package featuremgmt

import (
	"bytes"
	"context"
	"encoding/json"
)

type FeatureToggles interface {
	// Check if a feature is enabled for a given context.
	// The settings may be per user, tenant, or globally set in the cloud
	IsEnabled(ctx context.Context, flag string) bool

	// Check if a flag is configured globally.  For now, this is the same
	// as the function above, however it will move to only checking flags that
	// are configured by the operator and shared across all tenants.
	// Use of global feature flags should be limited and careful as they require
	// a full server restart for a change to take place.
	IsEnabledGlobally(flag string) bool
}

// FeatureFlagStage indicates the quality level
type FeatureFlagStage int

const (
	// FeatureStageUnknown indicates that no state is specified
	FeatureStageUnknown FeatureFlagStage = iota

	// FeatureStageExperimental -- Does this work for Grafana Labs?
	FeatureStageExperimental

	// FeatureStagePrivatePreview -- Does this work for a limited number of customers?
	FeatureStagePrivatePreview

	// FeatureStagePublicPreview -- Does this work for most customers?
	FeatureStagePublicPreview

	// FeatureStageGeneralAvailability -- Feature is available to all applicable customers
	FeatureStageGeneralAvailability

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

func (s FeatureFlagStage) String() string {
	switch s {
	case FeatureStageExperimental:
		return "experimental"
	case FeatureStagePrivatePreview:
		return "privatePreview"
	case FeatureStagePublicPreview:
		return "preview"
	case FeatureStageGeneralAvailability:
		return "GA"
	case FeatureStageDeprecated:
		return "deprecated"
	case FeatureStageUnknown:
	}
	return "unknown"
}

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

	switch j {
	case "alpha":
		fallthrough
	case "experimental":
		*s = FeatureStageExperimental

	case "privatePreview":
		*s = FeatureStagePrivatePreview

	case "beta":
		fallthrough
	case "preview":
		*s = FeatureStagePublicPreview

	case "stable":
		fallthrough
	case "ga":
		fallthrough
	case "GA":
		*s = FeatureStageGeneralAvailability

	case "deprecated":
		*s = FeatureStageDeprecated

	default:
		*s = FeatureStageUnknown
	}
	return nil
}

type FeatureFlag struct {
	Name        string           `json:"name" yaml:"name"` // Unique name
	Description string           `json:"description"`
	Stage       FeatureFlagStage `json:"stage,omitempty"`
	DocsURL     string           `json:"docsURL,omitempty"`

	// Owner person or team that owns this feature flag
	Owner codeowner `json:"-"`

	// 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
	// This flag is currently unused.
	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
	HideFromDocs      bool  `json:"hideFromDocs,omitempty"`      // don't add the values to docs
	HideFromAdminPage bool  `json:"hideFromAdminPage,omitempty"` // don't display the feature in the admin page - add a comment with the reasoning
	AllowSelfServe    *bool `json:"allowSelfServe,omitempty"`    // allow admin users to toggle the feature state from the admin page; this is required for GA toggles only

	// This field is only for the feature management API. To enable your feature toggle by default, use `Expression`.
	Enabled bool `json:"enabled,omitempty"`
}

type UpdateFeatureTogglesCommand struct {
	FeatureToggles []FeatureToggleDTO `json:"featureToggles"`
}

type FeatureToggleDTO struct {
	Name        string `json:"name" binding:"Required"`
	Description string `json:"description"`
	Enabled     bool   `json:"enabled"`
	ReadOnly    bool   `json:"readOnly,omitempty"`
}

type FeatureManagerState struct {
	RestartRequired bool `json:"restartRequired"`
	AllowEditing    bool `json:"allowEditing"`
}