package k8s

import (
	"fmt"
	"strconv"
	"strings"
	"time"

	corev1 "k8s.io/api/core/v1"

	"tower/internal/model"
)

// IssuesFromPods applies the PLAN.md pod rules.
//
// Pure rule function: it does not talk to the API server.
func IssuesFromPods(pods []*corev1.Pod, now time.Time, pendingGrace time.Duration, crashLoopRestartThreshold int) []model.Issue {
	if crashLoopRestartThreshold <= 0 {
		crashLoopRestartThreshold = 5
	}
	if pendingGrace <= 0 {
		pendingGrace = 120 * time.Second
	}

	out := make([]model.Issue, 0, 32)
	for _, p := range pods {
		if p == nil {
			continue
		}
		ns, name := p.Namespace, p.Name

		// Pending for too long.
		if p.Status.Phase == corev1.PodPending {
			age := now.Sub(p.CreationTimestamp.Time)
			if !p.CreationTimestamp.IsZero() && age >= pendingGrace {
				out = append(out, model.Issue{
					ID:       fmt.Sprintf("k8s:pod:%s/%s:Pending", ns, name),
					Category: model.CategoryKubernetes,
					Priority: model.PriorityP1,
					Title:    fmt.Sprintf("Pod Pending: %s/%s", ns, name),
					Details:  fmt.Sprintf("Pod has been Pending for %s.", age.Truncate(time.Second)),
					Evidence: map[string]string{
						"kind":      "Pod",
						"reason":    "Pending",
						"namespace": ns,
						"pod":       name,
						"phase":     string(p.Status.Phase),
						"node":      p.Spec.NodeName,
					},
					SuggestedFix: fmt.Sprintf("kubectl -n %s describe pod %s", ns, name),
				})
			}
		}

		// Container-derived signals.
		for _, cs := range p.Status.ContainerStatuses {
			cname := cs.Name
			restarts := int(cs.RestartCount)

			// CrashLoopBackOff and pull errors are reported via Waiting state.
			if cs.State.Waiting != nil {
				reason := cs.State.Waiting.Reason
				msg := cs.State.Waiting.Message
				switch reason {
				case "CrashLoopBackOff":
					pri := model.PriorityP1
					if restarts >= crashLoopRestartThreshold {
						pri = model.PriorityP0
					}
					out = append(out, model.Issue{
						ID:       fmt.Sprintf("k8s:pod:%s/%s:CrashLoop:%s", ns, name, cname),
						Category: model.CategoryKubernetes,
						Priority: pri,
						Title:    fmt.Sprintf("CrashLoopBackOff: %s/%s (%s)", ns, name, cname),
						Details:  firstNonEmpty(msg, "Container is in CrashLoopBackOff."),
						Evidence: map[string]string{
							"kind":      "Pod",
							"reason":    "CrashLoopBackOff",
							"namespace": ns,
							"pod":       name,
							"container": cname,
							"restarts":  strconv.Itoa(restarts),
							"node":      p.Spec.NodeName,
						},
						SuggestedFix: strings.TrimSpace(fmt.Sprintf(`kubectl -n %s describe pod %s
kubectl -n %s logs %s -c %s --previous`, ns, name, ns, name, cname)),
					})

				case "ImagePullBackOff", "ErrImagePull":
					out = append(out, model.Issue{
						ID:       fmt.Sprintf("k8s:pod:%s/%s:ImagePull:%s", ns, name, cname),
						Category: model.CategoryKubernetes,
						Priority: model.PriorityP1,
						Title:    fmt.Sprintf("%s: %s/%s (%s)", reason, ns, name, cname),
						Details:  firstNonEmpty(msg, "Container image pull is failing."),
						Evidence: map[string]string{
							"kind":      "Pod",
							"reason":    reason,
							"namespace": ns,
							"pod":       name,
							"container": cname,
							"restarts":  strconv.Itoa(restarts),
							"node":      p.Spec.NodeName,
						},
						SuggestedFix: fmt.Sprintf("kubectl -n %s describe pod %s", ns, name),
					})
				}
			}

			// OOMKilled is typically stored in LastTerminationState.
			if cs.LastTerminationState.Terminated != nil {
				term := cs.LastTerminationState.Terminated
				if term.Reason == "OOMKilled" {
					out = append(out, model.Issue{
						ID:       fmt.Sprintf("k8s:pod:%s/%s:OOMKilled:%s", ns, name, cname),
						Category: model.CategoryKubernetes,
						Priority: model.PriorityP1,
						Title:    fmt.Sprintf("OOMKilled: %s/%s (%s)", ns, name, cname),
						Details:  firstNonEmpty(term.Message, "Container was killed due to OOM."),
						Evidence: map[string]string{
							"kind":      "Pod",
							"reason":    "OOMKilled",
							"namespace": ns,
							"pod":       name,
							"container": cname,
							"restarts":  strconv.Itoa(restarts),
							"node":      p.Spec.NodeName,
						},
						SuggestedFix: strings.TrimSpace(fmt.Sprintf(`kubectl -n %s describe pod %s
kubectl -n %s logs %s -c %s --previous`, ns, name, ns, name, cname)),
					})
				}
			}

			// High restarts even if running.
			// Keep this lower priority than active CrashLoopBackOff.
			if restarts >= crashLoopRestartThreshold {
				if cs.State.Waiting == nil || cs.State.Waiting.Reason == "" {
					out = append(out, model.Issue{
						ID:       fmt.Sprintf("k8s:pod:%s/%s:Restarts:%s", ns, name, cname),
						Category: model.CategoryKubernetes,
						Priority: model.PriorityP2,
						Title:    fmt.Sprintf("High restarts: %s/%s (%s)", ns, name, cname),
						Details:  "Container has restarted multiple times.",
						Evidence: map[string]string{
							"kind":      "Pod",
							"reason":    "HighRestarts",
							"namespace": ns,
							"pod":       name,
							"container": cname,
							"restarts":  strconv.Itoa(restarts),
							"node":      p.Spec.NodeName,
						},
						SuggestedFix: fmt.Sprintf("kubectl -n %s describe pod %s", ns, name),
					})
				}
			}
		}
	}

	return out
}

func firstNonEmpty(v, fallback string) string {
	if strings.TrimSpace(v) != "" {
		return v
	}
	return fallback
}