use std::{
	collections::BTreeMap,
	rc::Rc,
};

#[derive (Clone, Debug, Hash, PartialEq)]
pub struct BogusClosure {
	pub idx: usize,
	pub upvalues: Vec <Value>,
}

#[derive (Clone, Debug, PartialEq)]
pub enum Value {
	Nil,
	Boolean (bool),
	Float (f64),
	Integer (i64),
	String (Rc <String>),
	
	// These are all bogus, I haven't figured out how to implement
	// tables and function pointers yet
	
	BogusArg (Rc <Vec <String>>),
	BogusClosure (Rc <BogusClosure>),
	BogusEnv (Rc <BTreeMap <String, Value>>),
	BogusPrint,
}

impl Default for Value {
	fn default () -> Self {
		Self::Nil
	}
}

impl From <String> for Value {
	fn from (x: String) -> Self {
		Self::String (x.into ())
	}
}

impl From <&str> for Value {
	fn from (x: &str) -> Self {
		Self::from (String::from (x))
	}
}

impl From <i32> for Value {
	fn from (x: i32) -> Self {
		Self::Integer (i64::try_from (x).unwrap ())
	}
}

impl From <f64> for Value {
	fn from (x: f64) -> Self {
		Self::Float (x)
	}
}

impl std::hash::Hash for Value {
	fn hash <H: std::hash::Hasher> (&self, state: &mut H) {
		// Per https://doc.rust-lang.org/std/hash/trait.Hash.html#prefix-collisions
		[0xff].hash (state);
		
		match self {
			// TODO: Weaken to a Lua error
			Self::Nil => panic! ("can't hash a nil value"),
			Self::Boolean (x) => x.hash (state),
			Self::Float (x) => x.to_ne_bytes ().hash (state),
			Self::Integer (x) => x.hash (state),
			Self::String (x) => x.as_ptr ().hash (state),
			Self::BogusArg (_) => panic! ("can't hash Bogus values"),
			Self::BogusClosure (_) => panic! ("can't hash Bogus values"),
			Self::BogusEnv (_) => panic! ("can't hash Bogus values"),
			Self::BogusPrint => panic! ("can't hash Bogus values"),
		}
	}
}

impl Value {
	pub fn as_float (&self) -> Option <f64> {
		match self {
			Self::Float (x) => Some (*x),
			// FloatToInt isn't stable yet, so only ints in i32 space can practically be used for now
			Self::Integer (x) => f64::try_from (i32::try_from (*x).ok ()?).ok (),
			_ => None,
		}
	}
	
	pub fn is_truthy (&self) -> bool {
		// And this is something Lua does better than JS and Python.
		
		match self {
			Value::Nil => false,
			Value::Boolean (false) => false,
			_ => true,
		}
	}
	
	pub fn take (&mut self) -> Self {
		let mut x = Value::Nil;
		std::mem::swap (self, &mut x);
		x
	}
}