use super::error::Res;
use super::util::WORD_CONSTITUENT_CHARACTERS;
use super::Context;
use crate::parser::element::element;
use crate::parser::greater_element::FootnoteDefinition;
use crate::parser::parser_context::ChainBehavior;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::util::blank_line;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::start_of_line;
use crate::parser::util::whitespace_eof;
use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::bytes::complete::tag_no_case;
use nom::bytes::complete::take_while;
use nom::character::complete::digit1;
use nom::character::complete::space0;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many1;
use nom::multi::many_till;
use nom::sequence::tuple;

#[tracing::instrument(ret, level = "debug")]
pub fn footnote_definition<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, FootnoteDefinition<'s>> {
    start_of_line(context, input)?;
    // Cannot be indented.
    let (remaining, (_lead_in, lbl, _lead_out, _ws)) =
        tuple((tag_no_case("[fn:"), label, tag("]"), space0))(input)?;
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::IgnoreParent(Some(&footnote_definition_end)),
        }));
    let element_matcher = parser_with_context!(element)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    let (remaining, (children, _exit_contents)) =
        many_till(element_matcher, exit_matcher)(remaining)?;
    let footnote_definition_end_matcher = parser_with_context!(footnote_definition_end)(context);
    let (remaining, _end) = alt((footnote_definition_end_matcher, whitespace_eof))(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        FootnoteDefinition {
            source,
            label: lbl,
            children,
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn label<'s>(input: &'s str) -> Res<&'s str, &'s str> {
    alt((
        digit1,
        take_while(|c| WORD_CONSTITUENT_CHARACTERS.contains(c) || "-_".contains(c)),
    ))(input)
}

#[tracing::instrument(ret, level = "debug")]
fn footnote_definition_end<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, &'s str> {
    let start_of_line_matcher = parser_with_context!(start_of_line)(&context);
    recognize(tuple((
        start_of_line_matcher,
        verify(many1(blank_line), |lines: &Vec<&str>| lines.len() >= 2),
    )))(input)
}