package infrastructure

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"oc-peer/conf"
	"slices"
	"sync"
	"time"

	oclib "cloud.o-forge.io/core/oc-lib"
	pp "cloud.o-forge.io/core/oc-lib/models/peer"
	"cloud.o-forge.io/core/oc-lib/models/utils"
	"cloud.o-forge.io/core/oc-lib/tools"
	"github.com/google/uuid"
	"github.com/libp2p/go-libp2p"
	dht "github.com/libp2p/go-libp2p-kad-dht"
	"github.com/libp2p/go-libp2p/core/crypto"
	"github.com/libp2p/go-libp2p/core/host"
)

type DHTRecord struct {
	Name       string    `json:"name"`
	State      int       `json:"state"`
	DID        string    `json:"did"`
	PeerID     string    `json:"peer_id"`
	PubKey     []byte    `json:"pub_key"`
	URL        string    `json:"url"`
	NATSUrl    string    `json:"nats_url"`
	Wallet     string    `json:"wallet"`
	Signature  []byte    `json:"signature"`
	ExpiryDate time.Time `json:"expiry_date"`
}

type DHTService struct {
	Key   string
	Host  host.Host
	DHT   *dht.IpfsDHT
	Cache []string
	mutex sync.RWMutex
}

var singletonService *DHTService

func GetDHTService() *DHTService {
	return singletonService
}

func Init(ctx context.Context) (*DHTService, error) {
	service := &DHTService{}
	priv, err := LoadKeyFromFile(false)
	if err != nil {
		return nil, err
	}
	h, err := libp2p.New(
		libp2p.Identity(priv),
		libp2p.ListenAddrStrings(
			fmt.Sprintf("/ip4/0.0.0.0/tcp/%d", conf.GetConfig().DHTEndpointPort),
		),
	)
	if err != nil {
		return nil, err
	}
	service.Host = h
	service.DHT, err = dht.New(ctx, h, dht.MaxRecordAge(24*time.Hour)) // every day DHT will purge expired data... if not used.
	if err != nil {
		return nil, err
	}
	err = service.DHT.Bootstrap(ctx)
	if err != nil {
		return nil, err
	}
	singletonService = service
	if VerifyPubWithPriv() {
		if _, err := singletonService.ClaimName(context.Background(),
			conf.GetConfig().Name,
			conf.GetConfig().Hostname); err == nil {
			go service.RefreshKeys(ctx, 30*time.Minute)
		}
	}

	return service, nil
}

func (d *DHTService) RefreshKeys(ctx context.Context, interval time.Duration) {
	ticker := time.NewTicker(interval)
	go func() {
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				s := []string{}
				d.mutex.Lock()
				s = append(s, d.Cache...)
				d.mutex.Unlock()
				for _, key := range s {
					_, _ = d.GetValue(ctx, key)
				}
			}
		}
	}()
}

func (d *DHTService) PutValue(
	ctx context.Context,
	key string,
	value []byte,
) error {
	err := d.DHT.PutValue(ctx, key, value)
	if err != nil {
		return err
	}
	d.mutex.Lock()
	if !slices.Contains(d.Cache, key) {
		d.Cache = append(d.Cache, key)
	}
	d.mutex.Unlock()
	return nil
}

func (d *DHTService) GetValue(
	ctx context.Context,
	key string,
) (*DHTRecord, error) {
	dht, err := d.DHT.GetValue(ctx, key)
	if err != nil {
		cache := []string{}
		d.mutex.Lock()
		for _, c := range d.Cache {
			if c != key {
				cache = append(cache, c)
			}
		}
		d.Cache = cache
		d.mutex.Unlock()
		return nil, err
	}
	d.mutex.Lock()
	if !slices.Contains(d.Cache, key) {
		d.Cache = append(d.Cache, key)
	}
	d.mutex.Unlock()
	var data DHTRecord
	json.Unmarshal(dht, &data)

	peerID, err := oclib.GenerateNodeID()
	if err != nil {
		return nil, err
	}

	access := pp.NewAccessor(&tools.APIRequest{Admin: true})
	p := &pp.Peer{
		AbstractObject: utils.AbstractObject{
			UUID: uuid.New().String(),
			Name: data.Name,
		},
		State:         pp.ONLINE,
		Relation:      pp.SELF,
		PeerID:        peerID,
		PublicKey:     string(data.PubKey),
		Url:           data.URL,
		NATSUrl:       oclib.GetConfig().NATSUrl,
		WalletAddress: data.Wallet,
	}
	if founded, _, err := access.Search(nil, fmt.Sprintf("%v", pp.SELF.EnumIndex()), false); err != nil || len(founded) == 0 {
		access.StoreOne(p)
	} else if f, _, err := access.LoadOne(founded[0].GetID()); err == nil && f.(*pp.Peer).Relation != pp.BLACKLIST {
		f.(*pp.Peer).State = pp.ONLINE
		f.(*pp.Peer).NATSUrl = p.NATSUrl
		f.(*pp.Peer).Url = p.Url
		f.(*pp.Peer).PeerID = p.PeerID
		f.(*pp.Peer).Relation = p.Relation
		f.(*pp.Peer).WalletAddress = p.WalletAddress
		access.UpdateOne(f, f.GetID())
	}

	return &data, err
}

func (d *DHTService) generateKey() (string, error) {
	s, err := oclib.GenerateNodeID()
	if err != nil {
		return s, err
	}
	return "/opencloud/peer/" + s, nil
}

// Create your peer.
func (d *DHTService) ClaimName(
	ctx context.Context,
	name string,
	endPoint string,
) (*pp.Peer, error) {
	if endPoint == "" {
		return nil, errors.New("no endpoint found for peer" + name)
	}

	peerID, err := oclib.GenerateNodeID()
	if err != nil {
		return nil, err
	}

	pub := d.Host.Peerstore().PubKey(d.Host.ID())
	pubBytes, _ := pub.Raw()

	now := time.Now()
	expiry := now.Add(1 * time.Hour)

	rec := DHTRecord{
		Name:   name,
		PeerID: peerID,
		PubKey: pubBytes,
	}

	payload, _ := json.Marshal(rec)
	sig, _ := sign(d.Host.Peerstore().PrivKey(d.Host.ID()), payload)
	rec.Signature = sig

	rec.URL = endPoint
	rec.NATSUrl = oclib.GetConfig().NATSUrl
	rec.State = pp.ONLINE.EnumIndex()
	rec.ExpiryDate = expiry

	data, _ := json.Marshal(rec)

	key, err := d.generateKey()
	if err != nil {
		return nil, err
	}

	// retrieve your key name in standard
	old, err := d.GetValue(ctx, key)
	if err == nil {
		if old.PeerID != peerID { // check if someone claims your name before
			return nil, errors.New("name already claimed by another peer")
			// TODO : can be fragile if 2 peers connect at the same time
		}
		if now.After(old.ExpiryDate) {
			payload, _ := json.Marshal(rec)
			d.PutValue(ctx, key, payload)
		}
	}

	if err := d.PutValue(ctx, key, data); err != nil {
		return nil, err
	}

	pubStr := base64.StdEncoding.EncodeToString(pubBytes)
	d.Key = key
	access := pp.NewAccessor(&tools.APIRequest{Admin: true})
	if err != nil {
		return nil, err
	}
	p := &pp.Peer{
		AbstractObject: utils.AbstractObject{
			UUID: uuid.New().String(),
			Name: name,
		},
		State:         pp.ONLINE,
		Relation:      pp.SELF,
		PeerID:        peerID,
		PublicKey:     pubStr,
		Url:           endPoint,
		NATSUrl:       oclib.GetConfig().NATSUrl,
		WalletAddress: "my-wallet",
	}
	if founded, _, err := access.Search(nil, fmt.Sprintf("%v", pp.SELF.EnumIndex()), false); err != nil || len(founded) == 0 {
		access.StoreOne(p)
	} else if f, _, err := access.LoadOne(founded[0].GetID()); err == nil {
		peerID, err := oclib.GenerateNodeID()
		if err != nil {
			return nil, err
		}
		f.(*pp.Peer).Name = name
		f.(*pp.Peer).PeerID = peerID
		f.(*pp.Peer).State = pp.ONLINE
		f.(*pp.Peer).Url = endPoint
		f.(*pp.Peer).NATSUrl = oclib.GetConfig().NATSUrl
		f.(*pp.Peer).Relation = pp.SELF
		access.UpdateOne(f, f.GetID())
	}

	return p, nil
}

func (d *DHTService) treatPeer(ctx context.Context, key string, rec *DHTRecord) (*pp.Peer, error) {
	pubKey, err := crypto.UnmarshalPublicKey(rec.PubKey)
	if err != nil {
		return nil, err
	}

	now := time.Now()
	dht := DHTRecord{
		Name:   rec.Name,
		PeerID: rec.PeerID,
		PubKey: rec.PubKey,
	}
	payload, _ := json.Marshal(dht)

	if ok, _ := verify(pubKey, payload, rec.Signature); !ok {
		return nil, errors.New("invalid signature")
	}
	pubBytes, _ := pubKey.Raw()
	pubStr := base64.StdEncoding.EncodeToString(pubBytes)

	rel := pp.NONE
	if d.Key == key {
		rel = pp.SELF
	}

	p := &pp.Peer{
		AbstractObject: utils.AbstractObject{
			UUID: uuid.New().String(),
			Name: rec.Name,
		},
		State:         pp.ONLINE,
		Relation:      rel,
		PeerID:        rec.PeerID,
		PublicKey:     pubStr,
		Url:           rec.URL,
		NATSUrl:       rec.NATSUrl,
		WalletAddress: rec.Wallet,
	}
	access := pp.NewAccessor(&tools.APIRequest{Admin: true})
	if now.After(rec.ExpiryDate) {
		rec.State = pp.OFFLINE.EnumIndex()
		p.State = pp.OFFLINE
		payload, _ := json.Marshal(rec)
		d.PutValue(ctx, key, payload)
		if founded, _, err := access.Search(nil, p.Name, false); err != nil || len(founded) == 0 {
			access.StoreOne(p)
		} else if f, _, err := access.LoadOne(founded[0].GetID()); err == nil {
			f.(*pp.Peer).State = pp.OFFLINE
			access.UpdateOne(f, f.GetID())
		}
		return nil, errors.New("peer " + key + " is expired")
	}
	if rec.State == pp.OFFLINE.EnumIndex() {
		if founded, _, err := access.Search(nil, p.Name, false); err != nil || len(founded) == 0 {
			ppp, _, err := access.StoreOne(p)
			if err == nil {
				return ppp.(*pp.Peer), nil
			}
		} else {
			f, ok := pp.CheckPeerStatus(founded[0].GetID(), "")
			if ok {
				f.State = pp.ONLINE
			} else {
				f.State = pp.OFFLINE
			}
			ppp, _, err := access.UpdateOne(f, f.GetID())
			if err == nil && ok {
				return ppp.(*pp.Peer), nil
			}
		}
	}
	return nil, errors.New("peer " + key + " is offline")
}

// Discover a specific Peer
func (d *DHTService) DiscoverPeers(
	ctx context.Context,
	name string,
) ([]*pp.Peer, error) {
	peers := []*pp.Peer{}
	key, err := d.generateKey()
	if err != nil {
		return nil, err
	}
	datas, err := d.DHT.SearchValue(ctx, key)
	if err != nil {
		return nil, errors.New("no DHT peer not found")
	}
	for data := range datas {
		var dht *DHTRecord
		json.Unmarshal(data, dht)
		if p, err := d.treatPeer(ctx, key, dht); err == nil {
			peers = append(peers, p)
		}
	}
	return peers, nil
}

func (d *DHTService) GetPeer(
	ctx context.Context,
	name string,
) (*pp.Peer, error) {
	key, err := d.generateKey()
	if err != nil {
		return nil, err
	}
	data, err := d.GetValue(ctx, key)
	if err != nil {
		return nil, errors.New("no DHT peer not found")
	}
	return d.treatPeer(ctx, key, data)
}

func (d *DHTService) existsDHT(ctx context.Context) (*DHTRecord, error) {
	if d.Key == "" {
		return nil, errors.New("no self peer found")
	}
	rec, err := d.GetValue(ctx, d.Key)
	if err != nil {
		return nil, errors.New("no DHT peer found")
	}

	pubKey, err := crypto.UnmarshalPublicKey(rec.PubKey)
	if err != nil {
		return rec, err
	}

	dht := DHTRecord{
		Name:   rec.Name,
		PeerID: rec.PeerID,
		PubKey: rec.PubKey,
	}
	payload, _ := json.Marshal(dht)

	if ok, _ := verify(pubKey, payload, rec.Signature); !ok {
		return rec, err
	}
	return rec, nil
}