package controller

import (
	"context"
	"fmt"
	"sort"
	"time"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"

	bindv1alpha1 "git.unkin.net/unkin/bind-operator/api/v1alpha1"
	"git.unkin.net/unkin/bind-operator/internal/bind"
)

const (
	requeueShort = 15 * time.Second
	requeueLong  = 2 * time.Minute

	managedByLabel = "app.kubernetes.io/managed-by"
	managedByValue = "bind-operator"
	clusterLabel   = "bind.unkin.net/cluster"

	finalizer = "bind.unkin.net/finalizer"

	// defaultBindImage is used when BindCluster.spec.image is empty.
	defaultBindImage = "internetsystemsconsortium/bind9:9.20"
)

func headlessServiceName(cluster string) string { return cluster + "-headless" }
func primaryServiceName(cluster string) string  { return cluster + "-primary" }

// primaryPodSelector selects only the primary pod (ordinal 0) via the stable
// StatefulSet pod-name label, for the write Service.
func primaryPodSelector(cluster string) map[string]string {
	s := commonLabels(cluster)
	s["statefulset.kubernetes.io/pod-name"] = primaryPodName(cluster)
	return s
}
func clientServiceName(cluster string) string { return cluster }
func primaryPodName(cluster string) string    { return cluster + "-0" }
func configMapName(cluster string) string     { return cluster + "-config" }
func keysSecretName(cluster string) string    { return cluster + "-keys" }
func rndcSecretName(cluster string) string    { return cluster + "-rndc" }

// primaryAddress is the in-cluster DNS name of the primary pod (ordinal 0).
func primaryAddress(cluster, namespace string) string {
	return fmt.Sprintf("%s-0.%s.%s.svc.cluster.local", cluster, headlessServiceName(cluster), namespace)
}

// setReady sets the standard Ready condition on a status conditions slice.
func setReady(conds *[]metav1.Condition, gen int64, ok bool, reason, msg string) {
	status := metav1.ConditionFalse
	if ok {
		status = metav1.ConditionTrue
	}
	meta.SetStatusCondition(conds, metav1.Condition{
		Type:               "Ready",
		Status:             status,
		Reason:             reason,
		Message:            msg,
		ObservedGeneration: gen,
	})
}

// commonLabels are applied to every object the operator creates for a cluster.
func commonLabels(cluster string) map[string]string {
	return map[string]string{
		managedByLabel: managedByValue,
		clusterLabel:   cluster,
	}
}

// getCluster fetches the BindCluster referenced by clusterRef in namespace.
func getCluster(ctx context.Context, c client.Client, namespace, clusterRef string) (*bindv1alpha1.BindCluster, error) {
	var cluster bindv1alpha1.BindCluster
	if err := c.Get(ctx, client.ObjectKey{Namespace: namespace, Name: clusterRef}, &cluster); err != nil {
		return nil, err
	}
	return &cluster, nil
}

// primaryReady reports whether the primary pod of a cluster is Ready.
func primaryReady(ctx context.Context, c client.Client, cluster *bindv1alpha1.BindCluster) bool {
	var pod corev1.Pod
	key := client.ObjectKey{Namespace: cluster.Namespace, Name: primaryPodName(cluster.Name)}
	if err := c.Get(ctx, key, &pod); err != nil {
		return false
	}
	for _, cond := range pod.Status.Conditions {
		if cond.Type == corev1.PodReady {
			return cond.Status == corev1.ConditionTrue
		}
	}
	return false
}

// primaryPodIP returns the pod IP of a cluster's primary pod (ordinal 0), or an
// empty string if the pod has no IP yet. BIND's primaries/default-primaries
// only accept IP addresses (not hostnames), and zone seeding needs the address
// for glue, so the operator resolves the pod IP rather than using a DNS name.
func primaryPodIP(ctx context.Context, c client.Client, cluster *bindv1alpha1.BindCluster) string {
	var pod corev1.Pod
	if err := c.Get(ctx, client.ObjectKey{Namespace: cluster.Namespace, Name: primaryPodName(cluster.Name)}, &pod); err != nil {
		return ""
	}
	return pod.Status.PodIP
}

// primaryTransferAddress returns the address secondaries use to reach the
// primary for catalog and zone AXFR. It prefers the primary Service ClusterIP,
// which is stable across primary pod restarts (the pod IP is not: it changes on
// every restart, leaving secondaries pointed at a dead address). It falls back
// to the primary pod IP when no primary Service is configured or its ClusterIP
// is not yet assigned.
func primaryTransferAddress(ctx context.Context, c client.Client, cluster *bindv1alpha1.BindCluster) string {
	if cluster.Spec.PrimaryService != nil {
		var svc corev1.Service
		if err := c.Get(ctx, client.ObjectKey{Namespace: cluster.Namespace, Name: primaryServiceName(cluster.Name)}, &svc); err == nil {
			if ip := svc.Spec.ClusterIP; ip != "" && ip != corev1.ClusterIPNone {
				return ip
			}
		}
	}
	return primaryPodIP(ctx, c, cluster)
}

// secondaryPodIPs returns the pod IPs of a cluster's secondary pods (every pod
// except the ordinal-0 primary) that currently have an address. The primary
// uses this list as its zone `also-notify` set, so a change to a primary zone
// (in particular a dynamic update) triggers an immediate NOTIFY -> IXFR to the
// secondaries instead of leaving them stale until the next SOA refresh. The
// list is sorted so the rendered zone config is stable and does not churn
// modzone on every reconcile. Pod IPs change across restarts, so the caller
// relies on the zone controller's periodic requeue to refresh the set (a
// restarted secondary re-transfers the whole zone on load regardless). Returns
// nil for a single-replica cluster.
func secondaryPodIPs(ctx context.Context, c client.Client, cluster *bindv1alpha1.BindCluster) []string {
	var pods corev1.PodList
	if err := c.List(ctx, &pods, client.InNamespace(cluster.Namespace), client.MatchingLabels(commonLabels(cluster.Name))); err != nil {
		return nil
	}
	primary := primaryPodName(cluster.Name)
	var ips []string
	for i := range pods.Items {
		p := &pods.Items[i]
		if p.Name == primary || p.Status.PodIP == "" {
			continue
		}
		ips = append(ips, p.Status.PodIP)
	}
	sort.Strings(ips)
	return ips
}

// resolveTSIG reads the material of a BindTSIGKey into TSIG credentials.
func resolveTSIG(ctx context.Context, c client.Client, namespace, keyRef string) (bind.TSIGCreds, error) {
	var creds bind.TSIGCreds
	if keyRef == "" {
		return creds, fmt.Errorf("no TSIG key referenced")
	}
	var key bindv1alpha1.BindTSIGKey
	if err := c.Get(ctx, client.ObjectKey{Namespace: namespace, Name: keyRef}, &key); err != nil {
		return creds, fmt.Errorf("get tsig key %s: %w", keyRef, err)
	}
	secretName := key.Status.SecretName
	if secretName == "" {
		secretName = key.Spec.SecretName
	}
	if secretName == "" {
		secretName = keyRef + "-tsig"
	}
	var secret corev1.Secret
	if err := c.Get(ctx, client.ObjectKey{Namespace: namespace, Name: secretName}, &secret); err != nil {
		return creds, fmt.Errorf("get tsig secret %s: %w", secretName, err)
	}
	keyName := key.Spec.KeyName
	if keyName == "" {
		keyName = keyRef
	}
	creds = bind.TSIGCreds{
		Name:      keyName,
		Algorithm: string(secret.Data["algorithm"]),
		Secret:    string(secret.Data["secret"]),
	}
	if creds.Algorithm == "" {
		creds.Algorithm = string(bindv1alpha1.TSIGHMACSHA256)
	}
	return creds, nil
}