implement distinct Epoch type and continue 0.4.0 spec update (#173)

* implement distinct Epoch type
* update two more spec 0.4.0 markers, leaving just deposit processing

beacon_chain/spec/beaconstate.nim

@@ -218,7 +218,7 @@ func get_genesis_beacon_state*(
 
   for i in 0 ..< SHARD_COUNT:
     state.latest_crosslinks[i] = Crosslink(
-      epoch: GENESIS_EPOCH, crosslink_data_root: ZERO_HASH)
+      epoch: GENESIS_EPOCH.uint64, crosslink_data_root: ZERO_HASH)
 
   # Process genesis deposits
   for deposit in genesis_validator_deposits:
@@ -401,7 +401,8 @@ proc checkAttestation*(
     return
 
   let expected_justified_block_root =
-    get_block_root(state, get_epoch_start_slot(attestation.data.justified_epoch))
+    get_block_root(
+      state, get_epoch_start_slot(attestation.data.justified_epoch.Epoch))
   if not (attestation.data.justified_block_root == expected_justified_block_root):
     warn("Unexpected justified block root",
       attestation_justified_block_root = attestation.data.justified_block_root,
@@ -412,7 +413,7 @@ proc checkAttestation*(
       attestation.data.latest_crosslink,
       Crosslink(
         crosslink_data_root: attestation.data.crosslink_data_root,
-        epoch: slot_to_epoch(attestation_data_slot))]):
+        epoch: slot_to_epoch(attestation_data_slot).uint64)]):
     warn("Unexpected crosslink shard",
       state_latest_crosslinks_attestation_data_shard =
         state.latest_crosslinks[attestation.data.shard],
@@ -521,6 +522,6 @@ proc makeAttestationData*(
     epoch_boundary_root: epoch_boundary_root,
     crosslink_data_root: Eth2Digest(), # Stub in phase0
     latest_crosslink: state.latest_crosslinks[shard],
-    justified_epoch: state.justified_epoch,
+    justified_epoch: state.justified_epoch.uint64,
     justified_block_root: justified_block_root,
   )

beacon_chain/spec/datatypes.nim

@@ -42,7 +42,7 @@ import
 
 type
   Slot* = distinct uint64
-  Epoch* = uint64
+  Epoch* = distinct uint64
 
 const
   SPEC_VERSION* = "0.4.0" ## \
@@ -112,7 +112,7 @@ const
   GENESIS_EPOCH* = (GENESIS_SLOT.uint64 div SLOTS_PER_EPOCH).Epoch ##\
   ## slot_to_epoch(GENESIS_SLOT)
   GENESIS_START_SHARD* = 0'u64
-  FAR_FUTURE_EPOCH* = not 0'u64 # 2^64 - 1 in spec
+  FAR_FUTURE_EPOCH* = (not 0'u64).Epoch # 2^64 - 1 in spec
   ZERO_HASH* = Eth2Digest()
   EMPTY_SIGNATURE* = ValidatorSig()
   BLS_WITHDRAWAL_PREFIX_BYTE* = 0'u8
@@ -246,7 +246,7 @@ type
     latest_crosslink*: Crosslink ##\
     ## Last crosslink
 
-    justified_epoch*: Epoch ##\
+    justified_epoch*: uint64 ##\
     ## Last justified epoch in the beacon state
 
     justified_block_root*: Eth2Digest ##\
@@ -284,7 +284,7 @@ type
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#voluntaryexit
   VoluntaryExit* = object
     # Minimum epoch for processing exit
-    epoch*: Epoch
+    epoch*: uint64
     # Index of the exiting validator
     validator_index*: uint64
     # Validator signature
@@ -451,7 +451,7 @@ type
 
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#crosslink
   Crosslink* = object
-    epoch*: Epoch ##\
+    epoch*: uint64 ##\
     ## Epoch number
 
     crosslink_data_root*: Eth2Digest ##\
@@ -527,15 +527,17 @@ template ethTimeUnit(typ: type) =
   proc `-`*(x: typ, y: uint64): typ {.borrow.}
   proc `-`*(x: uint64, y: typ): typ {.borrow.}
 
-  proc `+=`*(x: var typ, y: uint64) {.borrow.}
-  proc `-=`*(x: var typ, y: uint64) {.borrow.}
-
   # Not closed over type in question (Slot or Epoch)
   proc `mod`*(x: typ, y: uint64): uint64 {.borrow.}
   proc `div`*(x: typ, y: uint64): uint64 {.borrow.}
   proc `div`*(x: uint64, y: typ): uint64 {.borrow.}
   proc `-`*(x: typ, y: typ): uint64 {.borrow.}
 
+  proc `*`*(x: typ, y: uint64): uint64 {.borrow.}
+
+  proc `+=`*(x: var typ, y: uint64) {.borrow.}
+  proc `-=`*(x: var typ, y: uint64) {.borrow.}
+
   # Comparison operators
   proc `<`*(x: typ, y: typ): bool {.borrow.}
   proc `<`*(x: typ, y: uint64): bool {.borrow.}
@@ -543,21 +545,23 @@ template ethTimeUnit(typ: type) =
   proc `<=`*(x: typ, y: typ): bool {.borrow.}
   proc `<=`*(x: typ, y: uint64): bool {.borrow.}
   proc `<=`*(x: uint64, y: typ): bool {.borrow.}
+
   proc `==`*(x: typ, y: typ): bool {.borrow.}
   proc `==`*(x: typ, y: uint64): bool {.borrow.}
+  proc `==`*(x: uint64, y: typ): bool {.borrow.}
 
   # Nim integration
   proc `$`*(x: typ): string {.borrow.}
   proc hash*(x: typ): Hash {.borrow.}
 
 ethTimeUnit(Slot)
-#ethTimeUnit(Epoch)
+ethTimeUnit(Epoch)
 
 func humaneSlotNum*(s: auto): uint64 =
   s.Slot - GENESIS_SLOT
 
-func humaneEpochNum*(e: Epoch): Epoch =
-  e - GENESIS_EPOCH
+func humaneEpochNum*(e: auto): uint64 =
+  e.Epoch - GENESIS_EPOCH
 
 import nimcrypto, json_serialization
 export json_serialization

beacon_chain/spec/helpers.nim

@@ -218,10 +218,11 @@ func bytes_to_int*(data: seq[byte]): uint64 =
 
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#int_to_bytes1-int_to_bytes2-
 # Have 1, 4, and 32-byte versions. 2+ more and maybe worth metaprogramming.
-func int_to_bytes32*(x: uint64) : array[32, byte] =
-  # Little-endian data representation
+func int_to_bytes32*(x: uint64|Epoch) : array[32, byte] =
+  ## Little-endian data representation
+  ## TODO remove uint64 when those callers fade away
   for i in 0 ..< 8:
-    result[24 + i] = byte((x shr i*8) and 0xff)
+    result[24 + i] = byte((x.uint64 shr i*8) and 0xff)
 
 func int_to_bytes1*(x: int): array[1, byte] =
   assert x >= 0

beacon_chain/spec/validator.nim

@@ -71,7 +71,7 @@ func get_shuffled_seq*(seed: Eth2Digest,
 
   result = shuffled_active_validator_indices
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.3.0/specs/core/0_beacon-chain.md#get_shuffling
+# https://github.com/ethereum/eth2.0-specs/blob/v0.4.0/specs/core/0_beacon-chain.md#get_shuffling
 func get_shuffling*(seed: Eth2Digest,
                     validators: openArray[Validator],
                     epoch: Epoch,
@@ -80,6 +80,8 @@ func get_shuffling*(seed: Eth2Digest,
   ## This function is factored to facilitate testing with
   ## https://github.com/ethereum/eth2.0-test-generators/tree/master/permutated_index
   ## test vectors, which the split of get_shuffling obfuscates.
+  ## TODO fix bad list size but keep consistent with cached values,
+  ## once epoch processing reordering comes around
   let list_size = validators.len.uint64
 
   let

beacon_chain/ssz.nim

@@ -153,11 +153,8 @@ proc endRecord*(w: var SszWriter, memo: RecordWritingMemo) =
   let finalSize = uint32(w.stream.pos - memo.initialStreamPos - 4)
   memo.sizePrefixCursor.endWrite(finalSize.toBytesSSZ)
 
-func toSSZType(x: auto): auto =
-  when x is Slot:
-    x.uint64
-  else:
-    x
+func toSSZType(x: Slot|Epoch): auto = x.uint64
+func toSSZType(x: auto): auto = x
 
 proc writeValue*(w: var SszWriter, obj: auto) =
   # We are not using overloads here, because this leads to
@@ -241,8 +238,11 @@ proc readValue*(r: var SszReader, result: var auto) =
 
     else:
       result.deserializeFields(fieldName, field):
+        # TODO This hardcoding's ugly; generalize & abstract.
         when field is Slot:
           field = r.readValue(uint64).Slot
+        elif field is Epoch:
+          field = r.readValue(uint64).Epoch
         else:
           field = r.readValue(field.type)
 

beacon_chain/state_transition.nim

@@ -59,7 +59,7 @@ func verifyBlockSignature(state: BeaconState, blck: BeaconBlock): bool =
     proposal.signature,
     get_domain(state.fork, get_current_epoch(state), DOMAIN_PROPOSAL))
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.3.0/specs/core/0_beacon-chain.md#randao
+# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#randao
 proc processRandao(
     state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags): bool =
   let
@@ -69,7 +69,7 @@ proc processRandao(
   if skipValidation notin flags:
     if not bls_verify(
       proposer.pubkey,
-      int_to_bytes32(get_current_epoch(state)),
+      hash_tree_root(get_current_epoch(state).uint64),
       blck.randao_reveal,
       get_domain(state.fork, get_current_epoch(state), DOMAIN_RANDAO)):
 
@@ -280,7 +280,6 @@ proc processAttestations(
 
 # https://github.com/ethereum/eth2.0-specs/blob/v0.3.0/specs/core/0_beacon-chain.md#deposits-1
 func processDeposits(state: var BeaconState, blck: BeaconBlock): bool =
-  # TODO! Spec writing in progress as of v0.3.0
   true
 
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#voluntary-exits-1
@@ -305,7 +304,7 @@ proc processExits(
     if skipValidation notin flags:
       if not bls_verify(
           validator.pubkey, signed_root(exit, "signature"), exit.signature,
-          get_domain(state.fork, exit.epoch, DOMAIN_EXIT)):
+          get_domain(state.fork, exit.epoch.Epoch, DOMAIN_EXIT)):
         notice "Exit: invalid signature"
         return false
 
@@ -718,7 +717,7 @@ func processEpoch(state: var BeaconState) =
         if 3'u64 * total_attesting_balance(crosslink_committee) >=
             2'u64 * get_total_balance(state, crosslink_committee.committee):
           state.latest_crosslinks[crosslink_committee.shard] = Crosslink(
-            epoch: slot_to_epoch(slot),
+            epoch: slot_to_epoch(slot).uint64,
             crosslink_data_root: winning_root(crosslink_committee))
 
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#rewards-and-penalties

beacon_chain/sync_protocol.nim

@@ -74,7 +74,7 @@ p2pProtocol BeaconSync(version = 1,
 
     var
       latestFinalizedRoot: Eth2Digest # TODO
-      latestFinalizedEpoch: uint64 = node.state.data.finalized_epoch
+      latestFinalizedEpoch: uint64 = node.state.data.finalized_epoch.uint64
       bestRoot: Eth2Digest # TODO
       bestSlot: uint64 = node.state.data.slot.uint64
 

beacon_chain/validator_pool.nim

@@ -60,7 +60,7 @@ func genRandaoReveal*(k: ValidatorPrivKey, state: BeaconState, slot: Slot):
 
   # Off-by-one? I often get slot == state.slot but the check was "assert slot > state.slot" (Mamy)
   assert slot >= state.slot, "input slot: " & $humaneSlotNum(slot) & " - beacon state slot: " & $humaneSlotNum(state.slot)
-  bls_sign(k, int_to_bytes32(slot_to_epoch(slot)),
+  bls_sign(k, hash_tree_root(slot_to_epoch(slot).uint64),
     get_domain(state.fork, slot_to_epoch(slot), DOMAIN_RANDAO))
 
 func genRandaoReveal*(v: AttachedValidator, state: BeaconState, slot: Slot):

research/state_sim.nim

@@ -37,6 +37,7 @@ template withTimerRet(stats: var RunningStat, body: untyped): untyped =
   tmp
 
 proc `%`*(x: Slot): JsonNode {.borrow.}
+proc `%`*(x: Epoch): JsonNode {.borrow.}
 
 proc writeJson*(prefix, slot, v: auto) =
   var f: File

tests/test_validator.nim

@@ -33,7 +33,7 @@ suite "Validators":
         Validator(
           exit_epoch: FAR_FUTURE_EPOCH
         ), num_validators)
-      s = get_shuffling(Eth2Digest(), validators, 0, ShufflingCache())
+      s = get_shuffling(Eth2Digest(), validators, GENESIS_EPOCH, ShufflingCache())
       committees = get_epoch_committee_count(len(validators)).int
     check:
       # def b(s): return "Eth2Digest(data: [0x" + "'u8, 0x".join((s[i:i+2] for i in range(0, 64, 2))) + "'u8])"