use crate::duties_service::{DutiesService, DutyAndProof};
use beacon_node_fallback::{ApiTopic, BeaconNodeFallback};
use futures::future::join_all;
use logging::crit;
use slot_clock::SlotClock;
use std::collections::HashMap;
use std::ops::Deref;
use std::sync::Arc;
use task_executor::TaskExecutor;
use tokio::time::{Duration, Instant, sleep, sleep_until};
use tracing::{Instrument, Span, debug, error, info, info_span, instrument, trace, warn};
use tree_hash::TreeHash;
use types::{Attestation, AttestationData, ChainSpec, CommitteeIndex, EthSpec, Slot};
use validator_store::{Error as ValidatorStoreError, ValidatorStore};

/// Builds an `AttestationService`.
#[derive(Default)]
pub struct AttestationServiceBuilder<S: ValidatorStore, T: SlotClock + 'static> {
    duties_service: Option<Arc<DutiesService<S, T>>>,
    validator_store: Option<Arc<S>>,
    slot_clock: Option<T>,
    beacon_nodes: Option<Arc<BeaconNodeFallback<T>>>,
    executor: Option<TaskExecutor>,
    chain_spec: Option<Arc<ChainSpec>>,
    disable: bool,
}

impl<S: ValidatorStore + 'static, T: SlotClock + 'static> AttestationServiceBuilder<S, T> {
    pub fn new() -> Self {
        Self {
            duties_service: None,
            validator_store: None,
            slot_clock: None,
            beacon_nodes: None,
            executor: None,
            chain_spec: None,
            disable: false,
        }
    }

    pub fn duties_service(mut self, service: Arc<DutiesService<S, T>>) -> Self {
        self.duties_service = Some(service);
        self
    }

    pub fn validator_store(mut self, store: Arc<S>) -> Self {
        self.validator_store = Some(store);
        self
    }

    pub fn slot_clock(mut self, slot_clock: T) -> Self {
        self.slot_clock = Some(slot_clock);
        self
    }

    pub fn beacon_nodes(mut self, beacon_nodes: Arc<BeaconNodeFallback<T>>) -> Self {
        self.beacon_nodes = Some(beacon_nodes);
        self
    }

    pub fn executor(mut self, executor: TaskExecutor) -> Self {
        self.executor = Some(executor);
        self
    }

    pub fn chain_spec(mut self, chain_spec: Arc<ChainSpec>) -> Self {
        self.chain_spec = Some(chain_spec);
        self
    }

    pub fn disable(mut self, disable: bool) -> Self {
        self.disable = disable;
        self
    }

    pub fn build(self) -> Result<AttestationService<S, T>, String> {
        Ok(AttestationService {
            inner: Arc::new(Inner {
                duties_service: self
                    .duties_service
                    .ok_or("Cannot build AttestationService without duties_service")?,
                validator_store: self
                    .validator_store
                    .ok_or("Cannot build AttestationService without validator_store")?,
                slot_clock: self
                    .slot_clock
                    .ok_or("Cannot build AttestationService without slot_clock")?,
                beacon_nodes: self
                    .beacon_nodes
                    .ok_or("Cannot build AttestationService without beacon_nodes")?,
                executor: self
                    .executor
                    .ok_or("Cannot build AttestationService without executor")?,
                chain_spec: self
                    .chain_spec
                    .ok_or("Cannot build AttestationService without chain_spec")?,
                disable: self.disable,
            }),
        })
    }
}

/// Helper to minimise `Arc` usage.
pub struct Inner<S, T> {
    duties_service: Arc<DutiesService<S, T>>,
    validator_store: Arc<S>,
    slot_clock: T,
    beacon_nodes: Arc<BeaconNodeFallback<T>>,
    executor: TaskExecutor,
    chain_spec: Arc<ChainSpec>,
    disable: bool,
}

/// Attempts to produce attestations for all known validators 1/3rd of the way through each slot.
///
/// If any validators are on the same committee, a single attestation will be downloaded and
/// returned to the beacon node. This attestation will have a signature from each of the
/// validators.
pub struct AttestationService<S, T> {
    inner: Arc<Inner<S, T>>,
}

impl<S, T> Clone for AttestationService<S, T> {
    fn clone(&self) -> Self {
        Self {
            inner: self.inner.clone(),
        }
    }
}

impl<S, T> Deref for AttestationService<S, T> {
    type Target = Inner<S, T>;

    fn deref(&self) -> &Self::Target {
        self.inner.deref()
    }
}

impl<S: ValidatorStore + 'static, T: SlotClock + 'static> AttestationService<S, T> {
    /// Starts the service which periodically produces attestations.
    pub fn start_update_service(self, spec: &ChainSpec) -> Result<(), String> {
        if self.disable {
            info!("Attestation service disabled");
            return Ok(());
        }

        let slot_duration = Duration::from_secs(spec.seconds_per_slot);
        let duration_to_next_slot = self
            .slot_clock
            .duration_to_next_slot()
            .ok_or("Unable to determine duration to next slot")?;

        info!(
            next_update_millis = duration_to_next_slot.as_millis(),
            "Attestation production service started"
        );

        let executor = self.executor.clone();

        let interval_fut = async move {
            loop {
                if let Some(duration_to_next_slot) = self.slot_clock.duration_to_next_slot() {
                    sleep(duration_to_next_slot + slot_duration / 3).await;

                    if let Err(e) = self.spawn_attestation_tasks(slot_duration) {
                        crit!(error = e, "Failed to spawn attestation tasks")
                    } else {
                        trace!("Spawned attestation tasks");
                    }
                } else {
                    error!("Failed to read slot clock");
                    // If we can't read the slot clock, just wait another slot.
                    sleep(slot_duration).await;
                    continue;
                }
            }
        };

        executor.spawn(interval_fut, "attestation_service");
        Ok(())
    }

    /// Spawn only one new task for attestation post-Electra
    /// For each required aggregates, spawn a new task that downloads, signs and uploads the
    /// aggregates to the beacon node.
    fn spawn_attestation_tasks(&self, slot_duration: Duration) -> Result<(), String> {
        let slot = self.slot_clock.now().ok_or("Failed to read slot clock")?;
        let duration_to_next_slot = self
            .slot_clock
            .duration_to_next_slot()
            .ok_or("Unable to determine duration to next slot")?;

        // Create and publish an `Attestation` for all validators only once
        // as the committee_index is not included in AttestationData post-Electra
        let attestation_duties: Vec<_> = self.duties_service.attesters(slot).into_iter().collect();

        // Return early if there is no attestation duties
        if attestation_duties.is_empty() {
            return Ok(());
        }

        let attestation_service = self.clone();

        let attestation_data_handle = self
            .inner
            .executor
            .spawn_handle(
                async move {
                    let attestation_data = attestation_service
                        .beacon_nodes
                        .first_success(|beacon_node| async move {
                            let _timer = validator_metrics::start_timer_vec(
                                &validator_metrics::ATTESTATION_SERVICE_TIMES,
                                &[validator_metrics::ATTESTATIONS_HTTP_GET],
                            );
                            beacon_node
                                .get_validator_attestation_data(slot, 0)
                                .await
                                .map_err(|e| format!("Failed to produce attestation data: {:?}", e))
                                .map(|result| result.data)
                        })
                        .await
                        .map_err(|e| e.to_string())?;

                    attestation_service
                        .sign_and_publish_attestations(
                            slot,
                            &attestation_duties,
                            attestation_data.clone(),
                        )
                        .await
                        .map_err(|e| {
                            crit!(
                                error = format!("{:?}", e),
                                slot = slot.as_u64(),
                                "Error during attestation routine"
                            );
                            e
                        })?;
                    Ok::<AttestationData, String>(attestation_data)
                },
                "unaggregated attestation production",
            )
            .ok_or("Failed to spawn attestation data task")?;

        // If a validator needs to publish an aggregate attestation, they must do so at 2/3
        // through the slot. This delay triggers at this time
        let aggregate_production_instant = Instant::now()
            + duration_to_next_slot
                .checked_sub(slot_duration / 3)
                .unwrap_or_else(|| Duration::from_secs(0));

        let aggregate_duties_by_committee_index: HashMap<CommitteeIndex, Vec<DutyAndProof>> = self
            .duties_service
            .attesters(slot)
            .into_iter()
            .fold(HashMap::new(), |mut map, duty_and_proof| {
                map.entry(duty_and_proof.duty.committee_index)
                    .or_default()
                    .push(duty_and_proof);
                map
            });

        // Spawn a task that awaits the attestation data handle and then spawns aggregate tasks
        let attestation_service_clone = self.clone();
        let executor = self.inner.executor.clone();
        self.inner.executor.spawn(
            async move {
                // Log an error if the handle fails and return, skipping aggregates
                let attestation_data = match attestation_data_handle.await {
                    Ok(Some(Ok(data))) => data,
                    Ok(Some(Err(err))) => {
                        error!(?err, "Attestation production failed");
                        return;
                    }
                    Ok(None) | Err(_) => {
                        info!("Aborting attestation production due to shutdown");
                        return;
                    }
                };

                // For each committee index for this slot:
                // Create and publish `SignedAggregateAndProof` for all aggregating validators.
                aggregate_duties_by_committee_index.into_iter().for_each(
                    |(committee_index, validator_duties)| {
                        let attestation_service = attestation_service_clone.clone();
                        let attestation_data = attestation_data.clone();
                        executor.spawn_ignoring_error(
                            attestation_service.handle_aggregates(
                                slot,
                                committee_index,
                                validator_duties,
                                aggregate_production_instant,
                                attestation_data,
                            ),
                            "aggregate publish",
                        );
                    },
                )
            },
            "attestation and aggregate publish",
        );

        // Schedule pruning of the slashing protection database once all unaggregated
        // attestations have (hopefully) been signed, i.e. at the same time as aggregate
        // production.
        self.spawn_slashing_protection_pruning_task(slot, aggregate_production_instant);

        Ok(())
    }

    #[instrument(
        name = "handle_aggregates",
        skip_all,
        fields(%slot, %committee_index)
    )]
    async fn handle_aggregates(
        self,
        slot: Slot,
        committee_index: CommitteeIndex,
        validator_duties: Vec<DutyAndProof>,
        aggregate_production_instant: Instant,
        attestation_data: AttestationData,
    ) -> Result<(), ()> {
        // There's not need to produce `SignedAggregateAndProof` if we do not have
        // any validators for the given `slot` and `committee_index`.
        if validator_duties.is_empty() {
            return Ok(());
        }

        // Wait until the `aggregation_production_instant` (2/3rds
        // of the way though the slot). As verified in the
        // `delay_triggers_when_in_the_past` test, this code will still run
        // even if the instant has already elapsed.
        sleep_until(aggregate_production_instant).await;

        // Start the metrics timer *after* we've done the delay.
        let _aggregates_timer = validator_metrics::start_timer_vec(
            &validator_metrics::ATTESTATION_SERVICE_TIMES,
            &[validator_metrics::AGGREGATES],
        );

        // Download, sign and publish a `SignedAggregateAndProof` for each
        // validator that is elected to aggregate for this `slot` and
        // `committee_index`.
        self.produce_and_publish_aggregates(&attestation_data, committee_index, &validator_duties)
            .await
            .map_err(move |e| {
                crit!(
                    error = format!("{:?}", e),
                    committee_index,
                    slot = slot.as_u64(),
                    "Error during aggregate attestation routine"
                )
            })?;

        Ok(())
    }

    /// Performs the main steps of the attesting process: signing and publishing to the BN.
    ///
    /// https://github.com/ethereum/consensus-specs/blob/master/specs/phase0/validator.md#attesting
    ///
    /// ## Detail
    ///
    /// The given `validator_duties` should already be filtered to only contain those that match
    /// `slot`. Critical errors will be logged if this is not the case.
    #[instrument(skip_all, fields(%slot, %attestation_data.beacon_block_root))]
    async fn sign_and_publish_attestations(
        &self,
        slot: Slot,
        validator_duties: &[DutyAndProof],
        attestation_data: AttestationData,
    ) -> Result<(), String> {
        let _attestations_timer = validator_metrics::start_timer_vec(
            &validator_metrics::ATTESTATION_SERVICE_TIMES,
            &[validator_metrics::ATTESTATIONS],
        );

        let current_epoch = self
            .slot_clock
            .now()
            .ok_or("Unable to determine current slot from clock")?
            .epoch(S::E::slots_per_epoch());

        // Create futures to produce signed `Attestation` objects.
        let attestation_data_ref = &attestation_data;
        let signing_futures = validator_duties.iter().map(|duty_and_proof| {
            async move {
                let duty = &duty_and_proof.duty;
                let attestation_data = attestation_data_ref;

                // Ensure that the attestation matches the duties.
                if !duty.match_attestation_data::<S::E>(attestation_data, &self.chain_spec) {
                    crit!(
                        validator = ?duty.pubkey,
                        duty_slot = %duty.slot,
                        attestation_slot = %attestation_data.slot,
                        duty_index = duty.committee_index,
                        attestation_index = attestation_data.index,
                        "Inconsistent validator duties during signing"
                    );
                    return None;
                }

                let mut attestation = match Attestation::empty_for_signing(
                    duty.committee_index,
                    duty.committee_length as usize,
                    attestation_data.slot,
                    attestation_data.beacon_block_root,
                    attestation_data.source,
                    attestation_data.target,
                    &self.chain_spec,
                ) {
                    Ok(attestation) => attestation,
                    Err(err) => {
                        crit!(
                            validator = ?duty.pubkey,
                            ?duty,
                            ?err,
                            "Invalid validator duties during signing"
                        );
                        return None;
                    }
                };

                match self
                    .validator_store
                    .sign_attestation(
                        duty.pubkey,
                        duty.validator_committee_index as usize,
                        &mut attestation,
                        current_epoch,
                    )
                    .await
                {
                    Ok(()) => Some((attestation, duty.validator_index)),
                    Err(ValidatorStoreError::UnknownPubkey(pubkey)) => {
                        // A pubkey can be missing when a validator was recently
                        // removed via the API.
                        warn!(
                            info = "a validator may have recently been removed from this VC",
                            pubkey = ?pubkey,
                            validator = ?duty.pubkey,
                            slot = slot.as_u64(),
                            "Missing pubkey for attestation"
                        );
                        None
                    }
                    Err(e) => {
                        crit!(
                            error = ?e,
                            validator = ?duty.pubkey,
                            slot = slot.as_u64(),
                            "Failed to sign attestation"
                        );
                        None
                    }
                }
            }
            .instrument(Span::current())
        });

        // Execute all the futures in parallel, collecting any successful results.
        let (ref attestations, ref validator_indices): (Vec<_>, Vec<_>) = join_all(signing_futures)
            .instrument(info_span!(
                "sign_attestations",
                count = validator_duties.len()
            ))
            .await
            .into_iter()
            .flatten()
            .unzip();

        if attestations.is_empty() {
            warn!("No attestations were published");
            return Ok(());
        }
        let fork_name = self
            .chain_spec
            .fork_name_at_slot::<S::E>(attestation_data.slot);

        // Post the attestations to the BN.
        match self
            .beacon_nodes
            .request(ApiTopic::Attestations, |beacon_node| async move {
                let _timer = validator_metrics::start_timer_vec(
                    &validator_metrics::ATTESTATION_SERVICE_TIMES,
                    &[validator_metrics::ATTESTATIONS_HTTP_POST],
                );

                let single_attestations = attestations
                    .iter()
                    .zip(validator_indices)
                    .filter_map(|(a, i)| {
                        match a.to_single_attestation_with_attester_index(*i) {
                            Ok(a) => Some(a),
                            Err(e) => {
                                // This shouldn't happen unless BN and VC are out of sync with
                                // respect to the Electra fork.
                                error!(
                                    error = ?e,
                                    committee_index = attestation_data.index,
                                    slot = slot.as_u64(),
                                    "type" = "unaggregated",
                                    "Unable to convert to SingleAttestation"
                                );
                                None
                            }
                        }
                    })
                    .collect::<Vec<_>>();

                beacon_node
                    .post_beacon_pool_attestations_v2::<S::E>(single_attestations, fork_name)
                    .await
            })
            .instrument(info_span!(
                "publish_attestations",
                count = attestations.len()
            ))
            .await
        {
            Ok(()) => info!(
                count = attestations.len(),
                validator_indices = ?validator_indices,
                head_block = ?attestation_data.beacon_block_root,
                committee_index = attestation_data.index,
                slot = attestation_data.slot.as_u64(),
                "type" = "unaggregated",
                "Successfully published attestations"
            ),
            Err(e) => error!(
                error = %e,
                committee_index = attestation_data.index,
                slot = slot.as_u64(),
                "type" = "unaggregated",
                "Unable to publish attestations"
            ),
        }

        Ok(())
    }

    /// Performs the second step of the attesting process: downloading an aggregated `Attestation`,
    /// converting it into a `SignedAggregateAndProof` and returning it to the BN.
    ///
    /// https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/validator.md#broadcast-aggregate
    ///
    /// ## Detail
    ///
    /// The given `validator_duties` should already be filtered to only contain those that match
    /// `slot` and `committee_index`. Critical errors will be logged if this is not the case.
    ///
    /// Only one aggregated `Attestation` is downloaded from the BN. It is then cloned and signed
    /// by each validator and the list of individually-signed `SignedAggregateAndProof` objects is
    /// returned to the BN.
    #[instrument(skip_all, fields(slot = %attestation_data.slot, %committee_index))]
    async fn produce_and_publish_aggregates(
        &self,
        attestation_data: &AttestationData,
        committee_index: CommitteeIndex,
        validator_duties: &[DutyAndProof],
    ) -> Result<(), String> {
        if !validator_duties
            .iter()
            .any(|duty_and_proof| duty_and_proof.selection_proof.is_some())
        {
            // Exit early if no validator is aggregator
            return Ok(());
        }

        let fork_name = self
            .chain_spec
            .fork_name_at_slot::<S::E>(attestation_data.slot);

        let aggregated_attestation = &self
            .beacon_nodes
            .first_success(|beacon_node| async move {
                let _timer = validator_metrics::start_timer_vec(
                    &validator_metrics::ATTESTATION_SERVICE_TIMES,
                    &[validator_metrics::AGGREGATES_HTTP_GET],
                );
                if fork_name.electra_enabled() {
                    beacon_node
                        .get_validator_aggregate_attestation_v2(
                            attestation_data.slot,
                            attestation_data.tree_hash_root(),
                            committee_index,
                        )
                        .await
                        .map_err(|e| {
                            format!("Failed to produce an aggregate attestation: {:?}", e)
                        })?
                        .ok_or_else(|| format!("No aggregate available for {:?}", attestation_data))
                        .map(|result| result.into_data())
                } else {
                    beacon_node
                        .get_validator_aggregate_attestation_v1(
                            attestation_data.slot,
                            attestation_data.tree_hash_root(),
                        )
                        .await
                        .map_err(|e| {
                            format!("Failed to produce an aggregate attestation: {:?}", e)
                        })?
                        .ok_or_else(|| format!("No aggregate available for {:?}", attestation_data))
                        .map(|result| result.data)
                }
            })
            .instrument(info_span!("fetch_aggregate_attestation"))
            .await
            .map_err(|e| e.to_string())?;

        // Create futures to produce the signed aggregated attestations.
        let signing_futures = validator_duties.iter().map(|duty_and_proof| async move {
            let duty = &duty_and_proof.duty;
            let selection_proof = duty_and_proof.selection_proof.as_ref()?;

            if !duty.match_attestation_data::<S::E>(attestation_data, &self.chain_spec) {
                crit!("Inconsistent validator duties during signing");
                return None;
            }

            match self
                .validator_store
                .produce_signed_aggregate_and_proof(
                    duty.pubkey,
                    duty.validator_index,
                    aggregated_attestation.clone(),
                    selection_proof.clone(),
                )
                .await
            {
                Ok(aggregate) => Some(aggregate),
                Err(ValidatorStoreError::UnknownPubkey(pubkey)) => {
                    // A pubkey can be missing when a validator was recently
                    // removed via the API.
                    debug!(?pubkey, "Missing pubkey for aggregate");
                    None
                }
                Err(e) => {
                    crit!(
                        error = ?e,
                        pubkey = ?duty.pubkey,
                        "Failed to sign aggregate"
                    );
                    None
                }
            }
        });

        // Execute all the futures in parallel, collecting any successful results.
        let aggregator_count = validator_duties
            .iter()
            .filter(|d| d.selection_proof.is_some())
            .count();
        let signed_aggregate_and_proofs = join_all(signing_futures)
            .instrument(info_span!("sign_aggregates", count = aggregator_count))
            .await
            .into_iter()
            .flatten()
            .collect::<Vec<_>>();

        if !signed_aggregate_and_proofs.is_empty() {
            let signed_aggregate_and_proofs_slice = signed_aggregate_and_proofs.as_slice();
            match self
                .beacon_nodes
                .first_success(|beacon_node| async move {
                    let _timer = validator_metrics::start_timer_vec(
                        &validator_metrics::ATTESTATION_SERVICE_TIMES,
                        &[validator_metrics::AGGREGATES_HTTP_POST],
                    );
                    if fork_name.electra_enabled() {
                        beacon_node
                            .post_validator_aggregate_and_proof_v2(
                                signed_aggregate_and_proofs_slice,
                                fork_name,
                            )
                            .await
                    } else {
                        beacon_node
                            .post_validator_aggregate_and_proof_v1(
                                signed_aggregate_and_proofs_slice,
                            )
                            .await
                    }
                })
                .instrument(info_span!(
                    "publish_aggregates",
                    count = signed_aggregate_and_proofs.len()
                ))
                .await
            {
                Ok(()) => {
                    for signed_aggregate_and_proof in signed_aggregate_and_proofs {
                        let attestation = signed_aggregate_and_proof.message().aggregate();
                        info!(
                            aggregator = signed_aggregate_and_proof.message().aggregator_index(),
                            signatures = attestation.num_set_aggregation_bits(),
                            head_block = format!("{:?}", attestation.data().beacon_block_root),
                            committee_index = attestation.committee_index(),
                            slot = attestation.data().slot.as_u64(),
                            "type" = "aggregated",
                            "Successfully published attestation"
                        );
                    }
                }
                Err(e) => {
                    for signed_aggregate_and_proof in signed_aggregate_and_proofs {
                        let attestation = &signed_aggregate_and_proof.message().aggregate();
                        crit!(
                            error = %e,
                            aggregator = signed_aggregate_and_proof.message().aggregator_index(),
                            committee_index = attestation.committee_index(),
                            slot = attestation.data().slot.as_u64(),
                            "type" = "aggregated",
                            "Failed to publish attestation"
                        );
                    }
                }
            }
        }

        Ok(())
    }

    /// Spawn a blocking task to run the slashing protection pruning process.
    ///
    /// Start the task at `pruning_instant` to avoid interference with other tasks.
    fn spawn_slashing_protection_pruning_task(&self, slot: Slot, pruning_instant: Instant) {
        let attestation_service = self.clone();
        let executor = self.inner.executor.clone();
        let current_epoch = slot.epoch(S::E::slots_per_epoch());

        // Wait for `pruning_instant` in a regular task, and then switch to a blocking one.
        self.inner.executor.spawn(
            async move {
                sleep_until(pruning_instant).await;

                executor.spawn_blocking(
                    move || {
                        attestation_service
                            .validator_store
                            .prune_slashing_protection_db(current_epoch, false)
                    },
                    "slashing_protection_pruning",
                )
            },
            "slashing_protection_pre_pruning",
        );
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use futures::future::FutureExt;
    use parking_lot::RwLock;

    /// This test is to ensure that a `tokio_timer::Sleep` with an instant in the past will still
    /// trigger.
    #[tokio::test]
    async fn delay_triggers_when_in_the_past() {
        let in_the_past = Instant::now() - Duration::from_secs(2);
        let state_1 = Arc::new(RwLock::new(in_the_past));
        let state_2 = state_1.clone();

        sleep_until(in_the_past)
            .map(move |()| *state_1.write() = Instant::now())
            .await;

        assert!(
            *state_2.read() > in_the_past,
            "state should have been updated"
        );
    }
}