package k8s

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"sort"
	"strings"
	"time"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"

	"github.com/ocdp/cluster-service/internal/domain/entity"
	"github.com/ocdp/cluster-service/internal/domain/repository"
)

type DiagnosticsClient struct{}

func NewDiagnosticsClient() repository.InstanceDiagnosticsClient {
	return &DiagnosticsClient{}
}

type MockDiagnosticsClient struct{}

func NewMockDiagnosticsClient() repository.InstanceDiagnosticsClient {
	return &MockDiagnosticsClient{}
}

func (*MockDiagnosticsClient) GetDiagnostics(ctx context.Context, cluster *entity.Cluster, instance *entity.Instance, tailLines int64) (*entity.InstanceDiagnostics, error) {
	return &entity.InstanceDiagnostics{
		InstanceName: instance.Name,
		Namespace:    instance.Namespace,
		CollectedAt:  time.Now(),
	}, nil
}

func (*MockDiagnosticsClient) StreamPodLogs(ctx context.Context, cluster *entity.Cluster, namespace, podName, containerName string, tailLines int64) (<-chan string, <-chan error, error) {
	lines := make(chan string, 10)
	errs := make(chan error, 1)
	go func() {
		defer close(lines)
		defer close(errs)
		select {
		case <-ctx.Done():
			return
		case lines <- "[mock] Streaming pod logs...":
		case lines <- "[mock] Container started successfully":
		case lines <- "[mock] Listening on :8080":
		}
	}()
	return lines, errs, nil
}

func (c *DiagnosticsClient) GetDiagnostics(ctx context.Context, cluster *entity.Cluster, instance *entity.Instance, tailLines int64) (*entity.InstanceDiagnostics, error) {
	clientset, err := diagnosticsClientset(cluster)
	if err != nil {
		return nil, err
	}
	if tailLines <= 0 {
		tailLines = 200
	}
	if tailLines > 2000 {
		tailLines = 2000
	}

	pods, err := listInstancePods(ctx, clientset, instance)
	if err != nil {
		return nil, err
	}
	services, err := listInstanceServices(ctx, clientset, instance)
	if err != nil {
		return nil, err
	}
	events, err := listInstanceEvents(ctx, clientset, instance, pods, services)
	if err != nil {
		return nil, err
	}
	logs := collectPodLogs(ctx, clientset, pods, tailLines)

	return &entity.InstanceDiagnostics{
		InstanceName: instance.Name,
		Namespace:    instance.Namespace,
		Pods:         convertPodsToDiagnostics(pods),
		Services:     convertServicesToDiagnostics(services),
		Events:       convertEventsToDiagnostics(events),
		Logs:         logs,
		CollectedAt:  time.Now(),
	}, nil
}

func (c *DiagnosticsClient) StreamPodLogs(ctx context.Context, cluster *entity.Cluster, namespace, podName, containerName string, tailLines int64) (<-chan string, <-chan error, error) {
	clientset, err := diagnosticsClientset(cluster)
	if err != nil {
		return nil, nil, err
	}
	if tailLines <= 0 {
		tailLines = 200
	}
	if tailLines > 2000 {
		tailLines = 2000
	}

	req := clientset.CoreV1().Pods(namespace).GetLogs(podName, &corev1.PodLogOptions{
		Container: containerName,
		Follow:    true,
		TailLines: &tailLines,
	})

	stream, err := req.Stream(ctx)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to open log stream for %s/%s: %w", podName, containerName, err)
	}

	lines := make(chan string, 64)
	errs := make(chan error, 1)

	go func() {
		defer close(lines)
		defer close(errs)
		defer func() { _ = stream.Close() }()

		scanner := bufio.NewScanner(stream)
		// Allow long lines; Kubernetes log entries can exceed the default 64 KiB
		scanner.Buffer(make([]byte, 0, 64*1024), 2*1024*1024)

		for scanner.Scan() {
			select {
			case <-ctx.Done():
				return
			default:
			}
			line := scanner.Text()
			if line == "" {
				continue
			}
			select {
			case lines <- line:
			case <-ctx.Done():
				return
			}
		}
		if err := scanner.Err(); err != nil {
			select {
			case errs <- err:
			case <-ctx.Done():
			}
		}
	}()

	return lines, errs, nil
}

func diagnosticsClientset(cluster *entity.Cluster) (kubernetes.Interface, error) {
	config, err := restConfigFromCluster(cluster)
	if err != nil {
		return nil, err
	}
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		return nil, fmt.Errorf("failed to create diagnostics kubernetes client: %w", err)
	}
	return clientset, nil
}

func listInstancePods(ctx context.Context, clientset kubernetes.Interface, instance *entity.Instance) ([]corev1.Pod, error) {
	selector := fmt.Sprintf("app.kubernetes.io/instance=%s", instance.Name)
	pods, err := clientset.CoreV1().Pods(instance.Namespace).List(ctx, metav1.ListOptions{LabelSelector: selector})
	if err != nil {
		return nil, fmt.Errorf("failed to list instance pods: %w", err)
	}
	if len(pods.Items) > 0 {
		return pods.Items, nil
	}
	all, err := clientset.CoreV1().Pods(instance.Namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return nil, fmt.Errorf("failed to list namespace pods: %w", err)
	}
	filtered := make([]corev1.Pod, 0)
	for _, pod := range all.Items {
		if resourceMatchesInstance(pod.ObjectMeta, instance) {
			filtered = append(filtered, pod)
		}
	}
	return filtered, nil
}

func listInstanceServices(ctx context.Context, clientset kubernetes.Interface, instance *entity.Instance) ([]corev1.Service, error) {
	selector := fmt.Sprintf("app.kubernetes.io/instance=%s", instance.Name)
	services, err := clientset.CoreV1().Services(instance.Namespace).List(ctx, metav1.ListOptions{LabelSelector: selector})
	if err != nil {
		return nil, fmt.Errorf("failed to list instance services: %w", err)
	}
	if len(services.Items) > 0 {
		return services.Items, nil
	}
	all, err := clientset.CoreV1().Services(instance.Namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return nil, fmt.Errorf("failed to list namespace services: %w", err)
	}
	filtered := make([]corev1.Service, 0)
	for _, svc := range all.Items {
		if resourceMatchesInstance(svc.ObjectMeta, instance) {
			filtered = append(filtered, svc)
		}
	}
	return filtered, nil
}

func listInstanceEvents(ctx context.Context, clientset kubernetes.Interface, instance *entity.Instance, pods []corev1.Pod, services []corev1.Service) ([]corev1.Event, error) {
	events, err := clientset.CoreV1().Events(instance.Namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return nil, fmt.Errorf("failed to list instance events: %w", err)
	}
	names := map[string]bool{instance.Name: true}
	for _, pod := range pods {
		names[pod.Name] = true
	}
	for _, svc := range services {
		names[svc.Name] = true
	}
	filtered := make([]corev1.Event, 0)
	for _, event := range events.Items {
		if names[event.InvolvedObject.Name] || strings.Contains(event.Message, instance.Name) {
			filtered = append(filtered, event)
		}
	}
	sort.SliceStable(filtered, func(i, j int) bool {
		return filtered[i].LastTimestamp.Time.After(filtered[j].LastTimestamp.Time)
	})
	if len(filtered) > 100 {
		filtered = filtered[:100]
	}
	return filtered, nil
}

func collectPodLogs(ctx context.Context, clientset kubernetes.Interface, pods []corev1.Pod, tailLines int64) []entity.InstancePodLog {
	logs := make([]entity.InstancePodLog, 0)
	for _, pod := range pods {
		for _, container := range pod.Spec.Containers {
			item := entity.InstancePodLog{Pod: pod.Name, Container: container.Name, TailLines: tailLines}
			req := clientset.CoreV1().Pods(pod.Namespace).GetLogs(pod.Name, &corev1.PodLogOptions{
				Container: container.Name,
				TailLines: &tailLines,
			})
			stream, err := req.Stream(ctx)
			if err != nil {
				item.Error = err.Error()
				logs = append(logs, item)
				continue
			}
			data, err := io.ReadAll(io.LimitReader(stream, 1<<20))
			_ = stream.Close()
			if err != nil {
				item.Error = err.Error()
			} else {
				item.Log = string(data)
			}
			logs = append(logs, item)
		}
	}
	return logs
}

func convertPodsToDiagnostics(pods []corev1.Pod) []entity.InstancePodDiagnostics {
	out := make([]entity.InstancePodDiagnostics, 0, len(pods))
	for _, pod := range pods {
		containers := make([]entity.InstanceContainerDiagnostics, 0, len(pod.Status.ContainerStatuses))
		var restarts int32
		for _, status := range pod.Status.ContainerStatuses {
			restarts += status.RestartCount
			containers = append(containers, entity.InstanceContainerDiagnostics{
				Name:         status.Name,
				Image:        status.Image,
				Ready:        status.Ready,
				RestartCount: status.RestartCount,
				State:        containerStateName(status.State),
				Reason:       containerStateReason(status.State),
				Message:      containerStateMessage(status.State),
			})
		}
		conditions := make([]entity.InstanceConditionDiagnostics, 0, len(pod.Status.Conditions))
		for _, condition := range pod.Status.Conditions {
			conditions = append(conditions, entity.InstanceConditionDiagnostics{
				Type:    string(condition.Type),
				Status:  string(condition.Status),
				Reason:  condition.Reason,
				Message: condition.Message,
			})
		}
		out = append(out, entity.InstancePodDiagnostics{
			Name:              pod.Name,
			Namespace:         pod.Namespace,
			Phase:             string(pod.Status.Phase),
			NodeName:          pod.Spec.NodeName,
			PodIP:             pod.Status.PodIP,
			HostIP:            pod.Status.HostIP,
			RestartCount:      restarts,
			Containers:        containers,
			Conditions:        conditions,
			CreationTimestamp: pod.CreationTimestamp.Time,
		})
	}
	return out
}

func convertServicesToDiagnostics(services []corev1.Service) []entity.InstanceServiceDiagnostics {
	out := make([]entity.InstanceServiceDiagnostics, 0, len(services))
	for _, svc := range services {
		entry := convertServiceToEntry(&svc)
		out = append(out, entity.InstanceServiceDiagnostics{
			Name:      svc.Name,
			Namespace: svc.Namespace,
			Type:      string(svc.Spec.Type),
			ClusterIP: svc.Spec.ClusterIP,
			Ports:     entry.Ports,
		})
	}
	return out
}

func convertEventsToDiagnostics(events []corev1.Event) []entity.InstanceEventDiagnostics {
	out := make([]entity.InstanceEventDiagnostics, 0, len(events))
	for _, event := range events {
		out = append(out, entity.InstanceEventDiagnostics{
			Type:           event.Type,
			Reason:         event.Reason,
			Message:        event.Message,
			InvolvedKind:   event.InvolvedObject.Kind,
			InvolvedName:   event.InvolvedObject.Name,
			Count:          event.Count,
			FirstTimestamp: event.FirstTimestamp.Time,
			LastTimestamp:  event.LastTimestamp.Time,
		})
	}
	return out
}

func containerStateName(state corev1.ContainerState) string {
	switch {
	case state.Running != nil:
		return "running"
	case state.Waiting != nil:
		return "waiting"
	case state.Terminated != nil:
		return "terminated"
	default:
		return "unknown"
	}
}

func containerStateReason(state corev1.ContainerState) string {
	switch {
	case state.Waiting != nil:
		return state.Waiting.Reason
	case state.Terminated != nil:
		return state.Terminated.Reason
	default:
		return ""
	}
}

func containerStateMessage(state corev1.ContainerState) string {
	switch {
	case state.Waiting != nil:
		return state.Waiting.Message
	case state.Terminated != nil:
		return state.Terminated.Message
	default:
		return ""
	}
}