use nom::bytes::complete::tag;
use nom::character::complete::anychar;
use nom::character::complete::one_of;
use nom::character::complete::space0;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many_till;

use super::org_source::OrgSource;
use super::Context;
use crate::error::CustomError;
use crate::error::MyError;
use crate::error::Res;
use crate::parser::exiting::ExitClass;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_context::ExitMatcherNode;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::get_one_before;
use crate::parser::Target;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub fn target<'r, 's>(
    context: Context<'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, Target<'s>> {
    let (remaining, _) = tag("<<")(input)?;
    let (remaining, _) = peek(verify(anychar, |c| {
        !c.is_whitespace() && !"<>\n".contains(*c)
    }))(remaining)?;

    let parser_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &target_end,
        }));
    let (remaining, _body) = recognize(many_till(
        anychar,
        parser_with_context!(exit_matcher_parser)(&parser_context),
    ))(remaining)?;

    let document_root = context.get_document_root().unwrap();
    let preceding_character = get_one_before(document_root, remaining)
        .map(|slice| slice.chars().next())
        .flatten()
        .expect("We cannot be at the start of the file because we are inside a target.");
    if preceding_character.is_whitespace() {
        return Err(nom::Err::Error(CustomError::MyError(MyError(
            "Targets cannot end with whitespace.".into(),
        ))));
    }
    let (remaining, _) = tag(">>")(remaining)?;
    let (remaining, _) = space0(remaining)?;
    let source = get_consumed(input, remaining);

    Ok((
        remaining,
        Target {
            source: source.into(),
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn target_end<'r, 's>(
    context: Context<'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    recognize(one_of("<>\n"))(input)
}