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use specs::{prelude::*, world::Index};
use std::{borrow::Borrow, collections::HashMap};

/// A name that can be looked up later in the [`NameTable`].
///
/// Each [`Name`] should be unique within a [`World`]. Conflicts may mess up the
/// [`NameTable`] bookkeeping and lead to bad lookups.
#[derive(Debug, Clone, PartialEq, Hash, Eq)]
pub struct Name(String);

impl Name {
    pub fn new<S: Into<String>>(name: S) -> Self { Name(name.into()) }

    pub fn as_str(&self) -> &str { &self.0 }
}

impl AsRef<str> for Name {
    fn as_ref(&self) -> &str { self.0.as_ref() }
}

impl Borrow<String> for Name {
    fn borrow(&self) -> &String { &self.0 }
}

impl Borrow<str> for Name {
    fn borrow(&self) -> &str { self.0.as_str() }
}

impl<'a> From<&'a str> for Name {
    fn from(s: &'a str) -> Self { Name::new(s) }
}

impl From<String> for Name {
    fn from(s: String) -> Self { Name::new(s) }
}

impl Component for Name {
    type Storage = FlaggedStorage<Name, HashMapStorage<Name>>;
}

/// A global [`Resource`] for looking up an [`Entity`] using its [`Name`].
#[derive(Debug, Clone, PartialEq, Default)]
pub struct NameTable {
    pub(crate) names: HashMap<Name, Entity>,
}

impl NameTable {
    pub fn get(&self, name: &str) -> Option<Entity> {
        self.names.get(name).copied()
    }

    pub fn iter<'this>(
        &'this self,
    ) -> impl Iterator<Item = (&str, Entity)> + 'this {
        self.names.iter().map(|(name, ent)| (name.as_ref(), *ent))
    }

    pub fn clear(&mut self) { self.names.clear(); }

    pub fn len(&self) -> usize { self.names.len() }

    pub fn is_empty(&self) -> bool { self.names.is_empty() }

    pub fn remove_by_id(&mut self, id: Index) {
        let filter = move |(name, ent): (&Name, &Entity)| {
            if ent.id() == id {
                Some(name.clone())
            } else {
                None
            }
        };

        // OPT: This is super inefficient...
        if let Some(name) = self.names.iter().filter_map(filter).next() {
            self.names.remove(&name);
        }
    }
}