orchid/orchid-std/src/macros/match_macros.rs

use std::borrow::Cow;

use async_fn_stream::stream;
use futures::future::join_all;
use futures::{Stream, StreamExt, stream};
use never::Never;
use orchid_api::ExprTicket;
use orchid_api_derive::Coding;
use orchid_base::error::{OrcRes, mk_errv};
use orchid_base::format::fmt;
use orchid_base::name::Sym;
use orchid_base::sym;
use orchid_extension::atom::{Atomic, TAtom};
use orchid_extension::atom_owned::{OwnedAtom, OwnedVariant, own};
use orchid_extension::context::i;
use orchid_extension::conv::ToExpr;
use orchid_extension::coroutine_exec::{ExecHandle, exec};
use orchid_extension::expr::{Expr, ExprHandle};
use orchid_extension::gen_expr::{GExpr, arg, bot, call, lambda, sym_ref};
use orchid_extension::tree::{GenMember, fun, prefix};

use crate::macros::resolve::resolve;
use crate::macros::utils::{build_macro, mactree, mactreev};
use crate::std::reflection::sym_atom::SymAtom;
use crate::std::tuple::Tuple;
use crate::{HomoTpl, MacTok, MacTree, OrcOpt, Tpl, UntypedTuple, api};

#[derive(Clone, Coding)]
pub struct MatcherData {
	keys: Vec<api::TStrv>,
	matcher: ExprTicket,
}
impl MatcherData {
	async fn matcher(&self) -> Expr { Expr::from_handle(ExprHandle::from_ticket(self.matcher).await) }
	pub async fn run_matcher(
		&self,
		h: &mut ExecHandle<'_>,
		val: impl ToExpr,
	) -> OrcRes<OrcOpt<HomoTpl<Expr>>> {
		h.exec::<OrcOpt<HomoTpl<Expr>>>(call(self.matcher().await.to_gen().await, [val.to_gen().await]))
			.await
	}
	pub fn keys(&self) -> impl Stream<Item = Sym> {
		stream(async |mut h| {
			for tk in &self.keys {
				h.emit(Sym::from_api(*tk, &i()).await).await
			}
		})
	}
}
#[derive(Clone)]
pub struct MatcherAtom {
	/// The names that subresults may be bound to
	pub(super) keys: Vec<Sym>,
	/// Takes the value-to-be-matched, returns an `option (tuple T1..TN)` of the
	/// subresults to be bound to the names returned by [Self::keys]
	pub(super) matcher: Expr,
}
impl Atomic for MatcherAtom {
	type Data = MatcherData;
	type Variant = OwnedVariant;
}
impl OwnedAtom for MatcherAtom {
	type Refs = Never;
	async fn val(&self) -> std::borrow::Cow<'_, Self::Data> {
		Cow::Owned(MatcherData {
			keys: self.keys.iter().map(|t| t.to_api()).collect(),
			matcher: self.matcher.handle().ticket(),
		})
	}
}

pub async fn gen_match_macro_lib() -> Vec<GenMember> {
	prefix("pattern", [
		fun(
			true,
			"match_one",
			async |mat: TAtom<MatcherAtom>, value: Expr, then: Expr, default: Expr| {
				exec(async move |mut h| match mat.run_matcher(&mut h, value).await? {
					OrcOpt(Some(values)) =>
						Ok(call(then.to_gen().await, join_all(values.0.into_iter().map(|x| x.to_gen())).await)),
					OrcOpt(None) => Ok(default.to_gen().await),
				})
				.await
			},
		),
		fun(true, "matcher", async |names: HomoTpl<TAtom<SymAtom>>, matcher: Expr| MatcherAtom {
			keys: join_all(names.0.iter().map(async |atm| Sym::from_api(atm.0, &i()).await)).await,
			matcher,
		}),
		build_macro(None, ["match", "match_rule", "_row", "=>"])
			.rule(mactreev!("pattern::match" { "..$" rules 0 }), [async |[rules]| {
				exec(async move |mut h| {
					let rule_lines = h
						.exec::<TAtom<Tuple>>(call(sym_ref(sym!(macros::resolve; i())), [
							mactree!(macros::common::semi_list "push" rules.clone();).to_gen().await,
						]))
						.await?;
					let mut rule_atoms = Vec::<(TAtom<MatcherAtom>, Expr)>::new();
					for line_exprh in rule_lines.iter() {
						let line_mac = h
							.exec::<TAtom<MacTree>>(Expr::from_handle(ExprHandle::from_ticket(*line_exprh).await))
							.await?;
						let Tpl((matcher, body)) = h
							.exec(call(sym_ref(sym!(macros::resolve; i())), [
								mactree!(pattern::_row "push" own(&line_mac).await ;).to_gen().await,
							]))
							.await?;
						rule_atoms.push((matcher, body));
					}
					let base_case = lambda(0, [bot(mk_errv(
						i().i("No branches match").await,
						"None of the pattern provided matches this value",
						[rules.pos()],
					))]);
					let match_expr = stream::iter(rule_atoms.into_iter().rev())
						.fold(base_case, async |tail, (mat, body)| {
							lambda(0, [call(sym_ref(sym!(pattern::match_one; i())), [
								mat.to_gen().await,
								arg(0),
								body.to_gen().await,
								call(tail, [arg(0)]),
							])])
						})
						.await;
					Ok(match_expr)
				})
				.await
			}])
			.rule(mactreev!(pattern::match_rule (( "...$" pattern 0 ))), [async |[pattern]| {
				resolve(mactree!(pattern::match_rule "push" pattern; )).await
			}])
			.rule(mactreev!(pattern::_row ( "...$" pattern 0 pattern::=> "...$" value 1 )), [
				async |[pattern, mut value]| {
					exec(async move |mut h| -> OrcRes<Tpl<(TAtom<MatcherAtom>, GExpr)>> {
						let Ok(pat) = h
							.exec::<TAtom<MatcherAtom>>(call(sym_ref(sym!(macros::resolve; i())), [
								mactree!(pattern::match_rule "push" pattern.clone();).to_gen().await,
							]))
							.await
						else {
							return Err(mk_errv(
								i().i("Invalid pattern").await,
								format!("Could not parse {} as a match pattern", fmt(&pattern, &i()).await),
								[pattern.pos()],
							));
						};
						value = (pat.keys())
							.fold(value, async |value, name| mactree!("l_" name; ( "push" value ; )))
							.await;
						Ok(Tpl((pat, resolve(value).await)))
					})
					.await
				},
			])
			.finish(),
		fun(true, "ref_body", async |val| OrcOpt(Some(UntypedTuple(vec![val])))),
		build_macro(None, ["ref"])
			.rule(mactreev!(pattern::match_rule(pattern::ref "$" name)), [async |[name]| {
				let MacTok::Name(name) = name.tok() else {
					return Err(mk_errv(
						i().i("pattern 'ref' requires a name to bind to").await,
						format!(
							"'ref' was interpreted as a binding matcher, \
							but it was followed by {} instead of a name",
							fmt(&name, &i()).await
						),
						[name.pos()],
					));
				};
				Ok(MatcherAtom {
					keys: vec![name.clone()],
					matcher: sym_ref(sym!(pattern::ref_body; i())).to_expr().await,
				})
			}])
			.finish(),
	])
}