use super::combinator::context_many_till;
use super::error::Res;
use super::parser_context::ChainBehavior;
use super::parser_context::ContextElement;
use super::parser_context::ExitMatcherNode;
use super::text::blank_line;
use super::text::line_break;
use super::text::Paragraph;
use super::text::TextElement;
use super::text_element_parser::flat_text_element;
use super::token::Token;
use super::Context;
use nom::branch::alt;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::recognize;
use nom::multi::many1;
use nom::sequence::tuple;

pub fn paragraph<'s, 'r>(context: Context<'r, 's>, i: &'s str) -> Res<&'s str, Paragraph<'s>> {
    // Add a not(eof) check because many_till cannot match a zero-length string
    not(eof)(i)?;
    let paragraph_context = context
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&context_paragraph_end)),
        }))
        .with_additional_node(ContextElement::StartOfParagraph);
    let (remaining, (many, till)) =
        context_many_till(&paragraph_context, flat_text_element, context_paragraph_end)(i)?;
    let many = many
        .into_iter()
        .filter_map(|token| match token {
            Token::TextElement(text_element) => Some(text_element),
            Token::Paragraph(_) => panic!("There should only be text elements in paragraphs."),
        })
        .collect();
    Ok((
        remaining,
        Paragraph {
            contents: many,
            paragraph_end: till,
        },
    ))
}

fn context_paragraph_end<'s, 'r>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, &'s str> {
    paragraph_end(input)
}

fn paragraph_end(input: &str) -> Res<&str, &str> {
    alt((
        recognize(tuple((
            map(line_break, TextElement::LineBreak),
            many1(blank_line),
        ))),
        eof,
    ))(input)
}