forest/state_manager/

mod.rs

// Copyright 2019-2026 ChainSafe Systems
// SPDX-License-Identifier: Apache-2.0, MIT

#[cfg(test)]
mod tests;

mod cache;
pub mod chain_rand;
pub mod circulating_supply;
mod errors;
pub mod utils;

pub use self::errors::*;
use self::utils::structured;

use crate::beacon::{BeaconEntry, BeaconSchedule};
use crate::blocks::{Tipset, TipsetKey};
use crate::chain::{
    ChainStore,
    index::{ChainIndex, ResolveNullTipset},
};
use crate::interpreter::{
    BlockMessages, CalledAt, ExecutionContext, IMPLICIT_MESSAGE_GAS_LIMIT, VM, resolve_to_key_addr,
};
use crate::interpreter::{MessageCallbackCtx, VMTrace};
use crate::lotus_json::{LotusJson, lotus_json_with_self};
use crate::message::{ChainMessage, MessageRead as _, MessageReadWrite as _, SignedMessage};
use crate::networks::ChainConfig;
use crate::rpc::state::{ApiInvocResult, InvocResult, MessageGasCost};
use crate::rpc::types::{MiningBaseInfo, SectorOnChainInfo};
use crate::shim::actors::init::{self, State};
use crate::shim::actors::miner::{MinerInfo, MinerPower, Partition};
use crate::shim::actors::verifreg::{Allocation, AllocationID, Claim};
use crate::shim::actors::*;
use crate::shim::address::AddressId;
use crate::shim::crypto::{Signature, SignatureType};
use crate::shim::{
    actors::{
        LoadActorStateFromBlockstore, miner::ext::MinerStateExt as _,
        verifreg::ext::VerifiedRegistryStateExt as _,
    },
    executor::{ApplyRet, Receipt, StampedEvent},
};
use crate::shim::{
    address::{Address, Payload, Protocol},
    clock::ChainEpoch,
    econ::TokenAmount,
    machine::{GLOBAL_MULTI_ENGINE, MultiEngine},
    message::Message,
    randomness::Randomness,
    runtime::Policy,
    state_tree::{ActorState, StateTree},
    version::NetworkVersion,
};
use crate::state_manager::cache::TipsetStateCache;
use crate::state_manager::chain_rand::draw_randomness;
use crate::state_migration::run_state_migrations;
use crate::utils::ShallowClone as _;
use crate::utils::cache::SizeTrackingLruCache;
use crate::utils::get_size::{GetSize, vec_heap_size_helper};
use ahash::{HashMap, HashMapExt};
use anyhow::{Context as _, bail, ensure};
use bls_signatures::{PublicKey as BlsPublicKey, Serialize as _};
use chain_rand::ChainRand;
use cid::Cid;
pub use circulating_supply::GenesisInfo;
use fil_actor_verifreg_state::v12::DataCap;
use fil_actor_verifreg_state::v13::ClaimID;
use fil_actors_shared::fvm_ipld_amt::{Amt, Amtv0};
use fil_actors_shared::fvm_ipld_bitfield::BitField;
use fil_actors_shared::v12::runtime::DomainSeparationTag;
use futures::{FutureExt, channel::oneshot, select};
use fvm_ipld_blockstore::Blockstore;
use fvm_ipld_encoding::to_vec;
use fvm_shared4::crypto::signature::SECP_SIG_LEN;
use itertools::Itertools as _;
use nonzero_ext::nonzero;
use num::BigInt;
use num_traits::identities::Zero;
use schemars::JsonSchema;
use serde::{Deserialize, Serialize};
use std::ops::RangeInclusive;
use std::time::Duration;
use std::{num::NonZeroUsize, sync::Arc};
use tokio::sync::{RwLock, broadcast::error::RecvError};
use tracing::{error, info, instrument, warn};

const DEFAULT_TIPSET_CACHE_SIZE: NonZeroUsize = nonzero!(1024usize);
const DEFAULT_ID_TO_DETERMINISTIC_ADDRESS_CACHE_SIZE: NonZeroUsize = nonzero!(1024usize);
pub const EVENTS_AMT_BITWIDTH: u32 = 5;
pub type IdToAddressCache = SizeTrackingLruCache<AddressId, Address>;

/// Result of executing an individual chain message in a tipset.
///
/// Includes the executed message itself, the execution receipt, and
/// optional events emitted by the actor during execution.
#[derive(Debug, Clone)]
pub struct ExecutedMessage {
    pub message: ChainMessage,
    pub receipt: Receipt,
    pub events: Option<Vec<StampedEvent>>,
}

impl GetSize for ExecutedMessage {
    fn get_heap_size(&self) -> usize {
        self.message.get_heap_size()
            + self.receipt.get_heap_size()
            + self
                .events
                .as_ref()
                .map(vec_heap_size_helper)
                .unwrap_or_default()
    }
}

/// Aggregated execution result for a tipset.
#[derive(Debug, Clone, GetSize)]
pub struct ExecutedTipset {
    /// Resulting state tree root after message execution
    #[get_size(ignore)]
    pub state_root: Cid,
    /// Resulting message receipts root after message execution
    #[get_size(ignore)]
    pub receipt_root: Cid,
    /// Per-message execution details.
    /// Wrapped in an `Arc` to reduce cloning cost, as this can be quite large.
    pub executed_messages: Arc<Vec<ExecutedMessage>>,
}

/// Basic execution result for a tipset.
#[derive(Debug, Clone, GetSize)]
pub struct TipsetState {
    /// Resulting state tree root after message execution
    #[get_size(ignore)]
    pub state_root: Cid,
    /// Resulting message receipts root after message execution
    #[allow(dead_code)]
    #[get_size(ignore)]
    pub receipt_root: Cid,
}

impl From<ExecutedTipset> for TipsetState {
    fn from(
        ExecutedTipset {
            state_root,
            receipt_root,
            ..
        }: ExecutedTipset,
    ) -> Self {
        Self {
            state_root,
            receipt_root,
        }
    }
}

impl From<&ExecutedTipset> for TipsetState {
    fn from(
        ExecutedTipset {
            state_root,
            receipt_root,
            ..
        }: &ExecutedTipset,
    ) -> Self {
        Self {
            state_root: *state_root,
            receipt_root: *receipt_root,
        }
    }
}

/// External format for returning market balance from state.
#[derive(
    Debug, Default, Serialize, Deserialize, Clone, PartialEq, Eq, PartialOrd, Ord, JsonSchema,
)]
#[serde(rename_all = "PascalCase")]
pub struct MarketBalance {
    #[schemars(with = "LotusJson<TokenAmount>")]
    #[serde(with = "crate::lotus_json")]
    pub escrow: TokenAmount,
    #[schemars(with = "LotusJson<TokenAmount>")]
    #[serde(with = "crate::lotus_json")]
    pub locked: TokenAmount,
}
lotus_json_with_self!(MarketBalance);

/// State manager handles all interactions with the internal Filecoin actors
/// state. This encapsulates the [`ChainStore`] functionality, which only
/// handles chain data, to allow for interactions with the underlying state of
/// the chain. The state manager not only allows interfacing with state, but
/// also is used when performing state transitions.
pub struct StateManager<DB> {
    /// Chain store
    cs: Arc<ChainStore<DB>>,
    /// This is a cache which indexes tipsets to their calculated state output (state root, receipt root).
    cache: TipsetStateCache<ExecutedTipset>,
    id_to_deterministic_address_cache: IdToAddressCache,
    beacon: Arc<crate::beacon::BeaconSchedule>,
    engine: Arc<MultiEngine>,
}

#[allow(clippy::type_complexity)]
pub const NO_CALLBACK: Option<fn(MessageCallbackCtx<'_>) -> anyhow::Result<()>> = None;

impl<DB> StateManager<DB>
where
    DB: Blockstore,
{
    pub fn new(cs: Arc<ChainStore<DB>>) -> anyhow::Result<Self> {
        Self::new_with_engine(cs, GLOBAL_MULTI_ENGINE.clone())
    }

    pub fn new_with_engine(
        cs: Arc<ChainStore<DB>>,
        engine: Arc<MultiEngine>,
    ) -> anyhow::Result<Self> {
        let genesis = cs.genesis_block_header();
        let beacon = Arc::new(cs.chain_config().get_beacon_schedule(genesis.timestamp));

        Ok(Self {
            cs,
            cache: TipsetStateCache::new("executed_tipset"), // For StateOutput
            beacon,
            engine,
            id_to_deterministic_address_cache: SizeTrackingLruCache::new_with_metrics(
                "id_to_deterministic_address".into(),
                DEFAULT_ID_TO_DETERMINISTIC_ADDRESS_CACHE_SIZE,
            ),
        })
    }

    /// Returns the currently tracked heaviest tipset.
    pub fn heaviest_tipset(&self) -> Tipset {
        self.chain_store().heaviest_tipset()
    }

    /// Returns the currently tracked heaviest tipset and rewind to a most recent valid one if necessary.
    /// A valid head has
    ///     - state tree in the blockstore
    ///     - actor bundle version in the state tree that matches chain configuration
    pub fn maybe_rewind_heaviest_tipset(&self) -> anyhow::Result<()> {
        while self.maybe_rewind_heaviest_tipset_once()? {}
        Ok(())
    }

    fn maybe_rewind_heaviest_tipset_once(&self) -> anyhow::Result<bool> {
        let head = self.heaviest_tipset();
        if let Some(info) = self
            .chain_config()
            .network_height_with_actor_bundle(head.epoch())
        {
            let expected_height_info = info.info;
            let expected_bundle = info.manifest(self.blockstore())?;
            let expected_bundle_metadata = expected_bundle.metadata()?;
            let state = self.get_state_tree(head.parent_state())?;
            let bundle_metadata = state.get_actor_bundle_metadata()?;
            if expected_bundle_metadata != bundle_metadata {
                let current_epoch = head.epoch();
                let target_head = self.chain_index().tipset_by_height(
                    (expected_height_info.epoch - 1).max(0),
                    head,
                    ResolveNullTipset::TakeOlder,
                )?;
                let target_epoch = target_head.epoch();
                let bundle_version = &bundle_metadata.version;
                let expected_bundle_version = &expected_bundle_metadata.version;
                if target_epoch < current_epoch {
                    tracing::warn!(
                        "rewinding chain head from {current_epoch} to {target_epoch}, actor bundle: {bundle_version}, expected: {expected_bundle_version}"
                    );
                    if self.blockstore().has(target_head.parent_state())? {
                        self.chain_store().set_heaviest_tipset(target_head)?;
                        return Ok(true);
                    } else {
                        anyhow::bail!(
                            "failed to rewind, state tree @ {target_epoch} is missing from blockstore: {}",
                            target_head.parent_state()
                        );
                    }
                }
            }
        }
        Ok(false)
    }

    pub fn beacon_schedule(&self) -> &Arc<BeaconSchedule> {
        &self.beacon
    }

    /// Returns network version for the given epoch.
    pub fn get_network_version(&self, epoch: ChainEpoch) -> NetworkVersion {
        self.chain_config().network_version(epoch)
    }

    /// Gets the state tree
    pub fn get_state_tree(&self, state_cid: &Cid) -> anyhow::Result<StateTree<DB>> {
        StateTree::new_from_root(self.blockstore_owned(), state_cid)
    }

    /// Gets actor from given [`Cid`], if it exists.
    pub fn get_actor(&self, addr: &Address, state_cid: Cid) -> anyhow::Result<Option<ActorState>> {
        let state = self.get_state_tree(&state_cid)?;
        state.get_actor(addr)
    }

    /// Gets actor state from implicit actor address
    pub fn get_actor_state<S: LoadActorStateFromBlockstore>(
        &self,
        ts: &Tipset,
    ) -> anyhow::Result<S> {
        let state_tree = self.get_state_tree(ts.parent_state())?;
        state_tree.get_actor_state()
    }

    /// Gets actor state from explicit actor address
    pub fn get_actor_state_from_address<S: LoadActorStateFromBlockstore>(
        &self,
        ts: &Tipset,
        actor_address: &Address,
    ) -> anyhow::Result<S> {
        let state_tree = self.get_state_tree(ts.parent_state())?;
        state_tree.get_actor_state_from_address(actor_address)
    }

    /// Gets required actor from given [`Cid`].
    pub fn get_required_actor(&self, addr: &Address, state_cid: Cid) -> anyhow::Result<ActorState> {
        let state = self.get_state_tree(&state_cid)?;
        state.get_actor(addr)?.with_context(|| {
            format!("Failed to load actor with addr={addr}, state_cid={state_cid}")
        })
    }

    /// Returns a reference to the state manager's [`Blockstore`].
    pub fn blockstore(&self) -> &Arc<DB> {
        self.cs.blockstore()
    }

    pub fn blockstore_owned(&self) -> Arc<DB> {
        self.blockstore().clone()
    }

    /// Returns reference to the state manager's [`ChainStore`].
    pub fn chain_store(&self) -> &Arc<ChainStore<DB>> {
        &self.cs
    }

    /// Returns reference to the state manager's [`ChainIndex`].
    pub fn chain_index(&self) -> &ChainIndex<DB> {
        self.cs.chain_index()
    }

    /// Returns reference to the state manager's [`ChainConfig`].
    pub fn chain_config(&self) -> &Arc<ChainConfig> {
        self.cs.chain_config()
    }

    pub fn chain_rand(&self, tipset: Tipset) -> ChainRand<DB> {
        ChainRand::new(
            self.chain_config().shallow_clone(),
            tipset,
            self.chain_index().shallow_clone(),
            self.beacon.shallow_clone(),
        )
    }

    /// Returns the internal, protocol-level network chain from the state.
    pub fn get_network_state_name(
        &self,
        state_cid: Cid,
    ) -> anyhow::Result<crate::networks::StateNetworkName> {
        let init_act = self
            .get_actor(&init::ADDRESS.into(), state_cid)?
            .ok_or_else(|| Error::state("Init actor address could not be resolved"))?;
        Ok(
            State::load(self.blockstore(), init_act.code, init_act.state)?
                .into_network_name()
                .into(),
        )
    }

    /// Returns true if miner has been slashed or is considered invalid.
    pub fn is_miner_slashed(&self, addr: &Address, state_cid: &Cid) -> anyhow::Result<bool, Error> {
        let actor = self
            .get_actor(&Address::POWER_ACTOR, *state_cid)?
            .ok_or_else(|| Error::state("Power actor address could not be resolved"))?;

        let spas = power::State::load(self.blockstore(), actor.code, actor.state)?;

        Ok(spas.miner_power(self.blockstore(), addr)?.is_none())
    }

    /// Returns raw work address of a miner given the state root.
    pub fn get_miner_work_addr(&self, state_cid: Cid, addr: &Address) -> Result<Address, Error> {
        let state =
            StateTree::new_from_root(self.blockstore_owned(), &state_cid).map_err(Error::other)?;
        let ms: miner::State = state.get_actor_state_from_address(addr)?;
        let info = ms.info(self.blockstore()).map_err(|e| e.to_string())?;
        let addr = resolve_to_key_addr(&state, self.blockstore(), &info.worker())?;
        Ok(addr)
    }

    /// Returns specified actor's claimed power and total network power as a
    /// tuple.
    pub fn get_power(
        &self,
        state_cid: &Cid,
        addr: Option<&Address>,
    ) -> anyhow::Result<Option<(power::Claim, power::Claim)>, Error> {
        let actor = self
            .get_actor(&Address::POWER_ACTOR, *state_cid)?
            .ok_or_else(|| Error::state("Power actor address could not be resolved"))?;

        let spas = power::State::load(self.blockstore(), actor.code, actor.state)?;

        let t_pow = spas.total_power();

        if let Some(maddr) = addr {
            let m_pow = spas
                .miner_power(self.blockstore(), maddr)?
                .ok_or_else(|| Error::state(format!("Miner for address {maddr} not found")))?;

            let min_pow = spas.miner_nominal_power_meets_consensus_minimum(
                &self.chain_config().policy,
                self.blockstore(),
                maddr,
            )?;
            if min_pow {
                return Ok(Some((m_pow, t_pow)));
            }
        }

        Ok(None)
    }

    // Returns all sectors
    pub fn get_all_sectors(
        &self,
        addr: &Address,
        ts: &Tipset,
    ) -> anyhow::Result<Vec<SectorOnChainInfo>> {
        let actor = self
            .get_actor(addr, *ts.parent_state())?
            .ok_or_else(|| Error::state("Miner actor not found"))?;
        let state = miner::State::load(self.blockstore(), actor.code, actor.state)?;
        state.load_sectors_ext(self.blockstore(), None)
    }
}

impl<DB> StateManager<DB>
where
    DB: Blockstore + Send + Sync + 'static,
{
    /// Load the state of a tipset, including state root, message receipts
    pub async fn load_tipset_state(self: &Arc<Self>, ts: &Tipset) -> anyhow::Result<TipsetState> {
        if let Some(state) = self.cache.get_map(ts.key(), |et| et.into()) {
            Ok(state)
        } else if let Ok(receipt_ts) = self.chain_store().load_child_tipset(ts) {
            Ok(TipsetState {
                state_root: *receipt_ts.parent_state(),
                receipt_root: *receipt_ts.parent_message_receipts(),
            })
        } else {
            Ok(self.load_executed_tipset(ts).await?.into())
        }
    }

    /// Load an executed tipset, including state root, message receipts and events with caching.
    pub async fn load_executed_tipset(
        self: &Arc<Self>,
        ts: &Tipset,
    ) -> anyhow::Result<ExecutedTipset> {
        // validate the existence of state trees for post-chain-head-epoch tipsets in case chain head is reset(e.g. manually or via GC).
        if ts.epoch() >= self.heaviest_tipset().epoch()
            && let Some(cached) = self.cache.get(ts.key())
        {
            if StateTree::new_from_root(self.blockstore_owned(), &cached.state_root).is_ok() {
                return Ok(cached);
            } else {
                self.cache.remove(ts.key());
            }
        }
        self.cache
            .get_or_else(ts.key(), || async move {
                let receipt_ts = self.chain_store().load_child_tipset(ts).ok();
                self.load_executed_tipset_inner(ts, receipt_ts.as_ref())
                    .await
            })
            .await
    }

    async fn load_executed_tipset_inner(
        self: &Arc<Self>,
        msg_ts: &Tipset,
        // when `msg_ts` is the current head, `receipt_ts` is `None`
        receipt_ts: Option<&Tipset>,
    ) -> anyhow::Result<ExecutedTipset> {
        if let Some(receipt_ts) = receipt_ts {
            anyhow::ensure!(
                msg_ts.key() == receipt_ts.parents(),
                "message tipset should be the parent of message receipt tipset"
            );
        }
        let mut recomputed = false;
        let (state_root, receipt_root, receipts) = match receipt_ts.and_then(|ts| {
            let receipt_root = *ts.parent_message_receipts();
            Receipt::get_receipts(self.cs.blockstore(), receipt_root)
                .ok()
                .map(|r| (*ts.parent_state(), receipt_root, r))
        }) {
            Some((state_root, receipt_root, receipts)) => (state_root, receipt_root, receipts),
            None => {
                let state_output = self
                    .compute_tipset_state(msg_ts.shallow_clone(), NO_CALLBACK, VMTrace::NotTraced)
                    .await?;
                recomputed = true;
                (
                    state_output.state_root,
                    state_output.receipt_root,
                    Receipt::get_receipts(self.cs.blockstore(), state_output.receipt_root)?,
                )
            }
        };

        let messages = self.chain_store().messages_for_tipset(msg_ts)?;
        anyhow::ensure!(
            messages.len() == receipts.len(),
            "mismatching message and receipt counts ({} messages, {} receipts)",
            messages.len(),
            receipts.len()
        );
        let mut executed_messages = Vec::with_capacity(messages.len());
        for (message, receipt) in messages.iter().cloned().zip(receipts) {
            let events = if let Some(events_root) = receipt.events_root() {
                Some(
                    match StampedEvent::get_events(self.cs.blockstore(), &events_root) {
                        Ok(events) => events,
                        Err(e) if recomputed => return Err(e),
                        Err(_) => {
                            self.compute_tipset_state(
                                msg_ts.shallow_clone(),
                                NO_CALLBACK,
                                VMTrace::NotTraced,
                            )
                            .await?;
                            recomputed = true;
                            StampedEvent::get_events(self.cs.blockstore(), &events_root)?
                        }
                    },
                )
            } else {
                None
            };
            executed_messages.push(ExecutedMessage {
                message,
                receipt,
                events,
            });
        }
        Ok(ExecutedTipset {
            state_root,
            receipt_root,
            executed_messages: Arc::new(executed_messages),
        })
    }

    #[instrument(skip(self, rand))]
    fn call_raw(
        &self,
        state_cid: Option<Cid>,
        msg: &Message,
        rand: ChainRand<DB>,
        tipset: &Tipset,
    ) -> Result<ApiInvocResult, Error> {
        let mut msg = msg.clone();

        let state_cid = state_cid.unwrap_or(*tipset.parent_state());

        let tipset_messages = self
            .chain_store()
            .messages_for_tipset(tipset)
            .map_err(|err| Error::Other(err.to_string()))?;

        let prior_messsages = tipset_messages
            .iter()
            .filter(|ts_msg| ts_msg.message().from() == msg.from());

        // Handle state forks

        let height = tipset.epoch();
        let genesis_info = GenesisInfo::from_chain_config(self.chain_config().clone());
        let mut vm = VM::new(
            ExecutionContext {
                heaviest_tipset: tipset.shallow_clone(),
                state_tree_root: state_cid,
                epoch: height,
                rand: Box::new(rand),
                base_fee: tipset.block_headers().first().parent_base_fee.clone(),
                circ_supply: genesis_info.get_vm_circulating_supply(
                    height,
                    self.blockstore(),
                    &state_cid,
                )?,
                chain_config: self.chain_config().shallow_clone(),
                chain_index: self.chain_index().shallow_clone(),
                timestamp: tipset.min_timestamp(),
            },
            &self.engine,
            VMTrace::Traced,
        )?;

        for m in prior_messsages {
            vm.apply_message(m)?;
        }

        // We flush to get the VM's view of the state tree after applying the above messages
        // This is needed to get the correct nonce from the actor state to match the VM
        let state_cid = vm.flush()?;

        let state = StateTree::new_from_root(self.blockstore_owned(), &state_cid)?;

        let from_actor = state
            .get_actor(&msg.from())?
            .ok_or_else(|| anyhow::anyhow!("actor not found"))?;
        msg.set_sequence(from_actor.sequence);

        // Implicit messages need to set a special gas limit
        let mut msg = msg.clone();
        msg.gas_limit = IMPLICIT_MESSAGE_GAS_LIMIT as u64;

        let (apply_ret, duration) = vm.apply_implicit_message(&msg)?;

        Ok(ApiInvocResult {
            msg: msg.clone(),
            msg_rct: Some(apply_ret.msg_receipt()),
            msg_cid: msg.cid(),
            error: apply_ret.failure_info().unwrap_or_default(),
            duration: duration.as_nanos().clamp(0, u128::from(u64::MAX)) as u64,
            gas_cost: MessageGasCost::default(),
            execution_trace: structured::parse_events(apply_ret.exec_trace()).unwrap_or_default(),
        })
    }

    /// runs the given message and returns its result without any persisted
    /// changes.
    pub fn call(&self, message: &Message, tipset: Option<Tipset>) -> Result<ApiInvocResult, Error> {
        let ts = tipset.unwrap_or_else(|| self.heaviest_tipset());
        let chain_rand = self.chain_rand(ts.shallow_clone());
        self.call_raw(None, message, chain_rand, &ts)
    }

    /// Same as [`StateManager::call`] but runs the message on the given state and not
    /// on the parent state of the tipset.
    pub fn call_on_state(
        &self,
        state_cid: Cid,
        message: &Message,
        tipset: Option<Tipset>,
    ) -> Result<ApiInvocResult, Error> {
        let ts = tipset.unwrap_or_else(|| self.cs.heaviest_tipset());
        let chain_rand = self.chain_rand(ts.shallow_clone());
        self.call_raw(Some(state_cid), message, chain_rand, &ts)
    }

    pub async fn apply_on_state_with_gas(
        self: &Arc<Self>,
        tipset: Option<Tipset>,
        msg: Message,
        vm_flush: VMFlush,
    ) -> anyhow::Result<(ApiInvocResult, Option<Cid>)> {
        let ts = tipset.unwrap_or_else(|| self.heaviest_tipset());

        let from_a = self.resolve_to_key_addr(&msg.from, &ts).await?;

        // Pretend that the message is signed. This has an influence on the gas
        // cost. We obviously can't generate a valid signature. Instead, we just
        // fill the signature with zeros. The validity is not checked.
        let mut chain_msg = match from_a.protocol() {
            Protocol::Secp256k1 => SignedMessage::new_unchecked(
                msg.clone(),
                Signature::new_secp256k1(vec![0; SECP_SIG_LEN]),
            )
            .into(),
            Protocol::Delegated => SignedMessage::new_unchecked(
                msg.clone(),
                // In Lotus, delegated signatures have the same length as SECP256k1.
                // This may or may not change in the future.
                Signature::new(SignatureType::Delegated, vec![0; SECP_SIG_LEN]),
            )
            .into(),
            _ => msg.clone().into(),
        };

        let (_invoc_res, apply_ret, duration, state_root) = self
            .call_with_gas(&mut chain_msg, &[], Some(ts), vm_flush)
            .await?;

        Ok((
            ApiInvocResult {
                msg_cid: msg.cid(),
                msg,
                msg_rct: Some(apply_ret.msg_receipt()),
                error: apply_ret.failure_info().unwrap_or_default(),
                duration: duration.as_nanos().clamp(0, u128::from(u64::MAX)) as u64,
                gas_cost: MessageGasCost::default(),
                execution_trace: structured::parse_events(apply_ret.exec_trace())
                    .unwrap_or_default(),
            },
            state_root,
        ))
    }

    /// Computes message on the given [Tipset] state, after applying other
    /// messages and returns the values computed in the VM.
    pub async fn call_with_gas(
        self: &Arc<Self>,
        message: &mut ChainMessage,
        prior_messages: &[ChainMessage],
        tipset: Option<Tipset>,
        vm_flush: VMFlush,
    ) -> Result<(InvocResult, ApplyRet, Duration, Option<Cid>), Error> {
        let ts = tipset.unwrap_or_else(|| self.heaviest_tipset());
        let TipsetState { state_root, .. } = self
            .load_tipset_state(&ts)
            .await
            .map_err(|e| Error::Other(format!("Could not load tipset state: {e:#}")))?;
        let chain_rand = self.chain_rand(ts.clone());

        // Since we're simulating a future message, pretend we're applying it in the
        // "next" tipset
        let epoch = ts.epoch() + 1;
        let genesis_info = GenesisInfo::from_chain_config(self.chain_config().clone());
        // FVM requires a stack size of 64MiB. The alternative is to use `ThreadedExecutor` from
        // FVM, but that introduces some constraints, and possible deadlocks.
        let (ret, duration, state_cid) = stacker::grow(64 << 20, || -> anyhow::Result<_> {
            let mut vm = VM::new(
                ExecutionContext {
                    heaviest_tipset: ts.clone(),
                    state_tree_root: state_root,
                    epoch,
                    rand: Box::new(chain_rand),
                    base_fee: ts.block_headers().first().parent_base_fee.clone(),
                    circ_supply: genesis_info.get_vm_circulating_supply(
                        epoch,
                        self.blockstore(),
                        &state_root,
                    )?,
                    chain_config: self.chain_config().shallow_clone(),
                    chain_index: self.chain_index().shallow_clone(),
                    timestamp: ts.min_timestamp(),
                },
                &self.engine,
                VMTrace::NotTraced,
            )?;

            for msg in prior_messages {
                vm.apply_message(msg)?;
            }
            let from_actor = vm
                .get_actor(&message.from())
                .map_err(|e| Error::Other(format!("Could not get actor from state: {e:#}")))?
                .ok_or_else(|| Error::Other("cant find actor in state tree".to_string()))?;

            message.set_sequence(from_actor.sequence);
            let (ret, duration) = vm.apply_message(message)?;
            let state_root = match vm_flush {
                VMFlush::Flush => Some(vm.flush()?),
                VMFlush::Skip => None,
            };
            Ok((ret, duration, state_root))
        })?;

        Ok((
            InvocResult::new(message.message().clone(), &ret),
            ret,
            duration,
            state_cid,
        ))
    }

    /// Replays the given message and returns the result of executing the
    /// indicated message, assuming it was executed in the indicated tipset.
    pub async fn replay(self: &Arc<Self>, ts: Tipset, mcid: Cid) -> Result<ApiInvocResult, Error> {
        let this = Arc::clone(self);
        tokio::task::spawn_blocking(move || this.replay_blocking(ts, mcid)).await?
    }

    /// Blocking version of `replay`
    pub fn replay_blocking(
        self: &Arc<Self>,
        ts: Tipset,
        mcid: Cid,
    ) -> Result<ApiInvocResult, Error> {
        const REPLAY_HALT: &str = "replay_halt";

        let mut api_invoc_result = None;
        let callback = |ctx: MessageCallbackCtx<'_>| {
            match ctx.at {
                CalledAt::Applied | CalledAt::Reward
                    if api_invoc_result.is_none() && ctx.cid == mcid =>
                {
                    api_invoc_result = Some(ApiInvocResult {
                        msg_cid: ctx.message.cid(),
                        msg: ctx.message.message().clone(),
                        msg_rct: Some(ctx.apply_ret.msg_receipt()),
                        error: ctx.apply_ret.failure_info().unwrap_or_default(),
                        duration: ctx.duration.as_nanos().clamp(0, u128::from(u64::MAX)) as u64,
                        gas_cost: MessageGasCost::new(ctx.message.message(), ctx.apply_ret)?,
                        execution_trace: structured::parse_events(ctx.apply_ret.exec_trace())
                            .unwrap_or_default(),
                    });
                    anyhow::bail!(REPLAY_HALT);
                }
                _ => Ok(()), // ignored
            }
        };
        let result = self.compute_tipset_state_blocking(ts, Some(callback), VMTrace::Traced);
        if let Err(error_message) = result
            && error_message.to_string() != REPLAY_HALT
        {
            return Err(Error::Other(format!(
                "unexpected error during execution : {error_message:}"
            )));
        }
        api_invoc_result.ok_or_else(|| Error::Other("failed to replay".into()))
    }

    /// Replays a tipset up to a target message, capturing the state root before
    /// and after execution.
    pub async fn replay_for_prestate(
        self: &Arc<Self>,
        ts: Tipset,
        target_message_cid: Cid,
    ) -> Result<(Cid, ApiInvocResult, Cid), Error> {
        let this = Arc::clone(self);
        tokio::task::spawn_blocking(move || {
            this.replay_for_prestate_blocking(ts, target_message_cid)
        })
        .await
        .map_err(|e| Error::Other(format!("{e}")))?
    }

    fn replay_for_prestate_blocking(
        self: &Arc<Self>,
        ts: Tipset,
        target_msg_cid: Cid,
    ) -> Result<(Cid, ApiInvocResult, Cid), Error> {
        if ts.epoch() == 0 {
            return Err(Error::Other(
                "cannot trace messages in the genesis block".into(),
            ));
        }

        let genesis_timestamp = self.chain_store().genesis_block_header().timestamp;
        let exec = TipsetExecutor::new(
            self.chain_index().shallow_clone(),
            self.chain_config().shallow_clone(),
            self.beacon_schedule().shallow_clone(),
            &self.engine,
            ts.shallow_clone(),
        );
        let mut no_cb = NO_CALLBACK;
        let (parent_state, epoch, block_messages) =
            exec.prepare_parent_state(genesis_timestamp, VMTrace::NotTraced, &mut no_cb)?;

        Ok(stacker::grow(64 << 20, || {
            let mut vm =
                exec.create_vm(parent_state, epoch, ts.min_timestamp(), VMTrace::NotTraced)?;
            let mut processed = ahash::HashSet::default();

            for block in block_messages.iter() {
                let mut penalty = TokenAmount::zero();
                let mut gas_reward = TokenAmount::zero();

                for msg in block.messages.iter() {
                    let cid = msg.cid();
                    if processed.contains(&cid) {
                        continue;
                    }

                    processed.insert(cid);

                    if cid == target_msg_cid {
                        let pre_root = vm.flush()?;
                        let mut traced_vm =
                            exec.create_vm(pre_root, epoch, ts.min_timestamp(), VMTrace::Traced)?;
                        let (ret, duration) = traced_vm.apply_message(msg)?;
                        let post_root = traced_vm.flush()?;

                        return Ok((
                            pre_root,
                            ApiInvocResult {
                                msg_cid: cid,
                                msg: msg.message().clone(),
                                msg_rct: Some(ret.msg_receipt()),
                                error: ret.failure_info().unwrap_or_default(),
                                duration: duration.as_nanos().clamp(0, u128::from(u64::MAX)) as u64,
                                gas_cost: MessageGasCost::default(),
                                execution_trace: structured::parse_events(ret.exec_trace())
                                    .unwrap_or_default(),
                            },
                            post_root,
                        ));
                    }

                    let (ret, _) = vm.apply_message(msg)?;
                    gas_reward += ret.miner_tip();
                    penalty += ret.penalty();
                }

                if let Some(rew_msg) =
                    vm.reward_message(epoch, block.miner, block.win_count, penalty, gas_reward)?
                {
                    let (ret, _) = vm.apply_implicit_message(&rew_msg)?;
                    if let Some(err) = ret.failure_info() {
                        bail!(
                            "failed to apply reward message for miner {}: {err}",
                            block.miner
                        );
                    }

                    // This is more of a sanity check, this should not be able to be hit.
                    if !ret.msg_receipt().exit_code().is_success() {
                        bail!(
                            "reward application message failed (exit: {:?})",
                            ret.msg_receipt().exit_code()
                        );
                    }
                }
            }

            bail!("message {target_msg_cid} not found in tipset")
        })?)
    }

    /// Checks the eligibility of the miner. This is used in the validation that
    /// a block's miner has the requirements to mine a block.
    pub fn eligible_to_mine(
        &self,
        address: &Address,
        base_tipset: &Tipset,
        lookback_tipset: &Tipset,
    ) -> anyhow::Result<bool, Error> {
        let hmp =
            self.miner_has_min_power(&self.chain_config().policy, address, lookback_tipset)?;
        let version = self.get_network_version(base_tipset.epoch());

        if version <= NetworkVersion::V3 {
            return Ok(hmp);
        }

        if !hmp {
            return Ok(false);
        }

        let actor = self
            .get_actor(&Address::POWER_ACTOR, *base_tipset.parent_state())?
            .ok_or_else(|| Error::state("Power actor address could not be resolved"))?;

        let power_state = power::State::load(self.blockstore(), actor.code, actor.state)?;

        let actor = self
            .get_actor(address, *base_tipset.parent_state())?
            .ok_or_else(|| Error::state("Miner actor address could not be resolved"))?;

        let miner_state = miner::State::load(self.blockstore(), actor.code, actor.state)?;

        // Non-empty power claim.
        let claim = power_state
            .miner_power(self.blockstore(), address)?
            .ok_or_else(|| Error::Other("Could not get claim".to_string()))?;
        if claim.quality_adj_power <= BigInt::zero() {
            return Ok(false);
        }

        // No fee debt.
        if !miner_state.fee_debt().is_zero() {
            return Ok(false);
        }

        // No active consensus faults.
        let info = miner_state.info(self.blockstore())?;
        if base_tipset.epoch() <= info.consensus_fault_elapsed {
            return Ok(false);
        }

        Ok(true)
    }

    /// Conceptually, a [`Tipset`] consists of _blocks_ which share an _epoch_.
    /// Each _block_ contains _messages_, which are executed by the _Filecoin Virtual Machine_.
    ///
    /// VM message execution essentially looks like this:
    /// ```text
    /// state[N-900..N] * message = state[N+1]
    /// ```
    ///
    /// The `state`s above are stored in the `IPLD Blockstore`, and can be referred to by
    /// a [`Cid`] - the _state root_.
    /// The previous 900 states (configurable, see
    /// <https://docs.filecoin.io/reference/general/glossary/#finality>) can be
    /// queried when executing a message, so a store needs at least that many.
    /// (a snapshot typically contains 2000, for example).
    ///
    /// Each message costs FIL to execute - this is _gas_.
    /// After execution, the message has a _receipt_, showing how much gas was spent.
    /// This is similarly a [`Cid`] into the block store.
    ///
    /// For details, see the documentation for [`apply_block_messages`].
    ///
    pub async fn compute_tipset_state(
        self: &Arc<Self>,
        tipset: Tipset,
        callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()> + Send + 'static>,
        enable_tracing: VMTrace,
    ) -> Result<ExecutedTipset, Error> {
        let this = Arc::clone(self);
        tokio::task::spawn_blocking(move || {
            this.compute_tipset_state_blocking(tipset, callback, enable_tracing)
        })
        .await?
    }

    /// Blocking version of `compute_tipset_state`
    pub fn compute_tipset_state_blocking(
        &self,
        tipset: Tipset,
        callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()>>,
        enable_tracing: VMTrace,
    ) -> Result<ExecutedTipset, Error> {
        let epoch = tipset.epoch();
        let has_callback = callback.is_some();
        info!(
            "Evaluating tipset: EPOCH={epoch}, blocks={}, tsk={}",
            tipset.len(),
            tipset.key(),
        );
        Ok(apply_block_messages(
            self.chain_store().genesis_block_header().timestamp,
            self.chain_index().shallow_clone(),
            self.chain_config().shallow_clone(),
            self.beacon_schedule().shallow_clone(),
            &self.engine,
            tipset,
            callback,
            enable_tracing,
        )
        .map_err(|e| {
            if has_callback {
                e
            } else {
                e.context(format!("Failed to compute tipset state@{epoch}"))
            }
        })?)
    }

    #[instrument(skip_all)]
    pub async fn compute_state(
        self: &Arc<Self>,
        height: ChainEpoch,
        messages: Vec<Message>,
        tipset: Tipset,
        callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()> + Send + 'static>,
        enable_tracing: VMTrace,
    ) -> Result<ExecutedTipset, Error> {
        let this = Arc::clone(self);
        tokio::task::spawn_blocking(move || {
            this.compute_state_blocking(height, messages, tipset, callback, enable_tracing)
        })
        .await?
    }

    /// Blocking version of `compute_state`
    #[tracing::instrument(skip_all)]
    pub fn compute_state_blocking(
        &self,
        height: ChainEpoch,
        messages: Vec<Message>,
        tipset: Tipset,
        callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()>>,
        enable_tracing: VMTrace,
    ) -> Result<ExecutedTipset, Error> {
        Ok(compute_state(
            height,
            messages,
            tipset,
            self.chain_store().genesis_block_header().timestamp,
            self.chain_index().shallow_clone(),
            self.chain_config().shallow_clone(),
            self.beacon_schedule().shallow_clone(),
            &self.engine,
            callback,
            enable_tracing,
        )?)
    }

    /// Check if tipset had executed the message, by loading the receipt based
    /// on the index of the message in the block.
    fn tipset_executed_message(
        &self,
        tipset: &Tipset,
        message: &ChainMessage,
        allow_replaced: bool,
    ) -> Result<Option<Receipt>, Error> {
        if tipset.epoch() == 0 {
            return Ok(None);
        }
        let message_from_address = message.from();
        let message_sequence = message.sequence();
        // Load parent state.
        let pts = self
            .chain_index()
            .load_required_tipset(tipset.parents())
            .map_err(|err| Error::Other(format!("Failed to load tipset: {err}")))?;
        let messages = self
            .cs
            .messages_for_tipset(&pts)
            .map_err(|err| Error::Other(format!("Failed to load messages for tipset: {err}")))?;
        messages
            .iter()
            .enumerate()
            // iterate in reverse because we going backwards through the chain
            .rev()
            .filter(|(_, s)| {
                s.sequence() == message_sequence
                    && s.from() == message_from_address
                    && s.equal_call(message)
            })
            .map(|(index, m)| {
                // A replacing message is a message with a different CID,
                // any of Gas values, and different signature, but with all
                // other parameters matching (source/destination, nonce, params, etc.)
                if !allow_replaced && message.cid() != m.cid(){
                    Err(Error::Other(format!(
                        "found message with equal nonce and call params but different CID. wanted {}, found: {}, nonce: {}, from: {}",
                        message.cid(),
                        m.cid(),
                        message.sequence(),
                        message.from(),
                    )))
                } else {
                    let block_header = tipset.block_headers().first();
                    crate::chain::get_parent_receipt(
                        self.blockstore(),
                        block_header,
                        index,
                    )
                    .map_err(|err| Error::Other(format!("Failed to get parent receipt (message_receipts={}, index={index}, error={err})", block_header.message_receipts)))
                }
            })
            .next()
            .unwrap_or(Ok(None))
    }

    fn check_search(
        &self,
        mut current: Tipset,
        message: &ChainMessage,
        lookback_max_epoch: ChainEpoch,
        allow_replaced: bool,
    ) -> Result<Option<(Tipset, Receipt)>, Error> {
        let message_from_address = message.from();
        let message_sequence = message.sequence();
        let mut current_actor_state = self
            .get_required_actor(&message_from_address, *current.parent_state())
            .map_err(Error::state)?;
        let message_from_id = self.lookup_required_id(&message_from_address, &current)?;

        while current.epoch() >= lookback_max_epoch {
            let parent_tipset = self
                .chain_index()
                .load_required_tipset(current.parents())
                .map_err(|err| {
                    Error::Other(format!(
                        "failed to load tipset during msg wait searchback: {err:}"
                    ))
                })?;

            let parent_actor_state = self
                .get_actor(&message_from_id, *parent_tipset.parent_state())
                .map_err(|e| Error::State(e.to_string()))?;

            if parent_actor_state.is_none()
                || (current_actor_state.sequence > message_sequence
                    && parent_actor_state.as_ref().unwrap().sequence <= message_sequence)
            {
                let receipt = self
                    .tipset_executed_message(&current, message, allow_replaced)?
                    .context("Failed to get receipt with tipset_executed_message")?;
                return Ok(Some((current, receipt)));
            }

            if let Some(parent_actor_state) = parent_actor_state {
                current = parent_tipset;
                current_actor_state = parent_actor_state;
            } else {
                break;
            }
        }

        Ok(None)
    }

    /// Searches backwards through the chain for a message receipt.
    fn search_back_for_message(
        &self,
        current: Tipset,
        message: &ChainMessage,
        look_back_limit: Option<i64>,
        allow_replaced: Option<bool>,
    ) -> Result<Option<(Tipset, Receipt)>, Error> {
        let current_epoch = current.epoch();
        let allow_replaced = allow_replaced.unwrap_or(true);

        // Calculate the max lookback epoch (inclusive lower bound) for the search.
        let lookback_max_epoch = match look_back_limit {
            // No search: limit = 0 means search 0 epochs
            Some(0) => return Ok(None),
            // Limited search: calculate the inclusive lower bound, clamped to genesis
            // Example: limit=5 at epoch=1000 → min_epoch=996, searches [996,1000] = 5 epochs
            // Example: limit=2000 at epoch=1000 → min_epoch=0, searches [0,1000] = 1001 epochs (all available)
            Some(limit) if limit > 0 => (current_epoch - limit + 1).max(0),
            // Search all the way to genesis (epoch 0)
            _ => 0,
        };

        self.check_search(current, message, lookback_max_epoch, allow_replaced)
    }

    /// Returns a message receipt from a given tipset and message CID.
    pub fn get_receipt(&self, tipset: Tipset, msg: Cid) -> Result<Receipt, Error> {
        let m = crate::chain::get_chain_message(self.blockstore(), &msg)
            .map_err(|e| Error::Other(e.to_string()))?;
        let message_receipt = self.tipset_executed_message(&tipset, &m, true)?;
        if let Some(receipt) = message_receipt {
            return Ok(receipt);
        }

        let maybe_tuple = self.search_back_for_message(tipset, &m, None, None)?;
        let message_receipt = maybe_tuple
            .ok_or_else(|| {
                Error::Other("Could not get receipt from search back message".to_string())
            })?
            .1;
        Ok(message_receipt)
    }

    /// `WaitForMessage` blocks until a message appears on chain. It looks
    /// backwards in the chain to see if this has already happened. It
    /// guarantees that the message has been on chain for at least
    /// confidence epochs without being reverted before returning.
    pub async fn wait_for_message(
        self: &Arc<Self>,
        msg_cid: Cid,
        confidence: i64,
        look_back_limit: Option<ChainEpoch>,
        allow_replaced: Option<bool>,
    ) -> Result<(Option<Tipset>, Option<Receipt>), Error> {
        let mut head_changes_rx = self.cs.subscribe_head_changes();
        let (sender, mut receiver) = oneshot::channel::<()>();
        let message = crate::chain::get_chain_message(self.blockstore(), &msg_cid)
            .map_err(|err| Error::Other(format!("failed to load message {err:}")))?;
        let current_tipset = self.heaviest_tipset();
        let maybe_message_receipt =
            self.tipset_executed_message(&current_tipset, &message, true)?;
        if let Some(r) = maybe_message_receipt {
            return Ok((Some(current_tipset.shallow_clone()), Some(r)));
        }

        let mut candidate_tipset: Option<Tipset> = None;
        let mut candidate_receipt: Option<Receipt> = None;

        let sm_cloned = self.shallow_clone();

        let message_for_task = message.clone();
        let height_of_head = current_tipset.epoch();
        let task = tokio::task::spawn(async move {
            let back_tuple = sm_cloned.search_back_for_message(
                current_tipset,
                &message_for_task,
                look_back_limit,
                allow_replaced,
            )?;
            sender
                .send(())
                .map_err(|e| Error::Other(format!("Could not send to channel {e:?}")))?;
            Ok::<_, Error>(back_tuple)
        });

        let reverts: Arc<RwLock<HashMap<TipsetKey, bool>>> = Arc::new(RwLock::new(HashMap::new()));
        let block_revert = reverts.clone();
        let sm_cloned = Arc::clone(self);

        // Wait for message to be included in head change.
        let mut subscriber_poll = tokio::task::spawn(async move {
            loop {
                match head_changes_rx.recv().await {
                    Ok(head_changes) => {
                        for tipset in head_changes.reverts {
                            if candidate_tipset
                                .as_ref()
                                .is_some_and(|candidate| candidate.key() == tipset.key())
                            {
                                candidate_tipset = None;
                                candidate_receipt = None;
                            }
                        }
                        for tipset in head_changes.applies {
                            if candidate_tipset
                                .as_ref()
                                .map(|s| tipset.epoch() >= s.epoch() + confidence)
                                .unwrap_or_default()
                            {
                                return Ok((candidate_tipset, candidate_receipt));
                            }
                            let poll_receiver = receiver.try_recv();
                            if let Ok(Some(_)) = poll_receiver {
                                block_revert
                                    .write()
                                    .await
                                    .insert(tipset.key().to_owned(), true);
                            }

                            let maybe_receipt =
                                sm_cloned.tipset_executed_message(&tipset, &message, true)?;
                            if let Some(receipt) = maybe_receipt {
                                if confidence == 0 {
                                    return Ok((Some(tipset), Some(receipt)));
                                }
                                candidate_tipset = Some(tipset);
                                candidate_receipt = Some(receipt)
                            }
                        }
                    }
                    Err(RecvError::Lagged(i)) => {
                        warn!(
                            "wait for message head change subscriber lagged, skipped {} events",
                            i
                        );
                    }
                    Err(RecvError::Closed) => break,
                }
            }
            Ok((None, None))
        })
        .fuse();

        // Search backwards for message.
        let mut search_back_poll = tokio::task::spawn(async move {
            let back_tuple = task.await.map_err(|e| {
                Error::Other(format!("Could not search backwards for message {e}"))
            })??;
            if let Some((back_tipset, back_receipt)) = back_tuple {
                let should_revert = *reverts
                    .read()
                    .await
                    .get(back_tipset.key())
                    .unwrap_or(&false);
                let larger_height_of_head = height_of_head >= back_tipset.epoch() + confidence;
                if !should_revert && larger_height_of_head {
                    return Ok::<_, Error>((Some(back_tipset), Some(back_receipt)));
                }
                return Ok((None, None));
            }
            Ok((None, None))
        })
        .fuse();

        // Await on first future to finish.
        loop {
            select! {
                res = subscriber_poll => {
                    return res?
                }
                res = search_back_poll => {
                    if let Ok((Some(ts), Some(rct))) = res? {
                        return Ok((Some(ts), Some(rct)));
                    }
                }
            }
        }
    }

    pub async fn search_for_message(
        &self,
        from: Option<Tipset>,
        msg_cid: Cid,
        look_back_limit: Option<i64>,
        allow_replaced: Option<bool>,
    ) -> Result<Option<(Tipset, Receipt)>, Error> {
        let from = from.unwrap_or_else(|| self.heaviest_tipset());
        let message = crate::chain::get_chain_message(self.blockstore(), &msg_cid)
            .map_err(|err| Error::Other(format!("failed to load message {err}")))?;
        let current_tipset = self.heaviest_tipset();
        let maybe_message_receipt =
            self.tipset_executed_message(&from, &message, allow_replaced.unwrap_or(true))?;
        if let Some(r) = maybe_message_receipt {
            Ok(Some((from, r)))
        } else {
            self.search_back_for_message(current_tipset, &message, look_back_limit, allow_replaced)
        }
    }

    /// Returns a BLS public key from provided address
    pub fn get_bls_public_key(
        db: &Arc<DB>,
        addr: &Address,
        state_cid: Cid,
    ) -> Result<BlsPublicKey, Error> {
        let state = StateTree::new_from_root(Arc::clone(db), &state_cid)
            .map_err(|e| Error::Other(e.to_string()))?;
        let kaddr =
            resolve_to_key_addr(&state, db, addr).context("Failed to resolve key address")?;

        match kaddr.into_payload() {
            Payload::BLS(key) => BlsPublicKey::from_bytes(&key)
                .context("Failed to construct bls public key")
                .map_err(Error::from),
            _ => Err(Error::state(
                "Address must be BLS address to load bls public key",
            )),
        }
    }

    /// Looks up ID [Address] from the state at the given [Tipset].
    pub fn lookup_id(&self, addr: &Address, ts: &Tipset) -> Result<Option<Address>, Error> {
        let state_tree = StateTree::new_from_root(self.blockstore_owned(), ts.parent_state())
            .map_err(|e| format!("{e:?}"))?;
        Ok(state_tree
            .lookup_id(addr)
            .map_err(|e| Error::Other(e.to_string()))?
            .map(Address::new_id))
    }

    /// Looks up required ID [Address] from the state at the given [Tipset].
    pub fn lookup_required_id(&self, addr: &Address, ts: &Tipset) -> Result<Address, Error> {
        self.lookup_id(addr, ts)?
            .ok_or_else(|| Error::Other(format!("Failed to lookup the id address {addr}")))
    }

    /// Retrieves market state
    pub fn market_state(&self, ts: &Tipset) -> Result<market::State, Error> {
        let actor = self.get_required_actor(&Address::MARKET_ACTOR, *ts.parent_state())?;
        let market_state = market::State::load(self.blockstore(), actor.code, actor.state)?;
        Ok(market_state)
    }

    /// Retrieves market balance in escrow and locked tables.
    pub fn market_balance(&self, addr: &Address, ts: &Tipset) -> Result<MarketBalance, Error> {
        let market_state = self.market_state(ts)?;
        let new_addr = self.lookup_required_id(addr, ts)?;
        let out = MarketBalance {
            escrow: {
                market_state
                    .escrow_table(self.blockstore())?
                    .get(&new_addr)?
            },
            locked: {
                market_state
                    .locked_table(self.blockstore())?
                    .get(&new_addr)?
            },
        };

        Ok(out)
    }

    /// Retrieves miner info.
    pub fn miner_info(&self, addr: &Address, ts: &Tipset) -> Result<MinerInfo, Error> {
        let actor = self
            .get_actor(addr, *ts.parent_state())?
            .ok_or_else(|| Error::state("Miner actor not found"))?;
        let state = miner::State::load(self.blockstore(), actor.code, actor.state)?;

        Ok(state.info(self.blockstore())?)
    }

    /// Retrieves miner faults.
    pub fn miner_faults(&self, addr: &Address, ts: &Tipset) -> Result<BitField, Error> {
        self.all_partition_sectors(addr, ts, |partition| partition.faulty_sectors().clone())
    }

    /// Retrieves miner recoveries.
    pub fn miner_recoveries(&self, addr: &Address, ts: &Tipset) -> Result<BitField, Error> {
        self.all_partition_sectors(addr, ts, |partition| partition.recovering_sectors().clone())
    }

    fn all_partition_sectors(
        &self,
        addr: &Address,
        ts: &Tipset,
        get_sector: impl Fn(Partition<'_>) -> BitField,
    ) -> Result<BitField, Error> {
        let actor = self
            .get_actor(addr, *ts.parent_state())?
            .ok_or_else(|| Error::state("Miner actor not found"))?;

        let state = miner::State::load(self.blockstore(), actor.code, actor.state)?;

        let mut partitions = Vec::new();

        state.for_each_deadline(
            &self.chain_config().policy,
            self.blockstore(),
            |_, deadline| {
                deadline.for_each(self.blockstore(), |_, partition| {
                    partitions.push(get_sector(partition));
                    Ok(())
                })
            },
        )?;

        Ok(BitField::union(partitions.iter()))
    }

    /// Retrieves miner power.
    pub fn miner_power(&self, addr: &Address, ts: &Tipset) -> Result<MinerPower, Error> {
        if let Some((miner_power, total_power)) = self.get_power(ts.parent_state(), Some(addr))? {
            return Ok(MinerPower {
                miner_power,
                total_power,
                has_min_power: true,
            });
        }

        Ok(MinerPower {
            has_min_power: false,
            miner_power: Default::default(),
            total_power: Default::default(),
        })
    }

    /// Similar to `resolve_to_key_addr` in the `forest_vm` [`crate::state_manager`] but does not
    /// allow `Actor` type of addresses. Uses `ts` to generate the VM state.
    pub async fn resolve_to_key_addr(
        self: &Arc<Self>,
        addr: &Address,
        ts: &Tipset,
    ) -> anyhow::Result<Address> {
        match addr.protocol() {
            Protocol::BLS | Protocol::Secp256k1 | Protocol::Delegated => return Ok(*addr),
            Protocol::Actor => {
                return Err(Error::Other(
                    "cannot resolve actor address to key address".to_string(),
                )
                .into());
            }
            _ => {}
        };

        // First try to resolve the actor in the parent state, so we don't have to
        // compute anything.
        let state = StateTree::new_from_root(self.blockstore_owned(), ts.parent_state())?;
        if let Ok(addr) = resolve_to_key_addr(&state, self.blockstore(), addr) {
            return Ok(addr);
        }

        // If that fails, compute the tip-set and try again.
        let TipsetState { state_root, .. } = self.load_tipset_state(ts).await?;
        let state = StateTree::new_from_root(self.blockstore_owned(), &state_root)?;

        resolve_to_key_addr(&state, self.blockstore(), addr)
    }

    pub async fn miner_get_base_info(
        self: &Arc<Self>,
        beacon_schedule: &BeaconSchedule,
        tipset: Tipset,
        addr: Address,
        epoch: ChainEpoch,
    ) -> anyhow::Result<Option<MiningBaseInfo>> {
        let prev_beacon = self
            .chain_store()
            .chain_index()
            .latest_beacon_entry(tipset.clone())?;

        let entries: Vec<BeaconEntry> = beacon_schedule
            .beacon_entries_for_block(
                self.chain_config().network_version(epoch),
                epoch,
                tipset.epoch(),
                &prev_beacon,
            )
            .await?;

        let base = entries.last().unwrap_or(&prev_beacon);

        let (lb_tipset, lb_state_root) = ChainStore::get_lookback_tipset_for_round(
            self.chain_index(),
            self.chain_config(),
            &tipset,
            epoch,
        )?;

        // If the miner actor doesn't exist in the current tipset, it is a
        // user-error and we must return an error message. If the miner exists
        // in the current tipset but not in the lookback tipset, we may not
        // error and should instead return None.
        let actor = self.get_required_actor(&addr, *tipset.parent_state())?;
        if self.get_actor(&addr, lb_state_root)?.is_none() {
            return Ok(None);
        }

        let miner_state = miner::State::load(self.blockstore(), actor.code, actor.state)?;

        let addr_buf = to_vec(&addr)?;
        let rand = draw_randomness(
            base.signature(),
            DomainSeparationTag::WinningPoStChallengeSeed as i64,
            epoch,
            &addr_buf,
        )?;

        let network_version = self.chain_config().network_version(tipset.epoch());
        let sectors = self.get_sectors_for_winning_post(
            &lb_state_root,
            network_version,
            &addr,
            Randomness::new(rand.to_vec()),
        )?;

        if sectors.is_empty() {
            return Ok(None);
        }

        let (miner_power, total_power) = self
            .get_power(&lb_state_root, Some(&addr))?
            .context("failed to get power")?;

        let info = miner_state.info(self.blockstore())?;

        let worker_key = self
            .resolve_to_deterministic_address(info.worker, &tipset)
            .await?;
        let eligible = self.eligible_to_mine(&addr, &tipset, &lb_tipset)?;

        Ok(Some(MiningBaseInfo {
            miner_power: miner_power.quality_adj_power,
            network_power: total_power.quality_adj_power,
            sectors,
            worker_key,
            sector_size: info.sector_size,
            prev_beacon_entry: prev_beacon,
            beacon_entries: entries,
            eligible_for_mining: eligible,
        }))
    }

    /// Checks power actor state for if miner meets consensus minimum
    /// requirements.
    pub fn miner_has_min_power(
        &self,
        policy: &Policy,
        addr: &Address,
        ts: &Tipset,
    ) -> anyhow::Result<bool> {
        let actor = self
            .get_actor(&Address::POWER_ACTOR, *ts.parent_state())?
            .ok_or_else(|| Error::state("Power actor address could not be resolved"))?;
        let ps = power::State::load(self.blockstore(), actor.code, actor.state)?;

        ps.miner_nominal_power_meets_consensus_minimum(policy, self.blockstore(), addr)
    }

    /// Validates all tipsets at epoch `start..=end` behind the heaviest tipset.
    ///
    /// Tipsets are processed sequentially. The compute-intensive work inside each
    /// tipset (`bellperson` proof verification, FVM batch seal verification, etc.)
    /// is already heavily rayon-parallelized. Parallelizing the outer loop actually introduces
    /// some issues due to locks in the aforementioned crates. So don't do it.
    ///
    /// # What is validation?
    /// Every state transition returns a new _state root_, which is typically retained in, e.g., snapshots.
    /// For "full" snapshots, all state roots are retained.
    /// For standard snapshots, the last 2000 or so state roots are retained.
    ///
    /// _receipts_ meanwhile, are typically ephemeral, but each tipset knows the _receipt root_
    /// (hash) of the previous tipset.
    ///
    /// This function takes advantage of that fact to validate tipsets:
    /// - `tipset[N]` claims that `receipt_root[N-1]` should be `0xDEADBEEF`
    /// - find `tipset[N-1]`, and perform its state transition to get the actual `receipt_root`
    /// - assert that they match
    ///
    /// See [`Self::compute_tipset_state_blocking`] for an explanation of state transitions.
    #[tracing::instrument(skip(self))]
    pub fn validate_range(&self, epochs: RangeInclusive<i64>) -> anyhow::Result<()> {
        let heaviest = self.heaviest_tipset();
        let heaviest_epoch = heaviest.epoch();
        let end = self
            .chain_index()
            .tipset_by_height(*epochs.end(), heaviest, ResolveNullTipset::TakeOlder)
            .with_context(|| {
                format!(
            "couldn't get a tipset at height {} behind heaviest tipset at height {heaviest_epoch}",
            *epochs.end(),
        )
            })?;

        // lookup tipset parents as we go along, iterating DOWN from `end`
        let tipsets = end
            .chain(self.blockstore())
            .take_while(|ts| ts.epoch() >= *epochs.start());

        self.validate_tipsets(tipsets)
    }

    pub fn validate_tipsets<T>(&self, tipsets: T) -> anyhow::Result<()>
    where
        T: Iterator<Item = Tipset> + Send,
    {
        let genesis_timestamp = self.chain_store().genesis_block_header().timestamp;
        validate_tipsets(
            genesis_timestamp,
            self.chain_index(),
            self.chain_config(),
            self.beacon_schedule(),
            &self.engine,
            tipsets,
        )
    }

    pub fn get_verified_registry_actor_state(
        &self,
        ts: &Tipset,
    ) -> anyhow::Result<verifreg::State> {
        let act = self
            .get_actor(&Address::VERIFIED_REGISTRY_ACTOR, *ts.parent_state())
            .map_err(Error::state)?
            .ok_or_else(|| Error::state("actor not found"))?;
        verifreg::State::load(self.blockstore(), act.code, act.state)
    }
    pub fn get_claim(
        &self,
        addr: &Address,
        ts: &Tipset,
        claim_id: ClaimID,
    ) -> anyhow::Result<Option<Claim>> {
        let id_address = self.lookup_required_id(addr, ts)?;
        let state = self.get_verified_registry_actor_state(ts)?;
        state.get_claim(self.blockstore(), id_address, claim_id)
    }

    pub fn get_all_claims(&self, ts: &Tipset) -> anyhow::Result<HashMap<ClaimID, Claim>> {
        let state = self.get_verified_registry_actor_state(ts)?;
        state.get_all_claims(self.blockstore())
    }

    pub fn get_allocation(
        &self,
        addr: &Address,
        ts: &Tipset,
        allocation_id: AllocationID,
    ) -> anyhow::Result<Option<Allocation>> {
        let id_address = self.lookup_required_id(addr, ts)?;
        let state = self.get_verified_registry_actor_state(ts)?;
        state.get_allocation(self.blockstore(), id_address.id()?, allocation_id)
    }

    pub fn get_all_allocations(
        &self,
        ts: &Tipset,
    ) -> anyhow::Result<HashMap<AllocationID, Allocation>> {
        let state = self.get_verified_registry_actor_state(ts)?;
        state.get_all_allocations(self.blockstore())
    }

    pub fn verified_client_status(
        &self,
        addr: &Address,
        ts: &Tipset,
    ) -> anyhow::Result<Option<DataCap>> {
        let id = self.lookup_required_id(addr, ts)?;
        let network_version = self.get_network_version(ts.epoch());

        // This is a copy of Lotus code, we need to treat all the actors below version 9
        // differently. Which maps to network below version 17.
        // Original: https://github.com/filecoin-project/lotus/blob/5e76b05b17771da6939c7b0bf65127c3dc70ee23/node/impl/full/state.go#L1627-L1664.
        if (u32::from(network_version.0)) < 17 {
            let state = self.get_verified_registry_actor_state(ts)?;
            return state.verified_client_data_cap(self.blockstore(), id);
        }

        let act = self
            .get_actor(&Address::DATACAP_TOKEN_ACTOR, *ts.parent_state())
            .map_err(Error::state)?
            .ok_or_else(|| Error::state("Miner actor not found"))?;

        let state = datacap::State::load(self.blockstore(), act.code, act.state)?;

        state.verified_client_data_cap(self.blockstore(), id)
    }

    /// Similar to [`StateTree::resolve_to_deterministic_addr`] but does not allow [`crate::shim::address::Protocol::Actor`] type of addresses.
    /// Uses the [`Tipset`] `ts` to generate the VM state.
    pub async fn resolve_to_deterministic_address(
        self: &Arc<Self>,
        address: Address,
        ts: &Tipset,
    ) -> anyhow::Result<Address> {
        use crate::shim::address::Protocol::*;
        match address.protocol() {
            BLS | Secp256k1 | Delegated => Ok(address),
            Actor => anyhow::bail!("cannot resolve actor address to key address"),
            ID => {
                let id = address.id()?;
                if let Some(cached) = self.id_to_deterministic_address_cache.get_cloned(&id) {
                    return Ok(cached);
                }
                // First try to resolve the actor in the parent state, so we don't have to compute anything.
                let resolved = if let Ok(state) =
                    StateTree::new_from_root(self.blockstore_owned(), ts.parent_state())
                    && let Ok(address) = state
                        .resolve_to_deterministic_addr(self.chain_store().blockstore(), address)
                {
                    address
                } else {
                    // If that fails, compute the tip-set and try again.
                    let TipsetState { state_root, .. } = self.load_tipset_state(ts).await?;
                    let state = StateTree::new_from_root(self.blockstore_owned(), &state_root)?;
                    state.resolve_to_deterministic_addr(self.chain_store().blockstore(), address)?
                };
                self.id_to_deterministic_address_cache.push(id, resolved);
                Ok(resolved)
            }
        }
    }

    pub fn execution_trace(&self, tipset: &Tipset) -> anyhow::Result<(Cid, Vec<ApiInvocResult>)> {
        let mut invoc_trace = vec![];

        let genesis_timestamp = self.chain_store().genesis_block_header().timestamp;

        let callback = |ctx: MessageCallbackCtx<'_>| {
            match ctx.at {
                CalledAt::Applied | CalledAt::Reward => {
                    invoc_trace.push(ApiInvocResult {
                        msg_cid: ctx.message.cid(),
                        msg: ctx.message.message().clone(),
                        msg_rct: Some(ctx.apply_ret.msg_receipt()),
                        error: ctx.apply_ret.failure_info().unwrap_or_default(),
                        duration: ctx.duration.as_nanos().clamp(0, u128::from(u64::MAX)) as u64,
                        gas_cost: MessageGasCost::new(ctx.message.message(), ctx.apply_ret)?,
                        execution_trace: structured::parse_events(ctx.apply_ret.exec_trace())
                            .unwrap_or_default(),
                    });
                    Ok(())
                }
                _ => Ok(()), // ignored
            }
        };

        let ExecutedTipset { state_root, .. } = apply_block_messages(
            genesis_timestamp,
            self.chain_index().shallow_clone(),
            self.chain_config().shallow_clone(),
            self.beacon_schedule().shallow_clone(),
            &self.engine,
            tipset.shallow_clone(),
            Some(callback),
            VMTrace::Traced,
        )?;

        Ok((state_root, invoc_trace))
    }
}

pub fn validate_tipsets<DB, T>(
    genesis_timestamp: u64,
    chain_index: &ChainIndex<DB>,
    chain_config: &Arc<ChainConfig>,
    beacon: &Arc<BeaconSchedule>,
    engine: &MultiEngine,
    tipsets: T,
) -> anyhow::Result<()>
where
    DB: Blockstore + Send + Sync + 'static,
    T: Iterator<Item = Tipset> + Send,
{
    // Validate one tipset at a time. Parallelizing the outer loop across tipsets
    // might wedge the global rayon pool.
    // Sequential outer iteration leaves the entire rayon pool free for that
    // already-rich inner parallelism.
    for (child, parent) in tipsets.tuple_windows() {
        info!(height = parent.epoch(), "compute parent state");
        let ExecutedTipset {
            state_root: actual_state,
            receipt_root: actual_receipt,
            ..
        } = apply_block_messages(
            genesis_timestamp,
            chain_index.shallow_clone(),
            chain_config.shallow_clone(),
            beacon.shallow_clone(),
            engine,
            parent,
            NO_CALLBACK,
            VMTrace::NotTraced,
        )
        .context("couldn't compute tipset state")?;
        let expected_receipt = child.min_ticket_block().message_receipts;
        let expected_state = child.parent_state();
        if (expected_state, expected_receipt) != (&actual_state, actual_receipt) {
            error!(
                height = child.epoch(),
                ?expected_state,
                ?expected_receipt,
                ?actual_state,
                ?actual_receipt,
                "state mismatch"
            );
            bail!("state mismatch");
        }
    }
    Ok(())
}

/// Shared context for creating VMs and preparing tipset state.
///
/// Encapsulates randomness source, genesis info, VM construction,
/// null-epoch cron handling, and state migrations.
struct TipsetExecutor<'a, DB: Blockstore + Send + Sync + 'static> {
    tipset: Tipset,
    rand: ChainRand<DB>,
    chain_config: Arc<ChainConfig>,
    chain_index: ChainIndex<DB>,
    genesis_info: GenesisInfo,
    engine: &'a MultiEngine,
}

impl<'a, DB: Blockstore + Send + Sync + 'static> TipsetExecutor<'a, DB> {
    fn new(
        chain_index: ChainIndex<DB>,
        chain_config: Arc<ChainConfig>,
        beacon: Arc<BeaconSchedule>,
        engine: &'a MultiEngine,
        tipset: Tipset,
    ) -> Self {
        let rand = ChainRand::new(
            chain_config.shallow_clone(),
            tipset.shallow_clone(),
            chain_index.shallow_clone(),
            beacon,
        );
        let genesis_info = GenesisInfo::from_chain_config(chain_config.shallow_clone());
        Self {
            tipset,
            rand,
            chain_config,
            chain_index,
            genesis_info,
            engine,
        }
    }

    fn create_vm(
        &self,
        state_root: Cid,
        epoch: ChainEpoch,
        timestamp: u64,
        trace: VMTrace,
    ) -> anyhow::Result<VM<DB>> {
        let circ_supply = self.genesis_info.get_vm_circulating_supply(
            epoch,
            self.chain_index.db(),
            &state_root,
        )?;
        VM::new(
            ExecutionContext {
                heaviest_tipset: self.tipset.shallow_clone(),
                state_tree_root: state_root,
                epoch,
                rand: Box::new(self.rand.shallow_clone()),
                base_fee: self.tipset.min_ticket_block().parent_base_fee.clone(),
                circ_supply,
                chain_config: self.chain_config.shallow_clone(),
                chain_index: self.chain_index.shallow_clone(),
                timestamp,
            },
            self.engine,
            trace,
        )
    }

    /// Produces the state root ready for message execution by running
    /// null-epoch `crons` and any pending state migrations.
    fn prepare_parent_state<F>(
        &self,
        genesis_timestamp: u64,
        null_epoch_trace: VMTrace,
        cron_callback: &mut Option<F>,
    ) -> anyhow::Result<(Cid, ChainEpoch, Vec<BlockMessages>)>
    where
        F: FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()>,
    {
        use crate::shim::clock::EPOCH_DURATION_SECONDS;

        let mut parent_state = *self.tipset.parent_state();
        let parent_epoch = self
            .chain_index
            .load_required_tipset(self.tipset.parents())?
            .epoch();
        let epoch = self.tipset.epoch();

        for epoch_i in parent_epoch..epoch {
            if epoch_i > parent_epoch {
                let timestamp = genesis_timestamp + ((EPOCH_DURATION_SECONDS * epoch_i) as u64);
                parent_state = stacker::grow(64 << 20, || -> anyhow::Result<Cid> {
                    let mut vm =
                        self.create_vm(parent_state, epoch_i, timestamp, null_epoch_trace)?;
                    if let Err(e) = vm.run_cron(epoch_i, cron_callback.as_mut()) {
                        error!("Beginning of epoch cron failed to run: {e:#}");
                        return Err(e);
                    }
                    vm.flush()
                })?;
            }
            if let Some(new_state) = run_state_migrations(
                epoch_i,
                &self.chain_config,
                self.chain_index.db(),
                &parent_state,
            )? {
                parent_state = new_state;
            }
        }

        let block_messages = BlockMessages::for_tipset(self.chain_index.db(), &self.tipset)?;
        Ok((parent_state, epoch, block_messages))
    }
}

/// Messages are transactions that produce new states. The state (usually
/// referred to as the 'state-tree') is a mapping from actor addresses to actor
/// states. Each block contains the hash of the state-tree that should be used
/// as the starting state when executing the block messages.
///
/// # Execution environment
///
/// Transaction execution has the following inputs:
/// - a current state-tree (stored as IPLD in a key-value database). This
///   reference is in [`Tipset::parent_state`].
/// - up to 900 past state-trees. See
///   <https://docs.filecoin.io/reference/general/glossary/#finality>.
/// - up to 900 past tipset IDs.
/// - a deterministic source of randomness.
/// - the circulating supply of FIL (see
///   <https://filecoin.io/blog/filecoin-circulating-supply/>). The circulating
///   supply is determined by the epoch and the states of a few key actors.
/// - the base fee (see <https://spec.filecoin.io/systems/filecoin_vm/gas_fee/>).
///   This value is defined by `tipset.parent_base_fee`.
/// - the genesis timestamp (UNIX epoch time when the first block was
///   mined/created).
/// - a chain configuration (maps epoch to network version, has chain specific
///   settings).
///
/// The result of running a set of block messages is an index to the final
/// state-tree and an index to an array of message receipts (listing gas used,
/// return codes, etc).
///
/// # Cron and null tipsets
///
/// Once per epoch, after all messages have run, a special 'cron' transaction
/// must be executed. The tasks of the 'cron' transaction include running batch
/// jobs and keeping the state up-to-date with the current epoch.
///
/// It can happen that no blocks are mined in an epoch. The tipset for such an
/// epoch is called a null tipset. A null tipset has no identity and cannot be
/// directly executed. This is a problem for 'cron' which must run for every
/// epoch, even if there are no messages. The fix is to run 'cron' if there are
/// any null tipsets between the current epoch and the parent epoch.
///
/// Imagine the blockchain looks like this with a null tipset at epoch 9:
///
/// ```text
/// ┌────────┐ ┌────┐ ┌───────┐  ┌───────┐
/// │Epoch 10│ │Null│ │Epoch 8├──►Epoch 7├─►
/// └───┬────┘ └────┘ └───▲───┘  └───────┘
///     └─────────────────┘
/// ```
///
/// The parent of tipset-epoch-10 is tipset-epoch-8. Before executing the
/// messages in epoch 10, we have to run cron for epoch 9. However, running
/// 'cron' requires the timestamp of the youngest block in the tipset (which
/// doesn't exist because there are no blocks in the tipset). Lotus dictates that
/// the timestamp of a null tipset is `30s * epoch` after the genesis timestamp.
/// So, in the above example, if the genesis block was mined at time `X`, the
/// null tipset for epoch 9 will have timestamp `X + 30 * 9`.
///
/// # Migrations
///
/// Migrations happen between network upgrades and modify the state tree. If a
/// migration is scheduled for epoch 10, it will be run _after_ the messages for
/// epoch 10. The tipset for epoch 11 will link the state-tree produced by the
/// migration.
///
/// Example timeline with a migration at epoch 10:
///   1. Tipset-epoch-10 executes, producing state-tree A.
///   2. Migration consumes state-tree A and produces state-tree B.
///   3. Tipset-epoch-11 executes, consuming state-tree B (rather than A).
///
/// Note: The migration actually happens when tipset-epoch-11 executes. This is
///       because tipset-epoch-10 may be null and therefore not executed at all.
///
/// # Caching
///
/// Scanning the blockchain to find past tipsets and state-trees may be slow.
/// The `ChainStore` caches recent tipsets to make these scans faster.
#[allow(clippy::too_many_arguments)]
pub fn apply_block_messages<DB>(
    genesis_timestamp: u64,
    chain_index: ChainIndex<DB>,
    chain_config: Arc<ChainConfig>,
    beacon: Arc<BeaconSchedule>,
    engine: &MultiEngine,
    tipset: Tipset,
    mut callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()>>,
    enable_tracing: VMTrace,
) -> anyhow::Result<ExecutedTipset>
where
    DB: Blockstore + Send + Sync + 'static,
{
    // This function will:
    // 1. handle the genesis block as a special case
    // 2. run 'cron' for any null-tipsets between the current tipset and our parent tipset
    // 3. run migrations
    // 4. execute block messages
    // 5. write the state-tree to the DB and return the CID

    // step 1: special case for genesis block
    if tipset.epoch() == 0 {
        // NB: This is here because the process that executes blocks requires that the
        // block miner reference a valid miner in the state tree. Unless we create some
        // magical genesis miner, this won't work properly, so we short circuit here
        // This avoids the question of 'who gets paid the genesis block reward'
        let message_receipts = tipset.min_ticket_block().message_receipts;
        return Ok(ExecutedTipset {
            state_root: *tipset.parent_state(),
            receipt_root: message_receipts,
            executed_messages: vec![].into(),
        });
    }

    let exec = TipsetExecutor::new(
        chain_index.shallow_clone(),
        chain_config,
        beacon,
        engine,
        tipset.shallow_clone(),
    );

    // step 2: running cron for any null-tipsets
    // step 3: run migrations
    let (parent_state, epoch, block_messages) =
        exec.prepare_parent_state(genesis_timestamp, enable_tracing, &mut callback)?;

    // FVM requires a stack size of 64MiB. The alternative is to use `ThreadedExecutor` from
    // FVM, but that introduces some constraints, and possible deadlocks.
    stacker::grow(64 << 20, || -> anyhow::Result<ExecutedTipset> {
        let mut vm = exec.create_vm(parent_state, epoch, tipset.min_timestamp(), enable_tracing)?;

        // step 4: apply tipset messages
        let (receipts, events, events_roots) =
            vm.apply_block_messages(&block_messages, epoch, callback)?;

        // step 5: construct receipt root from receipts
        let receipt_root = Amtv0::new_from_iter(chain_index.db(), receipts.iter())?;

        // step 6: store events AMTs in the blockstore
        for (events, events_root) in events.iter().zip(events_roots.iter()) {
            if let Some(events) = events {
                let event_root =
                    events_root.context("events root should be present when events present")?;
                // Store the events AMT - the root CID should match the one computed by FVM
                let derived_event_root = Amt::new_from_iter_with_bit_width(
                    chain_index.db(),
                    EVENTS_AMT_BITWIDTH,
                    events.iter(),
                )
                .map_err(|e| Error::Other(format!("failed to store events AMT: {e}")))?;

                // Verify the stored root matches the FVM-computed root
                ensure!(
                    derived_event_root == event_root,
                    "Events AMT root mismatch: derived={derived_event_root}, actual={event_root}."
                );
            }
        }

        let state_root = vm.flush()?;

        // Update executed tipset cache
        let messages: Vec<ChainMessage> = block_messages
            .into_iter()
            .flat_map(|bm| bm.messages)
            .collect_vec();
        anyhow::ensure!(
            messages.len() == receipts.len() && messages.len() == events.len(),
            "length of messages, receipts, and events should match",
        );
        Ok(ExecutedTipset {
            state_root,
            receipt_root,
            executed_messages: messages
                .into_iter()
                .zip(receipts)
                .zip(events)
                .map(|((message, receipt), events)| ExecutedMessage {
                    message,
                    receipt,
                    events,
                })
                .collect_vec()
                .into(),
        })
    })
}

#[allow(clippy::too_many_arguments)]
pub fn compute_state<DB>(
    _height: ChainEpoch,
    messages: Vec<Message>,
    tipset: Tipset,
    genesis_timestamp: u64,
    chain_index: ChainIndex<DB>,
    chain_config: Arc<ChainConfig>,
    beacon: Arc<BeaconSchedule>,
    engine: &MultiEngine,
    callback: Option<impl FnMut(MessageCallbackCtx<'_>) -> anyhow::Result<()>>,
    enable_tracing: VMTrace,
) -> anyhow::Result<ExecutedTipset>
where
    DB: Blockstore + Send + Sync + 'static,
{
    if !messages.is_empty() {
        anyhow::bail!("Applying messages is not yet implemented.");
    }

    let output = apply_block_messages(
        genesis_timestamp,
        chain_index,
        chain_config,
        beacon,
        engine,
        tipset,
        callback,
        enable_tracing,
    )?;

    Ok(output)
}

/// Controls whether the VM should flush its state after execution
#[derive(Debug, Copy, Clone, Default)]
pub enum VMFlush {
    Flush,
    #[default]
    Skip,
}