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use crate::counters::Counters;
use crate::geometry::{self, HGrid, HGridEntry, ParticlesContacts};
use crate::math::Real;
use crate::object::Boundary;
use crate::object::Fluid;

/// Structure responsible for computing and grouping all the contact between fluid and boundary particles.
pub struct ContactManager {
    /// All contacts detected between pairs of fluid partices.
    pub fluid_fluid_contacts: Vec<ParticlesContacts>,
    /// All contacts detected between a fluid particle and a boundary particle.
    pub fluid_boundary_contacts: Vec<ParticlesContacts>,
    /// All contacts detected between two boundary particles.
    pub boundary_boundary_contacts: Vec<ParticlesContacts>,
}

impl ContactManager {
    /// Create a new contact manager.
    pub fn new() -> Self {
        Self {
            fluid_fluid_contacts: Vec::new(),
            fluid_boundary_contacts: Vec::new(),
            boundary_boundary_contacts: Vec::new(),
        }
    }

    /// The total number of contacts detected by this manager.
    ///
    /// Note that there will be two contact for each pair of distinct particles.
    pub fn ncontacts(&self) -> usize {
        self.fluid_fluid_contacts
            .iter()
            .map(|c| c.len())
            .sum::<usize>()
            + self
                .fluid_boundary_contacts
                .iter()
                .map(|c| c.len())
                .sum::<usize>()
            + self
                .boundary_boundary_contacts
                .iter()
                .map(|c| c.len())
                .sum::<usize>()
    }

    /// Computes all the contacts between the particles inserted on the provided spacial grid.
    pub fn update_contacts(
        &mut self,
        counters: &mut Counters,
        h: Real,
        fluids: &[Fluid],
        boundaries: &[Boundary],
        hgrid: &HGrid<HGridEntry>,
    ) {
        geometry::compute_contacts(
            counters,
            h,
            &fluids,
            &boundaries,
            &mut self.fluid_fluid_contacts,
            &mut self.fluid_boundary_contacts,
            &mut self.boundary_boundary_contacts,
            hgrid,
        );
    }
}