use crate::combinators::separated_by::SeparatedBy;
use crate::parser::{BoxedParser, ParseResult, Parser, ParserInput, Representation};

pub fn repeated<'a, P, I, O>(parser: P) -> Repeated<'a, I, O>
where
    P: Parser<I, O, I> + 'a,
    I: ParserInput + Clone + 'a,
{
    Repeated {
        inner_parser: BoxedParser::new(parser),
        at_least: None,
        at_most: None,
    }
}

pub struct Repeated<'a, I, O>
where
    I: ParserInput + Clone,
{
    pub(super) inner_parser: BoxedParser<'a, I, O, I>,
    pub(super) at_least: Option<u16>,
    pub(super) at_most: Option<u16>,
}

impl<'a, I, O> Repeated<'a, I, O>
where
    I: ParserInput + Clone,
{
    pub fn at_least(self, n: u16) -> Self {
        Self {
            at_least: Some(n),
            ..self
        }
    }
    pub fn at_most(self, n: u16) -> Self {
        Self {
            at_most: Some(n),
            ..self
        }
    }

    pub fn separated_by<D, O2>(self, delimiter: D, allow_trailing: bool) -> SeparatedBy<'a, I, O>
    where
        D: Parser<I, O2, I> + 'a,
        O2: 'a,
        I: 'a,
    {
        SeparatedBy {
            inner_repeated: self,
            delimiter: BoxedParser::new(delimiter.to(())),
            allow_trailing,
        }
    }
}

impl<'a, I, O> Parser<I, Vec<O>, I> for Repeated<'a, I, O>
where
    I: ParserInput + Clone + 'a,
{
    fn parse(&self, input: I) -> ParseResult<I, Vec<O>, I> {
        let at_least = self.at_least.unwrap_or(0);
        let at_most = self.at_most.unwrap_or(u16::MAX);

        if at_most == 0 {
            return Ok((vec![], input));
        }

        let mut results = Vec::new();
        let mut count: u16 = 0;
        let mut further_input = input.clone();

        while let Ok((item, rest)) = self.inner_parser.parse(further_input.clone()) {
            results.push(item);
            further_input = rest;
            count += 1;
            if count >= at_most {
                break;
            }
        }
        if count < at_least {
            return Err(input);
        }

        Ok((results, further_input))
    }

    fn representation(&self) -> Representation {
        Representation::repeated(
            self.inner_parser.representation(),
            self.at_least.unwrap_or(0),
            self.at_most.unwrap_or(u16::MAX),
        )
    }
}