ic-query 0.30.3

//! Module: nns::registry::replay
//!
//! Responsibility: apply one validated certified Registry delta batch to bounded memory state.
//! Does not own: network pagination, persistence, catalog projection, or assurance promotion.
//! Boundary: committed changelog rows are applied atomically and never trigger follow-up IO.

use super::{
    NnsCertifiedRegistryDeltaBatchReport, NnsCertifiedRegistryDeltaBatchRequest,
    NnsCertifiedRegistryMutation, NnsCertifiedRegistryMutationKind, NnsRegistryHostError,
    validate_nns_certified_registry_delta_batch,
};
use std::collections::BTreeMap;
use thiserror::Error as ThisError;

///
/// NnsRegistryReplayLimits
///
/// Caller-selected payload ceilings for one published Registry replay state.
///

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct NnsRegistryReplayLimits {
    /// Maximum live Registry keys retained after any applied mutation.
    pub max_entries: usize,
    /// Maximum combined raw key and live value bytes in the resulting state.
    pub max_content_bytes: usize,
}

impl NnsRegistryReplayLimits {
    /// Create explicit replay-state ceilings without selecting hidden defaults.
    #[must_use]
    pub const fn new(max_entries: usize, max_content_bytes: usize) -> Self {
        Self {
            max_entries,
            max_content_bytes,
        }
    }
}

///
/// NnsRegistryReplayValue
///
/// Current value and last committed mutation evidence for one Registry key.
///

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct NnsRegistryReplayValue {
    value: Vec<u8>,
    last_mutation_version: u64,
    timestamp_nanoseconds: u64,
}

impl NnsRegistryReplayValue {
    /// Return the current raw Registry value bytes.
    #[must_use]
    pub fn value(&self) -> &[u8] {
        &self.value
    }

    /// Return the Registry version that last mutated this key.
    #[must_use]
    pub const fn last_mutation_version(&self) -> u64 {
        self.last_mutation_version
    }

    /// Return the Registry-assigned timestamp of the last mutation.
    #[must_use]
    pub const fn timestamp_nanoseconds(&self) -> u64 {
        self.timestamp_nanoseconds
    }
}

///
/// NnsRegistryReplayState
///
/// Canonically ordered current Registry key state reconstructed from version zero.
/// This in-memory state is not authority evidence by itself. Callers must retain
/// and validate the certified batches that produced it.
///

#[derive(Clone, Debug, Default, Eq, PartialEq)]
pub struct NnsRegistryReplayState {
    through_version: u64,
    content_bytes: usize,
    entries: BTreeMap<Vec<u8>, NnsRegistryReplayValue>,
}

impl NnsRegistryReplayState {
    /// Create an empty Registry state immediately before version one.
    #[must_use]
    pub const fn new() -> Self {
        Self {
            through_version: 0,
            content_bytes: 0,
            entries: BTreeMap::new(),
        }
    }

    /// Return the last Registry version applied to this state.
    #[must_use]
    pub const fn through_version(&self) -> u64 {
        self.through_version
    }

    /// Return the number of currently present Registry keys.
    #[must_use]
    pub fn entry_count(&self) -> usize {
        self.entries.len()
    }

    /// Return combined raw key and current value bytes.
    #[must_use]
    pub const fn content_bytes(&self) -> usize {
        self.content_bytes
    }

    /// Return whether the current Registry state has no present keys.
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.entries.is_empty()
    }

    /// Look up one current Registry value by raw key bytes.
    #[must_use]
    pub fn get(&self, key: &[u8]) -> Option<&NnsRegistryReplayValue> {
        self.entries.get(key)
    }

    /// Iterate current Registry keys in canonical raw-byte order.
    pub fn entries(&self) -> impl Iterator<Item = (&[u8], &NnsRegistryReplayValue)> {
        self.entries
            .iter()
            .map(|(key, value)| (key.as_slice(), value))
    }
}

///
/// NnsRegistryReplayProgress
///
/// Derived state and completion accounting after one atomic batch application.
///

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct NnsRegistryReplayProgress {
    /// Registry version held before the batch was applied.
    pub previous_version: u64,
    /// Last Registry version held after the batch was applied.
    pub through_version: u64,
    /// Number of contiguous Registry versions applied from this batch.
    pub applied_version_count: usize,
    /// Number of committed mutations applied from this batch.
    pub applied_mutation_count: usize,
    /// Number of currently present Registry keys.
    pub entry_count: usize,
    /// Combined raw key and current value bytes.
    pub content_bytes: usize,
    /// Whether the state reached this batch's certified latest version.
    pub complete_at_certified_latest_version: bool,
}

///
/// NnsRegistryReplayError
///
/// Typed failures returned before an invalid or oversized replay state is published.
///

#[derive(Debug, ThisError)]
pub enum NnsRegistryReplayError {
    /// The supplied certified batch report failed its public contract.
    #[error(transparent)]
    InvalidBatch(#[from] NnsRegistryHostError),

    /// The batch does not continue immediately after the current replay state.
    #[error(
        "Registry replay state is at version {state_version}, but the batch starts after version {requested_version}"
    )]
    VersionMismatch {
        /// Version currently held by the replay state.
        state_version: u64,
        /// Version named by the batch request and report.
        requested_version: u64,
    },

    /// The existing or candidate state exceeds a caller-selected payload ceiling.
    #[error("Registry replay {field} is {actual}; caller maximum is {maximum}")]
    LimitExceeded {
        /// Bounded replay-state resource.
        field: &'static str,
        /// Caller-selected ceiling.
        maximum: usize,
        /// Existing or candidate amount.
        actual: usize,
    },

    /// Validated report content could not be decoded defensively.
    #[error("validated Registry replay {field} is not lowercase hexadecimal")]
    InvalidHex {
        /// Report field that failed decoding.
        field: &'static str,
    },

    /// Internal byte accounting could not be represented consistently.
    #[error("Registry replay byte accounting overflowed or became inconsistent")]
    Accounting,
}

/// Apply exactly one validated certified Registry delta batch atomically.
///
/// The committed changelog has already passed Registry mutation checks. To
/// match the official Registry reconstruction path, insert, update, and upsert
/// rows all replace the current value; delete rows remove it. Recorded
/// preconditions are evidence attached to the committed transaction and are
/// not re-evaluated during replay.
pub fn apply_nns_certified_registry_delta_batch(
    state: &mut NnsRegistryReplayState,
    request: &NnsCertifiedRegistryDeltaBatchRequest,
    report: &NnsCertifiedRegistryDeltaBatchReport,
    limits: NnsRegistryReplayLimits,
) -> Result<NnsRegistryReplayProgress, NnsRegistryReplayError> {
    validate_nns_certified_registry_delta_batch(request, report)?;
    if state.through_version != report.requested_version {
        return Err(NnsRegistryReplayError::VersionMismatch {
            state_version: state.through_version,
            requested_version: report.requested_version,
        });
    }
    enforce_limits(state, limits)?;

    let mut journal = ReplayJournal::new(state);
    let application = (|| {
        for version in &report.versions {
            for mutation in &version.mutations {
                apply_committed_mutation(
                    state,
                    &mut journal,
                    version.version,
                    version.timestamp_nanoseconds,
                    mutation,
                    limits,
                )?;
            }
            state.through_version = version.version;
        }
        enforce_limits(state, limits)
    })();
    if let Err(error) = application {
        journal.rollback(state);
        return Err(error);
    }
    let progress = NnsRegistryReplayProgress {
        previous_version: journal.previous_version,
        through_version: state.through_version,
        applied_version_count: report.version_count,
        applied_mutation_count: report.mutation_count,
        entry_count: state.entries.len(),
        content_bytes: state.content_bytes,
        complete_at_certified_latest_version: state.through_version
            == report.certified_latest_version,
    };
    Ok(progress)
}

fn apply_committed_mutation(
    state: &mut NnsRegistryReplayState,
    journal: &mut ReplayJournal,
    version: u64,
    timestamp_nanoseconds: u64,
    mutation: &NnsCertifiedRegistryMutation,
    limits: NnsRegistryReplayLimits,
) -> Result<(), NnsRegistryReplayError> {
    let key = decode_hex("mutation key", &mutation.key_hex)?;
    if mutation.mutation_kind == NnsCertifiedRegistryMutationKind::Delete {
        let prior_content_bytes = journal.remove_current(state, &key)?;
        state.content_bytes = state
            .content_bytes
            .checked_sub(prior_content_bytes)
            .ok_or(NnsRegistryReplayError::Accounting)?;
        return Ok(());
    }
    let value_hex = mutation
        .value_hex
        .as_deref()
        .ok_or(NnsRegistryReplayError::InvalidHex {
            field: "mutation value",
        })?;
    let value_bytes = value_hex.len() / 2;
    let prior_content_bytes = journal.remove_current(state, &key)?;
    let candidate_content_bytes = state
        .content_bytes
        .checked_sub(prior_content_bytes)
        .and_then(|bytes| bytes.checked_add(key.len()))
        .and_then(|bytes| bytes.checked_add(value_bytes))
        .ok_or(NnsRegistryReplayError::Accounting)?;
    enforce_limit(
        "content bytes",
        candidate_content_bytes,
        limits.max_content_bytes,
    )?;
    let candidate_entry_count = state
        .entries
        .len()
        .checked_add(1)
        .ok_or(NnsRegistryReplayError::Accounting)?;
    enforce_limit("entry count", candidate_entry_count, limits.max_entries)?;

    state.entries.insert(
        key,
        NnsRegistryReplayValue {
            value: decode_hex("mutation value", value_hex)?,
            last_mutation_version: version,
            timestamp_nanoseconds,
        },
    );
    state.content_bytes = candidate_content_bytes;
    Ok(())
}

struct ReplayJournal {
    previous_version: u64,
    previous_content_bytes: usize,
    entries: BTreeMap<Vec<u8>, Option<NnsRegistryReplayValue>>,
}

impl ReplayJournal {
    const fn new(state: &NnsRegistryReplayState) -> Self {
        Self {
            previous_version: state.through_version,
            previous_content_bytes: state.content_bytes,
            entries: BTreeMap::new(),
        }
    }

    fn remove_current(
        &mut self,
        state: &mut NnsRegistryReplayState,
        key: &[u8],
    ) -> Result<usize, NnsRegistryReplayError> {
        let current = state.entries.remove(key);
        let content_bytes = current.as_ref().map_or(Ok(0), |value| {
            key.len()
                .checked_add(value.value.len())
                .ok_or(NnsRegistryReplayError::Accounting)
        })?;
        self.entries.entry(key.to_vec()).or_insert(current);
        Ok(content_bytes)
    }

    fn rollback(self, state: &mut NnsRegistryReplayState) {
        for (key, original) in self.entries {
            state.entries.remove(&key);
            if let Some(value) = original {
                state.entries.insert(key, value);
            }
        }
        state.through_version = self.previous_version;
        state.content_bytes = self.previous_content_bytes;
    }
}

fn enforce_limits(
    state: &NnsRegistryReplayState,
    limits: NnsRegistryReplayLimits,
) -> Result<(), NnsRegistryReplayError> {
    enforce_limit("entry count", state.entries.len(), limits.max_entries)?;
    enforce_limit(
        "content bytes",
        state.content_bytes,
        limits.max_content_bytes,
    )
}

const fn enforce_limit(
    field: &'static str,
    actual: usize,
    maximum: usize,
) -> Result<(), NnsRegistryReplayError> {
    if actual > maximum {
        Err(NnsRegistryReplayError::LimitExceeded {
            field,
            maximum,
            actual,
        })
    } else {
        Ok(())
    }
}

fn decode_hex(field: &'static str, value: &str) -> Result<Vec<u8>, NnsRegistryReplayError> {
    if !value.len().is_multiple_of(2) || !crate::hex::is_lowercase_hex(value) {
        return Err(NnsRegistryReplayError::InvalidHex { field });
    }
    (0..value.len())
        .step_by(2)
        .map(|index| {
            u8::from_str_radix(&value[index..index + 2], 16)
                .map_err(|_| NnsRegistryReplayError::InvalidHex { field })
        })
        .collect()
}

#[cfg(test)]
mod tests;