freenet 0.2.110

use std::collections::BTreeMap;
use std::sync::RwLock;
use std::time::Duration;

use dashmap::DashMap;
use tokio::time::Instant;

use freenet_stdlib::prelude::*;

use crate::ring::PeerKeyLocation;
use crate::topology::rate::Rate;

use super::running_average::RunningAverage;

// Default usage is assumed to be the 50th percentile of usage for the resource.
const DEFAULT_USAGE_PERCENTILE: f64 = 0.5;

// Recache the estimated usage rate this often
const ESTIMATED_USAGE_RATE_CACHE_TIME: Duration = Duration::from_secs(60);

/// Hard ceiling on the number of distinct `AttributionSource` entries the
/// meter will retain at once.
///
/// `attribution_meters` is keyed by data that external actors influence
/// (peers we exchanged bytes with, contracts/delegates whose work we
/// executed). Per `.claude/rules/code-style.md` "NEVER use unbounded
/// per-key collections for data that external actors can influence" this
/// map must be size-bounded at insertion time. Peer churn is already
/// pruned by `retain_peer_sources`, but Contract/Delegate sources are
/// deliberately retained across that prune and would otherwise accumulate
/// one entry per distinct contract/delegate ever reported. The cap is the
/// backstop that bounds the worst case regardless of source variant.
///
/// Sized generously relative to a node's realistic concurrent-source
/// working set (live peers plus actively-executing contracts/delegates)
/// so legitimate traffic is never evicted, while still capping the map at
/// a few MB of running-average state.
///
/// Shared with [`crate::topology::TopologyManager::source_creation_times`],
/// which is keyed by the same `AttributionSource` and shares this meter's
/// lifecycle, so both bounded maps use one ceiling.
pub(crate) const MAX_ATTRIBUTION_SOURCES: usize = 4096;

/// Absolute age after which an attribution entry is eligible for eviction
/// regardless of the live-peer prune.
///
/// Per the AGENTS.md GC rule ("cleanup exemptions MUST be time-bounded"),
/// every entry carries an absolute-age threshold: an entry that has not
/// been reported against for longer than this is stale and can be dropped
/// on the next insertion that needs room. This is the TTL that keeps
/// Contract/Delegate sources — which `retain_peer_sources` intentionally
/// never prunes — from living forever after their last sample.
///
/// Shared with [`crate::topology::TopologyManager::source_creation_times`]
/// (same keyspace, same lifecycle) so both bounded maps age entries out on
/// the same schedule.
pub(crate) const ATTRIBUTION_SOURCE_TTL: Duration = Duration::from_secs(15 * 60);

// ---------------------------------------------------------------------------
// Cost-pressure per-axis floors + sustained window (#4861 Codex round-3).
//
// These MIRROR the authoritative constants in `ring/hosting/cache.rs`
// (`EXEC_CPU_PRESSURE_FLOOR_MICROS_PER_SEC`, `BROADCAST_FANOUT_PRESSURE_FLOOR_
// BYTES_PER_SEC`, `BROADCAST_MESSAGES_PRESSURE_FLOOR_PER_SEC`,
// `COST_RATE_MIN_WINDOW`). They cannot be imported: the `cache` module is
// private to `hosting`, which is itself private to `ring`, so the constants
// are not nameable from `topology::meter`. The insert-time above-floor
// sustained-run detection (`RunningAverage::new_cost_sustained`) needs the
// floor + window at sample time, on this side of that privacy boundary.
//
// The drift risk is closed by the guard test
// `ring::cost_pressure_seam_tests::meter_cost_floors_mirror_cache_source_of_truth`,
// which reads the authoritative cache.rs values (through `build_cost_axes`
// and the re-exported `COST_RATE_MIN_WINDOW`, both reachable from `ring`) and
// asserts they equal these mirrors — so CI fails if the two ever diverge.
// ---------------------------------------------------------------------------

/// Mirror of `cache::EXEC_CPU_PRESSURE_FLOOR_MICROS_PER_SEC`.
const EXEC_CPU_COST_FLOOR_MICROS_PER_SEC: f64 = 50_000.0;
/// Mirror of `cache::BROADCAST_FANOUT_PRESSURE_FLOOR_BYTES_PER_SEC`.
const BROADCAST_FANOUT_COST_FLOOR_BYTES_PER_SEC: f64 = 128.0 * 1024.0;
/// Mirror of `cache::BROADCAST_MESSAGES_PRESSURE_FLOOR_PER_SEC`.
const BROADCAST_MESSAGES_COST_FLOOR_PER_SEC: f64 = 10.0;
/// Mirror of `cache::COST_RATE_MIN_WINDOW`. `pub(crate)` so the `ring` guard
/// test can assert it equals the authoritative value.
pub(crate) const COST_SUSTAINED_WINDOW: Duration = Duration::from_secs(300);

/// Construct the [`RunningAverage`] for one `(source, resource)` cell.
/// Contract cost axes ([`ResourceType::cost_pressure_floor`] is `Some`) get
/// insert-time ABOVE-FLOOR sustained-run tracking (#4861 Codex round-3) so
/// their eviction-candidacy gate keys on sustained above-FLOOR cost rather
/// than mere sample continuity; every other axis keeps the plain running
/// average, behaviorally unchanged.
fn new_running_average(window_size: usize, resource: ResourceType) -> RunningAverage {
    match resource.cost_pressure_floor() {
        Some(floor) => {
            RunningAverage::new_cost_sustained(window_size, floor, COST_SUSTAINED_WINDOW)
        }
        None => RunningAverage::new(window_size),
    }
}

/// A structure that keeps track of the usage of dynamic resources which are consumed over time.
/// It provides methods to report and query resource usage, both total and attributed to specific
/// sources.
pub(crate) struct Meter {
    attribution_meters: AttributionMeters,
    running_average_window_size: usize,
    cached_estimated_usage_rate: RwLock<BTreeMap<ResourceType, (Rate, Instant)>>,
}

impl Meter {
    /// Creates a new `Meter`.
    pub fn new_with_window_size(running_average_window_size: usize) -> Self {
        Meter {
            attribution_meters: DashMap::new(),
            running_average_window_size,
            cached_estimated_usage_rate: RwLock::new(BTreeMap::new()),
        }
    }

    /// The measured usage rate for a resource attributed to a specific source.
    pub(crate) fn attributed_usage_rate(
        &self,
        attribution: &AttributionSource,
        resource: &ResourceType,
        at_time: Instant,
    ) -> Option<Rate> {
        match self.attribution_meters.get(attribution) {
            Some(attribution_meters) => {
                match attribution_meters.map.get(resource) {
                    Some(meter) => {
                        // Get the current measurement value
                        meter.get_rate_at_time(at_time)
                    }
                    None => Some(Rate::new(0.0, Duration::from_secs(1))), // No meter found for the given resource
                }
            }
            None => None, // No AttributionMeters found for the given attribution
        }
    }

    /// Returns the estimated usage rate for a resource of a given type.
    ///
    /// This function uses a percentile defined by `DEFAULT_USAGE_PERCENTILE` to estimate the usage rate
    /// for resources with unknown usage. It caches the estimated rates and refreshes them every
    /// `ESTIMATED_USAGE_RATE_CACHE_TIME` duration to avoid frequent recalculations.
    ///
    /// # Arguments
    ///
    /// * `resource` - A reference to the type of resource for which the usage rate is estimated.
    /// * `now` - The current `Instant` used to determine if the cached value is still valid.
    ///
    /// # Returns
    ///
    /// An `Option<Rate>` which is `Some(rate)` if an estimated rate is available, or `None` if it can't be determined.
    pub(crate) fn get_adjusted_usage_rate(
        &mut self,
        resource: &ResourceType,
        at_time: Instant,
    ) -> Option<Rate> {
        {
            let cache = self.cached_estimated_usage_rate.read().unwrap();
            if let Some((cached_rate, cached_time)) = cache.get(resource) {
                if at_time - *cached_time <= ESTIMATED_USAGE_RATE_CACHE_TIME {
                    return Some(*cached_rate);
                }
            }
        }

        match self.calculate_estimated_usage_rate(resource, at_time) {
            Some(estimated_usage_rate) => {
                let mut cache = self.cached_estimated_usage_rate.write().unwrap();
                cache.insert(*resource, (estimated_usage_rate, at_time));
                Some(estimated_usage_rate)
            }
            None => None,
        }
    }

    /// Returns a BTreeMap of AttributionSource to Rate of the usage rate for
    /// each attribution source. This does not adjust the usage rate for sources
    /// that are ramping up.
    pub(crate) fn get_usage_rates(
        &self,
        resource: &ResourceType,
        at_time: Instant,
    ) -> BTreeMap<AttributionSource, Rate> {
        let mut rates = BTreeMap::new();

        for entry in self.attribution_meters.iter() {
            if let Some(meter) = entry.value().map.get(resource) {
                if let Some(rate) = meter.get_rate_at_time(at_time) {
                    rates.insert(entry.key().clone(), rate);
                }
            }
        }

        rates
    }

    /// Per-CONTRACT attributed usage rates for one cost axis, plus their sum,
    /// for the cost-pressure eviction trigger (cost-aware eviction, #4861).
    ///
    /// Iterates the attribution meters, keeping only
    /// [`AttributionSource::Contract`] entries (peer/delegate bandwidth sources
    /// never participate in contract cost eviction), and reads each contract's
    /// rate via [`RunningAverage::windowed_rate`]: only samples within the
    /// last `min_window` participate (a source that stops reporting decays to
    /// nothing instead of holding a stale rate — review Fix 3), sparse
    /// samples are diluted over at least `min_window` (a lone burst cannot
    /// masquerade as a sustained storm), while a fully-recent saturated
    /// sample buffer divides by its actual span so a sustained high-frequency
    /// storm's TRUE rate is representable (the count-truncation under-read
    /// that hid the #4861 profile).
    ///
    /// Returns `(total_rate, per_contract_rate)` in axis units per second.
    /// EVERY positive-rate contract counts toward `total_rate` (the share
    /// denominator), but the per-contract map — the eviction CANDIDACY input —
    /// contains only contracts whose reporting is SUSTAINED: the source's
    /// current CONTINUOUS activity run must be at least `min_window / 2` long
    /// ([`crate::topology::running_average::WindowedRate::activity_span`]).
    /// That run length is buffer-CAPACITY-independent (tracked at insert time
    /// via `activity_start`), so it works at ANY report cadence above the
    /// floor — the fix for the review BLOCKER, where the old span-of-the-
    /// count-bounded-buffer signal INVERTED against high-frequency storms
    /// (fast cadence ⇒ short buffer span ⇒ never "sustained" ⇒ the worst
    /// storms were permanently exempted). A contract absent from the map has
    /// zero attributed cost for candidacy purposes, so a short burst — even a
    /// buffer-saturating one, and even on a source whose first-ever sample is
    /// arbitrarily old (a >`SUSTAINED_ACTIVITY_MAX_GAP` gap restarts the run)
    /// — can never make its contract a cost victim, no matter how big the
    /// burst.
    ///
    /// Single-axis convenience wrapper over [`Self::contract_cost_rates_multi`]
    /// for the unit tests; production reads all three cost axes in one pass via
    /// the multi form (#4903 review perf).
    #[cfg(test)]
    pub(crate) fn contract_cost_rates(
        &self,
        resource: &ResourceType,
        at_time: Instant,
        min_window: Duration,
    ) -> (f64, std::collections::HashMap<ContractInstanceId, f64>) {
        let mut out =
            self.contract_cost_rates_multi(std::slice::from_ref(resource), at_time, min_window);
        out.pop()
            .expect("exactly one result for one requested axis")
    }

    /// Multi-axis form of [`Self::contract_cost_rates`]: read SEVERAL cost
    /// axes in a SINGLE pass over the attribution meters, returning one
    /// `(total_rate, per_contract_rate)` per requested axis in the same order.
    ///
    /// The hosting sweep needs all three cost axes (CPU, fan-out bytes,
    /// broadcast messages) every tick; reading them with three separate
    /// [`Self::contract_cost_rates`] calls scanned the (potentially large)
    /// attribution-meter map three times under the topology read lock (#4903
    /// review perf). One pass amortizes the scan; the per-source windowing and
    /// the SUSTAINED continuous-run gate are identical to the single-axis form.
    pub(crate) fn contract_cost_rates_multi(
        &self,
        resources: &[ResourceType],
        at_time: Instant,
        min_window: Duration,
    ) -> Vec<(f64, std::collections::HashMap<ContractInstanceId, f64>)> {
        let sustained_min_span = min_window / 2;
        let mut results: Vec<(f64, std::collections::HashMap<ContractInstanceId, f64>)> = resources
            .iter()
            .map(|_| (0.0_f64, std::collections::HashMap::new()))
            .collect();
        if resources.is_empty() {
            return results;
        }
        for entry in self.attribution_meters.iter() {
            let AttributionSource::Contract(id) = entry.key() else {
                continue;
            };
            let source_map = &entry.value().map;
            for (i, resource) in resources.iter().enumerate() {
                let Some(avg) = source_map.get(resource) else {
                    continue;
                };
                let Some(windowed) = avg.windowed_rate(at_time, min_window) else {
                    continue;
                };
                let per_second = windowed.rate.per_second();
                if per_second > 0.0 {
                    results[i].0 += per_second;
                    if windowed.activity_span >= sustained_min_span {
                        results[i].1.insert(*id, per_second);
                    }
                }
            }
        }
        results
    }

    /// Estimates the usage rate for a given resource type based on existing data.
    ///
    /// This function calculates the estimated usage rate by taking the 50th percentile value (or another
    /// specified percentile defined by [DEFAULT_USAGE_PERCENTILE]) from the set of known rates for the
    /// specified resource type. It disregards resources with no known rate (which may leader to
    /// higher estimates).
    ///
    /// # Arguments
    ///
    /// * `resource` - A reference to the resource type for which the usage rate is to be estimated.
    ///
    /// # Returns
    ///
    /// An `Option<Rate>` which is `Some(rate)` if an estimated rate can be determined from available data,
    /// or `None` if no data is available for the given resource type.
    ///
    /// # Panics
    ///
    /// This function may panic if `DEFAULT_USAGE_PERCENTILE` is set to an invalid value that is not within
    /// the range [0.0, 1.0].
    fn calculate_estimated_usage_rate(
        &self,
        resource: &ResourceType,
        at_time: Instant,
    ) -> Option<Rate> {
        let rates: Vec<Rate> = self
            .attribution_meters
            .iter()
            // Filter out resources with no Rate and collect their rates
            .filter_map(|t| {
                t.value()
                    .map
                    .get(resource)
                    .and_then(|m| m.get_rate_at_time(at_time))
            })
            .collect();

        if rates.is_empty() {
            return None;
        }

        // Sort the collected rates
        let mut sorted_rates = rates;
        sorted_rates.sort_unstable(); // Using sort_unstable for potentially better performance

        // Calculate the index for the estimated usage rate
        let percentile_index =
            (DEFAULT_USAGE_PERCENTILE * sorted_rates.len() as f64).round() as usize;
        let estimated_index = percentile_index.min(sorted_rates.len().saturating_sub(1));

        sorted_rates.get(estimated_index).cloned()
    }

    /// Drop the per-source meters for every `AttributionSource::Peer` whose
    /// inner `PeerKeyLocation` is NOT in `live`. Non-`Peer` sources (Contract,
    /// Delegate) are always retained — only the peer-attributed bandwidth
    /// samples are bounded by the live connection set.
    ///
    /// Without this, a peer that ever exchanged bytes leaves a permanent entry
    /// in `attribution_meters`, so under connection churn the map (and the
    /// per-tick work that iterates it) grows without bound. See #3453 review.
    pub(crate) fn retain_peer_sources(&self, live: &std::collections::HashSet<PeerKeyLocation>) {
        self.attribution_meters.retain(|source, _| match source {
            AttributionSource::Peer(peer) => live.contains(peer),
            // Non-peer sources are not bounded by the live connection set;
            // enumerated explicitly (not `_`) so a future AttributionSource
            // variant must consciously decide its retention policy here.
            AttributionSource::Delegate(_) | AttributionSource::Contract(_) => true,
        });
    }

    /// Report the use of a resource. This should be done in the lowest-level
    /// functions that consume the resource, taking an AttributionMeter
    /// as a parameter.
    ///
    /// Takes `&self`: the underlying [`DashMap`] provides per-shard interior
    /// mutability (per `.claude/rules/code-style.md` — DashMap over
    /// `RwLock<HashMap>`).
    ///
    /// NOTE: this method does not yet deliver concurrent reporting in
    /// production. The sole caller, `Ring::report_contract_resource_usage`,
    /// still holds the outer `RwLock<TopologyManager>` write guard across
    /// this call (see `ring.rs`), so reporters serialize on that coarse lock
    /// regardless of the DashMap's per-shard locking. The DashMap swap is
    /// groundwork; relieving that outer-lock contention requires decoupling
    /// the contract meter from `TopologyManager` (the TopologyMeter /
    /// GovernanceMeter split tracked in #4276) and is a separate change.
    pub(crate) fn report(
        &self,
        attribution: &AttributionSource,
        resource: ResourceType,
        value: f64,
        at_time: Instant,
    ) {
        // Hot path (existing source) is a SINGLE shard acquisition: take the
        // `entry()` once and, when the source already exists, record the
        // sample inline under that one guard. The eviction scan must NOT run
        // while an entry guard is held (it `retain`s/`remove`s across keys on
        // the same DashMap → self-deadlock), so for a brand-new source we
        // drop the guard, run the bounded eviction, then re-acquire to insert.
        //
        // Bounding on the new-source path enforces the cap at insertion time
        // (code-style.md: per-key collections influenced by external actors
        // must be size-bounded at insertion). Reporting against an existing
        // source never grows the map, so the scan is skipped on the hot path.
        use dashmap::mapref::entry::Entry;
        let window_size = self.running_average_window_size;
        match self.attribution_meters.entry(attribution.clone()) {
            Entry::Occupied(mut occupied) => {
                let totals = occupied.get_mut();
                totals.last_reported = totals.last_reported.max(at_time);
                totals
                    .map
                    .entry(resource)
                    .or_insert_with(|| new_running_average(window_size, resource))
                    .insert_with_time(at_time, value);
                return;
            }
            // Drop the vacant guard without inserting; eviction needs an
            // unlocked map. We re-acquire the entry below after pruning.
            Entry::Vacant(_) => {}
        }

        self.evict_if_full(at_time);

        let mut totals = self
            .attribution_meters
            .entry(attribution.clone())
            .or_insert_with(|| ResourceTotals::new(at_time));
        totals.last_reported = totals.last_reported.max(at_time);
        totals
            .map
            .entry(resource)
            .or_insert_with(|| new_running_average(window_size, resource))
            .insert_with_time(at_time, value);
    }

    /// Make room for a new attribution source when the map is at capacity.
    ///
    /// Two-phase, both phases bounded by an absolute-age threshold so no
    /// entry can be exempted from eviction indefinitely (AGENTS.md GC rule):
    ///
    /// 1. Drop every entry whose last report is older than
    ///    [`ATTRIBUTION_SOURCE_TTL`]. This alone usually keeps the map well
    ///    under the cap for a healthy node.
    /// 2. If still at [`MAX_ATTRIBUTION_SOURCES`], evict the single
    ///    least-recently-reported entry (LRU) so the new source can be
    ///    inserted. Bounding by recency means a flood of new sources cannot
    ///    push the map past the cap.
    ///
    /// Note on the DashMap multi-key caveat (code-style.md): this is not an
    /// atomic read-modify-write across keys — TTL pruning and LRU selection
    /// only ever *remove* whole entries, and the subsequent insert in
    /// `report` is independent. No entry guard is held across the scan, so
    /// there is no self-deadlock risk.
    fn evict_if_full(&self, now: Instant) {
        // Phase 1: TTL prune.
        self.attribution_meters.retain(|_, totals| {
            now.saturating_duration_since(totals.last_reported) < ATTRIBUTION_SOURCE_TTL
        });

        if self.attribution_meters.len() < MAX_ATTRIBUTION_SOURCES {
            return;
        }

        // Phase 2: LRU eviction. Find the least-recently-reported key
        // without holding its guard across the removal.
        let oldest = self
            .attribution_meters
            .iter()
            .min_by_key(|entry| entry.value().last_reported)
            .map(|entry| entry.key().clone());
        if let Some(key) = oldest {
            self.attribution_meters.remove(&key);
        }
    }
}

/// What a resource sample is attributed to.
///
/// Peer and Delegate variants are the original cost-attribution targets.
/// Contract was added as part of contract-hardening: every WASM call,
/// state write, broadcast, and message decode that has a `ContractInstanceId`
/// in scope can attribute its cost both to the originating peer AND to
/// the contract, so the per-contract governance scoring can run on the
/// same meter infrastructure that previously only fed peer-side
/// load-shedding.
///
/// See `docs/design/contract-hardening.md` — "Shared governance module".
#[allow(dead_code)] // variants constructed incrementally as reporters are wired up
#[derive(Eq, Hash, PartialEq, Clone, Debug)]
pub(crate) enum AttributionSource {
    Peer(PeerKeyLocation),
    Delegate(DelegateKey),
    Contract(ContractInstanceId),
}

impl PartialOrd for AttributionSource {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl AttributionSource {
    /// Whether this source can plausibly contribute samples to the given
    /// resource type. Used to filter the `source_creation_times`
    /// iteration in `topology::extrapolated_usage` so a Contract source
    /// (which never produces bandwidth samples) doesn't get a phantom
    /// non-zero bandwidth rate synthesized for it during its 5-min
    /// ramp-up window — that synthesized rate would otherwise inflate
    /// the topology's perceived bandwidth usage and trigger spurious
    /// connection removals every time a contract is reported.
    pub(crate) fn contributes_to(&self, resource: &ResourceType) -> bool {
        use AttributionSource::*;
        use ResourceType::*;
        // Enumerate every (source, resource) pair explicitly so a future
        // ResourceType variant fails the match exhaustiveness check
        // instead of silently falling into a default. Codex re-reviewer
        // of PR #4260 flagged the `_ => false` wildcard as a foot-gun:
        // a new resource added without revisiting this predicate would
        // silently treat every source as non-contributing to it.
        match (self, resource) {
            // Peer sources produce the bandwidth samples that drive
            // topology load-shedding.
            (Peer(_), InboundBandwidthBytes) => true,
            (Peer(_), OutboundBandwidthBytes) => true,
            (Peer(_), ExecCpuMicros) => false,
            (Peer(_), ExecFuelUnits) => false,
            (Peer(_), StateBytesWritten) => false,
            (Peer(_), BroadcastFanoutCost) => false,
            (Peer(_), BroadcastMessagesSent) => false,
            // Delegate sources predate this PR; their existing usage
            // pattern is bandwidth-relevant for accounting purposes.
            (Delegate(_), InboundBandwidthBytes) => true,
            (Delegate(_), OutboundBandwidthBytes) => true,
            (Delegate(_), ExecCpuMicros) => false,
            (Delegate(_), ExecFuelUnits) => false,
            (Delegate(_), StateBytesWritten) => false,
            (Delegate(_), BroadcastFanoutCost) => false,
            (Delegate(_), BroadcastMessagesSent) => false,
            // Contract sources contribute the four contract-governance
            // resource types (CPU, fuel, state-bytes, fan-out cost) and
            // NEVER bandwidth — those are peer-attributed even when the
            // contract is the originator.
            (Contract(_), InboundBandwidthBytes) => false,
            (Contract(_), OutboundBandwidthBytes) => false,
            (Contract(_), ExecCpuMicros) => true,
            (Contract(_), ExecFuelUnits) => true,
            (Contract(_), StateBytesWritten) => true,
            (Contract(_), BroadcastFanoutCost) => true,
            (Contract(_), BroadcastMessagesSent) => true,
        }
    }
}

impl Ord for AttributionSource {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        // Variant discriminant defines the cross-variant ordering;
        // intra-variant comparisons use the inner key's natural ordering
        // (or its Debug formatting where the inner type doesn't implement
        // Ord — DelegateKey today, kept for cross-variant compat).
        fn rank(source: &AttributionSource) -> u8 {
            match source {
                AttributionSource::Peer(_) => 0,
                AttributionSource::Delegate(_) => 1,
                AttributionSource::Contract(_) => 2,
            }
        }
        match (self, other) {
            (AttributionSource::Peer(a), AttributionSource::Peer(b)) => a.cmp(b),
            (AttributionSource::Delegate(a), AttributionSource::Delegate(b)) => {
                // DelegateKey doesn't implement Ord; fall back to Debug.
                format!("{:?}", a).cmp(&format!("{:?}", b))
            }
            (AttributionSource::Contract(a), AttributionSource::Contract(b)) => a.cmp(b),
            (a, b) => rank(a).cmp(&rank(b)),
        }
    }
}

/// What kind of resource was consumed.
///
/// The first two variants (Inbound/OutboundBandwidthBytes) are the
/// peer-side cost dimensions used by `topology::adjust_topology` for
/// connection load-shedding.
///
/// The remaining variants were added for per-contract governance scoring:
/// CPU and fuel from WASM execution, on-disk state-write volume, and the
/// `Σ(subscriber × per-emit cost)` for state broadcast fan-out. Each is
/// reported alongside the corresponding `AttributionSource::Contract`
/// entry from the executor / runtime / broadcast pipeline.
#[derive(Eq, Hash, PartialEq, PartialOrd, Ord, Clone, Copy, Debug)]
pub(crate) enum ResourceType {
    InboundBandwidthBytes,
    OutboundBandwidthBytes,
    ExecCpuMicros,
    ExecFuelUnits,
    StateBytesWritten,
    BroadcastFanoutCost,
    /// Per-peer broadcast MESSAGES dispatched for a contract (count units,
    /// one per target per fan-out, one per targeted stale-peer heal). Added
    /// for cost-aware eviction (#4861): a tiny-payload contract fanning to
    /// many co-hosts at a high message RATE burns per-send overhead
    /// (syscall / encryption / queue work) that byte-denominated
    /// [`Self::BroadcastFanoutCost`] cannot see — 121-byte messages at storm
    /// frequency read as a negligible byte rate while dominating the node's
    /// real broadcast capacity. This axis counts sends, so N tiny sends
    /// register as N.
    BroadcastMessagesSent,
}

impl ResourceType {
    /// Resource types that participate in topology-side bandwidth
    /// capacity decisions (see `Limits::get` and
    /// `calculate_usage_proportion`). Non-bandwidth resources (CPU /
    /// fuel / state / fanout) are NOT included here: they are tracked
    /// by the meter for contract-governance purposes but have no
    /// rate-ceiling style limit configured.
    pub(crate) fn all() -> [ResourceType; 2] {
        [
            ResourceType::InboundBandwidthBytes,
            ResourceType::OutboundBandwidthBytes,
        ]
    }

    /// The cost-pressure floor (axis units per second) for the three contract
    /// COST axes, or `None` for every other resource. A cost axis's
    /// [`RunningAverage`] uses this floor to track a sustained ABOVE-FLOOR run
    /// at insert time (#4861 Codex round-3): its eviction-candidacy sustained
    /// signal counts only while the contract's true windowed rate stays at or
    /// above this floor, so a below-floor keep-alive trickle plus one dense
    /// burst never registers as sustained cost.
    ///
    /// Values MIRROR the authoritative `ring/hosting/cache.rs` floor constants
    /// (not importable across the private `hosting`/`cache` module boundary);
    /// the `ring` guard test `meter_cost_floors_mirror_cache_source_of_truth`
    /// fails CI if they drift. Enumerated exhaustively (no `_` arm) so a new
    /// `ResourceType` must consciously declare its floor, matching the
    /// [`AttributionSource::contributes_to`] discipline.
    pub(crate) fn cost_pressure_floor(&self) -> Option<f64> {
        match self {
            ResourceType::ExecCpuMicros => Some(EXEC_CPU_COST_FLOOR_MICROS_PER_SEC),
            ResourceType::BroadcastFanoutCost => Some(BROADCAST_FANOUT_COST_FLOOR_BYTES_PER_SEC),
            ResourceType::BroadcastMessagesSent => Some(BROADCAST_MESSAGES_COST_FLOOR_PER_SEC),
            ResourceType::InboundBandwidthBytes
            | ResourceType::OutboundBandwidthBytes
            | ResourceType::ExecFuelUnits
            | ResourceType::StateBytesWritten => None,
        }
    }

    /// Every resource type the meter understands, including non-bandwidth
    /// resources added for contract governance.
    #[allow(dead_code)] // wired up incrementally by per-resource-type reporters
    pub(crate) fn all_tracked() -> [ResourceType; 7] {
        [
            ResourceType::InboundBandwidthBytes,
            ResourceType::OutboundBandwidthBytes,
            ResourceType::ExecCpuMicros,
            ResourceType::ExecFuelUnits,
            ResourceType::StateBytesWritten,
            ResourceType::BroadcastFanoutCost,
            ResourceType::BroadcastMessagesSent,
        ]
    }
}

type AttributionMeters = DashMap<AttributionSource, ResourceTotals>;

/// A structure that holds running averages of resource usage for different resource types.
struct ResourceTotals {
    pub map: BTreeMap<ResourceType, RunningAverage>,
    /// Most recent time this source was reported against. Drives the TTL +
    /// LRU eviction in [`Meter::evict_if_full`] so a source that stops
    /// producing samples eventually ages out of the bounded map.
    last_reported: Instant,
}

impl ResourceTotals {
    fn new(at_time: Instant) -> Self {
        ResourceTotals {
            map: BTreeMap::new(),
            last_reported: at_time,
        }
    }
}

// Tests
#[cfg(test)]
mod tests {

    use super::*;

    #[test]
    fn test_empty_meter() {
        let meter = Meter::new_with_window_size(100);

        assert!(
            meter
                .attributed_usage_rate(
                    &AttributionSource::Peer(PeerKeyLocation::random()),
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now(),
                )
                .is_none()
        );
        assert!(meter.attribution_meters.is_empty());
    }

    fn contract_source(byte: u8) -> AttributionSource {
        AttributionSource::Contract(ContractInstanceId::new([byte; 32]))
    }

    #[test]
    fn test_meter_attributed_usage() {
        let meter = Meter::new_with_window_size(100);

        // Test that the attributed usage is 0.0 for all resources
        let attribution = AttributionSource::Peer(PeerKeyLocation::random());
        assert!(
            meter
                .attributed_usage_rate(
                    &attribution,
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now()
                )
                .is_none()
        );
        assert!(
            meter
                .attributed_usage_rate(
                    &attribution,
                    &ResourceType::OutboundBandwidthBytes,
                    Instant::now()
                )
                .is_none()
        );

        // Report some usage and test that the attributed usage is updated
        meter.report(
            &attribution,
            ResourceType::InboundBandwidthBytes,
            100.0,
            Instant::now(),
        );
        assert_eq!(
            meter
                .attributed_usage_rate(
                    &attribution,
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now()
                )
                .unwrap()
                .per_second(),
            100.0
        );
    }

    #[test]
    fn test_meter_report() -> anyhow::Result<()> {
        let meter = Meter::new_with_window_size(100);

        // Report some usage and test that the total and attributed usage are updated
        let attribution = AttributionSource::Peer(PeerKeyLocation::random());
        meter.report(
            &attribution,
            ResourceType::InboundBandwidthBytes,
            100.0,
            Instant::now(),
        );
        assert_eq!(
            meter
                .attributed_usage_rate(
                    &attribution,
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now()
                )
                .unwrap()
                .per_second(),
            100.0
        );

        // Report more usage and test that the total and attributed usage are updated
        meter.report(
            &attribution,
            ResourceType::InboundBandwidthBytes,
            200.0,
            Instant::now(),
        );
        assert_eq!(
            meter
                .attributed_usage_rate(
                    &attribution,
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now()
                )
                .unwrap()
                .per_second(),
            300.0
        );

        // Report usage for a different attribution and test that the total and attributed usage are updated
        let other_attribution = AttributionSource::Peer(PeerKeyLocation::random());
        meter.report(
            &other_attribution,
            ResourceType::InboundBandwidthBytes,
            150.0,
            Instant::now(),
        );
        assert_eq!(
            meter
                .attributed_usage_rate(
                    &other_attribution,
                    &ResourceType::InboundBandwidthBytes,
                    Instant::now()
                )
                .unwrap()
                .per_second(),
            150.0
        );
        Ok(())
    }

    /// `contract_cost_rates` (cost-aware eviction, #4861) aggregates ONLY
    /// Contract-attributed sources; samples older than the minimum window are
    /// ignored (a quiet source decays — review Fix 3); sparse samples are
    /// amortized over the minimum window (a lone burst cannot masquerade as a
    /// sustained storm); a fully-recent SATURATED sample buffer reads its
    /// true rate over its actual span (the count-truncation fix — without it
    /// a sustained high-frequency storm's rate is capped at
    /// samples×value/window and can hide under the floor); and the
    /// per-contract candidacy map admits only SUSTAINED sources (a continuous
    /// activity run of at least half the window — the buffer-capacity-
    /// independent `activity_span`, #4903 review BLOCKER) while every positive
    /// rate still counts toward the total.
    #[test]
    fn contract_cost_rates_aggregates_contract_sources_with_min_window() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);
        let now = t0 + Duration::from_secs(600);

        // Sparse source: two 30_000µs samples over 10 minutes. Only the
        // second falls within the last `min_window` of the read.
        meter.report(
            &contract_source(1),
            ResourceType::ExecCpuMicros,
            30_000.0,
            t0,
        );
        meter.report(
            &contract_source(1),
            ResourceType::ExecCpuMicros,
            30_000.0,
            t0 + Duration::from_secs(590),
        );
        // Burst source: one huge sample 1s before the read.
        meter.report(
            &contract_source(2),
            ResourceType::ExecCpuMicros,
            30_000_000.0,
            now - Duration::from_secs(1),
        );
        // Peer (bandwidth) source: must be excluded entirely.
        meter.report(
            &AttributionSource::Peer(PeerKeyLocation::random()),
            ResourceType::InboundBandwidthBytes,
            999_999.0,
            t0,
        );
        // Saturated high-frequency source on a different axis: 150 samples of
        // 58 messages at 1.6s cadence (storm profile). The ring keeps the last
        // 100, spanning ~158.4s.
        for i in 0..150u64 {
            meter.report(
                &contract_source(3),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + Duration::from_millis(1600 * i),
            );
        }
        let msgs_now = t0 + Duration::from_millis(1600 * 149) + Duration::from_secs(1);

        let (cpu_total, cpu_rates) =
            meter.contract_cost_rates(&ResourceType::ExecCpuMicros, now, min_window);
        let id1 = ContractInstanceId::new([1u8; 32]);
        let id2 = ContractInstanceId::new([2u8; 32]);
        // Sparse source: the t0 sample is older than the window and ignored
        // (review Fix 3), leaving one within-window sample — diluted over the
        // window (30_000/300s = 100/s) and NOT sustained (the >max-gap silence
        // between the two samples restarts the run, so activity_span is 0), so
        // it counts toward the total but is no candidacy entry.
        assert!(
            !cpu_rates.contains_key(&id1),
            "a lone within-window sample must not be a candidate"
        );
        // Burst source: counted in the TOTAL (diluted over min_window: 30M/300s
        // = 100_000/s) but EXCLUDED from the candidacy map (activity run ~0s —
        // not sustained), so one burst can never nominate a victim.
        assert!(
            !cpu_rates.contains_key(&id2),
            "burst must not be a candidate"
        );
        let expected_total = 30_000.0 / 300.0 + 30_000_000.0 / 300.0;
        assert!((cpu_total - expected_total).abs() < 1e-6);

        // Saturated storm source: true rate over the RETAINED span (~158.4s),
        // NOT diluted to 100×58/300s ≈ 19.3/s. 100×58/158.4 ≈ 36.6/s.
        let (msgs_total, msgs_rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, msgs_now, min_window);
        let id3 = ContractInstanceId::new([3u8; 32]);
        let rate3 = msgs_rates[&id3];
        assert!(
            rate3 > 30.0,
            "saturated buffer must read the true storm rate (~36.6/s), got {rate3}/s"
        );
        assert!((msgs_total - rate3).abs() < 1e-9);
    }

    /// Review Fix 2 / BLOCKER regression: an OLD first-ever sample must not
    /// admit a later short burst into candidacy. The continuity gap-reset
    /// (a >`SUSTAINED_ACTIVITY_MAX_GAP` silence restarts the activity run)
    /// makes the burst's `activity_span` measure only the burst, so a
    /// buffer-saturating 60-second flurry after a long silence is not
    /// sustained — "a single burst can never make its contract a victim"
    /// holds for old-first-sample sources too.
    #[test]
    fn contract_cost_rates_old_first_sample_then_burst_is_not_a_candidate() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // First-ever sample, 10 minutes before the read.
        meter.report(
            &contract_source(1),
            ResourceType::BroadcastMessagesSent,
            58.0,
            t0,
        );
        // A 60-second buffer-saturating flurry just before the read: 120
        // samples at 0.5s cadence (the buffer keeps the last 100, spanning
        // ~49.5s — all recent, so the rate reads high).
        let burst_start = t0 + Duration::from_secs(540);
        for i in 0..120u64 {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                burst_start + Duration::from_millis(500 * i),
            );
        }
        let now = t0 + Duration::from_secs(601);

        let (total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        let id1 = ContractInstanceId::new([1u8; 32]);
        assert!(
            !rates.contains_key(&id1),
            "an old-first-sample source's short burst must NOT be a candidate \
             (the gap-reset restarts the run at the burst, activity_span ~50s \
             < min_window/2)"
        );
        assert!(
            total > 0.0,
            "the burst still counts toward the node total (share denominator)"
        );
    }

    /// Review Fix 3 / BLOCKER regression: a contract that stops reporting
    /// decays out of the cost read within a bounded time — it leaves the
    /// candidacy map first (after one `SUSTAINED_ACTIVITY_MAX_GAP` of silence
    /// its activity run is no longer current, `activity_span` → 0) and then
    /// stops inflating the node total entirely (once every sample ages past
    /// `min_window`), instead of holding its stale storm rate for as long as
    /// the count-bounded buffer retains old samples.
    #[test]
    fn contract_cost_rates_quiet_contract_decays_out_within_min_window() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);
        let id1 = ContractInstanceId::new([1u8; 32]);

        // The FX2j storm profile: 150 samples of 58 msgs at 1.6s cadence.
        for i in 0..150u64 {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + Duration::from_millis(1600 * i),
            );
        }
        let storm_end = t0 + Duration::from_millis(1600 * 149);

        // Live: a sustained candidate at its true rate.
        let (live_total, live_rates) = meter.contract_cost_rates(
            &ResourceType::BroadcastMessagesSent,
            storm_end + Duration::from_secs(1),
            min_window,
        );
        assert!(live_rates[&id1] > 30.0);
        assert!(live_total > 30.0);

        // After 180s of silence (longer than SUSTAINED_ACTIVITY_MAX_GAP) the
        // activity run is no longer current: no longer a CANDIDATE (even
        // though some rate remains in the total while recent samples linger).
        let (_, stale_rates) = meter.contract_cost_rates(
            &ResourceType::BroadcastMessagesSent,
            storm_end + Duration::from_secs(180),
            min_window,
        );
        assert!(
            !stale_rates.contains_key(&id1),
            "a quiet contract must drop out of candidacy once its activity run \
             goes stale"
        );

        // After a full min_window of silence every sample is stale: the
        // contract contributes NOTHING (no total inflation, no candidacy).
        let (gone_total, gone_rates) = meter.contract_cost_rates(
            &ResourceType::BroadcastMessagesSent,
            storm_end + min_window + Duration::from_secs(1),
            min_window,
        );
        assert!(gone_rates.is_empty());
        assert_eq!(
            gone_total, 0.0,
            "a source quiet for min_window must stop inflating total_rate"
        );
    }

    /// #4903 review BLOCKER regression: storms at ANY report cadence above the
    /// floor must nominate. The old sustained gate keyed on the span of the
    /// count-bounded sample buffer, which shrinks with cadence — a fast storm's
    /// 100-sample buffer spans only a few tens of seconds, far under
    /// `min_window / 2`, so the FASTEST (worst) storms were PERMANENTLY exempt.
    /// The continuity-tracked `activity_span` is buffer-capacity-independent,
    /// so a 1.4s-cadence storm AND a 0.5s-cadence storm (buffer span ~50s) both
    /// nominate.
    #[test]
    fn contract_cost_rates_fast_storm_cadences_nominate() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);
        let run = Duration::from_secs(220); // > min_window/2, continuous

        // id1: 1.4s cadence (just under the old [1.52s, 3.03s] catchable band).
        let mut t = Duration::ZERO;
        while t <= run {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + t,
            );
            t += Duration::from_millis(1400);
        }
        // id2: 0.5s cadence — the 100-sample buffer spans only ~50s, deep
        // inside the old inversion (never "sustained" under the buffer-span
        // gate), yet the run is 220s.
        let mut t = Duration::ZERO;
        while t <= run {
            meter.report(
                &contract_source(2),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + t,
            );
            t += Duration::from_millis(500);
        }

        let now = t0 + run + Duration::from_secs(1);
        let (_total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        let id1 = ContractInstanceId::new([1u8; 32]);
        let id2 = ContractInstanceId::new([2u8; 32]);
        assert!(
            rates.contains_key(&id1),
            "a 1.4s-cadence storm must be a candidate"
        );
        assert!(
            rates.contains_key(&id2),
            "a 0.5s-cadence storm (buffer span ~50s ≪ min_window/2) must STILL \
             be a candidate — the BLOCKER inversion is fixed"
        );
    }

    /// A storm whose cadence is IRREGULAR — a 1.6s fan-out interleaved with
    /// sporadic targeted stale-peer heal samples — is still one continuous run
    /// (every gap stays under `SUSTAINED_ACTIVITY_MAX_GAP`), so it nominates.
    #[test]
    fn contract_cost_rates_heal_interleaved_storm_nominates() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // 220s of fan-out at 1.6s, plus an extra heal sample at a jittered
        // offset every ~5th dispatch — irregular but never a >max-gap silence.
        let mut t = Duration::ZERO;
        let mut n = 0u64;
        while t <= Duration::from_secs(220) {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + t,
            );
            if n % 5 == 0 {
                meter.report(
                    &contract_source(1),
                    ResourceType::BroadcastMessagesSent,
                    1.0,
                    t0 + t + Duration::from_millis(700),
                );
            }
            n += 1;
            t += Duration::from_millis(1600);
        }

        let now = t0 + Duration::from_secs(221);
        let (_total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            rates.contains_key(&ContractInstanceId::new([1u8; 32])),
            "a heal-interleaved (irregular-cadence) storm must be a candidate"
        );
    }

    /// The `ExecCpuMicros` axis must be able to nominate a multi-target CPU
    /// storm. The send-time summarize/delta CPU is reported per PEER send, so a
    /// 58-target fan-out floods the axis with 58 samples per dispatch — under
    /// the old buffer-span gate that flood spanned only a couple of dispatches
    /// (< min_window/2) and could NEVER nominate. With `activity_span` the
    /// continuous run is what matters, so the CPU axis nominates.
    ///
    /// Per-sample CPU is 2000µs so the storm's true rate — 58 × 2000 / 1.6s ≈
    /// 72_500µs/s — clears the 50_000µs/s CPU floor: under the ABOVE-FLOOR
    /// sustained gate (#4861 Codex round-3) a candidate must sustain a rate at
    /// or above the axis floor, so the flood modeled here has to be a genuine
    /// above-floor storm, not a trickle of tiny samples that would (correctly)
    /// no longer qualify.
    #[test]
    fn contract_cost_rates_multi_target_cpu_flood_nominates() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // 120 dispatches at 1.6s (192s continuous); each dispatch reports 58
        // per-target CPU samples spread across the ~1s send window.
        let mut dispatch = Duration::ZERO;
        for _ in 0..120u64 {
            for target in 0..58u64 {
                meter.report(
                    &contract_source(1),
                    ResourceType::ExecCpuMicros,
                    2000.0,
                    t0 + dispatch + Duration::from_millis(15 * target),
                );
            }
            dispatch += Duration::from_millis(1600);
        }

        let now = t0 + dispatch + Duration::from_secs(1);
        let (total, rates) =
            meter.contract_cost_rates(&ResourceType::ExecCpuMicros, now, min_window);
        assert!(
            rates.contains_key(&ContractInstanceId::new([1u8; 32])),
            "a multi-target (58/dispatch) above-floor CPU flood must nominate \
             on the ExecCpuMicros axis"
        );
        assert!(total > 0.0);
    }

    /// Boundary: a single dense burst — even one that saturates the sample
    /// buffer — is NOT a candidate (its continuous run is short), though it
    /// still counts toward the total (share denominator).
    #[test]
    fn contract_cost_rates_single_dense_burst_never_nominates() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // 200 samples over 30s (saturates the 100-sample buffer), then read.
        for i in 0..200u64 {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + Duration::from_millis(150 * i),
            );
        }
        let now = t0 + Duration::from_secs(31);
        let (total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            !rates.contains_key(&ContractInstanceId::new([1u8; 32])),
            "a 30s dense burst must not be sustained (run < min_window/2)"
        );
        assert!(total > 0.0, "the burst still counts toward the total");
    }

    /// Boundary (#4903 review round-2 requirement): the 60s gap-reset must have
    /// generous headroom above ANY cadence that exceeds a floor, so a genuine
    /// sustained storm never spuriously resets its run. A contract reporting
    /// every 30s (well under the 60s gap threshold) is ONE continuous run and
    /// stays sustained: no spurious gap-reset.
    ///
    /// The 400-msgs-per-report value keeps the storm's true rate — 400 / 30s ≈
    /// 13/s — above the 10 msgs/s floor, as the ABOVE-FLOOR sustained gate
    /// (#4861 Codex round-3) requires: sustainedness is a sustained above-FLOOR
    /// run, so the reporter modeled here has to clear the floor at its 30s
    /// cadence for the "no spurious 30s gap-reset" property to be observable.
    #[test]
    fn contract_cost_rates_slow_cadence_does_not_gap_reset() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // Report every 30s (well under the 60s gap threshold) for 240s
        // continuous, at a per-report volume that clears the message floor.
        let mut t = Duration::ZERO;
        while t <= Duration::from_secs(240) {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                400.0,
                t0 + t,
            );
            t += Duration::from_secs(30);
        }
        let now = t0 + Duration::from_secs(241);
        let (_total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            rates.contains_key(&ContractInstanceId::new([1u8; 32])),
            "a continuous 30s-cadence reporter must stay one sustained run — the \
             60s gap threshold must not spuriously reset a sub-60s cadence"
        );
    }

    /// Boundary (#4903 review round-2 requirement): an INTERMITTENT burst
    /// pattern — a 3s storm, then 90s of silence, repeated — must NOT
    /// accumulate span across the silences. Each >60s gap restarts the run, so
    /// every burst's `activity_span` is only ~3s and the contract is NEVER
    /// sustained, no matter how many cycles run.
    #[test]
    fn contract_cost_rates_intermittent_bursts_do_not_accumulate_span() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);

        // Three cycles of {3s burst (7 samples @ 0.5s), 90s silence}.
        let cycle = Duration::from_secs(93);
        for c in 0..3u64 {
            let start = cycle * c as u32;
            for i in 0..7u64 {
                meter.report(
                    &contract_source(1),
                    ResourceType::BroadcastMessagesSent,
                    58.0,
                    t0 + start + Duration::from_millis(500 * i),
                );
            }
        }
        // Read right after the third burst (t0 + 186 + 3).
        let now = t0 + cycle * 2 + Duration::from_secs(4);
        let (total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            !rates.contains_key(&ContractInstanceId::new([1u8; 32])),
            "intermittent bursts separated by >60s silences must never become \
             sustained — span must not accumulate across the gaps"
        );
        assert!(
            total > 0.0,
            "the recent burst still counts toward the total"
        );
    }

    /// #4861 Codex round-3 (THE finding): a contract that emits trivial
    /// below-floor keep-alive samples CONTINUOUSLY (every 30s, under the 60s
    /// gap — so sample continuity is never broken) for longer than
    /// `min_window / 2`, then a SINGLE dense burst, must NOT be a candidate.
    /// The old sustained gate keyed on `activity_start` (sample continuity),
    /// which the no-gap trickle held alive for 180s+, so the lone burst's high
    /// saturated-buffer rate would nominate the contract on ONE burst —
    /// violating invariant 3's "a single burst never triggers". The above-floor
    /// gate tracks how long the TRUE rate has stayed at or above the axis
    /// floor, which the trickle never does, so the run only opens mid-burst and
    /// spans a few seconds (< min_window/2). Before the fix this assertion
    /// FAILS (the contract IS a candidate); after it passes.
    #[test]
    fn contract_cost_rates_trickle_then_single_burst_is_not_a_candidate() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);
        let id1 = ContractInstanceId::new([1u8; 32]);

        // Trickle: 0.1 msgs every 30s (< 60s gap, so sampling stays continuous;
        // 0.1/30s ≈ 0.003/s — far below the 10 msgs/s floor) for 180s.
        let mut t = Duration::ZERO;
        while t <= Duration::from_secs(180) {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                0.1,
                t0 + t,
            );
            t += Duration::from_secs(30);
        }
        // Then ONE dense burst (120 samples over ~3s — saturates the buffer and
        // reads a high true rate).
        let burst_start = t0 + Duration::from_secs(181);
        for i in 0..120u64 {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                burst_start + Duration::from_millis(25 * i),
            );
        }
        let now = burst_start + Duration::from_secs(4);

        let (total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            !rates.contains_key(&id1),
            "a continuous below-floor trickle then a SINGLE dense burst must \
             NOT be a candidate: sample continuity is sustained but above-FLOOR \
             cost is not (Codex round-3)"
        );
        assert!(
            total > 0.0,
            "the burst still counts toward the node total (share denominator)"
        );
    }

    /// The counterpart to the trickle-then-burst boundary: the SAME dense burst
    /// shape, but REPEATED continuously (above the floor throughout) for longer
    /// than `min_window / 2`, IS a candidate — this is genuine sustained
    /// above-floor cost, not a lone burst.
    #[test]
    fn contract_cost_rates_repeated_dense_bursts_above_floor_is_a_candidate() {
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let min_window = Duration::from_secs(300);
        let id1 = ContractInstanceId::new([1u8; 32]);

        // The 25ms-cadence dense burst of the test above, sustained for 200s:
        // ~2320 msgs/s (buffer-saturating), continuously above the 10/s floor.
        let mut i = 0u64;
        while Duration::from_millis(25 * i) <= Duration::from_secs(200) {
            meter.report(
                &contract_source(1),
                ResourceType::BroadcastMessagesSent,
                58.0,
                t0 + Duration::from_millis(25 * i),
            );
            i += 1;
        }
        let now = t0 + Duration::from_millis(25 * (i - 1)) + Duration::from_secs(1);

        let (_total, rates) =
            meter.contract_cost_rates(&ResourceType::BroadcastMessagesSent, now, min_window);
        assert!(
            rates.contains_key(&id1),
            "a dense burst sustained ABOVE the floor for > min_window/2 IS a \
             candidate (sustained above-floor cost)"
        );
    }

    #[test]
    fn test_eviction_skipped_below_cap() {
        // Boundary: a handful of distinct sources stays well under the cap,
        // so nothing is ever evicted and every entry remains queryable.
        let meter = Meter::new_with_window_size(100);
        let now = Instant::now();
        for i in 0..8u8 {
            meter.report(
                &contract_source(i),
                ResourceType::StateBytesWritten,
                1.0,
                now,
            );
        }
        assert_eq!(meter.attribution_meters.len(), 8);
        for i in 0..8u8 {
            assert!(
                meter
                    .attributed_usage_rate(
                        &contract_source(i),
                        &ResourceType::StateBytesWritten,
                        now
                    )
                    .is_some()
            );
        }
    }

    #[test]
    fn test_ttl_evicts_stale_source_on_insert() {
        // An entry older than the TTL is dropped the next time a NEW source
        // is inserted, even though the map is nowhere near the cap.
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let stale = contract_source(1);
        meter.report(&stale, ResourceType::StateBytesWritten, 1.0, t0);
        assert_eq!(meter.attribution_meters.len(), 1);

        // Report a different source far enough in the future that `stale`
        // has aged past ATTRIBUTION_SOURCE_TTL.
        let later = t0 + ATTRIBUTION_SOURCE_TTL + Duration::from_secs(1);
        let fresh = contract_source(2);
        meter.report(&fresh, ResourceType::StateBytesWritten, 1.0, later);

        assert!(!meter.attribution_meters.contains_key(&stale));
        assert!(meter.attribution_meters.contains_key(&fresh));
        assert_eq!(meter.attribution_meters.len(), 1);
    }

    #[test]
    fn test_ttl_refreshed_by_repeated_reports() {
        // A source reported against again resets its TTL, so it survives an
        // insert that would otherwise have aged it out.
        let meter = Meter::new_with_window_size(100);
        let t0 = Instant::now();
        let kept = contract_source(1);
        meter.report(&kept, ResourceType::StateBytesWritten, 1.0, t0);

        // Refresh just before the TTL would expire.
        let refresh = t0 + ATTRIBUTION_SOURCE_TTL - Duration::from_secs(1);
        meter.report(&kept, ResourceType::StateBytesWritten, 1.0, refresh);

        // New source inserted slightly later: `kept` was last reported at
        // `refresh`, which is still within the TTL window, so it stays.
        let later = refresh + Duration::from_secs(2);
        meter.report(
            &contract_source(2),
            ResourceType::StateBytesWritten,
            1.0,
            later,
        );

        assert!(meter.attribution_meters.contains_key(&kept));
    }

    #[test]
    fn test_cap_enforced_via_lru_eviction() {
        // Filling to the cap with fresh sources (so TTL never fires) and
        // inserting one more must evict exactly the least-recently-reported
        // entry, keeping the map at the cap rather than growing past it.
        let meter = Meter::new_with_window_size(100);
        let base = Instant::now();

        // Use distinct, monotonically increasing timestamps so there's an
        // unambiguous LRU victim. Keep within the TTL window so phase-1
        // pruning is a no-op and we exercise phase-2 (LRU) deterministically.
        for i in 0..MAX_ATTRIBUTION_SOURCES {
            let src = AttributionSource::Contract(ContractInstanceId::new(id_bytes(i as u32)));
            let at = base + Duration::from_millis(i as u64);
            meter.report(&src, ResourceType::StateBytesWritten, 1.0, at);
        }
        assert_eq!(meter.attribution_meters.len(), MAX_ATTRIBUTION_SOURCES);

        // The oldest (i == 0) is the LRU victim.
        let oldest = AttributionSource::Contract(ContractInstanceId::new(id_bytes(0)));
        let newcomer = AttributionSource::Contract(ContractInstanceId::new(id_bytes(
            MAX_ATTRIBUTION_SOURCES as u32,
        )));
        let at = base + Duration::from_millis(MAX_ATTRIBUTION_SOURCES as u64);
        meter.report(&newcomer, ResourceType::StateBytesWritten, 1.0, at);

        assert_eq!(meter.attribution_meters.len(), MAX_ATTRIBUTION_SOURCES);
        assert!(!meter.attribution_meters.contains_key(&oldest));
        assert!(meter.attribution_meters.contains_key(&newcomer));
    }

    #[test]
    fn test_combined_phase_ttl_prune_avoids_lru() {
        // Combined-phase boundary: the map is AT the cap, but every existing
        // entry is older than the TTL. Inserting a new source must drop the
        // stale entries in phase 1 (TTL prune), bringing the map below the
        // cap so phase 2 (LRU eviction of a live entry) is SKIPPED. The new
        // entry is then inserted into the now-small map.
        let meter = Meter::new_with_window_size(100);
        let base = Instant::now();

        // Fill exactly to the cap.
        for i in 0..MAX_ATTRIBUTION_SOURCES {
            let src = AttributionSource::Contract(ContractInstanceId::new(id_bytes(i as u32)));
            meter.report(&src, ResourceType::StateBytesWritten, 1.0, base);
        }
        assert_eq!(meter.attribution_meters.len(), MAX_ATTRIBUTION_SOURCES);

        // Report a new source far enough ahead that every existing entry is
        // past the TTL. Phase 1 should evict ALL of them, so the map ends
        // with just the newcomer — proving phase 2 did not run (it would
        // have left the map at the cap).
        let later = base + ATTRIBUTION_SOURCE_TTL + Duration::from_secs(1);
        let newcomer = AttributionSource::Contract(ContractInstanceId::new(id_bytes(
            MAX_ATTRIBUTION_SOURCES as u32,
        )));
        meter.report(&newcomer, ResourceType::StateBytesWritten, 1.0, later);

        assert_eq!(
            meter.attribution_meters.len(),
            1,
            "TTL prune should have dropped all stale entries before LRU ran"
        );
        assert!(meter.attribution_meters.contains_key(&newcomer));
    }

    /// Encode a u32 into a 32-byte contract-id array so each index maps to a
    /// distinct `ContractInstanceId` (the single-byte `[byte; 32]` helper
    /// only yields 256 distinct ids — not enough to reach the cap).
    fn id_bytes(i: u32) -> [u8; 32] {
        let mut bytes = [0u8; 32];
        bytes[0..4].copy_from_slice(&i.to_le_bytes());
        bytes
    }
}