use std::marker::PhantomData;

use async_fn_stream::stream;
use futures::future::{LocalBoxFuture, join_all};
use futures::{FutureExt, Stream, StreamExt};
use itertools::Itertools;
use never::Never;
use orchid_base::error::{OrcErrv, OrcRes, Reporter};
use orchid_base::id_store::IdStore;
use orchid_base::interner::{Interner, Tok};
use orchid_base::location::SrcRange;
use orchid_base::match_mapping;
use orchid_base::name::Sym;
use orchid_base::parse::{Comment, ParseCtx, Snippet};
use orchid_base::reqnot::Requester;
use orchid_base::tree::{TokTree, Token, ttv_into_api};

use crate::api;
use crate::context::{SysCtxEntry, ctx, i};
use crate::conv::ToExpr;
use crate::expr::Expr;
use crate::gen_expr::GExpr;
use crate::tree::{GenTok, GenTokTree};

pub type PTok = Token<Expr, Never>;
pub type PTokTree = TokTree<Expr, Never>;
pub type PSnippet<'a> = Snippet<'a, Expr, Never>;

pub fn p_tok2gen(tok: PTok) -> GenTok {
	match_mapping!(tok, PTok => GenTok {
		Comment(s), Name(n), BR, Handle(ex), Bottom(err),
		LambdaHead(arg => Box::new(p_tree2gen(*arg))),
		NS(n, arg => Box::new(p_tree2gen(*arg))),
		S(p, body () p_v2gen),
	} {
		PTok::NewExpr(never) => match never {}
	})
}
pub fn p_tree2gen(tree: PTokTree) -> GenTokTree {
	TokTree { tok: p_tok2gen(tree.tok), sr: tree.sr }
}
pub fn p_v2gen(v: impl IntoIterator<Item = PTokTree>) -> Vec<GenTokTree> {
	v.into_iter().map(p_tree2gen).collect_vec()
}

pub trait Parser: Send + Sync + Sized + Default + 'static {
	const LINE_HEAD: &'static str;
	fn parse<'a>(
		ctx: ParsCtx<'a>,
		exported: bool,
		comments: Vec<Comment>,
		line: PSnippet<'a>,
	) -> impl Future<Output = OrcRes<Vec<ParsedLine>>> + 'a;
}

pub trait DynParser: Send + Sync + 'static {
	fn line_head(&self) -> &'static str;
	fn parse<'a>(
		&self,
		ctx: ParsCtx<'a>,
		exported: bool,
		comments: Vec<Comment>,
		line: PSnippet<'a>,
	) -> LocalBoxFuture<'a, OrcRes<Vec<ParsedLine>>>;
}

impl<T: Parser> DynParser for T {
	fn line_head(&self) -> &'static str { Self::LINE_HEAD }
	fn parse<'a>(
		&self,
		ctx: ParsCtx<'a>,
		exported: bool,
		comments: Vec<Comment>,
		line: PSnippet<'a>,
	) -> LocalBoxFuture<'a, OrcRes<Vec<ParsedLine>>> {
		Box::pin(async move { Self::parse(ctx, exported, comments, line).await })
	}
}

pub type ParserObj = &'static dyn DynParser;

pub struct ParsCtx<'a> {
	_parse: PhantomData<&'a mut ()>,
	module: Sym,
	reporter: &'a Reporter,
	i: Interner,
}
impl<'a> ParsCtx<'a> {
	pub(crate) fn new(module: Sym, reporter: &'a Reporter) -> Self {
		Self { _parse: PhantomData, module, reporter, i: i() }
	}
	pub fn module(&self) -> Sym { self.module.clone() }
}
impl ParseCtx for ParsCtx<'_> {
	fn i(&self) -> &Interner { &self.i }
	fn rep(&self) -> &Reporter { self.reporter }
}

type BoxConstCallback = Box<dyn FnOnce(ConstCtx) -> LocalBoxFuture<'static, GExpr>>;

#[derive(Default)]
pub(crate) struct ParsedConstCtxEntry {
	pub(crate) consts: IdStore<BoxConstCallback>,
}
impl SysCtxEntry for ParsedConstCtxEntry {}

pub struct ParsedLine {
	pub sr: SrcRange,
	pub comments: Vec<Comment>,
	pub kind: ParsedLineKind,
}
impl ParsedLine {
	pub fn cnst<'a, R: ToExpr + 'static, F: AsyncFnOnce(ConstCtx) -> R + 'static>(
		sr: &SrcRange,
		comments: impl IntoIterator<Item = &'a Comment>,
		exported: bool,
		name: Tok<String>,
		f: F,
	) -> Self {
		let cb = Box::new(|ctx| async move { f(ctx).await.to_gen().await }.boxed_local());
		let kind = ParsedLineKind::Mem(ParsedMem { name, exported, kind: ParsedMemKind::Const(cb) });
		let comments = comments.into_iter().cloned().collect();
		ParsedLine { comments, sr: sr.clone(), kind }
	}
	pub fn module<'a>(
		sr: &SrcRange,
		comments: impl IntoIterator<Item = &'a Comment>,
		exported: bool,
		name: &Tok<String>,
		use_prelude: bool,
		lines: impl IntoIterator<Item = ParsedLine>,
	) -> Self {
		let mem_kind = ParsedMemKind::Mod { lines: lines.into_iter().collect(), use_prelude };
		let line_kind = ParsedLineKind::Mem(ParsedMem { name: name.clone(), exported, kind: mem_kind });
		let comments = comments.into_iter().cloned().collect();
		ParsedLine { comments, sr: sr.clone(), kind: line_kind }
	}
	pub async fn into_api(self) -> api::ParsedLine {
		api::ParsedLine {
			comments: self.comments.into_iter().map(|c| c.to_api()).collect(),
			source_range: self.sr.to_api(),
			kind: match self.kind {
				ParsedLineKind::Mem(mem) => api::ParsedLineKind::Member(api::ParsedMember {
					name: mem.name.to_api(),
					exported: mem.exported,
					kind: match mem.kind {
						ParsedMemKind::Const(cb) => api::ParsedMemberKind::Constant(api::ParsedConstId(
							ctx().get_or_default::<ParsedConstCtxEntry>().consts.add(cb).id(),
						)),
						ParsedMemKind::Mod { lines, use_prelude } => api::ParsedMemberKind::Module {
							lines: linev_into_api(lines).boxed_local().await,
							use_prelude,
						},
					},
				}),
				ParsedLineKind::Rec(tv) =>
					api::ParsedLineKind::Recursive(ttv_into_api(tv, &mut (), &mut ()).await),
			},
		}
	}
}

pub(crate) async fn linev_into_api(v: Vec<ParsedLine>) -> Vec<api::ParsedLine> {
	join_all(v.into_iter().map(|l| l.into_api())).await
}

pub enum ParsedLineKind {
	Mem(ParsedMem),
	Rec(Vec<GenTokTree>),
}

pub struct ParsedMem {
	pub name: Tok<String>,
	pub exported: bool,
	pub kind: ParsedMemKind,
}

pub enum ParsedMemKind {
	Const(BoxConstCallback),
	Mod { lines: Vec<ParsedLine>, use_prelude: bool },
}

#[derive(Clone)]
pub struct ConstCtx {
	constid: api::ParsedConstId,
}
impl ConstCtx {
	pub fn names<'b>(
		&'b self,
		names: impl IntoIterator<Item = &'b Sym> + 'b,
	) -> impl Stream<Item = OrcRes<Sym>> + 'b {
		let resolve_names = api::ResolveNames {
			constid: self.constid,
			sys: ctx().sys_id(),
			names: names.into_iter().map(|n| n.to_api()).collect_vec(),
		};
		stream(async |mut cx| {
			for name_opt in ctx().reqnot().request(resolve_names).await {
				cx.emit(match name_opt {
					Err(e) => Err(OrcErrv::from_api(&e, &i()).await),
					Ok(name) => Ok(Sym::from_api(name, &i()).await),
				})
				.await
			}
		})
	}
	pub async fn names_n<const N: usize>(&self, names: [&Sym; N]) -> [OrcRes<Sym>; N] {
		self.names(names).collect::<Vec<_>>().await.try_into().expect("Lengths must match")
	}
}

pub(crate) async fn get_const(id: api::ParsedConstId) -> GExpr {
	let cb = (ctx().get_or_default::<ParsedConstCtxEntry>().consts.get(id.0))
		.expect("Bad ID or double read of parsed const")
		.remove();
	cb(ConstCtx { constid: id }).await
}