package storage

import (
	"bytes"
	"context"
	"encoding/gob"
	"encoding/json"
	"fmt"
	"time"

	"github.com/spf13/viper"
	clientv3 "go.etcd.io/etcd/client/v3"
	"go.etcd.io/etcd/client/v3/namespace"
)

type EtcdSerializer interface {
	Deserialize(d []byte, m *any) error
	Serialize(m any) ([]byte, error)
}

type JSONEtcdSerializer struct{}

// Serialize to JSON. Will err if there are unmarshalable key values
func (s JSONEtcdSerializer) Serialize(m any) ([]byte, error) {
	return json.Marshal(m)
}

// Deserialize back to map[string]interface{}
func (s JSONEtcdSerializer) Deserialize(d []byte, m *any) (err error) {
	err = json.Unmarshal(d, &m)
	if err != nil {
		fmt.Printf("JSONSerializer.deserialize() Error: %v", err)
		return err
	}
	return
}

// GobEtcdSerializer uses gob package to encode the session map
type GobEtcdSerializer struct{}

// Serialize using gob
func (s GobEtcdSerializer) Serialize(m any) ([]byte, error) {
	buf := new(bytes.Buffer)
	enc := gob.NewEncoder(buf)
	err := enc.Encode(m)
	if err == nil {
		return buf.Bytes(), nil
	}
	return nil, err
}

// Deserialize back to map[interface{}]interface{}
func (s GobEtcdSerializer) Deserialize(d []byte, m any) error {
	dec := gob.NewDecoder(bytes.NewBuffer(d))
	return dec.Decode(&m)
}

type EtcdHandler struct {
	*clientv3.Client
	serializer EtcdSerializer
}

func NewEtcdHandler(cfg *viper.Viper) (*EtcdHandler, error) {
	var (
		endpoints = cfg.GetStringSlice("storage.kv.etcd.endpoints")
		prefix    = cfg.GetString("storage.kv.etcd.prefix")
	)

	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   endpoints,
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		return nil, err
	}

	cli.KV = namespace.NewKV(cli.KV, prefix)
	cli.Watcher = namespace.NewWatcher(cli.Watcher, prefix)
	cli.Lease = namespace.NewLease(cli.Lease, prefix)

	return &EtcdHandler{
		Client:     cli,
		serializer: JSONEtcdSerializer{},
	}, nil
}

func (s *EtcdHandler) Put(k string, v any) error {
	data, err := s.serializer.Serialize(v)
	if err != nil {
		return err
	}
	// _, err = s.Client.KV.Put(context.TODO(), k, data.String())
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	_, err = s.Client.KV.Put(ctx, k, string(data))
	cancel()
	if err != nil {
		return err
	}
	return nil
}

func (s *EtcdHandler) PutWithTTL(k string, v any, duration time.Duration) error {
	lease, err := s.Client.Lease.Grant(context.TODO(), int64(duration.Seconds()))
	if err != nil {
		return err
	}

	data, err := s.serializer.Serialize(v)
	if err != nil {
		return err
	}
	// _, err = s.Client.KV.Put(context.TODO(), k, data.String(), clientv3.WithLease(lease.ID))
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	_, err = s.Client.KV.Put(ctx, k, string(data), clientv3.WithLease(lease.ID))
	cancel()
	if err != nil {
		return err
	}
	return nil
}

func (s *EtcdHandler) Get(k string) (any, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	resp, err := s.Client.KV.Get(ctx, k)
	cancel()
	if err != nil {
		return nil, err
	}
	for _, v := range resp.Kvs {
		var data any
		err := s.serializer.Deserialize([]byte(v.Value), &data)
		if err != nil {
			return nil, err
		}
		// We return directly as we want to last revision of value
		return data, nil
	}
	return nil, fmt.Errorf("no value %v", k)
}

func (s *EtcdHandler) Delete(k string) error {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	_, err := s.Client.KV.Delete(ctx, k)
	cancel()
	if err != nil {
		return err
	}
	return nil
}