use crate::protocol::eval::ValueGroup;
use crate::runtime2::scheduler::*;
use crate::runtime2::runtime::*;
use crate::runtime2::communication::*;

use super::component_context::*;

pub struct PortAnnotation {
    self_comp_id: CompId,
    self_port_id: PortId,
    peer_comp_id: CompId, // only valid for getter ports
    peer_port_id: PortId, // only valid for getter ports
    peer_discovered: bool, // only valid for getter ports
    mapping: Option<u32>,
    kind: PortKind,
}

impl PortAnnotation {
    fn new(comp_id: CompId, port_id: PortId, kind: PortKind) -> Self {
        return Self{
            self_comp_id: comp_id,
            self_port_id: port_id,
            peer_comp_id: CompId::new_invalid(),
            peer_port_id: PortId::new_invalid(),
            peer_discovered: false,
            mapping: None,
            kind,
        }
    }
}

#[derive(Debug, Eq, PartialEq)]
enum Mode {
    NonSync,
    SyncBusy,
    SyncAwaitingSolution,
    SelectBusy,
    SelectWait,
}

struct SolutionCombiner {
    solution: SyncPartialSolution,
    matched_channels: usize,
}

impl SolutionCombiner {
    fn new() -> Self {
        return Self {
            solution: SyncPartialSolution::default(),
            matched_channels: 0,
        }
    }

    #[inline]
    fn has_contributions(&self) -> bool {
        return !self.solution.channel_mapping.is_empty();
    }

    /// Returns a decision for the current round. If there is no decision (yet)
    /// then `RoundDecision::None` is returned.
    fn get_decision(&self) -> SyncRoundDecision {
        if self.matched_channels == self.solution.channel_mapping.len() {
            debug_assert_ne!(self.solution.decision, SyncRoundDecision::None);
            return self.solution.decision;
        }

        return SyncRoundDecision::None; // even in case of failure: wait for everyone.
    }

    fn combine_with_partial_solution(&mut self, partial: SyncPartialSolution) {
        debug_assert_ne!(self.solution.decision, SyncRoundDecision::Solution);
        debug_assert_ne!(partial.decision, SyncRoundDecision::Solution);

        if partial.decision == SyncRoundDecision::Failure {
            self.solution.decision = SyncRoundDecision::Failure;
        }

        for entry in partial.channel_mapping {
            let channel_index = if entry.getter.is_some() && entry.putter.is_some() {
                let channel_index = self.solution.channel_mapping.len();
                self.solution.channel_mapping.push(entry);

                channel_index
            } else if let Some(putter) = entry.putter {
                self.combine_with_putter_port(putter)
            } else if let Some(getter) = entry.getter {
                self.combine_with_getter_port(getter)
            } else {
                unreachable!(); // both putter and getter are None
            };

            let channel = &self.solution.channel_mapping[channel_index];
            if let Some(consistent) = Self::channel_is_consistent(channel) {
                if !consistent {
                    self.solution.decision = SyncRoundDecision::Failure;
                }
                self.matched_channels += 1;
            }
        }

        self.update_solution();
    }

    /// Combines the currently stored global solution (if any) with the newly
    /// provided local solution. Make sure to check the `has_decision` return
    /// value afterwards.
    fn combine_with_local_solution(&mut self, _comp_id: CompId, solution: SyncLocalSolution) {
        debug_assert_ne!(self.solution.decision, SyncRoundDecision::Solution);

        // Combine partial solution with the local solution entries
        for entry in solution {
            // Match the current entry up with its peer endpoint, or add a new
            // entry.
            let channel_index = match entry {
                SyncLocalSolutionEntry::Putter(putter) => {
                    self.combine_with_putter_port(putter)
                },
                SyncLocalSolutionEntry::Getter(getter) => {
                    self.combine_with_getter_port(getter)
                }
            };

            // Check if channel is now consistent
            let channel = &self.solution.channel_mapping[channel_index];
            if let Some(consistent) = Self::channel_is_consistent(channel) {
                if !consistent {
                    self.solution.decision = SyncRoundDecision::Failure;
                }
                self.matched_channels += 1;
            }
        }

        self.update_solution();
    }

    /// Takes whatever partial solution is present in the solution combiner and
    /// returns it. The solution combiner's solution will end up being empty.
    /// This is used when a new leader is found and we need to pass along our
    /// partial results.
    fn take_partial_solution(&mut self) -> SyncPartialSolution {
        let mut partial_solution = SyncPartialSolution::default();
        std::mem::swap(&mut partial_solution, &mut self.solution);
        self.clear();

        return partial_solution;
    }

    fn clear(&mut self) {
        self.solution.channel_mapping.clear();
        self.solution.decision = SyncRoundDecision::None;
        self.matched_channels = 0;
    }

    // --- Small utilities for combining solutions

    fn combine_with_putter_port(&mut self, putter: SyncSolutionPutterPort) -> usize {
        let channel_index = self.get_channel_index_for_putter(putter.self_comp_id, putter.self_port_id);
        if let Some(channel_index) = channel_index {
            let channel = &mut self.solution.channel_mapping[channel_index];
            debug_assert!(channel.putter.is_none());
            channel.putter = Some(putter);

            return channel_index;
        } else {
            let channel_index = self.solution.channel_mapping.len();
            self.solution.channel_mapping.push(SyncSolutionChannel{
                putter: Some(putter),
                getter: None,
            });

            return channel_index;
        }
    }

    fn combine_with_getter_port(&mut self, getter: SyncSolutionGetterPort) -> usize {
        let channel_index = self.get_channel_index_for_getter(getter.peer_comp_id, getter.peer_port_id);
        if let Some(channel_index) = channel_index {
            let channel = &mut self.solution.channel_mapping[channel_index];
            debug_assert!(channel.getter.is_none());
            channel.getter = Some(getter);

            return channel_index;
        } else {
            let channel_index = self.solution.channel_mapping.len();
            self.solution.channel_mapping.push(SyncSolutionChannel{
                putter: None,
                getter: Some(getter)
            });

            return channel_index;
        }
    }

    /// Retrieve index of the channel containing a getter port that has received
    /// from the specified putter port.
    fn get_channel_index_for_putter(&self, putter_comp_id: CompId, putter_port_id: PortId) -> Option<usize> {
        for (channel_index, channel) in self.solution.channel_mapping.iter().enumerate() {
            if let Some(getter) = &channel.getter {
                if getter.peer_comp_id == putter_comp_id && getter.peer_port_id == putter_port_id {
                    return Some(channel_index);
                }
            }
        }

        return None;
    }

    /// Retrieve index of the channel for a getter port. To find this channel
    /// the **peer** component/port IDs of the getter port are used.
    fn get_channel_index_for_getter(&self, peer_comp_id: CompId, peer_port_id: PortId) -> Option<usize> {
        for (channel_index, channel) in self.solution.channel_mapping.iter().enumerate() {
            if let Some(putter) = &channel.putter {
                if putter.self_comp_id == peer_comp_id && putter.self_port_id == peer_port_id {
                    return Some(channel_index);
                }
            }
        }

        return None;
    }

    fn channel_is_consistent(channel: &SyncSolutionChannel) -> Option<bool> {
        if channel.putter.is_none() || channel.getter.is_none() {
            return None;
        }

        let putter = channel.putter.as_ref().unwrap();
        let getter = channel.getter.as_ref().unwrap();
        return Some(putter.mapping == getter.mapping);
    }

    /// Determines the global solution if all components have contributed their
    /// local solutions.
    fn update_solution(&mut self) {
        if self.matched_channels == self.solution.channel_mapping.len() {
            if self.solution.decision != SyncRoundDecision::Failure {
                self.solution.decision = SyncRoundDecision::Solution;
            }
        }
    }
}

/// Tracking consensus state
pub struct Consensus {
    // General state of consensus manager
    mapping_counter: u32,
    mode: Mode,
    // State associated with sync round
    round_index: u32,
    highest_id: CompId,
    ports: Vec<PortAnnotation>,
    // State associated with arriving at a solution and being a (temporary)
    // leader in the consensus round
    solution: SolutionCombiner,
}

impl Consensus {
    pub(crate) fn new() -> Self {
        return Self{
            round_index: 0,
            highest_id: CompId::new_invalid(),
            ports: Vec::new(),
            mapping_counter: 0,
            mode: Mode::NonSync,
            solution: SolutionCombiner::new(),
        }
    }

    // -------------------------------------------------------------------------
    // Managing sync state
    // -------------------------------------------------------------------------

    /// Notifies the consensus management that the PDL code has reached the
    /// start of a sync block.
    pub(crate) fn notify_sync_start(&mut self, comp_ctx: &CompCtx) {
        debug_assert_eq!(self.mode, Mode::NonSync);
        self.highest_id = comp_ctx.id;
        self.mapping_counter = 0;
        self.mode = Mode::SyncBusy;

        // Make the internally stored port annotation array consistent with the
        // ports that the component currently owns. They should match by index
        // (i.e. annotation at index `i` corresponds to port `i` in `comp_ctx`).
        let mut needs_setting_ports = false;
        if comp_ctx.num_ports() != self.ports.len() {
            needs_setting_ports = true;
        } else {
            for (idx, port) in comp_ctx.iter_ports().enumerate() {
                let comp_port_id = port.self_id;
                let cons_port_id = self.ports[idx].self_port_id;
                if comp_port_id != cons_port_id {
                    needs_setting_ports = true;
                    break;
                }
            }
        }

        if needs_setting_ports {
            // Reset all ports
            self.ports.clear();
            self.ports.reserve(comp_ctx.num_ports());
            for port in comp_ctx.iter_ports() {
                self.ports.push(PortAnnotation::new(comp_ctx.id, port.self_id, port.kind));
            }
        } else {
            // Make sure that we consider all peers as undiscovered again
            for annotation in self.ports.iter_mut() {
                annotation.peer_discovered = false;
            }
        }
    }

    /// Notifies the consensus management that the PDL code has reached the end
    /// of a sync block. A local solution will be submitted, after which we wait
    /// until the participants in the round (hopefully) reach a conclusion.
    pub(crate) fn notify_sync_end(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &CompCtx) -> SyncRoundDecision {
        debug_assert_eq!(self.mode, Mode::SyncBusy);
        self.mode = Mode::SyncAwaitingSolution;

        // Submit our port mapping as a solution
        let mut local_solution = Vec::with_capacity(self.ports.len());
        for port in &self.ports {
            if let Some(mapping) = port.mapping {
                let port_handle = comp_ctx.get_port_handle(port.self_port_id);
                let port_info = comp_ctx.get_port(port_handle);
                let new_entry = match port_info.kind {
                    PortKind::Putter => SyncLocalSolutionEntry::Putter(SyncSolutionPutterPort{
                        self_comp_id: comp_ctx.id,
                        self_port_id: port_info.self_id,
                        mapping
                    }),
                    PortKind::Getter => SyncLocalSolutionEntry::Getter(SyncSolutionGetterPort{
                        self_comp_id: comp_ctx.id,
                        self_port_id: port_info.self_id,
                        peer_comp_id: port.peer_comp_id,
                        peer_port_id: port.peer_port_id,
                        mapping
                    })
                };
                local_solution.push(new_entry);
            }
        }

        let decision = self.handle_local_solution(sched_ctx, comp_ctx, comp_ctx.id, local_solution);
        return decision;
    }

    /// Notifies that a decision has been reached. Note that the caller should
    /// still take the appropriate actions based on the decision it is supplying
    /// to the consensus layer.
    pub(crate) fn notify_sync_decision(&mut self, _decision: SyncRoundDecision) {
        // Reset everything for the next round
        debug_assert_eq!(self.mode, Mode::SyncAwaitingSolution);
        self.mode = Mode::NonSync;
        self.round_index = self.round_index.wrapping_add(1);

        for port in self.ports.iter_mut() {
            port.mapping = None;
        }

        self.solution.clear();
    }

    // -------------------------------------------------------------------------
    // Handling inbound and outbound messages
    // -------------------------------------------------------------------------

    /// Prepares a set of values to be sent of a channel.
    pub(crate) fn annotate_data_message(&mut self, comp_ctx: &CompCtx, port_info: &Port, content: ValueGroup) -> DataMessage {
        debug_assert_eq!(self.mode, Mode::SyncBusy); // can only send between sync start and sync end
        debug_assert!(self.ports.iter().any(|v| v.self_port_id == port_info.self_id));
        let data_header = self.create_data_header_and_update_mapping(port_info);
        let sync_header = self.create_sync_header(comp_ctx);

        return DataMessage{ data_header, sync_header, content };
    }

    /// Handles the arrival of a new data message (needs to be called for every
    /// new data message, even though it might not end up being received). This
    /// is used to determine peers of `get`ter ports.
    // TODO: The use of this function is rather ugly. Find a more robust
    //  scheme about owners of `get`ter ports not knowing about their peers.
    //  (also, figure out why this was written again, I forgot).
    pub(crate) fn handle_incoming_data_message(&mut self, comp_ctx: &CompCtx, message: &DataMessage) {
        let target_handle = comp_ctx.get_port_handle(message.data_header.target_port);
        let target_index = comp_ctx.get_port_index(target_handle);
        let annotation = &mut self.ports[target_index];
        debug_assert!(
            !annotation.peer_discovered || (
                annotation.peer_comp_id == message.sync_header.sending_id &&
                annotation.peer_port_id == message.data_header.source_port
            )
        );
        annotation.peer_comp_id = message.sync_header.sending_id;
        annotation.peer_port_id = message.data_header.source_port;
        annotation.peer_discovered = true;
    }

    /// Checks if the data message can be received (due to port annotations), if
    /// it can then `true` is returned and the caller is responsible for handing
    /// the message of to the PDL code. Otherwise the message cannot be
    /// received.
    pub(crate) fn try_receive_data_message(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, message: &DataMessage) -> bool {
        debug_assert_eq!(self.mode, Mode::SyncBusy);
        debug_assert!(self.ports.iter().any(|v| v.self_port_id == message.data_header.target_port));

        // Make sure the expected mapping matches the currently stored mapping
        for (peer_port_kind, expected_annotation) in &message.data_header.expected_mapping {
            // Determine our annotation, in order to do so we need to find the
            // port matching the peer ports
            let mut self_annotation = None;
            let mut self_annotation_found = false;
            match peer_port_kind {
                PortAnnotationKind::Putter(peer_port) => {
                    for self_port in &self.ports {
                        if self_port.kind == PortKind::Getter &&
                            self_port.peer_discovered &&
                            self_port.peer_comp_id == peer_port.self_comp_id &&
                            self_port.peer_port_id == peer_port.self_port_id
                        {
                            self_annotation = self_port.mapping;
                            self_annotation_found = true;
                            break;
                        }
                    }
                },
                PortAnnotationKind::Getter(peer_port) => {
                    if peer_port.peer_comp_id == comp_ctx.id {
                        // Peer indicates that we talked to it
                        let self_port_handle = comp_ctx.get_port_handle(peer_port.peer_port_id);
                        let self_port_index = comp_ctx.get_port_index(self_port_handle);
                        self_annotation = self.ports[self_port_index].mapping;
                        self_annotation_found = true;
                    }
                }
            }

            if !self_annotation_found {
                continue
            }

            if self_annotation != *expected_annotation {
                return false;
            }
        }

        // Expected mapping matches current mapping, so we will receive the message
        self.set_annotation(message.sync_header.sending_id, &message.data_header);

        // Handle the sync header embedded within the data message
        self.handle_sync_header(sched_ctx, comp_ctx, &message.sync_header);

        return true;
    }

    /// Receives the sync message and updates the consensus state appropriately.
    pub(crate) fn receive_sync_message(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, message: SyncMessage) -> SyncRoundDecision {
        // Whatever happens: handle the sync header (possibly changing the
        // currently registered leader)
        self.handle_sync_header(sched_ctx, comp_ctx, &message.sync_header);

        match message.content {
            SyncMessageContent::NotificationOfLeader => {
                return SyncRoundDecision::None;
            },
            SyncMessageContent::LocalSolution(solution_generator_id, local_solution) => {
                return self.handle_local_solution(sched_ctx, comp_ctx, solution_generator_id, local_solution);
            },
            SyncMessageContent::PartialSolution(partial_solution) => {
                return self.handle_partial_solution(sched_ctx, comp_ctx, partial_solution);
            },
            SyncMessageContent::GlobalSolution => {
                debug_assert_eq!(self.mode, Mode::SyncAwaitingSolution); // leader can only find global- if we submitted local solution
                return SyncRoundDecision::Solution;
            },
            SyncMessageContent::GlobalFailure => {
                debug_assert_eq!(self.mode, Mode::SyncAwaitingSolution);
                return SyncRoundDecision::Failure;
            }
        }
    }

    fn handle_sync_header(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, header: &MessageSyncHeader) {
        if header.highest_id.0 > self.highest_id.0 {
            // Sender knows of someone with a higher ID. So store highest ID,
            // notify all peers, and forward local solutions
            self.highest_id = header.highest_id;
            for peer in comp_ctx.iter_peers() {
                if peer.id == header.sending_id {
                    continue; // do not send to sender: it has the higher ID
                }

                // also: only send if we received a message in this round
                let mut performed_communication = false; // TODO: Revise, temporary fix
                for port in self.ports.iter() {
                    if port.peer_comp_id == peer.id && port.mapping.is_some() {
                        performed_communication = true;
                        break;
                    }
                }

                if !performed_communication {
                    continue;
                }

                let message = SyncMessage{
                    sync_header: self.create_sync_header(comp_ctx),
                    content: SyncMessageContent::NotificationOfLeader,
                };
                peer.handle.send_message(&sched_ctx.runtime, Message::Sync(message), true);
            }

            self.forward_partial_solution(sched_ctx, comp_ctx);
        } else if header.highest_id.0 < self.highest_id.0 {
            // Sender has a lower ID, so notify it of our higher one
            let message = SyncMessage{
                sync_header: self.create_sync_header(comp_ctx),
                content: SyncMessageContent::NotificationOfLeader,
            };
            let peer_handle = comp_ctx.get_peer_handle(header.sending_id);
            let peer_info = comp_ctx.get_peer(peer_handle);
            peer_info.handle.send_message(&sched_ctx.runtime, Message::Sync(message), true);
        } // else: exactly equal
    }

    fn set_annotation(&mut self, source_comp_id: CompId, data_header: &MessageDataHeader) {
        for annotation in self.ports.iter_mut() {
            if annotation.self_port_id == data_header.target_port {
                // Message should have already passed the `handle_new_data_message` function, so we
                // should have already annotated the peer of the port.
                debug_assert!(
                    annotation.peer_discovered &&
                    annotation.peer_comp_id == source_comp_id &&
                    annotation.peer_port_id == data_header.source_port
                );
                annotation.mapping = Some(data_header.new_mapping);
            }
        }
    }

    // -------------------------------------------------------------------------
    // Leader-related methods
    // -------------------------------------------------------------------------

    fn forward_partial_solution(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx) {
        debug_assert_ne!(self.highest_id, comp_ctx.id); // not leader

        // Make sure that we have something to send
        if !self.solution.has_contributions() {
            return;
        }

        // Swap the container with the partial solution and then send it along
        let partial_solution = self.solution.take_partial_solution();
        self.send_to_leader(sched_ctx, comp_ctx, Message::Sync(SyncMessage{
            sync_header: self.create_sync_header(comp_ctx),
            content: SyncMessageContent::PartialSolution(partial_solution),
        }));
    }

    fn handle_local_solution(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &CompCtx, solution_sender_id: CompId, solution: SyncLocalSolution) -> SyncRoundDecision {
        if self.highest_id == comp_ctx.id {
            // We are the leader
            self.solution.combine_with_local_solution(solution_sender_id, solution);
            let round_decision = self.solution.get_decision();
            if round_decision != SyncRoundDecision::None {
                self.broadcast_decision(sched_ctx, comp_ctx, round_decision);
            }
            return round_decision;
        } else {
            // Forward the solution
            let message = SyncMessage{
                sync_header: self.create_sync_header(comp_ctx),
                content: SyncMessageContent::LocalSolution(solution_sender_id, solution),
            };
            self.send_to_leader(sched_ctx, comp_ctx, Message::Sync(message));
            return SyncRoundDecision::None;
        }
    }

    fn handle_partial_solution(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, solution: SyncPartialSolution) -> SyncRoundDecision {
        if self.highest_id == comp_ctx.id {
            // We are the leader, combine existing and new solution
            self.solution.combine_with_partial_solution(solution);
            let round_decision = self.solution.get_decision();
            if round_decision != SyncRoundDecision::None {
                self.broadcast_decision(sched_ctx, comp_ctx, round_decision);
            }
            return round_decision;
        } else {
            // Forward the partial solution
            let message = SyncMessage{
                sync_header: self.create_sync_header(comp_ctx),
                content: SyncMessageContent::PartialSolution(solution),
            };
            self.send_to_leader(sched_ctx, comp_ctx, Message::Sync(message));
            return SyncRoundDecision::None;
        }
    }

    fn broadcast_decision(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &CompCtx, decision: SyncRoundDecision) {
        debug_assert_eq!(self.highest_id, comp_ctx.id);

        let is_success = match decision {
            SyncRoundDecision::None => unreachable!(),
            SyncRoundDecision::Solution => true,
            SyncRoundDecision::Failure => false,
        };

        let mut peers = Vec::with_capacity(self.solution.solution.channel_mapping.len()); // TODO: @Performance

        for channel in self.solution.solution.channel_mapping.iter() {
            let getter = channel.getter.as_ref().unwrap();
            if getter.self_comp_id != comp_ctx.id && !peers.contains(&getter.self_comp_id) {
                peers.push(getter.self_comp_id);
            }
            if getter.peer_comp_id != comp_ctx.id && !peers.contains(&getter.peer_comp_id) {
                peers.push(getter.peer_comp_id);
            }
        }

        for peer in peers {
            let mut handle = sched_ctx.runtime.get_component_public(peer);
            let message = Message::Sync(SyncMessage{
                sync_header: self.create_sync_header(comp_ctx),
                content: if is_success { SyncMessageContent::GlobalSolution } else { SyncMessageContent::GlobalFailure },
            });
            handle.send_message(&sched_ctx.runtime, message, true);
            let _should_remove = handle.decrement_users();
            debug_assert!(_should_remove.is_none());
        }
    }

    fn send_to_leader(&mut self, sched_ctx: &SchedulerCtx, comp_ctx: &CompCtx, message: Message) {
        debug_assert_ne!(self.highest_id, comp_ctx.id); // we're not the leader, // TODO: @NoDirectHandle
        let mut leader_info = sched_ctx.runtime.get_component_public(self.highest_id);
        leader_info.send_message(&sched_ctx.runtime, message, true);
        let should_remove = leader_info.decrement_users();
        if let Some(key) = should_remove {
            sched_ctx.runtime.destroy_component(key);
        }
    }

    // -------------------------------------------------------------------------
    // Creating message headers
    // -------------------------------------------------------------------------

    fn create_data_header_and_update_mapping(&mut self, port_info: &Port) -> MessageDataHeader {
        let mut expected_mapping = Vec::with_capacity(self.ports.len());
        let mut port_index = usize::MAX;
        for (index, port) in self.ports.iter().enumerate() {
            if port.self_port_id == port_info.self_id {
                port_index = index; // remember for later updating
            }

            // Add all of the
            let annotation_kind = match port.kind {
                PortKind::Putter => {
                    PortAnnotationKind::Putter(PortAnnotationPutter{
                        self_comp_id: port.self_comp_id,
                        self_port_id: port.self_port_id
                    })
                },
                PortKind::Getter => {
                    if !port.peer_discovered {
                        continue;
                    }

                    PortAnnotationKind::Getter(PortAnnotationGetter{
                        self_comp_id: port.self_comp_id,
                        self_port_id: port.self_port_id,
                        peer_comp_id: port.peer_comp_id,
                        peer_port_id: port.peer_port_id,
                    })
                }
            };
            expected_mapping.push((annotation_kind, port.mapping));
        }

        let new_mapping = self.take_mapping();
        self.ports[port_index].mapping = Some(new_mapping);
        debug_assert_eq!(port_info.kind, PortKind::Putter);
        return MessageDataHeader{
            expected_mapping,
            new_mapping,
            source_port: port_info.self_id,
            target_port: port_info.peer_port_id,
        };
    }

    #[inline]
    fn create_sync_header(&self, comp_ctx: &CompCtx) -> MessageSyncHeader {
        return MessageSyncHeader{
            sync_round: self.round_index,
            sending_id: comp_ctx.id,
            highest_id: self.highest_id,
        };
    }

    #[inline]
    fn take_mapping(&mut self) -> u32 {
        let mapping = self.mapping_counter;
        self.mapping_counter = self.mapping_counter.wrapping_add(1);
        return mapping;
    }
}