refactor

type ChangeLog struct {
	TableName     NullString
	LockTableName NullString

	Variables *vars.Variables

	ChangeSets []*ChangeSet
}

type ChangeSet struct {
	Id string

	Name   NullString
	Author NullString

	Tags []string

	Changers []Changer
}

type Changer interface {
	Up(ctx Context) ([]*Stmt, error)
	Down(ctx Context) ([]*Stmt, error)

	DTO() (dto.Changer, error)
}

type Column struct {
	Name string
	Type string

	IsNullable NullBool

	Default NullString

	Constraint *Constraint
}

type Constraint struct {
	IsUnique   NullBool
	UniqueName NullString

	IsPrimaryKey   NullBool
	PrimaryKeyName NullString
}

type Context interface {
	Expand(string) (string, error)
}

type CreateTable struct {
	Name string

	IfNotExists NullBool

	Columns []*Column
}

type Expander interface {
	Expand(Context) (string, error)
}

type ExpanderFunc func(Context) (string, error)

type NullBool struct {
	Raw   string
	Bool  bool
	Valid bool
}

type NullString struct {
	String string
	Valid  bool
}

type RawSql struct {
	UpStmts   []*Stmt
	DownStmts []*Stmt
	// contains filtered or unexported fields
}

type Stmt struct {
	Raw  string
	Args []interface{}
}

type UnknownDTOChangerError struct {
	dto.Changer
}