package interceptedBlocks

import (
	"fmt"

	"github.com/ElrondNetwork/elrond-go-core/core"
	"github.com/ElrondNetwork/elrond-go-core/data"
	"github.com/ElrondNetwork/elrond-go-core/hashing"
	logger "github.com/ElrondNetwork/elrond-go-logger"
	"github.com/ElrondNetwork/elrond-go/process"
	"github.com/ElrondNetwork/elrond-go/sharding"
)

var _ process.HdrValidatorHandler = (*InterceptedHeader)(nil)
var _ process.InterceptedData = (*InterceptedHeader)(nil)

// InterceptedHeader represents the wrapper over HeaderWrapper struct.
// It implements Newer and Hashed interfaces
type InterceptedHeader struct {
	hdr               data.HeaderHandler
	sigVerifier       process.InterceptedHeaderSigVerifier
	integrityVerifier process.HeaderIntegrityVerifier
	hasher            hashing.Hasher
	shardCoordinator  sharding.Coordinator
	hash              []byte
	isForCurrentShard bool
	validityAttester  process.ValidityAttester
	epochStartTrigger process.EpochStartTriggerHandler
}

// NewInterceptedHeader creates a new instance of InterceptedHeader struct
func NewInterceptedHeader(arg *ArgInterceptedBlockHeader) (*InterceptedHeader, error) {
	err := checkBlockHeaderArgument(arg)
	if err != nil {
		return nil, err
	}

	hdr, err := process.CreateShardHeader(arg.Marshalizer, arg.HdrBuff)
	if err != nil {
		return nil, err
	}

	inHdr := &InterceptedHeader{
		hdr:               hdr,
		hasher:            arg.Hasher,
		sigVerifier:       arg.HeaderSigVerifier,
		integrityVerifier: arg.HeaderIntegrityVerifier,
		shardCoordinator:  arg.ShardCoordinator,
		validityAttester:  arg.ValidityAttester,
		epochStartTrigger: arg.EpochStartTrigger,
	}
	inHdr.processFields(arg.HdrBuff)

	return inHdr, nil
}

func (inHdr *InterceptedHeader) processFields(txBuff []byte) {
	inHdr.hash = inHdr.hasher.Compute(string(txBuff))

	isHeaderForCurrentShard := inHdr.shardCoordinator.SelfId() == inHdr.HeaderHandler().GetShardID()
	isMetachainShardCoordinator := inHdr.shardCoordinator.SelfId() == core.MetachainShardId
	inHdr.isForCurrentShard = isHeaderForCurrentShard || isMetachainShardCoordinator
}

// CheckValidity checks if the received header is valid (not nil fields, valid sig and so on)
func (inHdr *InterceptedHeader) CheckValidity() error {
	err := inHdr.integrityVerifier.Verify(inHdr.hdr)
	if err != nil {
		return err
	}

	err = inHdr.integrity()
	if err != nil {
		return err
	}

	err = inHdr.sigVerifier.VerifyRandSeedAndLeaderSignature(inHdr.hdr)
	if err != nil {
		return err
	}

	return inHdr.sigVerifier.VerifySignature(inHdr.hdr)
}

func (inHdr *InterceptedHeader) isEpochCorrect() bool {
	if inHdr.shardCoordinator.SelfId() != core.MetachainShardId {
		return true
	}
	if inHdr.epochStartTrigger.EpochStartRound() >= inHdr.epochStartTrigger.EpochFinalityAttestingRound() {
		return true
	}
	if inHdr.hdr.GetEpoch() >= inHdr.epochStartTrigger.Epoch() {
		return true
	}
	if inHdr.hdr.GetRound() <= inHdr.epochStartTrigger.EpochStartRound() {
		return true
	}
	if inHdr.hdr.GetRound() <= inHdr.epochStartTrigger.EpochFinalityAttestingRound()+process.EpochChangeGracePeriod {
		return true
	}

	return false
}

// integrity checks the integrity of the header block wrapper
func (inHdr *InterceptedHeader) integrity() error {
	if !inHdr.isEpochCorrect() {
		return fmt.Errorf("%w : shard header with old epoch and bad round: "+
			"shardHeaderHash=%s, "+
			"shardId=%v, "+
			"metaEpoch=%v, "+
			"shardEpoch=%v, "+
			"shardRound=%v, "+
			"metaFinalityAttestingRound=%v ",
			process.ErrEpochDoesNotMatch,
			logger.DisplayByteSlice(inHdr.hash),
			inHdr.hdr.GetShardID(),
			inHdr.epochStartTrigger.Epoch(),
			inHdr.hdr.GetEpoch(),
			inHdr.hdr.GetRound(),
			inHdr.epochStartTrigger.EpochFinalityAttestingRound())
	}

	err := checkHeaderHandler(inHdr.HeaderHandler())
	if err != nil {
		return err
	}

	if !inHdr.validityAttester.CheckBlockAgainstWhitelist(inHdr) {
		err = inHdr.validityAttester.CheckBlockAgainstFinal(inHdr.HeaderHandler())
		if err != nil {
			return err
		}
	}

	err = inHdr.validityAttester.CheckBlockAgainstRoundHandler(inHdr.HeaderHandler())
	if err != nil {
		return err
	}

	err = checkMiniblocks(inHdr.hdr.GetMiniBlockHeaderHandlers(), inHdr.shardCoordinator)
	if err != nil {
		return err
	}

	return nil
}

// Hash gets the hash of this header
func (inHdr *InterceptedHeader) Hash() []byte {
	return inHdr.hash
}

// HeaderHandler returns the HeaderHandler pointer that holds the data
func (inHdr *InterceptedHeader) HeaderHandler() data.HeaderHandler {
	return inHdr.hdr
}

// IsForCurrentShard returns true if this header is meant to be processed by the node from this shard
func (inHdr *InterceptedHeader) IsForCurrentShard() bool {
	return inHdr.isForCurrentShard
}

// Type returns the type of this intercepted data
func (inHdr *InterceptedHeader) Type() string {
	return "intercepted header"
}

// String returns the header's most important fields as string
func (inHdr *InterceptedHeader) String() string {
	return fmt.Sprintf("shardId=%d, metaEpoch=%d, shardEpoch=%d, round=%d, nonce=%d",
		inHdr.hdr.GetShardID(),
		inHdr.epochStartTrigger.Epoch(),
		inHdr.hdr.GetEpoch(),
		inHdr.hdr.GetRound(),
		inHdr.hdr.GetNonce(),
	)
}

// Identifiers returns the identifiers used in requests
func (inHdr *InterceptedHeader) Identifiers() [][]byte {
	keyNonce := []byte(fmt.Sprintf("%d-%d", inHdr.hdr.GetShardID(), inHdr.hdr.GetNonce()))
	keyEpoch := []byte(core.EpochStartIdentifier(inHdr.hdr.GetEpoch()))

	return [][]byte{inHdr.hash, keyNonce, keyEpoch}
}

// IsInterfaceNil returns true if there is no value under the interface
func (inHdr *InterceptedHeader) IsInterfaceNil() bool {
	return inHdr == nil
}
