Add first changes to syncing logic

- Adds testing framework
- Breaks out new `NetworkContext` object

beacon_node/network/src/beacon_chain.rs

@@ -7,6 +7,8 @@ use beacon_chain::{
     types::{BeaconState, ChainSpec},
     CheckPoint,
 };
+use libp2p::HelloMessage;
+use types::{Epoch, Hash256, Slot};
 
 /// The network's API to the beacon chain.
 pub trait BeaconChain: Send + Sync {
@@ -14,9 +16,19 @@ pub trait BeaconChain: Send + Sync {
 
     fn get_state(&self) -> RwLockReadGuard<BeaconState>;
 
+    fn slot(&self) -> Slot;
+
     fn head(&self) -> RwLockReadGuard<CheckPoint>;
 
+    fn best_slot(&self) -> Slot;
+
+    fn best_block_root(&self) -> Hash256;
+
     fn finalized_head(&self) -> RwLockReadGuard<CheckPoint>;
+
+    fn finalized_epoch(&self) -> Epoch;
+
+    fn hello_message(&self) -> HelloMessage;
 }
 
 impl<T, U, F> BeaconChain for RawBeaconChain<T, U, F>
@@ -33,11 +45,40 @@ where
         self.state.read()
     }
 
+    fn slot(&self) -> Slot {
+        self.get_state().slot
+    }
+
     fn head(&self) -> RwLockReadGuard<CheckPoint> {
         self.head()
     }
 
+    fn finalized_epoch(&self) -> Epoch {
+        self.get_state().finalized_epoch
+    }
+
     fn finalized_head(&self) -> RwLockReadGuard<CheckPoint> {
         self.finalized_head()
     }
+
+    fn best_slot(&self) -> Slot {
+        self.head().beacon_block.slot
+    }
+
+    fn best_block_root(&self) -> Hash256 {
+        self.head().beacon_block_root
+    }
+
+    fn hello_message(&self) -> HelloMessage {
+        let spec = self.get_spec();
+        let state = self.get_state();
+
+        HelloMessage {
+            network_id: spec.network_id,
+            latest_finalized_root: state.finalized_root,
+            latest_finalized_epoch: state.finalized_epoch,
+            best_root: self.best_block_root(),
+            best_slot: self.best_slot(),
+        }
+    }
 }