let port_was_used = last_instruction != PortInstruction::None;

                if exec_state.mode.is_in_sync_block() {

                    let closed_during_sync_round = content.closed_in_sync_round && port_was_used;

                    let closed_before_sync_round = !content.closed_in_sync_round && !port_has_had_message && port_was_used;

                    if closed_during_sync_round || closed_before_sync_round {

                        return Err((

                            last_instruction,

                            format!("Peer component (id:{}) shut down, so communication cannot (have) succeed(ed)", peer_comp_id.0)

                        ));

                    }

                } else {

                    let port_info = comp_ctx.get_port_mut(port_handle);

                    port_info.state.set(PortStateFlag::Closed);

                }

            }

        },

        ControlMessageContent::UnblockPort => {

            // We were previously blocked (or already closed)

            let port_to_unblock = message.target_port_id.unwrap();

            let port_handle = comp_ctx.get_port_handle(port_to_unblock);

            let port_info = comp_ctx.get_port_mut(port_handle);

            debug_assert_eq!(port_info.kind, PortKind::Putter);

            debug_assert!(port_info.state.is_set(PortStateFlag::BlockedDueToFullBuffers));

            port_info.state.clear(PortStateFlag::BlockedDueToFullBuffers);

            default_handle_recently_unblocked_port(

                exec_state, control, consensus, port_handle, sched_ctx,

                comp_ctx, inbox_main, inbox_backup

            )?;

        },

        ControlMessageContent::PortPeerChangedBlock => {

            // The peer of our port has just changed. So we are asked to

            // temporarily block the port (while our original recipient is

            // potentially rerouting some of the in-flight messages) and

            // Ack. Then we wait for the `unblock` call.

            let port_to_change = message.target_port_id.unwrap();

            let port_handle = comp_ctx.get_port_handle(port_to_change);

            let port_info = comp_ctx.get_port_mut(port_handle);

            let peer_comp_id = port_info.peer_comp_id;

            port_info.state.set(PortStateFlag::BlockedDueToPeerChange);

            let peer_handle = comp_ctx.get_peer_handle(peer_comp_id);

            default_send_ack(message.id, peer_handle, sched_ctx, comp_ctx);

        },

        ControlMessageContent::PortPeerChangedUnblock(new_port_id, new_comp_id) => {

            let port_to_change = message.target_port_id.unwrap();

            let port_handle = comp_ctx.get_port_handle(port_to_change);

            let port_info = comp_ctx.get_port(port_handle);

            debug_assert!(port_info.state.is_set(PortStateFlag::BlockedDueToPeerChange));

            let port_info = comp_ctx.get_port_mut(port_handle);

            port_info.peer_port_id = new_port_id;

            port_info.state.clear(PortStateFlag::BlockedDueToPeerChange);

            comp_ctx.change_port_peer(sched_ctx, port_handle, Some(new_comp_id));

            default_handle_recently_unblocked_port(

                exec_state, control, consensus, port_handle, sched_ctx,

                comp_ctx, inbox_main, inbox_backup

            )?;

        }

    }

    return Ok(());

}

/// Handles a component entering the synchronous block. Will ensure that the

/// `Consensus` and the `ComponentCtx` are initialized properly.

pub(crate) fn default_handle_sync_start(

    exec_state: &mut CompExecState, inbox_main: &mut InboxMainRef,

    sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, consensus: &mut Consensus

) {

    sched_ctx.info("Component starting sync mode");

    // If any messages are present for this sync round, set the appropriate flag

    // and notify the consensus handler of the present messages

    consensus.notify_sync_start(comp_ctx);

    for (port_index, message) in inbox_main.iter().enumerate() {

        if let Some(message) = message {

            consensus.handle_incoming_data_message(comp_ctx, message);

            let port_info = comp_ctx.get_port_by_index_mut(port_index);

            port_info.received_message_for_sync = true;

        }

    }

    // Modify execution state

    debug_assert_eq!(exec_state.mode, CompMode::NonSync);

    exec_state.mode = CompMode::Sync;

}

/// Handles a component that has reached the end of the sync block. This does

/// not necessarily mean that the component will go into the `NonSync` mode, as

/// it might have to wait for the leader to finish the round for everyone (see

/// `default_handle_sync_decision`)

pub(crate) fn default_handle_sync_end(

    exec_state: &mut CompExecState, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx,

    consensus: &mut Consensus

) {

    sched_ctx.info("Component ending sync mode (but possibly waiting for a solution)");

    debug_assert_eq!(exec_state.mode, CompMode::Sync);

    let decision = consensus.notify_sync_end_success(sched_ctx, comp_ctx);

    exec_state.mode = CompMode::SyncEnd;

    default_handle_sync_decision(sched_ctx, exec_state, comp_ctx, decision, consensus);

}

/// Handles a component initiating the exiting procedure, and closing all of its

/// ports. Should only be called once per component (which is ensured by

/// checking and modifying the mode in the execution state).

#[must_use]

pub(crate) fn default_handle_start_exit(

    exec_state: &mut CompExecState, control: &mut ControlLayer,

    sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, consensus: &mut Consensus

) -> CompScheduling {

    debug_assert_eq!(exec_state.mode, CompMode::StartExit);

    for port_index in 0..comp_ctx.num_ports() {

        let port_info = comp_ctx.get_port_by_index_mut(port_index);

        if port_info.state.is_blocked() {

            return CompScheduling::Sleep;

        }

    }

    sched_ctx.info(&format!("Component starting exit (reason: {:?})", exec_state.exit_reason));

    exec_state.mode = CompMode::BusyExit;

    let exit_inside_sync = exec_state.exit_reason.is_in_sync();

    // If exiting while inside sync mode, report to the leader of the current

    // round that we've failed.

    if exit_inside_sync {

        let decision = consensus.notify_sync_end_failure(sched_ctx, comp_ctx);

        default_handle_sync_decision(sched_ctx, exec_state, comp_ctx, decision, consensus);

    }

    // Iterating over ports by index to work around borrowing rules

    for port_index in 0..comp_ctx.num_ports() {

        let port = comp_ctx.get_port_by_index_mut(port_index);

        if port.state.is_closed() || port.state.is_set(PortStateFlag::Transmitted) || port.close_at_sync_end {

            // Already closed, or in the process of being closed

            continue;

        }

        // Mark as closed

        let port_id = port.self_id;

        port.state.set(PortStateFlag::Closed);

        // Notify peer of closing

        let port_handle = comp_ctx.get_port_handle(port_id);

        let (peer, message) = control.initiate_port_closing(port_handle, exit_inside_sync, comp_ctx);

        let peer_info = comp_ctx.get_peer(peer);

        peer_info.handle.send_message_logged(sched_ctx, Message::Control(message), true);

    }

    return CompScheduling::Immediate; // to check if we can shut down immediately

}

/// Handles a component waiting until all peers are notified that it is quitting

/// (i.e. after calling `default_handle_start_exit`).

#[must_use]

pub(crate) fn default_handle_busy_exit(

    exec_state: &mut CompExecState, control: &ControlLayer,

    sched_ctx: &SchedulerCtx

) -> CompScheduling {

    debug_assert_eq!(exec_state.mode, CompMode::BusyExit);

    if control.has_acks_remaining() {

        sched_ctx.info("Component busy exiting, still has `Ack`s remaining");

        return CompScheduling::Sleep;

    } else {

        sched_ctx.info("Component busy exiting, now shutting down");

        exec_state.mode = CompMode::Exit;

        return CompScheduling::Exit;

    }

}

/// Handles a potential synchronous round decision. If there was a decision then

/// the `Some(success)` value indicates whether the round succeeded or not.

/// Might also end up changing the `ExecState`.

///

/// Might be called in two cases:

/// 1. The component is in regular execution mode, at the end of a sync round,

///     and is waiting for a solution to the round.

/// 2. The component has encountered an error during a sync round and is

///     exiting, hence is waiting for a "Failure" message from the leader.

pub(crate) fn default_handle_sync_decision(

    sched_ctx: &SchedulerCtx, exec_state: &mut CompExecState, comp_ctx: &mut CompCtx,

    decision: SyncRoundDecision, consensus: &mut Consensus

) -> Option<bool> {

    let success = match decision {

        SyncRoundDecision::None => return None,

        SyncRoundDecision::Solution => true,

        SyncRoundDecision::Failure => false,

    };

    debug_assert!(

        exec_state.mode == CompMode::SyncEnd || (

            exec_state.mode.is_busy_exiting() && exec_state.exit_reason.is_error()

        ) || (

            exec_state.mode.is_in_sync_block() && decision == SyncRoundDecision::Failure

        )

    );

    sched_ctx.info(&format!("Handling decision {:?} (in mode: {:?})", decision, exec_state.mode));

    consensus.notify_sync_decision(decision);

    if success {

        // We cannot get a success message if the component has encountered an

        // error.

        for port_index in 0..comp_ctx.num_ports() {

            let port_info = comp_ctx.get_port_by_index_mut(port_index);

            if port_info.close_at_sync_end {

                port_info.state.set(PortStateFlag::Closed);

            }

            port_info.state.clear(PortStateFlag::Received);

        }

        debug_assert_eq!(exec_state.mode, CompMode::SyncEnd);

        exec_state.mode = CompMode::NonSync;

        return Some(true);

    } else {

        // We may get failure both in all possible cases. But we should only

        // modify the execution state if we're not already in exit mode

        if !exec_state.mode.is_busy_exiting() {

            sched_ctx.error("failed synchronous round, initiating exit");

            exec_state.set_as_start_exit(ExitReason::ErrorNonSync);

        }

        return Some(false);

    }

}

pub(crate) fn default_start_create_component(

    exec_state: &mut CompExecState, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx,

    control: &mut ControlLayer, inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup,

    definition_id: ProcedureDefinitionId, type_id: TypeId, arguments: ValueGroup

) {

    debug_assert_eq!(exec_state.mode, CompMode::NonSync);

    let mut transferred_ports = Vec::new();

    find_ports_in_value_group(&arguments, &mut transferred_ports);

    // Set execution state as waiting until we can create the component. If we

    // can do so right away, then we will.

    exec_state.set_as_create_component_blocked(definition_id, type_id, arguments);

    if ports_not_blocked(comp_ctx, &transferred_ports) {

        perform_create_component(exec_state, sched_ctx, comp_ctx, control, inbox_main, inbox_backup);

    }

}

/// Actually creates a component (and assumes that the caller made sure that

/// none of the ports are involved in a blocking operation).

pub(crate) fn perform_create_component(

    exec_state: &mut CompExecState, sched_ctx: &SchedulerCtx, instantiator_ctx: &mut CompCtx,

    control: &mut ControlLayer, inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup

) {

    // Small internal utilities

    struct PortPair {

        instantiator_id: PortId,

        instantiator_handle: LocalPortHandle,

        created_id: PortId,

        created_handle: LocalPortHandle,

        is_open: bool,

    }

    // Retrieve ports from the arguments

    debug_assert_eq!(exec_state.mode, CompMode::NewComponentBlocked);

    let (procedure_id, procedure_type_id) = exec_state.mode_component;

    let mut arguments = exec_state.mode_value.take();

    let mut ports = Vec::new();

    find_ports_in_value_group(&arguments, &mut ports);

    debug_assert!(ports_not_blocked(instantiator_ctx, &ports));

    // Reserve a location for the new component

    let reservation = sched_ctx.runtime.start_create_component();

    let mut created_ctx = CompCtx::new(&reservation);

    let mut port_pairs = Vec::with_capacity(ports.len());

    // Go over all the ports that will be transferred. Since the ports will get

    // a new ID in the new component, we will take care of that here.

    for (port_location, instantiator_port_id) in &ports {

        // Retrieve port information from instantiator

        let instantiator_port_id = *instantiator_port_id;

        let instantiator_port_handle = instantiator_ctx.get_port_handle(instantiator_port_id);

        let instantiator_port = instantiator_ctx.get_port(instantiator_port_handle);

        // Create port at created component

        let created_port_handle = created_ctx.add_port(

            instantiator_port.peer_comp_id, instantiator_port.peer_port_id,

            instantiator_port.kind, instantiator_port.state

        );

        let created_port = created_ctx.get_port(created_port_handle);

        let created_port_id = created_port.self_id;

        // Modify port ID in the arguments to the new component and store them

        // for later access

        let is_open = instantiator_port.state.is_open();

        port_pairs.push(PortPair{

            instantiator_id: instantiator_port_id,

            instantiator_handle: instantiator_port_handle,

            created_id: created_port_id,

            created_handle: created_port_handle,

            is_open,

        });

        for location in port_location.iter().copied() {

            let value = arguments.get_value_mut(location);

            match value {

                Value::Input(id) => *id = port_id_to_eval(created_port_id),

                Value::Output(id) => *id = port_id_to_eval(created_port_id),

                _ => unreachable!(),

            }

        }

    }

    // For each of the ports in the newly created component we set the peer to

    // the correct value. We will not yet change the peer on the instantiator's

    // ports (as we haven't yet stored the new component in the runtime's

    // component storage)

    let mut created_component_has_remote_peers = false;

    for pair in port_pairs.iter() {

        let instantiator_port_info = instantiator_ctx.get_port(pair.instantiator_handle);

        let created_port_info = created_ctx.get_port_mut(pair.created_handle);

        if created_port_info.peer_comp_id == instantiator_ctx.id {

            // The peer of the created component's port seems to be the

            // instantiator.

            let created_port_peer_index = port_pairs.iter()

                .position(|v| v.instantiator_id == instantiator_port_info.peer_port_id);

            match created_port_peer_index {

                Some(created_port_peer_index) => {

                    // However, the peer port is also moved to the new

                    // component, so the complete channel is owned by the new

                    // component.

                    let peer_pair = &port_pairs[created_port_peer_index];

                    created_port_info.peer_port_id = peer_pair.created_id;

                    created_port_info.peer_comp_id = reservation.id();

                },

                None => {

                    // Peer port remains with instantiator. However, we cannot

                    // set the peer on the instantiator yet, because the new

                    // component has not yet been stored in the runtime's

                    // component storage. So we do this later

                    created_port_info.peer_comp_id = instantiator_ctx.id;

                    if pair.is_open {

                        created_ctx.change_port_peer(sched_ctx, pair.created_handle, Some(instantiator_ctx.id));

                    }

                }

            }

        } else {

            // Peer is a different component

            if pair.is_open {

                // And the port is still open, so we need to notify the peer

                let peer_handle = instantiator_ctx.get_peer_handle(created_port_info.peer_comp_id);

                let peer_info = instantiator_ctx.get_peer(peer_handle);

                created_ctx.change_port_peer(sched_ctx, pair.created_handle, Some(peer_info.id));

                created_component_has_remote_peers = true;

            }

        }

    }

    // Now we store the new component into the runtime's component storage using

    // the reservation.

    let component = create_component(

        &sched_ctx.runtime.protocol, procedure_id, procedure_type_id,

        arguments, port_pairs.len()

    );

    let (created_key, created_runtime_component) = sched_ctx.runtime.finish_create_component(

        reservation, component, created_ctx, false

    );

    let created_ctx = &mut created_runtime_component.ctx;

    let created_component = &mut created_runtime_component.component;

    created_component.on_creation(created_key.downgrade(), sched_ctx);

    // We now pass along the messages that the instantiator component still has

    // that belong to the new component. At the same time we'll take care of

    // setting the correct peer of the instantiator component

    for pair in port_pairs.iter() {

        // Transferring the messages and removing the port from the

        // instantiator component

        let instantiator_port_index = instantiator_ctx.get_port_index(pair.instantiator_handle);

        instantiator_ctx.change_port_peer(sched_ctx, pair.instantiator_handle, None);

        instantiator_ctx.remove_port(pair.instantiator_handle);

            message.data_header.target_port = pair.created_id;

            created_component.adopt_message(created_ctx, message);

        }

        let mut message_index = 0;

        while message_index < inbox_backup.len() {

            let message = &inbox_backup[message_index];

            if message.data_header.target_port == pair.instantiator_id {

                // Transfer the message

                let mut message = inbox_backup.remove(message_index);

                message.data_header.target_port = pair.created_id;

                created_component.adopt_message(created_ctx, message);

            } else {

                // Message does not belong to the port pair that we're

                // transferring to the new component.

                message_index += 1;

            }

        }

        // Here we take care of the case where the instantiator previously owned

        // both ends of the channel, but has transferred one port to the new

        // component (hence creating a channel between the instantiator

        // component and the new component).

        let created_port_info = created_ctx.get_port(pair.created_handle);

        if pair.is_open && created_port_info.peer_comp_id == instantiator_ctx.id {

            // Note: the port we're receiving here belongs to the instantiator

            // and is NOT in the "port_pairs" array.

            let instantiator_port_handle = instantiator_ctx.get_port_handle(created_port_info.peer_port_id);

            let instantiator_port_info = instantiator_ctx.get_port_mut(instantiator_port_handle);

            instantiator_port_info.peer_port_id = created_port_info.self_id;

            instantiator_ctx.change_port_peer(sched_ctx, instantiator_port_handle, Some(created_ctx.id));

        }

    }

    // Finally: if we did move ports around whose peers are different

    // components, then we'll initiate the appropriate protocol to notify them.

    if created_component_has_remote_peers {

        let schedule_entry_id = control.add_schedule_entry(created_ctx.id);

        for pair in &port_pairs {

            let port_info = created_ctx.get_port(pair.created_handle);

            if pair.is_open && port_info.peer_comp_id != instantiator_ctx.id && port_info.peer_comp_id != created_ctx.id {

                // Peer component is not the instantiator, and it is not the

                // new component itself

                let message = control.add_reroute_entry(

                    instantiator_ctx.id, port_info.peer_port_id, port_info.peer_comp_id,

                    pair.instantiator_id, pair.created_id, created_ctx.id,

                    schedule_entry_id

                );

                let peer_handle = created_ctx.get_peer_handle(port_info.peer_comp_id);

                let peer_info = created_ctx.get_peer(peer_handle);

                peer_info.handle.send_message_logged(sched_ctx, message, true);

            }

        }

    } else {

        // We can schedule the component immediately, we do not have to wait

        // for any peers: there are none.

        sched_ctx.runtime.enqueue_work(created_key);

    }

    exec_state.mode = CompMode::NonSync;

    exec_state.mode_component = (ProcedureDefinitionId::new_invalid(), TypeId::new_invalid());

}

pub(crate) fn ports_not_blocked(comp_ctx: &CompCtx, ports: &EncounteredPorts) -> bool {

    for (_port_locations, port_id) in ports {

        let port_handle = comp_ctx.get_port_handle(*port_id);

        let port_info = comp_ctx.get_port(port_handle);

        if port_info.state.is_blocked_due_to_port_change() {

            return false;

        }

    }

    return true;

}

/// Performs the default action of printing the provided error, and then putting

/// the component in the state where it will shut down. Only to be used for

/// builtin components: their error message construction is simpler (and more

/// common) as they don't have any source code.

pub(crate) fn default_handle_error_for_builtin(

    exec_state: &mut CompExecState, sched_ctx: &SchedulerCtx,

    location_and_message: (PortInstruction, String)

) {

    let (_location, message) = location_and_message;

    sched_ctx.error(&message);

    let exit_reason = if exec_state.mode.is_in_sync_block() {

        ExitReason::ErrorInSync

    } else {

        ExitReason::ErrorNonSync

    };

    exec_state.set_as_start_exit(exit_reason);

}

#[inline]

pub(crate) fn default_handle_exit(_exec_state: &CompExecState) -> CompScheduling {

    debug_assert_eq!(_exec_state.mode, CompMode::Exit);

    return CompScheduling::Exit;

}

// -----------------------------------------------------------------------------

// Internal messaging/state utilities

// -----------------------------------------------------------------------------

/// Sends a message without any transmitted ports. Does not check if sending

/// is actually valid.

fn send_message_without_ports(

    sending_port_handle: LocalPortHandle, value: ValueGroup,

    comp_ctx: &CompCtx, sched_ctx: &SchedulerCtx, consensus: &mut Consensus,

) {

    let port_info = comp_ctx.get_port(sending_port_handle);

    debug_assert!(port_info.state.can_send());

    let peer_handle = comp_ctx.get_peer_handle(port_info.peer_comp_id);

    let peer_info = comp_ctx.get_peer(peer_handle);

    let annotated_message = consensus.annotate_data_message(comp_ctx, port_info, value);

    peer_info.handle.send_message_logged(sched_ctx, Message::Data(annotated_message), true);

}

/// Prepares sending a message that contains ports. Only once a particular

/// protocol has completed (where we notify all the peers that the ports will

/// be transferred) will we actually send the message to the recipient.

fn start_send_message_with_ports(

    sending_port_id: PortId, sending_port_instruction: PortInstruction, value: ValueGroup,

    exec_state: &mut CompExecState, comp_ctx: &mut CompCtx, sched_ctx: &SchedulerCtx,

    control: &mut ControlLayer

) -> Result<(), (PortInstruction, String)> {

    debug_assert_eq!(exec_state.mode, CompMode::Sync); // busy in sync, trying to send

    // Retrieve ports we're going to transfer

    let sending_port_handle = comp_ctx.get_port_handle(sending_port_id);

    let sending_port_info = comp_ctx.get_port_mut(sending_port_handle);

    sending_port_info.last_instruction = sending_port_instruction;

    let mut transmit_ports = Vec::new();

    find_ports_in_value_group(&value, &mut transmit_ports);

    debug_assert!(!transmit_ports.is_empty()); // required from caller

    // Enter the state where we'll wait until all transferred ports are not

    // blocked.

    exec_state.set_as_blocked_put_with_ports(sending_port_id, value);

    if ports_not_blocked(comp_ctx, &transmit_ports) {

        // Ports are not blocked, so we can send them right away.

        perform_send_message_with_ports_notify_peers(

            exec_state, comp_ctx, sched_ctx, control, transmit_ports

        )?;

    } // else: wait until they become unblocked

    return Ok(())

}

fn perform_send_message_with_ports_notify_peers(

    exec_state: &mut CompExecState, comp_ctx: &mut CompCtx, sched_ctx: &SchedulerCtx,

    control: &mut ControlLayer, transmit_ports: EncounteredPorts

) -> Result<(), (PortInstruction, String)> {

    // Check we're in the correct state in debug mode

    debug_assert_eq!(exec_state.mode, CompMode::PutPortsBlockedTransferredPorts);

    debug_assert!(ports_not_blocked(comp_ctx, &transmit_ports));

    // Set up the final Ack that triggers us to send our final message

    let unblock_put_control_id = control.add_unblock_put_with_ports_entry();

    for (_, port_id) in &transmit_ports {

        let transmit_port_handle = comp_ctx.get_port_handle(*port_id);

        let transmit_port_info = comp_ctx.get_port_mut(transmit_port_handle);

        let peer_comp_id = transmit_port_info.peer_comp_id;

        let peer_port_id = transmit_port_info.peer_port_id;

        // Note: we checked earlier that we are currently in sync mode. Now we

        // will check if we've already used the port we're about to transmit.

        if !transmit_port_info.last_instruction.is_none() {

            let sending_port_handle = comp_ctx.get_port_handle(exec_state.mode_port);

            let sending_port_instruction = comp_ctx.get_port(sending_port_handle).last_instruction;

            return Err((

                sending_port_instruction,

                String::from("Cannot transmit one of the ports in this message, as it is used in this sync round")

            ));

        }

        if transmit_port_info.state.is_set(PortStateFlag::Transmitted) {

            let sending_port_handle = comp_ctx.get_port_handle(exec_state.mode_port);

            let sending_port_instruction = comp_ctx.get_port(sending_port_handle).last_instruction;

            return Err((

                sending_port_instruction,

                String::from("Cannot transmit one of the ports in this message, as that port is already transmitted")

            ));

        }

        // Set the flag for transmission

        transmit_port_info.state.set(PortStateFlag::Transmitted);

        // Block the peer of the port

        let message = control.create_port_transfer_message(unblock_put_control_id, comp_ctx.id, peer_port_id);

        println!("DEBUG: Port transfer message\nControl ID: {:?}\nMessage: {:?}", unblock_put_control_id, message);

        let peer_handle = comp_ctx.get_peer_handle(peer_comp_id);

        let peer_info = comp_ctx.get_peer(peer_handle);

        peer_info.handle.send_message_logged(sched_ctx, message, true);

    }

    // We've set up the protocol, once all the PPC's are blocked we are supposed

    // to transfer the message to the recipient. So store it temporarily

    exec_state.mode = CompMode::PutPortsBlockedAwaitingAcks;

    return Ok(());

}

/// Performs the transmission of a data message that contains ports. These were

/// all stored in the component's execution state by the

/// `prepare_send_message_with_ports` function. Port must be ready to send!

fn perform_send_message_with_ports_to_receiver(

    exec_state: &mut CompExecState, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, consensus: &mut Consensus,

    inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup

) -> Result<(), (PortInstruction, String)> {

    debug_assert_eq!(exec_state.mode, CompMode::PutPortsBlockedSendingPort);

    // Find all ports again

    let mut transmit_ports = Vec::new();

    find_ports_in_value_group(&exec_state.mode_value, &mut transmit_ports);

    // Retrieve the port over which we're going to send the message

    let port_handle = comp_ctx.get_port_handle(exec_state.mode_port);

    let port_info = comp_ctx.get_port(port_handle);

    if !port_info.state.is_open() {

        return Err((

            port_info.last_instruction,

            String::from("cannot send over this port, as it is closed")

        ));

    }

    debug_assert!(!port_info.state.is_blocked_due_to_port_change()); // caller should have checked this

    let peer_handle = comp_ctx.get_peer_handle(port_info.peer_comp_id);

    // Change state back to its default

    exec_state.mode = CompMode::Sync;

    let message_value = exec_state.mode_value.take();

    exec_state.mode_port = PortId::new_invalid();

    // Annotate the data message

    let mut annotated_message = consensus.annotate_data_message(comp_ctx, port_info, message_value);

    // And further enhance the message by adding data about the ports that are

    // being transferred

    for (port_locations, transmit_port_id) in transmit_ports {

        let transmit_port_handle = comp_ctx.get_port_handle(transmit_port_id);

        let transmit_port_info = comp_ctx.get_port(transmit_port_handle);

        let transmit_messages = take_port_messages(comp_ctx, transmit_port_id, inbox_main, inbox_backup);

        let mut transmit_port_state = transmit_port_info.state;

        debug_assert!(transmit_port_state.is_set(PortStateFlag::Transmitted));

        transmit_port_state.clear(PortStateFlag::Transmitted);

        annotated_message.ports.push(TransmittedPort{

            locations: port_locations,

            messages: transmit_messages,

            peer_comp: transmit_port_info.peer_comp_id,

            peer_port: transmit_port_info.peer_port_id,

            kind: transmit_port_info.kind,

            state: transmit_port_state

        });

        comp_ctx.change_port_peer(sched_ctx, transmit_port_handle, None);

    }

    // And finally, send the message to the peer

    let peer_info = comp_ctx.get_peer(peer_handle);

    peer_info.handle.send_message_logged(sched_ctx, Message::Data(annotated_message), true);

    return Ok(());

}

/// Handles an `Ack` for the control layer.

fn default_handle_ack(

    exec_state: &mut CompExecState, control: &mut ControlLayer, control_id: ControlId,

    sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx, consensus: &mut Consensus,

    inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup

) -> Result<(), (PortInstruction, String)>{

    // Since an `Ack` may cause another one, handle them in a loop

    let mut to_ack = control_id;

    loop {

        let (action, new_to_ack) = control.handle_ack(to_ack, sched_ctx, comp_ctx);

        match action {

            AckAction::SendMessage(target_comp, message) => {

                // FIX @NoDirectHandle

                let mut handle = sched_ctx.runtime.get_component_public(target_comp);

                handle.send_message_logged(sched_ctx, Message::Control(message), true);

                let _should_remove = handle.decrement_users();

                debug_assert!(_should_remove.is_none());

            },

            AckAction::ScheduleComponent(to_schedule) => {

                // FIX @NoDirectHandle

                let mut handle = sched_ctx.runtime.get_component_public(to_schedule);

                // Note that the component is intentionally not

                // sleeping, so we just wake it up

                debug_assert!(!handle.sleeping.load(std::sync::atomic::Ordering::Acquire));

                let key = unsafe { to_schedule.upgrade() };

                sched_ctx.runtime.enqueue_work(key);

                let _should_remove = handle.decrement_users();

                debug_assert!(_should_remove.is_none());

            },

            AckAction::UnblockPutWithPorts => {

                // Send the message (containing ports) stored in the component

                // execution state to the recipient

                println!("DEBUG: Unblocking put with ports");

                debug_assert_eq!(exec_state.mode, CompMode::PutPortsBlockedAwaitingAcks);

                exec_state.mode = CompMode::PutPortsBlockedSendingPort;

                let port_handle = comp_ctx.get_port_handle(exec_state.mode_port);

                // Little bit of a hack, we didn't really unblock the sending

                // port, but this will mesh nicely with waiting for the sending

                // port to become unblocked.

                default_handle_recently_unblocked_port(

                    exec_state, control, consensus, port_handle, sched_ctx,

                    comp_ctx, inbox_main, inbox_backup

                )?;

            },

            AckAction::None => {}

        }

        match new_to_ack {

            Some(new_to_ack) => to_ack = new_to_ack,

            None => break,

        }

    }

    return Ok(());

}

/// Little helper for sending the most common kind of `Ack`

fn default_send_ack(

    causer_of_ack_id: ControlId, peer_handle: LocalPeerHandle,

    sched_ctx: &SchedulerCtx, comp_ctx: &CompCtx

) {

    let peer_info = comp_ctx.get_peer(peer_handle);

    peer_info.handle.send_message_logged(sched_ctx, Message::Control(ControlMessage{

        id: causer_of_ack_id,

        sender_comp_id: comp_ctx.id,

        target_port_id: None,

        content: ControlMessageContent::Ack

    }), true);

}

/// Handles the unblocking of a putter port. In case there is a pending message

/// on that port then it will be sent. There are two reasons for calling this

/// function: either a port was blocked (i.e. the Blocked state flag was

/// cleared), or the component is ready to send a message containing ports

/// (stored in the execution state). In this latter case we might still have

/// a blocked port.

fn default_handle_recently_unblocked_port(

    exec_state: &mut CompExecState, control: &mut ControlLayer, consensus: &mut Consensus,

    port_handle: LocalPortHandle, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx,

    inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup

) -> Result<(), (PortInstruction, String)> {

    let port_info = comp_ctx.get_port_mut(port_handle);

    let port_id = port_info.self_id;

    if port_info.state.is_blocked() {

        // Port is still blocked. We wait until the next control message where

        // we unblock the port.

        return Ok(());

    }

    if exec_state.is_blocked_on_put_without_ports(port_id) {

        // Annotate the message that we're going to send

        let port_info = comp_ctx.get_port(port_handle); // for immutable access

        debug_assert_eq!(port_info.kind, PortKind::Putter);

        let to_send = exec_state.mode_value.take();

        let to_send = consensus.annotate_data_message(comp_ctx, port_info, to_send);

        // Retrieve peer to send the message

        let peer_handle = comp_ctx.get_peer_handle(port_info.peer_comp_id);

        let peer_info = comp_ctx.get_peer(peer_handle);

        peer_info.handle.send_message_logged(sched_ctx, Message::Data(to_send), true);

        // Return to the regular execution mode

        exec_state.mode = CompMode::Sync;

use super::*;

// silly test to make sure that the PDL will never be an issue when doing TCP

// stuff with the actual components

#[test]

fn test_stdlib_file() {

    compile_and_create_component("

    import std.internet as inet;

    comp fake_listener_once(out<inet::TcpConnection> tx) {

        channel cmd_tx -> cmd_rx;

        channel data_tx -> data_rx;

        new fake_socket(cmd_rx, data_tx);

        sync put(tx, inet::TcpConnection{

            tx: cmd_tx,

            rx: data_rx,

        });

    }

    comp fake_socket(in<inet::Cmd> cmds, out<u8[]> tx) {

        auto to_send = {};

        auto shutdown = false;

        while (!shutdown) {

            auto keep_going = true;

            sync {

                while (keep_going) {

                    auto cmd = get(cmds);

                    if (let inet::Cmd::Send(data) = cmd) {

                        to_send = data;

                    } else if (let inet::Cmd::Receive = cmd) {

                        put(tx, to_send);

                    } else if (let inet::Cmd::Finish = cmd) {

                        keep_going = false;

                    } else if (let inet::Cmd::Shutdown = cmd) {

                        keep_going = false;

                        shutdown = true;

                    }

                }

            }

        }

    }

    comp fake_client(inet::TcpConnection conn) {

        sync put(conn.tx, inet::Cmd::Send({1, 3, 3, 7}));

        sync {

            put(conn.tx, inet::Cmd::Receive);

            auto val = get(conn.rx);

            put(conn.tx, inet::Cmd::Finish);

        }

        sync put(conn.tx, inet::Cmd::Shutdown);

    }

    comp constructor() {

        channel conn_tx -> conn_rx;

        new fake_listener_once(conn_tx);

        // Same crap as before:

        channel cmd_tx -> unused_cmd_rx;

        channel unused_data_tx -> data_rx;

        auto connection = inet::TcpConnection{ tx: cmd_tx, rx: data_rx };

        sync {

            connection = get(conn_rx);

        }

        new fake_client(connection);

    }

    ", "constructor", no_args());

}