package web

import (
	"context"
	"embed"
	"fmt"
	"html/template"
	"io/fs"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
	"unicode/utf8"

	"ts3monolith/internal/config"
	"ts3monolith/internal/rrd"
	"ts3monolith/internal/ts3"
)

//go:embed templates/*.html assets/*
var embedded embed.FS

type Server struct {
	cfg    config.Config
	ts     *ts3.Query
	rrd    *rrd.Manager
	tpl    *template.Template
	tokens *tokenManager
	limit  *limiter
}

type channelPage struct {
	ClientIP       string
	Clients        []ts3.Client
	Client         *ts3.Client
	ClientToken    string
	FormToken      string
	ChallengeToken string
	Error          string
	Success        string
	ChannelID      int
	VoiceURL       string
}

type statsPage struct {
	Current  int
	VoiceURL string
	Ranges   []rrd.Range
}

func New(cfg config.Config, tq *ts3.Query, rm *rrd.Manager) (*Server, error) {
	tpl, err := template.ParseFS(embedded, "templates/*.html")
	if err != nil {
		return nil, err
	}
	return &Server{cfg: cfg, ts: tq, rrd: rm, tpl: tpl, tokens: newTokenManager(cfg.AppSecret), limit: newLimiter()}, nil
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	assets, _ := fs.Sub(embedded, "assets")
	mux.Handle("GET /assets/", http.StripPrefix("/assets/", http.FileServer(http.FS(assets))))
	mux.HandleFunc("GET /{$}", func(w http.ResponseWriter, r *http.Request) { http.Redirect(w, r, "/stats", http.StatusFound) })
	mux.HandleFunc("GET /stats", s.stats)
	mux.HandleFunc("GET /graph/{file}", s.graph)
	mux.HandleFunc("GET /channel", s.channel)
	mux.HandleFunc("GET /embed/channel", s.channel)
	mux.HandleFunc("POST /channel/verify/start", s.verifyStart)
	mux.HandleFunc("POST /channel/verify/complete", s.verifyComplete)
	mux.HandleFunc("POST /channel/create", s.createChannel)
	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		_, _ = w.Write([]byte("ok\n"))
	})
	return s.security(mux)
}

func (s *Server) security(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("Referrer-Policy", "no-referrer")
		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=(), payment=(), usb=()")
		w.Header().Set("Cross-Origin-Opener-Policy", "same-origin")
		if s.cfg.HTTPSOnly {
			w.Header().Set("Strict-Transport-Security", "max-age=31536000")
		}
		frame := "'none'"
		if strings.HasPrefix(r.URL.Path, "/embed/channel") || strings.HasPrefix(r.URL.Path, "/channel/") {
			frame = strings.Join(s.cfg.FrameAncestors, " ")
		}
		w.Header().Set("Content-Security-Policy", "default-src 'self'; base-uri 'none'; object-src 'none'; frame-ancestors "+frame+"; form-action 'self'; img-src 'self'; style-src 'self'; script-src 'self'")
		next.ServeHTTP(w, r)
	})
}

func (s *Server) stats(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r).String()
	if !s.limit.allow("stats|"+ip, 60, time.Minute) {
		s.tooMany(w)
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), s.cfg.TSQueryTimeout)
	defer cancel()
	current, err := s.ts.CountOnline(ctx)
	if err != nil {
		ctx2, cancel2 := context.WithTimeout(r.Context(), 2*time.Second)
		defer cancel2()
		current, _ = s.rrd.Last(ctx2)
	}
	w.Header().Set("Cache-Control", "no-store")
	s.render(w, "stats.html", statsPage{Current: current, VoiceURL: s.voiceURL(), Ranges: rrd.Ranges})
}

func (s *Server) graph(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r).String()
	if !s.limit.allow("graph|"+ip, 120, time.Minute) {
		s.tooMany(w)
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), 8*time.Second)
	defer cancel()
	file := r.PathValue("file")
	if !strings.HasSuffix(file, ".png") {
		http.NotFound(w, r)
		return
	}
	key := strings.TrimSuffix(file, ".png")
	if key == "" || strings.Contains(key, "/") {
		http.NotFound(w, r)
		return
	}
	p, err := s.rrd.Graph(ctx, key)
	if err != nil {
		http.Error(w, "graph unavailable", http.StatusServiceUnavailable)
		return
	}
	w.Header().Set("Cache-Control", "public, max-age=60")
	http.ServeFile(w, r, p)
}

func (s *Server) channel(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r)
	if ip == nil {
		http.Error(w, "invalid client address", http.StatusBadRequest)
		return
	}
	if !s.limit.allow("channel|"+ip.String(), 40, time.Minute) {
		s.tooMany(w)
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), s.cfg.TSQueryTimeout)
	defer cancel()
	clients, err := s.ts.ClientsByIP(ctx, ip)
	p := channelPage{ClientIP: ip.String(), Clients: clients, FormToken: s.tokens.formToken(ip.String()), VoiceURL: s.voiceURL()}
	if err != nil {
		p.Error = "Nie udało się sprawdzić połączenia z TeamSpeak."
	}
	if len(clients) == 1 {
		p.Client = &clients[0]
		p.ClientToken = s.tokens.clientToken(ip.String(), clients[0])
	}
	w.Header().Set("Cache-Control", "no-store")
	s.render(w, "channel.html", p)
}

func (s *Server) verifyStart(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r)
	if ip == nil {
		http.Error(w, "bad request", 400)
		return
	}
	if !s.requirePost(w, r, ip.String()) {
		return
	}
	if !s.limit.allow("verify|"+ip.String(), 10, time.Minute) {
		s.tooMany(w)
		return
	}
	if _, err := s.tokens.verify(r.FormValue("form_token"), "form", ip.String()); err != nil {
		http.Error(w, "invalid form", http.StatusForbidden)
		return
	}
	clid, _ := strconv.Atoi(r.FormValue("clid"))
	ctx, cancel := context.WithTimeout(r.Context(), s.cfg.TSQueryTimeout)
	defer cancel()
	clients, err := s.ts.ClientsByIP(ctx, ip)
	if err != nil {
		http.Error(w, "verification unavailable", 503)
		return
	}
	var selected *ts3.Client
	for i := range clients {
		if clients[i].ID == clid {
			selected = &clients[i]
			break
		}
	}
	if selected == nil {
		http.Error(w, "client unavailable", 409)
		return
	}
	challenge, code, _ := s.tokens.challengeToken(ip.String(), *selected)
	if err := s.ts.SendPrivateMessage(ctx, selected.ID, "Kod weryfikacyjny strony tworzenia kanału: "+code+". Kod jest ważny 5 minut."); err != nil {
		http.Error(w, "could not send verification", 503)
		return
	}
	p := channelPage{ClientIP: ip.String(), Client: selected, ChallengeToken: challenge, FormToken: s.tokens.formToken(ip.String()), VoiceURL: s.voiceURL()}
	s.render(w, "verify.html", p)
}

func (s *Server) verifyComplete(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r)
	if ip == nil {
		http.Error(w, "bad request", 400)
		return
	}
	if !s.requirePost(w, r, ip.String()) {
		return
	}
	if !s.limit.allow("verifydone|"+ip.String(), 10, time.Minute) {
		s.tooMany(w)
		return
	}
	if _, err := s.tokens.verify(r.FormValue("form_token"), "form", ip.String()); err != nil {
		http.Error(w, "invalid form", 403)
		return
	}
	pld, err := s.tokens.verify(r.FormValue("challenge_token"), "challenge", ip.String())
	if err != nil || r.FormValue("code") != s.tokens.challengeCode(pld) {
		http.Error(w, "invalid or expired code", 403)
		return
	}
	c := ts3.Client{ID: pld.ClID, DatabaseID: pld.DBID, Nick: pld.Nick, UID: pld.UID, IP: ip.String()}
	p := channelPage{ClientIP: ip.String(), Client: &c, ClientToken: s.tokens.clientToken(ip.String(), c), FormToken: s.tokens.formToken(ip.String()), VoiceURL: s.voiceURL()}
	s.render(w, "channel.html", p)
}

func (s *Server) createChannel(w http.ResponseWriter, r *http.Request) {
	ip := s.clientIP(r)
	if ip == nil {
		http.Error(w, "bad request", 400)
		return
	}
	if !s.requirePost(w, r, ip.String()) {
		return
	}
	if !s.limit.allow("create|"+ip.String(), 5, time.Hour) {
		s.tooMany(w)
		return
	}
	if _, err := s.tokens.verify(r.FormValue("form_token"), "form", ip.String()); err != nil {
		http.Error(w, "invalid form", 403)
		return
	}
	pld, err := s.tokens.verify(r.FormValue("client_token"), "client", ip.String())
	if err != nil {
		http.Error(w, "client verification expired", 403)
		return
	}
	name := strings.TrimSpace(r.FormValue("name"))
	topic := strings.TrimSpace(r.FormValue("topic"))
	password := r.FormValue("password")
	if name == "" {
		name = randomChannelName()
	}
	if err := validateInput(name, topic, password); err != nil {
		c := ts3.Client{ID: pld.ClID, DatabaseID: pld.DBID, Nick: pld.Nick, UID: pld.UID, IP: ip.String()}
		s.render(w, "channel.html", channelPage{ClientIP: ip.String(), Client: &c, ClientToken: r.FormValue("client_token"), FormToken: s.tokens.formToken(ip.String()), Error: err.Error(), VoiceURL: s.voiceURL()})
		return
	}
	c := ts3.Client{ID: pld.ClID, DatabaseID: pld.DBID, Nick: pld.Nick, UID: pld.UID, IP: ip.String()}
	ctx, cancel := context.WithTimeout(r.Context(), 6*time.Second)
	defer cancel()
	cid, err := s.ts.CreateChannelForClient(ctx, c, s.cfg.TSChannelAdminGID, name, topic, password)
	if err != nil {
		log.Printf("channel create failed for client dbid=%d: %v", c.DatabaseID, err)
		s.render(w, "channel.html", channelPage{ClientIP: ip.String(), Client: &c, ClientToken: s.tokens.clientToken(ip.String(), c), FormToken: s.tokens.formToken(ip.String()), Error: "Nie udało się utworzyć kanału. Sprawdź połączenie z TS3 i spróbuj ponownie.", VoiceURL: s.voiceURL()})
		return
	}
	s.render(w, "channel.html", channelPage{ClientIP: ip.String(), Client: &c, FormToken: s.tokens.formToken(ip.String()), Success: "Kanał został utworzony, uprawnienia nadane, a klient przeniesiony.", ChannelID: cid, VoiceURL: s.voiceURL()})
}

func (s *Server) requirePost(w http.ResponseWriter, r *http.Request, ip string) bool {
	r.Body = http.MaxBytesReader(w, r.Body, 16<<10)
	if err := r.ParseForm(); err != nil {
		http.Error(w, "bad request", 400)
		return false
	}
	if o := r.Header.Get("Origin"); o != "" {
		u, err := url.Parse(o)
		if err != nil || !strings.EqualFold(u.Host, r.Host) {
			http.Error(w, "forbidden", 403)
			return false
		}
	}
	return true
}

func validateInput(name, topic, password string) error {
	if utf8.RuneCountInString(name) < 1 || utf8.RuneCountInString(name) > 40 {
		return fmt.Errorf("Nazwa kanału musi mieć 1–40 znaków.")
	}
	if utf8.RuneCountInString(topic) > 255 {
		return fmt.Errorf("Temat może mieć maksymalnie 255 znaków.")
	}
	if utf8.RuneCountInString(password) > 64 {
		return fmt.Errorf("Hasło może mieć maksymalnie 64 znaki.")
	}
	for _, v := range []string{name, topic, password} {
		if strings.ContainsRune(v, '\x00') {
			return fmt.Errorf("Nieprawidłowe dane wejściowe.")
		}
	}
	return nil
}

func randomChannelName() string { return "channel-" + randomNonce()[:10] }

func (s *Server) clientIP(r *http.Request) net.IP {
	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		host = r.RemoteAddr
	}
	remote := net.ParseIP(strings.TrimSpace(host))
	if remote == nil {
		return nil
	}
	trusted := false
	for _, n := range s.cfg.TrustedProxies {
		if n.Contains(remote) {
			trusted = true
			break
		}
	}
	if !trusted {
		return remote
	}
	for _, h := range []string{"CF-Connecting-IP", "X-Real-IP"} {
		if v := strings.TrimSpace(r.Header.Get(h)); v != "" {
			if ip := net.ParseIP(v); ip != nil {
				return ip
			}
		}
	}
	if v := r.Header.Get("X-Forwarded-For"); v != "" {
		if ip := net.ParseIP(strings.TrimSpace(strings.Split(v, ",")[0])); ip != nil {
			return ip
		}
	}
	return remote
}

func (s *Server) voiceURL() string {
	return "ts3server://" + s.cfg.TSVoiceHost + "?port=" + strconv.Itoa(s.cfg.TSVoicePort)
}
func (s *Server) tooMany(w http.ResponseWriter) {
	w.Header().Set("Retry-After", "60")
	http.Error(w, "too many requests", http.StatusTooManyRequests)
}
func (s *Server) render(w http.ResponseWriter, name string, data any) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := s.tpl.ExecuteTemplate(w, name, data); err != nil {
		log.Printf("template error: %v", err)
	}
}

func EnsureGraphDir(path string) error { return os.MkdirAll(filepath.Clean(path), 0750) }