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use std::sync::Arc;

use gramatika::{Parse, ParseStreamer, Span, Spanned, SpannedError, Token as _};

use crate::{
	common::{AttributeList, TypeDecl},
	stmt::BlockStmt,
	token::{brace, keyword, operator, punct, Token, TokenKind},
	ParseStream,
};

use super::Decl;

#[derive(Clone, DebugLisp)]
pub struct FunctionDecl {
	pub attributes: Option<AttributeList>,
	pub storage: Token,
	pub storage_modifier: Option<Token>,
	pub name: Token,
	pub params: Arc<[Decl]>,
	pub return_ty: Option<TypeDecl>,
	pub body: BlockStmt,
}

#[derive(Clone, DebugLisp)]
pub struct ParamDecl {
	pub attributes: Option<AttributeList>,
	pub name: Token,
	pub ty: TypeDecl,
}

impl Parse for FunctionDecl {
	type Stream = ParseStream;

	fn parse(input: &mut Self::Stream) -> gramatika::Result<Self> {
		use TokenKind::*;

		let storage = input.consume(keyword![fn])?;
		let storage_modifier = if input.check(operator![<]) {
			input.consume(operator![<])?;
			let modifier = input.consume_kind(TokenKind::Keyword)?;
			input.consume(operator![>])?;

			Some(modifier)
		} else {
			None
		};
		let name = input.consume_as(TokenKind::Ident, Token::function)?;
		input.consume(brace!["("])?;

		let mut params = vec![];
		while !input.check(brace![")"]) {
			match input.peek() {
				Some(token) => match token.as_matchable() {
					(Punct, "@", _) | (Ident, _, _) => {
						let param = input.parse::<ParamDecl>()?;
						params.push(Decl::Param(param));
					}
					(Punct, ",", _) => input.discard(),
					(_, _, span) => {
						return Err(SpannedError {
							message: "Expected parameter, `,`, or `)`".into(),
							span: Some(span),
							source: input.source(),
						})
					}
				},
				None => {
					return Err(SpannedError {
						message: "Unexpected end of input".into(),
						source: input.source(),
						span: None,
					})
				}
			};
		}

		input.consume(brace![")"])?;
		let return_ty = if input.check(operator![->]) {
			Some(input.parse::<TypeDecl>()?)
		} else {
			None
		};

		let body = input.parse::<BlockStmt>()?;

		Ok(Self {
			attributes: None,
			storage,
			storage_modifier,
			name,
			params: params.into(),
			return_ty,
			body,
		})
	}
}

impl Spanned for FunctionDecl {
	fn span(&self) -> Span {
		self.storage.span().through(self.body.brace_close.span())
	}
}

impl Parse for ParamDecl {
	type Stream = ParseStream;

	fn parse(input: &mut Self::Stream) -> gramatika::Result<Self> {
		let attributes = if input.check(punct!["@"]) {
			Some(input.parse::<AttributeList>()?)
		} else {
			None
		};
		let name = input.consume_kind(TokenKind::Ident)?;
		let ty = input.parse::<TypeDecl>()?;

		Ok(Self {
			attributes,
			name,
			ty,
		})
	}
}

impl Spanned for ParamDecl {
	fn span(&self) -> Span {
		let span_start = self
			.attributes
			.as_ref()
			.and_then(|attrs| attrs.attributes.first().map(|attr| &attr.at_sign))
			.unwrap_or(&self.name)
			.span();

		span_start.through(self.ty.span())
	}
}