package common

import (
	"bytes"
	"crypto/sha512"
	"encoding/binary"
	"encoding/json"
	"github.com/matchsystems/werr"
	"io"
	"time"
)

// BlockSecsDiff is the time in second that passes
// between blocks rotation
const BlockSecsDiff = 100

func GetBlockId(t time.Time) int64 {
	// because number is int -- it will just cut off the floating point part
	return (t.UTC().Unix() / BlockSecsDiff) * BlockSecsDiff
}

type BlockJson struct {
	Id           int64             `json:"id"`
	PrevHash     string            `json:"prev_hash"`
	Hash         string            `json:"hash"`
	TXs          []json.RawMessage `json:"txs"`
	IsFinished   bool              `json:"is_finished"`
	ByteEncoding string            `json:"byte_encoding"`
}

type Block struct {
	Id         int64
	PrevHash   []byte
	Hash       []byte
	TXs        []*Tx
	IsFinished bool
}

func (block *Block) CalcHash() ([]byte, error) {
	hash := sha512.New()
	if err := binary.Write(hash, binary.BigEndian, block.Id); err != nil {
		return nil, werr.Wrapf(err, "failed to write block id into hash buffer for block %d", block.Id)
	}
	hash.Write(block.PrevHash)
	for _, tx := range block.TXs {
		hash.Write(tx.Hash)
	}
	return hash.Sum(nil), nil
}

// ValidateHash calculates new block hash and compares it to current block.Hash
// returning is block hash is valid
func (block *Block) ValidateHash() bool {
	hash, err := block.CalcHash()
	if err != nil {
		return false
	}
	return bytes.Equal(block.Hash, hash)
}

// ValidateTXs returns the number of invalid transactions
// and map of hashes : reasons why txs were invalid.
// If invalid count > 0 -- the whole block isn't legit
func (block *Block) ValidateTXs() (invalidCount int, invalidTXs map[string]string) {
	invalidTXs = make(map[string]string)
	for _, tx := range block.TXs {
		if err := tx.Validate(); err != nil {
			invalidTXs[tx.HashString()] = err.Error()
			invalidCount++
		}
	}
	return invalidCount, invalidTXs
}

func (block *Block) ToJSON(byteEncodingStr string) ([]byte, error) {
	encoding, err := GetEncoding(byteEncodingStr)
	if err != nil {
		return nil, err
	}
	var txData json.RawMessage
	txsData := make([]json.RawMessage, len(block.TXs))
	for i, tx := range block.TXs {
		if txData, err = tx.ToJSON(byteEncodingStr); err != nil {
			return nil, werr.Wrapf(err, "error while converting transaction to JSON %d", i)
		}
		txsData[i] = txData
	}
	data := &BlockJson{
		Id:         block.Id,
		PrevHash:   encoding.EncodeToString(block.PrevHash),
		Hash:       encoding.EncodeToString(block.Hash),
		TXs:        txsData,
		IsFinished: block.IsFinished,
	}
	jsonBytes, err := json.Marshal(data)
	if err != nil {
		return nil, werr.Wrapf(err, "error while marshaling")
	}
	return jsonBytes, err
}

func (block *BlockJson) Process() (*Block, error) {
	var err error
	txs := make([]*Tx, len(block.TXs))
	for i, jsonTx := range block.TXs {
		if txs[i], err = TxFromJSON(jsonTx); err != nil {
			return nil, err
		}
	}
	out := &Block{
		Id:         block.Id,
		TXs:        txs,
		IsFinished: block.IsFinished,
	}
	encoding, err := GetEncoding(block.ByteEncoding)
	if err != nil {
		return nil, err
	}
	if out.Hash, err = encoding.DecodeString(block.Hash); err != nil {
		return nil, werr.Wrapf(err, "error while decoding hash")
	}
	return out, nil
}

func BlockFromJSON(marshaledData []byte) (opts *Block, err error) {
	data := &BlockJson{}
	if err := json.Unmarshal(marshaledData, data); err != nil {
		return nil, werr.Wrapf(err, "error while unmarshaling")
	}
	return data.Process()
}
func BlockFromJsonReader(r io.Reader) (opts *Block, err error) {
	data := &BlockJson{}
	if err := json.NewDecoder(r).Decode(&data); err != nil {
		return nil, werr.Wrapf(err, "error while unmarshaling")
	}
	return data.Process()
}