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use std::error::Error as StdError;
use std::fmt;

use redis::{ErrorKind as RedisErrorKind, RedisError};

pub type InitializationResult<T> = Result<T, InitializationError>;

/// An error specifying what went wrong
/// on a failed checkout
#[derive(Debug)]
pub struct CheckoutError {
    kind: CheckoutErrorKind,
}

/// An error returned from `reool` when a checkout failed
impl CheckoutError {
    pub(crate) fn new(kind: CheckoutErrorKind) -> Self {
        Self { kind }
    }

    /// The kind of the error which can be matched
    pub fn kind(&self) -> CheckoutErrorKind {
        self.kind
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CheckoutErrorKind {
    /// Currently there is no connection available
    NoConnection,
    /// An enqueued request for a checkout that had a timeout
    /// set timed out. A reservation could not be fulfilled.
    CheckoutTimeout,
    /// No connection immediately available and no more
    /// requests can be enqueued to wait for a connection
    /// because the reservation queue has reached it`s limit
    ReservationLimitReached,
    /// No connection because there is no pool available.
    NoPool,
    /// If maximum number of checkout that can be
    /// enqueued has been reached
    CheckoutLimitReached,
    /// Something went wrong executing a task. Keep in
    /// mind that it depends on the `Executor` whether
    /// this error is returned. Some `Executor`s might simply
    /// panic.
    TaskExecution,
}

impl fmt::Display for CheckoutErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let s = match self {
            CheckoutErrorKind::NoConnection => "there are no connections available",
            CheckoutErrorKind::CheckoutTimeout => {
                "there was no connection to checkout available in time"
            }
            CheckoutErrorKind::ReservationLimitReached => "the reservation limit has been reached",
            CheckoutErrorKind::NoPool => "there was no pool available",
            CheckoutErrorKind::CheckoutLimitReached => "checkout limit limit reached",
            CheckoutErrorKind::TaskExecution => "task execution failed",
        };
        f.write_str(s)
    }
}

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

impl StdError for CheckoutError {
    fn description(&self) -> &str {
        match self.kind {
            CheckoutErrorKind::NoConnection => "there are no connections available",
            CheckoutErrorKind::CheckoutTimeout => {
                "there was no connection to checkout available in time"
            }
            CheckoutErrorKind::ReservationLimitReached => "the reservation limit has been reached",
            CheckoutErrorKind::NoPool => "there was no pool available",
            CheckoutErrorKind::CheckoutLimitReached => "checkout limit limit reached",
            CheckoutErrorKind::TaskExecution => "task execution failed",
        }
    }

    fn cause(&self) -> Option<&dyn StdError> {
        None
    }
}

impl From<CheckoutErrorKind> for CheckoutError {
    fn from(kind: CheckoutErrorKind) -> Self {
        Self { kind }
    }
}

impl From<CheckoutError> for RedisError {
    fn from(error: CheckoutError) -> Self {
        (
            RedisErrorKind::IoError,
            "checkout failed",
            error.to_string(),
        )
            .into()
    }
}

/// An initialization has failed
#[derive(Debug)]
pub struct InitializationError {
    message: Option<String>,
    cause: Option<Box<dyn StdError + Send + Sync>>,
}

impl InitializationError {
    pub fn new<T: Into<String>, E: StdError + Send + Sync + 'static>(
        msg: T,
        cause: Option<E>,
    ) -> Self {
        Self {
            message: Some(msg.into()),
            cause: cause.map(|cause| Box::new(cause) as Box<dyn StdError + Send + Sync>),
        }
    }

    pub fn message_only<T: Into<String>>(msg: T) -> Self {
        Self {
            message: Some(msg.into()),
            cause: None,
        }
    }

    pub fn cause_only<E: StdError + Send + Sync + 'static>(cause: E) -> Self {
        Self {
            message: None,
            cause: Some(Box::new(cause)),
        }
    }
}

impl fmt::Display for InitializationError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match (self.message.as_ref(), self.cause.as_ref()) {
            (Some(msg), Some(cause)) => write!(f, "{}: {}", msg, cause),
            (Some(msg), None) => write!(f, "{}", msg),
            (None, Some(cause)) => write!(f, "{}: {}", self.description(), cause),
            (None, None) => write!(f, "{}", self.description()),
        }
    }
}

impl StdError for InitializationError {
    fn description(&self) -> &str {
        "initialization failed"
    }

    fn cause(&self) -> Option<&dyn StdError> {
        self.cause.as_ref().map(|cause| &**cause as &dyn StdError)
    }
}