iceoryx2 0.9.0

// Copyright (c) 2023 Contributors to the Eclipse Foundation
//
// See the NOTICE file(s) distributed with this work for additional
// information regarding copyright ownership.
//
// This program and the accompanying materials are made available under the
// terms of the Apache Software License 2.0 which is available at
// https://www.apache.org/licenses/LICENSE-2.0, or the MIT license
// which is available at https://opensource.org/licenses/MIT.
//
// SPDX-License-Identifier: Apache-2.0 OR MIT

//! # Example
//!
//! See [`crate::service`]
//!
pub use crate::port::event_id::EventId;

use alloc::format;

use iceoryx2_bb_container::relocatable_option::RelocatableOption;
use iceoryx2_bb_posix::clock::Time;
use iceoryx2_cal::dynamic_storage::DynamicStorageCreateError;
use iceoryx2_log::{fail, fatal_panic};

use crate::service::builder::OpenDynamicStorageFailure;
use crate::service::dynamic_config::MessagingPatternSettings;
use crate::service::port_factory::event;
use crate::service::static_config::messaging_pattern::MessagingPattern;
use crate::service::*;
use crate::service::{self, dynamic_config::event::DynamicConfigSettings};

use self::attribute::{AttributeSpecifier, AttributeVerifier};
use builder::RETRY_LIMIT;
use static_config::event::Deadline;

use super::ServiceState;

/// Failures that can occur when an existing [`MessagingPattern::Event`] [`Service`] shall be opened.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum EventOpenError {
    /// The [`Service`] does not exist.
    DoesNotExist,
    /// The process has not enough permissions to open the [`Service`]
    InsufficientPermissions,
    /// Some underlying resources of the [`Service`] do not exist which indicate a corrupted
    /// [`Service`]state.
    ServiceInCorruptedState,
    /// The [`Service`] has the wrong messaging pattern.
    IncompatibleMessagingPattern,
    /// The [`AttributeVerifier`] required attributes that the [`Service`] does not satisfy.
    IncompatibleAttributes,
    /// Errors that indicate either an implementation issue or a wrongly configured system.
    InternalFailure,
    /// The [`Service`]s deadline settings are not equal the the user given requirements.
    IncompatibleDeadline,
    /// The event id that is emitted for a newly created [`Notifier`](crate::port::notifier::Notifier)
    /// does not fit the required event id.
    IncompatibleNotifierCreatedEvent,
    /// The event id that is emitted if a [`Notifier`](crate::port::notifier::Notifier) is dropped
    /// does not fit the required event id.
    IncompatibleNotifierDroppedEvent,
    /// The event id that is emitted if a [`Notifier`](crate::port::notifier::Notifier) is
    /// identified as dead does not fit the required event id.
    IncompatibleNotifierDeadEvent,
    /// The [`Service`]s creation timeout has passed and it is still not initialized. Can be caused
    /// by a process that crashed during [`Service`] creation.
    HangsInCreation,
    /// The [`Service`] supports less [`Notifier`](crate::port::notifier::Notifier)s than requested.
    DoesNotSupportRequestedAmountOfNotifiers,
    /// The [`Service`] supports less [`Listener`](crate::port::listener::Listener)s than requested.
    DoesNotSupportRequestedAmountOfListeners,
    /// The [`Service`] supported [`EventId`] is smaller than the requested max [`EventId`].
    DoesNotSupportRequestedMaxEventId,
    /// The [`Service`] supports less [`Node`](crate::node::Node)s than requested.
    DoesNotSupportRequestedAmountOfNodes,
    /// The maximum number of [`Node`](crate::node::Node)s have already opened the [`Service`].
    ExceedsMaxNumberOfNodes,
    /// The [`Service`] is marked for destruction and currently cleaning up since no one is using it anymore.
    /// When the call creation call is repeated with a little delay the [`Service`] should be
    /// recreatable.
    IsMarkedForDestruction,
}

impl core::fmt::Display for EventOpenError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "EventOpenError::{self:?}")
    }
}

impl core::error::Error for EventOpenError {}

impl From<ServiceState> for EventOpenError {
    fn from(value: ServiceState) -> Self {
        match value {
            ServiceState::IncompatibleMessagingPattern => {
                EventOpenError::IncompatibleMessagingPattern
            }
            ServiceState::InsufficientPermissions => EventOpenError::InsufficientPermissions,
            ServiceState::HangsInCreation => EventOpenError::HangsInCreation,
            ServiceState::Corrupted => EventOpenError::ServiceInCorruptedState,
        }
    }
}

/// Failures that can occur when a new [`MessagingPattern::Event`] [`Service`] shall be created.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum EventCreateError {
    /// Some underlying resources of the [`Service`] are either missing, corrupted or unaccessible.
    ServiceInCorruptedState,
    /// Errors that indicate either an implementation issue or a wrongly configured system.
    InternalFailure,
    /// Multiple processes are trying to create the same [`Service`].
    IsBeingCreatedByAnotherInstance,
    /// The [`Service`] already exists.
    AlreadyExists,
    /// The [`Service`]s creation timeout has passed and it is still not initialized. Can be caused
    /// by a process that crashed during [`Service`] creation.
    HangsInCreation,
    /// The process has insufficient permissions to create the [`Service`].
    InsufficientPermissions,
}

impl core::fmt::Display for EventCreateError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "EventCreateError::{self:?}")
    }
}

impl core::error::Error for EventCreateError {}

impl From<ServiceState> for EventCreateError {
    fn from(value: ServiceState) -> Self {
        match value {
            ServiceState::IncompatibleMessagingPattern => EventCreateError::AlreadyExists,
            ServiceState::InsufficientPermissions => EventCreateError::InsufficientPermissions,
            ServiceState::HangsInCreation => EventCreateError::HangsInCreation,
            ServiceState::Corrupted => EventCreateError::ServiceInCorruptedState,
        }
    }
}

/// Failures that can occur when a [`MessagingPattern::Event`] [`Service`] shall be opened or
/// created.
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum EventOpenOrCreateError {
    /// Failures that can occur when an event [`Service`] is opened.
    EventOpenError(EventOpenError),
    /// Failures that can occur when an event [`Service`] is created.
    EventCreateError(EventCreateError),
    /// Can occur when another process creates and removes the same [`Service`] repeatedly with a
    /// high frequency.
    SystemInFlux,
}

impl From<EventOpenError> for EventOpenOrCreateError {
    fn from(value: EventOpenError) -> Self {
        EventOpenOrCreateError::EventOpenError(value)
    }
}

impl From<EventCreateError> for EventOpenOrCreateError {
    fn from(value: EventCreateError) -> Self {
        EventOpenOrCreateError::EventCreateError(value)
    }
}

impl core::fmt::Display for EventOpenOrCreateError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "EventOpenOrCreateError::{self:?}")
    }
}

impl core::error::Error for EventOpenOrCreateError {}

impl From<ServiceState> for EventOpenOrCreateError {
    fn from(value: ServiceState) -> Self {
        EventOpenOrCreateError::EventOpenError(value.into())
    }
}

/// Builder to create new [`MessagingPattern::Event`] based [`Service`]s
///
/// # Example
///
/// See [`crate::service`]
#[derive(Debug, Clone)]
pub struct Builder<ServiceType: service::Service> {
    base: builder::BuilderWithServiceType<ServiceType>,
    verify_max_notifiers: bool,
    verify_max_listeners: bool,
    verify_max_nodes: bool,
    verify_event_id_max_value: bool,
    verify_deadline: bool,
    verify_notifier_created_event: bool,
    verify_notifier_dropped_event: bool,
    verify_notifier_dead_event: bool,
}

impl<ServiceType: service::Service> Builder<ServiceType> {
    pub(crate) fn new(base: builder::BuilderWithServiceType<ServiceType>) -> Self {
        let mut new_self = Self {
            base,
            verify_max_notifiers: false,
            verify_max_listeners: false,
            verify_max_nodes: false,
            verify_event_id_max_value: false,
            verify_deadline: false,
            verify_notifier_dead_event: false,
            verify_notifier_created_event: false,
            verify_notifier_dropped_event: false,
        };

        new_self.base.service_config.messaging_pattern = MessagingPattern::Event(
            static_config::event::StaticConfig::new(new_self.base.shared_node.config()),
        );

        new_self
    }

    fn config_details(&mut self) -> &mut static_config::event::StaticConfig {
        match self.base.service_config.messaging_pattern {
            MessagingPattern::Event(ref mut v) => v,
            _ => {
                fatal_panic!(from self, "This should never happen! Accessing wrong messaging pattern in Event builder!");
            }
        }
    }

    /// Enables the deadline property of the service. There must be a notification emitted by any
    /// [`Notifier`](crate::port::notifier::Notifier) after at least the provided `deadline`.
    pub fn deadline(mut self, deadline: Duration) -> Self {
        self.config_details().deadline = RelocatableOption::Some(Deadline {
            value: deadline.into(),
            creation_time: Time::default(),
        });
        self.verify_deadline = true;
        self
    }

    /// Disables the deadline property of the service. [`Notifier`](crate::port::notifier::Notifier)
    /// can signal notifications at any rate.
    pub fn disable_deadline(mut self) -> Self {
        self.config_details().deadline = RelocatableOption::None;
        self.verify_deadline = true;
        self
    }

    /// If the [`Service`] is created it defines how many [`Node`](crate::node::Node)s shall
    /// be able to open it in parallel. If an existing [`Service`] is opened it defines how many
    /// [`Node`](crate::node::Node)s must be at least supported.
    pub fn max_nodes(mut self, value: usize) -> Self {
        self.config_details().max_nodes = value;
        self.verify_max_nodes = true;
        self
    }

    /// If the [`Service`] is created it set the greatest supported [`UniqueNodeId`] value
    /// If an existing [`Service`] is opened it defines the value size the [`UniqueNodeId`]
    /// must at least support.
    pub fn event_id_max_value(mut self, value: usize) -> Self {
        self.config_details().event_id_max_value = value;
        self.verify_event_id_max_value = true;
        self
    }

    /// If the [`Service`] is created it defines how many [`crate::port::notifier::Notifier`] shall
    /// be supported at most. If an existing [`Service`] is opened it defines how many
    /// [`crate::port::notifier::Notifier`] must be at least supported.
    pub fn max_notifiers(mut self, value: usize) -> Self {
        self.config_details().max_notifiers = value;
        self.verify_max_notifiers = true;
        self
    }

    /// If the [`Service`] is created it defines how many [`crate::port::listener::Listener`] shall
    /// be supported at most. If an existing [`Service`] is opened it defines how many
    /// [`crate::port::listener::Listener`] must be at least supported.
    pub fn max_listeners(mut self, value: usize) -> Self {
        self.config_details().max_listeners = value;
        self.verify_max_listeners = true;
        self
    }

    /// If the [`Service`] is created it defines the event that shall be emitted by every newly
    /// created [`Notifier`](crate::port::notifier::Notifier).
    pub fn notifier_created_event(mut self, value: EventId) -> Self {
        self.config_details().notifier_created_event = RelocatableOption::Some(value.as_value());
        self.verify_notifier_created_event = true;
        self
    }

    /// If the [`Service`] is created it disables the event that shall be emitted by every newly
    /// created [`Notifier`](crate::port::notifier::Notifier).
    pub fn disable_notifier_created_event(mut self) -> Self {
        self.config_details().notifier_created_event = RelocatableOption::None;
        self.verify_notifier_created_event = true;
        self
    }

    /// If the [`Service`] is created it defines the event that shall be emitted by every
    /// [`Notifier`](crate::port::notifier::Notifier) before it is dropped.
    pub fn notifier_dropped_event(mut self, value: EventId) -> Self {
        self.config_details().notifier_dropped_event = RelocatableOption::Some(value.as_value());
        self.verify_notifier_dropped_event = true;
        self
    }

    /// If the [`Service`] is created it disables the event that shall be emitted by every
    /// [`Notifier`](crate::port::notifier::Notifier) before it is dropped.
    pub fn disable_notifier_dropped_event(mut self) -> Self {
        self.config_details().notifier_dropped_event = RelocatableOption::None;
        self.verify_notifier_dropped_event = true;
        self
    }

    /// If the [`Service`] is created it defines the event that shall be emitted when a
    /// [`Notifier`](crate::port::notifier::Notifier) is identified as dead.
    pub fn notifier_dead_event(mut self, value: EventId) -> Self {
        self.config_details().notifier_dead_event = RelocatableOption::Some(value.as_value());
        self.verify_notifier_dead_event = true;
        self
    }

    /// If the [`Service`] is created it disables the event that shall be emitted when a
    /// [`Notifier`](crate::port::notifier::Notifier) is identified as dead.
    pub fn disable_notifier_dead_event(mut self) -> Self {
        self.config_details().notifier_dead_event = RelocatableOption::None;
        self.verify_notifier_dead_event = true;
        self
    }

    /// If the [`Service`] exists, it will be opened otherwise a new [`Service`] will be
    /// created.
    pub fn open_or_create(self) -> Result<event::PortFactory<ServiceType>, EventOpenOrCreateError> {
        self.open_or_create_with_attributes(&AttributeVerifier::new())
    }

    /// If the [`Service`] exists, it will be opened otherwise a new [`Service`] will be
    /// created. It defines a set of attributes. If the [`Service`] already exists all attribute
    /// requirements must be satisfied otherwise the open process will fail. If the [`Service`]
    /// does not exist the required attributes will be defined in the [`Service`].
    pub fn open_or_create_with_attributes(
        mut self,
        verifier: &AttributeVerifier,
    ) -> Result<event::PortFactory<ServiceType>, EventOpenOrCreateError> {
        let msg = "Unable to open or create event service";

        let mut retry_count = 0;
        loop {
            if RETRY_LIMIT < retry_count {
                fail!(from self,
                      with EventOpenOrCreateError::SystemInFlux,
                      "{} since an instance is creating and removing the same service repeatedly.",
                      msg);
            }
            retry_count += 1;

            match self.base.is_service_available(msg)? {
                Some(_) => return Ok(self.open_with_attributes(verifier)?),
                None => {
                    match self
                        .create_impl(&AttributeSpecifier(verifier.required_attributes().clone()))
                    {
                        Ok(factory) => return Ok(factory),
                        Err(EventCreateError::AlreadyExists)
                        | Err(EventCreateError::IsBeingCreatedByAnotherInstance) => {
                            continue;
                        }
                        Err(e) => return Err(e.into()),
                    }
                }
            }
        }
    }

    /// Opens an existing [`Service`].
    pub fn open(self) -> Result<event::PortFactory<ServiceType>, EventOpenError> {
        self.open_with_attributes(&AttributeVerifier::new())
    }

    /// Opens an existing [`Service`] with attribute requirements. If the defined attribute
    /// requirements are not satisfied the open process will fail.
    pub fn open_with_attributes(
        mut self,
        verifier: &AttributeVerifier,
    ) -> Result<event::PortFactory<ServiceType>, EventOpenError> {
        let msg = "Unable to open event service";

        let mut service_open_retry_count = 0;
        loop {
            match self.base.is_service_available(msg)? {
                None => {
                    fail!(from self, with EventOpenError::DoesNotExist,
                        "{} since the event does not exist.", msg);
                }
                Some((static_config, static_storage)) => {
                    let event_static_config =
                        self.verify_service_configuration(&static_config, verifier)?;

                    let service_tag = self
                        .base
                        .create_node_service_tag(msg, EventOpenError::InternalFailure)?;

                    let dynamic_config = match self.base.open_dynamic_config_storage() {
                        Ok(v) => v,
                        Err(OpenDynamicStorageFailure::IsMarkedForDestruction) => {
                            fail!(from self, with EventOpenError::IsMarkedForDestruction,
                                "{} since the service is marked for destruction.", msg);
                        }
                        Err(OpenDynamicStorageFailure::ExceedsMaxNumberOfNodes) => {
                            fail!(from self, with EventOpenError::ExceedsMaxNumberOfNodes,
                                "{} since it would exceed the maximum number of supported nodes.", msg);
                        }
                        Err(OpenDynamicStorageFailure::DynamicStorageOpenError(
                            DynamicStorageOpenError::DoesNotExist,
                        )) => {
                            fail!(from self, with EventOpenError::ServiceInCorruptedState,
                                "{} since the dynamic segment of the service is missing.", msg);
                        }
                        Err(e) => {
                            if self.base.is_service_available(msg)?.is_none() {
                                fail!(from self, with EventOpenError::DoesNotExist,
                                    "{} since the event does not exist.", msg);
                            }

                            service_open_retry_count += 1;

                            if RETRY_LIMIT < service_open_retry_count {
                                fail!(from self, with EventOpenError::ServiceInCorruptedState,
                                "{} since the dynamic service information could not be opened ({:?}). This could indicate a corrupted system or a misconfigured system where services are created/removed with a high frequency.",
                                msg, e);
                            }

                            continue;
                        }
                    };

                    self.base.service_config.messaging_pattern =
                        MessagingPattern::Event(event_static_config);

                    if let Some(service_tag) = service_tag {
                        service_tag.release_ownership();
                    }

                    return Ok(event::PortFactory::new(service::ServiceState::new(
                        static_config,
                        self.base.shared_node,
                        dynamic_config,
                        static_storage,
                        NoResource,
                    )));
                }
            }
        }
    }

    /// Creates a new [`Service`].
    pub fn create(mut self) -> Result<event::PortFactory<ServiceType>, EventCreateError> {
        self.create_impl(&AttributeSpecifier::new())
    }

    /// Creates a new [`Service`] with a set of attributes.
    pub fn create_with_attributes(
        mut self,
        attributes: &AttributeSpecifier,
    ) -> Result<event::PortFactory<ServiceType>, EventCreateError> {
        self.create_impl(attributes)
    }

    fn create_impl(
        &mut self,
        attributes: &AttributeSpecifier,
    ) -> Result<event::PortFactory<ServiceType>, EventCreateError> {
        self.adjust_attributes_to_meaningful_values();

        let msg = "Unable to create event service";

        match self.base.is_service_available(msg)? {
            None => {
                let service_tag = self
                    .base
                    .create_node_service_tag(msg, EventCreateError::InternalFailure)?;

                if let RelocatableOption::Some(ref mut deadline) =
                    self.base.service_config.event_mut().deadline
                {
                    let now = fail!(from self, when Time::now(),
                                with EventCreateError::InternalFailure,
                                "{} since the current system time could not be acquired.", msg);

                    deadline.creation_time = now;
                }

                let static_config = match self.base.create_static_config_storage() {
                    Ok(c) => c,
                    Err(StaticStorageCreateError::AlreadyExists) => {
                        fail!(from self, with EventCreateError::AlreadyExists,
                           "{} since the service already exists.", msg);
                    }
                    Err(StaticStorageCreateError::Creation) => {
                        fail!(from self, with EventCreateError::IsBeingCreatedByAnotherInstance,
                            "{} since the service is being created by another instance.", msg);
                    }
                    Err(StaticStorageCreateError::InsufficientPermissions) => {
                        fail!(from self, with EventCreateError::InsufficientPermissions,
                            "{} since the static service information could not be created due to insufficient permissions.", msg);
                    }
                    Err(e) => {
                        fail!(from self, with EventCreateError::InternalFailure,
                            "{} since the static service information could not be created ({:?}).", msg, e);
                    }
                };

                let event_config = self.base.service_config.event();

                let dynamic_config_setting = DynamicConfigSettings {
                    number_of_listeners: event_config.max_listeners,
                    number_of_notifiers: event_config.max_notifiers,
                };

                let dynamic_config = match self.base.create_dynamic_config_storage(
                    &MessagingPatternSettings::Event(dynamic_config_setting),
                    dynamic_config::event::DynamicConfig::memory_size(&dynamic_config_setting),
                    event_config.max_nodes,
                ) {
                    Ok(dynamic_config) => dynamic_config,
                    Err(DynamicStorageCreateError::AlreadyExists) => {
                        fail!(from self, with EventCreateError::ServiceInCorruptedState,
                            "{} since there exist an old dynamic config from a previous instance of the service.", msg);
                    }
                    Err(e) => {
                        fail!(from self, with EventCreateError::InternalFailure,
                            "{} since the dynamic service segment could not be created ({:?}).", msg, e);
                    }
                };

                self.base.service_config.attributes = attributes.0.clone();

                let service_config = fail!(from self, when ServiceType::ConfigSerializer::serialize(&self.base.service_config),
                                            with EventCreateError::ServiceInCorruptedState,
                                            "{} since the configuration could not be serialized.", msg);

                // only unlock the static details when the service is successfully created
                let unlocked_static_details = fail!(from self, when static_config.unlock(service_config.as_slice()),
                            with EventCreateError::ServiceInCorruptedState,
                            "{} since the configuration could not be written to the static storage.", msg);

                unlocked_static_details.release_ownership();
                if let Some(service_tag) = service_tag {
                    service_tag.release_ownership();
                }

                Ok(event::PortFactory::new(service::ServiceState::new(
                    self.base.service_config.clone(),
                    self.base.shared_node.clone(),
                    dynamic_config,
                    unlocked_static_details,
                    NoResource,
                )))
            }
            Some(_) => {
                fail!(from self, with EventCreateError::AlreadyExists,
                    "{} since the service already exists.", msg);
            }
        }
    }

    fn adjust_attributes_to_meaningful_values(&mut self) {
        let origin = format!("{self:?}");
        let settings = self.base.service_config.event_mut();

        if settings.max_notifiers == 0 {
            warn!(from origin, "Setting the maximum amount of notifiers to 0 is not supported. Adjust it to 1, the smallest supported value.");
            settings.max_notifiers = 1;
        }

        if settings.max_listeners == 0 {
            warn!(from origin, "Setting the maximum amount of listeners to 0 is not supported. Adjust it to 1, the smallest supported value.");
            settings.max_listeners = 1;
        }

        if settings.max_nodes == 0 {
            warn!(from origin, "Setting the maximum amount of nodes to 0 is not supported. Adjust it to 1, the smallest supported value.");
            settings.max_nodes = 1;
        }
    }

    fn verify_service_configuration(
        &self,
        existing_settings: &static_config::StaticConfig,
        required_attributes: &AttributeVerifier,
    ) -> Result<static_config::event::StaticConfig, EventOpenError> {
        let msg = "Unable to open event";

        let existing_attributes = existing_settings.attributes();
        if let Err(incompatible_key) = required_attributes.verify_requirements(existing_attributes)
        {
            fail!(from self, with EventOpenError::IncompatibleAttributes,
                "{} due to incompatible service attribute key {}. The following attributes {:?} are required but the service has the attributes {:?}.",
                msg, incompatible_key, required_attributes, existing_attributes);
        }

        let required_settings = self.base.service_config.event();
        let existing_settings = match &existing_settings.messaging_pattern {
            MessagingPattern::Event(v) => v,
            p => {
                fail!(from self, with EventOpenError::IncompatibleMessagingPattern,
                "{} since a service with the messaging pattern {:?} exists but MessagingPattern::Event is required.", msg, p);
            }
        };

        if self.verify_max_notifiers
            && existing_settings.max_notifiers < required_settings.max_notifiers
        {
            fail!(from self, with EventOpenError::DoesNotSupportRequestedAmountOfNotifiers,
                "{} since the event supports only {} notifiers but a support of {} notifiers was requested.",
                msg, existing_settings.max_notifiers, required_settings.max_notifiers);
        }

        if self.verify_max_listeners
            && existing_settings.max_listeners < required_settings.max_listeners
        {
            fail!(from self, with EventOpenError::DoesNotSupportRequestedAmountOfListeners,
                "{} since the event supports only {} listeners but a support of {} listeners was requested.",
                msg, existing_settings.max_notifiers, required_settings.max_listeners);
        }

        if self.verify_event_id_max_value
            && existing_settings.event_id_max_value < required_settings.event_id_max_value
        {
            fail!(from self, with EventOpenError::DoesNotSupportRequestedMaxEventId,
                "{} since the event supports only EventIds with a value of at most {} a support of {} was requested.",
                msg, existing_settings.event_id_max_value, required_settings.event_id_max_value);
        }

        if self.verify_max_nodes && existing_settings.max_nodes < required_settings.max_nodes {
            fail!(from self, with EventOpenError::DoesNotSupportRequestedAmountOfNodes,
                "{} since the event supports only {} nodes but {} are required.",
                msg, existing_settings.max_nodes, required_settings.max_nodes);
        }

        if self.verify_notifier_created_event
            && existing_settings.notifier_created_event != required_settings.notifier_created_event
        {
            fail!(from self, with EventOpenError::IncompatibleNotifierCreatedEvent,
                "{} since the notifier_created_event id is {:?} but the value {:?} is required.",
                msg, existing_settings.notifier_created_event, required_settings.notifier_created_event);
        }

        if self.verify_notifier_dropped_event
            && existing_settings.notifier_dropped_event != required_settings.notifier_dropped_event
        {
            fail!(from self, with EventOpenError::IncompatibleNotifierDroppedEvent,
                "{} since the notifier_dropped_event id is {:?} but the value {:?} is required.",
                msg, existing_settings.notifier_dropped_event, required_settings.notifier_dropped_event);
        }

        if self.verify_notifier_dead_event
            && existing_settings.notifier_dead_event != required_settings.notifier_dead_event
        {
            fail!(from self, with EventOpenError::IncompatibleNotifierDeadEvent,
                "{} since the notifier_dead_event id is {:?} but the value {:?} is required.",
                msg, existing_settings.notifier_dead_event, required_settings.notifier_dead_event);
        }

        if self.verify_deadline
            && existing_settings.deadline.map(|v| v.value)
                != required_settings.deadline.map(|v| v.value)
        {
            fail!(from self, with EventOpenError::IncompatibleDeadline,
                "{} since the deadline is {:?} but a deadline of {:?} is required.",
                msg, existing_settings.deadline, required_settings.deadline);
        }

        Ok(*existing_settings)
    }
}