package kubernetes

import (
	"context"
	"fmt"
	"log/slog"
	"os/exec"
	"strings"
	"sync"
	"time"

	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/port"

	corev1 "k8s.io/api/core/v1"
	k8serrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/watch"
	"k8s.io/client-go/kubernetes"
)

// ProjectRepository implements port.ProjectRepository using Kubernetes.
type ProjectRepository struct {
	namespace string
	client    *kubernetes.Clientset
	logger    *slog.Logger

	projects map[domain.ProjectID]*domain.Project
	mu       sync.RWMutex

	// Watch management
	watchCancel context.CancelFunc
	watchWg     sync.WaitGroup
}

// NewProjectRepository creates a new Kubernetes project repository.
// If client is nil, falls back to hardcoded projects (for local development).
func NewProjectRepository(namespace string) *ProjectRepository {
	return NewProjectRepositoryWithClient(namespace, nil, nil)
}

// NewProjectRepositoryWithClient creates a new Kubernetes project repository
// with an optional K8s client for dynamic project discovery.
func NewProjectRepositoryWithClient(namespace string, client *kubernetes.Clientset, logger *slog.Logger) *ProjectRepository {
	if logger == nil {
		logger = slog.Default()
	}

	r := &ProjectRepository{
		namespace: namespace,
		client:    client,
		logger:    logger,
		projects:  make(map[domain.ProjectID]*domain.Project),
	}

	// Initialize with fallback hardcoded projects
	// These will be replaced by discovered projects if K8s client is available
	r.initFallbackProjects()

	return r
}

// initFallbackProjects adds hardcoded projects for when K8s client is unavailable.
// Currently empty - projects are discovered dynamically from K8s or stored in the database.
func (r *ProjectRepository) initFallbackProjects() {
	// No hardcoded fallback projects
}

// Ensure ProjectRepository implements port.ProjectRepository at compile time.
var _ port.ProjectRepository = (*ProjectRepository)(nil)

// List returns all available projects.
func (r *ProjectRepository) List(ctx context.Context) ([]domain.Project, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	projects := make([]domain.Project, 0, len(r.projects))
	for _, p := range r.projects {
		projects = append(projects, *p)
	}
	return projects, nil
}

// Get returns a project by ID.
func (r *ProjectRepository) Get(ctx context.Context, id domain.ProjectID) (*domain.Project, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	p, ok := r.projects[id]
	if !ok {
		return nil, domain.ErrProjectNotFound
	}
	return p, nil
}

// Exists checks if a project exists.
func (r *ProjectRepository) Exists(ctx context.Context, id domain.ProjectID) (bool, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	_, ok := r.projects[id]
	return ok, nil
}

// Register adds a new project to the repository.
func (r *ProjectRepository) Register(ctx context.Context, project *domain.Project) error {
	r.mu.Lock()
	defer r.mu.Unlock()

	r.projects[project.ID] = project
	return nil
}

// Unregister removes a project from the repository.
func (r *ProjectRepository) Unregister(ctx context.Context, id domain.ProjectID) error {
	r.mu.Lock()
	defer r.mu.Unlock()

	delete(r.projects, id)
	return nil
}

// RefreshStatus updates the status of all projects from K8s.
// If K8s client is available, it also discovers new projects.
func (r *ProjectRepository) RefreshStatus(ctx context.Context) error {
	// Try to discover projects from K8s labels first
	if r.client != nil {
		if err := r.discoverProjects(ctx); err != nil {
			r.logger.Warn("failed to discover projects from K8s, using fallback", "error", err)
		}
	}

	r.mu.Lock()
	defer r.mu.Unlock()

	for _, p := range r.projects {
		status, err := r.getPodStatus(ctx, p.PodName)
		if err != nil {
			p.Status = domain.ProjectStatusError
			continue
		}
		p.Status = status
	}
	return nil
}

// discoverProjects finds projects from pods with rdev labels.
func (r *ProjectRepository) discoverProjects(ctx context.Context) error {
	if r.client == nil {
		return fmt.Errorf("k8s client not available")
	}

	// List pods with the rdev project label
	labelSelector := fmt.Sprintf("%s=true", domain.LabelProject)

	pods, err := r.client.CoreV1().Pods(r.namespace).List(ctx, metav1.ListOptions{
		LabelSelector: labelSelector,
	})
	if err != nil {
		return fmt.Errorf("list pods: %w", err)
	}

	r.mu.Lock()
	defer r.mu.Unlock()

	// Track which projects we've seen to detect deletions
	seen := make(map[domain.ProjectID]bool)

	for _, pod := range pods.Items {
		project := r.podToProject(&pod)
		if project != nil {
			seen[project.ID] = true
			r.projects[project.ID] = project
			r.logger.Debug("discovered project from pod",
				"project_id", project.ID,
				"pod_name", project.PodName,
				"status", project.Status)
		}
	}

	// Remove projects whose pods no longer exist (but keep fallback projects if no K8s client)
	for id := range r.projects {
		if !seen[id] {
			// Only remove if we have at least one discovered project
			// This prevents removing all fallback projects when K8s is unavailable
			if len(seen) > 0 {
				r.logger.Info("removing project (pod deleted)", "project_id", id)
				delete(r.projects, id)
			}
		}
	}

	return nil
}

// podToProject converts a K8s pod to a domain.Project.
// Returns nil if the pod doesn't have the required labels.
func (r *ProjectRepository) podToProject(pod *corev1.Pod) *domain.Project {
	labels := pod.Labels
	annotations := pod.Annotations

	// Check for required labels
	if labels[domain.LabelProject] != "true" {
		return nil
	}

	name := labels[domain.LabelName]
	if name == "" {
		// Fallback to pod name if name label is missing
		name = pod.Name
	}

	workspace := labels[domain.LabelWorkspace]
	if workspace == "" {
		workspace = "/workspace" // Default workspace
	}

	description := ""
	if annotations != nil {
		description = annotations[domain.AnnotDescription]
	}

	// Convert pod phase to project status
	status := r.phaseToStatus(pod.Status.Phase)

	return &domain.Project{
		ID:          domain.ProjectID(name),
		Name:        capitalizeFirst(name),
		Description: description,
		PodName:     pod.Name,
		Status:      status,
		Workspace:   workspace,
	}
}

// phaseToStatus converts K8s pod phase to domain.ProjectStatus.
func (r *ProjectRepository) phaseToStatus(phase corev1.PodPhase) domain.ProjectStatus {
	switch phase {
	case corev1.PodRunning:
		return domain.ProjectStatusRunning
	case corev1.PodPending:
		return domain.ProjectStatusPending
	case corev1.PodFailed:
		return domain.ProjectStatusFailed
	case corev1.PodSucceeded:
		// Succeeded is a terminal state, treat as not available
		return domain.ProjectStatusNotFound
	default:
		return domain.ProjectStatusUnknown
	}
}

// StartWatching begins watching for pod changes in the background.
// Call StopWatching to stop the watch.
func (r *ProjectRepository) StartWatching(ctx context.Context) error {
	if r.client == nil {
		return fmt.Errorf("k8s client not available for watching")
	}

	// Create a cancellable context for the watch
	watchCtx, cancel := context.WithCancel(ctx)
	r.watchCancel = cancel

	r.watchWg.Add(1)
	go r.watchLoop(watchCtx)

	r.logger.Info("started watching for project pod changes", "namespace", r.namespace)
	return nil
}

// StopWatching stops the background pod watch.
func (r *ProjectRepository) StopWatching() {
	if r.watchCancel != nil {
		r.watchCancel()
		r.watchWg.Wait()
		r.watchCancel = nil
		r.logger.Info("stopped watching for project pod changes")
	}
}

// watchLoop continuously watches for pod changes.
func (r *ProjectRepository) watchLoop(ctx context.Context) {
	defer r.watchWg.Done()

	labelSelector := fmt.Sprintf("%s=true", domain.LabelProject)
	backoff := time.Second

	for {
		select {
		case <-ctx.Done():
			return
		default:
		}

		watcher, err := r.client.CoreV1().Pods(r.namespace).Watch(ctx, metav1.ListOptions{
			LabelSelector: labelSelector,
		})
		if err != nil {
			r.logger.Error("failed to create pod watch", "error", err)
			time.Sleep(backoff)
			backoff = min(backoff*2, time.Minute)
			continue
		}

		backoff = time.Second // Reset backoff on successful connection

		r.handleWatchEvents(ctx, watcher)
		watcher.Stop()
	}
}

// handleWatchEvents processes events from the pod watcher.
func (r *ProjectRepository) handleWatchEvents(ctx context.Context, watcher watch.Interface) {
	for {
		select {
		case <-ctx.Done():
			return
		case event, ok := <-watcher.ResultChan():
			if !ok {
				// Watch channel closed, need to reconnect
				r.logger.Debug("watch channel closed, reconnecting")
				return
			}

			pod, ok := event.Object.(*corev1.Pod)
			if !ok {
				continue
			}

			switch event.Type {
			case watch.Added, watch.Modified:
				project := r.podToProject(pod)
				if project != nil {
					r.mu.Lock()
					existing, exists := r.projects[project.ID]
					if !exists || existing.Status != project.Status {
						r.logger.Info("project updated",
							"event", event.Type,
							"project_id", project.ID,
							"status", project.Status)
					}
					r.projects[project.ID] = project
					r.mu.Unlock()
				}

			case watch.Deleted:
				project := r.podToProject(pod)
				if project != nil {
					r.mu.Lock()
					r.logger.Info("project removed", "project_id", project.ID)
					delete(r.projects, project.ID)
					r.mu.Unlock()
				}
			}
		}
	}
}

// getPodStatus queries the status of a pod using kubectl (fallback method).
func (r *ProjectRepository) getPodStatus(ctx context.Context, podName string) (domain.ProjectStatus, error) {
	// If we have a K8s client, use it directly
	if r.client != nil {
		pod, err := r.client.CoreV1().Pods(r.namespace).Get(ctx, podName, metav1.GetOptions{})
		if err != nil {
			if k8serrors.IsNotFound(err) {
				return domain.ProjectStatusNotFound, nil
			}
			return domain.ProjectStatusUnknown, fmt.Errorf("get pod: %w", err)
		}
		return r.phaseToStatus(pod.Status.Phase), nil
	}

	// Fallback to kubectl for local development
	cmd := exec.CommandContext(ctx, "kubectl",
		"get", "pod", podName,
		"-n", r.namespace,
		"-o", "jsonpath={.status.phase}",
	)

	output, err := cmd.Output()
	if err != nil {
		// Check if pod doesn't exist
		if strings.Contains(err.Error(), "not found") {
			return domain.ProjectStatusNotFound, nil
		}
		return domain.ProjectStatusUnknown, fmt.Errorf("get pod status: %w", err)
	}

	phase := strings.ToLower(strings.TrimSpace(string(output)))
	switch phase {
	case "running":
		return domain.ProjectStatusRunning, nil
	case "pending":
		return domain.ProjectStatusPending, nil
	case "failed":
		return domain.ProjectStatusFailed, nil
	default:
		return domain.ProjectStatusUnknown, nil
	}
}

// capitalizeFirst capitalizes the first letter of a string.
func capitalizeFirst(s string) string {
	if s == "" {
		return s
	}
	return strings.ToUpper(s[:1]) + s[1:]
}