use nom::branch::alt;
use nom::bytes::complete::is_not;
use nom::bytes::complete::tag;
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::multi::many0;
use nom::sequence::preceded;
use nom::sequence::tuple;

use super::org_source::OrgSource;
use super::util::get_consumed;
use crate::context::parser_with_context;
use crate::context::ContextElement;
use crate::context::RefContext;
use crate::error::CustomError;
use crate::error::MyError;
use crate::error::Res;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::immediate_in_section;
use crate::parser::util::start_of_line;
use crate::types::Comment;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub fn comment<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, Comment<'s>> {
    if immediate_in_section(context, "comment") {
        return Err(nom::Err::Error(CustomError::MyError(MyError(
            "Cannot nest objects of the same element".into(),
        ))));
    }
    let parser_context = ContextElement::Context("comment");
    let parser_context = context.with_additional_node(&parser_context);
    let comment_line_matcher = parser_with_context!(comment_line)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    let (remaining, _first_line) = comment_line_matcher(input)?;
    let (remaining, _remaining_lines) =
        many0(preceded(not(exit_matcher), comment_line_matcher))(remaining)?;

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        Comment {
            source: source.into(),
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn comment_line<'b, 'g, 'r, 's>(
    _context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    start_of_line(input)?;
    let (remaining, _indent) = space0(input)?;
    let (remaining, (_hash, _leading_whitespace_and_content, _line_ending)) = tuple((
        tag("#"),
        opt(tuple((space1, is_not("\r\n")))),
        alt((line_ending, eof)),
    ))(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, source))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::context::Context;
    use crate::context::ContextElement;
    use crate::context::GlobalSettings;
    use crate::context::List;

    #[test]
    fn require_space_after_hash() {
        let input = OrgSource::new(
            "# Comment line
#not a comment
# Comment again",
        );
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let comment_matcher = parser_with_context!(comment)(&initial_context);
        let (remaining, first_comment) = comment_matcher(input).expect("Parse first comment");
        assert_eq!(
            Into::<&str>::into(remaining),
            r#"#not a comment
# Comment again"#
        );
        assert_eq!(
            first_comment.source,
            "# Comment line
"
        );
    }
}