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use std::error::Error;
use std::fmt::{Debug, Display, Formatter};

const SHUTDOWN_MESSAGE: &str = "could not accept the command for execution, probably the cache is being shutdown.";

/// The execution of every write operation is returned a [`crate::cache::command::command_executor::CommandSendResult`].
///
/// `CommandSendResult` wraps `CommandSendError` that is encountered when there is an error in sending a command to `crate::cache::command::command_executor::CommandExecutor`.
///
/// `CommandSendError` is also returned to the clients if an attempt is made to perform any operation say `put`, `delete`, while the cache is being shutdown.
pub struct CommandSendError {
    command_description: String,
}

impl CommandSendError {
    pub(crate) fn new(command_description: String) -> Self {
        CommandSendError {
            command_description
        }
    }

    pub(crate) fn shutdown() -> Self {
        CommandSendError {
            command_description: SHUTDOWN_MESSAGE.to_string()
        }
    }
}

/// Display implementation for `CommandSendError`. Currently, both `Display` and `Debug` return the same message.
impl Display for CommandSendError {
    fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result {
        write!(
            formatter,
            "{} Command description: {}",
            SHUTDOWN_MESSAGE,
            self.command_description
        )
    }
}

/// Debug implementation for `CommandSendError`. Currently, both `Display` and `Debug` return the same message.
impl Debug for CommandSendError {
    fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result {
        write!(
            formatter,
            "{} Command description: {}",
            SHUTDOWN_MESSAGE,
            self.command_description
        )
    }
}

/// Error implementation for `CommandSendError`.
impl Error for CommandSendError {}

#[cfg(test)]
mod tests {
    use crate::cache::command::error::CommandSendError;

    #[test]
    fn command_send_error_display() {
        let error = CommandSendError::new("put".to_string());
        assert_eq!(
            format!("{}", error),
            "could not accept the command for execution, probably the cache is being shutdown. Command description: put",
        );
    }

    #[test]
    fn command_send_error_debug() {
        let error = CommandSendError::new("put".to_string());
        assert_eq!(
            format!("{:?}", error),
            "could not accept the command for execution, probably the cache is being shutdown. Command description: put",
        );
    }
}