roadmap rest of naive attestation aggregation

beacon_chain/attestation_aggregation.nim

@@ -5,10 +5,30 @@
 #   * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+# Mostly TODOs at this point, but basically, called every 1/3 + expected
+# network + attestation pool lag to collect attestations, if one wants a
+# maximally updated pool (but could also just only aggregate to previous
+# slots, safer probably), check for some fixed slot offset to past for a
+# locally attached validator (externally-to-this-module supplied), run a
+# set of supplied algorithms (already implemented) to check if that is a
+# matching pair. Aggregation itself's already implemented in attestation
+# pool, so this is mostly (a) selection of when to aggregate, (b) change
+# of validation, (c) and specific sending deadlines with slots.
+#
+# The other part is arguably part of attestation pool -- the validation's
+# something that should be happing on receipt, not aggregation per se. In
+# that part, check that messages conform -- so, check for each type
+# https://github.com/ethereum/eth2.0-specs/blob/v0.9.2/specs/networking/p2p-interface.md#topics-and-messages
+# specifies. So by the time this calls attestation pool, all validation's
+# already done.
+#
+# Finally, some of the filtering's libp2p stuff. Consistency checks between
+# topic/message types and GOSSIP_MAX_SIZE.
+
 import
   options, sequtils,
   ./spec/[datatypes, crypto, digest, helpers, validator],
-  ./ssz
+  ./attestation_pool, ./beacon_node_types, ./ssz
 
 # TODO add tests
 # TODO gossipsub validation lives somewhere, maybe here
@@ -45,24 +65,36 @@ func should_aggregate(
   # https://github.com/ethereum/eth2.0-specs/blob/v0.9.2/specs/validator/0_beacon-chain-validator.md#aggregation-selection
   # A validator is selected to aggregate based upon the return value of
   # is_aggregator().
-  let slot = state.slot - 1 # TODO this isn't correct
-
-  # the "Construct aggregate" section seems to suggest it's from a previous
-  # slot.
+  #const use_offset = ATTESTATION_PROPAGATION_SLOT_RANGE - 3
+  #TODO implement this constant
+  # just pick some fixed time offset in past after which we should have gotten
+  # all attestations -- in principle, if we trust that we get attestations the
+  # slot get sent within SECONDS_PER_SLOT / 3, can use current slot, but seems
+  # risky. initally aim for one or two slots back to try to be currentand keep
+  # away from anything too near edge of ATTESTATION_PROPAGATION_SLOT_RANGE.
+  #
+  # static:
+  #  doAssert use_offset > 0
+  let slot = state.slot - 2
+  if slot < 0:
+    return
+  # TODO aggregate_and_proof.aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate_and_proof.aggregate.data.slot
   doAssert slot < state.slot
   is_aggregator(state, slot, index, get_slot_signature(state, slot, privkey))
 
-func aggregate_attestations_naively*(
-    state: BeaconState, index: uint64, privkey: ValidatorPrivKey):
-    Option[Attestation] =
+proc aggregate_attestations*(
+    pool: AttestationPool, state: BeaconState, index: uint64,
+    privkey: ValidatorPrivKey): Option[Attestation] =
   # Keep this code opt-in with clean entry point; if there's a part that
   # mutates state, split that off and keep this separate.
   # TODO alias CommitteeIndex to actual type then convert various uint64's here
-  # to it
-  # TODO return Option[AggregateAndProof] maybe
+  # TODO return Option[AggregateAndProof]
 
   # If the validator is selected to aggregate (`is_aggregator()`), they
   # construct an aggregate attestation
+  let slot = state.slot - 2
+  # TODO as before, check sanity here against (1) constant ATTESTATION_PROPAGATION_SLOT_RANGE
+  # and (2) genesis slot
   if not should_aggregate(state, index, privkey):
     return none(Attestation)
 
@@ -70,12 +102,15 @@ func aggregate_attestations_naively*(
   # Collect attestations seen via gossip during the slot that have an
   # equivalent attestation_data to that constructed by the validator,
   # and create an aggregate_attestation: Attestation with the following fields.
-  var aggregate_attestation = Attestation(
-  )
-
-  # https://github.com/ethereum/eth2.0-specs/blob/v0.9.2/specs/validator/0_beacon-chain-validator.md#aggregate-signature-1
-  # Set aggregate_attestation.signature = aggregate_signature where
-  # aggregate_signature is obtained from get_aggregate_signature(...).
-  aggregate_attestation.signature = get_aggregate_signature([])
+  # TODO set slot here and tell should_aggregate
+  let attestations = getAttestationsForBlock(pool, state, slot)
+  # TODO it's a greedy set packing algorithm to avoid overlap
+  # make sure this works here or change it (both places maybe?)
+  # TODO scan for matching attestationdata; already aggregated
+  # SECONDS_PER_SLOT / 3 in: initial aggregation TODO adjust this elsewhere
+  # SECONDS_PER_SLOT * 2 / 3
 
+  # TODO obviously wrong, but define check against attestation_data first
+  # also, this should be AggregateAndProof apparently, indeed.
+  let aggregate_attestation = attestations[0]
   some(aggregate_attestation)