use std::{collections::HashMap, hash::Hash};


use std::ops::{
	Mul, Div,
	MulAssign, DivAssign
};

#[derive(Debug)]
#[derive(Hash)]
#[derive(Eq, PartialEq)]
#[derive(Copy, Clone)]
pub enum BaseUnit {
	Second,
	Meter,
	Kilogram,
	Ampere,
	Kelvin,
	Mole,
	Candela
}

#[derive(Debug)]
#[derive(Clone)]
pub struct Unit {
	// Unit, power.
	pub val: HashMap<BaseUnit, f64>
}


impl ToString for Unit {
	fn to_string(&self) -> String {
		format!("{:?}", self)
	}
}


impl Unit {

	pub fn new() -> Unit {
		return Unit{
			val: HashMap::new()
		}
	}

	pub fn unitless(&self) -> bool { self.val.len() == 0 }

	pub fn insert(&mut self, u: BaseUnit, p: f64) {
		match self.val.get_mut(&u) {
			Some(i) => {
				let n = *i + p;

				if n == 0f64 {
					self.val.remove(&u);
				} else { *i = n; }
			},
			None => { self.val.insert(u, p); }
		};
	}

	pub fn pow(&mut self, pwr: f64) {
		for (_, p) in &mut self.val {
			*p *= pwr;
		}
	}

}


impl PartialEq for Unit {
	fn eq(&self, other: &Self) -> bool {
		for (u, p) in &other.val {
			match self.val.get(u) {
				Some(i) => { if i != p { return false; } },
				None => { return false; }
			};
		}
		return true;
	}
}

impl Mul for Unit {
	type Output = Self;

	fn mul(self, other: Self) -> Self::Output {
		let mut o = self.clone();
		for (u, p) in &other.val { o.insert(*u, *p); }
		return o;
	}
}

impl MulAssign for Unit where {
	fn mul_assign(&mut self, other: Self) {
		for (u, p) in &other.val { self.insert(*u, *p); }
	}
}

impl Div for Unit {
	type Output = Self;

	fn div(self, other: Self) -> Self::Output {
		let mut o = self.clone();
		for (u, p) in &other.val { o.insert(*u, -*p); }
		return o;
	}
}

impl DivAssign for Unit where {
	fn div_assign(&mut self, other: Self) {
		for (u, p) in &other.val { self.insert(*u, -*p); }
	}
}