Fantom-foundation/go-lachesis

package migration

import (
    "errors"
    "fmt"

    "github.com/ethereum/go-ethereum/log"
    "golang.org/x/crypto/sha3"
)

// Migration is a migration step.
type Migration struct {
    name string
    exec func() error
    prev *Migration
}

// Begin with empty unique migration step.
func Begin(appName string) *Migration {
    return &Migration{
        name: appName,
    }
}

// Next creates next migration.
func (m *Migration) Next(name string, exec func() error) *Migration {
    if name == "" {
        panic("empty name")
    }

    if exec == nil {
        panic("empty exec")
    }

    return &Migration{
        name: name,
        exec: exec,
        prev: m,
    }
}

// ID is an uniq migration's id.
func (m *Migration) ID() string {
    digest := sha3.NewLegacyKeccak256()
    digest.Write([]byte(m.name))

    bytes := digest.Sum(nil)
    return fmt.Sprintf("%x", bytes)
}

// Exec method run migrations chain in order
func (m *Migration) Exec(curr IDStore) error {
    currID := curr.GetID()
    myID := m.ID()

    if m.veryFirst() {
        if currID != "" {
            return errors.New("unknown version: " + currID)
        }
        return nil
    }

    if currID == myID {
        return nil
    }

    err := m.prev.Exec(curr)
    if err != nil {
        return err
    }

    err = m.exec()
    if err != nil {
        log.Error("'"+m.name+"' migration failed", "err", err)
        return err
    }
    log.Warn("'" + m.name + "' migration has been applied")

    curr.SetID(myID)
    return nil
}

func (m *Migration) veryFirst() bool {
    return m.exec == nil
}

// IDs return list of migrations ids in chain
func (m *Migration) IDs() []string {
    if m.prev == nil {
        return []string{m.ID()}
    }

    return append(m.prev.IDs(), m.ID())
}