use nom::branch::alt;
use nom::bytes::complete::is_not;
use nom::bytes::complete::tag_no_case;
use nom::character::complete::line_ending;
use nom::character::complete::space0;
use nom::character::complete::space1;
use nom::combinator::consumed;
use nom::combinator::eof;
use nom::combinator::opt;
use nom::combinator::verify;
use nom::multi::many_till;
use nom::sequence::tuple;

use super::error::Res;
use super::Context;
use crate::parser::exiting::ExitClass;
use crate::parser::lesser_element::LesserBlock;
use crate::parser::object_parser::standard_set_object;
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::maybe_consume_trailing_whitespace_if_not_exiting;
use crate::parser::util::start_of_line;

#[tracing::instrument(ret, level = "debug")]
pub fn lesser_block<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, LesserBlock<'s>> {
    start_of_line(context, input)?;
    let (remaining, _leading_whitespace) = space0(input)?;
    let (remaining, (_begin, name)) = tuple((
        tag_no_case("#+begin_"),
        verify(name, |name: &str| match name.to_lowercase().as_str() {
            "comment" | "example" | "export" | "src" | "verse" => true,
            _ => false,
        }),
    ))(remaining)?;

    let (remaining, parameters) = opt(tuple((space1, data)))(remaining)?;
    let (remaining, _nl) = line_ending(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("comment");
    let parser_context = context
        .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
        .with_additional_node(ContextElement::Context("lesser block"))
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &lesser_block_end_specialized,
        }));
    let parameters = match parameters {
        Some((_ws, parameters)) => Some(parameters),
        None => None,
    };

    let object_matcher = parser_with_context!(standard_set_object)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    // Check for a completely empty block
    let (remaining, children) = match consumed(many_till(blank_line, exit_matcher))(remaining) {
        Ok((remaining, (whitespace, (_children, _exit_contents)))) => todo!(),
        Err(_) => {
            let (remaining, (children, _exit_contents)) =
                many_till(object_matcher, exit_matcher)(remaining)?;
            (remaining, children)
        }
    };
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let (remaining, _trailing_ws) =
        maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        LesserBlock {
            source,
            name,
            data: parameters,
            children,
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn name<'s>(input: &'s str) -> Res<&'s str, &'s str> {
    is_not(" \t\r\n")(input)
}

#[tracing::instrument(ret, level = "debug")]
fn data<'s>(input: &'s str) -> Res<&'s str, &'s str> {
    is_not("\r\n")(input)
}

fn lesser_block_end<'x>(current_name: &'x str) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, &'s str> + 'x {
    move |context: Context, input: &str| {
        start_of_line(context, input)?;
        let (remaining, _leading_whitespace) = space0(input)?;
        let (remaining, (_begin, _name, _ws)) = tuple((
            tag_no_case("#+end_"),
            tag_no_case(current_name),
            alt((eof, line_ending)),
        ))(remaining)?;
        let source = get_consumed(input, remaining);
        Ok((remaining, source))
    }
}