package coderd

import (
	"net/http"
	"reflect"

	"golang.org/x/xerrors"

	"github.com/coder/coder/coderd/audit"
	"github.com/coder/coder/coderd/features"
	"github.com/coder/coder/coderd/httpapi"
	"github.com/coder/coder/codersdk"
)

func NewMockFeaturesService(feats FeatureInterfaces) features.Service {
	return &featuresService{
		feats: &feats,
	}
}

type featuresService struct {
	feats *FeatureInterfaces
}

func (*featuresService) EntitlementsAPI(rw http.ResponseWriter, _ *http.Request) {
	feats := make(map[string]codersdk.Feature)
	for _, f := range codersdk.FeatureNames {
		feats[f] = codersdk.Feature{
			Entitlement: codersdk.EntitlementNotEntitled,
			Enabled:     false,
		}
	}
	httpapi.Write(rw, http.StatusOK, codersdk.Entitlements{
		Features:   feats,
		Warnings:   []string{},
		HasLicense: false,
	})
}

// Get returns the implementations for feature interfaces. Parameter `s` must be a pointer to a
// struct type containing feature interfaces as fields.  The AGPL featureService always returns the
// "disabled" version of the feature interface because it doesn't include any enterprise features
// by definition.
func (f *featuresService) Get(ps any) error {
	if reflect.TypeOf(ps).Kind() != reflect.Pointer {
		return xerrors.New("input must be pointer to struct")
	}
	vs := reflect.ValueOf(ps).Elem()
	if vs.Kind() != reflect.Struct {
		return xerrors.New("input must be pointer to struct")
	}
	for i := 0; i < vs.NumField(); i++ {
		vf := vs.Field(i)
		tf := vf.Type()
		if tf.Kind() != reflect.Interface {
			return xerrors.Errorf("fields of input struct must be interfaces: %s", tf.String())
		}
		err := f.setImplementation(vf, tf)
		if err != nil {
			return err
		}
	}
	return nil
}

// setImplementation finds the correct implementation for the field's type, and sets it on the
// struct.  It returns an error if unsuccessful
func (f *featuresService) setImplementation(vf reflect.Value, tf reflect.Type) error {
	feats := f.feats
	if feats == nil {
		feats = &DisabledImplementations
	}

	// when we get more than a few features it might make sense to have a data structure for finding
	// the correct implementation that's faster than just a linear search, but for now just spin
	// through the implementations we have.
	vd := reflect.ValueOf(*feats)
	for j := 0; j < vd.NumField(); j++ {
		vdf := vd.Field(j)
		if vdf.Type() == tf {
			vf.Set(vdf)
			return nil
		}
	}
	return xerrors.Errorf("unable to find implementation of interface %s", tf.String())
}

// FeatureInterfaces contains a field for each interface controlled by an enterprise feature.
type FeatureInterfaces struct {
	Auditor audit.Auditor
}

// DisabledImplementations includes all the implementations of turned-off features.  There are no
// turned-on implementations in AGPL code.
var DisabledImplementations = FeatureInterfaces{
	Auditor: audit.NewNop(),
}