//
// Describe the commnucation status changes as events.
//
// These implement a mechanism equivalent to what is described in
// Section 2.2.4 Listeners, Conditions, and Wait-sets
//
// Communcation statues are detailed in Figure 2.13 and tables in Section 2.2.4.1
// in DDS Specification v1.4

use crate::dds::qos::QosPolicyId;
use mio::{Evented};
use mio_extras::channel as mio_channel;


/// This trait corresponds to set_listener() of the Entity class in DDS spec. 
/// Types implementing this trait can be registered to a poll and
/// polled for status events. 
pub trait StatusEvented<E> {
	fn as_status_evented(&mut self) -> &dyn Evented;
	fn try_recv_status(&self) -> Option<E>;
}

// Helper object for various DDS Entities
pub(crate) struct StatusReceiver<E> {
	channel_receiver: mio_channel::Receiver<E>,
	enabled: bool, // if not enabled, we should forward status to parent Entity
}

impl<E> StatusReceiver<E> {
	pub fn new(channel_receiver: mio_channel::Receiver<E>) -> StatusReceiver<E> {
		StatusReceiver::<E> {	channel_receiver, enabled: false }
	}
}

impl<E> StatusEvented<E> for StatusReceiver<E> {
	fn as_status_evented(&mut self) -> &dyn Evented {
		self.enabled = true;
		&self.channel_receiver
	}

	fn try_recv_status(&self) -> Option<E> {
		if self.enabled {
			self.channel_receiver.try_recv().ok()
		} else {
			None
		}
	}
}

#[derive(Debug, Clone)]
pub enum DomainParticipantStatus {
	PublisherStatus(PublisherStatus),
	SubscriberStatus(SubscriberStatus),
	TopicStatus(TopicStatus),
}

#[derive(Debug, Clone)]
pub enum SubscriberStatus {
	DataOnReaders,
	DataReaderStatus(DataReaderStatus),
}

pub type PublisherStatus = DataWriterStatus;

#[derive(Debug, Clone)]
pub enum TopicStatus {
	InconsistentTopic { count: CountWithChange },
}

#[derive(Debug, Clone)]
pub enum DataReaderStatus {
	/// Sample was rejected, because resource limits would have been exeeded.
	SampleRejected { 
		count: CountWithChange,
		last_reason: SampleRejectedStatusKind,
		//last_instance_key:  
	},
	/// Remote Writer has become active or inactive.
	LivelinessChanged { 
		alive_total: CountWithChange,
		not_alive_total: CountWithChange,
		//last_publication_key:  
	},
	/// Deadline requested by this DataReader was missed.
	RequestedDeadlineMissed { 
		count: CountWithChange,
		//last_instance_key:  
	},
	/// This DataReader has requested a QoS policy that is incompatibel with what is offered.
	RequestedIncompatibleQos { 
		count: CountWithChange,
		last_policy_id: QosPolicyId,
		policies: Vec<QosPolicyCount>,
	},
	// DataAvailable is not implemented, as it seems to bring little additional value, 
	// because the normal data waiting mechanism already uses the same mio::poll structure,
	// so repeating the functionality here would bring little additional value.

	/// A sample has been lost (never received).
	/// (Whtever this means?)
	SampleLost  { 
		count: CountWithChange 
	},

	/// The DataReader has found a DataWriter that matches the Topic and has
	/// compatible QoS, or has ceased to be matched with a DataWriter that was
	/// previously considered to be matched.
	SubscriptionMatched { 
		total: CountWithChange,
		current: CountWithChange,
		//last_publication_key:  
	},
}

#[derive(Debug, Clone)]
pub enum DataWriterStatus {
	LivelinessLost { 
		count: CountWithChange 
	},
	OfferedDeadlineMissed { 
		count: CountWithChange,
		//last_instance_key:  
	},
	OfferedIncompatibleQos { 
		count: CountWithChange,
		last_policy_id: QosPolicyId,
		policies: Vec<QosPolicyCount>,  
	},
	PublicationMatched { 
		total: CountWithChange,
		current: CountWithChange,
		//last_subscription_key:  
	},
}

/// Helper to contain same count actions across statuses
#[derive(Debug, Copy, Clone, PartialEq)]
pub struct CountWithChange {
	// 2.3. Platform Specific Model defines these as "long", which appears to be 32-bit signed.
  count: i32,
  count_change: i32,
}

impl CountWithChange {
  pub(crate) fn new(count: i32, count_change: i32) -> CountWithChange {
    CountWithChange { count, count_change }
  }

  // ??
  // same as "new" ?
  pub fn start_from(count: i32, count_change: i32) -> CountWithChange {
    CountWithChange { count, count_change }
  }

  pub fn count(&self) -> i32 {
    self.count
  }

  pub fn count_change(&self) -> i32 {
    self.count_change
  }

  // does this make sense?
  // pub fn increase(&mut self) {
  //   self.count += 1;
  //   self.count_change += 1;
  // }

}

// sample rejection reasons
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum SampleRejectedStatusKind {
	NotRejected,
	ByInstancesLimit,
	BySamplesLimit,
	BySamplesPerInstanceLimit,
}

#[derive(Debug, Clone, Copy, PartialEq)]
pub struct QosPolicyCount {
	policy_id: QosPolicyId,
	count: i32,	
}