package dao

import (
	"fmt"
	"sort"

	"github.com/derailed/k9s/internal/watch"
	"github.com/rs/zerolog/log"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
)

// MetaViewers represents a collection of meta viewers.
type ResourceMetas map[GVR]metav1.APIResource

var resMetas ResourceMetas

func AccessorFor(f Factory, gvr GVR) (Accessor, error) {
	m := map[GVR]Accessor{
		"contexts":                      &Context{},
		"screendumps":                   &ScreenDump{},
		"apps/v1/deployments":           &Deployment{},
		"apps/v1/daemonsets":            &DaemonSet{},
		"extensions/v1beta1/daemonsets": &DaemonSet{},
		"apps/v1/statefulsets":          &StatefulSet{},
	}

	r, ok := m[gvr]
	if !ok {
		r = &Resource{}
		log.Warn().Msgf("No DAO registry entry for %q. Going generic!", gvr)
	}
	r.Init(f, gvr)

	return r, nil
}

func AllGVRs() []GVR {
	kk := make(GVRs, 0, len(resMetas))
	for k := range resMetas {
		kk = append(kk, k)
	}
	sort.Sort(kk)

	return kk
}

// MetaFor returns a resource metadata for a given gvr.
func MetaFor(gvr GVR) (metav1.APIResource, error) {
	m, ok := resMetas[gvr]
	if !ok {
		return metav1.APIResource{}, fmt.Errorf("no resource meta defined for %q", gvr)
	}
	return m, nil
}

// Load hydrates server preferred+CRDs resource metadata.
func Load(f *watch.Factory) error {
	resMetas = make(ResourceMetas, 100)
	if err := loadPreferred(f, resMetas); err != nil {
		return err
	}
	if err := loadNonResource(resMetas); err != nil {
		return err
	}

	return loadCRDs(f, resMetas)
}

func loadNonResource(m ResourceMetas) error {
	m["contexts"] = metav1.APIResource{
		Name:         "contexts",
		SingularName: "context",
		Namespaced:   false,
		Kind:         "Context",
		ShortNames:   []string{"ctx"},
		Verbs:        []string{},
		Categories:   []string{"K9s"},
	}
	m["screendumps"] = metav1.APIResource{
		Name:         "screendumps",
		SingularName: "screendump",
		Namespaced:   false,
		Kind:         "ScreenDump",
		ShortNames:   []string{"sd"},
		Verbs:        []string{"delete"},
		Categories:   []string{"K9s"},
	}

	return nil
}

func loadPreferred(f *watch.Factory, m ResourceMetas) error {
	discovery, err := f.Client().CachedDiscovery()
	if err != nil {
		return err
	}
	rr, err := discovery.ServerPreferredResources()
	if err != nil {
		return err
	}
	for _, r := range rr {
		for _, res := range r.APIResources {
			gvr := FromGVAndR(r.GroupVersion, res.Name)
			res.Group, res.Version = gvr.ToG(), gvr.ToV()
			m[gvr] = res
		}
	}

	return nil
}

func loadCRDs(f *watch.Factory, m ResourceMetas) error {
	oo, err := f.List("", "apiextensions.k8s.io/v1beta1/customresourcedefinitions", labels.Everything())
	if err != nil {
		return err
	}
	f.WaitForCacheSync()

	for _, o := range oo {
		meta, errs := extractMeta(o)
		if len(errs) > 0 {
			log.Error().Err(errs[0]).Msgf("Fail to extract CRD meta (%d) errors", len(errs))
			continue
		}
		gvr := NewGVR(meta.Group, meta.Version, meta.Name)
		m[gvr] = meta
	}

	return nil
}

func extractMeta(o runtime.Object) (metav1.APIResource, []error) {
	var (
		m    metav1.APIResource
		errs []error
	)

	crd, ok := o.(*unstructured.Unstructured)
	if !ok {
		return m, append(errs, fmt.Errorf("Expected CustomResourceDefinition, but got %T", o))
	}

	var spec map[string]interface{}
	spec, errs = extractMap(crd.Object, "spec", errs)

	var meta map[string]interface{}
	meta, errs = extractMap(crd.Object, "metadata", errs)

	m.Name, errs = extractStr(meta, "name", errs)
	m.Group, errs = extractStr(spec, "group", errs)
	m.Version, errs = extractStr(spec, "version", errs)

	var scope string
	scope, errs = extractStr(spec, "scope", errs)

	m.Namespaced = isNamespaced(scope)

	var names map[string]interface{}
	names, errs = extractMap(spec, "names", errs)
	m.Kind, errs = extractStr(names, "kind", errs)
	m.SingularName, errs = extractStr(names, "singular", errs)
	m.Name, errs = extractStr(names, "plural", errs)
	m.ShortNames, errs = extractSlice(names, "shortNames", errs)

	return m, errs
}

func isNamespaced(scope string) bool {
	return scope == "Namespaced"
}

func extractSlice(m map[string]interface{}, n string, errs []error) ([]string, []error) {
	if m[n] == nil {
		return nil, errs
	}
	s, ok := m[n].([]string)
	if ok {
		return s, errs
	}

	ii, ok := m[n].([]interface{})
	if !ok {
		return s, append(errs, fmt.Errorf("failed to extract slice %s -- %#v", n, m))
	}

	ss := make([]string, len(ii))
	for i, name := range ii {
		ss[i], ok = name.(string)
		if !ok {
			return s, append(errs, fmt.Errorf("expecting string shortnames"))
		}
	}
	return s, errs
}

func extractStr(m map[string]interface{}, n string, errs []error) (string, []error) {
	s, ok := m[n].(string)
	if !ok {
		return s, append(errs, fmt.Errorf("failed to extract string %s", n))
	}
	return s, errs
}

func extractMap(m map[string]interface{}, n string, errs []error) (map[string]interface{}, []error) {
	v, ok := m[n].(map[string]interface{})
	if !ok {
		return v, append(errs, fmt.Errorf("failed to extract field %s", n))
	}
	return v, errs
}