Add attester to beacon chain test harness

beacon_node/beacon_chain/src/attestation_processing.rs

@@ -0,0 +1,47 @@
+use super::{BeaconChain, ClientDB, SlotClock};
+pub use crate::attestation_aggregator::{ProcessError as AggregatorError, ProcessOutcome};
+use crate::canonical_head::Error as HeadError;
+use types::{AttestationData, Signature};
+
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    PresentSlotUnknown,
+    AggregatorError(AggregatorError),
+    HeadError(HeadError),
+}
+
+impl<T, U> BeaconChain<T, U>
+where
+    T: ClientDB,
+    U: SlotClock,
+{
+    pub fn process_free_attestation(
+        &self,
+        attestation_data: &AttestationData,
+        signature: &Signature,
+        validator_index: u64,
+    ) -> Result<ProcessOutcome, Error> {
+        let present_slot = self
+            .present_slot()
+            .ok_or_else(|| Error::PresentSlotUnknown)?;
+        let state = self.state(present_slot)?;
+
+        self.attestation_aggregator
+            .write()
+            .expect("Aggregator unlock failed.")
+            .process_free_attestation(&state, attestation_data, signature, validator_index)
+            .map_err(|e| e.into())
+    }
+}
+
+impl From<AggregatorError> for Error {
+    fn from(e: AggregatorError) -> Error {
+        Error::AggregatorError(e)
+    }
+}
+
+impl From<HeadError> for Error {
+    fn from(e: HeadError) -> Error {
+        Error::HeadError(e)
+    }
+}