use nalgebra::DVector;
use rustc_hash::FxHashMap;
use slab::Slab;
use std::collections::BTreeSet;
use sycamore::prelude::*;

#[derive(Clone, PartialEq)]
pub struct Element {
    pub id: String,
    pub label: String,
    pub color: [f32; 3],
    pub rep: DVector<f64>,
    pub constraints: BTreeSet<usize>
}

#[derive(Clone)]
pub struct Constraint {
    pub args: (usize, usize),
    pub rep: f64,
    pub active: Signal<bool>
}

// a complete, view-independent description of an assembly
#[derive(Clone)]
pub struct Assembly {
    // elements and constraints
    pub elements: Signal<Slab<Element>>,
    pub constraints: Signal<Slab<Constraint>>,
    
    // indexing
    pub elements_by_id: Signal<FxHashMap<String, usize>>
}

impl Assembly {
    pub fn new() -> Assembly {
        Assembly {
            elements: create_signal(Slab::new()),
            constraints: create_signal(Slab::new()),
            elements_by_id: create_signal(FxHashMap::default())
        }
    }
    
    // insert an element into the assembly without checking whether we already
    // have an element with the same identifier. any element that does have the
    // same identifier will get kicked out of the `elements_by_id` index
    fn insert_element_unchecked(&self, elt: Element) {
        let id = elt.id.clone();
        let key = self.elements.update(|elts| elts.insert(elt));
        self.elements_by_id.update(|elts_by_id| elts_by_id.insert(id, key));
    }
    
    pub fn try_insert_element(&self, elt: Element) -> bool {
        let can_insert = self.elements_by_id.with_untracked(
            |elts_by_id| !elts_by_id.contains_key(&elt.id)
        );
        if can_insert {
            self.insert_element_unchecked(elt);
        }
        can_insert
    }
    
    pub fn insert_new_element(&self) {
        // find the next unused identifier in the default sequence
        let mut id_num = 1;
        let mut id = format!("sphere{}", id_num);
        while self.elements_by_id.with_untracked(
            |elts_by_id| elts_by_id.contains_key(&id)
        ) {
            id_num += 1;
            id = format!("sphere{}", id_num);
        }
        
        // create and insert a new element
        self.insert_element_unchecked(
            Element {
                id: id,
                label: format!("Sphere {}", id_num),
                color: [0.75_f32, 0.75_f32, 0.75_f32],
                rep: DVector::<f64>::from_column_slice(&[0.0, 0.0, 0.0, 0.5, -0.5]),
                constraints: BTreeSet::default()
            }
        );
    }
    
    pub fn insert_constraint(&self, constraint: Constraint) {
        let args = constraint.args;
        let key = self.constraints.update(|csts| csts.insert(constraint));
        self.elements.update(|elts| {
            elts[args.0].constraints.insert(key);
            elts[args.1].constraints.insert(key);
        })
    }
}