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::eof;
use nom::combinator::not;
use nom::combinator::opt;
use nom::combinator::verify;
use nom::multi::many_till;
use nom::sequence::tuple;

use super::Context;
use crate::error::CustomError;
use crate::error::MyError;
use crate::error::Res;
use crate::parser::element_parser::element;
use crate::parser::exiting::ExitClass;
use crate::parser::greater_element::GreaterBlock;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::source::SetSource;
use crate::parser::util::blank_line;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::immediate_in_section;
use crate::parser::util::start_of_line;
use crate::parser::Element;
use crate::parser::Paragraph;

#[tracing::instrument(ret, level = "debug")]
pub fn greater_block<'r, 's>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, GreaterBlock<'s>> {
    // TODO: Do I need to differentiate between different greater block types.
    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" => false,
            _ => true,
        }),
    ))(remaining)?;
    let context_name = match name.to_lowercase().as_str() {
        "center" => "center block",
        "quote" => "quote block",
        _ => "greater block",
    };
    if immediate_in_section(context, context_name) {
        return Err(nom::Err::Error(CustomError::MyError(MyError(
            "Cannot nest objects of the same element",
        ))));
    }
    let (remaining, parameters) = opt(tuple((space1, parameters)))(remaining)?;
    let (remaining, _nl) = line_ending(remaining)?;
    let parser_context = context
        .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
        .with_additional_node(ContextElement::Context(context_name))
        .with_additional_node(ContextElement::GreaterBlock(name))
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &greater_block_end,
        }));
    let parameters = match parameters {
        Some((_ws, parameters)) => Some(parameters),
        None => None,
    };

    let element_matcher = parser_with_context!(element(true))(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    // Check for a completely empty block
    let (remaining, children) = match tuple((
        not(exit_matcher),
        blank_line,
        many_till(blank_line, exit_matcher),
    ))(remaining)
    {
        Ok((remain, (_not_immediate_exit, first_line, (_trailing_whitespace, _exit_contents)))) => {
            let mut element = Element::Paragraph(Paragraph::of_text(first_line));
            let source = get_consumed(remaining, remain);
            element.set_source(source);
            (remain, vec![element])
        }
        Err(_) => {
            let (remaining, (children, _exit_contents)) =
                many_till(element_matcher, exit_matcher)(remaining)?;
            (remaining, children)
        }
    };
    let (remaining, _end) = greater_block_end(&parser_context, remaining)?;

    // Not checking if parent exit matcher is causing exit because the greater_block_end matcher asserts we matched a full greater block

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        GreaterBlock {
            source,
            name,
            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 parameters<'s>(input: &'s str) -> Res<&'s str, &'s str> {
    is_not("\r\n")(input)
}

#[tracing::instrument(ret, level = "debug")]
fn greater_block_end<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    start_of_line(context, input)?;
    let current_name: &str = get_context_greater_block_name(context).ok_or(nom::Err::Error(
        CustomError::MyError(MyError("Not inside a greater block")),
    ))?;
    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))
}

fn get_context_greater_block_name<'r, 's>(context: Context<'r, 's>) -> Option<&'s str> {
    for thing in context.iter() {
        match thing.get_data() {
            ContextElement::GreaterBlock(name) => return Some(name),
            _ => {}
        };
    }
    None
}