package peerfinder

import (
	"context"
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"log"
	"net"
	"net/http"
	"sort"
	"strconv"
	"strings"

	"github.com/oklog/ulid/v2"
	contentnegotiation "gitlab.com/jamietanna/content-negotiation-go"
	"go.opentelemetry.io/otel/attribute"
	"go.sour.is/pkg/lg"

	"go.sour.is/ev"
	"go.sour.is/ev/event"
)

var (
	//go:embed pages/* layouts/* assets/*
	files     embed.FS
	templates map[string]*template.Template
)

// Args passed to templates
type Args struct {
	RemoteIP   string
	Requests   []*Request
	CountPeers int
}

// requestArgs builds args from http.Request
func requestArgs(r *http.Request) Args {
	remoteIP, _, _ := strings.Cut(r.RemoteAddr, ":")
	if s := r.Header.Get("X-Forwarded-For"); s != "" {
		s, _, _ = strings.Cut(s, ", ")
		remoteIP = s
	}
	return Args{
		RemoteIP: remoteIP,
	}
}

// RegisterHTTP adds handler paths to the ServeMux
func (s *service) RegisterHTTP(mux *http.ServeMux) {
	a, _ := fs.Sub(files, "assets")
	assets := http.StripPrefix("/peers/assets/", http.FileServer(http.FS(a)))

	mux.Handle("/peers/assets/", lg.Htrace(assets, "peer-assets"))
	mux.Handle("/peers/", lg.Htrace(s, "peers"))
}

func (s *service) Setup() error {
	return nil
}

// ServeHTTP handle HTTP requests
func (s *service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	ctx, span := lg.Span(ctx)
	defer span.End()

	r = r.WithContext(ctx)

	if !s.up.Load() {
		w.WriteHeader(http.StatusFailedDependency)
		fmt.Fprint(w, "Starting up...")
		return
	}

	switch r.Method {
	case http.MethodGet:
		switch {
		case strings.HasPrefix(r.URL.Path, "/peers/pending/"):
			s.getPending(w, r, strings.TrimPrefix(r.URL.Path, "/peers/pending/"))
			return

		case strings.HasPrefix(r.URL.Path, "/peers/req/"):
			s.getResultsForRequest(w, r, strings.TrimPrefix(r.URL.Path, "/peers/req/"))
			return

		case strings.HasPrefix(r.URL.Path, "/peers/status"):
			var pickID string
			if strings.HasPrefix(r.URL.Path, "/peers/status/") {
				pickID = strings.TrimPrefix(r.URL.Path, "/peers/status/")
			}

			var requests []*Request

			s.state.Use(r.Context(), func(ctx context.Context, state *state) error {
				for id, p := range state.peers {
					fmt.Fprintln(w, "PEER:", id[24:], p.Owner, p.Name)
				}

				if pickID != "" {
					if rq, ok := state.requests[pickID]; ok {
						requests = append(requests, rq)
					}
				} else {
					requests = make([]*Request, 0, len(state.requests))
					for i := range state.requests {
						rq := state.requests[i]
						requests = append(requests, rq)
					}
				}

				for i := range requests {
					rq := requests[i]
					for i := range rq.Responses {
						res := rq.Responses[i]
						if peer, ok := state.peers[res.PeerID]; ok {
							res.Peer = peer
							res.Peer.ID = ""
						}
					}
				}

				return nil
			})

			for i, rq := range requests {
				fmt.Fprintln(w, "REQ: ", i, rq.RequestIP, len(rq.Responses))
				for i, peer := range fnOrderByPeer(rq) {
					fmt.Fprintln(w, "  PEER: ", i, peer.RequestID, peer.Name, peer.Latency, peer.Jitter)
					for i, res := range peer.Results {
						fmt.Fprintln(w, "    RES: ", i, res.RequestID, res.Latency, res.Jitter)
					}
				}
			}

		default:
			s.getResults(w, r)
			return
		}
	case http.MethodPost:
		switch {
		case strings.HasPrefix(r.URL.Path, "/peers/req/"):
			s.postResult(w, r, strings.TrimPrefix(r.URL.Path, "/peers/req/"))
			return

		case strings.HasPrefix(r.URL.Path, "/peers/req"):
			s.postRequest(w, r)
			return

		default:
			w.WriteHeader(http.StatusNotFound)
			return
		}
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}
}
func (s *service) getPending(w http.ResponseWriter, r *http.Request, peerID string) {
	ctx, span := lg.Span(r.Context())
	defer span.End()

	span.SetAttributes(
		attribute.String("peerID", peerID),
	)

	var peer *Peer
	err := s.state.Use(ctx, func(ctx context.Context, state *state) error {
		var ok bool
		if peer, ok = state.peers[peerID]; !ok {
			return fmt.Errorf("peer not found: %s", peerID)
		}

		return nil
	})
	if err != nil {
		span.AddEvent(err.Error())
		w.WriteHeader(http.StatusNotFound)
		return
	}

	info, err := ev.Upsert(ctx, s.es, aggInfo, func(ctx context.Context, agg *Info) error {
		return agg.OnUpsert() // initialize if not exists
	})
	if err != nil {
		span.RecordError(err)
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	requests, err := s.es.Read(ctx, queueRequests, -1, -30)
	if err != nil {
		span.RecordError(err)
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	peerResults := &PeerResults{}
	peerResults.SetStreamID(aggPeer(peerID))
	err = s.es.Load(ctx, peerResults)
	if err != nil && !errors.Is(err, ev.ErrNotFound) {
		span.AddEvent("peer not found")
		w.WriteHeader(http.StatusNotFound)
		return
	}

	var req *Request
	for _, e := range requests {
		r := &Request{}
		r.ApplyEvent(e)

		if !peerResults.Has(r.RequestID) {
			if !peer.CanSupport(r.RequestIP) {
				continue
			}
			req = r
		}
	}
	if req == nil {
		span.AddEvent("request not found")
		w.WriteHeader(http.StatusNoContent)
		return
	}

	negotiator := contentnegotiation.NewNegotiator("application/json", "text/environment", "text/plain", "text/html")
	negotiated, _, err := negotiator.Negotiate(r.Header.Get("Accept"))
	if err != nil {
		span.RecordError(err)
		w.WriteHeader(http.StatusNotAcceptable)
		return
	}

	span.AddEvent(negotiated.String())
	mime := negotiated.String()
	switch mime {
	case "text/environment":
		w.Header().Set("content-type", negotiated.String())
		_, err = encodeTo(w, info.MarshalEnviron, req.MarshalEnviron)
	case "application/json":
		w.Header().Set("content-type", negotiated.String())
		var out interface{} = info
		if req != nil {
			out = struct {
				ScriptVersion string `json:"script_version"`
				RequestID     string `json:"req_id"`
				RequestIP     string `json:"req_ip"`
				Family        string `json:"req_family"`
				Created       string `json:"req_created"`
			}{
				info.ScriptVersion,
				req.RequestID,
				req.RequestIP,
				strconv.Itoa(req.Family),
				req.CreatedString(),
			}
		}
		err = json.NewEncoder(w).Encode(out)
	}
	span.RecordError(err)
}
func (s *service) getResults(w http.ResponseWriter, r *http.Request) {
	ctx, span := lg.Span(r.Context())
	defer span.End()

	// events, err := s.es.Read(ctx, queueRequests, -1, -30)
	// if err != nil {
	// 	span.RecordError(err)
	// 	w.WriteHeader(http.StatusInternalServerError)
	// 	return
	// }

	// requests := make([]*Request, len(events))
	// for i, req := range events {
	// 	if req, ok := req.(*RequestSubmitted); ok {
	// 		requests[i], err = s.loadResult(ctx, req.RequestID())
	// 		if err != nil {
	// 			span.RecordError(err)
	// 			w.WriteHeader(http.StatusInternalServerError)
	// 			return
	// 		}
	// 	}
	// }

	var requests ListRequest
	s.state.Use(ctx, func(ctx context.Context, state *state) error {
		requests = make([]*Request, 0, len(state.requests))

		for _, req := range state.requests {
			if req.RequestID == "" {
				continue
			}
			if req.Hidden {
				continue
			}

			requests = append(requests, req)
		}

		return nil
	})
	sort.Sort(sort.Reverse(requests))

	args := requestArgs(r)
	args.Requests = requests[:min(maxResults, len(requests))]

	s.state.Use(ctx, func(ctx context.Context, state *state) error {
		args.CountPeers = len(state.peers)
		return nil
	})

	t := templates["home.go.tpl"]
	t.Execute(w, args)
}
func (s *service) getResultsForRequest(w http.ResponseWriter, r *http.Request, uuid string) {
	ctx, span := lg.Span(r.Context())
	defer span.End()

	span.SetAttributes(
		attribute.String("uuid", uuid),
	)

	var request *Request
	err := s.state.Use(ctx, func(ctx context.Context, state *state) error {
		request = state.requests[uuid]

		return nil
	})
	if err != nil {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	request, err = s.loadResult(ctx, request)

	// request, err := s.loadResult(ctx, uuid)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	negotiator := contentnegotiation.NewNegotiator("application/json", "text/environment", "text/csv", "text/plain", "text/html")
	negotiated, _, err := negotiator.Negotiate(r.Header.Get("Accept"))
	if err != nil {
		w.WriteHeader(http.StatusNotAcceptable)
		return
	}
	span.AddEvent(negotiated.String())
	switch negotiated.String() {
	// case "text/environment":
	// 	encodeTo(w, responses.MarshalBinary)
	case "application/json":
		json.NewEncoder(w).Encode(request)
		return
	default:
		args := requestArgs(r)
		args.Requests = append(args.Requests, request)
		span.AddEvent(fmt.Sprint(args))
		err := renderTo(w, "req.go.tpl", args)
		span.RecordError(err)

		return
	}
}
func (s *service) postRequest(w http.ResponseWriter, r *http.Request) {
	ctx, span := lg.Span(r.Context())
	defer span.End()

	if err := r.ParseForm(); err != nil {
		w.WriteHeader(http.StatusUnprocessableEntity)
		return
	}

	args := requestArgs(r)
	requestIP := args.RemoteIP

	if ip := r.Form.Get("req_ip"); ip != "" {
		requestIP = ip
	}

	ip := net.ParseIP(requestIP)
	if ip == nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	req := &RequestSubmitted{
		RequestIP: ip.String(),
	}
	if hidden, err := strconv.ParseBool(r.Form.Get("req_hidden")); err == nil {
		req.Hidden = hidden
	}

	span.SetAttributes(
		attribute.Stringer("req_ip", ip),
	)

	s.es.Append(ctx, queueRequests, event.NewEvents(req))

	http.Redirect(w, r, "/peers/req/"+req.RequestID(), http.StatusSeeOther)
}
func (s *service) postResult(w http.ResponseWriter, r *http.Request, reqID string) {
	ctx, span := lg.Span(r.Context())
	defer span.End()

	span.SetAttributes(
		attribute.String("id", reqID),
	)

	if _, err := ulid.ParseStrict(reqID); err != nil {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if err := r.ParseForm(); err != nil {
		w.WriteHeader(http.StatusUnprocessableEntity)
		return
	}

	form := make([]string, 0, len(r.Form))
	for k, vals := range r.Form {
		for _, v := range vals {
			form = append(form, fmt.Sprint(k, v))
		}
	}
	span.SetAttributes(
		attribute.StringSlice("form", form),
	)

	peerID := r.Form.Get("peer_id")

	err := s.state.Use(ctx, func(ctx context.Context, state *state) error {
		var ok bool
		if _, ok = state.peers[peerID]; !ok {
			log.Printf("peer not found: req=%s peer=%s\n", reqID, peerID)
			return fmt.Errorf("peer not found: req=%s peer=%s", reqID, peerID)
		}

		return nil
	})
	if err != nil {
		span.RecordError(err)
		w.WriteHeader(http.StatusNotFound)
		return
	}

	peerResults := &PeerResults{}
	peerResults.SetStreamID(aggPeer(peerID))
	err = s.es.Load(ctx, peerResults)
	if err != nil && !errors.Is(err, ev.ErrNotFound) {
		span.RecordError(fmt.Errorf("peer not found: req=%s peer=%s %w", reqID, peerID, err))
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if peerResults.Has(reqID) {
		span.RecordError(fmt.Errorf("request previously recorded: req=%v peer=%v", reqID, peerID))
		w.WriteHeader(http.StatusAlreadyReported)
		return
	}

	var unreach bool
	latency, err := strconv.ParseFloat(r.Form.Get("res_latency"), 64)
	if err != nil {
		unreach = true
	}

	req := &ResultSubmitted{
		RequestID:   reqID,
		PeerID:      r.Form.Get("peer_id"),
		PeerVersion: r.Form.Get("peer_version"),
		Latency:     latency,
		Unreachable: unreach,
	}

	if jitter, err := strconv.ParseFloat(r.Form.Get("res_jitter"), 64); err == nil {
		req.Jitter = jitter
	} else {
		span.RecordError(err)
	}
	if minrtt, err := strconv.ParseFloat(r.Form.Get("res_minrtt"), 64); err == nil {
		req.MinRTT = minrtt
	} else {
		span.RecordError(err)
	}
	if maxrtt, err := strconv.ParseFloat(r.Form.Get("res_maxrtt"), 64); err == nil {
		req.MaxRTT = maxrtt
	} else {
		span.RecordError(err)
	}

	span.SetAttributes(
		attribute.Stringer("result", req),
	)

	log.Printf("record result: %v", req)
	s.es.Append(ctx, queueResults, event.NewEvents(req))
}

func renderTo(w io.Writer, name string, args any) (err error) {
	defer func() {
		if p := recover(); p != nil {
			err = fmt.Errorf("panic: %s", p)
		}
		if err != nil {
			fmt.Fprint(w, err)
		}
	}()

	t, ok := templates[name]
	if !ok || t == nil {
		return fmt.Errorf("missing template")
	}
	return t.Execute(w, args)
}
func encodeTo(w io.Writer, fns ...func() ([]byte, error)) (int, error) {
	i := 0
	for _, fn := range fns {
		b, err := fn()
		if err != nil {
			return i, err
		}

		j, err := w.Write(b)
		i += j
		if err != nil {
			return i, err
		}
	}
	return i, nil
}

func loadTemplates() error {
	if templates != nil {
		return nil
	}
	templates = make(map[string]*template.Template)
	tmplFiles, err := fs.ReadDir(files, "pages")
	if err != nil {
		return err
	}

	for _, tmpl := range tmplFiles {
		if tmpl.IsDir() {
			continue
		}
		pt := template.New(tmpl.Name())
		pt.Funcs(funcMap)
		pt, err = pt.ParseFS(files, "pages/"+tmpl.Name(), "layouts/*.go.tpl")
		if err != nil {
			log.Println(err)

			return err
		}
		templates[tmpl.Name()] = pt
	}
	return nil
}

var funcMap = map[string]any{
	"orderByPeer":    fnOrderByPeer,
	"countResponses": fnCountResponses,
}

type peerResult struct {
	RequestID string
	Name      string
	Country   string
	Latency   float64
	Jitter    float64
}
type peer struct {
	RequestID string
	Name      string
	Note      string
	Nick      string
	Country   string
	Latency   float64
	Jitter    float64
	VPNTypes  []string

	Results peerResults
}
type listPeer []peer

func (lis listPeer) Len() int {
	return len(lis)
}
func (lis listPeer) Less(i, j int) bool {
	if lis[j].Latency == 0.0 && lis[i].Latency > 0.0 {
		return true
	}
	if lis[i].Latency == 0.0 && lis[j].Latency > 0.0 {
		return false
	}

	return lis[i].Latency < lis[j].Latency
}
func (lis listPeer) Swap(i, j int) {
	lis[i], lis[j] = lis[j], lis[i]
}

type peerResults []peerResult

func (lis peerResults) Len() int {
	return len(lis)
}
func (lis peerResults) Less(i, j int) bool {
	if lis[j].Latency == 0.0 && lis[i].Latency > 0.0 {
		return true
	}
	if lis[i].Latency == 0.0 && lis[j].Latency > 0.0 {
		return false
	}

	return lis[i].Latency < lis[j].Latency
}
func (lis peerResults) Swap(i, j int) {
	lis[i], lis[j] = lis[j], lis[i]
}

func fnOrderByPeer(rq *Request) listPeer {
	peers := make(map[string]peer)
	for i := range rq.Responses {
		if rq.Responses[i] == nil || rq.Responses[i].Peer == nil {
			continue
		}
		rs := rq.Responses[i]

		p, ok := peers[rs.Peer.Owner]

		if !ok {
			p.RequestID = rq.RequestID
			p.Country = rs.Peer.Country
			p.Name = rs.Peer.Name
			p.Nick = rs.Peer.Nick
			p.Note = rs.Peer.Note
			p.Latency = rs.Latency
			p.Jitter = rs.Jitter
			p.VPNTypes = rs.Peer.Type
		}

		p.Results = append(p.Results, peerResult{
			RequestID: rq.RequestID,
			Name:      rs.Peer.Name,
			Country:   rs.Peer.Country,
			Latency:   rs.Latency,
			Jitter:    rs.Jitter,
		})

		peers[rs.Peer.Owner] = p
	}

	peerList := make(listPeer, 0, len(peers))
	for i := range peers {
		v := peers[i]
		sort.Sort(v.Results)

		v.Name = v.Results[0].Name
		v.Country = v.Results[0].Country
		v.Latency = v.Results[0].Latency
		v.Jitter = v.Results[0].Jitter

		peerList = append(peerList, v)
	}

	sort.Sort(peerList)
	return peerList
}
func fnCountResponses(rq *Request) int {
	count := 0
	for _, res := range rq.Responses {
		if !res.Unreachable {
			count++
		}
	}
	return count
}

// func filter(peer *Peer, requests, responses event.Events) *RequestSubmitted {
// 	have := make(map[string]struct{}, len(responses))
// 	for _, res := range toList[ResultSubmitted](responses...) {
// 		have[res.RequestID] = struct{}{}
// 	}
// 	for _, req := range reverse(toList[RequestSubmitted](requests...)...) {
// 		if _, ok := have[req.RequestID()]; !ok {
// 			if !peer.CanSupport(req.RequestIP) {
// 				continue
// 			}

// 			return req
// 		}
// 	}
// 	return nil
// }
// func toList[E any, T es.PE[E]](lis ...event.Event) []T {
// 	newLis := make([]T, 0, len(lis))
// 	for i := range lis {
// 		if e, ok := lis[i].(T); ok {
// 			newLis = append(newLis, e)
// 		}
// 	}
// 	return newLis
// }
// func reverse[T any](s ...T) []T {
// 	first, last := 0, len(s)-1
// 	for first < last {
// 		s[first], s[last] = s[last], s[first]
// 		first++
// 		last--
// 	}
// 	return s
// }