extern crate rand;
use rand::Rng;
use std::rc::Rc;
use std::sync::Arc;
use std::cell::{Cell, RefCell};

/// Generate random structs and enums!
///
/// You shouldn't implement this trait yourself — instead, use the `derive` macro:
/// ```
/// use gen_random_proc_macro::GenRandom;
/// use gen_random::GenRandom;
///
/// #[derive(GenRandom, Debug)]
/// enum MyType {
///     // this variant will be chosen 7 / 10.5 = 2/3 of the time
///     #[prob = 7]
///     Variant1(f64),
///     // this variant will be chosen 3.5 / 10.5 = 1/3 of the time
///     #[prob = 3.5]
///     Variant2 {
///         // bias & scale attributes can be used for fields of type f32/f64.
///         // this makes `a` range from 2 to 6 (as opposed to the default 0 to 1).
///         #[bias = 2.0]
///         #[scale = 4.0]
///         a: f64,
///         // we can even include a randomly-generated MyType inside this MyType!
///         // be careful when doing this or else you might try to generate an infinite struct!
///         b: Box<MyType>
///     }
/// }
///
/// fn main() {
///     let my_value = MyType::gen_thread_random();
///     println!("{my_value:?}");
/// }
/// ```

pub trait GenRandom: Sized {
	/// To allow recursive structs like binary trees,
	/// we provide a `max_depth` functionality.
	/// If your struct isn't recursive, you can use [GenRandom::gen_random] instead.
	/// If `max_depth <= 0` the **first** variant of an `enum` is always chosen
	/// (so make sure `Empty` or whatever comes first).
	/// For `Option<T>`, if `max_depth <= 0`, `None` is always chosen.
	fn gen_random_max_depth(rng: &mut impl Rng, max_depth: isize) -> Self;
	
	/// Generate a random instance of this struct using the given random number generator.
	fn gen_random(rng: &mut impl Rng) -> Self {
		Self::gen_random_max_depth(rng, isize::MAX)
	}
	
	/// Generate a random instance of this struct using `rand::thread_rng()` with a maximum depth.
	fn gen_thread_random_max_depth(max_depth: isize) -> Self {
		let mut thread_rng = rand::thread_rng();
		Self::gen_random_max_depth(&mut thread_rng, max_depth)
	}
	
	/// Generate a random instance of this struct using `rand::thread_rng()`.
	fn gen_thread_random() -> Self {
		Self::gen_thread_random_max_depth(isize::MAX)
	}
}

pub fn gen_random_vec<T: GenRandom>(rng: &mut impl Rng, len: usize) -> Vec<T> {
	(0..len).map(|_| T::gen_random(rng)).collect()
}

pub fn gen_thread_random_vec<T: GenRandom>(len: usize) -> Vec<T> {
	gen_random_vec(&mut rand::thread_rng(), len)
}

impl GenRandom for f32 {
	fn gen_random_max_depth(rng: &mut impl Rng, _depth: isize) -> Self {
		rng.gen_range(0.0..1.0)
	}
}

impl GenRandom for f64 {
	fn gen_random_max_depth(rng: &mut impl Rng, _depth: isize) -> Self {
		rng.gen_range(0.0..1.0)
	}
}

impl<T: GenRandom> GenRandom for Box<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		Box::new(T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for [T; 1] {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		[T::gen_random_max_depth(rng, depth)]
	}
}

impl<T: GenRandom> GenRandom for [T; 2] {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		[T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth)]
	}
}

impl<T: GenRandom> GenRandom for [T; 3] {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		[T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth)]
	}
}

impl<T: GenRandom> GenRandom for [T; 4] {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		[T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth)]
	}
}

impl<T: GenRandom> GenRandom for (T, T) {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		(T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for (T, T, T) {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		(T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for (T, T, T, T) {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		(T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth), T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for Rc<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		Self::new(T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for Arc<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		Self::new(T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for Cell<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		Self::new(T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for RefCell<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		Self::new(T::gen_random_max_depth(rng, depth))
	}
}

impl<T: GenRandom> GenRandom for Option<T> {
	fn gen_random_max_depth(rng: &mut impl Rng, depth: isize) -> Self {
		if depth <= 0 {
			None
		} else if rng.gen_range(0..2) == 0 {
			None
		} else {
			Some(T::gen_random_max_depth(rng, depth))
		}
	}
}


#[cfg(test)]
mod tests {
	extern crate gen_random_proc_macro;
	extern crate rand;
	use super::{gen_thread_random_vec, GenRandom};
	use gen_random_proc_macro::GenRandom;

	#[derive(GenRandom, Debug)]
	enum Test1 {
		#[prob = 0.2]
		A(f32),
		#[prob = 0.8]
		B(Option<f32>),
	}

	#[derive(GenRandom, Debug)]
	#[allow(dead_code)]
	enum Test2 {
		#[prob = 0.1]
		Variant1,
		#[prob = 0.7]
		Variant2 { x: f32, y: f64, z: Test1 },
		#[prob = 0.2]
		Variant3(f32, Box<Test2>),
	}

	#[derive(GenRandom, Debug)]
	enum LinkedList {
		#[prob = 10]
		Empty,
		#[prob = 90]
		Cons(f32, Box<LinkedList>),
	}

	#[derive(GenRandom, Debug)]
	enum BinaryTree {
		#[prob = 1]
		Empty,
		#[prob = 99]
		Node(f64, Box<BinaryTree>, Box<BinaryTree>)
	}

	#[derive(GenRandom, Debug)]
	struct ScaleBias {
		#[bias = 1.0]
		#[scale = 10.0]
		a: f32,
		#[bias = 2.0]
		#[scale = 0.0]
		b: f32,
	}

	#[test]
	fn basic() {
		let tests1: Vec<Test1> = gen_thread_random_vec(10);
		println!("{tests1:?}");
	}

	#[test]
	fn many_types_of_variants() {
		let tests2: Vec<Test2> = gen_thread_random_vec(10);
		println!("{tests2:?}");
	}

	#[test]
	fn linked_list() {
		let ll = LinkedList::gen_thread_random();
		println!("{ll:?}");
	}

	#[test]
	fn scale_bias() {
		let sb: Vec<ScaleBias> = gen_thread_random_vec(10);
		println!("{sb:?}");
		for x in sb.iter() {
			if x.a < 1.0 || x.a > 11.0 {
				panic!("a field should be between 1 and 11; got {}", x.a);
			}
			if x.b != 2.0 {
				panic!("b field should be exactly 2; got {}", x.b);
			}
		}
	}
	
	#[test]
	fn binary_tree_max_depth() {
		let bintree = BinaryTree::gen_thread_random_max_depth(5);
		println!("{bintree:?}");
	}
}