};

    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")

            ));

        }

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());

}