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// Thank you BurntSushi!!!
// https://www.reddit.com/r/rust/comments/8fecqy/can_someone_show_an_example_of_failure_crate_usage/

use std::fmt;
use std::result;

use failure::{Backtrace, Context, Fail};

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

#[derive(Debug)]
pub struct Error {
    ctx: Context<ErrorKind>,
}

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

    #[allow(dead_code)]
    pub(crate) fn stub_not_found<T: AsRef<str>>(stub: T) -> Error {
        Error::from(ErrorKind::StubNotFound(stub.as_ref().to_string()))
    }

    pub(crate) fn bad_yaml(line: usize, col: usize) -> Error {
        Error::from(ErrorKind::BadYaml { line, col })
    }
}

impl Fail for Error {
    fn cause(&self) -> Option<&dyn Fail> {
        self.ctx.cause()
    }

    fn backtrace(&self) -> Option<&Backtrace> {
        self.ctx.backtrace()
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.ctx.fmt(f)
    }
}

/// The specific kind of error that can occur.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum ErrorKind {
    /// When a criterion with the given stub could not be found
    StubNotFound(String),
    /// When Rubric YAML data is invalid
    BadYaml {
        line: usize,
        col: usize
    },
    /// Hints that destructuring should not be exhaustive.
    ///
    /// This enum may grow additional variants, so this makes sure clients
    /// don't count on exhaustive matching. (Otherwise, adding a new variant
    /// could break existing code.)
    #[doc(hidden)]
    __Nonexhaustive,
}

impl fmt::Display for ErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            ErrorKind::StubNotFound(ref stub) => {
                write!(f, "criterion with stub '{}' not found", stub)
            },
            ErrorKind::BadYaml { line, col } => {
                write!(f, "Bad yaml at line {}, col {}", line, col)
            }
            ErrorKind::__Nonexhaustive => panic!("invalid error"),
        }
    }
}

impl From<ErrorKind> for Error {
    fn from(kind: ErrorKind) -> Error {
        Error::from(Context::new(kind))
    }
}

impl From<Context<ErrorKind>> for Error {
    fn from(ctx: Context<ErrorKind>) -> Error {
        Error { ctx }
    }
}