use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::anychar;
use nom::character::complete::line_ending;
use nom::character::complete::multispace1;
use nom::character::complete::one_of;
use nom::character::complete::space0;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many_till;
use nom::sequence::terminated;
use tracing::span;

use super::radio_link::RematchObject;
use super::Context;
use crate::error::CustomError;
use crate::error::MyError;
use crate::error::Res;
use crate::parser::exiting::ExitClass;
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::radio_link::rematch_target;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::get_one_before;
use crate::parser::util::preceded_by_whitespace;
use crate::parser::Bold;
use crate::parser::Code;
use crate::parser::Italic;
use crate::parser::Object;
use crate::parser::StrikeThrough;
use crate::parser::Underline;
use crate::parser::Verbatim;

#[tracing::instrument(ret, level = "debug")]
pub fn text_markup<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Object<'s>> {
    alt((
        map(parser_with_context!(bold)(context), Object::Bold),
        map(parser_with_context!(italic)(context), Object::Italic),
        map(parser_with_context!(underline)(context), Object::Underline),
        map(
            parser_with_context!(strike_through)(context),
            Object::StrikeThrough,
        ),
        map(parser_with_context!(verbatim)(context), Object::Verbatim),
        map(parser_with_context!(code)(context), Object::Code),
    ))(input)
}

#[tracing::instrument(ret, level = "debug")]
pub fn bold<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Bold<'s>> {
    let text_markup_object_specialized = text_markup_object("*");
    let (remaining, children) = text_markup_object_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, Bold { source, children }))
}

#[tracing::instrument(ret, level = "debug")]
pub fn italic<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Italic<'s>> {
    let text_markup_object_specialized = text_markup_object("/");
    let (remaining, children) = text_markup_object_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, Italic { source, children }))
}

#[tracing::instrument(ret, level = "debug")]
pub fn underline<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Underline<'s>> {
    let text_markup_object_specialized = text_markup_object("_");
    let (remaining, children) = text_markup_object_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, Underline { source, children }))
}

#[tracing::instrument(ret, level = "debug")]
pub fn strike_through<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, StrikeThrough<'s>> {
    let text_markup_object_specialized = text_markup_object("+");
    let (remaining, children) = text_markup_object_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, StrikeThrough { source, children }))
}

#[tracing::instrument(ret, level = "debug")]
pub fn verbatim<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Verbatim<'s>> {
    let text_markup_string_specialized = text_markup_string("=");
    let (remaining, contents) = text_markup_string_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, Verbatim { source, contents }))
}

#[tracing::instrument(ret, level = "debug")]
pub fn code<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Code<'s>> {
    let text_markup_string_specialized = text_markup_string("~");
    let (remaining, contents) = text_markup_string_specialized(context, input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, Code { source, contents }))
}

fn text_markup_object(
    marker_symbol: &str,
) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, Vec<Object<'s>>> {
    let marker_symbol = marker_symbol.to_owned();
    move |context: Context, input: &str| _text_markup_object(context, input, marker_symbol.as_str())
}

#[tracing::instrument(ret, level = "debug")]
fn _text_markup_object<'r, 's, 'x>(
    context: Context<'r, 's>,
    input: &'s str,
    marker_symbol: &'x str,
) -> Res<&'s str, Vec<Object<'s>>> {
    let (remaining, _) = pre(context, input)?;
    let (remaining, open) = tag(marker_symbol)(remaining)?;
    let (remaining, _peek_not_whitespace) = peek(not(multispace1))(remaining)?;
    let text_markup_end_specialized = text_markup_end(open);
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &text_markup_end_specialized,
        }));

    let (remaining, (children, _exit_contents)) = verify(
        many_till(
            parser_with_context!(standard_set_object)(&parser_context),
            parser_with_context!(exit_matcher_parser)(&parser_context),
        ),
        |(children, _exit_contents)| !children.is_empty(),
    )(remaining)?;

    {
        let span = span!(tracing::Level::DEBUG, "Checking parent exit.");
        let _enter = span.enter();
        if exit_matcher_parser(context, remaining).is_ok() {
            return Err(nom::Err::Error(CustomError::MyError(MyError(
                "Parent exit matcher is triggering.",
            ))));
        }
    }

    let (remaining, _close) = text_markup_end_specialized(context, remaining)?;
    let (remaining, _trailing_whitespace) = space0(remaining)?;
    Ok((remaining, children))
}

fn text_markup_string(
    marker_symbol: &str,
) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, &'s str> {
    let marker_symbol = marker_symbol.to_owned();
    move |context: Context, input: &str| _text_markup_string(context, input, marker_symbol.as_str())
}

#[tracing::instrument(ret, level = "debug")]
fn _text_markup_string<'r, 's, 'x>(
    context: Context<'r, 's>,
    input: &'s str,
    marker_symbol: &'x str,
) -> Res<&'s str, &'s str> {
    let (remaining, _) = pre(context, input)?;
    let (remaining, open) = tag(marker_symbol)(remaining)?;
    let (remaining, _peek_not_whitespace) = peek(not(multispace1))(remaining)?;
    let text_markup_end_specialized = text_markup_end(open);
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &text_markup_end_specialized,
        }));

    let (remaining, contents) = recognize(verify(
        many_till(
            anychar,
            parser_with_context!(exit_matcher_parser)(&parser_context),
        ),
        |(children, _exit_contents)| !children.is_empty(),
    ))(remaining)?;

    {
        let span = span!(tracing::Level::DEBUG, "Checking parent exit.");
        let _enter = span.enter();
        if exit_matcher_parser(context, remaining).is_ok() {
            return Err(nom::Err::Error(CustomError::MyError(MyError(
                "Parent exit matcher is triggering.",
            ))));
        }
    }

    let (remaining, _close) = text_markup_end_specialized(context, remaining)?;
    let (remaining, _trailing_whitespace) = space0(remaining)?;
    Ok((remaining, contents))
}

#[tracing::instrument(ret, level = "debug")]
pub fn pre<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
    let document_root = context.get_document_root().unwrap();
    let preceding_character = get_one_before(document_root, input)
        .map(|slice| slice.chars().next())
        .flatten();
    match preceding_character {
        // If None, we are at the start of the file which is technically the beginning of a line.
        None | Some('\r') | Some('\n') | Some(' ') | Some('\t') | Some('-') | Some('(')
        | Some('{') | Some('\'') | Some('"') | Some('<') => {}
        Some(_) => {
            // Not at start of line, cannot be a heading
            return Err(nom::Err::Error(CustomError::MyError(MyError(
                "Not a valid pre character for text markup.",
            ))));
        }
    };
    Ok((input, ()))
}

#[tracing::instrument(ret, level = "debug")]
pub fn post<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
    let (remaining, _) = alt((recognize(one_of(" \r\n\t-.,;:!?')}[\">")), line_ending))(input)?;
    Ok((remaining, ()))
}

fn text_markup_end(
    marker_symbol: &str,
) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, &'s str> {
    let marker_symbol = marker_symbol.to_owned();
    move |context: Context, input: &str| _text_markup_end(context, input, marker_symbol.as_str())
}

#[tracing::instrument(ret, level = "debug")]
fn _text_markup_end<'r, 's, 'x>(
    context: Context<'r, 's>,
    input: &'s str,
    marker_symbol: &'x str,
) -> Res<&'s str, &'s str> {
    not(parser_with_context!(preceded_by_whitespace)(context))(input)?;
    let (remaining, _marker) = terminated(
        tag(marker_symbol),
        peek(parser_with_context!(post)(context)),
    )(input)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, source))
}

impl<'x> RematchObject<'x> for Bold<'x> {
    #[tracing::instrument(ret, level = "debug")]
    fn rematch_object<'r, 's>(
        &'x self,
        _context: Context<'r, 's>,
        input: &'s str,
    ) -> Res<&'s str, Object<'s>> {
        let (remaining, children) =
            _rematch_text_markup_object(_context, input, "*", &self.children)?;
        let source = get_consumed(input, remaining);
        Ok((remaining, Object::Bold(Bold { source, children })))
    }
}

#[tracing::instrument(ret, level = "debug")]
fn _rematch_text_markup_object<'r, 's, 'x>(
    context: Context<'r, 's>,
    input: &'s str,
    marker_symbol: &'static str,
    original_match_children: &'x Vec<Object<'x>>,
) -> Res<&'s str, Vec<Object<'s>>> {
    let (remaining, _) = pre(context, input)?;
    let (remaining, open) = tag(marker_symbol)(remaining)?;
    let (remaining, _peek_not_whitespace) = peek(not(multispace1))(remaining)?;
    let text_markup_end_specialized = text_markup_end(open);
    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &text_markup_end_specialized,
        }));

    let (remaining, children) =
        // TODO: This doesn't really check the exit matcher between each object. I think it may be possible to construct an org document that parses incorrectly with the current code.
        rematch_target(&parser_context, original_match_children, remaining)?;

    {
        let span = span!(tracing::Level::DEBUG, "Checking parent exit.");
        let _enter = span.enter();
        if exit_matcher_parser(context, remaining).is_ok() {
            return Err(nom::Err::Error(CustomError::MyError(MyError(
                "Parent exit matcher is triggering.",
            ))));
        }
    }

    let (remaining, _close) = text_markup_end_specialized(context, remaining)?;
    let (remaining, _trailing_whitespace) = space0(remaining)?;
    Ok((remaining, children))
}