//! Formatting specifiers for the config file format
use super::*;
use sexp::{
    Sexp,
    Atom,
};

/// A valid type in the config file
#[derive(Debug)]
pub enum LispType
{
    List,
    String,
    Integer,
    Float,

    /// A non-descript atom, either String, Integer, Float, or the empty list.
    Atom,
}

impl From<Sexp> for LispType
{
    fn from(from: Sexp) -> Self
    {
	match from {
	    Sexp::Atom(atom) => atom.into(),
	    Sexp::List(_) => Self::List
	}
    }
}


impl From<&Sexp> for LispType
{
    fn from(from: &Sexp) -> Self
    {
	match from {
	    Sexp::Atom(atom) => atom.into(),
	    Sexp::List(_) => Self::List
	}
    }
}

impl From<&Atom> for LispType
{
    fn from(from: &Atom) -> Self
    {
	match from {
	    Atom::F(_) => Self::Float,
	    Atom::I(_) => Self::Integer,
	    Atom::S(_) => Self::String,
	}
    }
}

impl From<Atom> for LispType
{
    fn from(from: Atom) -> Self
    {
	match from {
	    Atom::F(_) => Self::Float,
	    Atom::I(_) => Self::Integer,
	    Atom::S(_) => Self::String,
	}
    }
}

impl<T> From<Result<T, Error>> for LispType
where T: Into<LispType>
{
    fn from(from: Result<T, Error>) -> Self
    {
	match from {
	    Ok(value) => value.into(),
	    Err(Error::TypeError{got,..}) => got,
	    _ => unreachable!("you shouldn't use this here"),
	}
    }
}

impl std::fmt::Display for LispType
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	f.write_str(match self {
	    Self::List => "list",
	    Self::String => "string",
	    Self::Integer => "integer",
	    Self::Float => "float",
	    Self::Atom => "nil",
	})
    }
}

pub trait LispExt
{
    /// Try to get `car` and `cdr`
    fn try_split<'a>(&'a self) -> Result<(&'a Sexp, &'a [Sexp]), Error>;
}

impl LispExt for Vec<Sexp>
{
    fn try_split<'a>(&'a self) -> Result<(&'a Sexp, &'a [Sexp]), Error>
    {
	if self.len() > 1 {
	    Ok((&self[0], &self[1..]))
	} else if self.len() > 0{
	    Ok((&self[0], &[]))
	} else {
	    Err(Error::UnexpectedEmpty)
	}
    }
}

// Sexp doesn't use try_from(), so...
pub trait TryIntoExt: Sized
{
    fn try_into_list(self) -> Result<Vec<Sexp>, Error>;
    fn try_into_atom(self) -> Result<Atom, Error>;

    fn try_into_string(self) -> Result<String, Error>;
    fn try_into_int(self) -> Result<i64, Error>;
    fn try_into_float(self) -> Result<f64, Error>;
}

impl TryIntoExt for Sexp
{
    fn try_into_list(self) -> Result<Vec<Sexp>, Error>
    {
	match self {
	    Sexp::List(this) => Ok(this),
	    other => Err(Error::bad_type(LispType::List, other)),
	}
    }
    fn try_into_atom(self) -> Result<Atom, Error>
    {
	match self {
	    Sexp::Atom(this) => Ok(this),
	    other => Err(Error::bad_type(LispType::Atom, other)),
	}
    }

    fn try_into_string(self) -> Result<String, Error>
    {
	match self.try_into_atom() {
	    Ok(Atom::S(this)) => Ok(this),
	    other => Err(Error::bad_type(LispType::String, other)),
	}
    }
    
    fn try_into_int(self) -> Result<i64, Error>
    {	
	match self.try_into_atom() {
	    Ok(Atom::I(this)) => Ok(this),
	    other => Err(Error::bad_type(LispType::Integer, other)),
	}
    }
    fn try_into_float(self) -> Result<f64, Error>
    {
	match self.try_into_atom() {
	    Ok(Atom::F(this)) => Ok(this),
	    other => Err(Error::bad_type(LispType::Float, other)),
	}
    }
}

impl TryIntoExt for Atom
{
    #[inline]
    fn try_into_list(self) -> Result<Vec<Sexp>, Error>
    {
	Err(Error::bad_type(LispType::List, self))
    }
    #[inline]
    fn try_into_atom(self) -> Result<Atom, Error>
    {
	Ok(self)
    }

    fn try_into_string(self) -> Result<String, Error>
    {
	match self {
	    Atom::S(this) => Ok(this),
	    other => Err(Error::bad_type(LispType::String, other)),
	}
    }
    
    fn try_into_int(self) -> Result<i64, Error>
    {
	match self {
	    Atom::I(this) => Ok(this),
	    other => Err(Error::bad_type(LispType::Integer, other)),
	}
    }
    fn try_into_float(self) -> Result<f64, Error>
    {
	match self {
	    Atom::F(this) => Ok(this),
	    other => Err(Error::bad_type(LispType::Float, other)),
	}
    }
    
}


// To avoid some `clone()`s
pub trait TryGetExt: Sized
{
    fn try_get_list(&self) -> Result<&[Sexp], Error>;
    fn try_get_atom(&self) -> Result<&Atom, Error>;

    fn try_get_string(&self) -> Result<&String, Error>;
    fn try_get_int(&self) -> Result<&i64, Error>;
    fn try_get_float(&self) -> Result<&f64, Error>;
}

impl TryGetExt for Sexp
{
    fn try_get_list(&self) -> Result<&[Sexp], Error>
    {
	match self {
	    Self::List(list) => Ok(&list[..]),
	    other => Err(Error::bad_type(LispType::List, other)),
	}
    }
    fn try_get_atom(&self) -> Result<&Atom, Error>
    {
	match self {
	    Self::Atom(atom) => Ok(atom),
	    other => Err(Error::bad_type(LispType::Atom, other)),
	}
    }

    fn try_get_string(&self) -> Result<&String, Error>
    {
	match self {
	    Self::Atom(Atom::S(string)) => Ok(string),
	    other => Err(Error::bad_type(LispType::String, other)),
	}
    }
    fn try_get_int(&self) -> Result<&i64, Error>
    {
	match self {
	    Self::Atom(Atom::I(int)) => Ok(int),
	    other => Err(Error::bad_type(LispType::Integer, other)),
	}
    }
    fn try_get_float(&self) -> Result<&f64, Error>
    {	
	match self {
	    Self::Atom(Atom::F(float)) => Ok(float),
	    other => Err(Error::bad_type(LispType::Float, other)),
	}
    }
}