package featuremgmt

import (
	"bytes"
	"encoding/json"
)

type FeatureToggles interface {
	IsEnabled(flag string) bool
}

// FeatureFlagState indicates the quality level
type FeatureFlagState int

const (
	// FeatureStateUnknown indicates that no state is specified
	FeatureStateUnknown FeatureFlagState = iota

	// FeatureStateAlpha the feature is in active development and may change at any time
	FeatureStateAlpha

	// FeatureStateBeta the feature is still in development, but settings will have migrations
	FeatureStateBeta

	// FeatureStateStable this is a stable feature
	FeatureStateStable

	// FeatureStateDeprecated the feature will be removed in the future
	FeatureStateDeprecated
)

func (s FeatureFlagState) String() string {
	switch s {
	case FeatureStateAlpha:
		return "alpha"
	case FeatureStateBeta:
		return "beta"
	case FeatureStateStable:
		return "stable"
	case FeatureStateDeprecated:
		return "deprecated"
	case FeatureStateUnknown:
	}
	return "unknown"
}

// MarshalJSON marshals the enum as a quoted json string
func (s FeatureFlagState) MarshalJSON() ([]byte, error) {
	buffer := bytes.NewBufferString(`"`)
	buffer.WriteString(s.String())
	buffer.WriteString(`"`)
	return buffer.Bytes(), nil
}

// UnmarshalJSON unmarshals a quoted json string to the enum value
func (s *FeatureFlagState) UnmarshalJSON(b []byte) error {
	var j string
	err := json.Unmarshal(b, &j)
	if err != nil {
		return err
	}

	switch j {
	case "alpha":
		*s = FeatureStateAlpha

	case "beta":
		*s = FeatureStateBeta

	case "stable":
		*s = FeatureStateStable

	case "deprecated":
		*s = FeatureStateDeprecated

	default:
		*s = FeatureStateUnknown
	}
	return nil
}

type FeatureFlag struct {
	Name        string           `json:"name" yaml:"name"` // Unique name
	Description string           `json:"description"`
	State       FeatureFlagState `json:"state,omitempty"`
	DocsURL     string           `json:"docsURL,omitempty"`

	// CEL-GO expression.  Using the value "true" will mean this is on by default
	Expression string `json:"expression,omitempty"`

	// Special behavior flags
	RequiresDevMode bool `json:"requiresDevMode,omitempty"` // can not be enabled in production
	RequiresRestart bool `json:"requiresRestart,omitempty"` // The server must be initialized with the value
	RequiresLicense bool `json:"requiresLicense,omitempty"` // Must be enabled in the license
	FrontendOnly    bool `json:"frontend,omitempty"`        // change is only seen in the frontend
}