1 files changed, 65 insertions, 0 deletions
diff --git a/predict/options.go b/predict/options.go
new file mode 100644
index 0000000..df39437
--- /dev/null
+++ b/predict/options.go
@@ -0,0 +1,65 @@
+package predict
+
+import (
+	"fmt"
+	"github.com/posener/complete/v2"
+	"strings"
+)
+
+// Option provides prediction through options pattern.
+//
+// Usage:
+//
+//  func(o ...predict.Option) {
+//  	cfg := predict.Options(o)
+//  	// use cfg.Predict...
+//  }
+type Option func(*Config)
+
+// OptValues allows to set a desired set of valid values for the flag.
+func OptValues(values ...string) Option {
+	return OptPredictor(Set(values))
+}
+
+// OptPredictor allows to set a custom predictor.
+func OptPredictor(p complete.Predictor) Option {
+	return func(o *Config) { o.Predictor = p }
+}
+
+// OptCheck enforces the valid values on the predicted flag.
+func OptCheck() Option {
+	return func(o *Config) { o.check = true }
+}
+
+type Config struct {
+	complete.Predictor
+	check bool
+}
+
+func Options(os ...Option) Config {
+	var op Config
+	for _, f := range os {
+		f(&op)
+	}
+	return op
+}
+
+func (c Config) Predict(prefix string) []string {
+	if c.Predictor != nil {
+		return c.Predictor.Predict(prefix)
+	}
+	return nil
+}
+
+func (c Config) Check(value string) error {
+	predictions := c.Predictor.Predict(value)
+	if !c.check || len(predictions) == 0 {
+		return nil
+	}
+	for _, vv := range predictions {
+		if value == vv {
+			return nil
+		}
+	}
+	return fmt.Errorf("not in allowed values: %s", strings.Join(predictions, ","))
+}