parlov-elicit 0.5.0

//! `UniquenessElicitation` -- probes with a body that triggers a uniqueness conflict.
//!
//! Sends a JSON body containing a known-duplicate field value (from `ctx.known_duplicate`)
//! on both baseline and probe requests. The oracle signal is the server returning 409
//! versus 404 for a nonexistent one.

use http::Method;
use parlov_core::{
    Applicability, NormativeStrength, OracleClass, ResponseSurface, SignalSurface, Technique,
    Vector,
};

use crate::strategy::Strategy;
use crate::types::{ProbeSpec, RiskLevel, StrategyMetadata};
use crate::util::{build_pair, clone_headers_static, json_body};
use crate::ScanContext;

static METADATA: StrategyMetadata = StrategyMetadata {
    strategy_id: "uniqueness-elicit",
    strategy_name: "Uniqueness Elicitation",
    risk: RiskLevel::OperationDestructive,
};

/// `Strong` for 409 (Conflict) or 422 (Unprocessable Entity); `Weak` otherwise.
///
/// Body-content discrimination is intentionally not consulted — status code is enough to
/// confirm the uniqueness check ran.
fn uniqueness_applicable(baseline: &ResponseSurface, probe: &ResponseSurface) -> Applicability {
    let is_strong = |s: u16| matches!(s, 409 | 422);
    if is_strong(baseline.status.as_u16()) || is_strong(probe.status.as_u16()) {
        return Applicability::Strong;
    }
    Applicability::Weak
}

static TECHNIQUE: Technique = Technique {
    id: "uniqueness",
    name: "Uniqueness conflict probe",
    oracle_class: OracleClass::Existence,
    vector: Vector::StatusCodeDiff,
    strength: NormativeStrength::May,
    normalization_weight: Some(0.05),
    inverted_signal_weight: None,
    method_relevant: false,
    parser_relevant: true,
    applicability: uniqueness_applicable,
    contradiction_surface: SignalSurface::Status,
};

/// Elicits existence differentials via a uniqueness-conflict body payload.
pub struct UniquenessElicitation;

impl Strategy for UniquenessElicitation {
    fn metadata(&self) -> &'static StrategyMetadata {
        &METADATA
    }

    fn technique_def(&self) -> &'static Technique {
        &TECHNIQUE
    }

    fn methods(&self) -> &[Method] {
        &[Method::POST, Method::PUT]
    }

    fn is_applicable(&self, ctx: &ScanContext) -> bool {
        ctx.known_duplicate.is_some()
    }

    fn generate(&self, ctx: &ScanContext) -> Vec<ProbeSpec> {
        let Some(kd) = &ctx.known_duplicate else {
            return vec![];
        };
        let body = Some(json_body(&[(&kd.field, &kd.value)]));
        let headers = clone_headers_static(&ctx.headers, "content-type", "application/json");
        let mut specs = Vec::with_capacity(2);
        for method in [Method::POST, Method::PUT] {
            let pair = build_pair(
                ctx,
                method,
                headers.clone(),
                headers.clone(),
                body.clone(),
                METADATA.clone(),
                TECHNIQUE,
            );
            specs.push(ProbeSpec::Pair(pair));
        }
        specs
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test_utils::{ctx_operation_destructive, ctx_with_duplicate};

    #[test]
    fn risk_is_operation_destructive() {
        assert_eq!(
            UniquenessElicitation.risk(),
            RiskLevel::OperationDestructive
        );
    }

    #[test]
    fn is_applicable_false_when_known_duplicate_none() {
        assert!(!UniquenessElicitation.is_applicable(&ctx_operation_destructive()));
    }

    #[test]
    fn is_applicable_true_when_known_duplicate_some() {
        assert!(UniquenessElicitation.is_applicable(&ctx_with_duplicate()));
    }

    #[test]
    fn generate_returns_two_items_when_applicable() {
        assert_eq!(
            UniquenessElicitation.generate(&ctx_with_duplicate()).len(),
            2
        );
    }

    #[test]
    fn probe_body_contains_duplicate_field() {
        let specs = UniquenessElicitation.generate(&ctx_with_duplicate());
        let ProbeSpec::Pair(pair) = &specs[0] else {
            panic!("expected Pair")
        };
        let body = pair.probe.body.as_deref().expect("body must be present");
        let parsed: serde_json::Value = serde_json::from_slice(body).expect("valid JSON");
        assert_eq!(parsed["email"], "alice@example.com");
    }

    #[test]
    fn technique_strength_is_may() {
        let specs = UniquenessElicitation.generate(&ctx_with_duplicate());
        assert_eq!(specs[0].technique().strength, NormativeStrength::May);
    }

    #[test]
    fn normalization_weight_is_0_05() {
        assert_eq!(TECHNIQUE.normalization_weight, Some(0.05));
    }

    #[test]
    fn inverted_signal_weight_is_none() {
        assert_eq!(TECHNIQUE.inverted_signal_weight, None);
    }
}