package httpserver

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

	"kubeviz/internal/config"
	"kubeviz/internal/session"
)

const sessionCookieName = "kubeviz_session"

type Server struct {
	cfg       config.Config
	store     *session.Store
	templates *template.Template
	mux       *http.ServeMux
}

func New(cfg config.Config) (*Server, error) {
	tpls, err := template.ParseFS(templateFS, "ui/templates/*.html")
	if err != nil {
		return nil, err
	}

	s := &Server{
		cfg:       cfg,
		store:     session.NewStore(cfg.SessionTTL),
		templates: tpls,
		mux:       http.NewServeMux(),
	}
	s.routes()
	return s, nil
}

func (s *Server) routes() {
	s.mux.Handle("/", s.middleware(http.HandlerFunc(s.handleIndex)))
	s.mux.Handle("/api/manifests/parse", s.middleware(http.HandlerFunc(s.handleParseManifests)))
	s.mux.Handle("/api/helm/render", s.middleware(http.HandlerFunc(s.handleHelmRender)))
	s.mux.Handle("/api/git/import", s.middleware(http.HandlerFunc(s.handleGitImport)))
	s.mux.Handle("/api/graph", s.middleware(http.HandlerFunc(s.handleGraph)))
	s.mux.Handle("/api/diff", s.middleware(http.HandlerFunc(s.handleDiff)))
	s.mux.Handle("/api/resources/", s.middleware(http.HandlerFunc(s.handleResource)))
	s.mux.Handle("/api/export/svg", s.middleware(http.HandlerFunc(s.handleExportSVG)))
	s.mux.Handle("/api/export/png", s.middleware(http.HandlerFunc(s.handleExportPNG)))
	s.mux.Handle("/api/session/clear", s.middleware(http.HandlerFunc(s.handleClearSession)))

	staticSub, _ := fs.Sub(staticFS, "ui/static")
	s.mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(staticSub))))
}

func (s *Server) Handler() http.Handler {
	return s.mux
}

func (s *Server) Shutdown(ctx context.Context) {
	s.store.Stop()
	_ = ctx
}

func (s *Server) middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
		defer cancel()
		r = r.WithContext(ctx)

		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("Referrer-Policy", "same-origin")
		if s.cfg.AppCSPEnabled {
			w.Header().Set("Content-Security-Policy", "default-src 'self'; base-uri 'self'; object-src 'none'; frame-ancestors 'self'; script-src 'self'; script-src-elem 'self'; style-src 'self' 'unsafe-inline'; style-src-elem 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self' data:; connect-src 'self'; worker-src 'self' blob:;")
		}
		if r.TLS != nil || strings.EqualFold(r.Header.Get("X-Forwarded-Proto"), "https") {
			w.Header().Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
		}

		next.ServeHTTP(w, r)
	})
}

func (s *Server) sessionID(w http.ResponseWriter, r *http.Request) (string, error) {
	cookie, err := r.Cookie(sessionCookieName)
	if err == nil && cookie.Value != "" {
		return cookie.Value, nil
	}
	if !errors.Is(err, http.ErrNoCookie) && err != nil {
		return "", err
	}
	sid, err := s.store.NewSessionID()
	if err != nil {
		return "", err
	}
	http.SetCookie(w, &http.Cookie{
		Name:     sessionCookieName,
		Value:    sid,
		Path:     "/",
		HttpOnly: true,
		Secure:   s.cfg.CookieSecure,
		SameSite: http.SameSiteLaxMode,
		MaxAge:   int(s.cfg.SessionTTL.Seconds()),
	})
	return sid, nil
}

func parseRelations(raw string) map[string]bool {
	return parseCSVSet(raw)
}

func parseCSVSet(raw string) map[string]bool {
	if raw == "" {
		return nil
	}
	out := map[string]bool{}
	for _, item := range strings.Split(raw, ",") {
		trimmed := strings.TrimSpace(item)
		if trimmed == "" {
			continue
		}
		out[trimmed] = true
	}
	return out
}

func writeJSON(w http.ResponseWriter, status int, payload any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(payload); err != nil {
		log.Printf("failed writing JSON: %v", err)
	}
}

func subFS(fsys embed.FS, dir string) fs.FS {
	sub, err := fs.Sub(fsys, dir)
	if err != nil {
		panic(err)
	}
	return sub
}