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use std::error;
use std::fmt::{self, Formatter, Display};
use std::result;

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

impl Error{
    pub fn new(desc: &str) -> Error{
        Error{
            description: desc.to_owned(),
            cause: None,
        }
    }

    pub fn with_cause<'a, E: 'static + error::Error, C: Into<Option<E>>>(desc: &str, cause: C) -> Error{
        Error{
            description: desc.to_owned(),
            cause: cause.into().map(|e| Box::new(e) as Box<error::Error>),
        }
    }
}


impl error::Error for Error{
    fn description(&self) -> &str{
        &self.description
    }

    fn cause(&self) -> Option<&error::Error>{
        self.cause.as_ref().map(|e| &**e)
    }
}

impl Display for Error{
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result{
        fmt.write_str(&self.description)?;
        fmt.write_str("\n")?;
        if let Some(cause) = self.cause.as_ref(){
            fmt.write_str("cause: ")?;
            cause.fmt(fmt)
        }else{
            Ok(())
        }
    }
}


impl<'a> From<&'a str> for Error{
    fn from(desc: &str) -> Error{
        Error::new(desc)
    }
}

pub type Result<T> = result::Result<T, Error>;