# beacon_chain
# Copyright (c) 2018-2022 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.

import
  std/[options, random],
  chronicles,
  eth/keys,
  stew/endians2,
  ../beacon_chain/consensus_object_pools/sync_committee_msg_pool,
  ../beacon_chain/spec/datatypes/bellatrix,
  ../beacon_chain/spec/[
    beaconstate, helpers, keystore, signatures, state_transition, validator]

type
  MockPrivKeysT = object
  MockPubKeysT = object
const
  MockPrivKeys* = MockPrivKeysT()
  MockPubKeys* = MockPubKeysT()

# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.3/tests/core/pyspec/eth2spec/test/helpers/keys.py
func `[]`*(_: MockPrivKeysT, index: ValidatorIndex|uint64): ValidatorPrivKey =
  # 0 is not a valid BLS private key - 1000 helps interop with rust BLS library,
  # lighthouse. EF tests use 1 instead of 1000.
  var bytes = (index.uint64 + 1000'u64).toBytesLE()
  static: doAssert sizeof(bytes) <= sizeof(result)
  copyMem(addr result, addr bytes, sizeof(bytes))

func `[]`*(_: MockPubKeysT, index: ValidatorIndex|uint64): ValidatorPubKey =
  MockPrivKeys[index].toPubKey().toPubKey()

func makeFakeHash*(i: int): Eth2Digest =
  var bytes = uint64(i).toBytesLE()
  static: doAssert sizeof(bytes) <= sizeof(result.data)
  copyMem(addr result.data[0], addr bytes[0], sizeof(bytes))

func makeDeposit*(
    i: int,
    flags: UpdateFlags = {},
    cfg = defaultRuntimeConfig): DepositData =
  let
    privkey = MockPrivKeys[i.ValidatorIndex]
    pubkey = MockPubKeys[i.ValidatorIndex]
    withdrawal_credentials = makeWithdrawalCredentials(pubkey)

  result = DepositData(
    pubkey: pubkey,
    withdrawal_credentials: withdrawal_credentials,
    amount: MAX_EFFECTIVE_BALANCE)

  if skipBlsValidation notin flags:
    result.signature = get_deposit_signature(cfg, result, privkey).toValidatorSig()

func makeInitialDeposits*(
    n = SLOTS_PER_EPOCH, flags: UpdateFlags = {}, cfg = defaultRuntimeConfig): seq[DepositData] =
  for i in 0..<n.int:
    result.add makeDeposit(i, flags, cfg = cfg)

func signBlock(
    fork: Fork, genesis_validators_root: Eth2Digest, forked: ForkedBeaconBlock,
    privKey: ValidatorPrivKey, flags: UpdateFlags = {}): ForkedSignedBeaconBlock =
  let
    slot = withBlck(forked): blck.slot
    root = hash_tree_root(forked)
    signature =
      if skipBlsValidation notin flags:
        get_block_signature(
          fork, genesis_validators_root, slot, root, privKey).toValidatorSig()
      else:
        ValidatorSig()
  ForkedSignedBeaconBlock.init(forked, root, signature)

proc addTestBlock*(
    state: var ForkedHashedBeaconState,
    cache: var StateCache,
    eth1_data = Eth1Data(),
    attestations = newSeq[Attestation](),
    deposits = newSeq[Deposit](),
    sync_aggregate = SyncAggregate.init(),
    graffiti = default(GraffitiBytes),
    flags: set[UpdateFlag] = {},
    nextSlot = true,
    cfg = defaultRuntimeConfig): ForkedSignedBeaconBlock =
  # Create and add a block to state - state will advance by one slot!
  if nextSlot:
    var info = ForkedEpochInfo()
    process_slots(
      cfg, state, getStateField(state, slot) + 1, cache, info, flags).expect(
        "can advance 1")

  let
    proposer_index = get_beacon_proposer_index(
      state, cache, getStateField(state, slot))
    privKey = MockPrivKeys[proposer_index.get]
    randao_reveal =
      if skipBlsValidation notin flags:
        get_epoch_signature(
          getStateField(state, fork),
          getStateField(state, genesis_validators_root),
          getStateField(state, slot).epoch, privKey).toValidatorSig()
      else:
        ValidatorSig()

  let
    message = makeBeaconBlock(
      cfg,
      state,
      proposer_index.get(),
      randao_reveal,
      # Keep deposit counts internally consistent.
      Eth1Data(
        deposit_root: eth1_data.deposit_root,
        deposit_count: getStateField(state, eth1_deposit_index) + deposits.lenu64,
        block_hash: eth1_data.block_hash),
      graffiti,
      attestations,
      deposits,
      BeaconBlockExits(),
      sync_aggregate,
      default(ExecutionPayload),
      noRollback,
      cache,
      verificationFlags = {skipBlsValidation})

  if message.isErr:
    raiseAssert "Failed to create a block: " & $message.error

  let
    new_block = signBlock(
      getStateField(state, fork),
      getStateField(state, genesis_validators_root), message.get(), privKey,
      flags)

  new_block

proc makeTestBlock*(
    state: ForkedHashedBeaconState,
    cache: var StateCache,
    eth1_data = Eth1Data(),
    attestations = newSeq[Attestation](),
    deposits = newSeq[Deposit](),
    sync_aggregate = SyncAggregate.init(),
    graffiti = default(GraffitiBytes),
    cfg = defaultRuntimeConfig): ForkedSignedBeaconBlock =
  # Create a block for `state.slot + 1` - like a block proposer would do!
  # It's a bit awkward - in order to produce a block for N+1, we need to
  # calculate what the state will look like after that block has been applied,
  # because the block includes the state root.
  let tmpState = assignClone(state)
  addTestBlock(
    tmpState[], cache, eth1_data,
    attestations, deposits, sync_aggregate, graffiti, cfg = cfg)

func makeAttestationData*(
    state: ForkyBeaconState, slot: Slot, committee_index: CommitteeIndex,
    beacon_block_root: Eth2Digest): AttestationData =
  let
    current_epoch = get_current_epoch(state)
    start_slot = start_slot(current_epoch)
    epoch_boundary_block_root =
      if start_slot == state.slot: beacon_block_root
      else: get_block_root_at_slot(state, start_slot)

  doAssert slot.epoch == current_epoch,
    "Computed epoch was " & $slot.epoch &
    "  while the state current_epoch was " & $current_epoch

  # https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/phase0/validator.md#attestation-data
  AttestationData(
    slot: slot,
    index: committee_index.uint64,
    beacon_block_root: beacon_block_root,
    source: state.current_justified_checkpoint,
    target: Checkpoint(
      epoch: current_epoch,
      root: epoch_boundary_block_root
    )
  )

func makeAttestationSig*(
    fork: Fork, genesis_validators_root: Eth2Digest, data: AttestationData,
    committee: openArray[ValidatorIndex],
    bits: CommitteeValidatorsBits): ValidatorSig =
  let signing_root = compute_attestation_signing_root(
    fork, genesis_validators_root, data)

  var
    agg {.noinit.}: AggregateSignature
    first = true

  for i in 0..<bits.len():
    if not bits[i]: continue
    let sig = blsSign(MockPrivKeys[committee[i]], signing_root.data)

    if first:
      agg.init(sig)
      first = false
    else:
      agg.aggregate(sig)

  if first:
    ValidatorSig.infinity()
  else:
    agg.finish().toValidatorSig()

func makeAttestationData*(
    state: ForkedHashedBeaconState, slot: Slot, committee_index: CommitteeIndex,
    beacon_block_root: Eth2Digest): AttestationData =
  ## Create an attestation / vote for the block `beacon_block_root` using the
  ## data in `state` to fill in the rest of the fields.
  ## `state` is the state corresponding to the `beacon_block_root` advanced to
  ## the slot we're attesting to.
  withState(state):
    makeAttestationData(
      forkyState.data, slot, committee_index, beacon_block_root)

func makeAttestation*(
    state: ForkedHashedBeaconState, beacon_block_root: Eth2Digest,
    committee: seq[ValidatorIndex], slot: Slot, committee_index: CommitteeIndex,
    validator_index: ValidatorIndex, cache: var StateCache,
    flags: UpdateFlags = {}): Attestation =
  # Avoids state_sim silliness; as it's responsible for all validators,
  # transforming, from monotonic enumerable index -> committee index ->
  # monotonic enumerable index, is wasteful and slow. Most test callers
  # want ValidatorIndex, so that's supported too.
  let
    index_in_committee = committee.find(validator_index)
    data = makeAttestationData(state, slot, committee_index, beacon_block_root)

  doAssert index_in_committee != -1, "find_beacon_committee should guarantee this"

  var aggregation_bits = CommitteeValidatorsBits.init(committee.len)
  aggregation_bits.setBit index_in_committee

  let sig = if skipBlsValidation in flags:
    ValidatorSig()
  else:
    makeAttestationSig(
      getStateField(state, fork),
      getStateField(state, genesis_validators_root),
      data, committee, aggregation_bits)

  Attestation(
    data: data,
    aggregation_bits: aggregation_bits,
    signature: sig
  )

func find_beacon_committee(
    state: ForkedHashedBeaconState, validator_index: ValidatorIndex,
    cache: var StateCache): auto =
  let epoch = epoch(getStateField(state, slot))
  for epoch_committee_index in 0'u64 ..< get_committee_count_per_slot(
      state, epoch, cache) * SLOTS_PER_EPOCH:
    let
      slot = ((epoch_committee_index mod SLOTS_PER_EPOCH) +
        epoch.start_slot.uint64).Slot
      index = CommitteeIndex(epoch_committee_index div SLOTS_PER_EPOCH)
      committee = get_beacon_committee(state, slot, index, cache)
    if validator_index in committee:
      return (committee, slot, index)
  doAssert false

func makeAttestation*(
    state: ForkedHashedBeaconState, beacon_block_root: Eth2Digest,
    validator_index: ValidatorIndex, cache: var StateCache): Attestation =
  let (committee, slot, index) =
    find_beacon_committee(state, validator_index, cache)
  makeAttestation(state, beacon_block_root, committee, slot, index,
    validator_index, cache)

func makeFullAttestations*(
    state: ForkedHashedBeaconState, beacon_block_root: Eth2Digest, slot: Slot,
    cache: var StateCache,
    flags: UpdateFlags = {}): seq[Attestation] =
  # Create attestations in which the full committee participates for each shard
  # that should be attested to during a particular slot
  let committees_per_slot = get_committee_count_per_slot(
    state, slot.epoch, cache)
  for committee_index in get_committee_indices(committees_per_slot):
    let
      committee = get_beacon_committee(state, slot, committee_index, cache)
      data = makeAttestationData(state, slot, committee_index, beacon_block_root)

    doAssert committee.len() >= 1
    var attestation = Attestation(
      aggregation_bits: CommitteeValidatorsBits.init(committee.len),
      data: data)
    for i in 0..<committee.len:
      attestation.aggregation_bits.setBit(i)

    attestation.signature = makeAttestationSig(
        getStateField(state, fork),
        getStateField(state, genesis_validators_root), data, committee,
        attestation.aggregation_bits)

    result.add attestation

proc makeSyncAggregate(
    state: ForkedHashedBeaconState,
    syncCommitteeRatio: float,
    cfg: RuntimeConfig): SyncAggregate =
  if syncCommitteeRatio <= 0.0:
    return SyncAggregate.init()

  let
    syncCommittee =
      withState(state):
        when stateFork >= BeaconStateFork.Altair:
          if (forkyState.data.slot + 1).is_sync_committee_period():
            forkyState.data.next_sync_committee
          else:
            forkyState.data.current_sync_committee
        else:
          return SyncAggregate.init()
    fork =
      getStateField(state, fork)
    genesis_validators_root =
      getStateField(state, genesis_validators_root)
    slot =
      getStateField(state, slot)
    latest_block_root =
      withState(state): state.latest_block_root
    syncCommitteePool = newClone(SyncCommitteeMsgPool.init(keys.newRng()))

  type
    Aggregator = object
      subcommitteeIdx: SyncSubcommitteeIndex
      validatorIdx: ValidatorIndex
      selectionProof: ValidatorSig

  let
    minActiveParticipants =
      if syncCommitteeRatio >= 2.0 / 3: # Ensure supermajority is hit
        (SYNC_COMMITTEE_SIZE * 2 + 2) div 3
      else:
        0
    maxActiveParticipants = (syncCommitteeRatio * SYNC_COMMITTEE_SIZE).int
  var
    aggregators: seq[Aggregator]
    numActiveParticipants = 0
  for subcommitteeIdx in SyncSubcommitteeIndex:
    let
      firstKeyIdx = subcommitteeIdx.int * SYNC_SUBCOMMITTEE_SIZE
      lastKeyIdx = firstKeyIdx + SYNC_SUBCOMMITTEE_SIZE - 1
    var processedKeys = initHashSet[ValidatorPubKey]()
    for idx, validatorKey in syncCommittee.pubkeys[firstKeyIdx .. lastKeyIdx]:
      if validatorKey in processedKeys:
        continue
      processedKeys.incl validatorKey
      let
        validatorIdx =
          block:
            var res = 0
            for i, validator in getStateField(state, validators):
              if validator.pubkey == validatorKey:
                res = i
                break
            res.ValidatorIndex
        selectionProofSig = get_sync_committee_selection_proof(
          fork, genesis_validators_root,
          slot, subcommitteeIdx,
          MockPrivKeys[validatorIdx])
      if is_sync_committee_aggregator(selectionProofSig.toValidatorSig):
        aggregators.add Aggregator(
          subcommitteeIdx: subcommitteeIdx,
          validatorIdx: validatorIdx,
          selectionProof: selectionProofSig.toValidatorSig)

      if numActiveParticipants >= minActiveParticipants and
          rand(1.0) > syncCommitteeRatio:
        continue
      var positions: seq[uint64]
      for pos, key in syncCommittee.pubkeys[firstKeyIdx + idx .. lastKeyIdx]:
        if numActiveParticipants >= maxActiveParticipants:
          break
        if key == validatorKey:
          positions.add (idx + pos).uint64
          inc numActiveParticipants
      if positions.len == 0:
        continue

      let signature = get_sync_committee_message_signature(
        fork, genesis_validators_root,
        slot, latest_block_root,
        MockPrivKeys[validatorIdx])
      syncCommitteePool[].addSyncCommitteeMessage(
        slot,
        latest_block_root,
        uint64 validatorIdx,
        signature,
        subcommitteeIdx,
        positions)

  for aggregator in aggregators:
    var contribution: SyncCommitteeContribution
    if syncCommitteePool[].produceContribution(
        slot, latest_block_root, aggregator.subcommitteeIdx, contribution):
      let
        contributionAndProof = ContributionAndProof(
          aggregator_index: uint64 aggregator.validatorIdx,
          contribution: contribution,
          selection_proof: aggregator.selectionProof)
        contributionSig = get_contribution_and_proof_signature(
          fork, genesis_validators_root,
          contributionAndProof,
          MockPrivKeys[aggregator.validatorIdx])
        signedContributionAndProof = SignedContributionAndProof(
          message: contributionAndProof,
          signature: contributionSig.toValidatorSig)
      discard syncCommitteePool[].addContribution(
        signedContributionAndProof, contribution.signature.load.get)

  syncCommitteePool[].produceSyncAggregate(latest_block_root)

iterator makeTestBlocks*(
  state: ForkedHashedBeaconState,
  cache: var StateCache,
  blocks: int,
  attested: bool,
  syncCommitteeRatio = 0.0,
  cfg = defaultRuntimeConfig): ForkedSignedBeaconBlock =
  var
    state = assignClone(state)
  for _ in 0..<blocks:
    let
      parent_root = withState(state[]): forkyState.latest_block_root
      attestations =
        if attested:
          makeFullAttestations(
            state[], parent_root, getStateField(state[], slot), cache)
        else:
          @[]
      sync_aggregate = makeSyncAggregate(state[], syncCommitteeRatio, cfg)

    yield addTestBlock(state[], cache,
      attestations = attestations, sync_aggregate = sync_aggregate, cfg = cfg)