use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::line_ending;
use nom::character::complete::space1;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::opt;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many0;
use nom::multi::many1;
use nom::multi::many1_count;
use nom::multi::many_till;
use nom::sequence::tuple;

use crate::parser::element::element;
use crate::parser::object::standard_set_object;
use crate::parser::parser_context::ChainBehavior;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ContextTree;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::util::element_trailing_whitespace;

use super::element::Element;
use super::error::Res;
use super::object::Object;
use super::parser_with_context::parser_with_context;
use super::source::Source;
use super::util::exit_matcher_parser;
use super::util::get_consumed;
use super::util::start_of_line;
use super::util::trailing_whitespace;
use super::Context;

#[derive(Debug)]
pub struct Document<'s> {
    pub source: &'s str,
    pub zeroth_section: Option<Section<'s>>,
    pub children: Vec<Heading<'s>>,
}

#[derive(Debug)]
pub struct Heading<'s> {
    pub source: &'s str,
    pub stars: usize,
    pub title: Vec<Object<'s>>,
    pub children: Vec<DocumentElement<'s>>,
}

#[derive(Debug)]
pub struct Section<'s> {
    pub source: &'s str,
    pub children: Vec<Element<'s>>,
}

#[derive(Debug)]
pub enum DocumentElement<'s> {
    Heading(Heading<'s>),
    Section(Section<'s>),
}

impl<'s> Source<'s> for Document<'s> {
    fn get_source(&'s self) -> &'s str {
        self.source
    }
}

impl<'s> Source<'s> for DocumentElement<'s> {
    fn get_source(&'s self) -> &'s str {
        match self {
            DocumentElement::Heading(obj) => obj.source,
            DocumentElement::Section(obj) => obj.source,
        }
    }
}

#[tracing::instrument(ret, level = "debug")]
#[allow(dead_code)]
pub fn document(input: &str) -> Res<&str, Document> {
    let initial_context: ContextTree<'_, '_> = ContextTree::new();
    let document_context =
        initial_context.with_additional_node(ContextElement::DocumentRoot(input));
    let section_matcher = parser_with_context!(section)(&document_context);
    let heading_matcher = parser_with_context!(heading)(&document_context);
    let (remaining, zeroth_section) = opt(section_matcher)(input)?;
    let (remaining, children) = many0(heading_matcher)(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        Document {
            source,
            zeroth_section,
            children,
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn section<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Section<'s>> {
    // TODO: The zeroth section is specialized so it probably needs its own parser
    let parser_context = context
        .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
        .with_additional_node(ContextElement::Context("section"))
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&section_end)),
        }));
    let element_matcher = parser_with_context!(element)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    let trailing_matcher = parser_with_context!(element_trailing_whitespace)(&parser_context);
    let (remaining, (children, _exit_contents)) = verify(
        many_till(
            tuple((
                element_matcher,
                opt(map(trailing_matcher, Element::TrailingWhitespace)),
            )),
            exit_matcher,
        ),
        |(children, _exit_contents)| !children.is_empty(),
    )(input)?;
    let flattened_children: Vec<Element> = children
        .into_iter()
        .flat_map(|tpl| {
            let mut flattened_children = Vec::with_capacity(2);
            flattened_children.push(tpl.0);
            if let Some(bar) = tpl.1 {
                flattened_children.push(bar);
            }
            flattened_children.into_iter()
        })
        .collect();
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        Section {
            source,
            children: flattened_children,
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn section_end<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let headline_matcher = parser_with_context!(headline)(context);
    alt((recognize(headline_matcher), eof))(input)
}

#[tracing::instrument(ret, level = "debug")]
fn heading<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Heading<'s>> {
    not(|i| context.check_exit_matcher(i))(input)?;
    let (remaining, (star_count, _ws, title, _ws2)) = headline(context, input)?;
    let section_matcher = parser_with_context!(section)(context);
    let heading_matcher = parser_with_context!(heading)(context);
    let (remaining, children) = many0(alt((
        map(
            verify(heading_matcher, |h| h.stars > star_count),
            DocumentElement::Heading,
        ),
        map(section_matcher, DocumentElement::Section),
    )))(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        Heading {
            source,
            stars: star_count,
            title,
            children,
        },
    ))
}

#[tracing::instrument(ret, level = "debug")]
fn headline<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, (usize, &'s str, Vec<Object<'s>>, &'s str)> {
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&headline_end)),
        }));
    let standard_set_object_matcher = parser_with_context!(standard_set_object)(&parser_context);
    let start_of_line_matcher = parser_with_context!(start_of_line)(&parser_context);

    let (remaining, (_sol, star_count, ws, title, ws2)) = tuple((
        start_of_line_matcher,
        many1_count(tag("*")),
        space1,
        many1(standard_set_object_matcher),
        trailing_whitespace,
    ))(input)?;
    Ok((remaining, (star_count, ws, title, ws2)))
}

#[tracing::instrument(ret, level = "debug")]
fn headline_end<'r, 's>(_context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    alt((line_ending, eof))(input)
}