using System;
using System.Threading.Tasks;

namespace Microsoft.AspNet.Identity
{
    /// <summary>
    /// Represents a token provider that generates tokens from a user's security stamp and
    /// sends them to the user via their phone number.
    /// </summary>
    /// <typeparam name="TUser">The type encapsulating a user.</typeparam>
    public class PhoneNumberTokenProvider<TUser> : TotpSecurityStampBasedTokenProvider<TUser>
        where TUser : class
    {
        /// <summary>
        /// Returns a flag indicating whether the token provider can generate a token suitable for two factor authentication token for
        /// the specified <paramref name="ref"/>.
        /// </summary>
        /// <param name="manager">The <see cref="UserManager{TUser}"/> that can be used to retrieve user properties.</param>
        /// <param name="user">The user a token could be generated for.</param>
        /// <returns>
        /// The <see cref="Task"/> that represents the asynchronous operation, containing the a flag indicating if a two
        /// factor token could be generated by this provider for the specified <paramref name="user"/> and <paramref name="purpose"/>.
        /// The task will return true if a two factor authentication token could be generated as the user has
        /// a telephone number, otherwise false.
        /// </returns>
        public override async Task<bool> CanGenerateTwoFactorTokenAsync(UserManager<TUser> manager, TUser user)
        {
            if (manager == null)
            {
                throw new ArgumentNullException(nameof(manager));
            }
            var phoneNumber = await manager.GetPhoneNumberAsync(user);
            return !string.IsNullOrWhiteSpace(phoneNumber) && await manager.IsPhoneNumberConfirmedAsync(user);
        }

        /// <summary>
        /// Returns a constant, provider and user unique modifier used for entropy in generated tokens from user information, as an asynchronous operation.
        /// </summary>
        /// <param name="purpose">The purpose the token will be generated for.</param>
        /// <param name="manager">The <see cref="UserManager{TUser}"/> that can be used to retrieve user properties.</param>
        /// <param name="user">The user a token should be generated for.</param>
        /// <returns>
        /// The <see cref="Task"/> that represents the asynchronous operation, containing a constant modifier for the specified 
        /// <paramref name="user"/> and <paramref name="purpose"/>.
        /// </returns>
        public override async Task<string> GetUserModifierAsync(string purpose, UserManager<TUser> manager, TUser user)
        {
            if (manager == null)
            {
                throw new ArgumentNullException(nameof(manager));
            }
            var phoneNumber = await manager.GetPhoneNumberAsync(user);
            return "PhoneNumber:" + purpose + ":" + phoneNumber;
        }
    }
}