package middleware

import (
	"net/http"
	"os"
)

// SecurityHeaders adds production-grade security headers to responses
func SecurityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Prevent clickjacking
		w.Header().Set("X-Frame-Options", "SAMEORIGIN")

		// Prevent MIME type sniffing
		w.Header().Set("X-Content-Type-Options", "nosniff")

		// XSS Protection (legacy but still useful for older browsers)
		w.Header().Set("X-XSS-Protection", "1; mode=block")

		// Referrer policy - strict privacy
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")

		// Permissions Policy - disable unnecessary features
		w.Header().Set("Permissions-Policy",
			"geolocation=(), microphone=(), camera=(), payment=(), usb=(), "+
				"magnetometer=(), gyroscope=(), accelerometer=()")

		// Content Security Policy (comprehensive)
		csp := "default-src 'self'; " +
			"script-src 'self' 'unsafe-inline' https://unpkg.com https://code.iconify.design; " +
			"style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; " +
			"font-src 'self' https://fonts.gstatic.com; " +
			"img-src 'self' data: https:; " +
			"connect-src 'self' https://api.iconify.design; " +
			"frame-ancestors 'self'; " +
			"base-uri 'self'; " +
			"form-action 'self'"
		w.Header().Set("Content-Security-Policy", csp)

		// HSTS - only in production with HTTPS
		if os.Getenv("GO_ENV") == "production" {
			// 1 year max-age, include subdomains
			w.Header().Set("Strict-Transport-Security",
				"max-age=31536000; includeSubDomains; preload")
		}

		next.ServeHTTP(w, r)
	})
}