package state

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"time"

	cmn "github.com/tendermint/tmlibs/common"
	dbm "github.com/tendermint/tmlibs/db"

	wire "github.com/tendermint/go-wire"

	"github.com/tendermint/tendermint/types"
)

// database keys
var (
	stateKey = []byte("stateKey")
)

func calcValidatorsKey(height int64) []byte {
	return []byte(cmn.Fmt("validatorsKey:%v", height))
}

func calcConsensusParamsKey(height int64) []byte {
	return []byte(cmn.Fmt("consensusParamsKey:%v", height))
}

func calcABCIResponsesKey(height int64) []byte {
	return []byte(cmn.Fmt("abciResponsesKey:%v", height))
}

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

// State is a short description of the latest committed block of the Tendermint consensus.
// It keeps all information necessary to validate new blocks,
// including the last validator set and the consensus params.
// All fields are exposed so the struct can be easily serialized,
// but none of them should be mutated directly.
// Instead, use state.Copy() ro state.NextState(...).
// NOTE: not goroutine-safe.
type State struct {
	// Immutable
	ChainID string

	// LastBlockHeight=0 at genesis (ie. block(H=0) does not exist)
	LastBlockHeight  int64
	LastBlockTotalTx int64
	LastBlockID      types.BlockID
	LastBlockTime    time.Time

	// LastValidators is used to validate block.LastCommit.
	// Validators are persisted to the database separately every time they change,
	// so we can query for historical validator sets.
	// Note that if s.LastBlockHeight causes a valset change,
	// we set s.LastHeightValidatorsChanged = s.LastBlockHeight + 1
	Validators                  *types.ValidatorSet
	LastValidators              *types.ValidatorSet
	LastHeightValidatorsChanged int64

	// Consensus parameters used for validating blocks.
	// Changes returned by EndBlock and updated after Commit.
	ConsensusParams                  types.ConsensusParams
	LastHeightConsensusParamsChanged int64

	// Merkle root of the results from executing prev block
	LastResultsHash []byte

	// The latest AppHash we've received from calling abci.Commit()
	AppHash []byte
}

// Copy makes a copy of the State for mutating.
func (s State) Copy() State {
	return State{
		ChainID: s.ChainID,

		LastBlockHeight:  s.LastBlockHeight,
		LastBlockTotalTx: s.LastBlockTotalTx,
		LastBlockID:      s.LastBlockID,
		LastBlockTime:    s.LastBlockTime,

		Validators:                  s.Validators.Copy(),
		LastValidators:              s.LastValidators.Copy(),
		LastHeightValidatorsChanged: s.LastHeightValidatorsChanged,

		ConsensusParams:                  s.ConsensusParams,
		LastHeightConsensusParamsChanged: s.LastHeightConsensusParamsChanged,

		AppHash: s.AppHash,

		LastResultsHash: s.LastResultsHash,
	}
}

// Save persists the State, the ValidatorsInfo, and the ConsensusParamsInfo to the database.
// It sets the given appHash on the state before persisting.
func (s State) Save(db dbm.DB, appHash []byte) {
	s.AppHash = appHash
	nextHeight := s.LastBlockHeight + 1
	saveValidatorsInfo(db, nextHeight, s.LastHeightValidatorsChanged, s.Validators)
	saveConsensusParamsInfo(db, nextHeight, s.LastHeightConsensusParamsChanged, s.ConsensusParams)
	db.SetSync(stateKey, s.Bytes())
}

// Equals returns true if the States are identical.
func (s State) Equals(s2 State) bool {
	return bytes.Equal(s.Bytes(), s2.Bytes())
}

// Bytes serializes the State using go-wire.
func (s State) Bytes() []byte {
	return wire.BinaryBytes(s)
}

// NextState returns a new State updated according to the header and responses.
func (s State) NextState(blockID types.BlockID, header *types.Header,
	abciResponses *ABCIResponses) (State, error) {

	// copy the valset so we can apply changes from EndBlock
	// and update s.LastValidators and s.Validators
	prevValSet := s.Validators.Copy()
	nextValSet := prevValSet.Copy()

	// update the validator set with the latest abciResponses
	lastHeightValsChanged := s.LastHeightValidatorsChanged
	if len(abciResponses.EndBlock.ValidatorUpdates) > 0 {
		err := updateValidators(nextValSet, abciResponses.EndBlock.ValidatorUpdates)
		if err != nil {
			return s, fmt.Errorf("Error changing validator set: %v", err)
		}
		// change results from this height but only applies to the next height
		lastHeightValsChanged = header.Height + 1
	}

	// Update validator accums and set state variables
	nextValSet.IncrementAccum(1)

	// update the params with the latest abciResponses
	nextParams := s.ConsensusParams
	lastHeightParamsChanged := s.LastHeightConsensusParamsChanged
	if abciResponses.EndBlock.ConsensusParamUpdates != nil {
		// NOTE: must not mutate s.ConsensusParams
		nextParams = s.ConsensusParams.Update(abciResponses.EndBlock.ConsensusParamUpdates)
		err := nextParams.Validate()
		if err != nil {
			return s, fmt.Errorf("Error updating consensus params: %v", err)
		}
		// change results from this height but only applies to the next height
		lastHeightParamsChanged = header.Height + 1
	}

	// NOTE: the AppHash has not been populated.
	// It will be filled on state.Save.
	return State{
		ChainID:                          s.ChainID,
		LastBlockHeight:                  header.Height,
		LastBlockTotalTx:                 s.LastBlockTotalTx + header.NumTxs,
		LastBlockID:                      blockID,
		LastBlockTime:                    header.Time,
		Validators:                       nextValSet,
		LastValidators:                   s.Validators.Copy(),
		LastHeightValidatorsChanged:      lastHeightValsChanged,
		ConsensusParams:                  nextParams,
		LastHeightConsensusParamsChanged: lastHeightParamsChanged,
		LastResultsHash:                  abciResponses.ResultsHash(),
		AppHash:                          nil,
	}, nil
}

// GetValidators returns the last and current validator sets.
func (s State) GetValidators() (last *types.ValidatorSet, current *types.ValidatorSet) {
	return s.LastValidators, s.Validators
}

//------------------------------------------------------------------------
// Genesis

// MakeGenesisStateFromFile reads and unmarshals state from the given
// file.
//
// Used during replay and in tests.
func MakeGenesisStateFromFile(genDocFile string) (*State, error) {
	genDoc, err := MakeGenesisDocFromFile(genDocFile)
	if err != nil {
		return nil, err
	}
	return MakeGenesisState(genDoc)
}

// MakeGenesisDocFromFile reads and unmarshals genesis doc from the given file.
func MakeGenesisDocFromFile(genDocFile string) (*types.GenesisDoc, error) {
	genDocJSON, err := ioutil.ReadFile(genDocFile)
	if err != nil {
		return nil, fmt.Errorf("Couldn't read GenesisDoc file: %v", err)
	}
	genDoc, err := types.GenesisDocFromJSON(genDocJSON)
	if err != nil {
		return nil, fmt.Errorf("Error reading GenesisDoc: %v", err)
	}
	return genDoc, nil
}

// MakeGenesisState creates state from types.GenesisDoc.
func MakeGenesisState(genDoc *types.GenesisDoc) (*State, error) {
	err := genDoc.ValidateAndComplete()
	if err != nil {
		return nil, fmt.Errorf("Error in genesis file: %v", err)
	}

	// Make validators slice
	validators := make([]*types.Validator, len(genDoc.Validators))
	for i, val := range genDoc.Validators {
		pubKey := val.PubKey
		address := pubKey.Address()

		// Make validator
		validators[i] = &types.Validator{
			Address:     address,
			PubKey:      pubKey,
			VotingPower: val.Power,
		}
	}

	return &State{

		ChainID: genDoc.ChainID,

		LastBlockHeight: 0,
		LastBlockID:     types.BlockID{},
		LastBlockTime:   genDoc.GenesisTime,

		Validators:                  types.NewValidatorSet(validators),
		LastValidators:              types.NewValidatorSet(nil),
		LastHeightValidatorsChanged: 1,

		ConsensusParams:                  *genDoc.ConsensusParams,
		LastHeightConsensusParamsChanged: 1,

		AppHash: genDoc.AppHash,
	}, nil
}