enum.go

package jsonschema

import (
	"fmt"
	"reflect"
	"strings"
)

// EvaluateEnum checks if the data's value matches one of the enumerated values specified in the schema.
// According to the JSON Schema Draft 2020-12:
//   - The value of the "enum" keyword must be an array.
//   - This array should have at least one element, and all elements should be unique.
//   - An instance validates successfully against this keyword if its value is equal to one of the elements in the array.
//   - Elements in the array might be of any type, including null.
//
// This method ensures that the data instance conforms to the enumerated values defined in the schema.
// If the instance does not match any of the enumerated values, it returns a EvaluationError detailing the allowed values.
//
// Reference: https://json-schema.org/draft/2020-12/json-schema-validation#name-enum
func evaluateEnum(schema *Schema, instance interface{}) *EvaluationError {
	if len(schema.Enum) == 0 {
		return nil // No enum values, so no validation needed
	}

	allowed := make([]string, 0, len(schema.Enum))

	for _, enumValue := range schema.Enum {
		if reflect.DeepEqual(instance, enumValue) {
			return nil // Match found.
		}

		allowed = append(allowed, fmt.Sprintf("%v", enumValue))
	}

	// No match found.
	return NewEvaluationError("enum", "value_not_in_enum", "Value {received} should be one of the allowed values: {expected}", map[string]interface{}{
		"expected": strings.Join(allowed, ", "),
		"received": instance,
	})
}