use super::error::Res;
use super::footnote_definition::footnote_definition;
use super::greater_block::greater_block;
use super::greater_element::FootnoteDefinition;
use super::greater_element::GreaterBlock;
use super::greater_element::PlainList;
use super::lesser_element::Paragraph;
use super::paragraph::paragraph;
use super::plain_list::plain_list;
use super::source::Source;
use super::Context;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_with_context::parser_with_context;
use nom::branch::alt;
use nom::combinator::map;

#[derive(Debug)]
pub enum Element<'s> {
    Paragraph(Paragraph<'s>),
    PlainList(PlainList<'s>),
    GreaterBlock(GreaterBlock<'s>),
    FootnoteDefinition(FootnoteDefinition<'s>),
    /// The whitespace that follows an element.
    ///
    /// This isn't a real org-mode element. Except for items in plain lists, trailing blank lines belong to the preceding element. It is a separate `Element` in this enum to make parsing easier.
    TrailingWhitespace(&'s str),
}

impl<'s> Source<'s> for Element<'s> {
    fn get_source(&'s self) -> &'s str {
        match self {
            Element::Paragraph(obj) => obj.source,
            Element::PlainList(obj) => obj.source,
            Element::GreaterBlock(obj) => obj.source,
            Element::TrailingWhitespace(src) => src,
            Element::FootnoteDefinition(obj) => obj.source,
        }
    }
}

#[tracing::instrument(ret, level = "debug")]
pub fn element_with_whitespace<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, Element<'s>> {
    let parser_context =
        context.with_additional_node(ContextElement::ConsumeTrailingWhitespace(true));
    element(&parser_context, input)
}

#[tracing::instrument(ret, level = "debug")]
pub fn element_without_whitespace<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, Element<'s>> {
    let parser_context =
        context.with_additional_node(ContextElement::ConsumeTrailingWhitespace(false));
    element(&parser_context, input)
}

#[tracing::instrument(ret, level = "debug")]
pub fn element<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Element<'s>> {
    let non_paragraph_matcher = parser_with_context!(non_paragraph_element)(context);
    let paragraph_matcher = parser_with_context!(paragraph)(context);

    alt((
        non_paragraph_matcher,
        map(paragraph_matcher, Element::Paragraph),
    ))(input)
}

pub fn non_paragraph_element<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, Element<'s>> {
    let plain_list_matcher = parser_with_context!(plain_list)(context);
    let greater_block_matcher = parser_with_context!(greater_block)(context);
    let footnote_definition_matcher = parser_with_context!(footnote_definition)(context);
    alt((
        map(plain_list_matcher, Element::PlainList),
        map(greater_block_matcher, Element::GreaterBlock),
        map(footnote_definition_matcher, Element::FootnoteDefinition),
    ))(input)
}