package state

import (
	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
	"github.com/nspcc-dev/neo-go/pkg/io"
	"github.com/nspcc-dev/neo-go/pkg/util"
)

// MPTRootBase represents storage state root.
type MPTRootBase struct {
	Version  byte
	Index    uint32
	PrevHash util.Uint256
	Root     util.Uint256
}

// MPTRoot represents storage state root together with sign info.
type MPTRoot struct {
	MPTRootBase
	Witness *transaction.Witness
}

// MPTRootStateFlag represents verification state of the state root.
type MPTRootStateFlag byte

// Possible verification states of MPTRoot.
const (
	Unverified MPTRootStateFlag = 0x00
	Verified   MPTRootStateFlag = 0x01
	Invalid    MPTRootStateFlag = 0x03
)

// MPTRootState represents state root together with its verification state.
type MPTRootState struct {
	MPTRoot
	Flag MPTRootStateFlag
}

// EncodeBinary implements io.Serializable.
func (s *MPTRootState) EncodeBinary(w *io.BinWriter) {
	w.WriteB(byte(s.Flag))
	s.MPTRoot.EncodeBinary(w)
}

// DecodeBinary implements io.Serializable.
func (s *MPTRootState) DecodeBinary(r *io.BinReader) {
	s.Flag = MPTRootStateFlag(r.ReadB())
	s.MPTRoot.DecodeBinary(r)
}

// GetSignedPart returns part of MPTRootBase which needs to be signed.
func (s *MPTRootBase) GetSignedPart() []byte {
	buf := io.NewBufBinWriter()
	s.EncodeBinary(buf.BinWriter)
	return buf.Bytes()
}

// Equals checks if s == other.
func (s *MPTRootBase) Equals(other *MPTRootBase) bool {
	return s.Version == other.Version && s.Index == other.Index &&
		s.PrevHash.Equals(other.PrevHash) && s.Root.Equals(other.Root)
}

// Hash returns hash of s.
func (s *MPTRootBase) Hash() util.Uint256 {
	return hash.DoubleSha256(s.GetSignedPart())
}

// DecodeBinary implements io.Serializable.
func (s *MPTRootBase) DecodeBinary(r *io.BinReader) {
	s.Version = r.ReadB()
	s.Index = r.ReadU32LE()
	s.PrevHash.DecodeBinary(r)
	s.Root.DecodeBinary(r)
}

// EncodeBinary implements io.Serializable.
func (s *MPTRootBase) EncodeBinary(w *io.BinWriter) {
	w.WriteB(s.Version)
	w.WriteU32LE(s.Index)
	s.PrevHash.EncodeBinary(w)
	s.Root.EncodeBinary(w)
}

// DecodeBinary implements io.Serializable.
func (s *MPTRoot) DecodeBinary(r *io.BinReader) {
	s.MPTRootBase.DecodeBinary(r)

	var ws []transaction.Witness
	r.ReadArray(&ws, 1)
	if len(ws) == 1 {
		s.Witness = &ws[0]
	}
}

// EncodeBinary implements io.Serializable.
func (s *MPTRoot) EncodeBinary(w *io.BinWriter) {
	s.MPTRootBase.EncodeBinary(w)
	if s.Witness == nil {
		w.WriteVarUint(0)
	} else {
		w.WriteArray([]*transaction.Witness{s.Witness})
	}
}