use super::*;
use common::{
    terrain::Block,
    store::{Id, Store},
};
use vek::*;

pub enum Primitive {
    Empty, // Placeholder

    // Shapes
    Aabb(Aabb<i32>),
    Pyramid { aabb: Aabb<i32>, inset: i32 },

    // Combinators
    And(Id<Primitive>, Id<Primitive>),
    Or(Id<Primitive>, Id<Primitive>),
    Xor(Id<Primitive>, Id<Primitive>),
}

pub struct Fill {
    pub prim: Id<Primitive>,
    pub block: Block,
}

impl Fill {
    fn contains_at(&self, tree: &Store<Primitive>, prim: Id<Primitive>, pos: Vec3<i32>) -> bool {
        // Custom closure because vek's impl of `contains_point` is inclusive :(
        let aabb_contains = |aabb: Aabb<i32>, pos: Vec3<i32>| (aabb.min.x..aabb.max.x).contains(&pos.x)
            && (aabb.min.y..aabb.max.y).contains(&pos.y)
            && (aabb.min.z..aabb.max.z).contains(&pos.z);

        match &tree[prim] {
            Primitive::Empty => false,

            Primitive::Aabb(aabb) => aabb_contains(*aabb, pos),
            Primitive::Pyramid { aabb, inset } => {
                let inset = (*inset).max(aabb.size().reduce_min());
                let inner = Aabr { min: aabb.min.xy() - 1 + inset, max: aabb.max.xy() - inset };
                aabb_contains(*aabb, pos) && (inner.projected_point(pos.xy()) - pos.xy())
                    .map(|e| e.abs())
                    .reduce_max() as f32 / (inset as f32) < 1.0 - ((pos.z - aabb.min.z) as f32 + 0.5) / (aabb.max.z - aabb.min.z) as f32
            },

            Primitive::And(a, b) => self.contains_at(tree, *a, pos) && self.contains_at(tree, *b, pos),
            Primitive::Or(a, b) => self.contains_at(tree, *a, pos) || self.contains_at(tree, *b, pos),
            Primitive::Xor(a, b) => self.contains_at(tree, *a, pos) ^ self.contains_at(tree, *b, pos),
        }
    }

    pub fn sample_at(&self, tree: &Store<Primitive>, pos: Vec3<i32>) -> Option<Block> {
        Some(self.block).filter(|_| self.contains_at(tree, self.prim, pos))
    }

    fn get_bounds_inner(&self, tree: &Store<Primitive>, prim: Id<Primitive>) -> Option<Aabb<i32>> {
        fn or_zip_with<T, F: FnOnce(T, T) -> T>(a: Option<T>, b: Option<T>, f: F) -> Option<T> {
            match (a, b) {
                (Some(a), Some(b)) => Some(f(a, b)),
                (Some(a), _) => Some(a),
                (_, b) => b,
            }
        }

        Some(match &tree[prim] {
            Primitive::Empty => return None,
            Primitive::Aabb(aabb) => *aabb,
            Primitive::Pyramid { aabb, .. } => *aabb,
            Primitive::And(a, b) => or_zip_with(self.get_bounds_inner(tree, *a), self.get_bounds_inner(tree, *b), |a, b| a.intersection(b))?,
            Primitive::Or(a, b) | Primitive::Xor(a, b) =>
                or_zip_with(self.get_bounds_inner(tree, *a), self.get_bounds_inner(tree, *b), |a, b| a.union(b))?,
        })
    }

    pub fn get_bounds(&self, tree: &Store<Primitive>) -> Aabb<i32> {
        self.get_bounds_inner(tree, self.prim).unwrap_or_else(|| Aabb::new_empty(Vec3::zero()))
    }
}

pub trait Structure {
    fn render<F: FnMut(Primitive) -> Id<Primitive>, G: FnMut(Fill)>(
        &self,
        site: &Site,
        prim: F,
        fill: G,
    ) {}

    // Generate a primitive tree and fills for this structure
    fn render_collect(&self, site: &Site) -> (Store<Primitive>, Vec<Fill>) {
        let mut tree = Store::default();
        let mut fills = Vec::new();
        let root = self.render(site, |p| tree.insert(p), |f| fills.push(f));
        (tree, fills)
    }
}