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#![allow(dead_code)]

use failure::{Backtrace, Context, Fail};
use std::fmt;
use std::path::{Path, PathBuf};
use std::result;

/// A type alias for handling errors throughout grue
pub type Result<T> = result::Result<T, Error>;

/// An error that can occur
#[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()
	}

	pub fn memory<T: AsRef<str>>(msg: T) -> Error {
		Error::from(ErrorKind::Memory(msg.as_ref().to_string()))
	}

	pub fn parse<T: AsRef<str>>(msg: T) -> Error {
		Error::from(ErrorKind::Parse(msg.as_ref().to_string()))
	}

	pub fn bug<T: AsRef<str>>(msg: T) -> Error {
		Error::from(ErrorKind::Bug(msg.as_ref().to_string()))
	}

	pub fn config<T: AsRef<str>>(msg: T) -> Error {
		Error::from(ErrorKind::Config(msg.as_ref().to_string()))
	}

	pub fn number<E: Fail>(err: E) -> Error {
		Error::from(err.context(ErrorKind::Number))
	}

	pub fn io<E: Fail>(err: E) -> Error {
		Error::from(err.context(ErrorKind::Io))
	}
}

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 {
	/// An error that occurred while accessing or allocating memory
	Memory(String),

	/// An error that occurred while parsing a data source
	Parse(String),

	/// An error that occurred while working with a file path.
	Path(PathBuf),

	/// Generally, these errors correspond to bugs in this library.
	Bug(String),

	/// An error occurred while reading/writing a configuration
	Config(String),

	/// An unexpected I/O error occurred.
	Io,

	/// An error occurred while parsing a number in a free-form query.
	Number,

	/// 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 ErrorKind {
	/// A convenience routine for creating an error associated with a path.
	pub(crate) fn path<P: AsRef<Path>>(path: P) -> ErrorKind {
		ErrorKind::Path(path.as_ref().to_path_buf())
	}
}

impl fmt::Display for ErrorKind {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		match *self {
			ErrorKind::Memory(ref msg) => write!(f, "memory error: {}", msg),
			ErrorKind::Parse(ref msg) => write!(f, "parse error: {}", msg),
			ErrorKind::Path(ref path) => write!(f, "{}", path.display()),
			ErrorKind::Bug(ref msg) => {
				let report = "Please report this bug with a backtrace at \
				              https://github.com/gwihlidal/grue";
				write!(f, "BUG: {}\n{}", msg, report)
			}
			ErrorKind::Config(ref msg) => write!(f, "config error: {}", msg),
			ErrorKind::Io => write!(f, "I/O error"),
			ErrorKind::Number => write!(f, "error parsing number"),
			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 }
	}
}

impl From<std::io::Error> for Error {
	fn from(err: std::io::Error) -> Self {
		Error::io(err)
		//Error::from(Context::new(ErrorKind::Io))
	}
}