ic_testkit/pic/

snapshot.rs

use std::collections::BTreeMap;

use candid::Principal;
use pocket_ic::{PocketIc, RejectResponse};

use super::{PocketIcCallFailure, transport};

#[derive(Clone, Debug, Eq, PartialEq)]
struct ControllerSnapshot {
    snapshot_id: Vec<u8>,
    sender: Option<Principal>,
}

/// Deterministically ordered snapshots retaining each successful capture sender.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ControllerSnapshots(BTreeMap<Principal, ControllerSnapshot>);

/// One canister and exact management-call sender used for snapshot capture.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct CanisterSnapshotTarget {
    canister_id: Principal,
    sender: Option<Principal>,
}

/// Failure to remove a snapshot while rolling back a partial capture.
#[non_exhaustive]
#[derive(Debug)]
pub struct SnapshotCleanupFailure {
    /// Canister whose snapshot could not be removed.
    pub canister_id: Principal,
    /// Exact sender selected for cleanup.
    pub sender: Option<Principal>,
    /// Complete rejection or operation failure, retaining transport classification.
    pub source: Box<PocketIcCallFailure>,
}

/// Caller-selected cycle funding applied immediately before snapshot restore.
#[non_exhaustive]
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum SnapshotRestoreFunding {
    /// Do not add cycles before the restore operation.
    Preserve,
    /// Add cycles only when needed to reach the given minimum balance.
    TopUpTo {
        /// Minimum balance established immediately before each restore.
        minimum_cycles: u128,
    },
}

/// Structured controller-snapshot failure.
#[non_exhaustive]
#[derive(Debug)]
pub enum ControllerSnapshotError {
    /// A cached baseline requires at least one canister.
    EmptyCanisterSet,
    /// Input contained the same canister more than once.
    DuplicateCanisterId {
        /// Repeated canister id.
        canister_id: Principal,
    },
    /// Snapshot capture failed with the exact selected sender.
    CaptureFailed {
        /// Canister whose capture failed.
        canister_id: Principal,
        /// Exact sender selected for capture.
        sender: Option<Principal>,
        /// Complete rejection or operation failure.
        source: Box<PocketIcCallFailure>,
        /// Failures while deleting snapshots captured earlier in the set.
        cleanup_failures: Vec<SnapshotCleanupFailure>,
    },
    /// Snapshot restore failed with the retained capture sender.
    RestoreFailed {
        /// Canister whose restore failed.
        canister_id: Principal,
        /// Exact sender selected for restore.
        sender: Option<Principal>,
        /// Complete rejection or operation failure.
        source: Box<PocketIcCallFailure>,
    },
}

/// Exact-sender capture and restore of related canister snapshots.
pub trait PocketIcSnapshotExt {
    /// Capture snapshots with one explicit sender per canister.
    ///
    /// Input is duplicate-checked before any effects and captured in deterministic
    /// canister-id order. A later failure rolls back snapshots captured earlier
    /// in the set. No other sender is attempted after a rejection.
    fn capture_snapshots<I>(
        &self,
        targets: I,
    ) -> Result<ControllerSnapshots, ControllerSnapshotError>
    where
        I: IntoIterator<Item = CanisterSnapshotTarget>;

    /// Restore each snapshot with its exact captured sender and selected funding.
    ///
    /// `Preserve` never adds cycles; `TopUpTo` is evaluated before each restore.
    /// PocketIC may charge cycles for the restore itself. Rejection or panic stops
    /// the set without retrying another sender or rewinding earlier restores.
    fn restore_snapshots(
        &self,
        snapshots: &ControllerSnapshots,
        funding: SnapshotRestoreFunding,
    ) -> Result<(), ControllerSnapshotError>;
}

impl PocketIcSnapshotExt for PocketIc {
    fn capture_snapshots<I>(
        &self,
        targets: I,
    ) -> Result<ControllerSnapshots, ControllerSnapshotError>
    where
        I: IntoIterator<Item = CanisterSnapshotTarget>,
    {
        capture_snapshot_set(self, targets)
    }

    fn restore_snapshots(
        &self,
        snapshots: &ControllerSnapshots,
        funding: SnapshotRestoreFunding,
    ) -> Result<(), ControllerSnapshotError> {
        for (canister_id, snapshot_id, sender) in snapshots.iter() {
            restore_controller_snapshot(self, canister_id, snapshot_id, funding, sender)?;
        }
        Ok(())
    }
}

impl CanisterSnapshotTarget {
    /// Select one canister and exact sender for snapshot capture.
    #[must_use]
    pub const fn new(canister_id: Principal, sender: Option<Principal>) -> Self {
        Self {
            canister_id,
            sender,
        }
    }

    /// Canister whose snapshot will be captured.
    #[must_use]
    pub const fn canister_id(self) -> Principal {
        self.canister_id
    }

    /// Exact management-call sender, including `None` for the default sender.
    #[must_use]
    pub const fn sender(self) -> Option<Principal> {
        self.sender
    }
}

fn capture_snapshot_set<I>(
    pocket_ic: &PocketIc,
    targets: I,
) -> Result<ControllerSnapshots, ControllerSnapshotError>
where
    I: IntoIterator<Item = CanisterSnapshotTarget>,
{
    // Validate the entire input before issuing any management calls. The map
    // also owns the deterministic canister order.
    let mut ordered_targets = BTreeMap::new();
    for target in targets {
        if ordered_targets
            .insert(target.canister_id, target.sender)
            .is_some()
        {
            return Err(ControllerSnapshotError::DuplicateCanisterId {
                canister_id: target.canister_id,
            });
        }
    }
    let mut snapshots = BTreeMap::new();
    for (canister_id, sender) in ordered_targets {
        let failure = match try_take_snapshot(pocket_ic, canister_id, sender) {
            Ok(snapshot) => {
                snapshots.insert(canister_id, snapshot);
                continue;
            }
            Err(failure) => failure,
        };
        let cleanup_failures =
            cleanup_captured_snapshots(snapshots, |canister_id, sender, snapshot_id| {
                pocket_ic.delete_canister_snapshot(canister_id, sender, snapshot_id)
            });
        return Err(ControllerSnapshotError::CaptureFailed {
            canister_id,
            sender,
            source: Box::new(failure),
            cleanup_failures,
        });
    }
    Ok(ControllerSnapshots(snapshots))
}

impl ControllerSnapshots {
    /// Return the number of captured canisters.
    #[must_use]
    pub fn len(&self) -> usize {
        self.0.len()
    }

    /// Report whether the set contains no snapshots.
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }

    /// Iterate over captured canister ids in deterministic principal order.
    pub fn canister_ids(&self) -> impl Iterator<Item = Principal> + '_ {
        self.0.keys().copied()
    }

    pub(super) fn iter(&self) -> impl Iterator<Item = (Principal, &[u8], Option<Principal>)> + '_ {
        self.0.iter().map(|(canister_id, snapshot)| {
            (
                *canister_id,
                snapshot.snapshot_id.as_slice(),
                snapshot.sender,
            )
        })
    }
}

impl std::fmt::Display for ControllerSnapshotError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::EmptyCanisterSet => {
                f.write_str("a cached baseline requires at least one canister")
            }
            Self::DuplicateCanisterId { canister_id } => {
                write!(f, "duplicate canister id in snapshot set: {canister_id}")
            }
            Self::CaptureFailed {
                canister_id,
                sender,
                source,
                cleanup_failures,
            } => write!(
                f,
                "failed to capture snapshot for {canister_id} with sender {sender:?}: {source}; {} partial snapshots could not be cleaned up",
                cleanup_failures.len()
            ),
            Self::RestoreFailed {
                canister_id,
                sender,
                source,
            } => write!(
                f,
                "failed to restore snapshot for {canister_id} with sender {sender:?}: {source}",
            ),
        }
    }
}

impl std::error::Error for ControllerSnapshotError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Self::CaptureFailed { source, .. } | Self::RestoreFailed { source, .. } => {
                Some(source.as_ref())
            }
            _ => None,
        }
    }
}

fn try_take_snapshot(
    pocket_ic: &PocketIc,
    canister_id: Principal,
    sender: Option<Principal>,
) -> Result<ControllerSnapshot, PocketIcCallFailure> {
    let snapshot =
        transport::capture_call(|| pocket_ic.take_canister_snapshot(canister_id, sender, None))?;
    Ok(ControllerSnapshot {
        snapshot_id: snapshot.id,
        sender,
    })
}

fn cleanup_captured_snapshots(
    snapshots: BTreeMap<Principal, ControllerSnapshot>,
    mut remove: impl FnMut(Principal, Option<Principal>, Vec<u8>) -> Result<(), RejectResponse>,
) -> Vec<SnapshotCleanupFailure> {
    let mut failures = Vec::new();
    for (canister_id, snapshot) in snapshots {
        let cleanup =
            transport::capture_call(|| remove(canister_id, snapshot.sender, snapshot.snapshot_id));
        if let Err(source) = cleanup {
            failures.push(SnapshotCleanupFailure {
                canister_id,
                sender: snapshot.sender,
                source: Box::new(source),
            });
        }
    }
    failures
}

fn restore_controller_snapshot(
    pocket_ic: &PocketIc,
    canister_id: Principal,
    snapshot_id: &[u8],
    funding: SnapshotRestoreFunding,
    sender: Option<Principal>,
) -> Result<(), ControllerSnapshotError> {
    transport::capture_call(|| {
        apply_snapshot_restore_funding(pocket_ic, canister_id, funding);
        pocket_ic.load_canister_snapshot(canister_id, sender, snapshot_id.to_vec())
    })
    .map_err(|source| ControllerSnapshotError::RestoreFailed {
        canister_id,
        sender,
        source: Box::new(source),
    })
}

fn apply_snapshot_restore_funding(
    pocket_ic: &PocketIc,
    canister_id: Principal,
    funding: SnapshotRestoreFunding,
) {
    if funding == SnapshotRestoreFunding::Preserve {
        return;
    }

    let balance = pocket_ic.cycle_balance(canister_id);
    let top_up = snapshot_restore_top_up(balance, funding);
    if top_up > 0 {
        let _ = pocket_ic.add_cycles(canister_id, top_up);
    }
}

const fn snapshot_restore_top_up(balance: u128, funding: SnapshotRestoreFunding) -> u128 {
    match funding {
        SnapshotRestoreFunding::Preserve => 0,
        SnapshotRestoreFunding::TopUpTo { minimum_cycles } => {
            minimum_cycles.saturating_sub(balance)
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{SnapshotRestoreFunding, snapshot_restore_top_up};

    #[test]
    fn cleanup_preserves_causes_and_senders_and_continues_after_each_failure() {
        use super::{
            ControllerSnapshot, PocketIcCallFailure, SnapshotCleanupFailure,
            cleanup_captured_snapshots,
        };
        use candid::Principal;
        use pocket_ic::{ErrorCode, RejectCode, RejectResponse};

        let ids = [1, 2, 3, 4].map(|byte| Principal::from_slice(&[byte]));
        let sender = Some(Principal::anonymous());
        let snapshots = ids
            .map(|id| {
                (
                    id,
                    ControllerSnapshot {
                        snapshot_id: vec![7],
                        sender,
                    },
                )
            })
            .into_iter()
            .collect();
        let rejection = RejectResponse {
            reject_code: RejectCode::CanisterReject,
            reject_message: "cleanup rejected".into(),
            error_code: ErrorCode::CanisterCalledTrap,
            certified: false,
        };
        let transport = "reqwest::Error { kind: Request, url: \"http://127.0.0.1:1234/instances/0/update/delete_canister_snapshot\", source: hyper::Error(IncompleteMessage) }";
        let mut calls = Vec::new();
        let failures = cleanup_captured_snapshots(snapshots, |id, selected_sender, snapshot_id| {
            assert_eq!(snapshot_id, [7]);
            calls.push((id, selected_sender));
            if id == ids[1] {
                return Err(rejection.clone());
            }
            if id == ids[2] {
                std::panic::panic_any(transport.to_owned());
            }
            Ok(())
        });
        assert_eq!(calls, ids.map(|id| (id, sender)));
        let [
            SnapshotCleanupFailure {
                canister_id: rejected_id,
                sender: rejected_sender,
                source: rejected,
            },
            SnapshotCleanupFailure {
                canister_id: panicked_id,
                sender: panicked_sender,
                source: panicked,
            },
        ] = failures.as_slice()
        else {
            panic!("expected both cleanup failures: {failures:?}");
        };
        assert_eq!(*rejected_id, ids[1]);
        assert_eq!(*rejected_sender, sender);
        let PocketIcCallFailure::Rejected(response) = rejected.as_ref() else {
            panic!("expected rejection: {rejected:?}");
        };
        assert_eq!(response, &rejection);
        assert_eq!(*panicked_id, ids[2]);
        assert_eq!(*panicked_sender, sender);
        let PocketIcCallFailure::Operation(source) = panicked.as_ref() else {
            panic!("expected operation failure: {panicked:?}");
        };
        assert!(source.is_transport());
        assert_eq!(source.message(), transport);
    }

    #[test]
    fn snapshot_restore_funding_is_explicit() {
        assert_eq!(
            snapshot_restore_top_up(10, SnapshotRestoreFunding::Preserve),
            0
        );
        assert_eq!(
            snapshot_restore_top_up(10, SnapshotRestoreFunding::TopUpTo { minimum_cycles: 25 }),
            15
        );
        assert_eq!(
            snapshot_restore_top_up(30, SnapshotRestoreFunding::TopUpTo { minimum_cycles: 25 }),
            0
        );
    }
}