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use std::fmt;

pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;

#[derive(Debug)]
pub struct Error {
    msg: String,
    cause: Option<Box<dyn std::error::Error>>
}

impl Error {
    pub fn new(msg: &str) -> Error {
        Error {
            msg: msg.into(),
            cause: None
        }
    }
}

impl std::error::Error for Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.cause.as_ref().map(Box::as_ref)
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(&self.msg)?;
        if let Some(cause) = &self.cause {
            write!(f, "\n\tcaused by: {}", cause)?;
        }
        Ok(())
    }
}

pub trait ErrorExt {
    fn wrap(self, msg: &str) -> Error;
}

impl<T: Into<Box<dyn std::error::Error>>> ErrorExt for T {
    fn wrap(self, msg: &str) -> Error {
        Error {
            msg: msg.into(),
            cause: Some(self.into())
        }
    }
}

pub trait ResultExt<T> {
    fn wrap_err(self, msg: &str) -> std::result::Result<T, Error>;
}

impl<T, E: ErrorExt> ResultExt<T> for std::result::Result<T, E> {
    fn wrap_err(self, msg: &str) -> std::result::Result<T, Error> {
        self.map_err(|err| err.wrap(msg))
    }
}