use std::error;
use std::fmt;

/// An error that can occur in this crate.
///
/// Generally, this error corresponds to problems with underlying process.
#[derive(Debug)]
pub struct Error {
    source: Vec<Error>,
    kind: ErrorKind,
}

#[derive(Debug)]
#[non_exhaustive]
pub enum ErrorKind {
    Config,
    Fetch, // TODO: merge into "Update" or "Command" type of error? => Have this as an other level of error?
    Compile, // TODO: merge into "Update" or "Command" type of error? => Have this as an other level of error?
    Install, // TODO: merge into "Update" or "Command" type of error? => Have this as an other level of error?
}

impl Error {
    pub(crate) fn new(source: Vec<Error>, kind: ErrorKind) -> Error {
        Error { source, kind }
    }

    /// Return the kind of this error.
    pub fn kind(&self) -> &ErrorKind {
        &self.kind
    }
}

impl error::Error for Error {
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
        if self.source.is_empty() {
            None
        } else {
            Some(&self.source[0])
        }
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use std::error::Error;

        match self.kind {
            ErrorKind::Config => write!(
                f,
                "Could not read configuration file: {}",
                self.source().unwrap()
            ),
            ErrorKind::Fetch => write!(f, "Could not install: {}", self.source().unwrap()),
            ErrorKind::Compile => write!(f, "Could not install: {}", self.source().unwrap()),
            ErrorKind::Install => write!(f, "Could not install: {}", self.source().unwrap()),
        }
    }
}