(next_bend) = gear.ref_(layout.drawing()).next_gear() {
                        bend = next_bend;
                        gear = bend.into();
                    }

                    Self::add_trianvertex_to_graph_and_map_as_binavnode(
                        &mut graph,
                        &mut map,
                        trianvertex,
                        bend.into(),
                    );
                } else {
                    Self::add_trianvertex_to_graph_and_map_as_binavnode(
                        &mut graph,
                        &mut map,
                        trianvertex,
                        trianvertex.into(),
                    );
                }
            }
        }

        for edge in triangulation.edge_references() {
            Self::add_trianedge_to_graph_as_quadrinavedge(
                &mut graph,
                &map,
                edge.source(),
                edge.target(),
            );
        }

        // The existence of a constraint edge does not (!) guarantee that this
        // edge exactly will be present in the triangulation. It appears that
        // Spade splits a constraint edge into two if an endpoint of another
        // constraint lies on it.
        //
        // So now we go over all the constraints and make sure that
        // quadrinavedges exist for every one of them.
        for constraint in constraints.iter() {
            Self::add_trianedge_to_graph_as_quadrinavedge(
                &mut graph,
                &map,
                constraint.0.node,
                constraint.1.node,
            );
        }

        Ok(Self {
            graph,
            origin,
            origin_navnode: NavnodeIndex(origin_navnode.unwrap()),
            destination,
            destination_navnode: NavnodeIndex(destination_navnode.unwrap()),
            triangulation,
            constraints,
        })
    }

    fn add_trianvertex_to_graph_and_map_as_binavnode(
        graph: &mut UnGraph<NavnodeWeight, (), usize>,
        map: &mut BTreeMap<TrianvertexNodeIndex, Vec<(NodeIndex<usize>, NodeIndex<usize>)>>,
        trianvertex: TrianvertexNodeIndex,
        node: BinavnodeNodeIndex,
    ) {
        let navnode1 = graph.add_node(NavnodeWeight {
            node,
            maybe_sense: Some(RotationSense::Counterclockwise),
        });

        let navnode2 = graph.add_node(NavnodeWeight {
            node,
            maybe_sense: Some(RotationSense::Clockwise),
        });

        map.get_mut(&trianvertex)
            .unwrap()
            .push((navnode1, navnode2));
    }

    fn add_trianedge_to_graph_as_quadrinavedge(
        graph: &mut UnGraph<NavnodeWeight, (), usize>,
        map: &BTreeMap<TrianvertexNodeIndex, Vec<(NodeIndex<usize>, NodeIndex<usize>)>>,
        from_trianvertex: TrianvertexNodeIndex,
        to_trianvertex: TrianvertexNodeIndex,
    ) {
        for (from_navnode1, from_navnode2) in map[&from_trianvertex].iter() {
            for (to_navnode1, to_navnode2) in map[&to_trianvertex].iter() {
                graph.update_edge(*from_navnode1, *to_navnode1, ());
                graph.update_edge(*from_navnode1, *to_navnode2, ());
                graph.update_edge(*from_navnode2, *to_navnode1, ());
                graph.update_edge(*from_navnode2, *to_navnode2, ());
            }
        }
    }

    /// Returns the origin node.
    pub fn origin(&self) -> FixedDotIndex {
        self.origin
    }

    /// Returns the navnode of the origin node.
    pub fn origin_navnode(&self) -> NavnodeIndex {
        self.origin_navnode
    }

    /// Returns the destination node.
    pub fn destination(&self) -> FixedDotIndex {
        self.destination
    }

    /// Returns the navnode of the destination node.
    pub fn destination_navnode(&self) -> NavnodeIndex {
        self.destination_navnode
    }
}

impl GraphBase for Navmesh {
    type NodeId = NavnodeIndex;
    type EdgeId = (NavnodeIndex, NavnodeIndex);
}

impl Data for Navmesh {
    type NodeWeight = NavnodeWeight;
    type EdgeWeight = ();
}

impl DataMap for Navmesh {
    fn node_weight(&self, vertex: Self::NodeId) -> Option<&Self::NodeWeight> {
        self.graph.node_weight(vertex.petgraph_index())
    }

    fn edge_weight(&self, _edge: Self::EdgeId) -> Option<&Self::EdgeWeight> {
        None
    }
}

#[derive(Debug, Clone, Copy)]
pub struct NavmeshEdgeReference {
    from: NavnodeIndex,
    to: NavnodeIndex,
}

impl EdgeRef for NavmeshEdgeReference {
    type NodeId = NavnodeIndex;
    type EdgeId = (NavnodeIndex, NavnodeIndex);
    type Weight = ();

    fn source(&self) -> Self::NodeId {
        self.from
    }

    fn target(&self) -> Self::NodeId {
        self.to
    }

    fn weight(&self) -> &Self::Weight {
        &()
    }

    fn id(&self) -> Self::EdgeId {
        (self.from, self.to)
    }
}

impl<'a> IntoNeighbors for &'a Navmesh {
    type Neighbors = Box<dyn Iterator<Item = NavnodeIndex> + 'a>;

    fn neighbors(self, vertex: Self::NodeId) -> Self::Neighbors {
        Box::new(
            self.graph
                .neighbors(vertex.petgraph_index())
                .map(NavnodeIndex),
        )
    }
}

impl<'a> IntoEdgeReferences for &'a Navmesh {
    type EdgeRef = NavmeshEdgeReference;
    type EdgeReferences = Box<dyn Iterator<Item = NavmeshEdgeReference> + 'a>;

    fn edge_references(self) -> Self::EdgeReferences {
        Box::new(
            self.graph
                .edge_references()
                .map(|edge| NavmeshEdgeReference {
                    from: NavnodeIndex(edge.source()),
                    to: NavnodeIndex(edge.target()),
                }),
        )
    }
}

impl<'a> IntoEdges for &'a Navmesh {
    type Edges = Box<dyn Iterator<Item = NavmeshEdgeReference> + 'a>;

    fn edges(self, vertex: Self::NodeId) -> Self::Edges {
        Box::new(
            self.graph
                .edges(vertex.petgraph_index())
                .map(|edge| NavmeshEdgeReference {
                    from: NavnodeIndex(edge.source()),
                    to: NavnodeIndex(edge.target()),
                }),
        )
    }
}

impl<'a> MakeEdgeRef for &'a Navmesh {
    fn edge_ref(
        &self,
        edge_id: <&'a Navmesh as GraphBase>::EdgeId,
    ) -> <&'a Navmesh as IntoEdgeReferences>::EdgeRef {
        NavmeshEdgeReference {
            from: edge_id.0,
            to: edge_id.1,
        }
    }
}