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package builder
import (
"bytes"
"io"
)
type Writer interface {
io.Writer
Append(...interface{})
}
type stringWriter struct {
writer *bytes.Buffer
buffer []byte
args []interface{}
}
func NewWriter() *stringWriter {
w := &stringWriter{}
w.writer = bytes.NewBuffer(w.buffer)
return w
}
func (s *stringWriter) Write(buf []byte) (int, error) {
return s.writer.Write(buf)
}
func (s *stringWriter) Append(args ...interface{}) {
s.args = append(s.args, args...)
}
type Cond interface {
WriteTo(Writer) error
And(...Cond) Cond
Or(...Cond) Cond
IsValid() bool
}
type condEmpty struct{}
var _ Cond = condEmpty{}
func NewCond() Cond {
return condEmpty{}
}
func (condEmpty) WriteTo(w Writer) error {
return nil
}
func (condEmpty) And(conds ...Cond) Cond {
return And(conds...)
}
func (condEmpty) Or(conds ...Cond) Cond {
return Or(conds...)
}
func (condEmpty) IsValid() bool {
return false
}
func condToSQL(cond Cond) (string, []interface{}, error) {
if cond == nil || !cond.IsValid() {
return "", nil, nil
}
w := NewWriter()
if err := cond.WriteTo(w); err != nil {
return "", nil, err
}
return w.writer.String(), w.args, nil
}
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