package kube

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	batchv1 "k8s.io/api/batch/v1"
	coordinationv1 "k8s.io/api/coordination/v1"
	corev1 "k8s.io/api/core/v1"
	k8serrors "k8s.io/apimachinery/pkg/api/errors"
	apiresource "k8s.io/apimachinery/pkg/api/resource"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/kubernetes"
)

// JobSpec is a self-contained description of a sync job, mirroring db.Job.
type JobSpec struct {
	ID             int64
	Name           string
	Pair           string
	Direction      string
	Src            string
	Dest           string
	SrcHost        string
	DestHost       string
	CronSchedule   string
	LockTTLSeconds int
	DryRun         bool
	DeleteMissing  bool
	Workers        int
	MtimeThreshold string
	Excludes       []string
	Enabled        bool
}

// LockStatus describes the current lock state for a job.
type LockStatus struct {
	Locked    bool      `json:"locked"`
	Holder    string    `json:"holder,omitempty"`
	ExpiresAt time.Time `json:"expires_at,omitempty"`
}

// CronJobName returns the K8s CronJob name for a job name.
func CronJobName(jobName string) string {
	name := strings.ToLower(strings.ReplaceAll(jobName, "_", "-"))
	if len(name) > 52 {
		name = name[:52]
	}
	return "ha-sync-" + name
}

// LeaseName returns the Lease name for a job name.
func LeaseName(jobName string) string {
	name := strings.ToLower(strings.ReplaceAll(jobName, "_", "-"))
	if len(name) > 55 {
		name = name[:55]
	}
	return "ha-sync-" + name
}

func pvcName(host, pair string) string {
	return fmt.Sprintf("pvc-%s-%s", strings.ToLower(host), strings.ToLower(pair))
}

func buildArgs(spec JobSpec) []string {
	args := []string{
		"--src=" + spec.Src,
		"--dest=" + spec.Dest,
		"--pair=" + spec.Pair,
		"--direction=" + spec.Direction,
		"--log-dir=/var/log/ha-sync",
		"--src-host=" + spec.SrcHost,
		"--dest-host=" + spec.DestHost,
		fmt.Sprintf("--workers=%d", spec.Workers),
		fmt.Sprintf("--lock-ttl=%d", spec.LockTTLSeconds),
	}
	if spec.MtimeThreshold != "" {
		args = append(args, "--mtime-threshold="+spec.MtimeThreshold)
	}
	if spec.DryRun {
		args = append(args, "--dry-run")
	}
	if spec.DeleteMissing {
		args = append(args, "--delete-missing")
	}
	for _, ex := range spec.Excludes {
		args = append(args, "--exclude="+ex)
	}
	return args
}

func qty(s string) apiresource.Quantity {
	q, _ := apiresource.ParseQuantity(s)
	return q
}

func volumeFromPVC(name, claimName string) corev1.Volume {
	return corev1.Volume{
		Name: name,
		VolumeSource: corev1.VolumeSource{
			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{ClaimName: claimName},
		},
	}
}

func buildCronJob(namespace string, spec JobSpec) *batchv1.CronJob {
	cronName := CronJobName(spec.Name)
	successLimit := int32(3)
	failureLimit := int32(3)
	suspended := !spec.Enabled

	return &batchv1.CronJob{
		TypeMeta: metav1.TypeMeta{APIVersion: "batch/v1", Kind: "CronJob"},
		ObjectMeta: metav1.ObjectMeta{
			Name:      cronName,
			Namespace: namespace,
			Labels: map[string]string{
				"app":          "ha-sync",
				"ha-sync/job":  spec.Name,
				"ha-sync/pair": spec.Pair,
			},
			Annotations: map[string]string{
				"ha-sync/job-id": fmt.Sprintf("%d", spec.ID),
			},
		},
		Spec: batchv1.CronJobSpec{
			Schedule:                   spec.CronSchedule,
			ConcurrencyPolicy:          batchv1.ForbidConcurrent,
			SuccessfulJobsHistoryLimit: &successLimit,
			FailedJobsHistoryLimit:     &failureLimit,
			Suspend:                    &suspended,
			JobTemplate: batchv1.JobTemplateSpec{
				Spec: batchv1.JobSpec{
					Template: corev1.PodTemplateSpec{
						Spec: corev1.PodSpec{
							ServiceAccountName: "ha-sync",
							RestartPolicy:      corev1.RestartPolicyOnFailure,
							Containers: []corev1.Container{{
								Name:            "ha-sync",
								Image:           "ha-sync:latest",
								ImagePullPolicy: corev1.PullNever,
								Command:         []string{"/usr/local/bin/ha-sync"},
								Args:            buildArgs(spec),
								Env: []corev1.EnvVar{
									{
										Name: "HA_SYNC_DB_DSN",
										ValueFrom: &corev1.EnvVarSource{
											SecretKeyRef: &corev1.SecretKeySelector{
												LocalObjectReference: corev1.LocalObjectReference{Name: "ha-sync-db-secret"},
												Key:                  "HA_SYNC_DB_DSN",
											},
										},
									},
									{
										Name: "POD_NAME",
										ValueFrom: &corev1.EnvVarSource{
											FieldRef: &corev1.ObjectFieldSelector{FieldPath: "metadata.name"},
										},
									},
								},
								VolumeMounts: []corev1.VolumeMount{
									{Name: "src-data", MountPath: spec.Src},
									{Name: "dest-data", MountPath: spec.Dest},
									{Name: "logs", MountPath: "/var/log/ha-sync"},
								},
								Resources: corev1.ResourceRequirements{
									Requests: corev1.ResourceList{
										corev1.ResourceCPU:    qty("50m"),
										corev1.ResourceMemory: qty("64Mi"),
									},
									Limits: corev1.ResourceList{
										corev1.ResourceCPU:    qty("500m"),
										corev1.ResourceMemory: qty("256Mi"),
									},
								},
							}},
							Volumes: []corev1.Volume{
								volumeFromPVC("src-data", pvcName(spec.SrcHost, spec.Pair)),
								volumeFromPVC("dest-data", pvcName(spec.DestHost, spec.Pair)),
								volumeFromPVC("logs", "pvc-ha-sync-logs"),
							},
						},
					},
				},
			},
		},
	}
}

// ApplyCronJob creates or server-side-applies the K8s CronJob for a job spec.
func ApplyCronJob(ctx context.Context, client kubernetes.Interface, namespace string, spec JobSpec) error {
	desired := buildCronJob(namespace, spec)
	data, err := json.Marshal(desired)
	if err != nil {
		return fmt.Errorf("kube: marshal cronjob: %w", err)
	}
	_, err = client.BatchV1().CronJobs(namespace).Patch(ctx, desired.Name,
		types.ApplyPatchType, data,
		metav1.PatchOptions{FieldManager: "ha-sync-ctl", Force: boolPtr(true)})
	if err != nil {
		return fmt.Errorf("kube: apply cronjob %s: %w", desired.Name, err)
	}
	return nil
}

// DeleteCronJob removes the K8s CronJob for a job (ignores not-found).
func DeleteCronJob(ctx context.Context, client kubernetes.Interface, namespace, jobName string) error {
	cronName := CronJobName(jobName)
	err := client.BatchV1().CronJobs(namespace).Delete(ctx, cronName, metav1.DeleteOptions{})
	if err != nil && !k8serrors.IsNotFound(err) {
		return fmt.Errorf("kube: delete cronjob %s: %w", cronName, err)
	}
	return nil
}

// TriggerJob creates a one-off Job from the CronJob.
func TriggerJob(ctx context.Context, client kubernetes.Interface, namespace, jobName string) (string, error) {
	cronName := CronJobName(jobName)
	cj, err := client.BatchV1().CronJobs(namespace).Get(ctx, cronName, metav1.GetOptions{})
	if err != nil {
		return "", fmt.Errorf("kube: get cronjob %s: %w", cronName, err)
	}

	ts := time.Now().UTC().Format("150405")
	manualName := fmt.Sprintf("%s-manual-%s", cronName, ts)
	if len(manualName) > 63 {
		manualName = manualName[:63]
	}

	job := &batchv1.Job{
		ObjectMeta: metav1.ObjectMeta{
			Name:      manualName,
			Namespace: namespace,
			Labels:    cj.Labels,
			Annotations: map[string]string{
				"ha-sync/triggered": "manual",
			},
		},
		Spec: cj.Spec.JobTemplate.Spec,
	}
	created, err := client.BatchV1().Jobs(namespace).Create(ctx, job, metav1.CreateOptions{})
	if err != nil {
		return "", fmt.Errorf("kube: create manual job: %w", err)
	}
	return created.Name, nil
}

// GetLockStatus checks the K8s Lease to determine if a job is actively running.
func GetLockStatus(ctx context.Context, client kubernetes.Interface, namespace, jobName string) (LockStatus, error) {
	leaseName := LeaseName(jobName)
	lease, err := client.CoordinationV1().Leases(namespace).Get(ctx, leaseName, metav1.GetOptions{})
	if err != nil {
		if k8serrors.IsNotFound(err) {
			return LockStatus{Locked: false}, nil
		}
		return LockStatus{}, fmt.Errorf("kube: get lease %s: %w", leaseName, err)
	}
	return leaseStatus(lease), nil
}

func leaseStatus(lease *coordinationv1.Lease) LockStatus {
	if lease.Spec.RenewTime == nil || lease.Spec.LeaseDurationSeconds == nil || lease.Spec.HolderIdentity == nil {
		return LockStatus{Locked: false}
	}
	ttl := time.Duration(*lease.Spec.LeaseDurationSeconds) * time.Second
	expiresAt := lease.Spec.RenewTime.Time.Add(ttl)
	if time.Now().After(expiresAt) {
		return LockStatus{Locked: false}
	}
	return LockStatus{
		Locked:    true,
		Holder:    *lease.Spec.HolderIdentity,
		ExpiresAt: expiresAt,
	}
}

// SuspendCronJob sets the suspend flag on a CronJob without changing other config.
func SuspendCronJob(ctx context.Context, client kubernetes.Interface, namespace, jobName string, suspend bool) error {
	cronName := CronJobName(jobName)
	patch := fmt.Sprintf(`{"spec":{"suspend":%v}}`, suspend)
	_, err := client.BatchV1().CronJobs(namespace).Patch(ctx, cronName,
		types.MergePatchType, []byte(patch), metav1.PatchOptions{})
	if err != nil && !k8serrors.IsNotFound(err) {
		return fmt.Errorf("kube: suspend %s=%v: %w", cronName, suspend, err)
	}
	return nil
}

// ListCronJobs returns all CronJobs with the ha-sync app label.
func ListCronJobs(ctx context.Context, client kubernetes.Interface, namespace string) ([]batchv1.CronJob, error) {
	list, err := client.BatchV1().CronJobs(namespace).List(ctx, metav1.ListOptions{
		LabelSelector: "app=ha-sync",
	})
	if err != nil {
		return nil, fmt.Errorf("kube: list cronjobs: %w", err)
	}
	return list.Items, nil
}

// ImportFromCronJob extracts a JobSpec from an existing K8s CronJob.
func ImportFromCronJob(cj batchv1.CronJob) *JobSpec {
	jobName := cj.Labels["ha-sync/job"]
	pair := cj.Labels["ha-sync/pair"]
	if jobName == "" {
		name := strings.TrimPrefix(cj.Name, "ha-sync-")
		if name == cj.Name {
			return nil
		}
		jobName = name
	}

	spec := &JobSpec{
		Name:           jobName,
		Pair:           pair,
		CronSchedule:   cj.Spec.Schedule,
		Enabled:        cj.Spec.Suspend == nil || !*cj.Spec.Suspend,
		LockTTLSeconds: 3600,
		Workers:        4,
		MtimeThreshold: "2s",
		SrcHost:        "dell",
		DestHost:       "hp",
	}

	containers := cj.Spec.JobTemplate.Spec.Template.Spec.Containers
	if len(containers) == 0 {
		return spec
	}
	for _, arg := range containers[0].Args {
		switch {
		case strings.HasPrefix(arg, "--src="):
			spec.Src = strings.TrimPrefix(arg, "--src=")
		case strings.HasPrefix(arg, "--dest="):
			spec.Dest = strings.TrimPrefix(arg, "--dest=")
		case strings.HasPrefix(arg, "--pair="):
			spec.Pair = strings.TrimPrefix(arg, "--pair=")
		case strings.HasPrefix(arg, "--direction="):
			spec.Direction = strings.TrimPrefix(arg, "--direction=")
		case strings.HasPrefix(arg, "--src-host="):
			spec.SrcHost = strings.TrimPrefix(arg, "--src-host=")
		case strings.HasPrefix(arg, "--dest-host="):
			spec.DestHost = strings.TrimPrefix(arg, "--dest-host=")
		case arg == "--dry-run":
			spec.DryRun = true
		case arg == "--delete-missing":
			spec.DeleteMissing = true
		case strings.HasPrefix(arg, "--exclude="):
			spec.Excludes = append(spec.Excludes, strings.TrimPrefix(arg, "--exclude="))
		}
	}
	return spec
}

func boolPtr(b bool) *bool { return &b }