package ai

import (
	"context"
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/rcourtman/pulse-go-rewrite/internal/models"
)

const (
	maxKubernetesNodeIssues       = 15
	maxKubernetesPodIssues        = 25
	maxKubernetesPodRestartLeads  = 10
	maxKubernetesDeploymentIssues = 15
	maxKubernetesMessageLength    = 160
)

var (
	ErrKubernetesStateUnavailable = errors.New("kubernetes state unavailable")
	ErrKubernetesClusterNotFound  = errors.New("kubernetes cluster not found")
)

// AnalyzeKubernetesCluster runs AI analysis for a specific Kubernetes cluster.
func (s *Service) AnalyzeKubernetesCluster(ctx context.Context, clusterID string) (*ExecuteResponse, error) {
	clusterID = strings.TrimSpace(clusterID)
	if clusterID == "" {
		return nil, fmt.Errorf("cluster_id is required")
	}

	s.mu.RLock()
	stateProvider := s.stateProvider
	s.mu.RUnlock()
	if stateProvider == nil {
		return nil, ErrKubernetesStateUnavailable
	}

	state := stateProvider.GetState()
	cluster, ok := findKubernetesCluster(state.KubernetesClusters, clusterID)
	if !ok {
		return nil, ErrKubernetesClusterNotFound
	}

	clusterName := kubernetesClusterDisplayName(cluster)
	prompt := fmt.Sprintf(
		"Analyze the Kubernetes cluster %q. Summarize health, highlight critical issues, and suggest the next actions. Be concise and specific to the telemetry.",
		clusterName,
	)

	systemPrompt := s.buildSystemPrompt(ExecuteRequest{
		Prompt:     prompt,
		TargetType: "kubernetes_cluster",
		TargetID:   cluster.ID,
	})
	systemPrompt += "\n\n## Kubernetes Cluster Telemetry\n"
	systemPrompt += buildKubernetesClusterContext(cluster)
	systemPrompt += "\n\nUse the telemetry above only. Do not request kubectl output."

	return s.Execute(ctx, ExecuteRequest{
		Prompt:       prompt,
		TargetType:   "kubernetes_cluster",
		TargetID:     cluster.ID,
		SystemPrompt: systemPrompt,
		UseCase:      "chat",
	})
}

func findKubernetesCluster(clusters []models.KubernetesCluster, clusterID string) (models.KubernetesCluster, bool) {
	for _, cluster := range clusters {
		if cluster.ID == clusterID {
			return cluster, true
		}
	}
	return models.KubernetesCluster{}, false
}

func kubernetesClusterDisplayName(cluster models.KubernetesCluster) string {
	if cluster.CustomDisplayName != "" {
		return cluster.CustomDisplayName
	}
	if cluster.DisplayName != "" {
		return cluster.DisplayName
	}
	if cluster.Name != "" {
		return cluster.Name
	}
	return cluster.ID
}

func buildKubernetesClusterContext(cluster models.KubernetesCluster) string {
	var b strings.Builder

	clusterName := kubernetesClusterDisplayName(cluster)
	b.WriteString("### Cluster Summary\n")
	b.WriteString(fmt.Sprintf("- Name: %s\n", clusterName))
	b.WriteString(fmt.Sprintf("- ID: %s\n", cluster.ID))
	if cluster.Status != "" {
		b.WriteString(fmt.Sprintf("- Status: %s\n", cluster.Status))
	}
	if cluster.Version != "" {
		b.WriteString(fmt.Sprintf("- Version: %s\n", cluster.Version))
	}
	if cluster.Server != "" {
		b.WriteString(fmt.Sprintf("- API server: %s\n", cluster.Server))
	}
	if cluster.Context != "" {
		b.WriteString(fmt.Sprintf("- Context: %s\n", cluster.Context))
	}
	if cluster.AgentVersion != "" {
		b.WriteString(fmt.Sprintf("- Agent version: %s\n", cluster.AgentVersion))
	}
	if cluster.IntervalSeconds > 0 {
		b.WriteString(fmt.Sprintf("- Telemetry interval: %ds\n", cluster.IntervalSeconds))
	}
	if !cluster.LastSeen.IsZero() {
		age := formatKubernetesAge(time.Since(cluster.LastSeen))
		b.WriteString(fmt.Sprintf("- Last seen: %s (%s ago)\n", cluster.LastSeen.Format(time.RFC3339), age))
	}
	if cluster.PendingUninstall {
		b.WriteString("- Pending uninstall: true\n")
	}

	nodeSummary, nodeIssues := summarizeKubernetesNodes(cluster.Nodes)
	podSummary, podIssues, restartLeaders := summarizeKubernetesPods(cluster.Pods)
	deploymentSummary, deploymentIssues := summarizeKubernetesDeployments(cluster.Deployments)

	b.WriteString("\n### Workload Summary\n")
	b.WriteString(nodeSummary)
	b.WriteString(podSummary)
	b.WriteString(deploymentSummary)

	if len(nodeIssues) > 0 {
		b.WriteString("\n### Unhealthy Nodes\n")
		for _, issue := range nodeIssues {
			b.WriteString("- ")
			b.WriteString(issue)
			b.WriteString("\n")
		}
	}

	if len(podIssues) > 0 {
		b.WriteString("\n### Unhealthy Pods\n")
		for _, issue := range podIssues {
			b.WriteString("- ")
			b.WriteString(issue)
			b.WriteString("\n")
		}
	}

	if len(restartLeaders) > 0 {
		b.WriteString("\n### Pods With Restarts\n")
		for _, entry := range restartLeaders {
			b.WriteString("- ")
			b.WriteString(entry)
			b.WriteString("\n")
		}
	}

	if len(deploymentIssues) > 0 {
		b.WriteString("\n### Deployments Not Fully Available\n")
		for _, issue := range deploymentIssues {
			b.WriteString("- ")
			b.WriteString(issue)
			b.WriteString("\n")
		}
	}

	return strings.TrimSpace(b.String())
}

func summarizeKubernetesNodes(nodes []models.KubernetesNode) (string, []string) {
	total := len(nodes)
	ready := 0
	notReady := 0
	unschedulable := 0
	var issues []string

	for _, node := range nodes {
		if node.Ready {
			ready++
		} else {
			notReady++
		}
		if node.Unschedulable {
			unschedulable++
		}

		if !node.Ready || node.Unschedulable {
			issue := fmt.Sprintf("%s (ready=%t, unschedulable=%t)", node.Name, node.Ready, node.Unschedulable)
			issues = append(issues, issue)
		}
	}

	if len(issues) > maxKubernetesNodeIssues {
		issues = append(issues[:maxKubernetesNodeIssues], fmt.Sprintf("... and %d more", len(issues)-maxKubernetesNodeIssues))
	}

	summary := fmt.Sprintf("- Nodes: %d total, %d ready, %d not ready, %d unschedulable\n", total, ready, notReady, unschedulable)
	return summary, issues
}

func summarizeKubernetesPods(pods []models.KubernetesPod) (string, []string, []string) {
	total := len(pods)
	phaseCounts := make(map[string]int)
	var unhealthy []podIssue
	var restarts []podIssue

	for _, pod := range pods {
		phase := strings.ToLower(strings.TrimSpace(pod.Phase))
		if phase == "" {
			phase = "unknown"
		}
		phaseCounts[phase]++

		if phase == "succeeded" {
			continue
		}

		isHealthy := isKubernetesPodHealthy(pod)
		if !isHealthy {
			unhealthy = append(unhealthy, podIssue{
				name:      pod.Name,
				namespace: pod.Namespace,
				reason:    kubernetesPodReason(pod),
				restarts:  pod.Restarts,
			})
		}

		if pod.Restarts > 0 {
			restarts = append(restarts, podIssue{
				name:      pod.Name,
				namespace: pod.Namespace,
				reason:    kubernetesPodReason(pod),
				restarts:  pod.Restarts,
			})
		}
	}

	issueLines := formatPodIssues(unhealthy, maxKubernetesPodIssues)
	restartLines := formatPodRestarts(restarts, maxKubernetesPodRestartLeads)
	summary := fmt.Sprintf(
		"- Pods: %d total, %d running, %d pending, %d failed, %d succeeded, %d unknown\n",
		total,
		phaseCounts["running"],
		phaseCounts["pending"],
		phaseCounts["failed"],
		phaseCounts["succeeded"],
		phaseCounts["unknown"],
	)
	return summary, issueLines, restartLines
}

func summarizeKubernetesDeployments(deployments []models.KubernetesDeployment) (string, []string) {
	total := len(deployments)
	healthy := 0
	var issues []string

	for _, deployment := range deployments {
		if isKubernetesDeploymentHealthy(deployment) {
			healthy++
			continue
		}
		issues = append(issues, fmt.Sprintf(
			"%s/%s desired=%d ready=%d updated=%d available=%d",
			deployment.Namespace,
			deployment.Name,
			deployment.DesiredReplicas,
			deployment.ReadyReplicas,
			deployment.UpdatedReplicas,
			deployment.AvailableReplicas,
		))
	}

	if len(issues) > maxKubernetesDeploymentIssues {
		issues = append(issues[:maxKubernetesDeploymentIssues], fmt.Sprintf("... and %d more", len(issues)-maxKubernetesDeploymentIssues))
	}

	summary := fmt.Sprintf("- Deployments: %d total, %d healthy, %d unhealthy\n", total, healthy, total-healthy)
	return summary, issues
}

type podIssue struct {
	name      string
	namespace string
	reason    string
	restarts  int
}

func formatPodIssues(issues []podIssue, limit int) []string {
	lines := make([]string, 0, min(limit, len(issues)))
	for _, issue := range issues {
		if len(lines) >= limit {
			break
		}
		lines = append(lines, formatPodIssueLine(issue))
	}
	if len(issues) > limit {
		lines = append(lines, fmt.Sprintf("... and %d more", len(issues)-limit))
	}
	return lines
}

func formatPodRestarts(issues []podIssue, limit int) []string {
	if len(issues) == 0 {
		return nil
	}
	sort.Slice(issues, func(i, j int) bool {
		if issues[i].restarts == issues[j].restarts {
			return issues[i].name < issues[j].name
		}
		return issues[i].restarts > issues[j].restarts
	})
	if len(issues) > limit {
		issues = issues[:limit]
	}

	lines := make([]string, 0, len(issues))
	for _, issue := range issues {
		line := fmt.Sprintf("%s/%s restarts=%d", issue.namespace, issue.name, issue.restarts)
		if issue.reason != "" {
			line += " " + issue.reason
		}
		lines = append(lines, line)
	}
	return lines
}

func formatPodIssueLine(issue podIssue) string {
	base := fmt.Sprintf("%s/%s", issue.namespace, issue.name)
	if issue.reason == "" {
		return base
	}
	return fmt.Sprintf("%s %s", base, issue.reason)
}

func isKubernetesPodHealthy(pod models.KubernetesPod) bool {
	phase := strings.ToLower(strings.TrimSpace(pod.Phase))
	if phase == "" {
		return false
	}
	if phase != "running" {
		return false
	}

	containers := pod.Containers
	if len(containers) == 0 {
		return true
	}

	for _, container := range containers {
		if !container.Ready {
			return false
		}
		state := strings.ToLower(strings.TrimSpace(container.State))
		if state != "" && state != "running" {
			return false
		}
	}
	return true
}

func isKubernetesDeploymentHealthy(deployment models.KubernetesDeployment) bool {
	desired := deployment.DesiredReplicas
	if desired <= 0 {
		return true
	}
	if deployment.AvailableReplicas < desired {
		return false
	}
	if deployment.ReadyReplicas < desired {
		return false
	}
	if deployment.UpdatedReplicas < desired {
		return false
	}
	return true
}

func kubernetesPodReason(pod models.KubernetesPod) string {
	var parts []string
	phase := strings.TrimSpace(pod.Phase)
	if phase != "" {
		parts = append(parts, fmt.Sprintf("phase=%s", phase))
	}
	if pod.Reason != "" {
		parts = append(parts, fmt.Sprintf("reason=%s", pod.Reason))
	}
	if message := strings.TrimSpace(pod.Message); message != "" {
		parts = append(parts, fmt.Sprintf("message=%s", truncateKubernetesMessage(message)))
	}

	containerIssues := []string{}
	for _, container := range pod.Containers {
		if container.Ready && strings.ToLower(strings.TrimSpace(container.State)) == "running" {
			continue
		}
		detail := container.Name
		if container.State != "" {
			detail += fmt.Sprintf(" state=%s", container.State)
		}
		if container.Reason != "" {
			detail += fmt.Sprintf(" reason=%s", container.Reason)
		}
		containerIssues = append(containerIssues, detail)
		if len(containerIssues) >= 3 {
			break
		}
	}
	if len(containerIssues) > 0 {
		parts = append(parts, fmt.Sprintf("containers=%s", strings.Join(containerIssues, "; ")))
	}
	if pod.Restarts > 0 {
		parts = append(parts, fmt.Sprintf("restarts=%d", pod.Restarts))
	}

	return strings.TrimSpace(strings.Join(parts, ", "))
}

func truncateKubernetesMessage(message string) string {
	if len(message) <= maxKubernetesMessageLength {
		return message
	}
	return message[:maxKubernetesMessageLength] + "..."
}

func formatKubernetesAge(duration time.Duration) string {
	if duration < time.Minute {
		seconds := int(duration.Seconds())
		if seconds < 0 {
			seconds = 0
		}
		return fmt.Sprintf("%ds", seconds)
	}
	if duration < time.Hour {
		minutes := int(duration.Minutes())
		return fmt.Sprintf("%dm", minutes)
	}
	if duration < 24*time.Hour {
		hours := int(duration.Hours())
		return fmt.Sprintf("%dh", hours)
	}
	days := int(duration.Hours() / 24)
	return fmt.Sprintf("%dd", days)
}