From f3a3cfcc45357cd691b9bbb663482056704ebf40 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sat, 2 Mar 2019 15:33:52 +1100
Subject: [PATCH] Add surround/dbl vote fns to SlashableAttestation

Copied from `SlashableVoteData`
---
 eth2/types/src/attester_slashing.rs     |  2 +-
 eth2/types/src/slashable_attestation.rs | 23 ++++++++++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/eth2/types/src/attester_slashing.rs b/eth2/types/src/attester_slashing.rs
index 2a1df9e0cc..9cb2123249 100644
--- a/eth2/types/src/attester_slashing.rs
+++ b/eth2/types/src/attester_slashing.rs
@@ -1,4 +1,4 @@
-use crate::{test_utils::TestRandom, SlashableAttestation};
+use crate::{test_utils::TestRandom, ChainSpec, SlashableAttestation};
 use rand::RngCore;
 use serde_derive::Serialize;
 use ssz_derive::{Decode, Encode, TreeHash};
diff --git a/eth2/types/src/slashable_attestation.rs b/eth2/types/src/slashable_attestation.rs
index c4a12338a5..d24c5dde42 100644
--- a/eth2/types/src/slashable_attestation.rs
+++ b/eth2/types/src/slashable_attestation.rs
@@ -1,4 +1,4 @@
-use crate::{test_utils::TestRandom, AggregateSignature, AttestationData, Bitfield};
+use crate::{test_utils::TestRandom, AggregateSignature, AttestationData, Bitfield, ChainSpec};
 use rand::RngCore;
 use serde_derive::Serialize;
 use ssz_derive::{Decode, Encode, TreeHash};
@@ -12,6 +12,27 @@ pub struct SlashableAttestation {
     pub aggregate_signature: AggregateSignature,
 }
 
+impl SlashableAttestation {
+    /// Check if ``attestation_data_1`` and ``attestation_data_2`` have the same target.
+    ///
+    /// Spec v0.3.0
+    pub fn is_double_vote(&self, other: &SlashableAttestation, spec: &ChainSpec) -> bool {
+        self.data.slot.epoch(spec.epoch_length) == other.data.slot.epoch(spec.epoch_length)
+    }
+
+    /// Check if ``attestation_data_1`` surrounds ``attestation_data_2``.
+    ///
+    /// Spec v0.3.0
+    pub fn is_surround_vote(&self, other: &SlashableAttestation, spec: &ChainSpec) -> bool {
+        let source_epoch_1 = self.data.justified_epoch;
+        let source_epoch_2 = other.data.justified_epoch;
+        let target_epoch_1 = self.data.slot.epoch(spec.epoch_length);
+        let target_epoch_2 = other.data.slot.epoch(spec.epoch_length);
+
+        (source_epoch_1 < source_epoch_2) && (target_epoch_2 < target_epoch_1)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;