#![allow(clippy::upper_case_acronyms)]

pub mod combinator;
mod peg_parser;
mod test;

use std::{cell::RefCell, fmt, rc::Rc};

use combinator::Span;

#[cfg(test)]
use crate::ast::{Block, Expression};
use crate::{
    ast::{ASTItem, AST},
    identifier::{Id, IdStore},
};

pub struct Parser {
    id_store: IdStore<ASTItem>,
}

impl Parser {
    pub(crate) fn new() -> Self {
        Self { id_store: IdStore::new() }
    }

    pub(crate) fn parse(&mut self, input: &str) -> Result<AST, ParseError> {
        peg_parser::schala_parser::program(input, self).map_err(ParseError::from_peg)
    }

    pub(crate) fn parse_comb(&mut self, input: &str) -> Result<AST, ParseError> {
        let id_store: IdStore<ASTItem> = IdStore::new();
        let span = Span::new_extra(input, Rc::new(RefCell::new(id_store)));
        combinator::program(span).map_err(|err| convert_err(input, err)).map(|(_, output)| output)
    }

    #[cfg(test)]
    fn expression(&mut self, input: &str) -> Result<Expression, ParseError> {
        peg_parser::schala_parser::expression(input, self).map_err(ParseError::from_peg)
    }

    #[cfg(test)]
    fn expression_comb(&mut self, input: &str) -> Result<Expression, ParseError> {
        let id_store: IdStore<ASTItem> = IdStore::new();
        let span = Span::new_extra(input, Rc::new(RefCell::new(id_store)));

        combinator::expression(span).map_err(|err| convert_err(input, err)).map(|(rest, output)| output)
    }

    #[cfg(test)]
    fn block(&mut self, input: &str) -> Result<Block, ParseError> {
        peg_parser::schala_parser::block(input, self).map_err(ParseError::from_peg)
    }

    #[cfg(test)]
    fn block_comb(&mut self, input: &str) -> Result<Block, ParseError> {
        let id_store: IdStore<ASTItem> = IdStore::new();
        let span = Span::new_extra(input, Rc::new(RefCell::new(id_store)));
        combinator::block(span).map_err(|err| convert_err(input, err)).map(|(_, output)| output)
    }

    fn fresh(&mut self) -> Id<ASTItem> {
        self.id_store.fresh()
    }
}

fn convert_err<'a>(
    input: &'a str,
    err: nom::Err<nom::error::VerboseError<combinator::Span<'a>>>,
) -> ParseError {
    use nom::{error::VerboseError, Err};

    match err {
        Err::Error(err) | Err::Failure(err) => {
            let err = VerboseError {
                errors: err.errors.into_iter().map(|(sp, kind)| (*sp.fragment(), kind)).collect(),
            };
            let msg = nom::error::convert_error(input, err);
            ParseError { msg, location: (0).into() }
        }
        _ => panic!(),
    }
}

/// Represents a parsing error
#[derive(Debug)]
pub struct ParseError {
    pub msg: String,
    pub location: Location,
}

impl ParseError {
    fn from_peg(err: peg::error::ParseError<peg::str::LineCol>) -> Self {
        let msg = err.to_string();
        Self { msg, location: err.location.offset.into() }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub struct Location {
    pub(crate) offset: usize,
}

impl From<usize> for Location {
    fn from(offset: usize) -> Self {
        Self { offset }
    }
}

impl fmt::Display for Location {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.offset)
    }
}