using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using System.Linq;
using System.Threading.Tasks;
using Timeline.Entities;
using Timeline.Models;

namespace Timeline.Services
{
    public class CreateTokenResult
    {
        public string Token { get; set; }
        public UserInfo UserInfo { get; set; }
    }

    public enum PutUserResult
    {
        /// <summary>
        /// A new user is created.
        /// </summary>
        Created,
        /// <summary>
        /// A existing user is modified.
        /// </summary>
        Modified
    }

    public enum PatchUserResult
    {
        /// <summary>
        /// Succeed to modify user.
        /// </summary>
        Success,
        /// <summary>
        /// A user of given username does not exist.
        /// </summary>
        NotExists
    }

    public enum DeleteUserResult
    {
        /// <summary>
        /// Succeed to delete user.
        /// </summary>
        Success,
        /// <summary>
        /// A user of given username does not exist.
        /// </summary>
        NotExists
    }

    public interface IUserService
    {
        /// <summary>
        /// Try to anthenticate with the given username and password.
        /// If success, create a token and return the user info.
        /// </summary>
        /// <param name="username">The username of the user to be anthenticated.</param>
        /// <param name="password">The password of the user to be anthenticated.</param>
        /// <returns>Return null if anthentication failed. An <see cref="CreateTokenResult"/> containing the created token and user info if anthentication succeeded.</returns>
        Task<CreateTokenResult> CreateToken(string username, string password);

        /// <summary>
        /// Verify the given token.
        /// If success, return the user info.
        /// </summary>
        /// <param name="token">The token to verify.</param>
        /// <returns>Return null if verification failed. The user info if verification succeeded.</returns>
        Task<UserInfo> VerifyToken(string token);

        /// <summary>
        /// Get the user info of given username.
        /// </summary>
        /// <param name="username">Username of the user.</param>
        /// <returns>The info of the user. Null if the user of given username does not exists.</returns>
        Task<UserInfo> GetUser(string username);

        /// <summary>
        /// List all users.
        /// </summary>
        /// <returns>The user info of users.</returns>
        Task<UserInfo[]> ListUsers();

        /// <summary>
        /// Create or modify a user with given username.
        /// Return <see cref="PutUserResult.Created"/> if a new user is created.
        /// Return <see cref="PutUserResult.Modified"/> if a existing user is modified.
        /// </summary>
        /// <param name="username">Username of user.</param>
        /// <param name="password">Password of user.</param>
        /// <param name="roles">Array of roles of user.</param>
        /// <returns>Return <see cref="PutUserResult.Created"/> if a new user is created.
        /// Return <see cref="PutUserResult.Modified"/> if a existing user is modified.</returns>
        Task<PutUserResult> PutUser(string username, string password, string[] roles);

        /// <summary>
        /// Partially modify a use of given username.
        /// </summary>
        /// <param name="username">Username of the user to modify.</param>
        /// <param name="password">New password. If not modify, then null.</param>
        /// <param name="roles">New roles. If not modify, then null.</param>
        /// <returns>Return <see cref="PatchUserResult.Success"/> if modification succeeds.
        /// Return <see cref="PatchUserResult.NotExists"/> if the user of given username doesn't exist.</returns>
        Task<PatchUserResult> PatchUser(string username, string password, string[] roles); 

        /// <summary>
        /// Delete a user of given username.
        /// Return <see cref="DeleteUserResult.Success"/> if success to delete.
        /// Return <see cref="DeleteUserResult.NotExists"/> if the user of given username
        /// does not exist.
        /// </summary>
        /// <param name="username">Username of thet user to delete.</param>
        /// <returns><see cref="DeleteUserResult.Success"/> if success to delete.
        /// <see cref="DeleteUserResult.NotExists"/> if the user doesn't exist.</returns>
        Task<DeleteUserResult> DeleteUser(string username);
    }

    public class UserService : IUserService
    {
        private readonly ILogger<UserService> _logger;
        private readonly DatabaseContext _databaseContext;
        private readonly IJwtService _jwtService;
        private readonly IPasswordService _passwordService;

        public UserService(ILogger<UserService> logger, DatabaseContext databaseContext, IJwtService jwtService, IPasswordService passwordService)
        {
            _logger = logger;
            _databaseContext = databaseContext;
            _jwtService = jwtService;
            _passwordService = passwordService;
        }

        public async Task<CreateTokenResult> CreateToken(string username, string password)
        {
            var users = _databaseContext.Users.ToList();

            var user = await _databaseContext.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

            if (user == null)
            {
                _logger.LogInformation($"Create token failed with invalid username. Username = {username} Password = {password} .");
                return null;
            }

            var verifyResult = _passwordService.VerifyPassword(user.EncryptedPassword, password);

            if (verifyResult)
            {
                var userInfo = new UserInfo(user);

                return new CreateTokenResult
                {
                    Token = _jwtService.GenerateJwtToken(user.Id, userInfo.Roles),
                    UserInfo = userInfo
                };
            }
            else
            {
                _logger.LogInformation($"Create token failed with invalid password. Username = {username} Password = {password} .");
                return null;
            }
        }

        public async Task<UserInfo> VerifyToken(string token)
        {
            var userId = _jwtService.VerifyJwtToken(token);

            if (userId == null)
            {
                _logger.LogInformation($"Verify token falied. Reason: invalid token. Token: {token} .");
                return null;
            }

            var user = await _databaseContext.Users.Where(u => u.Id == userId.Value).SingleOrDefaultAsync();

            if (user == null)
            {
                _logger.LogInformation($"Verify token falied. Reason: invalid user id. UserId: {userId} Token: {token} .");
                return null;
            }

            return new UserInfo(user);
        }

        public async Task<UserInfo> GetUser(string username)
        {
            return await _databaseContext.Users
                .Where(user => user.Name == username)
                .Select(user => new UserInfo(user)).SingleOrDefaultAsync();
        }

        public async Task<UserInfo[]> ListUsers()
        {
            return await _databaseContext.Users.Select(user => new UserInfo(user)).ToArrayAsync();
        }

        public async Task<PutUserResult> PutUser(string username, string password, string[] roles)
        {
            var user = await _databaseContext.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

            if (user == null)
            {
                await _databaseContext.AddAsync(new User
                {
                    Name = username,
                    EncryptedPassword = _passwordService.HashPassword(password),
                    RoleString = string.Join(',', roles)
                });
                await _databaseContext.SaveChangesAsync();
                return PutUserResult.Created;
            }

            user.EncryptedPassword = _passwordService.HashPassword(password);
            user.RoleString = string.Join(',', roles);
            await _databaseContext.SaveChangesAsync();

            return PutUserResult.Modified;
        }

        public async Task<PatchUserResult> PatchUser(string username, string password, string[] roles)
        {
            var user = await _databaseContext.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

            if (user == null)
                return PatchUserResult.NotExists;

            bool modified = false;

            if (password != null)
            {
                modified = true;
                user.EncryptedPassword = _passwordService.HashPassword(password);
            }

            if (roles != null)
            {
                modified = true;
                user.RoleString = string.Join(',', roles);
            }

            if (modified)
            {
                await _databaseContext.SaveChangesAsync();
            }

            return PatchUserResult.Success;
        }

        public async Task<DeleteUserResult> DeleteUser(string username)
        {
            var user = await _databaseContext.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

            if (user == null)
            {
                return DeleteUserResult.NotExists;
            }

            _databaseContext.Users.Remove(user);
            await _databaseContext.SaveChangesAsync();
            return DeleteUserResult.Success;
        }
    }
}