package types

import (
	"bytes"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/tendermint/tendermint/crypto"
	"github.com/tendermint/tendermint/crypto/merkle"
	"github.com/tendermint/tendermint/crypto/tmhash"
	tmjson "github.com/tendermint/tendermint/libs/json"
	tmrand "github.com/tendermint/tendermint/libs/rand"
	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
)

// Evidence represents any provable malicious activity by a validator.
type Evidence interface {
	Height() int64                                     // height of the equivocation
	Time() time.Time                                   // time of the equivocation
	Address() []byte                                   // address of the equivocating validator
	Bytes() []byte                                     // bytes which comprise the evidence
	Hash() []byte                                      // hash of the evidence
	Verify(chainID string, pubKey crypto.PubKey) error // verify the evidence
	Equal(Evidence) bool                               // check equality of evidence

	ValidateBasic() error
	String() string
}

const (
	// MaxEvidenceBytes is a maximum size of any evidence (including amino overhead).
	MaxEvidenceBytes int64 = 444
)

// ErrEvidenceInvalid wraps a piece of evidence and the error denoting how or why it is invalid.
type ErrEvidenceInvalid struct {
	Evidence   Evidence
	ErrorValue error
}

// NewErrEvidenceInvalid returns a new EvidenceInvalid with the given err.
func NewErrEvidenceInvalid(ev Evidence, err error) *ErrEvidenceInvalid {
	return &ErrEvidenceInvalid{ev, err}
}

// Error returns a string representation of the error.
func (err *ErrEvidenceInvalid) Error() string {
	return fmt.Sprintf("Invalid evidence: %v. Evidence: %v", err.ErrorValue, err.Evidence)
}

// ErrEvidenceOverflow is for when there is too much evidence in a block.
type ErrEvidenceOverflow struct {
	MaxNum int
	GotNum int
}

// NewErrEvidenceOverflow returns a new ErrEvidenceOverflow where got > max.
func NewErrEvidenceOverflow(max, got int) *ErrEvidenceOverflow {
	return &ErrEvidenceOverflow{max, got}
}

// Error returns a string representation of the error.
func (err *ErrEvidenceOverflow) Error() string {
	return fmt.Sprintf("Too much evidence: Max %d, got %d", err.MaxNum, err.GotNum)
}

//-------------------------------------------

func EvidenceToProto(evidence Evidence) (*tmproto.Evidence, error) {
	if evidence == nil {
		return nil, errors.New("nil evidence")
	}

	switch evi := evidence.(type) {
	case *DuplicateVoteEvidence:
		pbevi := evi.ToProto()
		tp := &tmproto.Evidence{
			Sum: &tmproto.Evidence_DuplicateVoteEvidence{
				DuplicateVoteEvidence: pbevi,
			},
		}
		return tp, nil

	default:
		return nil, fmt.Errorf("toproto: evidence is not recognized: %T", evi)
	}
}

func EvidenceFromProto(evidence *tmproto.Evidence) (Evidence, error) {
	if evidence == nil {
		return nil, errors.New("nil evidence")
	}

	switch evi := evidence.Sum.(type) {
	case *tmproto.Evidence_DuplicateVoteEvidence:
		return DuplicateVoteEvidenceFromProto(evi.DuplicateVoteEvidence)
	default:
		return nil, errors.New("evidence is not recognized")
	}
}

func init() {
	tmjson.RegisterType(&DuplicateVoteEvidence{}, "tendermint/DuplicateVoteEvidence")
}

//-------------------------------------------

// DuplicateVoteEvidence contains evidence a validator signed two conflicting
// votes.
type DuplicateVoteEvidence struct {
	VoteA *Vote `json:"vote_a"`
	VoteB *Vote `json:"vote_b"`

	Timestamp time.Time `json:"timestamp"`
}

var _ Evidence = &DuplicateVoteEvidence{}

// NewDuplicateVoteEvidence creates DuplicateVoteEvidence with right ordering given
// two conflicting votes. If one of the votes is nil, evidence returned is nil as well
func NewDuplicateVoteEvidence(vote1, vote2 *Vote, time time.Time) *DuplicateVoteEvidence {
	var voteA, voteB *Vote
	if vote1 == nil || vote2 == nil {
		return nil
	}
	if strings.Compare(vote1.BlockID.Key(), vote2.BlockID.Key()) == -1 {
		voteA = vote1
		voteB = vote2
	} else {
		voteA = vote2
		voteB = vote1
	}
	return &DuplicateVoteEvidence{
		VoteA: voteA,
		VoteB: voteB,

		Timestamp: time,
	}
}

// String returns a string representation of the evidence.
func (dve *DuplicateVoteEvidence) String() string {
	return fmt.Sprintf("DuplicateVoteEvidence{VoteA: %v, VoteB: %v, Time: %v}", dve.VoteA, dve.VoteB, dve.Timestamp)
}

// Height returns the height this evidence refers to.
func (dve *DuplicateVoteEvidence) Height() int64 {
	return dve.VoteA.Height
}

// Time returns time of the latest vote.
func (dve *DuplicateVoteEvidence) Time() time.Time {
	return dve.Timestamp
}

// Address returns the address of the validator.
func (dve *DuplicateVoteEvidence) Address() []byte {
	return dve.VoteA.ValidatorAddress
}

// Hash returns the hash of the evidence.
func (dve *DuplicateVoteEvidence) Bytes() []byte {
	pbe := dve.ToProto()
	bz, err := pbe.Marshal()
	if err != nil {
		panic(err)
	}

	return bz
}

// Hash returns the hash of the evidence.
func (dve *DuplicateVoteEvidence) Hash() []byte {
	pbe := dve.ToProto()
	bz, err := pbe.Marshal()
	if err != nil {
		panic(err)
	}

	return tmhash.Sum(bz)
}

// Verify returns an error if the two votes aren't conflicting.
//
// To be conflicting, they must be from the same validator, for the same H/R/S,
// but for different blocks.
func (dve *DuplicateVoteEvidence) Verify(chainID string, pubKey crypto.PubKey) error {
	// H/R/S must be the same
	if dve.VoteA.Height != dve.VoteB.Height ||
		dve.VoteA.Round != dve.VoteB.Round ||
		dve.VoteA.Type != dve.VoteB.Type {
		return fmt.Errorf("h/r/s does not match: %d/%d/%v vs %d/%d/%v",
			dve.VoteA.Height, dve.VoteA.Round, dve.VoteA.Type,
			dve.VoteB.Height, dve.VoteB.Round, dve.VoteB.Type)
	}

	// Address must be the same
	if !bytes.Equal(dve.VoteA.ValidatorAddress, dve.VoteB.ValidatorAddress) {
		return fmt.Errorf("validator addresses do not match: %X vs %X",
			dve.VoteA.ValidatorAddress,
			dve.VoteB.ValidatorAddress,
		)
	}

	// BlockIDs must be different
	if dve.VoteA.BlockID.Equals(dve.VoteB.BlockID) {
		return fmt.Errorf(
			"block IDs are the same (%v) - not a real duplicate vote",
			dve.VoteA.BlockID,
		)
	}

	// pubkey must match address (this should already be true, sanity check)
	addr := dve.VoteA.ValidatorAddress
	if !bytes.Equal(pubKey.Address(), addr) {
		return fmt.Errorf("address (%X) doesn't match pubkey (%v - %X)",
			addr, pubKey, pubKey.Address())
	}
	va := dve.VoteA.ToProto()
	vb := dve.VoteB.ToProto()
	// Signatures must be valid
	if !pubKey.VerifySignature(VoteSignBytes(chainID, va), dve.VoteA.Signature) {
		return fmt.Errorf("verifying VoteA: %w", ErrVoteInvalidSignature)
	}
	if !pubKey.VerifySignature(VoteSignBytes(chainID, vb), dve.VoteB.Signature) {
		return fmt.Errorf("verifying VoteB: %w", ErrVoteInvalidSignature)
	}

	return nil
}

// Equal checks if two pieces of evidence are equal.
func (dve *DuplicateVoteEvidence) Equal(ev Evidence) bool {
	if _, ok := ev.(*DuplicateVoteEvidence); !ok {
		return false
	}
	pbdev := dve.ToProto()
	bz, err := pbdev.Marshal()
	if err != nil {
		panic(err)
	}

	var evbz []byte
	if ev, ok := ev.(*DuplicateVoteEvidence); ok {
		evpb := ev.ToProto()
		evbz, err = evpb.Marshal()
		if err != nil {
			panic(err)
		}
	}

	// just check their hashes
	dveHash := tmhash.Sum(bz)
	evHash := tmhash.Sum(evbz)
	return bytes.Equal(dveHash, evHash)
}

// ValidateBasic performs basic validation.
func (dve *DuplicateVoteEvidence) ValidateBasic() error {
	if dve == nil {
		return errors.New("empty duplicate vote evidence")
	}

	if dve.VoteA == nil || dve.VoteB == nil {
		return fmt.Errorf("one or both of the votes are empty %v, %v", dve.VoteA, dve.VoteB)
	}
	if err := dve.VoteA.ValidateBasic(); err != nil {
		return fmt.Errorf("invalid VoteA: %w", err)
	}
	if err := dve.VoteB.ValidateBasic(); err != nil {
		return fmt.Errorf("invalid VoteB: %w", err)
	}
	// Enforce Votes are lexicographically sorted on blockID
	if strings.Compare(dve.VoteA.BlockID.Key(), dve.VoteB.BlockID.Key()) >= 0 {
		return errors.New("duplicate votes in invalid order")
	}
	return nil
}

func (dve *DuplicateVoteEvidence) ToProto() *tmproto.DuplicateVoteEvidence {
	voteB := dve.VoteB.ToProto()
	voteA := dve.VoteA.ToProto()
	tp := tmproto.DuplicateVoteEvidence{
		VoteA:     voteA,
		VoteB:     voteB,
		Timestamp: dve.Timestamp,
	}
	return &tp
}

func DuplicateVoteEvidenceFromProto(pb *tmproto.DuplicateVoteEvidence) (*DuplicateVoteEvidence, error) {
	if pb == nil {
		return nil, errors.New("nil duplicate vote evidence")
	}

	vA, err := VoteFromProto(pb.VoteA)
	if err != nil {
		return nil, err
	}

	vB, err := VoteFromProto(pb.VoteB)
	if err != nil {
		return nil, err
	}

	dve := NewDuplicateVoteEvidence(vA, vB, pb.Timestamp)

	return dve, dve.ValidateBasic()
}

//--------------------------------------------------

// EvidenceList is a list of Evidence. Evidences is not a word.
type EvidenceList []Evidence

// Hash returns the simple merkle root hash of the EvidenceList.
func (evl EvidenceList) Hash() []byte {
	// These allocations are required because Evidence is not of type Bytes, and
	// golang slices can't be typed cast. This shouldn't be a performance problem since
	// the Evidence size is capped.
	evidenceBzs := make([][]byte, len(evl))
	for i := 0; i < len(evl); i++ {
		evidenceBzs[i] = evl[i].Bytes()
	}
	return merkle.HashFromByteSlices(evidenceBzs)
}

func (evl EvidenceList) String() string {
	s := ""
	for _, e := range evl {
		s += fmt.Sprintf("%s\t\t", e)
	}
	return s
}

// Has returns true if the evidence is in the EvidenceList.
func (evl EvidenceList) Has(evidence Evidence) bool {
	for _, ev := range evl {
		if ev.Equal(evidence) {
			return true
		}
	}
	return false
}

//-------------------------------------------- MOCKING --------------------------------------

// unstable - use only for testing

// assumes the round to be 0 and the validator index to be 0
func NewMockDuplicateVoteEvidence(height int64, time time.Time, chainID string) *DuplicateVoteEvidence {
	val := NewMockPV()
	return NewMockDuplicateVoteEvidenceWithValidator(height, time, val, chainID)
}

func NewMockDuplicateVoteEvidenceWithValidator(height int64, time time.Time,
	pv PrivValidator, chainID string) *DuplicateVoteEvidence {
	pubKey, _ := pv.GetPubKey()
	voteA := makeMockVote(height, 0, 0, pubKey.Address(), randBlockID(), time)
	vA := voteA.ToProto()
	_ = pv.SignVote(chainID, vA)
	voteA.Signature = vA.Signature
	voteB := makeMockVote(height, 0, 0, pubKey.Address(), randBlockID(), time)
	vB := voteB.ToProto()
	_ = pv.SignVote(chainID, vB)
	voteB.Signature = vB.Signature
	return NewDuplicateVoteEvidence(voteA, voteB, time)
}

func makeMockVote(height int64, round, index int32, addr Address,
	blockID BlockID, time time.Time) *Vote {
	return &Vote{
		Type:             tmproto.SignedMsgType(2),
		Height:           height,
		Round:            round,
		BlockID:          blockID,
		Timestamp:        time,
		ValidatorAddress: addr,
		ValidatorIndex:   index,
	}
}

func randBlockID() BlockID {
	return BlockID{
		Hash: tmrand.Bytes(tmhash.Size),
		PartSetHeader: PartSetHeader{
			Total: 1,
			Hash:  tmrand.Bytes(tmhash.Size),
		},
	}
}