parlov-elicit 0.5.0

//! `StateTransitionElicitation` -- probes with a body triggering an invalid state transition.
//!
//! Sends a JSON body containing a known-invalid field value (from `ctx.state_field`)
//! on both baseline and probe requests. The oracle signal is the server returning
//! 409 for an existing resource 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: "state-transition-elicit",
    strategy_name: "State Transition Elicitation",
    risk: RiskLevel::MethodDestructive,
};

/// Confirms the domain state machine evaluated the transition.
/// `Strong` for 409 (Conflict) or 422 (Unprocessable Entity); `Weak` otherwise.
fn state_transition_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: "state-transition",
    name: "Invalid state transition probe",
    oracle_class: OracleClass::Existence,
    vector: Vector::StatusCodeDiff,
    strength: NormativeStrength::May,
    normalization_weight: Some(0.02),
    inverted_signal_weight: None,
    method_relevant: false,
    parser_relevant: true,
    applicability: state_transition_applicable,
    contradiction_surface: SignalSurface::Status,
};

/// Elicits existence differentials via an invalid state-transition body payload.
pub struct StateTransitionElicitation;

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

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

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

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

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

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

    #[test]
    fn risk_is_method_destructive() {
        assert_eq!(
            StateTransitionElicitation.risk(),
            RiskLevel::MethodDestructive
        );
    }

    #[test]
    fn is_applicable_false_when_state_field_none() {
        assert!(!StateTransitionElicitation.is_applicable(&ctx_method_destructive()));
    }

    #[test]
    fn is_applicable_true_when_state_field_some() {
        assert!(StateTransitionElicitation.is_applicable(&ctx_with_state_field()));
    }

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

    #[test]
    fn probe_body_contains_state_field_as_valid_json() {
        let specs = StateTransitionElicitation.generate(&ctx_with_state_field());
        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["status"], "invalid_state");
    }

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

    #[test]
    fn normalization_weight_is_0_02() {
        assert_eq!(TECHNIQUE.normalization_weight, Some(0.02));
    }

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