use std::fmt;

/// The type of errors returned by helper functions on `Term`
#[derive(Debug, Clone)]
pub enum TypeError {
    /// The term could not be decoded in the given type
    WrongType(&'static str),
    /// The term is not an array of the requested length
    WrongLength(usize, usize),
    /// The dictionnary is missing a key
    MissingKey(String),
    /// The dictionnary contains an invalid key
    UnexpectedKey(String),
    /// The underlying raw string contains garbage (should not happen in theory)
    Garbage,
}

impl From<std::str::Utf8Error> for TypeError {
    fn from(_x: std::str::Utf8Error) -> TypeError {
        TypeError::Garbage
    }
}

impl std::fmt::Display for TypeError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            TypeError::WrongType(t) => write!(f, "Not a {}", t),
            TypeError::WrongLength(n, m) => write!(f, "Expected {} items, got {}", m, n),
            TypeError::MissingKey(k) => write!(f, "Missing key `{}` in dict", k),
            TypeError::UnexpectedKey(k) => write!(f, "Spurrious/unexpected key `{}` in dict", k),
            TypeError::Garbage => write!(f, "Garbage in underlying data"),
        }
    }
}