package middleware

import "net/http"

// SecurityHeaders returns a middleware that injects security hardening headers
// into every HTTP response. HSTS is only added in production to avoid breaking
// local HTTP development.
//
// Headers applied:
//   - X-Content-Type-Options: nosniff        — prevents MIME-type sniffing
//   - X-Frame-Options: DENY                  — blocks clickjacking
//   - X-XSS-Protection: 1; mode=block        — legacy XSS filter for older browsers
//   - Referrer-Policy                        — limits referrer leakage
//   - Permissions-Policy                     — disables dangerous browser features
//   - Content-Security-Policy               — restricts resource loading for API routes
//   - Cross-Origin-Opener-Policy: same-origin — isolates browsing context
//   - Strict-Transport-Security              — production only (requires HTTPS)
func SecurityHeaders(env string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			h := w.Header()
			h.Set("X-Content-Type-Options", "nosniff")
			h.Set("X-Frame-Options", "DENY")
			h.Set("X-XSS-Protection", "1; mode=block")
			h.Set("Referrer-Policy", "strict-origin-when-cross-origin")
			h.Set("Permissions-Policy", "geolocation=(), microphone=(), camera=()")
			h.Set("Content-Security-Policy", "default-src 'none'; base-uri 'self'; connect-src 'self'; frame-ancestors 'none'")
			h.Set("Cross-Origin-Opener-Policy", "same-origin")
			if env == "production" {
				h.Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
			}
			next.ServeHTTP(w, r)
		})
	}
}
