package service

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"metis/pkg/config"
)

// DesiredNodeMetadata captures the node identity Metis should preserve through
// recovery builds and re-assert after the node rejoins the cluster.
type DesiredNodeMetadata struct {
	Node          string            `json:"node"`
	Hostname      string            `json:"hostname,omitempty"`
	CapturedAt    time.Time         `json:"captured_at,omitempty"`
	Labels        map[string]string `json:"labels,omitempty"`
	Annotations   map[string]string `json:"annotations,omitempty"`
	Taints        []string          `json:"taints,omitempty"`
	Unschedulable bool              `json:"unschedulable,omitempty"`
}

func (a *App) loadDesiredNodeMetadata() error {
	data, err := os.ReadFile(a.settings.DesiredMetadataPath)
	if err != nil {
		return err
	}
	var desired map[string]DesiredNodeMetadata
	if err := json.Unmarshal(data, &desired); err != nil {
		return err
	}
	a.mu.Lock()
	a.desiredMetadata = desired
	a.mu.Unlock()
	return nil
}

func (a *App) persistDesiredNodeMetadata() error {
	a.mu.RLock()
	data, err := json.MarshalIndent(a.desiredMetadata, "", "  ")
	a.mu.RUnlock()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(a.settings.DesiredMetadataPath), 0o755); err != nil {
		return err
	}
	return os.WriteFile(a.settings.DesiredMetadataPath, data, 0o644)
}

func (a *App) desiredMetadataForNode(node string) (DesiredNodeMetadata, bool) {
	node = strings.TrimSpace(node)
	if node == "" {
		return DesiredNodeMetadata{}, false
	}
	a.mu.RLock()
	defer a.mu.RUnlock()
	desired, ok := a.desiredMetadata[node]
	if !ok {
		return DesiredNodeMetadata{}, false
	}
	return cloneDesiredNodeMetadata(desired), true
}

func (a *App) stageDesiredNodeMetadata(nodeName string) (DesiredNodeMetadata, error) {
	nodeName = strings.TrimSpace(nodeName)
	if nodeName == "" {
		return DesiredNodeMetadata{}, fmt.Errorf("node metadata requires a node name")
	}
	nodeSpec, _, err := a.inventory.FindNode(nodeName)
	if err != nil {
		return DesiredNodeMetadata{}, err
	}
	cfg, err := config.Build(a.inventory, nodeName)
	if err != nil {
		return DesiredNodeMetadata{}, err
	}
	desired := DesiredNodeMetadata{
		Node:       nodeName,
		Hostname:   strings.TrimSpace(nodeSpec.Hostname),
		CapturedAt: time.Now().UTC(),
		Labels:     filteredRestorableLabels(cfg.Labels),
		Taints:     restorableTaints(cfg.Taints),
	}
	if existing, ok := a.desiredMetadataForNode(nodeName); ok {
		desired = mergeDesiredNodeMetadata(desired, existing)
	}
	if live, ok := liveClusterNode(nodeName); ok {
		desired = mergeDesiredNodeMetadata(desired, desiredMetadataFromCluster(*live))
	}
	desired.Labels = normalizeStringMap(desired.Labels)
	desired.Annotations = normalizeStringMap(desired.Annotations)
	desired.Taints = normalizeTaints(desired.Taints)
	a.mu.Lock()
	if a.desiredMetadata == nil {
		a.desiredMetadata = map[string]DesiredNodeMetadata{}
	}
	a.desiredMetadata[nodeName] = desired
	a.mu.Unlock()
	if err := a.persistDesiredNodeMetadata(); err != nil {
		return DesiredNodeMetadata{}, err
	}
	return cloneDesiredNodeMetadata(desired), nil
}

func (a *App) syncDesiredNodeMetadata(record SnapshotRecord) error {
	desired, ok := a.desiredMetadataForNode(record.Node)
	if !ok {
		return nil
	}
	live, ok := liveClusterNode(record.Node)
	if !ok {
		return nil
	}
	return patchDesiredNodeMetadata(*live, desired)
}

func desiredMetadataFromCluster(node clusterNode) DesiredNodeMetadata {
	return DesiredNodeMetadata{
		Node:          strings.TrimSpace(node.Name),
		Labels:        filteredRestorableLabels(node.Labels),
		Annotations:   filteredRestorableAnnotations(node.Annotations),
		Taints:        restorableTaints(node.Taints),
		Unschedulable: node.Unschedulable,
	}
}

func mergeDesiredNodeMetadata(base, overlay DesiredNodeMetadata) DesiredNodeMetadata {
	merged := cloneDesiredNodeMetadata(base)
	if hostname := strings.TrimSpace(overlay.Hostname); hostname != "" {
		merged.Hostname = hostname
	}
	if !overlay.CapturedAt.IsZero() {
		merged.CapturedAt = overlay.CapturedAt
	}
	if merged.Labels == nil {
		merged.Labels = map[string]string{}
	}
	for key, value := range overlay.Labels {
		if key = strings.TrimSpace(key); key == "" {
			continue
		}
		merged.Labels[key] = strings.TrimSpace(value)
	}
	if merged.Annotations == nil {
		merged.Annotations = map[string]string{}
	}
	for key, value := range overlay.Annotations {
		if key = strings.TrimSpace(key); key == "" {
			continue
		}
		merged.Annotations[key] = strings.TrimSpace(value)
	}
	if len(overlay.Taints) > 0 {
		merged.Taints = normalizeTaints(overlay.Taints)
	}
	merged.Unschedulable = overlay.Unschedulable
	return merged
}

func patchDesiredNodeMetadata(live clusterNode, desired DesiredNodeMetadata) error {
	node := strings.TrimSpace(desired.Node)
	if node == "" {
		node = strings.TrimSpace(live.Name)
	}
	if node == "" {
		return nil
	}
	labelPatch := metadataStringPatch(live.Labels, desired.Labels, isRestorableLabel)
	annotationPatch := metadataStringPatch(live.Annotations, desired.Annotations, isRestorableAnnotation)
	mergedTaints := mergeLiveAndDesiredTaints(live.Taints, desired.Taints)
	body := map[string]any{}
	metadata := map[string]any{}
	if len(labelPatch) > 0 {
		metadata["labels"] = labelPatch
	}
	if len(annotationPatch) > 0 {
		metadata["annotations"] = annotationPatch
	}
	if len(metadata) > 0 {
		body["metadata"] = metadata
	}
	spec := map[string]any{}
	if live.Unschedulable != desired.Unschedulable {
		spec["unschedulable"] = desired.Unschedulable
	}
	if !sameTaints(live.Taints, mergedTaints) {
		spec["taints"] = taintPatchPayload(mergedTaints)
	}
	if len(spec) > 0 {
		body["spec"] = spec
	}
	if len(body) == 0 {
		return nil
	}
	kube, err := kubeClientFactory()
	if err != nil {
		return err
	}
	return kube.mergePatch("/api/v1/nodes/"+node, body)
}

func metadataStringPatch(live, desired map[string]string, allow func(string) bool) map[string]any {
	patch := map[string]any{}
	for key, value := range desired {
		key = strings.TrimSpace(key)
		if key == "" || !allow(key) {
			continue
		}
		value = strings.TrimSpace(value)
		if strings.TrimSpace(live[key]) != value {
			patch[key] = value
		}
	}
	for key := range live {
		key = strings.TrimSpace(key)
		if key == "" || !allow(key) {
			continue
		}
		if _, ok := desired[key]; !ok {
			patch[key] = nil
		}
	}
	return patch
}

func liveClusterNode(node string) (*clusterNode, bool) {
	node = strings.TrimSpace(node)
	if node == "" {
		return nil, false
	}
	for _, live := range clusterNodes() {
		if strings.TrimSpace(live.Name) == node {
			copyNode := live
			return &copyNode, true
		}
	}
	return nil, false
}

func filteredRestorableLabels(values map[string]string) map[string]string {
	filtered := map[string]string{}
	for key, value := range values {
		key = strings.TrimSpace(key)
		if key == "" || !isRestorableLabel(key) {
			continue
		}
		filtered[key] = strings.TrimSpace(value)
	}
	return filtered
}

func filteredRestorableAnnotations(values map[string]string) map[string]string {
	filtered := map[string]string{}
	for key, value := range values {
		key = strings.TrimSpace(key)
		if key == "" || !isRestorableAnnotation(key) {
			continue
		}
		filtered[key] = strings.TrimSpace(value)
	}
	return filtered
}

func normalizeStringMap(values map[string]string) map[string]string {
	if len(values) == 0 {
		return nil
	}
	normalized := map[string]string{}
	for key, value := range values {
		key = strings.TrimSpace(key)
		if key == "" {
			continue
		}
		normalized[key] = strings.TrimSpace(value)
	}
	if len(normalized) == 0 {
		return nil
	}
	return normalized
}

func restorableTaints(values []string) []string {
	filtered := make([]string, 0, len(values))
	for _, value := range values {
		value = normalizeTaint(value)
		if value == "" || !isRestorableTaint(value) {
			continue
		}
		filtered = append(filtered, value)
	}
	return normalizeTaints(filtered)
}

func normalizeTaints(values []string) []string {
	if len(values) == 0 {
		return nil
	}
	seen := map[string]struct{}{}
	out := make([]string, 0, len(values))
	for _, value := range values {
		value = normalizeTaint(value)
		if value == "" {
			continue
		}
		if _, ok := seen[value]; ok {
			continue
		}
		seen[value] = struct{}{}
		out = append(out, value)
	}
	sort.Strings(out)
	if len(out) == 0 {
		return nil
	}
	return out
}

func normalizeTaint(value string) string {
	return strings.TrimSpace(value)
}

func sameTaints(left, right []string) bool {
	left = normalizeTaints(left)
	right = normalizeTaints(right)
	if len(left) != len(right) {
		return false
	}
	for idx := range left {
		if left[idx] != right[idx] {
			return false
		}
	}
	return true
}

func mergeLiveAndDesiredTaints(live, desired []string) []string {
	merged := make([]string, 0, len(live)+len(desired))
	for _, taint := range live {
		taint = normalizeTaint(taint)
		if taint == "" || isRestorableTaint(taint) {
			continue
		}
		merged = append(merged, taint)
	}
	merged = append(merged, restorableTaints(desired)...)
	return normalizeTaints(merged)
}

func taintPatchPayload(values []string) []map[string]string {
	payload := make([]map[string]string, 0, len(values))
	for _, value := range normalizeTaints(values) {
		key, taintValue, effect := splitTaint(value)
		if key == "" {
			continue
		}
		entry := map[string]string{"key": key}
		if taintValue != "" {
			entry["value"] = taintValue
		}
		if effect != "" {
			entry["effect"] = effect
		}
		payload = append(payload, entry)
	}
	return payload
}

func splitTaint(raw string) (string, string, string) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return "", "", ""
	}
	effect := ""
	body := raw
	if idx := strings.LastIndex(raw, ":"); idx >= 0 {
		body = strings.TrimSpace(raw[:idx])
		effect = strings.TrimSpace(raw[idx+1:])
	}
	key := body
	value := ""
	if idx := strings.Index(body, "="); idx >= 0 {
		key = strings.TrimSpace(body[:idx])
		value = strings.TrimSpace(body[idx+1:])
	}
	return strings.TrimSpace(key), value, effect
}

func isRestorableTaint(raw string) bool {
	key, _, _ := splitTaint(raw)
	if key == "" {
		return false
	}
	for _, prefix := range []string{
		"node.kubernetes.io/",
		"node.cloudprovider.kubernetes.io/",
		"ToBeDeletedByClusterAutoscaler",
	} {
		if strings.HasPrefix(key, prefix) {
			return false
		}
	}
	return true
}

func isRestorableLabel(key string) bool {
	key = strings.TrimSpace(key)
	if key == "" {
		return false
	}
	if strings.HasPrefix(key, "node-role.kubernetes.io/") {
		return true
	}
	for _, prefix := range []string{
		"kubernetes.io/",
		"beta.kubernetes.io/",
		"node.kubernetes.io/",
		"topology.kubernetes.io/",
		"feature.node.kubernetes.io/",
		"failure-domain.beta.kubernetes.io/",
		"nvidia.com/",
		"k3s.io/",
		"rke2.io/",
		"volumes.kubernetes.io/",
		"node.cloudprovider.kubernetes.io/",
	} {
		if strings.HasPrefix(key, prefix) {
			return false
		}
	}
	return true
}

func isRestorableAnnotation(key string) bool {
	key = strings.TrimSpace(key)
	if key == "" {
		return false
	}
	for _, prefix := range []string{
		"kubectl.kubernetes.io/",
		"kubeadm.alpha.kubernetes.io/",
		"kubernetes.io/",
		"node.alpha.kubernetes.io/",
		"node.kubernetes.io/",
		"volumes.kubernetes.io/",
		"csi.volume.kubernetes.io/",
		"csi.storage.k8s.io/",
		"flannel.alpha.coreos.com/",
		"projectcalico.org/",
		"rke2.io/",
		"k3s.io/",
		"nvidia.com/",
	} {
		if strings.HasPrefix(key, prefix) {
			return false
		}
	}
	return true
}

func cloneDesiredNodeMetadata(value DesiredNodeMetadata) DesiredNodeMetadata {
	clone := value
	clone.Labels = normalizeStringMap(value.Labels)
	clone.Annotations = normalizeStringMap(value.Annotations)
	clone.Taints = normalizeTaints(value.Taints)
	return clone
}

func desiredNodeMetadataSyncEvent(node string, err error) Event {
	return Event{
		Time:    time.Now().UTC(),
		Kind:    "sentinel.node-metadata",
		Summary: fmt.Sprintf("Could not restore desired node metadata for %s", node),
		Details: map[string]any{
			"node":  node,
			"error": err.Error(),
		},
	}
}