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use std::borrow::Cow;

use nom::{
    error::{make_error, ErrorKind},
    Err, IResult,
};

use crate::parse::combinators::{blank_lines_count, lines_while};

#[derive(Debug, Default, Clone)]
#[cfg_attr(feature = "ser", derive(serde::Serialize))]
pub struct Comment<'a> {
    /// Comments value, with pound signs
    pub value: Cow<'a, str>,
    /// Numbers of blank lines between last comment's line and next non-blank
    /// line or buffer's end
    pub post_blank: usize,
}

impl Comment<'_> {
    pub(crate) fn parse(input: &str) -> Option<(&str, Comment)> {
        parse_internal(input).ok()
    }

    pub fn into_owned(self) -> Comment<'static> {
        Comment {
            value: self.value.into_owned().into(),
            post_blank: self.post_blank,
        }
    }
}

fn parse_internal(input: &str) -> IResult<&str, Comment, ()> {
    let (input, value) = lines_while(|line| {
        let line = line.trim_start();
        line == "#" || line.starts_with("# ")
    })(input)?;

    if value.is_empty() {
        // TODO: better error kind
        return Err(Err::Error(make_error(input, ErrorKind::Many0)));
    }

    let (input, post_blank) = blank_lines_count(input)?;

    Ok((
        input,
        Comment {
            value: value.into(),
            post_blank,
        },
    ))
}