heddle-api 0.31.0-alpha.3

//! Terminal stream failures belong to the wire contract, independent of a host.

use crate::heddle::api::common::{
    AccountBillingLock, AccountBillingLockReason, CallFailure, CursorFailure, ErrorDetail,
    ErrorReason, PolicyDenial, RetryAdvice, StreamFailure, error_detail,
};
use prost::Message;

/// Stable policy identifier for the account billing lock.
pub const ACCOUNT_BILLING_LOCK_POLICY_ID: &str = "account_locked_billing";

/// Builds the single structured error detail used for an account billing-lock
/// denial. Hosts attach this detail to a `FAILED_PRECONDITION` failure.
pub fn account_billing_lock_error_detail(
    resource: impl Into<String>,
    billing_lock: AccountBillingLock,
) -> ErrorDetail {
    let rule = match AccountBillingLockReason::try_from(billing_lock.reason) {
        Ok(AccountBillingLockReason::OverFreeCapWithoutPaidPlan) => {
            "over_free_cap_without_paid_plan"
        }
        _ => "account_billing_lock",
    };
    ErrorDetail {
        reason: ErrorReason::PolicyDenied as i32,
        resource: resource.into(),
        field: String::new(),
        context: Some(error_detail::Context::Policy(PolicyDenial {
            policy_id: ACCOUNT_BILLING_LOCK_POLICY_ID.to_owned(),
            rule: rule.to_owned(),
            human_verification_can_override: false,
            billing_lock: Some(Box::new(billing_lock)),
        })),
    }
}

/// Returns the typed lock from a policy denial, rejecting details with a
/// different reason, policy identifier, or context arm.
pub fn account_billing_lock_from_error_detail(detail: &ErrorDetail) -> Option<&AccountBillingLock> {
    if detail.reason != ErrorReason::PolicyDenied as i32 {
        return None;
    }
    let error_detail::Context::Policy(policy) = detail.context.as_ref()? else {
        return None;
    };
    if policy.policy_id != ACCOUNT_BILLING_LOCK_POLICY_ID {
        return None;
    }
    policy.billing_lock.as_deref()
}

/// Encodes a complete account billing-lock `ErrorDetail` for transport.
pub fn encode_account_billing_lock_error_detail(
    resource: impl Into<String>,
    billing_lock: AccountBillingLock,
) -> Vec<u8> {
    account_billing_lock_error_detail(resource, billing_lock).encode_to_vec()
}

/// Decodes a transported `ErrorDetail` and extracts its account billing lock.
/// A valid non-billing detail returns `Ok(None)`.
pub fn decode_account_billing_lock_error_detail(
    encoded: &[u8],
) -> Result<Option<AccountBillingLock>, prost::DecodeError> {
    let detail = ErrorDetail::decode(encoded)?;
    Ok(account_billing_lock_from_error_detail(&detail).cloned())
}

impl CallFailure {
    /// Preserve the original failure inside the terminal stream context.
    /// Explicit retry advice takes precedence over a cursor, then existing detail.
    pub fn into_stream_failure(
        mut self,
        retry: Option<RetryAdvice>,
        cursor: Option<CursorFailure>,
    ) -> Self {
        if retry.is_none()
            && cursor.is_none()
            && matches!(
                self.error.as_ref().and_then(|error| error.context.as_ref()),
                Some(error_detail::Context::Stream(_))
            )
        {
            return self;
        }
        let hint = retry
            .map(|retry| (ErrorReason::Transient, error_detail::Context::Retry(retry)))
            .or_else(|| {
                cursor.map(|cursor| {
                    (
                        ErrorReason::CursorInvalid,
                        error_detail::Context::Cursor(cursor),
                    )
                })
            });
        let nested = match hint {
            Some((reason, context)) => Some(ErrorDetail {
                reason: reason as i32,
                context: Some(context),
                ..Default::default()
            }),
            None => self.error.take(),
        };
        // The protobuf error graph is recursive; its generated fields require Box.
        self.error = Some(ErrorDetail {
            reason: nested
                .as_ref()
                .map_or(ErrorReason::Unspecified as i32, |error| error.reason),
            resource: nested
                .as_ref()
                .map(|error| error.resource.clone())
                .unwrap_or_default(),
            field: nested
                .as_ref()
                .map(|error| error.field.clone())
                .unwrap_or_default(),
            context: Some(error_detail::Context::Stream(Box::new(StreamFailure {
                code: self.code,
                message: self.message.clone(),
                error: nested.map(Box::new),
            }))),
        });
        self
    }
}

#[cfg(test)]
mod tests {
    use crate::heddle::api::common::{
        CallFailure, CallFailureCode, CursorFailure, ErrorDetail, ErrorReason, PolicyDenial,
        RetryAdvice, error_detail,
    };
    use prost::Message;

    #[test]
    fn terminal_failure_preserves_policy_and_is_idempotent_on_the_wire() {
        let detail = ErrorDetail {
            reason: ErrorReason::PolicyDenied as i32,
            resource: "spool:owner/private".into(),
            field: "sharing_policy".into(),
            context: Some(error_detail::Context::Policy(PolicyDenial {
                policy_id: "thread.sharing".into(),
                rule: "sharing revoked".into(),
                human_verification_can_override: false,
                billing_lock: None,
            })),
        };
        let failure = CallFailure {
            code: CallFailureCode::PermissionDenied as i32,
            message: "sharing revoked".into(),
            error: Some(detail.clone()),
        }
        .into_stream_failure(None, None);
        let encoded = failure.encode_to_vec();
        assert_eq!(
            encoded,
            failure
                .clone()
                .into_stream_failure(None, None)
                .encode_to_vec()
        );
        let restored = CallFailure::decode(encoded.as_slice()).expect("decode terminal frame");
        assert_eq!(restored.code, failure.code);
        assert_eq!(restored.message, failure.message);
        let outer = restored.error.expect("typed failure");
        assert_eq!(outer.reason, detail.reason);
        assert_eq!(outer.resource, detail.resource);
        assert_eq!(outer.field, detail.field);
        let Some(error_detail::Context::Stream(stream)) = outer.context else {
            panic!("terminal failure must carry a stream context");
        };
        assert_eq!(stream.code, failure.code);
        assert_eq!(stream.message, failure.message);
        assert_eq!(stream.error.as_deref(), Some(&detail));
    }

    #[test]
    fn explicit_hints_have_deterministic_precedence() {
        let base = CallFailure {
            code: CallFailureCode::Unavailable as i32,
            message: "resume".into(),
            error: None,
        };
        let cursor = CursorFailure {
            restart_cursor: "page-42".into(),
            ..Default::default()
        };
        let retry = RetryAdvice {
            retry_after: Some(prost_types::Duration {
                seconds: 3,
                nanos: 0,
            }),
        };
        for (advice, expected) in [
            (Some(retry), ErrorReason::Transient),
            (None, ErrorReason::CursorInvalid),
        ] {
            let failure = base
                .clone()
                .into_stream_failure(advice, Some(cursor.clone()));
            let outer = failure.error.expect("stream error");
            assert_eq!(outer.reason, expected as i32);
            let Some(error_detail::Context::Stream(stream)) = outer.context else {
                panic!("terminal stream context");
            };
            let hint = stream.error.expect("nested hint");
            match (advice, hint.context) {
                (Some(expected), Some(error_detail::Context::Retry(actual))) => {
                    assert_eq!(actual, expected)
                }
                (None, Some(error_detail::Context::Cursor(actual))) => assert_eq!(actual, cursor),
                _ => panic!("explicit hint must determine recovery"),
            }
        }
    }
}