use crate::*;

pub enum EdnItem<T> {
    Nil,
    Num(usize),
    Sym(T),
    Key(T),
    Exp(Vec<EdnItem<T>>),
}
impl<T> Default for EdnItem<T> {
    fn default () -> Self {
        Self::Nil
    }
}
impl<T: Debug> Debug for EdnItem<T> {
    fn fmt (&self, f: &mut Formatter<'_>) -> Result<(), FormatError> {
        use EdnItem::*;
        match self {
            Nil    => write!(f, "Nil"),
            Num(u) => write!(f, "Num({u})"),
            Sym(u) => write!(f, "Sym({u:?})"),
            Key(u) => write!(f, "Key({u:?})"),
            Exp(e) => write!(f, "Exp({})",
                itertools::join(e.iter().map(|i|format!("{:?}", i)), ","))
        }
    }
}
impl<T: PartialEq> PartialEq for EdnItem<T> {
    fn eq (&self, other: &Self) -> bool {
        use EdnItem::*;
        match (self, other) {
            (Nil, Nil) => true,
            (Num(a), Num(b)) => a == b,
            (Sym(a), Sym(b)) => a == b,
            (Key(a), Key(b)) => a == b,
            (Exp(a), Exp(b)) => a == b,
            _ => false
        }
    }
}
impl<T: AsRef<str> + PartialEq + Default + Clone + std::fmt::Debug> EdnItem<T> {
    pub fn to_ref (&self) -> EdnItem<&str> {
        match self {
            Self::Key(x) => EdnItem::Key(x.as_ref()),
            _ => todo!()
        }
    }
    pub fn to_str (&self) -> &str {
        match self {
            Self::Key(x) => x.as_ref(),
            _ => todo!()
        }
    }
    pub fn symbols <'a> (&'a self) -> EdnIterator<'a, T> {
        EdnIterator::new(&self)
    }
}
impl EdnItem<String> {
    pub fn from (other: EdnItem<impl AsRef<str>>) -> EdnItem<String> {
        use EdnItem::*;
        match other {
            Nil => Nil,
            Key(t) => Key(t.as_ref().to_string()),
            _ => todo!()
        }
    }
}
impl<'a> TryFrom<Token<'a>> for EdnItem<String> {
    type Error = ParseError;
    fn try_from (token: Token<'a>) -> Result<Self, Self::Error> {
        use Token::*;
        Ok(match token {
            Nil => Self::Nil,
            Num(chars, index, length) =>
                Self::Num(Token::number(&chars[index..index+length])),
            Sym(chars, index, length) =>
                Self::Sym(String::from(&chars[index..index+length])),
            Key(chars, index, length) =>
                Self::Key(String::from(&chars[index..index+length])),
            Exp(chars, index, length, 0) =>
                Self::Exp(Self::read_all(&chars[index+1..(index+length).saturating_sub(1)])?),
            _ => panic!("unclosed delimiter")
        })
    }
}

impl<'a> TryFrom<Token<'a>> for EdnItem<&'a str> {
    type Error = ParseError;
    fn try_from (token: Token<'a>) -> Result<Self, Self::Error> {
        use Token::*;
        Ok(match token {
            Nil => EdnItem::Nil,
            Num(chars, index, length) =>
                Self::Num(Token::number(&chars[index..index+length])),
            Sym(chars, index, length) =>
                Self::Sym(&chars[index..index+length]),
            Key(chars, index, length) =>
                Self::Key(&chars[index..index+length]),
            Exp(chars, index, length, 0) =>
                Self::Exp(Self::read_all(&chars[index+1..(index+length).saturating_sub(1)])?),
            _ => panic!("unclosed delimiter")
        })
    }
}

impl<'a, T: std::fmt::Debug + Clone + Default + PartialEq + From<&'a str>> EdnItem<T> {
    pub fn read_all (mut source: &'a str) -> Result<Vec<Self>, ParseError> {
        let mut items = vec![];
        loop {
            if source.len() == 0 {
                break
            }
            let (remaining, token) = Token::chomp(source)?;
            match Self::read(token)? { Self::Nil => {}, item => items.push(item) };
            source = remaining
        }
        Ok(items)
    }
    pub fn read_one (source: &'a str) -> Result<(Self, &'a str), ParseError> {
        Ok({
            if source.len() == 0 {
                return Err(ParseError::Unknown(5))
            }
            let (remaining, token) = Token::chomp(source)?;
            (Self::read(token)?, remaining)
        })
    }
    pub fn read (token: Token<'a>) -> Result<Self, ParseError> {
        use Token::*;
        Ok(match token {
            Nil => EdnItem::Nil,
            Num(chars, index, length) =>
                Self::Num(Token::number(&chars[index..index+length])),
            Sym(chars, index, length) =>
                Self::Sym(T::from(&chars[index..index+length])),
            Key(chars, index, length) =>
                Self::Key(T::from(&chars[index..index+length])),
            Exp(chars, index, length, 0) =>
                Self::Exp(Self::read_all(&chars[index+1..(index+length).saturating_sub(1)])?),
            _ => panic!("unclosed delimiter")
        })
    }
    //pub fn to_str <'a> (&'a self) -> EdnItem<&'a str> {
        //use EdnItem::*;
        //match self {
            //Nil    => Nil,
            //Num(n) => Num(*n),
            //Sym(t) => Sym(t.as_str()),
            //Key(t) => Key(t.as_str()),
            //Exp(t) => Exp(t.iter().map(|x|x.to_str()).collect())
        //}
    //}
}