package httpserver

import (
	"net/http"
	"strings"

	"update_server/internal/config"
)

const contentSecurityPolicy = "default-src 'self'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; img-src 'self' data:; object-src 'none'; script-src 'self'; style-src 'self'"

func securityHeaders(cfg config.Config) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			headers := w.Header()
			headers.Set("Content-Security-Policy", contentSecurityPolicy)
			headers.Set("Cross-Origin-Opener-Policy", "same-origin")
			headers.Set("Cross-Origin-Resource-Policy", "same-origin")
			headers.Set("Permissions-Policy", "camera=(), geolocation=(), microphone=()")
			headers.Set("Referrer-Policy", "no-referrer")
			headers.Set("X-Content-Type-Options", "nosniff")
			headers.Set("X-Frame-Options", "DENY")

			if cfg.SecureCookies {
				headers.Set("Strict-Transport-Security", "max-age=31536000")
			}

			next.ServeHTTP(w, r)
		})
	}
}

func adminResponseHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		applyNoStoreHeaders(w)
		addVaryHeader(w, "Cookie")
		w.Header().Set("X-Robots-Tag", "noindex, nofollow")
		next.ServeHTTP(w, r)
	})
}

func apiResponseHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Robots-Tag", "noindex, nofollow")
		next.ServeHTTP(w, r)
	})
}

func protectedAPIResponseHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		applyNoStoreHeaders(w)
		addVaryHeader(w, "Authorization")
		w.Header().Set("X-Robots-Tag", "noindex, nofollow")
		next.ServeHTTP(w, r)
	})
}

func applyNoStoreHeaders(w http.ResponseWriter) {
	w.Header().Set("Cache-Control", "no-store, private, max-age=0")
	w.Header().Set("Pragma", "no-cache")
	w.Header().Set("Expires", "0")
}

func addVaryHeader(w http.ResponseWriter, value string) {
	value = strings.TrimSpace(value)
	if value == "" {
		return
	}

	current := w.Header().Values("Vary")
	for _, entry := range current {
		for _, existing := range strings.Split(entry, ",") {
			if strings.EqualFold(strings.TrimSpace(existing), value) {
				return
			}
		}
	}

	w.Header().Add("Vary", value)
}