mempill-types 0.2.0

//! Belief projection: derived, read-time types.
//!
//! `BeliefProjection` is never stored; it is recomputed on every `query_memory` call
//! by performing a canonical valid-time fold over the full claim and assertion history.

use crate::claim::{Confidence, Criticality, Fact};
use crate::identity::ClaimRef;
use crate::provenance::ProvenanceLabel;
use crate::time::{TransactionTime, ValidTime};

// Re-use Cardinality from claim — it's defined there per the design.
// belief.rs needs Fact, etc., so we import the types from the parent modules.

/// The read-time canonical belief projection.
///
/// Derived, never stored. Recomputed on every `query_memory` call by the TruthEngine
/// performing a canonical valid-time fold. No pre-computed "current value" row exists.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct BeliefProjection {
    /// The resolved belief status (Resolved, Contested, NoBelief, etc.).
    pub status: BeliefStatus,
    /// The claim covering NOW under the canonical fold, if unambiguous.
    pub primary: Option<Belief>,
    /// Both claims when Contested or Conflict (never silently picked).
    pub alternatives: Vec<Belief>,
    /// Derived currency state at read time: Fresh, AgingUnconfirmed, or Decayed.
    pub currency: CurrencyState,
    /// Criticality class of the primary claim, or the highest alternative when contested.
    pub criticality: Criticality,
    /// Computed staleness flag (is_stale = true when currency is Decayed or no reconfirmation).
    pub staleness: StalenessFlag,
    /// Active markers on the projection (Contested, PendingReview, AgedSetMember, etc.).
    pub markers: Vec<Marker>,
}

/// Resolved belief status for a subject-line at read time.
///
/// Produced by the canonical valid-time fold in `TruthEngine::query_memory`.
/// The status is authoritative: a `Contested` result means the conflict was
/// detected and surfaced explicitly, never silently resolved.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[non_exhaustive]
pub enum BeliefStatus {
    /// Single live truth.
    Resolved,
    /// External contradiction, oracle absent — conflict surfaces explicitly rather than being resolved silently.
    Contested,
    /// Multiple mutually-exclusive active beliefs.
    Conflict,
    /// Value known, but the valid-time window is unknown (caller did not supply valid-time).
    TimingUncertain,
    /// Subject-line exists but no currently-valid claim.
    NoBelief,
}

/// A single candidate belief — one arm of the canonical fold result.
///
/// A `BeliefProjection` has exactly one `primary` when `Resolved`, two entries in
/// `alternatives` when `Contested` or `Conflict`, and neither when `NoBelief`.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct Belief {
    /// Stable reference to the underlying committed claim.
    pub claim_ref: ClaimRef,
    /// The (subject, predicate, value) triple of the claim.
    pub fact: Fact,
    /// Provenance label: who asserted the claim and by what method.
    pub provenance: ProvenanceLabel,
    /// Valid-time window of the claim (when it holds in the world).
    pub valid_time: ValidTime,
    /// Transaction time: when the claim was written to the store.
    pub transaction_time: TransactionTime,
    /// Dual confidence scores (value confidence + valid-time extraction confidence).
    pub confidence: Confidence,
    /// Derived currency signal at read time (computed, never stored).
    pub currency_signal: CurrencySignal,
    /// Criticality class of this claim.
    pub criticality: Criticality,
}

/// Derived currency state at read time.
///
/// Computed from `(now - last_refreshed_at)` relative to configured aging thresholds.
/// Never stored — recomputed on every `query_memory` call.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[non_exhaustive]
pub enum CurrencyState {
    /// Within the configured freshness window.
    Fresh,
    /// Past the freshness threshold but not yet fully decayed.
    AgingUnconfirmed,
    /// Beyond the decay threshold — treat value as potentially stale.
    Decayed,
}

/// Currency signal — derived and decaying, refreshed only on provenance-independent restatement.
///
/// Currency is not stored; it is computed at read time from `(now - last_refreshed_at)`
/// relative to the configured aging thresholds. Claims that are not reconfirmed by an
/// independent source decay over time toward `AgingUnconfirmed` then `Decayed`.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct CurrencySignal {
    /// When this claim's currency was last refreshed (by a provenance-independent restatement).
    pub last_refreshed_at: TransactionTime,
    /// Computed decay state at read time (never stored; derived from now - last_refreshed_at).
    pub state: CurrencyState,
    /// Number of provenance-independent corroborating sources (confidence annotation only; not a gate).
    pub corroboration_count: u32,
}

/// Computed staleness flag on a `BeliefProjection`.
///
/// `is_stale` is set when currency is `Decayed` or when the engine's currency
/// aging thresholds have been exceeded without a provenance-independent reconfirmation.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
pub struct StalenessFlag {
    /// Whether the belief is considered stale at read time.
    pub is_stale: bool,
    /// Optional human-readable reason for the staleness determination.
    pub reason: Option<String>,
}

/// Active signal flags on a `BeliefProjection` at read time.
///
/// Multiple markers may be set simultaneously. Callers should inspect all markers,
/// not just the `status`, for full situational awareness.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[non_exhaustive]
pub enum Marker {
    /// The belief is in active contest (two or more unresolved conflicting claims).
    Contested,
    /// A conflict exists but neither claim is contested — pending oracle or evidence.
    PendingConflict,
    /// A parent claim was superseded; this claim is flagged for human review.
    PendingReview,
    /// Set member that has exceeded the currency decay threshold (aging signal).
    AgedSetMember,
    /// Claim origin includes RecallReEntry provenance.
    RecallTainted,
    /// Derivation depth exceeds the configured cap for currency boosts.
    LowDerivationAnchor,
}

/// History entry status for `query_history` — whether the claim is the current belief
/// or was superseded by a later one.
///
/// `Current` and `Superseded` are derived from `is_live` in the canonical fold result
/// so that `history()` and `recall()` always agree on which entry is current.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[non_exhaustive]
#[serde(rename_all = "PascalCase")]
pub enum HistoryEntryStatus {
    /// This claim is the live (current) belief at the time of the query.
    Current,
    /// This claim was superseded by a later claim on the same subject-line.
    Superseded,
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::Utc;

    #[test]
    fn belief_status_round_trip_serde() {
        let statuses = [
            BeliefStatus::Resolved,
            BeliefStatus::Contested,
            BeliefStatus::Conflict,
            BeliefStatus::TimingUncertain,
            BeliefStatus::NoBelief,
        ];
        for s in &statuses {
            let json = serde_json::to_string(s).unwrap();
            let back: BeliefStatus = serde_json::from_str(&json).unwrap();
            assert_eq!(s, &back);
        }
    }

    #[test]
    fn currency_state_round_trip_serde() {
        let states = [CurrencyState::Fresh, CurrencyState::AgingUnconfirmed, CurrencyState::Decayed];
        for s in &states {
            let json = serde_json::to_string(s).unwrap();
            let back: CurrencyState = serde_json::from_str(&json).unwrap();
            assert_eq!(s, &back);
        }
    }

    #[test]
    fn staleness_flag_not_stale() {
        let f = StalenessFlag { is_stale: false, reason: None };
        assert!(!f.is_stale);
        assert!(f.reason.is_none());
    }

    #[test]
    fn marker_round_trip_serde() {
        let marker = Marker::RecallTainted;
        let json = serde_json::to_string(&marker).unwrap();
        let back: Marker = serde_json::from_str(&json).unwrap();
        assert_eq!(marker, back);
    }

    #[test]
    fn currency_signal_round_trip_serde() {
        let sig = CurrencySignal {
            last_refreshed_at: TransactionTime(Utc::now()),
            state: CurrencyState::Fresh,
            corroboration_count: 3,
        };
        let json = serde_json::to_string(&sig).unwrap();
        let back: CurrencySignal = serde_json::from_str(&json).unwrap();
        assert_eq!(sig.corroboration_count, back.corroboration_count);
        assert_eq!(sig.state, back.state);
    }
}