nimbus-eth2/tests/mocking/mock_attestations.nim

# beacon_chain
# Copyright (c) 2018-2019 Status Research & Development GmbH
# Licensed and distributed under either of
#   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
#   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.

# Mocking attestations
# ---------------------------------------------------------------

import
  # Standard library
  sets,
  # Status
  chronicles,
  # Specs
  ../../beacon_chain/spec/[datatypes, beaconstate, helpers, validator, crypto,
                           signatures, state_transition, presets],
  # Internals
  ../../beacon_chain/[ssz, extras],
  # Mocking procs
  ./mock_blocks,
  ./mock_validator_keys

proc mockAttestationData(
       state: BeaconState,
       slot: Slot,
       index: uint64): AttestationData =
  doAssert state.slot >= slot

  if slot == state.slot:
    result.beacon_block_root = mockBlockForNextSlot(state).message.parent_root
  else:
    result.beacon_block_root = get_block_root_at_slot(state, slot)

  let current_epoch_start_slot = state.get_current_epoch().compute_start_slot_at_epoch()
  let epoch_boundary_root = block:
    if slot < current_epoch_start_slot:
      get_block_root(state, get_previous_epoch(state))
    elif slot == current_epoch_start_slot:
      result.beacon_block_root
    else:
      get_block_root(state, get_current_epoch(state))

  if slot < current_epoch_start_slot:
    result.source = state.previous_justified_checkpoint
  else:
    result.source = state.current_justified_checkpoint

  let target_epoch = compute_epoch_at_slot(slot)

  result.slot = slot
  result.index = index

  result.target = Checkpoint(
    epoch: target_epoch, root: epoch_boundary_root
  )

proc signMockAttestation*(state: BeaconState, attestation: var Attestation) =
  var cache = StateCache()
  let participants = get_attesting_indices(
    state,
    attestation.data,
    attestation.aggregation_bits,
    cache
  )

  var agg {.noInit.}: AggregateSignature
  var first_iter = true # Can't do while loop on hashset
  for validator_index in participants:
    let sig = get_attestation_signature(
      state.fork, state.genesis_validators_root, attestation.data,
      MockPrivKeys[validator_index]
    )
    if first_iter:
      agg.init(sig)
      first_iter = false
    else:
      agg.aggregate(sig)

  if first_iter != true:
    attestation.signature = agg.finish()
    # Otherwise no participants so zero sig

proc mockAttestationImpl(
       state: BeaconState,
       slot: Slot,
       flags: UpdateFlags): Attestation =

  var cache = StateCache()

  let
    beacon_committee = get_beacon_committee(
      state,
      result.data.slot,
      result.data.index.CommitteeIndex,
      cache
    )
    committee_size = beacon_committee.len

  result.data = mockAttestationData(state, slot, 0)
  result.aggregation_bits = init(CommitteeValidatorsBits, committee_size)

  # fillAggregateAttestation
  for i in 0 ..< beacon_committee.len:
    result.aggregation_bits[i] = true

  if skipBlsValidation notin flags:
    signMockAttestation(state, result)

proc mockAttestation*(
       state: BeaconState,
       flags: UpdateFlags = {}): Attestation =
  mockAttestationImpl(state, state.slot, flags)

proc mockAttestation*(
       state: BeaconState,
       slot: Slot,
       flags: UpdateFlags = {}): Attestation =
  mockAttestationImpl(state, slot, flags)

func fillAggregateAttestation*(state: BeaconState, attestation: var Attestation) =
  var cache = StateCache()
  let beacon_committee = get_beacon_committee(
    state,
    attestation.data.slot,
    attestation.data.index.CommitteeIndex,
    cache
  )
  for i in 0 ..< beacon_committee.len:
    attestation.aggregation_bits[i] = true

proc add*(state: var HashedBeaconState, attestation: Attestation, slot: Slot) =
  var
    signedBlock = mockBlockForNextSlot(state.data)
    cache = StateCache()
  signedBlock.message.slot = slot
  signedBlock.message.body.attestations.add attestation
  doAssert process_slots(state, slot, cache)
  signMockBlock(state.data, signedBlock)

  let success = state_transition(
    defaultRuntimePreset, state, signedBlock, cache,
    flags = {skipStateRootValidation}, noRollback)

  doAssert success