package main

import (
	"bytes"
	"context"
	"encoding/json"
	"os"
	"sort"
	"strings"
	"time"

	"github.com/bep/debounce"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	klog "k8s.io/klog/v2"
)

type WellKnownService struct {
	clientset *kubernetes.Clientset
	namespace string
	cmName    string

	localCache wkRegistry
}

func NewWellKnownService(clientset *kubernetes.Clientset, namespace string, cmName string) *WellKnownService {
	return &WellKnownService{
		clientset: clientset,
		namespace: namespace,
		cmName:    cmName,
	}
}

func (s *WellKnownService) GetData(ctx context.Context) (wkRegistry, error) {
	if s.localCache != nil {
		return s.localCache, nil
	}

	cm, err := s.clientset.CoreV1().ConfigMaps(s.namespace).Get(ctx, s.cmName, metav1.GetOptions{})
	if errors.IsNotFound(err) {
		return nil, nil
	} else if err != nil {
		return nil, err
	}

	reg := make(wkRegistry)
	for name, data := range cm.Data {
		baseName := strings.TrimSuffix(name, ".json")
		id := strings.ReplaceAll(baseName, "__", "/")
		var d wkData
		if err := json.Unmarshal([]byte(data), &d); err != nil {
			klog.Error(err)
		}
		reg[id] = d
	}

	// Update the local cache
	s.localCache = reg

	return reg, nil
}

func (s *WellKnownService) UpdateConfigMap(ctx context.Context, reg wkRegistry) error {
	// Update the local cache
	s.localCache = reg

	cm := &v1.ConfigMap{Data: reg.encode()}
	cm.Namespace = s.namespace
	cm.Name = s.cmName

	_, err := s.clientset.
		CoreV1().
		ConfigMaps(s.namespace).
		Update(ctx, cm, metav1.UpdateOptions{})
	if errors.IsNotFound(err) {
		_, err = s.clientset.
			CoreV1().
			ConfigMaps(s.namespace).
			Create(ctx, cm, metav1.CreateOptions{})
		if err == nil {
			klog.Infof("Created ConfigMap %s/%s\n", cm.GetNamespace(), cm.GetName())
		}
		return err
	} else if err != nil {
		klog.Error(err)
		return err
	}
	return nil
}

// stableMarshal ensures the keys in maps are always sorted before encoding to JSON.
func stableMarshal(v interface{}) ([]byte, error) {
	buffer := &bytes.Buffer{}
	encoder := json.NewEncoder(buffer)
	encoder.SetEscapeHTML(false)
	encoder.SetIndent("", "  ")

	// Use a custom map sorter for stability
	if err := encodeSorted(encoder, v); err != nil {
		return nil, err
	}
	return buffer.Bytes(), nil
}

// encodeSorted is a helper function to sort keys before encoding map.
func encodeSorted(encoder *json.Encoder, v interface{}) error {
	switch v := v.(type) {
	case map[string]interface{}:
		// Sort the keys in the map
		keys := make([]string, 0, len(v))
		for key := range v {
			keys = append(keys, key)
		}
		sort.Strings(keys)

		// Create a new map in sorted order
		sortedMap := make(map[string]interface{})
		for _, key := range keys {
			sortedMap[key] = v[key]
		}

		return encoder.Encode(sortedMap)
	case map[string]string:
		// Sort the keys in the map
		keys := make([]string, 0, len(v))
		for key := range v {
			keys = append(keys, key)
		}
		sort.Strings(keys)

		// Create a new map in sorted order
		sortedMap := make(map[string]string)
		for _, key := range keys {
			sortedMap[key] = v[key]
		}

		return encoder.Encode(sortedMap)
	default:
		// Use default encoding for non-map types
		return encoder.Encode(v)
	}
}

func (s *WellKnownService) DiscoveryLoop(ctx context.Context) {
	// Watch for service changes in the namespace
	watch, err := s.clientset.
		CoreV1().
		Services(s.namespace).
		Watch(ctx, metav1.ListOptions{})
	if err != nil {
		klog.Error(err)
		os.Exit(1)
	}

	klog.Infof("Watching for service changes in namespace: %s", s.namespace)

	debounced := debounce.New(15000 * time.Millisecond)
	hash := []byte{}

	for event := range watch.ResultChan() {
		svc, ok := event.Object.(*v1.Service)
		if !ok {
			klog.Warning("Unexpected object type")
			continue
		}

		klog.Infof("Change detected on service: %s", svc.GetName())

		debounced(func() {
			klog.Info("Processing service change...")
			reg, err := s.collectData(ctx)
			if err != nil {
				klog.Error(err)
				return
			}

			// Generate a stable JSON representation of the registry
			newHash, err := stableMarshal(reg)
			if err != nil {
				klog.Error(err)
				return
			}

			// Compare with the previous hash
			if bytes.Equal(hash, newHash) {
				klog.V(1).Info("No changes detected, skipping update")
				return
			}
			hash = newHash

			klog.Infof("Writing configmap for discovered services...")
			if err := s.UpdateConfigMap(ctx, reg); err != nil {
				klog.Error(err)
			}
		})
	}
}

func (s *WellKnownService) collectData(ctx context.Context) (wkRegistry, error) {
	reg := make(wkRegistry)

	svcs, err := s.clientset.CoreV1().Services(s.namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return reg, err
	}

	for _, svc := range svcs.Items {
		//klog.Infof("Processing service: %s", svc.GetName())

		// Check if the service has a format lock (e.g., JSON only)
		format := "default"
		if fmtAnnotation, ok := svc.Annotations["well-known.252.no/format"]; ok {
			format = fmtAnnotation
		}

		directory := ""
		if dirAnnotation, ok := svc.Annotations["well-known.252.no/directory"]; ok {
			directory = dirAnnotation
		}

		for key, value := range svc.Annotations {
			resolvedName := resolveName(key)
			if resolvedName == "" || resolvedName == "directory" || resolvedName == "format" {
				continue
			}

			isPlainText := strings.HasSuffix(resolvedName, ".txt")
			if isPlainText {
				format = "text"
			} else if strings.HasSuffix(resolvedName, ".json") {
				format = "json"
			}

			if directory != "" {
				resolvedName = directory + "/" + resolvedName
			}

			resolvedName = strings.ReplaceAll(resolvedName, "__", "/")
			newData := parseData(value, isPlainText)

			if existingData, ok := reg[resolvedName]; ok {
				reg[resolvedName] = mergeData(existingData, newData)
			} else {
				// Store the data with the format information
				reg[resolvedName] = map[string]interface{}{
					"data":   newData,
					"format": format,
				}
			}

			//klog.Infof("Added data for %s with format %s", resolvedName, format)
		}
	}

	return reg, nil
}

func parseData(value string, isPlainText bool) wkData {
	if isPlainText {
		return value
	}
	var d map[string]interface{}
	err := json.Unmarshal([]byte(value), &d)
	if err != nil {
		klog.Error(err)
		return nil
	}
	return d
}