// Package kubeedit is the write side of the Kubernetes integration: the
// console's edits become changes to ClientGroup, BlockList and DNSZone objects.
//
// It is the only code that writes to the cluster, and the runtime never
// imports it. Every spec is validated with the runtime's own converters
// (kubesource.Check*) before it is written, so the console cannot store an
// object the runtime would reject.
package kubeedit

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"reflect"
	"sort"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/util/validation"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/util/retry"

	"git.k8s-git-k6n.net/mats/fancy-dns/internal/kubesource"
)

// ActorAnnotation records who last changed an object through the console.
const ActorAnnotation = "fancydns.k6n.net/last-edited-by"

// ErrNotFound is returned when the object or record to change does not exist.
var ErrNotFound = errors.New("not found")

// Editor writes fancy-dns objects into one namespace.
type Editor struct {
	c  dynamic.Interface
	ns string
}

// New returns an Editor for namespace ns.
func New(c dynamic.Interface, ns string) *Editor { return &Editor{c: c, ns: ns} }

// Namespace is where objects are written.
func (e *Editor) Namespace() string { return e.ns }

func (e *Editor) res(gvr schema.GroupVersionResource) dynamic.ResourceInterface {
	return e.c.Resource(gvr).Namespace(e.ns)
}

func decodeSpec(u *unstructured.Unstructured, into any) error {
	raw, _ := u.Object["spec"].(map[string]any)
	if raw == nil {
		return nil
	}
	return runtime.DefaultUnstructuredConverter.FromUnstructured(raw, into)
}

func encodeSpec(spec any) (map[string]any, error) {
	// ToUnstructured wants a pointer; the specs are passed by value.
	v := reflect.New(reflect.TypeOf(spec))
	v.Elem().Set(reflect.ValueOf(spec))
	return runtime.DefaultUnstructuredConverter.ToUnstructured(v.Interface())
}

func sameSpec(a, b any) bool {
	x, _ := json.Marshal(a)
	y, _ := json.Marshal(b)
	return string(x) == string(y)
}

func checkName(kind, name string) error {
	if errs := validation.IsDNS1123Subdomain(name); len(errs) > 0 {
		return fmt.Errorf("%s name %q cannot be a Kubernetes object name (%s): use lowercase letters, digits, '-' and '.'", kind, name, errs[0])
	}
	return nil
}

func stamp(u *unstructured.Unstructured, actor string) {
	ann := u.GetAnnotations()
	if ann == nil {
		ann = map[string]string{}
	}
	if actor != "" {
		ann[ActorAnnotation] = actor
	}
	u.SetAnnotations(ann)
	labels := u.GetLabels()
	if labels == nil {
		labels = map[string]string{}
	}
	labels["app.kubernetes.io/managed-by"] = "fancy-dns-console"
	u.SetLabels(labels)
}

func newObject(kind, name string, spec any) (*unstructured.Unstructured, error) {
	raw, err := encodeSpec(spec)
	if err != nil {
		return nil, err
	}
	return &unstructured.Unstructured{Object: map[string]any{
		"apiVersion": kubesource.APIGroup + "/" + kubesource.Version,
		"kind":       kind,
		"metadata":   map[string]any{"name": name, "namespace": ""},
		"spec":       raw,
	}}, nil
}

// upsert creates the object or replaces its spec, retrying on conflict.
func (e *Editor) upsert(ctx context.Context, gvr schema.GroupVersionResource, kind, name, actor string, spec any) (*unstructured.Unstructured, error) {
	var out *unstructured.Unstructured
	err := retry.RetryOnConflict(retry.DefaultRetry, func() error {
		cur, err := e.res(gvr).Get(ctx, name, metav1.GetOptions{})
		if apierrors.IsNotFound(err) {
			obj, err := newObject(kind, name, spec)
			if err != nil {
				return err
			}
			obj.SetNamespace(e.ns)
			stamp(obj, actor)
			out, err = e.res(gvr).Create(ctx, obj, metav1.CreateOptions{})
			return err
		}
		if err != nil {
			return err
		}
		raw, err := encodeSpec(spec)
		if err != nil {
			return err
		}
		cur.Object["spec"] = raw
		stamp(cur, actor)
		out, err = e.res(gvr).Update(ctx, cur, metav1.UpdateOptions{})
		return err
	})
	return out, err
}

func (e *Editor) remove(ctx context.Context, gvr schema.GroupVersionResource, name string) error {
	err := e.res(gvr).Delete(ctx, name, metav1.DeleteOptions{})
	if apierrors.IsNotFound(err) {
		return fmt.Errorf("%w: %s", ErrNotFound, name)
	}
	return err
}

func (e *Editor) list(ctx context.Context, gvr schema.GroupVersionResource) ([]unstructured.Unstructured, error) {
	l, err := e.res(gvr).List(ctx, metav1.ListOptions{})
	if err != nil {
		return nil, err
	}
	sort.Slice(l.Items, func(i, j int) bool { return l.Items[i].GetName() < l.Items[j].GetName() })
	return l.Items, nil
}

// upsertRaw is upsert for a spec that is already unstructured.
func (e *Editor) upsertRaw(ctx context.Context, gvr schema.GroupVersionResource, kind, name, actor string, spec map[string]any, labels map[string]string) (*unstructured.Unstructured, error) {
	var out *unstructured.Unstructured
	err := retry.RetryOnConflict(retry.DefaultRetry, func() error {
		cur, err := e.res(gvr).Get(ctx, name, metav1.GetOptions{})
		if apierrors.IsNotFound(err) {
			obj := &unstructured.Unstructured{Object: map[string]any{
				"apiVersion": kubesource.APIGroup + "/" + kubesource.Version,
				"kind":       kind,
				"metadata":   map[string]any{"name": name, "namespace": e.ns},
				"spec":       spec,
			}}
			stamp(obj, actor)
			if len(labels) > 0 {
				merged := obj.GetLabels()
				for k, v := range labels {
					merged[k] = v
				}
				obj.SetLabels(merged)
			}
			out, err = e.res(gvr).Create(ctx, obj, metav1.CreateOptions{})
			return err
		}
		if err != nil {
			return err
		}
		cur.Object["spec"] = spec
		stamp(cur, actor)
		out, err = e.res(gvr).Update(ctx, cur, metav1.UpdateOptions{})
		return err
	})
	return out, err
}