package types

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"sync"

	crypto "github.com/tendermint/go-crypto"
	data "github.com/tendermint/go-wire/data"
	. "github.com/tendermint/tmlibs/common"
	"github.com/tendermint/tmlibs/log"
)

const (
	stepNone      = 0 // Used to distinguish the initial state
	stepPropose   = 1
	stepPrevote   = 2
	stepPrecommit = 3
)

func voteToStep(vote *Vote) int8 {
	switch vote.Type {
	case VoteTypePrevote:
		return stepPrevote
	case VoteTypePrecommit:
		return stepPrecommit
	default:
		PanicSanity("Unknown vote type")
		return 0
	}
}

type PrivValidator struct {
	Address       data.Bytes       `json:"address"`
	PubKey        crypto.PubKey    `json:"pub_key"`
	LastHeight    int              `json:"last_height"`
	LastRound     int              `json:"last_round"`
	LastStep      int8             `json:"last_step"`
	LastSignature crypto.Signature `json:"last_signature,omitempty"` // so we dont lose signatures
	LastSignBytes data.Bytes       `json:"last_signbytes,omitempty"` // so we dont lose signatures

	// PrivKey should be empty if a Signer other than the default is being used.
	PrivKey crypto.PrivKey `json:"priv_key"`
	Signer  `json:"-"`

	// For persistence.
	// Overloaded for testing.
	filePath string
	mtx      sync.Mutex
}

// This is used to sign votes.
// It is the caller's duty to verify the msg before calling Sign,
// eg. to avoid double signing.
// Currently, the only callers are SignVote and SignProposal
type Signer interface {
	PubKey() crypto.PubKey
	Sign(msg []byte) crypto.Signature
}

// Implements Signer
type DefaultSigner struct {
	priv crypto.PrivKey
}

func NewDefaultSigner(priv crypto.PrivKey) *DefaultSigner {
	return &DefaultSigner{priv: priv}
}

// Implements Signer
func (ds *DefaultSigner) Sign(msg []byte) crypto.Signature {
	return ds.priv.Sign(msg)
}

// Implements Signer
func (ds *DefaultSigner) PubKey() crypto.PubKey {
	return ds.priv.PubKey()
}

func (privVal *PrivValidator) SetSigner(s Signer) {
	privVal.Signer = s
	privVal.setPubKeyAndAddress()
}

// Overwrite address and pubkey for convenience
func (privVal *PrivValidator) setPubKeyAndAddress() {
	privVal.PubKey = privVal.Signer.PubKey()
	privVal.Address = privVal.PubKey.Address()
}

// Generates a new validator with private key.
func GenPrivValidator() *PrivValidator {
	privKey := crypto.GenPrivKeyEd25519().Wrap()
	pubKey := privKey.PubKey()
	return &PrivValidator{
		Address:  pubKey.Address(),
		PubKey:   pubKey,
		PrivKey:  privKey,
		LastStep: stepNone,
		filePath: "",
		Signer:   NewDefaultSigner(privKey),
	}
}

func LoadPrivValidator(filePath string) *PrivValidator {
	privValJSONBytes, err := ioutil.ReadFile(filePath)
	if err != nil {
		Exit(err.Error())
	}
	privVal := PrivValidator{}
	err = json.Unmarshal(privValJSONBytes, &privVal)
	if err != nil {
		Exit(Fmt("Error reading PrivValidator from %v: %v\n", filePath, err))
	}

	privVal.filePath = filePath
	privVal.Signer = NewDefaultSigner(privVal.PrivKey)
	privVal.setPubKeyAndAddress()
	return &privVal
}

func LoadOrGenPrivValidator(filePath string, logger log.Logger) *PrivValidator {
	var privValidator *PrivValidator
	if _, err := os.Stat(filePath); err == nil {
		privValidator = LoadPrivValidator(filePath)
		logger.Info("Loaded PrivValidator",
			"file", filePath, "privValidator", privValidator)
	} else {
		privValidator = GenPrivValidator()
		privValidator.SetFile(filePath)
		privValidator.Save()
		logger.Info("Generated PrivValidator", "file", filePath)
	}
	return privValidator
}

func (privVal *PrivValidator) SetFile(filePath string) {
	privVal.mtx.Lock()
	defer privVal.mtx.Unlock()
	privVal.filePath = filePath
}

func (privVal *PrivValidator) Save() {
	privVal.mtx.Lock()
	defer privVal.mtx.Unlock()
	privVal.save()
}

func (privVal *PrivValidator) save() {
	if privVal.filePath == "" {
		PanicSanity("Cannot save PrivValidator: filePath not set")
	}
	jsonBytes, err := json.Marshal(privVal)
	if err != nil {
		// `@; BOOM!!!
		PanicCrisis(err)
	}
	err = WriteFileAtomic(privVal.filePath, jsonBytes, 0600)
	if err != nil {
		// `@; BOOM!!!
		PanicCrisis(err)
	}
}

// NOTE: Unsafe!
func (privVal *PrivValidator) Reset() {
	privVal.LastHeight = 0
	privVal.LastRound = 0
	privVal.LastStep = 0
	privVal.LastSignature = crypto.Signature{}
	privVal.LastSignBytes = nil
	privVal.Save()
}

func (privVal *PrivValidator) GetAddress() []byte {
	return privVal.Address
}

func (privVal *PrivValidator) SignVote(chainID string, vote *Vote) error {
	privVal.mtx.Lock()
	defer privVal.mtx.Unlock()
	signature, err := privVal.signBytesHRS(vote.Height, vote.Round, voteToStep(vote), SignBytes(chainID, vote))
	if err != nil {
		return errors.New(Fmt("Error signing vote: %v", err))
	}
	vote.Signature = signature
	return nil
}

func (privVal *PrivValidator) SignProposal(chainID string, proposal *Proposal) error {
	privVal.mtx.Lock()
	defer privVal.mtx.Unlock()
	signature, err := privVal.signBytesHRS(proposal.Height, proposal.Round, stepPropose, SignBytes(chainID, proposal))
	if err != nil {
		return fmt.Errorf("Error signing proposal: %v", err)
	}
	proposal.Signature = signature
	return nil
}

// check if there's a regression. Else sign and write the hrs+signature to disk
func (privVal *PrivValidator) signBytesHRS(height, round int, step int8, signBytes []byte) (crypto.Signature, error) {
	sig := crypto.Signature{}
	// If height regression, err
	if privVal.LastHeight > height {
		return sig, errors.New("Height regression")
	}
	// More cases for when the height matches
	if privVal.LastHeight == height {
		// If round regression, err
		if privVal.LastRound > round {
			return sig, errors.New("Round regression")
		}
		// If step regression, err
		if privVal.LastRound == round {
			if privVal.LastStep > step {
				return sig, errors.New("Step regression")
			} else if privVal.LastStep == step {
				if privVal.LastSignBytes != nil {
					if privVal.LastSignature.Empty() {
						PanicSanity("privVal: LastSignature is nil but LastSignBytes is not!")
					}
					// so we dont sign a conflicting vote or proposal
					// NOTE: proposals are non-deterministic (include time),
					// so we can actually lose them, but will still never sign conflicting ones
					if bytes.Equal(privVal.LastSignBytes, signBytes) {
						// log.Notice("Using privVal.LastSignature", "sig", privVal.LastSignature)
						return privVal.LastSignature, nil
					}
				}
				return sig, errors.New("Step regression")
			}
		}
	}

	// Sign
	sig = privVal.Sign(signBytes)

	// Persist height/round/step
	privVal.LastHeight = height
	privVal.LastRound = round
	privVal.LastStep = step
	privVal.LastSignature = sig
	privVal.LastSignBytes = signBytes
	privVal.save()

	return sig, nil

}

func (privVal *PrivValidator) SignHeartbeat(chainID string, heartbeat *Heartbeat) error {
	privVal.mtx.Lock()
	defer privVal.mtx.Unlock()
	heartbeat.Signature = privVal.Sign(SignBytes(chainID, heartbeat))
	return nil
}

func (privVal *PrivValidator) String() string {
	return fmt.Sprintf("PrivValidator{%v LH:%v, LR:%v, LS:%v}", privVal.Address, privVal.LastHeight, privVal.LastRound, privVal.LastStep)
}

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

type PrivValidatorsByAddress []*PrivValidator

func (pvs PrivValidatorsByAddress) Len() int {
	return len(pvs)
}

func (pvs PrivValidatorsByAddress) Less(i, j int) bool {
	return bytes.Compare(pvs[i].Address, pvs[j].Address) == -1
}

func (pvs PrivValidatorsByAddress) Swap(i, j int) {
	it := pvs[i]
	pvs[i] = pvs[j]
	pvs[j] = it
}