use orchid_api_derive::Coding;
use orchid_base::{FmtUnit, OrcRes, sym};
use orchid_extension::gen_expr::GExpr;
use orchid_extension::tree::{GenMember, cnst, comments, fun, prefix};
use orchid_extension::{Atomic, Expr, TAtom, ThinAtom, ThinVariant, ToExpr, TryFromExpr};

#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, Coding)]
pub struct Bool(pub bool);
impl Atomic for Bool {
	type Variant = ThinVariant;
	type Data = Self;
}
impl ThinAtom for Bool {
	async fn print(&self) -> FmtUnit { self.0.to_string().into() }
}
impl TryFromExpr for Bool {
	async fn try_from_expr(expr: Expr) -> OrcRes<Self> {
		match TAtom::<Bool>::downcast(expr.handle()).await {
			Err(e) => Err(e.mk_err().await),
			Ok(atom) => Ok(atom.value),
		}
	}
}
impl ToExpr for Bool {
	async fn to_gen(self) -> GExpr {
		if self.0 { sym!(std::true) } else { sym!(std::false) }.to_gen().await
	}
}

pub fn gen_bool_lib() -> Vec<GenMember> {
	prefix("std", [
		comments(
			[
				"Returns the second argument if the bool is true, the third argument otherwise",
				"|type: Bool -> T -> T -> T|",
			],
			fun(true, "ifthenelse", async |Bool(b): Bool, t: Expr, f: Expr| if b { t } else { f }),
		),
		cnst(true, "true", Bool(true)),
		cnst(true, "false", Bool(false)),
	])
}