use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::bytes::complete::tag_no_case;
use nom::bytes::complete::take_while1;
use nom::character::complete::line_ending;
use nom::character::complete::space0;
use nom::combinator::eof;
use nom::combinator::map;
use nom::sequence::tuple;

use super::util::get_consumed;
use super::Context;
use crate::error::Res;
use crate::parser::exiting::ExitClass;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::plain_text::plain_text;
use crate::parser::util::start_of_line;
use crate::parser::LatexEnvironment;

#[tracing::instrument(ret, level = "debug")]
pub fn latex_environment<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, LatexEnvironment<'s>> {
    start_of_line(context, input)?;
    let (remaining, _leading_whitespace) = space0(input)?;
    let (remaining, (_opening, name, _open_close_brace, _ws, _line_ending)) = tuple((
        tag_no_case(r#"\begin{"#),
        name,
        tag("}"),
        space0,
        line_ending,
    ))(remaining)?;

    let latex_environment_end_specialized = latex_environment_end(name);
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &latex_environment_end_specialized,
        }));

    let (remaining, _contents) = map(parser_with_context!(plain_text)(&parser_context), |obj| {
        obj.source
    })(remaining)?;
    let (remaining, _end) = latex_environment_end_specialized(&parser_context, remaining)?;

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

#[tracing::instrument(ret, level = "debug")]
fn name<'s>(input: &'s str) -> Res<&'s str, &'s str> {
    take_while1(|c: char| c.is_alphanumeric() || c == '*')(input)
}

fn latex_environment_end(
    current_name: &str,
) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, &'s str> {
    let current_name_lower = current_name.to_lowercase();
    move |context: Context, input: &str| {
        _latex_environment_end(context, input, current_name_lower.as_str())
    }
}

#[tracing::instrument(ret, level = "debug")]
fn _latex_environment_end<'r, 's, 'x>(
    context: Context<'r, 's>,
    input: &'s str,
    current_name_lower: &'x str,
) -> Res<&'s str, &'s str> {
    start_of_line(context, input)?;
    let (remaining, _leading_whitespace) = space0(input)?;
    let (remaining, (_begin, _name, _close_brace, _ws, _line_ending)) = tuple((
        tag_no_case(r#"\end{"#),
        tag_no_case(current_name_lower),
        tag("}"),
        space0,
        alt((eof, line_ending)),
    ))(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, source))
}