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package lite
import (
"github.com/tendermint/tendermint/types"
liteErr "github.com/tendermint/tendermint/lite/errors"
)
var _ Certifier = &Dynamic{}
// Dynamic uses a Static for Certify, but adds an
// Update method to allow for a change of validators.
//
// You can pass in a FullCommit with another validator set,
// and if this is a provably secure transition (< 1/3 change,
// sufficient signatures), then it will update the
// validator set for the next Certify call.
// For security, it will only follow validator set changes
// going forward.
type Dynamic struct {
cert *Static
lastHeight int64
}
// NewDynamic returns a new dynamic certifier.
func NewDynamic(chainID string, vals *types.ValidatorSet, height int64) *Dynamic {
return &Dynamic{
cert: NewStatic(chainID, vals),
lastHeight: height,
}
}
// ChainID returns the chain id of this certifier.
func (c *Dynamic) ChainID() string {
return c.cert.ChainID()
}
// Validators returns the validators of this certifier.
func (c *Dynamic) Validators() *types.ValidatorSet {
return c.cert.vSet
}
// Hash returns the hash of this certifier.
func (c *Dynamic) Hash() []byte {
return c.cert.Hash()
}
// LastHeight returns the last height of this certifier.
func (c *Dynamic) LastHeight() int64 {
return c.lastHeight
}
// Certify will verify whether the commit is valid and will update the height if it is or return an
// error if it is not.
func (c *Dynamic) Certify(check Commit) error {
err := c.cert.Certify(check)
if err == nil {
// update last seen height if input is valid
c.lastHeight = check.Height()
}
return err
}
// Update will verify if this is a valid change and update
// the certifying validator set if safe to do so.
//
// Returns an error if update is impossible (invalid proof or IsTooMuchChangeErr)
func (c *Dynamic) Update(fc FullCommit) error {
// ignore all checkpoints in the past -> only to the future
h := fc.Height()
if h <= c.lastHeight {
return liteErr.ErrPastTime()
}
// first, verify if the input is self-consistent....
err := fc.ValidateBasic(c.ChainID())
if err != nil {
return err
}
// now, make sure not too much change... meaning this commit
// would be approved by the currently known validator set
// as well as the new set
commit := fc.Commit.Commit
err = c.Validators().VerifyCommitAny(fc.Validators, c.ChainID(),
commit.BlockID, h, commit)
if err != nil {
return liteErr.ErrTooMuchChange()
}
// looks good, we can update
c.cert = NewStatic(c.ChainID(), fc.Validators)
c.lastHeight = h
return nil
}