// SPDX-FileCopyrightText: 2025 Topola contributors
//
// SPDX-License-Identifier: MIT

use std::ops::{Index, IndexMut};

use derive_getters::Getters;
use enum_dispatch::enum_dispatch;
use geo::Point;
use spade::{handles::FixedVertexHandle, HasPosition, InsertionError, Point2};

use crate::{
    drawing::{
        bend::FixedBendIndex,
        dot::{DotIndex, FixedDotIndex},
        graph::{GetMaybeNet, MakePrimitiveRef, PrimitiveIndex},
        primitive::{GetCore, GetJoints, MakePrimitiveShape},
        rules::AccessRules,
        seg::{FixedSegIndex, LoneLooseSegIndex, SeqLooseSegIndex},
    },
    geometry::{shape::AccessShape, GetLayer},
    graph::{GenericIndex, GetIndex},
    layout::{CompoundEntryLabel, Layout},
    triangulation::{GetTrianvertexNodeIndex, Triangulation},
};

use super::{navmesh::NavmeshError, RouterOptions};

/// Prenavmesh nodes are the vertices of constrained Delaunay triangulation
/// before it is converted to the navmesh, which is done by multiplying each
/// of the prenavmesh nodes into more nodes, called navnodes.
#[enum_dispatch(GetIndex, MakePrimitive)]
#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub enum PrenavmeshNodeIndex {
    FixedDot(FixedDotIndex),
    FixedBend(FixedBendIndex),
}

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

#[derive(Clone, Copy)]
pub struct PrenavmeshWeight {
    pub node: PrenavmeshNodeIndex,
    pub pos: Point,
}

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

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

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

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

#[derive(Clone, Copy)]
pub struct PrenavmeshConstraint(pub PrenavmeshWeight, pub PrenavmeshWeight);

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

    pub 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)
    }

    pub 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)
    }

    pub 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)
    }
}

#[derive(Clone)]
pub struct PrenavnodeToHandleMap {
    fixed_dot_to_handle: Box<[Option<FixedVertexHandle>]>,
    fixed_bend_to_handle: Box<[Option<FixedVertexHandle>]>,
}

impl PrenavnodeToHandleMap {
    pub fn new(fixed_dot_bound: usize, fixed_bend_bound: usize) -> Self {
        Self {
            fixed_dot_to_handle: vec![None; fixed_dot_bound].into_boxed_slice(),
            fixed_bend_to_handle: vec![None; fixed_bend_bound].into_boxed_slice(),
        }
    }
}

impl Index<PrenavmeshNodeIndex> for PrenavnodeToHandleMap {
    type Output = Option<FixedVertexHandle>;

    fn index(&self, prenavnode: PrenavmeshNodeIndex) -> &Self::Output {
        match prenavnode {
            PrenavmeshNodeIndex::FixedDot(dot) => &self.fixed_dot_to_handle[dot.index()],
            PrenavmeshNodeIndex::FixedBend(bend) => &self.fixed_bend_to_handle[bend.index()],
        }
    }
}

impl IndexMut<PrenavmeshNodeIndex> for PrenavnodeToHandleMap {
    fn index_mut(&mut self, prenavnode: PrenavmeshNodeIndex) -> &mut Self::Output {
        match prenavnode {
            PrenavmeshNodeIndex::FixedDot(dot) => &mut self.fixed_dot_to_handle[dot.index()],
            PrenavmeshNodeIndex::FixedBend(bend) => &mut self.fixed_bend_to_handle[bend.index()],
        }
    }
}

#[derive(Clone, Getters)]
pub struct Prenavmesh {
    triangulation: Triangulation<PrenavmeshNodeIndex, PrenavnodeToHandleMap, PrenavmeshWeight, ()>,
    constraints: Vec<PrenavmeshConstraint>,
}

impl Prenavmesh {
    pub fn new(
        layout: &Layout<impl AccessRules>,
        origin: FixedDotIndex,
        destination: FixedDotIndex,
        _options: RouterOptions,
    ) -> Result<Self, NavmeshError> {
        let mut this = Self {
            triangulation: Triangulation::new(PrenavnodeToHandleMap::new(
                layout.drawing().geometry().dot_index_bound(),
                layout.drawing().geometry().bend_index_bound(),
            )),
            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_ref(layout.drawing());

            let Some(primitive_net) = primitive.maybe_net() else {
                continue;
            };

            if node == origin.into()
                || node == destination.into()
                || Some(primitive_net) != maybe_net
            {
                match node {
                    PrimitiveIndex::FixedDot(dot) => {
                        layout
                            .drawing()
                            // TODO: Add `.compounds()` method working on `PrimitiveIndex`.
                            .compounds(GenericIndex::<()>::new(dot.index()))
                            .find(|(label, _)| *label == CompoundEntryLabel::Fillet)
                            .is_some();

                        // Do not add prenavnodes for primitives that have been filleted.
                        // For now, we do this by detecting if the primitive overlaps
                        // a fillet.
                        // TODO: This method is simplistic and will obviously result in
                        // false positives in some cases, so in the future, instead of this,
                        // create a fillet compound type and check for compound membership.
                        if Self::is_fixed_dot_filleted(layout, dot) {
                            continue;
                        }

                        this.triangulation
                            .add_vertex(PrenavmeshWeight::new_from_fixed_dot(layout, dot))?;
                    }
                    PrimitiveIndex::LoneLooseSeg(seg) => {
                        this.add_constraint(PrenavmeshConstraint::new_from_lone_loose_seg(
                            layout, seg,
                        ))?;
                    }
                    PrimitiveIndex::SeqLooseSeg(seg) => {
                        this.add_constraint(PrenavmeshConstraint::new_from_seq_loose_seg(
                            layout, seg,
                        ))?;
                    }
                    PrimitiveIndex::FixedBend(bend) => {
                        this.triangulation
                            .add_vertex(PrenavmeshWeight::new_from_fixed_bend(layout, bend))?;
                    }
                    _ => (),
                }
            }
        }

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

            let Some(primitive_net) = primitive.maybe_net() else {
                continue;
            };

            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 (from_dot, to_dot) = layout.drawing().primitive(seg).joints();

                        if Self::is_fixed_dot_filleted(layout, from_dot)
                            && Self::is_fixed_dot_filleted(layout, to_dot)
                        {
                            continue;
                        }

                        let constraint = PrenavmeshConstraint::new_from_fixed_seg(layout, seg);

                        if !this
                            .triangulation
                            .intersects_constraint(&constraint.0, &constraint.1)
                        {
                            this.add_constraint(constraint);
                        }
                    }
                    _ => (),
                }
            }
        }

        Ok(this)
    }

    fn is_fixed_dot_filleted(layout: &Layout<impl AccessRules>, dot: FixedDotIndex) -> bool {
        layout
            .drawing()
            .compounds(GenericIndex::<()>::new(dot.index()))
            .find(|(label, _)|
            // Fillets fail this test for some reason that I did not investigate, so
            // I added this condition.
                *label == CompoundEntryLabel::Fillet
            // Exclude apices because they may overlap fillets.
                || *label == CompoundEntryLabel::Apex)
            .is_none()
            && layout
                .drawing()
                .overlapees(dot.into())
                .find(|overlapee| {
                    layout
                        .drawing()
                        // TODO: Add `.compounds()` method working on `PrimitiveIndex`.
                        .compounds(GenericIndex::<()>::new(overlapee.2.index()))
                        .find(|(label, _)| *label == CompoundEntryLabel::Fillet)
                        .is_some()
                })
                .is_some()
    }

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