package server

import (
	"context"

	batchv1 "k8s.io/api/batch/v1"
	corev1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"

	"git.unkin.net/unkin/repospawner/internal/jobs"
)

// Cluster is the slice of the Kubernetes API the server needs. Keeping it an
// interface lets the reconciler and handlers be tested without a cluster.
type Cluster interface {
	// CreateJob creates a Job, reporting AlreadyExists as nil so a repeated
	// reconcile is harmless.
	CreateJob(ctx context.Context, job *batchv1.Job) error
	// ListJobs returns every repospawner-owned Job in the namespace.
	ListJobs(ctx context.Context) ([]batchv1.Job, error)
	// ListPods returns every repospawner-owned Job pod in the namespace.
	ListPods(ctx context.Context) ([]corev1.Pod, error)
	// Ping reports whether the API server is reachable.
	Ping(ctx context.Context) error
}

// KubeCluster is the in-cluster Cluster implementation.
type KubeCluster struct {
	client    kubernetes.Interface
	namespace string
}

// NewKubeCluster builds a Cluster from the pod's in-cluster credentials.
func NewKubeCluster(namespace string) (*KubeCluster, error) {
	cfg, err := rest.InClusterConfig()
	if err != nil {
		return nil, err
	}
	client, err := kubernetes.NewForConfig(cfg)
	if err != nil {
		return nil, err
	}
	return &KubeCluster{client: client, namespace: namespace}, nil
}

// ownedSelector matches everything repospawner creates.
const ownedSelector = jobs.LabelApp + "=" + jobs.AppName + "," + jobs.LabelRequest

func (k *KubeCluster) CreateJob(ctx context.Context, job *batchv1.Job) error {
	_, err := k.client.BatchV1().Jobs(k.namespace).Create(ctx, job, metav1.CreateOptions{})
	if apierrors.IsAlreadyExists(err) {
		return nil
	}
	return err
}

func (k *KubeCluster) ListJobs(ctx context.Context) ([]batchv1.Job, error) {
	list, err := k.client.BatchV1().Jobs(k.namespace).List(ctx, metav1.ListOptions{LabelSelector: ownedSelector})
	if err != nil {
		return nil, err
	}
	return list.Items, nil
}

func (k *KubeCluster) ListPods(ctx context.Context) ([]corev1.Pod, error) {
	list, err := k.client.CoreV1().Pods(k.namespace).List(ctx, metav1.ListOptions{LabelSelector: ownedSelector})
	if err != nil {
		return nil, err
	}
	return list.Items, nil
}

func (k *KubeCluster) Ping(ctx context.Context) error {
	limit := int64(1)
	_, err := k.client.BatchV1().Jobs(k.namespace).List(ctx, metav1.ListOptions{Limit: limit})
	return err
}