// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Security.Cryptography;
using System.Text;
using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.WebUtilities;
using Microsoft.Extensions.Options;

namespace Microsoft.AspNetCore.Antiforgery
{
    internal class AntiforgeryOptionsSetup : IConfigureOptions<AntiforgeryOptions>
    {
        private readonly DataProtectionOptions _dataProtectionOptions;

        public AntiforgeryOptionsSetup(IOptions<DataProtectionOptions> dataProtectionOptions)
        {
            _dataProtectionOptions = dataProtectionOptions.Value;
        }

        public void Configure(AntiforgeryOptions options)
        {
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }

            if (options.Cookie.Name == null)
            {
                var applicationId = _dataProtectionOptions.ApplicationDiscriminator ?? string.Empty;
                options.Cookie.Name = AntiforgeryOptions.DefaultCookiePrefix + ComputeCookieName(applicationId);
            }
        }

        private static string ComputeCookieName(string applicationId)
        {
            byte[] fullHash = SHA256.HashData(Encoding.UTF8.GetBytes(applicationId));
            return WebEncoders.Base64UrlEncode(fullHash, 0, 8);
        }
    }
}
