use std::fmt::{Display as FmtDisplay, Result as FmtResult, Formatter};

use crate::protocol::eval::{Prompt, EvalError, ValueGroup, Value, ValueId, PortId as EvalPortId};

use crate::protocol::*;

use crate::runtime2::*;

use crate::runtime2::communication::*;

use super::{CompCtx, CompPDL, CompId};

use super::component_context::*;

use super::component_random::*;

use super::component_internet::*;

use super::control_layer::*;

use super::consensus::*;

pub enum CompScheduling {

    Immediate,

    Requeue,

    Sleep,

    Exit,

}

/// Potential error emitted by a component

pub enum CompError {

    /// Error originating from the code executor. Hence has an associated

    /// source location.

    Executor(EvalError),

    /// Error originating from a component, but not necessarily associated with

    /// a location in the source.

    Component(String), // TODO: Maybe a different embedded value in the future?

    /// Pure runtime error. Not necessarily originating from the component

    /// itself. Should be treated as a very severe runtime-compromising error.

    Runtime(RtError),

}

impl FmtDisplay for CompError {

    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {

        match self {

            CompError::Executor(v) => v.fmt(f),

            CompError::Component(v) => v.fmt(f),

            CompError::Runtime(v) => v.fmt(f),

        }

    }

}

/// Generic representation of a component (as viewed by a scheduler).

pub(crate) trait Component {

    /// Called upon the creation of the component. Note that the scheduler

    /// context is officially running another component (the component that is

    /// creating the new component).

    fn on_creation(&mut self, comp_id: CompId, sched_ctx: &SchedulerCtx);

    /// Called when a component crashes or wishes to exit. So is not called

    /// right before destruction, other components may still hold a handle to

    /// the component and send it messages!

    fn on_shutdown(&mut self, sched_ctx: &SchedulerCtx);

    /// Called if the component is created by another component and the messages

    /// are being transferred between the two.

    fn adopt_message(&mut self, comp_ctx: &mut CompCtx, message: DataMessage);

    /// Called if the component receives a new message. The component is

    /// responsible for deciding where that messages goes.

    fn handle_message(&mut self, sched_ctx: &mut SchedulerCtx, comp_ctx: &mut CompCtx, message: Message);

    /// Called if the component's routine should be executed. The return value

    /// can be used to indicate when the routine should be run again.

    fn run(&mut self, sched_ctx: &mut SchedulerCtx, comp_ctx: &mut CompCtx) -> CompScheduling;

}

/// Representation of the generic operating mode of a component. Although not

/// every state may be used by every kind of (builtin) component, this allows

/// writing standard handlers for particular events in a component's lifetime.

#[derive(Debug, Copy, Clone, PartialEq, Eq)]

pub(crate) enum CompMode {

    NonSync, // not in sync mode

    Sync, // in sync mode, can interact with other components

    SyncEnd, // awaiting a solution, i.e. encountered the end of the sync block

    BlockedGet, // blocked because we need to receive a message on a particular port

    BlockedPut, // component is blocked because the port is blocked

    BlockedSelect, // waiting on message to complete the select statement

    BlockedPutPortsAwaitingAcks,// blocked because we're waiting to send a data message containing ports, but first need to receive Acks for the PortPeerChanged messages

    BlockedPutPortsReady, // blocked because we're waitingto send a data message containing ports

    StartExit, // temporary state: if encountered then we start the shutdown process.

    BusyExit, // temporary state: waiting for Acks for all the closed ports, potentially waiting for sync round to finish

    Exit, // exiting: shutdown process started, now waiting until the reference count drops to 0

}

impl CompMode {

    pub(crate) fn is_in_sync_block(&self) -> bool {

        use CompMode::*;

        match self {

            Sync | SyncEnd | BlockedGet | BlockedPut | BlockedSelect |

                BlockedPutPortsAwaitingAcks | BlockedPutPortsReady => true,

            NonSync | StartExit | BusyExit | Exit => false,

        }

    }

    pub(crate) fn is_busy_exiting(&self) -> bool {

        use CompMode::*;

        match self {

            NonSync | Sync | SyncEnd | BlockedGet | BlockedPut | BlockedSelect |

                BlockedPutPortsAwaitingAcks | BlockedPutPortsReady => false,

            StartExit | BusyExit => true,

            Exit => false,

        }

    }

}

#[derive(Debug)]

pub(crate) enum ExitReason {

    Termination, // regular termination of component

    ErrorInSync,

    ErrorNonSync,

}

impl ExitReason {

    pub(crate) fn is_in_sync(&self) -> bool {

        use ExitReason::*;

        match self {

            Termination | ErrorNonSync => false,

            ErrorInSync => true,

        }

    }

    pub(crate) fn is_error(&self) -> bool {

        use ExitReason::*;

        match self {

            Termination => false,

            ErrorInSync | ErrorNonSync => true,

        }

    }

}

/// Component execution state: the execution mode along with some descriptive

/// fields. Fields are public for ergonomic reasons, use member functions when

/// appropriate.

pub(crate) struct CompExecState {

    pub mode: CompMode,

    pub mode_port: PortId, // valid if blocked on a port (put/get)

    pub mode_value: ValueGroup, // valid if blocked on a put

    pub exit_reason: ExitReason, // valid if in StartExit/BusyExit/Exit mode

}

impl CompExecState {

    pub(crate) fn new() -> Self {

        return Self{

            mode: CompMode::NonSync,

            mode_port: PortId::new_invalid(),

            mode_value: ValueGroup::default(),

            exit_reason: ExitReason::Termination,

        }

    }

    pub(crate) fn set_as_start_exit(&mut self, reason: ExitReason) {

        self.mode = CompMode::StartExit;

        self.exit_reason = reason;

    }

    pub(crate) fn set_as_blocked_get(&mut self, port: PortId) {

        self.mode = CompMode::BlockedGet;

        self.mode_port = port;

        debug_assert!(self.mode_value.values.is_empty());

    }

    pub(crate) fn is_blocked_on_get(&self, port: PortId) -> bool {

        return

            self.mode == CompMode::BlockedGet &&

            self.mode_port == port;

    }

    pub(crate) fn set_as_blocked_put_without_ports(&mut self, port: PortId, value: ValueGroup) {

        self.mode = CompMode::BlockedPut;

        self.mode_port = port;

        self.mode_value = value;

    }

    pub(crate) fn set_as_blocked_put_with_ports(&mut self, port: PortId, value: ValueGroup) {

        self.mode = CompMode::BlockedPutPortsAwaitingAcks;

        self.mode_port = port;

        self.mode_value = value;

    }

    pub(crate) fn is_blocked_on_put_without_ports(&self, port: PortId) -> bool {

        return

            self.mode == CompMode::BlockedPut &&

            self.mode_port == port;

    }

    pub(crate) fn is_blocked_on_put_with_ports(&self, port: PortId) -> bool {

        return

            self.mode == CompMode::BlockedPutPortsReady &&

            self.mode_port == port;

    }

}

// TODO: Replace when implementing port sending. Should probably be incorporated

//  into CompCtx (and rename CompCtx into CompComms)

pub(crate) type InboxMain = Vec<Option<DataMessage>>;

pub(crate) type InboxMainRef = [Option<DataMessage>];

pub(crate) type InboxBackup = Vec<DataMessage>;

/// Creates a new component based on its definition. Meaning that if it is a

/// user-defined component then we set up the PDL code state. Otherwise we

/// construct a custom component. This does NOT take care of port and message

/// management.

pub(crate) fn create_component(

    protocol: &ProtocolDescription,

    definition_id: ProcedureDefinitionId, type_id: TypeId,

    arguments: ValueGroup, num_ports: usize

) -> Box<dyn Component> {

    let definition = &protocol.heap[definition_id];

    debug_assert!(definition.kind == ProcedureKind::Primitive || definition.kind == ProcedureKind::Composite);

    if definition.source.is_builtin() {

        // Builtin component

        let component: Box<dyn Component> = match definition.source {

            ProcedureSource::CompRandomU32 => Box::new(ComponentRandomU32::new(arguments)),

            ProcedureSource::CompTcpClient => Box::new(ComponentTcpClient::new(arguments)),

            _ => unreachable!(),

        };

        return component;

    } else {

        // User-defined component

        let prompt = Prompt::new(

            &protocol.types, &protocol.heap,

            definition_id, type_id, arguments

        );

        let component = CompPDL::new(prompt, num_ports);

        return Box::new(component);

    }

}

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

// Generic component messaging utilities (for sending and receiving)

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

/// Default handling of sending a data message. In case the port is blocked then

/// the `ExecState` will become blocked as well. Note that

/// `default_handle_control_message` will ensure that the port becomes

/// unblocked if so instructed by the receiving component. The returned

/// scheduling value must be used.

#[must_use]

pub(crate) fn default_send_data_message(

    exec_state: &mut CompExecState, transmitting_port_id: PortId,

    port_instruction: PortInstruction, value: ValueGroup,

    sched_ctx: &SchedulerCtx, consensus: &mut Consensus,

    control: &mut ControlLayer, comp_ctx: &mut CompCtx

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

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

    let port_handle = comp_ctx.get_port_handle(transmitting_port_id);

    let port_info = comp_ctx.get_port_mut(port_handle);

    port_info.last_instruction = port_instruction;

    let port_info = comp_ctx.get_port(port_handle);

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

    let mut ports = Vec::new();

    find_ports_in_value_group(&value, &mut ports);

    if port_info.state.is_closed() {

        // Note: normally peer is eventually consistent, but if it has shut down

        // then we can be sure it is consistent (I think?)

        return Err((

            port_info.last_instruction,

            format!("Cannot send on this port, as the peer (id:{}) has shut down", port_info.peer_comp_id.0)

        ))

    } else if !ports.is_empty() {

        prepare_send_message_with_ports(

            transmitting_port_id, port_instruction, value, exec_state,

            comp_ctx, sched_ctx, control

        )?;

        return Ok(CompScheduling::Sleep);

    } else if port_info.state.is_blocked() {

        // Port is blocked, so we cannot send

        exec_state.set_as_blocked_put_without_ports(transmitting_port_id, value);

        return Ok(CompScheduling::Sleep);

    } else {

        // Port is not blocked and no ports to transfer: send to the peer

        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);

        return Ok(CompScheduling::Immediate);

    }

}

pub(crate) enum IncomingData {

    PlacedInSlot,

    SlotFull(DataMessage),

}

/// Default handling of receiving a data message. In case there is no room for

/// the message it is returned from this function. Note that this function is

/// different from PDL code performing a `get` on a port; this is the case where

/// the message first arrives at the component.

// NOTE: This is supposed to be a somewhat temporary implementation. It would be

//  nicest if the sending component can figure out it cannot send any more data.

#[must_use]

pub(crate) fn default_handle_incoming_data_message(

    exec_state: &mut CompExecState, inbox_main: &mut InboxMain,

    comp_ctx: &mut CompCtx, incoming_message: DataMessage,

    sched_ctx: &SchedulerCtx, control: &mut ControlLayer

) -> IncomingData {

    let port_handle = comp_ctx.get_port_handle(incoming_message.data_header.target_port);

    let port_index = comp_ctx.get_port_index(port_handle);

    comp_ctx.get_port_mut(port_handle).received_message_for_sync = true;

    let port_value_slot = &mut inbox_main[port_index];

    let target_port_id = incoming_message.data_header.target_port;

    if port_value_slot.is_none() {

        // We can put the value in the slot

        *port_value_slot = Some(incoming_message);

        // Check if we're blocked on receiving this message.

        dbg_code!({

            // Our port cannot have been blocked itself, because we're able to

            // directly insert the message into its slot.

            assert!(!comp_ctx.get_port(port_handle).state.is_blocked());

        });

        if exec_state.is_blocked_on_get(target_port_id) {

            // Return to normal operation

            exec_state.mode = CompMode::Sync;

            exec_state.mode_port = PortId::new_invalid();

            debug_assert!(exec_state.mode_value.values.is_empty());

        }

        return IncomingData::PlacedInSlot

    } else {

        // Slot is already full, so if the port was previously opened, it will

        // now become closed

        let port_info = comp_ctx.get_port_mut(port_handle);

        if port_info.state.is_open() {

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

            let (peer_handle, message) =

                control.initiate_port_blocking(comp_ctx, port_handle);

            let peer = comp_ctx.get_peer(peer_handle);

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

        }

        return IncomingData::SlotFull(incoming_message)

    }

}

pub(crate) enum GetResult {

    Received(DataMessage),

    NoMessage,

    Error((PortInstruction, String)),

}

/// Default attempt at trying to receive from a port (i.e. through a `get`, or

/// the equivalent operation for a builtin component). `target_port` is the port

/// we're trying to receive from, and the `target_port_instruction` is the

/// instruction we're attempting on this port.

pub(crate) fn default_attempt_get(

    exec_state: &mut CompExecState, target_port: PortId, target_port_instruction: PortInstruction,

    inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup, sched_ctx: &SchedulerCtx,

    comp_ctx: &mut CompCtx, control: &mut ControlLayer, consensus: &mut Consensus

) -> GetResult {

    let port_handle = comp_ctx.get_port_handle(target_port);

    let port_index = comp_ctx.get_port_index(port_handle);

    let port_info = comp_ctx.get_port_mut(port_handle);

    port_info.last_instruction = target_port_instruction;

    if port_info.state.is_closed() {

        let peer_id = port_info.peer_comp_id;

        return GetResult::Error((

            target_port_instruction,

            format!("Cannot get from this port, as the peer component (id:{}) closed the port", peer_id.0)

        ));

    }

    if let Some(message) = &inbox_main[port_index] {

        if consensus.try_receive_data_message(sched_ctx, comp_ctx, message) {

            // We're allowed to receive this message

            let mut message = inbox_main[port_index].take().unwrap();

            debug_assert_eq!(target_port, message.data_header.target_port);

            // Note: we can still run into an unrecoverable error when actually

            // receiving this message

            match default_handle_received_data_message(

                target_port, target_port_instruction,

                &mut message, inbox_main, inbox_backup,

                comp_ctx, sched_ctx, control,

            ) {

                Ok(()) => return GetResult::Received(message),

                Err(location_and_message) => return GetResult::Error(location_and_message)

            }

        } else {

            // We're not allowed to receive this message. This means that the

            // receiver is attempting to receive something out of order with

            // respect to the sender.

            return GetResult::Error((target_port_instruction, String::from(

                "Cannot get from this port, as this causes a deadlock. This happens if you `get` in a different order as another component `put`s"

            )));

        }

    } else {

        // We don't have a message waiting for us and the port is not blocked.

        // So enter the BlockedGet state

        exec_state.set_as_blocked_get(target_port);

        return GetResult::NoMessage;

    }

}

/// Default handling that has been received through a `get`. Will check if any

/// more messages are waiting, and if the corresponding port was blocked because

/// of full buffers (hence, will use the control layer to make sure the peer

/// will become unblocked).

pub(crate) fn default_handle_received_data_message(

    targeted_port: PortId, _port_instruction: PortInstruction, message: &mut DataMessage,

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

    comp_ctx: &mut CompCtx, sched_ctx: &SchedulerCtx, control: &mut ControlLayer

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

    let port_handle = comp_ctx.get_port_handle(targeted_port);

    let port_index = comp_ctx.get_port_index(port_handle);

    debug_assert!(inbox_main[port_index].is_none()); // because we've just received from it

    // If we received any ports, add them to the port tracking and inbox struct.

    // Then notify the peers that they can continue sending to this port, but

    // now at a new address.

    for received_port in &mut message.ports {

        // Transfer messages to main/backup inbox

        let _new_inbox_index = inbox_main.len();

        if !received_port.messages.is_empty() {

            inbox_main.push(Some(received_port.messages.remove(0)));

        }

        // Create a new port locally

        let mut new_port_state = received_port.state;

        new_port_state.set(PortStateFlag::Received);

        let new_port_handle = comp_ctx.add_port(

            received_port.peer_comp, received_port.peer_port,

            received_port.kind, new_port_state

        );

        debug_assert_eq!(_new_inbox_index, comp_ctx.get_port_index(new_port_handle));

        comp_ctx.change_port_peer(sched_ctx, new_port_handle, Some(received_port.peer_comp));

        let new_port = comp_ctx.get_port(new_port_handle);

        // Replace all references to the port in the received message

        for message_location in received_port.locations.iter().copied() {

            let value = match message_location {

                ValueId::Heap(heap_pos, heap_index) => &mut message.content.regions[heap_pos as usize][heap_index as usize],

                ValueId::Stack(stack_index) => &mut message.content.values[stack_index as usize],

            };

            match value {

                Value::Input(_) => {

                    debug_assert_eq!(new_port.kind, PortKind::Getter);

                    *value = Value::Input(port_id_to_eval(new_port.self_id));

                },

                Value::Output(_) => {

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

                    *value = Value::Output(port_id_to_eval(new_port.self_id));

                },

                _ => unreachable!(),

            }

        }

        // Let the peer know that the port can now be used

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

        let peer_info = comp_ctx.get_peer(peer_handle);

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

            id: ControlId::new_invalid(),

            sender_comp_id: comp_ctx.id,

            target_port_id: Some(new_port.peer_port_id),

            content: ControlMessageContent::PortPeerChangedUnblock(new_port.self_id, comp_ctx.id)

        }), true);

    }

    // Modify last-known location where port instruction was retrieved

    let port_info = comp_ctx.get_port(port_handle);

    debug_assert_ne!(port_info.last_instruction, PortInstruction::None); // set by caller

    debug_assert!(port_info.state.is_open()); // checked by caller

    // Check if there are any more messages in the backup buffer

    for message_index in 0..inbox_backup.len() {

        let message = &inbox_backup[message_index];

        if message.data_header.target_port == targeted_port {

            // One more message, place it in the slot

            let message = inbox_backup.remove(message_index);

            debug_assert!(comp_ctx.get_port(port_handle).state.is_blocked()); // since we're removing another message from the backup

            inbox_main[port_index] = Some(message);

            return Ok(());

        }

    }

    // Did not have any more messages, so if we were blocked, then we need to

    // unblock the port now (and inform the peer of this unblocking)

    if port_info.state.is_set(PortStateFlag::BlockedDueToFullBuffers) {

        let port_info = comp_ctx.get_port_mut(port_handle);

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

        let (peer_handle, message) = control.cancel_port_blocking(comp_ctx, port_handle);

        let peer_info = comp_ctx.get_peer(peer_handle);

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

    }

    return Ok(());

}

/// Handles control messages in the default way. Note that this function may

/// take a lot of actions in the name of the caller: pending messages may be

/// sent, ports may become blocked/unblocked, etc. So the execution

/// (`CompExecState`), control (`ControlLayer`) and consensus (`Consensus`)

/// state may all change.

pub(crate) fn default_handle_control_message(

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

    message: ControlMessage, sched_ctx: &SchedulerCtx, comp_ctx: &mut CompCtx,

    inbox_main: &mut InboxMain, inbox_backup: &mut InboxBackup

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

    match message.content {

        ControlMessageContent::Ack => {

            default_handle_ack(exec_state, control, message.id, sched_ctx, comp_ctx, consensus, inbox_main, inbox_backup);

        },

        ControlMessageContent::BlockPort => {

            // One of our messages was accepted, but the port should be

            // blocked.

            let port_to_block = message.target_port_id.unwrap();

            let port_handle = comp_ctx.get_port_handle(port_to_block);

            let port_info = comp_ctx.get_port_mut(port_handle);

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

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

        },

        ControlMessageContent::ClosePort(content) => {

            // Request to close the port. We immediately comply and remove

            // the component handle as well

            let port_to_close = message.target_port_id.unwrap();

            let port_handle = comp_ctx.get_port_handle(port_to_close);

            // We're closing the port, so we will always update the peer of the

            // port (in case of error messages)

            let port_info = comp_ctx.get_port_mut(port_handle);

            port_info.peer_comp_id = message.sender_comp_id;

            port_info.close_at_sync_end = true; // might be redundant (we might set it closed now)

            let peer_comp_id = port_info.peer_comp_id;

            let peer_handle = comp_ctx.get_peer_handle(peer_comp_id);

            // One exception to sending an `Ack` is if we just closed the

            // port ourselves, meaning that the `ClosePort` messages got

            // sent to one another.

            if let Some(control_id) = control.has_close_port_entry(port_handle, comp_ctx) {

                // The two components (sender and this component) are closing

                // the channel at the same time. So we don't care about the

                // content of the `ClosePort` message.

                default_handle_ack(exec_state, control, control_id, sched_ctx, comp_ctx, consensus, inbox_main, inbox_backup);

            } else {

                // Respond to the message

                let port_info = comp_ctx.get_port(port_handle);

                let last_instruction = port_info.last_instruction;

                let port_has_had_message = port_info.received_message_for_sync;

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

                comp_ctx.change_port_peer(sched_ctx, port_handle, None);

                // Handle any possible error conditions (which boil down to: the

                // port has been used, but the peer has died). If not in sync

                // mode then we close the port immediately.

                // Note that `port_was_used` does not mean that any messages

                // were actually received. It might also mean that e.g. the

                // component attempted a `get`, but there were no messages, so

                // now it is in the `BlockedGet` state.

                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, 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, 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);

        println!("DEBUG: Considering port:\n{:?}", port);

        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);

    }

}

/// 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 prepare_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

    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()); // requisite for calling this function

    // 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;