use std::hash::Hash;

use boxcar;
use dashmap::DashMap;

pub struct Interner<V, I>
where
	V: Copy + Eq + Hash,
	I: Copy + Into<usize>,
{
	map:   DashMap<V, I>,
	store: boxcar::Vec<V>,
}

impl<V, I> Interner<V, I>
where
	V: Copy + Eq + Hash,
	I: Copy + From<usize> + Into<usize>,
{
	pub fn new() -> Self {
		return Interner {
			map:   DashMap::new(),
			store: boxcar::Vec::with_capacity(1024),
		};
	}

	pub fn get(&self, key: I) -> V {
		return self.store[key.into()];
	}

	pub fn intern(&self, value: V) -> I {
		if let Some(key) = self.map.get(&value) {
			return *key;
		}
		let key = self.store.push(value).into();
		self.map.insert(value, key);
		return key;
	}
}

#[cfg(test)]
mod tests {
	use super::Interner;
	use crate::unistr::UniStr;

	#[test]
	fn test_interner_intern() {
		let xs = [UniStr("fishi"), UniStr("fishi"), UniStr("fishᵢ")];
		let y = UniStr("andy");

		let mut interner = Interner::<_, usize>::new();
		for i in 0..xs.len() {
			for j in i..xs.len() {
				assert_eq!(interner.intern(xs[i]), interner.intern(xs[j]));
			}
		}
		for i in 0..xs.len() {
			assert_ne!(interner.intern(y), interner.intern(xs[i]));
		}
	}

	#[test]
	fn test_interner_gets_first_inserted() {
		let mut interner = Interner::<_, usize>::new();
		let xs = [UniStr("fishi"), UniStr("fishi"), UniStr("fishᵢ")];
		let ys = xs.iter().map(|&x| interner.intern(x)).collect::<Vec<_>>();

		for i in 0..ys.len() {
			assert_eq!(interner.get(ys[i]), xs[0]);
		}
	}
}