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tuple.go
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tuple.go
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package tuple
import (
"bytes"
"encoding/json"
"reflect"
)
// Some builds a Tupe when value is present.
func Some[T any](value T) Tuple[T] {
return Tuple[T]{
isPresent: true,
value: value,
}
}
// Tuple Wrapper for structs that encodes/decodes json as a tuple, rather than dict
type Tuple[T any] struct {
isPresent bool
value T
}
// Value returns the underlying struct
func (t Tuple[T]) Value() T {
return t.value
}
// MarshalJSON custom marshaller for tuple wrapped structs
func (t Tuple[T]) MarshalJSON() ([]byte, error) {
v := reflect.ValueOf(t.value)
values := make([]interface{}, v.NumField())
for i := 0; i < v.NumField(); i++ {
values[i] = v.Field(i).Interface()
}
return json.Marshal(values)
}
// UnmarshalJSON decodes Option from json.
// This works by creating a temp []interface{}, where each item in the slice is a pointer to the fields of the underlying
// tuple struct. Since it's pre-filled with pointers, unmarshal fills the pointers and checks the types
func (t *Tuple[T]) UnmarshalJSON(b []byte) error {
if bytes.Equal(b, []byte("null")) {
t.isPresent = false
return nil
}
v := reflect.ValueOf(&t.value).Elem()
tmpMap := make([]interface{}, v.NumField())
tmv := reflect.ValueOf(&tmpMap).Elem()
for i := 0; i < v.NumField(); i++ {
field := v.Field(i)
tmv.Index(i).Set(field.Addr())
}
err := json.Unmarshal(b, &tmpMap)
if err != nil {
return err
}
t.isPresent = true
return nil
}