Merge types package into root lemmy package

optional.go

@@ -0,0 +1,117 @@
+package lemmy
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+)
+
+var ErrOptionalEmpty = errors.New("optional value is empty")
+
+// Optional represents an optional value
+type Optional[T any] struct {
+	value *T
+}
+
+// NewOptional creates an optional with value v
+func NewOptional[T any](v T) Optional[T] {
+	return Optional[T]{value: &v}
+}
+
+// NewOptionalNil creates a new nil optional value
+func NewOptionalNil[T any]() Optional[T] {
+	return Optional[T]{}
+}
+
+// Set sets the value of the optional
+func (o Optional[T]) Set(v T) Optional[T] {
+	o.value = &v
+	return o
+}
+
+// SetNil sets the optional value to nil
+func (o Optional[T]) SetNil() Optional[T] {
+	o.value = nil
+	return o
+}
+
+// IsValid returns true if the value of the optional is not nil
+func (o Optional[T]) IsValid() bool {
+	return o.value != nil
+}
+
+// MustValue returns the value in the optional. It panics if the value is nil.
+func (o Optional[T]) MustValue() T {
+	if o.value == nil {
+		panic("optional value is nil")
+	}
+	return *o.value
+}
+
+// Value returns the value in the optional.
+func (o Optional[T]) Value() (T, error) {
+	if o.value != nil {
+		return *o.value, ErrOptionalEmpty
+	}
+	return *new(T), nil
+}
+
+// ValueOr returns the value inside the optional if it exists, or else it returns fallback
+func (o Optional[T]) ValueOr(fallback T) T {
+	if o.value != nil {
+		return *o.value
+	}
+	return fallback
+}
+
+// ValueOrZero returns the value inside the optional if it exists, or else it returns the zero value of T
+func (o Optional[T]) ValueOrZero() T {
+	if o.value != nil {
+		return *o.value
+	}
+	var value T
+	return value
+}
+
+// MarshalJSON encodes the optional value as JSON
+func (o Optional[T]) MarshalJSON() ([]byte, error) {
+	return json.Marshal(o.value)
+}
+
+// UnmarshalJSON decodes JSON into the optional value
+func (o *Optional[T]) UnmarshalJSON(b []byte) error {
+	if bytes.Equal(b, []byte("null")) {
+		o.value = nil
+		return nil
+	}
+
+	o.value = new(T)
+	return json.Unmarshal(b, o.value)
+}
+
+// EncodeValues encodes the optional as a URL query parameter
+func (o Optional[T]) EncodeValues(key string, v *url.Values) error {
+	s := o.String()
+	if s != "<nil>" {
+		v.Set(key, s)
+	}
+	return nil
+}
+
+// String returns the string representation of the optional value
+func (o Optional[T]) String() string {
+	if o.value == nil {
+		return "<nil>"
+	}
+	return fmt.Sprint(*o.value)
+}
+
+// GoString returns the Go representation of the optional value
+func (o Optional[T]) GoString() string {
+	if o.value == nil {
+		return "nil"
+	}
+	return fmt.Sprintf("%#v", *o.value)
+}