use anyhow::{Result, Context, anyhow};
use mipl::prelude::*;

pub fn tokenize(src: String) -> Parser {
    let del_param = DelimitersParam{
        discard: DiscardDelimiters::new(
            vec![
                ' ',
                '\n',
                '\t'
            ]
        ),
        keep: KeepDelimiters::new(
            vec![
                '(',
                ')',
                '~',
                '&',
                '|',
                '=',
                '>',
                '<',
                '*',
                '#'
            ]
        )
    };

    Parser::from(src, del_param)
}

#[derive(Debug)]
pub struct Parsers {
    /// L-expr parser
    pub l_parser: Parser,
    /// State-expr parser
    pub s_parser: Parser,
    /// The number of steps to take
    pub steps: usize
}
impl Parsers {
    pub fn new(parser: &mut Parser) -> Result<Self> {
        let states: Vec<String> = vec!["*", "#"]
            .into_iter()
            .map(String::from)
            .collect();

        let mut l_parser = CollectUntil::<OrExactMatch>::subparse(states.clone(), parser);

        if l_parser.peek().is_none() {
            return Err(anyhow!(
                "No L-expr found. Refer to https://ecaxpr-book.pages.dev/langref if confused."
            ))
        }

        if parser.peek().is_none() {
            return Err(anyhow!(
                "No State-expr found. Refer to https://ecaxpr-book.pages.dev/langref if confused"
            ))
        };
        let s_parser = CollectWhile::<OrExactMatch>::subparse(states, parser);
        
        let steps: usize = match parser.next() {
            Some(Token::Str(s)) => s.parse().with_context(||
                format!(
                    "Failed to parse Steps-expr. Refer to https://ecaxpr-book.pages.dev/langref if confused"
                )
            ),
            _ => Err(anyhow!(
                "Number of steps to take not given."
            ))
        }?;

        Ok(Parsers {
            l_parser,
            s_parser,
            steps
        })
    }
}