package security

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log"
	"net/http"
	"time"
)

type nonceKey struct{}

// NonceFrom returns the per-request nonce, or empty string if none.
func NonceFrom(ctx context.Context) string {
	if v, ok := ctx.Value(nonceKey{}).(string); ok {
		return v
	}
	return ""
}

// nonce is the internal middleware that generates a cryptographic nonce per request.
func nonce(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		n := generateNonce()
		ctx := context.WithValue(r.Context(), nonceKey{}, n)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func generateNonce() string {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		log.Printf("crypto/rand failed (fallback nonce): %v", err)
		return fmt.Sprintf("%x", time.Now().UnixNano())
	}
	return base64.StdEncoding.EncodeToString(b)
}