manager.go

package fitcha

import "context"

type FeatureManager interface {
	Store() Storage

	Evaluate(context.Context, string) (bool, error)

	EvaluateExpr(context.Context, string, string) (bool, error)

	IsEnabled(context.Context, string) (bool, error)

	Enable(context.Context, string) error

	Disable(context.Context, string) error

	AvailableFeatures() []string

	EnabledFeatures() []string
}

type simpleFeatureManager struct {
	store Storage
}

func NewFeatureManager(store Storage) FeatureManager {
	return &simpleFeatureManager{
		store: store,
	}
}

func (sfm *simpleFeatureManager) Store() Storage {
	return sfm.store
}

func (sfm *simpleFeatureManager) IsEnabled(ctx context.Context, featureName string) (bool, error) {
	feature, err := sfm.Store().Find(featureName)
	if err != nil {
		return false, err
	}
	if !feature.IsEnabled {
		return false, ErrFeatureIsNotEnabled
	}
	return true, nil
}

func (sfm *simpleFeatureManager) Enable(ctx context.Context, featureName string) error {
	feature, err := sfm.Store().Find(featureName)
	if err != nil {
		return err
	}
	feature.IsEnabled = true
	sfm.Store().Update(feature)
	return nil
}

func (sfm *simpleFeatureManager) Disable(ctx context.Context, featureName string) error {
	feature, err := sfm.Store().Find(featureName)
	if err != nil {
		return err
	}
	feature.IsEnabled = false
	sfm.Store().Update(feature)
	return nil
}

func (sfm *simpleFeatureManager) Evaluate(ctx context.Context, featureName string) (bool, error) {
	feature, err := sfm.Store().Find(featureName)
	if err != nil {
		return false, err
	}
	if !feature.IsEnabled {
		return false, ErrFeatureIsNotEnabled
	}
	return sfm.EvaluateExpr(ctx, featureName, feature.Expr)
}

func (sfm *simpleFeatureManager) EvaluateExpr(ctx context.Context, featureName string, cond string) (bool, error) {
	feature, err := sfm.Store().Find(featureName)
	if err != nil {
		return false, err
	}

	if !feature.IsEnabled {
		return false, ErrFeatureIsNotEnabled
	}

	if cond == "" {
		return false, ErrEmptyExpression
	}
	return evaluateCondition(ctx, cond)
}

func (sfm *simpleFeatureManager) AvailableFeatures() []string {
	available := make([]string, 0)
	for _, f := range sfm.store.List() {
		available = append(available, string(f.Name))
	}
	return available
}

func (sfm *simpleFeatureManager) EnabledFeatures() []string {
	available := make([]string, 0)
	for _, f := range sfm.store.List() {
		if f.IsEnabled {
			available = append(available, string(f.Name))
		}
	}
	return available
}