ableos_userland/programs/aidl/src/parser.rs

use logos::{Logos, SpannedIter};

use crate::{
    ast::{IDLModule, Item, ItemInterface, ItemType, UseDecl},
    lexer::{Span, Spanned, Token, Ident},
};
use std::{
    iter::{Iterator, Peekable, Filter},
    ops::Range,
};

type Wtf<'a> = Peekable<
        Filter<SpannedIter<'a, Token>, Box<dyn Fn(&(Result<Token, ()>, Range<usize>)) -> bool>>,
    >;

struct TokenIterator<'a> {
    spanned: Wtf<'a>,
}

fn token_is_not_comment((ref a, ..): &(Result<Token, ()>, Range<usize>)) -> bool {
    !matches!(a, Err(_) | Ok(Token::Comment(..)))
}

impl<'a> TokenIterator<'a> {
    pub fn new(src: &'a str) -> Self {
        let spanned = Token::lexer(src)
            .spanned()
            .filter(
                Box::new(token_is_not_comment) as Box<dyn Fn(&(Result<Token, ()>, Range<usize>)) -> bool>,
            )
            .peekable();

        Self { spanned }
    }
    pub fn next(&mut self) -> Option<Spanned<Token>> {
        let nxt = self
            .spanned
            .next()
            .and_then(|(token, span)| Some(Spanned(token.ok()?, Span(span))));
        println!("[NEXT] {:#?}", nxt);
        nxt
    }

    pub fn peek(&mut self) -> Option<Spanned<&Token>> {
        let peek = self
            .spanned
            .peek()
            .and_then(|(token, span)| Some(Spanned(token.as_ref().ok()?, Span(span.clone()))));
        println!("[PEEK] {:#?}", peek);
        peek
    }
}

pub struct Parser<'a> {
    tokens: TokenIterator<'a>,
}

impl<'a> Parser<'a> {
    pub fn new(src: &'a str) -> Self {
        Self {
            tokens: TokenIterator::new(src),
        }
    }

    fn get_real(&mut self, matcher: impl Fn(&Token) -> bool) -> Option<Spanned<Token>> {
        if matcher(self.tokens.peek()?.0) {
            self.tokens.next()
        } else {
            None
        }
    }

    fn semi(&mut self) -> Option<Span> {
        Some(self.get_real(|token| matches!(token, Token::Semicolon))?.1)
    }

    fn ask_ident(&mut self) -> Option<Spanned<String>> {
        Some(crate::unwrap_match!(
            self.get_real(|token| matches!(token, Token::Ident(Ident::Other(_))))?,
            Spanned(Token::Ident(Ident::Other(ident)), span) =>
            Spanned(ident, span)
        ))
    }

    fn ask_interface(&mut self) -> Option<Spanned<ItemInterface>> {
        let Spanned(_, kSp) =
            self.get_real(|token| matches!(token, Token::Ident(Ident::Interface)))?;
        let Spanned(ident, iSp) = self.ask_ident()?;

        Some(Spanned::new(
            ItemInterface {
                name: ident,
                functions: vec![],
            },
            [kSp, iSp, self.semi()?],
        ))
    }

    fn ask_typealias(&mut self) -> Option<Spanned<ItemType>> {
        let Spanned(_, kSp) =
            self.get_real(|token| matches!(token, Token::Ident(Ident::Type)))?;
        let Spanned(name, nSp) = self.ask_ident()?;

        let Spanned(_, eqSp) = self.get_real(|token| matches!(token, Token::Equals))?;
        let Spanned(referree, rSp) = self.ask_ident()?;

        Some(Spanned::new(
            ItemType { name, referree },
            [kSp, nSp, eqSp, rSp, self.semi()?],
        ))
    }

    fn ask_item(&mut self) -> Option<Spanned<Item>> {
        Some(match self.tokens.peek()?.0 {
            Token::Ident(Ident::Other(_)) => None?,
            Token::Ident(keyword) => match keyword {
                Ident::Interface => self.ask_interface()?.map(Item::Interface),
                Ident::Type => self.ask_typealias()?.map(Item::Type),
                _ => None?,
            },
            _ => None?,
        })
    }

    fn ask_use(&mut self) -> Option<Spanned<UseDecl>> {
        let Spanned(_, kSp) =
            self.get_real(|token| matches!(token, Token::Ident(Ident::Use)))?;
        let Spanned(name, nSp) = self.ask_ident()?;

        Some(Spanned::new(
            UseDecl { module: name },
            [kSp, nSp, self.semi()?],
        ))
    }

    pub fn parse(mut self) -> IDLModule {
        IDLModule {
            uses: fill_while(|| self.ask_use()),
            items: fill_while(|| self.ask_item()),
        }
    }
}

fn fill_while<T>(mut f: impl FnMut() -> Option<Spanned<T>>) -> Vec<T> {
    let mut real = vec![];
    while let Some(Spanned(t, _)) = f() {
        real.push(t);
    }
    real
}