Fantom-foundation/go-lachesis

package epochcheck

import (
    "errors"

    "github.com/Fantom-foundation/go-lachesis/inter"
    "github.com/Fantom-foundation/go-lachesis/inter/idx"
    "github.com/Fantom-foundation/go-lachesis/inter/pos"
    "github.com/Fantom-foundation/go-lachesis/lachesis"
)

var (
    // ErrNotRelevant indicates the event's epoch isn't equal to current epoch.
    ErrNotRelevant = errors.New("event is too old or too new")
    // ErrAuth indicates that event's creator isn't authorized to create events in current epoch.
    ErrAuth = errors.New("event creator isn't validator")
)

// DagReader is accessed by the validator to get the current state.
type DagReader interface {
    GetEpochValidators() (*pos.Validators, idx.Epoch)
}

// Checker which require only current epoch info
type Checker struct {
    config *lachesis.DagConfig
    reader DagReader
}

func New(config *lachesis.DagConfig, reader DagReader) *Checker {
    return &Checker{
        config: config,
        reader: reader,
    }
}

// Validate event
func (v *Checker) Validate(e *inter.Event) error {
    // check epoch first, because validators group is known only for the current epoch
    validators, epoch := v.reader.GetEpochValidators()
    if e.Epoch != epoch {
        return ErrNotRelevant
    }
    if !validators.Exists(e.Creator) {
        return ErrAuth
    }
    return nil
}