// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.

// TODO(jimmy-dexon): remove comments of WitnessAck before open source.

package types

import (
	"bytes"
	"fmt"
	"io"
	"time"

	"github.com/dexon-foundation/dexon/rlp"

	"github.com/dexon-foundation/dexon-consensus/common"
	"github.com/dexon-foundation/dexon-consensus/core/crypto"
)

// GenesisHeight refers to the initial height the genesis block should be.
const GenesisHeight uint64 = 1

// BlockVerifyStatus is the return code for core.Application.VerifyBlock
type BlockVerifyStatus int

// Enums for return value of core.Application.VerifyBlock.
const (
	// VerifyOK: Block is verified.
	VerifyOK BlockVerifyStatus = iota
	// VerifyRetryLater: Block is unable to be verified at this moment.
	// Try again later.
	VerifyRetryLater
	// VerifyInvalidBlock: Block is an invalid one.
	VerifyInvalidBlock
)

type rlpTimestamp struct {
	time.Time
}

func (t *rlpTimestamp) EncodeRLP(w io.Writer) error {
	return rlp.Encode(w, uint64(t.UTC().UnixNano()))
}

func (t *rlpTimestamp) DecodeRLP(s *rlp.Stream) error {
	var nano uint64
	err := s.Decode(&nano)
	if err == nil {
		sec := int64(nano) / 1000000000
		nsec := int64(nano) % 1000000000
		t.Time = time.Unix(sec, nsec).UTC()
	}
	return err
}

// Witness represents the consensus information on the compaction chain.
type Witness struct {
	Height uint64 `json:"height"`
	Data   []byte `json:"data"`
}

// Block represents a single event broadcasted on the network.
type Block struct {
	ProposerID  NodeID           `json:"proposer_id"`
	ParentHash  common.Hash      `json:"parent_hash"`
	Hash        common.Hash      `json:"hash"`
	Position    Position         `json:"position"`
	Timestamp   time.Time        `json:"timestamp"`
	Payload     []byte           `json:"payload"`
	PayloadHash common.Hash      `json:"payload_hash"`
	Witness     Witness          `json:"witness"`
	Randomness  []byte           `json:"randomness"`
	Signature   crypto.Signature `json:"signature"`

	CRSSignature crypto.Signature `json:"crs_signature"`
}

type rlpBlock struct {
	ProposerID  NodeID
	ParentHash  common.Hash
	Hash        common.Hash
	Position    Position
	Timestamp   *rlpTimestamp
	Payload     []byte
	PayloadHash common.Hash
	Witness     *Witness
	Randomness  []byte
	Signature   crypto.Signature

	CRSSignature crypto.Signature
}

// EncodeRLP implements rlp.Encoder
func (b *Block) EncodeRLP(w io.Writer) error {
	return rlp.Encode(w, rlpBlock{
		ProposerID:   b.ProposerID,
		ParentHash:   b.ParentHash,
		Hash:         b.Hash,
		Position:     b.Position,
		Timestamp:    &rlpTimestamp{b.Timestamp},
		Payload:      b.Payload,
		PayloadHash:  b.PayloadHash,
		Witness:      &b.Witness,
		Randomness:   b.Randomness,
		Signature:    b.Signature,
		CRSSignature: b.CRSSignature,
	})
}

// DecodeRLP implements rlp.Decoder
func (b *Block) DecodeRLP(s *rlp.Stream) error {
	var dec rlpBlock
	err := s.Decode(&dec)
	if err == nil {
		*b = Block{
			ProposerID:   dec.ProposerID,
			ParentHash:   dec.ParentHash,
			Hash:         dec.Hash,
			Position:     dec.Position,
			Timestamp:    dec.Timestamp.Time,
			Payload:      dec.Payload,
			PayloadHash:  dec.PayloadHash,
			Witness:      *dec.Witness,
			Randomness:   dec.Randomness,
			Signature:    dec.Signature,
			CRSSignature: dec.CRSSignature,
		}
	}
	return err
}

func (b *Block) String() string {
	return fmt.Sprintf("Block{Hash:%v %s}", b.Hash.String()[:6], b.Position)
}

// Clone returns a deep copy of a block.
func (b *Block) Clone() (bcopy *Block) {
	bcopy = &Block{}
	bcopy.ProposerID = b.ProposerID
	bcopy.ParentHash = b.ParentHash
	bcopy.Hash = b.Hash
	bcopy.Position.Round = b.Position.Round
	bcopy.Position.Height = b.Position.Height
	bcopy.Signature = b.Signature.Clone()
	bcopy.CRSSignature = b.CRSSignature.Clone()
	bcopy.Witness.Height = b.Witness.Height
	bcopy.Witness.Data = common.CopyBytes(b.Witness.Data)
	bcopy.Timestamp = b.Timestamp
	bcopy.Payload = common.CopyBytes(b.Payload)
	bcopy.PayloadHash = b.PayloadHash
	bcopy.Randomness = common.CopyBytes(b.Randomness)
	return
}

// IsGenesis checks if the block is a genesisBlock
func (b *Block) IsGenesis() bool {
	return b.Position.Height == GenesisHeight && b.ParentHash == common.Hash{}
}

// IsFinalized checks if the block is finalized.
func (b *Block) IsFinalized() bool {
	return len(b.Randomness) > 0
}

// IsEmpty checks if the block is an 'empty block'.
func (b *Block) IsEmpty() bool {
	return b.ProposerID.Hash == common.Hash{}
}

// ByHash is the helper type for sorting slice of blocks by hash.
type ByHash []*Block

func (b ByHash) Len() int {
	return len(b)
}

func (b ByHash) Less(i int, j int) bool {
	return bytes.Compare([]byte(b[i].Hash[:]), []byte(b[j].Hash[:])) == -1
}

func (b ByHash) Swap(i int, j int) {
	b[i], b[j] = b[j], b[i]
}

// BlocksByPosition is the helper type for sorting slice of blocks by position.
type BlocksByPosition []*Block

// Len implements Len method in sort.Sort interface.
func (bs BlocksByPosition) Len() int {
	return len(bs)
}

// Less implements Less method in sort.Sort interface.
func (bs BlocksByPosition) Less(i int, j int) bool {
	return bs[j].Position.Newer(bs[i].Position)
}

// Swap implements Swap method in sort.Sort interface.
func (bs BlocksByPosition) Swap(i int, j int) {
	bs[i], bs[j] = bs[j], bs[i]
}

// Push implements Push method in heap interface.
func (bs *BlocksByPosition) Push(x interface{}) {
	*bs = append(*bs, x.(*Block))
}

// Pop implements Pop method in heap interface.
func (bs *BlocksByPosition) Pop() (ret interface{}) {
	n := len(*bs)
	*bs, ret = (*bs)[0:n-1], (*bs)[n-1]
	return
}