canic-core 0.97.3

///
/// IcpRefillPolicyInput
///

#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub struct IcpRefillPolicyInput {
    pub requested_amount_e8s: u64,
    pub observed_xdr_permyriad_per_icp: Option<u64>,
    pub active_for_key: bool,
    pub cycles_funding_enabled: bool,
}

///
/// IcpRefillPolicyRules
///

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct IcpRefillPolicyRules {
    pub max_refill_e8s_per_call: u64,
    pub min_xdr_permyriad_per_icp: Option<u64>,
}

///
/// IcpRefillPolicyViolation
///

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum IcpRefillPolicyViolation {
    NotConfigured,
    CyclesFundingDisabled,
    AmountZero,
    MaxRefillPerCall {
        requested_e8s: u64,
        max_e8s: u64,
    },
    RateUnavailable {
        min_xdr_permyriad_per_icp: u64,
    },
    RateGateDenied {
        observed_xdr_permyriad_per_icp: u64,
        min_xdr_permyriad_per_icp: u64,
    },
    ConcurrentRefill,
}

/// Evaluate an operator-triggered canister-side refill request.
///
/// Manual refills are constrained by the configured cap, rate gate, funding
/// controls, and concurrency key.
pub const fn evaluate_manual_refill(
    policy: Option<&IcpRefillPolicyRules>,
    input: IcpRefillPolicyInput,
) -> Result<(), IcpRefillPolicyViolation> {
    let Some(policy) = policy else {
        return Err(IcpRefillPolicyViolation::NotConfigured);
    };

    evaluate_common(policy, input)
}

const fn evaluate_common(
    policy: &IcpRefillPolicyRules,
    input: IcpRefillPolicyInput,
) -> Result<(), IcpRefillPolicyViolation> {
    if !input.cycles_funding_enabled {
        return Err(IcpRefillPolicyViolation::CyclesFundingDisabled);
    }
    if input.requested_amount_e8s == 0 {
        return Err(IcpRefillPolicyViolation::AmountZero);
    }
    if input.requested_amount_e8s > policy.max_refill_e8s_per_call {
        return Err(IcpRefillPolicyViolation::MaxRefillPerCall {
            requested_e8s: input.requested_amount_e8s,
            max_e8s: policy.max_refill_e8s_per_call,
        });
    }
    if input.active_for_key {
        return Err(IcpRefillPolicyViolation::ConcurrentRefill);
    }
    if let Some(min_xdr_permyriad_per_icp) = policy.min_xdr_permyriad_per_icp {
        match input.observed_xdr_permyriad_per_icp {
            Some(observed_xdr_permyriad_per_icp)
                if observed_xdr_permyriad_per_icp >= min_xdr_permyriad_per_icp => {}
            Some(observed_xdr_permyriad_per_icp) => {
                return Err(IcpRefillPolicyViolation::RateGateDenied {
                    observed_xdr_permyriad_per_icp,
                    min_xdr_permyriad_per_icp,
                });
            }
            None => {
                return Err(IcpRefillPolicyViolation::RateUnavailable {
                    min_xdr_permyriad_per_icp,
                });
            }
        }
    }

    Ok(())
}

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

    fn policy() -> IcpRefillPolicyRules {
        IcpRefillPolicyRules {
            max_refill_e8s_per_call: 100_000_000,
            min_xdr_permyriad_per_icp: Some(40_000),
        }
    }

    fn input() -> IcpRefillPolicyInput {
        IcpRefillPolicyInput {
            requested_amount_e8s: 50_000_000,
            observed_xdr_permyriad_per_icp: Some(45_000),
            active_for_key: false,
            cycles_funding_enabled: true,
        }
    }

    #[test]
    fn manual_refill_allows_configured_request() {
        evaluate_manual_refill(Some(&policy()), input()).expect("manual refill");
    }

    #[test]
    fn refill_denies_amount_above_cap() {
        let mut input = input();
        input.requested_amount_e8s = 100_000_001;

        let err = evaluate_manual_refill(Some(&policy()), input).expect_err("cap violation");

        assert_eq!(
            err,
            IcpRefillPolicyViolation::MaxRefillPerCall {
                requested_e8s: 100_000_001,
                max_e8s: 100_000_000,
            }
        );
    }

    #[test]
    fn refill_denies_missing_rate_when_gate_configured() {
        let mut input = input();
        input.observed_xdr_permyriad_per_icp = None;

        let err = evaluate_manual_refill(Some(&policy()), input).expect_err("rate required");

        assert_eq!(
            err,
            IcpRefillPolicyViolation::RateUnavailable {
                min_xdr_permyriad_per_icp: 40_000,
            }
        );
    }

    #[test]
    fn refill_denies_low_rate() {
        let mut input = input();
        input.observed_xdr_permyriad_per_icp = Some(39_999);

        let err = evaluate_manual_refill(Some(&policy()), input).expect_err("rate too low");

        assert_eq!(
            err,
            IcpRefillPolicyViolation::RateGateDenied {
                observed_xdr_permyriad_per_icp: 39_999,
                min_xdr_permyriad_per_icp: 40_000,
            }
        );
    }

    #[test]
    fn refill_denies_concurrent_key() {
        let mut input = input();
        input.active_for_key = true;

        let err = evaluate_manual_refill(Some(&policy()), input).expect_err("concurrent refill");

        assert_eq!(err, IcpRefillPolicyViolation::ConcurrentRefill);
    }

    #[test]
    fn manual_refill_denies_when_cycles_funding_disabled() {
        let mut input = input();
        input.cycles_funding_enabled = false;

        let err = evaluate_manual_refill(Some(&policy()), input).expect_err("kill switch");

        assert_eq!(err, IcpRefillPolicyViolation::CyclesFundingDisabled);
    }
}