package clustercache

import (
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/rancher/steve/pkg/attributes"
	"github.com/rancher/steve/pkg/schema"
	"github.com/rancher/steve/pkg/schemaserver/types"
	"github.com/rancher/wrangler/pkg/generic"
	"github.com/rancher/wrangler/pkg/merr"
	"github.com/sirupsen/logrus"
	"k8s.io/apimachinery/pkg/api/meta"
	"k8s.io/apimachinery/pkg/runtime"
	schema2 "k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/dynamic/dynamicinformer"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"
)

var (
	logOnce = sync.Once{}
)

type Handler func(gvr schema2.GroupVersionResource, key string, obj runtime.Object) error

type ClusterCache interface {
	AddController(gvk schema2.GroupVersionKind, informer cache.SharedIndexInformer)
	List(gvr schema2.GroupVersionResource) []interface{}
	OnAdd(ctx context.Context, handler Handler)
	OnRemove(ctx context.Context, handler Handler)
	OnChange(ctx context.Context, handler Handler)
	OnSchemas(schemas *schema.Collection) error
}

type event struct {
	add bool
	gvr schema2.GroupVersionResource
	obj runtime.Object
}

type watcher struct {
	ctx      context.Context
	cancel   func()
	informer cache.SharedIndexInformer
	gvk      schema2.GroupVersionKind
	gvr      schema2.GroupVersionResource
	start    bool
}

type clusterCache struct {
	sync.RWMutex

	ctx               context.Context
	typed             map[schema2.GroupVersionKind]cache.SharedIndexInformer
	informerFactory   dynamicinformer.DynamicSharedInformerFactory
	controllerFactory generic.ControllerManager
	watchers          map[schema2.GroupVersionResource]*watcher
	workqueue         workqueue.DelayingInterface

	addHandlers    cancelCollection
	removeHandlers cancelCollection
	changeHandlers cancelCollection
}

func NewClusterCache(ctx context.Context, client dynamic.Interface) ClusterCache {
	c := &clusterCache{
		ctx:             ctx,
		typed:           map[schema2.GroupVersionKind]cache.SharedIndexInformer{},
		informerFactory: dynamicinformer.NewDynamicSharedInformerFactory(client, 2*time.Hour),
		watchers:        map[schema2.GroupVersionResource]*watcher{},
		workqueue:       workqueue.NewNamedDelayingQueue("cluster-cache"),
	}
	go c.start()
	return c
}

func (h *clusterCache) AddController(gvk schema2.GroupVersionKind, informer cache.SharedIndexInformer) {
	h.typed[gvk] = informer
}

func validSchema(schema *types.APISchema) bool {
	canList := false
	canWatch := false
	for _, verb := range attributes.Verbs(schema) {
		switch verb {
		case "list":
			canList = true
		case "watch":
			canWatch = true
		}
	}

	if !canList || !canWatch {
		return false
	}

	if attributes.PreferredVersion(schema) != "" {
		return false
	}

	if attributes.PreferredGroup(schema) != "" {
		return false
	}

	return true
}

func (h *clusterCache) addResourceEventHandler(gvr schema2.GroupVersionResource, informer cache.SharedIndexInformer) {
	informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			if rObj, ok := obj.(runtime.Object); ok {
				h.workqueue.Add(event{
					add: true,
					obj: rObj,
					gvr: gvr,
				})
			}
		},
		DeleteFunc: func(obj interface{}) {
			if rObj, ok := obj.(runtime.Object); ok {
				h.workqueue.Add(event{
					obj: rObj,
					gvr: gvr,
				})
			}
		},
	})
}

func (h *clusterCache) OnSchemas(schemas *schema.Collection) error {
	h.Lock()
	defer h.Unlock()

	var (
		toStart = map[schema2.GroupVersionResource]*watcher{}
		gvrs    = map[schema2.GroupVersionResource]bool{}
	)

	for _, id := range schemas.IDs() {
		schema := schemas.Schema(id)
		if !validSchema(schema) {
			continue
		}

		gvr := attributes.GVR(schema)
		gvk := attributes.GVK(schema)
		gvrs[gvr] = true

		w := h.watchers[gvr]
		if w != nil {
			continue
		}

		ctx, cancel := context.WithCancel(h.ctx)
		w = &watcher{
			ctx:      ctx,
			cancel:   cancel,
			gvk:      gvk,
			gvr:      gvr,
			informer: h.typed[gvk],
		}
		toStart[gvr] = w

		if w.informer == nil {
			w.informer = h.informerFactory.ForResource(gvr).Informer()
			w.start = true
		}

		logrus.Infof("Watching counts for %s", gvk.String())
		h.addResourceEventHandler(gvr, w.informer)
		name := fmt.Sprintf("meta %s", gvk)
		h.controllerFactory.AddHandler(ctx, gvk, w.informer, name, func(key string, obj runtime.Object) (object runtime.Object, e error) {
			return callAll(h.changeHandlers.List(), gvr, key, obj)
		})
	}

	for gvr, w := range h.watchers {
		if !gvrs[gvr] {
			logrus.Infof("Stopping count watch on %s", gvr)
			w.cancel()
			delete(h.watchers, gvr)
		}
	}

	for _, w := range toStart {
		if !w.start {
			continue
		}
		go w.informer.Run(w.ctx.Done())
	}

	for _, w := range toStart {
		cache.WaitForCacheSync(w.ctx.Done(), w.informer.HasSynced)
	}

	var errs []error
	for _, w := range toStart {
		if err := h.controllerFactory.EnsureStart(w.ctx, w.gvk, 5); err != nil {
			errs = append(errs, err)
		}
		h.watchers[w.gvr] = w
	}

	return merr.NewErrors(errs...)
}

func (h *clusterCache) List(gvr schema2.GroupVersionResource) []interface{} {
	h.RLock()
	defer h.RUnlock()

	w, ok := h.watchers[gvr]
	if !ok {
		return nil
	}

	return w.informer.GetStore().List()
}

func (h *clusterCache) start() {
	for {
		eventObj, ok := h.workqueue.Get()
		if ok {
			break
		}

		event := eventObj.(event)
		w := h.watchers[event.gvr]
		if w == nil {
			continue
		}

		key := toKey(event.obj)
		if event.add {
			_, err := callAll(h.addHandlers.List(), event.gvr, key, event.obj)
			if err != nil {
				logrus.Errorf("failed to handle add event: %v", err)
			}
		} else {
			_, err := callAll(h.removeHandlers.List(), event.gvr, key, event.obj)
			if err != nil {
				logrus.Errorf("failed to handle remove event: %v", err)
			}
		}
	}
}

func toKey(obj runtime.Object) string {
	meta, err := meta.Accessor(obj)
	if err != nil {
		return ""
	}
	ns := meta.GetNamespace()
	if ns == "" {
		return meta.GetName()
	}
	return ns + "/" + meta.GetName()
}

func (h *clusterCache) OnAdd(ctx context.Context, handler Handler) {
	h.addHandlers.Add(ctx, handler)
}

func (h *clusterCache) OnRemove(ctx context.Context, handler Handler) {
	h.removeHandlers.Add(ctx, handler)
}

func (h *clusterCache) OnChange(ctx context.Context, handler Handler) {
	h.changeHandlers.Add(ctx, handler)
}

func callAll(handlers []interface{}, gvr schema2.GroupVersionResource, key string, obj runtime.Object) (runtime.Object, error) {
	var errs []error
	for _, handler := range handlers {
		f := handler.(Handler)
		if err := f(gvr, key, obj); err != nil {
			errs = append(errs, err)
		}
	}

	return obj, merr.NewErrors(errs...)
}