use nom::{
    IResult,
    bytes::complete::{tag, take_while1},
    combinator::{recognize, opt},
    multi::many0,
    sequence::{delimited, pair},
};
use crate::whitespace::cfws;


/// VCHAR definition
pub fn is_vchar(c: char) -> bool {
  (c >= '\x21' && c <= '\x7E') || !c.is_ascii()
}

/// Sequence of visible chars with the UTF-8 extension
///
/// ```abnf
/// VCHAR   =  %x21-7E
///            ; visible (printing) characters
/// VCHAR   =/  UTF8-non-ascii
/// SEQ     = 1*VCHAR
///```
pub fn vchar_seq(input: &str) -> IResult<&str, &str> {
   take_while1(is_vchar)(input)
}

/// Atom allowed characters
fn is_atext(c: char) -> bool {
    c.is_ascii_alphanumeric() || "!#$%&'*+-/=?^_`{|}~".contains(c) || !c.is_ascii()
}

/// Atom 
///
/// `[CFWS] 1*atext [CFWS]`
pub fn atom(input: &str) -> IResult<&str, &str> {
    delimited(opt(cfws), take_while1(is_atext), opt(cfws))(input)
}

/// dot-atom-text
///
/// `1*atext *("." 1*atext)`
fn dot_atom_text(input: &str) -> IResult<&str, &str> {
    recognize(pair(take_while1(is_atext), many0(pair(tag("."), take_while1(is_atext)))))(input)
}

/// dot-atom
///
/// `[CFWS] dot-atom-text [CFWS]`
pub fn dot_atom(input: &str) -> IResult<&str, &str> {
    delimited(opt(cfws), dot_atom_text, opt(cfws))(input)
}


#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vchar_seq() {
        assert_eq!(vchar_seq("hello world"), Ok((" world", "hello")));
        assert_eq!(vchar_seq("hello👋 world"), Ok((" world", "hello👋")));
    }

    #[test]
    fn test_atext() {
        assert!(is_atext('='));
        assert!(is_atext('5'));
        assert!(is_atext('Q'));
        assert!(!is_atext(' '));
        assert!(is_atext('É')); // support utf8
    }

    #[test]
    fn test_atom() {
        assert_eq!(atom("(skip)  imf_codec (hidden) aerogramme"), Ok(("aerogramme", "imf_codec")));
    }

    #[test]
    fn test_dot_atom_text() {
        assert_eq!(dot_atom_text("quentin.dufour.io abcdef"), Ok((" abcdef", "quentin.dufour.io")));
    }

    #[test]
    fn test_dot_atom() {
        assert_eq!(dot_atom("   (skip) quentin.dufour.io abcdef"), Ok(("abcdef", "quentin.dufour.io")));
    }
}