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package survey
import (
"errors"
"fmt"
"reflect"
)
// Required does not allow an empty value
func Required(val interface{}) error {
// the reflect value of the result
value := reflect.ValueOf(val)
// if the value passed in is the zero value of the appropriate type
if isZero(value) && value.Kind() != reflect.Bool {
return errors.New("Value is required")
}
return nil
}
// MaxLength requires that the string is no longer than the specified value
func MaxLength(length int) Validator {
// return a validator that checks the length of the string
return func(val interface{}) error {
if str, ok := val.(string); ok {
// if the string is longer than the given value
if len([]rune(str)) > length {
// yell loudly
return fmt.Errorf("value is too long. Max length is %v", length)
}
} else {
// otherwise we cannot convert the value into a string and cannot enforce length
return fmt.Errorf("cannot enforce length on response of type %v", reflect.TypeOf(val).Name())
}
// the input is fine
return nil
}
}
// MinLength requires that the string is longer or equal in length to the specified value
func MinLength(length int) Validator {
// return a validator that checks the length of the string
return func(val interface{}) error {
if str, ok := val.(string); ok {
// if the string is shorter than the given value
if len([]rune(str)) < length {
// yell loudly
return fmt.Errorf("value is too short. Min length is %v", length)
}
} else {
// otherwise we cannot convert the value into a string and cannot enforce length
return fmt.Errorf("cannot enforce length on response of type %v", reflect.TypeOf(val).Name())
}
// the input is fine
return nil
}
}
// ComposeValidators is a variadic function used to create one validator from many.
func ComposeValidators(validators ...Validator) Validator {
// return a validator that calls each one sequentially
return func(val interface{}) error {
// execute each validator
for _, validator := range validators {
// if the answer's value is not valid
if err := validator(val); err != nil {
// return the error
return err
}
}
// we passed all validators, the answer is valid
return nil
}
}
// isZero returns true if the passed value is the zero object
func isZero(v reflect.Value) bool {
switch v.Kind() {
case reflect.Slice, reflect.Map:
return v.Len() == 0
}
// compare the types directly with more general coverage
return reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface())
}
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