// © 2023 John Breaux
//! A [`Parsable`] struct (an AST node) can parse tokens from a [stream](TokenStream) into it[`self`](https://doc.rust-lang.org/stable/std/keyword.SelfTy.html)
use super::*;
/// Parses tokens from [stream](TokenStream) into Self node
pub trait Parsable {
    /// Parses tokens from [TokenStream](TokenStream) into Self nodes
    fn parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Self, ParseError>
    where
        Self: Sized,
        T: TokenStream<'text>;

    /// Attempts to parse tokens from [stream](TokenStream) into Self nodes.
    ///
    /// Masks failed expectations.
    fn try_parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Option<Self>, ParseError>
    where
        Self: Sized,
        T: TokenStream<'text>,
    {
        match Self::parse(p, stream) {
            Ok(some) => Ok(Some(some)),
            Err(ParseError::LexError(_)) => Ok(None),
            Err(e) => Err(e),
        }
    }

    fn parse_and<'text, T, R>(
        p: &Parser,
        stream: &mut T,
        f: fn(p: &Parser, &mut T) -> R,
    ) -> Result<(Self, R), ParseError>
    where
        Self: Sized,
        T: TokenStream<'text>,
    {
        Ok((Self::parse(p, stream)?, f(p, stream)))
    }

    /// Attempts to parse tokens from [stream](TokenStream) into Self nodes.
    ///
    /// Returns [`Self::default()`](Default::default()) on error
    fn parse_or_default<'text, T>(p: &Parser, stream: &mut T) -> Self
    where
        Self: Sized + Default,
        T: TokenStream<'text>,
    {
        Self::parse(p, stream).unwrap_or_default()
    }
}

macro_rules! parsable_str_types {
    ($($t:ty),*$(,)?) => {$(
        impl Parsable for $t {
            fn parse<'text, T>(_p: &Parser, stream: &mut T) -> Result<Self, ParseError>
            where T: TokenStream<'text> {
                Ok(stream.expect(Type::String)?.lexeme().trim_matches('"').into())
            }
        }
    )*};
}
use std::{path::PathBuf, rc::Rc};
parsable_str_types![String, Rc<str>, Box<str>, PathBuf];

/// Vectors of arbitrary parsables are cool
impl<P: Parsable> Parsable for Vec<P> {
    fn parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Self, ParseError>
    where T: TokenStream<'text> {
        // [dead beef]
        // [A, B,]
        // [c d e f]
        // [ something
        //   else      ]

        stream.require(Type::LBracket)?;
        stream.allow(Type::Endl);
        let mut out = vec![];
        while let Some(t) = P::try_parse(p, stream)? {
            out.push(t);
            stream.allow(Type::Separator);
            stream.allow(Type::Endl);
        }
        stream.require(Type::RBracket)?;
        Ok(out)
    }
}