type ClauseBuilder func(Clause, Builder)

type Writer interface {
	WriteByte(byte) error
	WriteString(string) (int, error)
}

// Builder builder interface
type Builder interface {
	Writer
	WriteQuoted(field interface{})
	AddVar(Writer, ...interface{})
	AddError(error) error
}

// Clause
type Clause struct {
	Name                string // WHERE
	BeforeExpression    Expression

	return stmt.SQL.WriteString(str)
}

// WriteByte write byte
func (stmt *Statement) WriteByte(c byte) error {
	return stmt.SQL.WriteByte(c)
}

// WriteQuoted write quoted value
func (stmt *Statement) WriteQuoted(value interface{}) {
	stmt.QuoteTo(&stmt.SQL, value)
}

// QuoteTo write quoted value to writer
func (stmt *Statement) QuoteTo(writer clause.Writer, field interface{}) {

type Gt Eq

func (gt Gt) Build(builder Builder) {
	builder.WriteQuoted(gt.Column)
	builder.WriteString(" > ")
	builder.AddVar(builder, gt.Value)
}

func (gt Gt) NegationBuild(builder Builder) {
	Lte(gt).Build(builder)
}

// Gte greater than or equal to for where
type Gte Eq

func (gte Gte) Build(builder Builder) {
	builder.WriteQuoted(gte.Column)
	builder.WriteString(" >= ")

		for idx, assignment := range set {
			if idx > 0 {
				builder.WriteByte(',')
			}
			builder.WriteQuoted(assignment.Column)
			builder.WriteByte('=')
			builder.AddVar(builder, assignment.Value)
		}
	} else {
		builder.WriteQuoted(Column{Name: PrimaryKey})
		builder.WriteByte('=')
		builder.WriteQuoted(Column{Name: PrimaryKey})
	}
}

// MergeClause merge assignments clauses