use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::alpha1;
use nom::character::complete::anychar;
use nom::character::complete::line_ending;
use nom::character::complete::one_of;
use nom::character::complete::space0;
use nom::combinator::opt;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::multi::many_till;
use nom::sequence::tuple;

use super::Context;
use crate::error::Res;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::LatexFragment;

#[tracing::instrument(ret, level = "debug")]
pub fn latex_fragment<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, LatexFragment<'s>> {
    let (remaining, _) = alt((parser_with_context!(raw_latex_fragment)(context),))(input)?;
    let (remaining, _) = space0(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, LatexFragment { source }))
}

#[tracing::instrument(ret, level = "debug")]
fn raw_latex_fragment<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let (remaining, _) = tag("\\")(input)?;
    let (remaining, _) = name(context, remaining)?;
    let (remaining, _) = opt(parser_with_context!(brackets)(context))(remaining)?;

    let source = get_consumed(input, remaining);
    Ok((remaining, source))
}

#[tracing::instrument(ret, level = "debug")]
fn name<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    alpha1(input)
}

#[tracing::instrument(ret, level = "debug")]
fn brackets<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let (remaining, body) = alt((
        recognize(tuple((
            tag("["),
            many_till(
                anychar,
                peek(alt((
                    parser_with_context!(exit_matcher_parser)(context),
                    alt((recognize(one_of("{}[]")), line_ending)),
                ))),
            ),
            tag("]"),
        ))),
        recognize(tuple((
            tag("{"),
            many_till(
                anychar,
                peek(alt((
                    parser_with_context!(exit_matcher_parser)(context),
                    alt((recognize(one_of("{}")), line_ending)),
                ))),
            ),
            tag("}"),
        ))),
    ))(input)?;
    Ok((remaining, body))
}