package payload

import (
	"bytes"
	"errors"
	"io"

	"github.com/CityOfZion/neo-go/pkg/wire/payload/transaction"
	"github.com/CityOfZion/neo-go/pkg/wire/util"
)

var (
	errPadding = errors.New("There is a padding mismatch")
)

//BlockBase represents the base of the block
// This is different than the block header. See HeadersMessage
type BlockBase struct {
	// Version of the block.
	Version uint32 `json:"version"`

	// hash of the previous block.
	PrevHash util.Uint256 `json:"previousblockhash"`

	// Root hash of a transaction list.
	MerkleRoot util.Uint256 `json:"merkleroot"`

	// The time stamp of each block must be later than previous block's time stamp.
	// Generally the difference of two block's time stamp is about 15 seconds and imprecision is allowed.
	// The height of the block must be exactly equal to the height of the previous block plus 1.
	Timestamp uint32 `json:"time"`

	// index/height of the block
	Index uint32 `json:"height"`

	// Random number also called nonce
	ConsensusData uint64 `json:"nonce"`

	// Contract addresss of the next miner
	NextConsensus util.Uint160 `json:"next_consensus"`

	// Padding that is fixed to 1
	_ uint8

	// Script used to validate the block
	Witness transaction.Witness `json:"script"`

	// hash of this block, created when binary encoded.
	Hash util.Uint256
}

// EncodePayload implements the Messager interface
func (b *BlockBase) EncodePayload(bw *util.BinWriter) error {

	b.encodeHashableFields(bw)

	bw.Write(uint8(1))
	b.Witness.Encode(bw)

	return bw.Err
}

// Decode decodes an io.Reader into a Blockbase
func (b *BlockBase) Decode(r io.Reader) error {
	br := &util.BinReader{R: r}
	b.DecodePayload(br)
	return br.Err
}

// Encode encodes a blockbase into an io.Writer
func (b *BlockBase) Encode(w io.Writer) error {
	bw := &util.BinWriter{W: w}
	b.EncodePayload(bw)
	return bw.Err
}

func (b *BlockBase) encodeHashableFields(bw *util.BinWriter) {
	bw.Write(b.Version)
	bw.Write(b.PrevHash)
	bw.Write(b.MerkleRoot)
	bw.Write(b.Timestamp)
	bw.Write(b.Index)
	bw.Write(b.ConsensusData)
	bw.Write(b.NextConsensus)
}

// DecodePayload implements the messager interface
func (b *BlockBase) DecodePayload(br *util.BinReader) error {

	b.decodeHashableFields(br)

	var padding uint8
	br.Read(&padding)
	if padding != 1 {
		return errPadding
	}

	b.Witness = transaction.Witness{}
	b.Witness.Decode(br)

	err := b.createHash()

	if err != nil {
		return err
	}

	return br.Err
}

func (b *BlockBase) decodeHashableFields(br *util.BinReader) {
	br.Read(&b.Version)
	br.Read(&b.PrevHash)
	br.Read(&b.MerkleRoot)
	br.Read(&b.Timestamp)
	br.Read(&b.Index)
	br.Read(&b.ConsensusData)
	br.Read(&b.NextConsensus)
}

func (b *BlockBase) createHash() error {

	hash, err := util.CalculateHash(b.encodeHashableFields)
	b.Hash = hash
	return err
}

// Bytes returns the byte representation of Blockbase
func (b *BlockBase) Bytes() ([]byte, error) {
	buf := new(bytes.Buffer)
	err := b.Encode(buf)
	return buf.Bytes(), err
}