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::util::get_consumed;
use super::Context;
use crate::parser::error::CustomError;
use crate::parser::error::MyError;
use crate::parser::error::Res;
use crate::parser::parser_context::ContextElement;
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::immediate_in_section;
use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
use crate::parser::util::start_of_line;
use crate::parser::Comment;

#[tracing::instrument(ret, level = "debug")]
pub fn comment<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Comment<'s>> {
    if immediate_in_section(context, "comment") {
        return Err(nom::Err::Error(CustomError::MyError(MyError(
            "Cannot nest objects of the same element",
        ))));
    }
    let parser_context = context.with_additional_node(ContextElement::Context("comment"));
    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 (remaining, _trailing_ws) =
        maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;

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

#[tracing::instrument(ret, level = "debug")]
fn comment_line<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    start_of_line(context, 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 crate::parser::parser_context::ContextElement;
    use crate::parser::parser_context::ContextTree;
    use crate::parser::parser_with_context::parser_with_context;

    use super::*;

    #[test]
    fn require_space_after_hash() {
        let input = "# Comment line
#not a comment
# Comment again";
        let initial_context: ContextTree<'_, '_> = ContextTree::new();
        let document_context =
            initial_context.with_additional_node(ContextElement::DocumentRoot(input));
        let comment_matcher =
            parser_with_context!(comment)(&document_context);
        let (remaining, first_comment) =
            comment_matcher(input).expect("Parse first comment");
        assert_eq!(remaining, r#"#not a comment
# Comment again"#);
        assert_eq!(
            first_comment.source,
            "# Comment line
"
        );
    }
}