package drand

import (
	"crypto/sha256"
	"encoding/binary"
	"errors"
	"strconv"
	"sync"

	protobuf "github.com/golang/protobuf/proto"
	"github.com/harmony-one/bls/ffi/go/bls"
	drand_proto "github.com/harmony-one/harmony/api/drand"
	"github.com/harmony-one/harmony/core/types"
	bls_cosi "github.com/harmony-one/harmony/crypto/bls"
	"github.com/harmony-one/harmony/crypto/vrf"
	"github.com/harmony-one/harmony/crypto/vrf/p256"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/p2p"
)

// DRand is the main struct which contains state for the distributed randomness protocol.
type DRand struct {
	vrfs                  *map[uint32][]byte
	bitmap                *bls_cosi.Mask
	pRand                 *[32]byte
	rand                  *[32]byte
	ConfirmedBlockChannel chan *types.Block // Channel to receive confirmed blocks
	PRndChannel           chan []byte       // Channel to send pRnd (preimage of randomness resulting from combined vrf randomnesses) to consensus. The first 32 bytes are randomness, the rest is for bitmap.
	RndChannel            chan [64]byte     // Channel for DRG protocol to send the final randomness to consensus. The first 32 bytes are the randomness and the last 32 bytes are the hash of the block where the corresponding pRnd was generated

	// global consensus mutex
	mutex sync.Mutex

	// map of nodeID to validator Peer object
	// FIXME: should use PubKey of p2p.Peer as the hashkey
	validators sync.Map // key is uint16, value is p2p.Peer

	// Leader's address
	leader p2p.Peer

	// Public keys of the committee including leader and validators
	PublicKeys []*bls.PublicKey
	pubKeyLock sync.Mutex

	// private/public keys of current node
	priKey *bls.SecretKey
	pubKey *bls.PublicKey
	// VRF private and public key
	// TODO: directly use signature signing key (BLS) for vrf
	vrfPriKey *vrf.PrivateKey
	vrfPubKey *vrf.PublicKey

	// Whether I am leader. False means I am validator
	IsLeader bool

	// Leader or validator Id - 4 byte
	nodeID uint32

	// The p2p host used to send/receive p2p messages
	host p2p.Host

	// Shard Id which this node belongs to
	ShardID uint32

	// Blockhash - 32 byte
	blockHash [32]byte
}

// New creates a new dRand object
func New(host p2p.Host, ShardID string, peers []p2p.Peer, leader p2p.Peer, confirmedBlockChannel chan *types.Block, isLeader bool) *DRand {
	dRand := DRand{}
	dRand.host = host

	if confirmedBlockChannel != nil {
		dRand.ConfirmedBlockChannel = confirmedBlockChannel
	}

	dRand.PRndChannel = make(chan []byte)
	dRand.RndChannel = make(chan [64]byte)

	selfPeer := host.GetSelfPeer()
	dRand.IsLeader = isLeader

	dRand.leader = leader
	for _, peer := range peers {
		dRand.validators.Store(utils.GetUniqueIDFromPeer(peer), peer)
	}

	dRand.vrfs = &map[uint32][]byte{}

	// Initialize cosign bitmap
	allPublicKeys := make([]*bls.PublicKey, 0)
	for _, validatorPeer := range peers {
		allPublicKeys = append(allPublicKeys, validatorPeer.PubKey)
	}
	allPublicKeys = append(allPublicKeys, leader.PubKey)

	dRand.PublicKeys = allPublicKeys

	bitmap, _ := bls_cosi.NewMask(dRand.PublicKeys, dRand.leader.PubKey)
	dRand.bitmap = bitmap

	dRand.pRand = nil
	dRand.rand = nil

	// For now use socket address as ID
	// TODO: populate Id derived from address
	dRand.nodeID = utils.GetUniqueIDFromPeer(selfPeer)

	// Set private key for myself so that I can sign messages.
	nodeIDBytes := make([]byte, 32)
	binary.LittleEndian.PutUint32(nodeIDBytes, dRand.nodeID)
	privateKey := bls.SecretKey{}
	err := privateKey.SetLittleEndian(nodeIDBytes)
	dRand.priKey = &privateKey
	dRand.pubKey = privateKey.GetPublicKey()

	// VRF keys
	priKey, pubKey := p256.GenerateKey()
	dRand.vrfPriKey = &priKey
	dRand.vrfPubKey = &pubKey

	myShardID, err := strconv.Atoi(ShardID)
	if err != nil {
		panic("Unparseable shard Id" + ShardID)
	}
	dRand.ShardID = uint32(myShardID)

	return &dRand
}

// AddPeers adds new peers into the validator map of the consensus
// and add the public keys
func (dRand *DRand) AddPeers(peers []*p2p.Peer) int {
	count := 0

	for _, peer := range peers {
		_, ok := dRand.validators.Load(utils.GetUniqueIDFromPeer(*peer))
		if !ok {
			dRand.validators.Store(utils.GetUniqueIDFromPeer(*peer), *peer)
			dRand.pubKeyLock.Lock()
			dRand.PublicKeys = append(dRand.PublicKeys, peer.PubKey)
			dRand.pubKeyLock.Unlock()
			utils.GetLogInstance().Debug("[DRAND]", "AddPeers", *peer)
		}
		count++
	}
	return count
}

// Sign on the drand message signature field.
func (dRand *DRand) signDRandMessage(message *drand_proto.Message) error {
	message.Signature = nil
	// TODO: use custom serialization method rather than protobuf
	marshaledMessage, err := protobuf.Marshal(message)
	if err != nil {
		return err
	}
	// 64 byte of signature on previous data
	hash := sha256.Sum256(marshaledMessage)
	signature := dRand.priKey.SignHash(hash[:])

	message.Signature = signature.Serialize()
	return nil
}

// Signs the drand message and returns the marshaled message.
func (dRand *DRand) signAndMarshalDRandMessage(message *drand_proto.Message) ([]byte, error) {
	err := dRand.signDRandMessage(message)
	if err != nil {
		return []byte{}, err
	}

	marshaledMessage, err := protobuf.Marshal(message)
	if err != nil {
		return []byte{}, err
	}
	return marshaledMessage, nil
}

func (dRand *DRand) vrf(blockHash [32]byte) (rand [32]byte, proof []byte) {
	rand, proof = (*dRand.vrfPriKey).Evaluate(blockHash[:])
	return
}

// GetValidatorPeers returns list of validator peers.
func (dRand *DRand) GetValidatorPeers() []p2p.Peer {
	validatorPeers := make([]p2p.Peer, 0)

	dRand.validators.Range(func(k, v interface{}) bool {
		if peer, ok := v.(p2p.Peer); ok {
			validatorPeers = append(validatorPeers, peer)
			return true
		}
		return false
	})

	return validatorPeers
}

// Verify the signature of the message are valid from the signer's public key.
func verifyMessageSig(signerPubKey *bls.PublicKey, message drand_proto.Message) error {
	signature := message.Signature
	message.Signature = nil
	messageBytes, err := protobuf.Marshal(&message)
	if err != nil {
		return err
	}

	msgSig := bls.Sign{}
	err = msgSig.Deserialize(signature)
	if err != nil {
		return err
	}
	msgHash := sha256.Sum256(messageBytes)
	if !msgSig.VerifyHash(signerPubKey, msgHash[:]) {
		return errors.New("failed to verify the signature")
	}
	return nil
}

// Gets the validator peer based on validator ID.
func (dRand *DRand) getValidatorPeerByID(validatorID uint32) *p2p.Peer {
	v, ok := dRand.validators.Load(validatorID)
	if !ok {
		utils.GetLogInstance().Warn("Unrecognized validator", "validatorID", validatorID, "dRand", dRand)
		return nil
	}
	value, ok := v.(p2p.Peer)
	if !ok {
		utils.GetLogInstance().Warn("Invalid validator", "validatorID", validatorID, "dRand", dRand)
		return nil
	}
	return &value
}

// ResetState resets the state of the randomness protocol
func (dRand *DRand) ResetState() {
	dRand.vrfs = &map[uint32][]byte{}

	bitmap, _ := bls_cosi.NewMask(dRand.PublicKeys, dRand.leader.PubKey)
	dRand.bitmap = bitmap
	dRand.pRand = nil
	dRand.rand = nil
}

// SetLeaderPubKey deserialize the public key of drand leader
func (dRand *DRand) SetLeaderPubKey(k []byte) error {
	dRand.leader.PubKey = &bls.PublicKey{}
	return dRand.leader.PubKey.Deserialize(k)
}

// UpdatePublicKeys updates the PublicKeys variable, protected by a mutex
func (dRand *DRand) UpdatePublicKeys(pubKeys []*bls.PublicKey) int {
	dRand.pubKeyLock.Lock()
	dRand.PublicKeys = append(pubKeys[:0:0], pubKeys...)
	dRand.pubKeyLock.Unlock()

	return len(dRand.PublicKeys)
}