use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::anychar;
use nom::combinator::opt;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many1;
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::ExportSnippet;

#[tracing::instrument(ret, level = "debug")]
pub fn export_snippet<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, ExportSnippet<'s>> {
    let (remaining, _) = tag("@@")(input)?;
    let (remaining, backend_name) = backend(context, remaining)?;
    let (remaining, backend_contents) =
        opt(tuple((tag(":"), parser_with_context!(contents)(context))))(remaining)?;
    let (remaining, _) = tag("@@")(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        ExportSnippet {
            source,
            backend: backend_name,
            contents: backend_contents.map(|(_colon, backend_contents)| backend_contents),
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn backend<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let (remaining, backend_name) =
        recognize(many1(verify(anychar, |c| c.is_alphanumeric() || *c == '-')))(input)?;

    Ok((remaining, backend_name))
}

#[tracing::instrument(ret, level = "debug")]
fn contents<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let (remaining, source) = recognize(verify(
        many_till(
            anychar,
            peek(alt((
                parser_with_context!(exit_matcher_parser)(context),
                tag("@@"),
            ))),
        ),
        |(children, _exit_contents)| !children.is_empty(),
    ))(input)?;
    Ok((remaining, source))
}