Port over challenge code, in packages now

.gitignore

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+### Go template
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, build with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out

LICENSE

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+MIT License
+
+Copyright (c) 2019 @protolambda
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# Beacon transition - Go
+
+Originally "beacon challenge", put together under a line limit.
+
+This new repo aims to provide a good interface, and a minimal implementation, without code-golfing.
+
+
+## License
+
+MIT, see license file.
+

eth2/beacon/block.go

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+package beacon
+
+import "go-beacon-transition/eth2"
+
+type BeaconBlock struct {
+	// Header
+	Slot          eth2.Slot
+	Parent_root   eth2.Root
+	State_root    eth2.Root
+	Randao_reveal [96]byte
+	Eth1_data     Eth1Data
+
+	// Body
+	Body BeaconBlockBody
+	// Signature
+	Signature eth2.BLSSignature
+}
+
+type BeaconBlockBody struct {
+	Proposer_slashings []ProposerSlashing
+	Attester_slashings []AttesterSlashing
+	Attestations       []Attestation
+	Deposits           []Deposit
+	Voluntary_exits    []VoluntaryExit
+	Transfers          []Transfer
+}
+

eth2/beacon/containers.go

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+package beacon
+
+import (
+	"go-beacon-transition/eth2"
+	"go-beacon-transition/eth2/util/bitfield"
+)
+
+// NOTE: these containers are going to be moved to sub-packages, per-topic.
+
+type ProposerSlashing struct {
+	// Proposer index
+	Proposer_index eth2.ValidatorIndex
+	// First proposal
+	Proposal_1 Proposal
+	// Second proposal
+	Proposal_2 Proposal
+}
+
+type Proposal struct {
+	// Slot number
+	Slot eth2.Slot
+	// Shard number (`BEACON_CHAIN_SHARD_NUMBER` for beacon chain)
+	Shard eth2.Shard
+	// Block root
+	Block_root eth2.Root
+	// Signature
+	Signature eth2.BLSSignature
+}
+
+type AttesterSlashing struct {
+	// First slashable attestation
+	Slashable_attestation_1 SlashableAttestation
+	// Second slashable attestation
+	Slashable_attestation_2 SlashableAttestation
+}
+
+type SlashableAttestation struct {
+	// Validator indices
+	Validator_indices []eth2.ValidatorIndex
+	// Attestation data
+	Data AttestationData
+	// Custody bitfield
+	Custody_bitfield bitfield.Bitfield
+	// Aggregate signature
+	Aggregate_signature eth2.BLSSignature
+}
+
+type Attestation struct {
+	// Attester aggregation bitfield
+	Aggregation_bitfield bitfield.Bitfield
+	// Attestation data
+	Data AttestationData
+	// Custody bitfield
+	Custody_bitfield bitfield.Bitfield
+	// BLS aggregate signature
+	Aggregate_signature eth2.BLSSignature
+}
+
+type AttestationData struct {
+	// Slot number
+	Slot eth2.Slot
+	// Shard number
+	Shard eth2.Shard
+	// Root of the signed beacon block
+	Beacon_block_root eth2.Root
+	// Root of the ancestor at the epoch boundary
+	Epoch_boundary_root eth2.Root
+	// Data from the shard since the last attestation
+	Crosslink_data_root eth2.Root
+	// Last crosslink
+	Latest_crosslink Crosslink
+	// Last justified epoch in the beacon state
+	Justified_epoch eth2.Epoch
+	// Hash of the last justified beacon block
+	Justified_block_root eth2.Root
+}
+
+type AttestationDataAndCustodyBit struct {
+	// Attestation data
+	Data AttestationData
+	// Custody bit
+	Custody_bit bool
+}
+
+type Crosslink struct {
+	// Epoch number
+	Epoch eth2.Epoch
+	// Shard data since the previous crosslink
+	Crosslink_data_root eth2.Root
+}
+
+type Deposit struct {
+	// Branch in the deposit tree
+	Branch []eth2.Root
+	// Index in the deposit tree
+	Index eth2.DepositIndex
+	// Data
+	Deposit_data DepositData
+}
+
+type DepositData struct {
+	// Amount in Gwei
+	Amount eth2.Gwei
+	// Timestamp from deposit contract
+	Timestamp eth2.Timestamp
+	// Deposit input
+	Deposit_input DepositInput
+}
+
+type DepositInput struct {
+	// BLS pubkey
+	Pubkey eth2.BLSPubkey
+	// Withdrawal credentials
+	Withdrawal_credentials eth2.Root
+	// A BLS signature of this `DepositInput`
+	Proof_of_possession eth2.BLSSignature
+}
+
+type VoluntaryExit struct {
+	// Minimum epoch for processing exit
+	Epoch eth2.Epoch
+	// Index of the exiting validator
+	Validator_index eth2.ValidatorIndex
+	// Validator signature
+	Signature eth2.BLSSignature
+}
+
+type Transfer struct {
+	// Sender index
+	From eth2.ValidatorIndex
+	// Recipient index
+	To eth2.ValidatorIndex
+	// Amount in Gwei
+	Amount eth2.Gwei
+	// Fee in Gwei for block proposer
+	Fee eth2.Gwei
+	// Inclusion slot
+	Slot eth2.Slot
+	// Sender withdrawal pubkey
+	Pubkey eth2.BLSPubkey
+	// Sender signature
+	Signature eth2.BLSSignature
+}
+
+
+type Validator struct {
+	// BLS public key
+	Pubkey eth2.BLSPubkey
+	// Withdrawal credentials
+	Withdrawal_credentials eth2.Root
+	// Epoch when validator activated
+	Activation_epoch eth2.Epoch
+	// Epoch when validator exited
+	Exit_epoch eth2.Epoch
+	// Epoch when validator is eligible to withdraw
+	Withdrawable_epoch eth2.Epoch
+	// Did the validator initiate an exit
+	Initiated_exit bool
+	// Was the validator slashed
+	Slashed bool
+}
+
+func (v *Validator) IsActive(epoch eth2.Epoch) bool {
+	return v.Activation_epoch <= epoch && epoch < v.Exit_epoch
+}
+
+type PendingAttestation struct {
+	// Attester aggregation bitfield
+	Aggregation_bitfield bitfield.Bitfield
+	// Attestation data
+	Data AttestationData
+	// Custody bitfield
+	Custody_bitfield bitfield.Bitfield
+	// Inclusion slot
+	Inclusion_slot eth2.Slot
+}
+
+type Fork struct {
+	// TODO: fork versions are 64 bits, but usage is 32 bits in BLS domain. Spec unclear about it.
+	// Previous fork version
+	Previous_version uint64
+	// Current fork version
+	Current_version uint64
+	// Fork epoch number
+	Epoch eth2.Epoch
+}
+
+// Return the fork version of the given epoch
+func (f Fork) GetVersion(epoch eth2.Epoch) uint64 {
+	if epoch < f.Epoch {
+		return f.Previous_version
+	}
+	return f.Current_version
+}
+
+type Eth1Data struct {
+	// Root of the deposit tree
+	Deposit_root eth2.Root
+	// Block hash
+	Block_hash eth2.Root
+}
+
+type Eth1DataVote struct {
+	// Data being voted for
+	Eth1_data Eth1Data
+	// Vote count
+	Vote_count uint64
+}

eth2/beacon/state.go

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+package beacon
+
+import "go-beacon-transition/eth2"
+
+type BeaconState struct {
+	// Misc
+	Slot         eth2.Slot
+	Genesis_time eth2.Timestamp
+	Fork         Fork // For versioning hard forks
+
+	// Validator registry
+	Validator_registry              []Validator
+	Validator_balances              []eth2.Gwei
+	Validator_registry_update_epoch eth2.Epoch
+
+	// Randomness and committees
+	Latest_randao_mixes            [eth2.LATEST_RANDAO_MIXES_LENGTH]eth2.Bytes32
+	Previous_shuffling_start_shard eth2.Shard
+	Current_shuffling_start_shard  eth2.Shard
+	Previous_shuffling_epoch       eth2.Epoch
+	Current_shuffling_epoch        eth2.Epoch
+	Previous_shuffling_seed        eth2.Bytes32
+	Current_shuffling_seed         eth2.Bytes32
+
+	// Finality
+	Previous_justified_epoch eth2.Epoch
+	Justified_epoch          eth2.Epoch
+	Justification_bitfield   uint64
+	Finalized_epoch          eth2.Epoch
+
+	// Recent state
+	Latest_crosslinks         [eth2.SHARD_COUNT]Crosslink
+	Latest_block_roots        [eth2.LATEST_BLOCK_ROOTS_LENGTH]eth2.Root
+	Latest_active_index_roots [eth2.LATEST_ACTIVE_INDEX_ROOTS_LENGTH]eth2.Root
+	// Balances slashed at every withdrawal period
+	Latest_slashed_balances [eth2.LATEST_SLASHED_EXIT_LENGTH]eth2.Gwei
+	Latest_attestations     []PendingAttestation
+	Batched_block_roots     []eth2.Root
+
+	// Ethereum 1.0 chain data
+	Latest_eth1_data Eth1Data
+	Eth1_data_votes  []Eth1DataVote
+	Deposit_index    eth2.DepositIndex
+}
+
+// Make a deep copy of the state object
+func (st *BeaconState) Copy() *BeaconState {
+	// copy over state
+	stUn := *st
+	res := &stUn
+	// manually copy over slices
+	// validators
+	copy(res.Validator_registry, st.Validator_registry)
+	copy(res.Validator_balances, st.Validator_balances)
+	// recent state
+	copy(res.Latest_attestations, st.Latest_attestations)
+	copy(res.Batched_block_roots, st.Batched_block_roots)
+	// eth1
+	copy(res.Eth1_data_votes, st.Eth1_data_votes)
+	return res
+}
+
+// Get current epoch
+func (st *BeaconState) Epoch() eth2.Epoch {
+	return st.Slot.ToEpoch()
+}
+
+// Return previous epoch. Not just current - 1: it's clipped to genesis.
+func (st *BeaconState) PreviousEpoch() eth2.Epoch {
+	epoch := st.Epoch()
+	if epoch < eth2.GENESIS_EPOCH {
+		return eth2.GENESIS_EPOCH
+	} else {
+		return epoch
+	}
+}