using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using System.Web;
using API.Constants;
using API.Data;
using API.Data.Repositories;
using API.DTOs;
using API.DTOs.Account;
using API.DTOs.Email;
using API.Entities;
using API.Entities.Enums;
using API.Errors;
using API.Extensions;
using API.Services;
using AutoMapper;
using Kavita.Common;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace API.Controllers
{
    /// <summary>
    /// All Account matters
    /// </summary>
    public class AccountController : BaseApiController
    {
        private readonly UserManager<AppUser> _userManager;
        private readonly SignInManager<AppUser> _signInManager;
        private readonly ITokenService _tokenService;
        private readonly IUnitOfWork _unitOfWork;
        private readonly ILogger<AccountController> _logger;
        private readonly IMapper _mapper;
        private readonly IAccountService _accountService;
        private readonly IEmailService _emailService;
        private readonly IHostEnvironment _environment;

        /// <inheritdoc />
        public AccountController(UserManager<AppUser> userManager,
            SignInManager<AppUser> signInManager,
            ITokenService tokenService, IUnitOfWork unitOfWork,
            ILogger<AccountController> logger,
            IMapper mapper, IAccountService accountService, IEmailService emailService, IHostEnvironment environment)
        {
            _userManager = userManager;
            _signInManager = signInManager;
            _tokenService = tokenService;
            _unitOfWork = unitOfWork;
            _logger = logger;
            _mapper = mapper;
            _accountService = accountService;
            _emailService = emailService;
            _environment = environment;
        }

        /// <summary>
        /// Update a user's password
        /// </summary>
        /// <param name="resetPasswordDto"></param>
        /// <returns></returns>
        [HttpPost("reset-password")]
        public async Task<ActionResult> UpdatePassword(ResetPasswordDto resetPasswordDto)
        {
            _logger.LogInformation("{UserName} is changing {ResetUser}'s password", User.GetUsername(), resetPasswordDto.UserName);
            var user = await _userManager.Users.SingleAsync(x => x.UserName == resetPasswordDto.UserName);

            if (resetPasswordDto.UserName != User.GetUsername() && !(User.IsInRole(PolicyConstants.AdminRole) || User.IsInRole(PolicyConstants.ChangePasswordRole)))
                return Unauthorized("You are not permitted to this operation.");

            var errors = await _accountService.ChangeUserPassword(user, resetPasswordDto.Password);
            if (errors.Any())
            {
                return BadRequest(errors);
            }

            _logger.LogInformation("{User}'s Password has been reset", resetPasswordDto.UserName);
            return Ok();
        }

        /// <summary>
        /// Register the first user (admin) on the server. Will not do anything if an admin is already confirmed
        /// </summary>
        /// <param name="registerDto"></param>
        /// <returns></returns>
        [HttpPost("register")]
        public async Task<ActionResult<UserDto>> RegisterFirstUser(RegisterDto registerDto)
        {
            var admins = await _userManager.GetUsersInRoleAsync("Admin");
            if (admins.Count > 0) return BadRequest("Not allowed");

            try
            {
                var usernameValidation = await _accountService.ValidateUsername(registerDto.Username);
                if (usernameValidation.Any())
                {
                    return BadRequest(usernameValidation);
                }

                var user = new AppUser()
                {
                    UserName = registerDto.Username,
                    Email = registerDto.Email,
                    UserPreferences = new AppUserPreferences
                    {
                        Theme = await _unitOfWork.SiteThemeRepository.GetDefaultTheme()
                    },
                    ApiKey = HashUtil.ApiKey()
                };

                var result = await _userManager.CreateAsync(user, registerDto.Password);
                if (!result.Succeeded) return BadRequest(result.Errors);

                var token = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                if (string.IsNullOrEmpty(token)) return BadRequest("There was an issue generating a confirmation token.");
                if (!await ConfirmEmailToken(token, user)) return BadRequest($"There was an issue validating your email: {token}");


                var roleResult = await _userManager.AddToRoleAsync(user, PolicyConstants.AdminRole);
                if (!roleResult.Succeeded) return BadRequest(result.Errors);

                return new UserDto
                {
                    Username = user.UserName,
                    Email = user.Email,
                    Token = await _tokenService.CreateToken(user),
                    RefreshToken = await _tokenService.CreateRefreshToken(user),
                    ApiKey = user.ApiKey,
                    Preferences = _mapper.Map<UserPreferencesDto>(user.UserPreferences)
                };
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Something went wrong when registering user");
                await _unitOfWork.RollbackAsync();
            }

            return BadRequest("Something went wrong when registering user");
        }


        /// <summary>
        /// Perform a login. Will send JWT Token of the logged in user back.
        /// </summary>
        /// <param name="loginDto"></param>
        /// <returns></returns>
        [HttpPost("login")]
        public async Task<ActionResult<UserDto>> Login(LoginDto loginDto)
        {
            var user = await _userManager.Users
                .Include(u => u.UserPreferences)
                .SingleOrDefaultAsync(x => x.NormalizedUserName == loginDto.Username.ToUpper());

            if (user == null) return Unauthorized("Invalid username");

            // Check if the user has an email, if not, inform them so they can migrate
            var validPassword = await _signInManager.UserManager.CheckPasswordAsync(user, loginDto.Password);
            if (string.IsNullOrEmpty(user.Email) && !user.EmailConfirmed && validPassword)
            {
                _logger.LogCritical("User {UserName} does not have an email. Providing a one time migration", user.UserName);
                return Unauthorized(
                    "You are missing an email on your account. Please wait while we migrate your account.");
            }

            if (!validPassword)
            {
                return Unauthorized("Your credentials are not correct");
            }

            var result = await _signInManager
                .CheckPasswordSignInAsync(user, loginDto.Password, false);

            if (!result.Succeeded)
            {
                return Unauthorized(result.IsNotAllowed ? "You must confirm your email first" : "Your credentials are not correct.");
            }

            // Update LastActive on account
            user.LastActive = DateTime.Now;
            user.UserPreferences ??= new AppUserPreferences
            {
                Theme = await _unitOfWork.SiteThemeRepository.GetDefaultTheme()
            };

            _unitOfWork.UserRepository.Update(user);
            await _unitOfWork.CommitAsync();

            _logger.LogInformation("{UserName} logged in at {Time}", user.UserName, user.LastActive);

            var dto = _mapper.Map<UserDto>(user);
            dto.Token = await _tokenService.CreateToken(user);
            dto.RefreshToken = await _tokenService.CreateRefreshToken(user);
            var pref = await _unitOfWork.UserRepository.GetPreferencesAsync(user.UserName);
            pref.Theme ??= await _unitOfWork.SiteThemeRepository.GetDefaultTheme();
            dto.Preferences = _mapper.Map<UserPreferencesDto>(pref);
            return dto;
        }

        [HttpPost("refresh-token")]
        public async Task<ActionResult<TokenRequestDto>> RefreshToken([FromBody] TokenRequestDto tokenRequestDto)
        {
            var token = await _tokenService.ValidateRefreshToken(tokenRequestDto);
            if (token == null)
            {
                return Unauthorized(new { message = "Invalid token" });
            }

            return Ok(token);
        }

        /// <summary>
        /// Get All Roles back. See <see cref="PolicyConstants"/>
        /// </summary>
        /// <returns></returns>
        [HttpGet("roles")]
        public ActionResult<IList<string>> GetRoles()
        {
            return typeof(PolicyConstants)
                .GetFields(BindingFlags.Public | BindingFlags.Static)
                .Where(f => f.FieldType == typeof(string))
                .ToDictionary(f => f.Name,
                    f => (string) f.GetValue(null)).Values.ToList();
        }


        /// <summary>
        /// Resets the API Key assigned with a user
        /// </summary>
        /// <returns></returns>
        [HttpPost("reset-api-key")]
        public async Task<ActionResult<string>> ResetApiKey()
        {
            var user = await _unitOfWork.UserRepository.GetUserByUsernameAsync(User.GetUsername());

            user.ApiKey = HashUtil.ApiKey();

            if (_unitOfWork.HasChanges() && await _unitOfWork.CommitAsync())
            {
                return Ok(user.ApiKey);
            }

            await _unitOfWork.RollbackAsync();
            return BadRequest("Something went wrong, unable to reset key");

        }

        /// <summary>
        /// Update the user account. This can only affect Username, Email (will require confirming), Roles, and Library access.
        /// </summary>
        /// <param name="dto"></param>
        /// <returns></returns>
        [Authorize(Policy = "RequireAdminRole")]
        [HttpPost("update")]
        public async Task<ActionResult> UpdateAccount(UpdateUserDto dto)
        {
            var adminUser = await _unitOfWork.UserRepository.GetUserByUsernameAsync(User.GetUsername());
            if (!await _unitOfWork.UserRepository.IsUserAdminAsync(adminUser)) return Unauthorized("You do not have permission");

            var user = await _unitOfWork.UserRepository.GetUserByIdAsync(dto.UserId);
            if (user == null) return BadRequest("User does not exist");

            // Check if username is changing
            if (!user.UserName.Equals(dto.Username))
            {
                // Validate username change
                var errors = await _accountService.ValidateUsername(dto.Username);
                if (errors.Any()) return BadRequest("Username already taken");
                user.UserName = dto.Username;
                _unitOfWork.UserRepository.Update(user);
            }

            if (!user.Email.Equals(dto.Email))
            {
                // Validate username change
                var errors = await _accountService.ValidateEmail(dto.Email);
                if (errors.Any()) return BadRequest("Email already registered");
                // NOTE: This needs to be handled differently, like save it in a temp variable in DB until email is validated. For now, I wont allow it
            }

            // Update roles
            var existingRoles = await _userManager.GetRolesAsync(user);
            var hasAdminRole = dto.Roles.Contains(PolicyConstants.AdminRole);
            if (!hasAdminRole)
            {
                dto.Roles.Add(PolicyConstants.PlebRole);
            }
            if (existingRoles.Except(dto.Roles).Any() || dto.Roles.Except(existingRoles).Any())
            {
                var roles = dto.Roles;

                var roleResult = await _userManager.RemoveFromRolesAsync(user, existingRoles);
                if (!roleResult.Succeeded) return BadRequest(roleResult.Errors);
                roleResult = await _userManager.AddToRolesAsync(user, roles);
                if (!roleResult.Succeeded) return BadRequest(roleResult.Errors);
            }


            var allLibraries = (await _unitOfWork.LibraryRepository.GetLibrariesAsync()).ToList();
            List<Library> libraries;
            if (hasAdminRole)
            {
                _logger.LogInformation("{UserName} is being registered as admin. Granting access to all libraries",
                    user.UserName);
                libraries = allLibraries;
            }
            else
            {
                // Remove user from all libraries
                foreach (var lib in allLibraries)
                {
                    lib.AppUsers ??= new List<AppUser>();
                    lib.AppUsers.Remove(user);
                }

                libraries = (await _unitOfWork.LibraryRepository.GetLibraryForIdsAsync(dto.Libraries)).ToList();
            }

            foreach (var lib in libraries)
            {
                lib.AppUsers ??= new List<AppUser>();
                lib.AppUsers.Add(user);
            }

            if (!_unitOfWork.HasChanges()) return Ok();
            if (await _unitOfWork.CommitAsync())
            {
                return Ok();
            }

            await _unitOfWork.RollbackAsync();
            return BadRequest("There was an exception when updating the user");
        }



        [Authorize(Policy = "RequireAdminRole")]
        [HttpPost("invite")]
        public async Task<ActionResult<string>> InviteUser(InviteUserDto dto)
        {
            var adminUser = await _unitOfWork.UserRepository.GetUserByUsernameAsync(User.GetUsername());
            if (adminUser == null) return Unauthorized("You need to login");
            _logger.LogInformation("{User} is inviting {Email} to the server", adminUser.UserName, dto.Email);

            // Check if there is an existing invite
            var emailValidationErrors = await _accountService.ValidateEmail(dto.Email);
            if (emailValidationErrors.Any())
            {
                var invitedUser = await _unitOfWork.UserRepository.GetUserByEmailAsync(dto.Email);
                if (await _userManager.IsEmailConfirmedAsync(invitedUser))
                    return BadRequest($"User is already registered as {invitedUser.UserName}");
                return BadRequest("User is already invited under this email and has yet to accepted invite.");
            }

            // Create a new user
            var user = new AppUser()
            {
                UserName = dto.Email,
                Email = dto.Email,
                ApiKey = HashUtil.ApiKey(),
                UserPreferences = new AppUserPreferences
                {
                    Theme = await _unitOfWork.SiteThemeRepository.GetDefaultTheme()
                }
            };

            try
            {
                var result = await _userManager.CreateAsync(user, AccountService.DefaultPassword);
                if (!result.Succeeded) return BadRequest(result.Errors);

                // Assign Roles
                var roles = dto.Roles;
                var hasAdminRole = dto.Roles.Contains(PolicyConstants.AdminRole);
                if (!hasAdminRole)
                {
                    roles.Add(PolicyConstants.PlebRole);
                }

                foreach (var role in roles)
                {
                    if (!PolicyConstants.ValidRoles.Contains(role)) continue;
                    var roleResult = await _userManager.AddToRoleAsync(user, role);
                    if (!roleResult.Succeeded)
                        return
                            BadRequest(roleResult.Errors);
                }

                // Grant access to libraries
                List<Library> libraries;
                if (hasAdminRole)
                {
                    _logger.LogInformation("{UserName} is being registered as admin. Granting access to all libraries",
                        user.UserName);
                    libraries = (await _unitOfWork.LibraryRepository.GetLibrariesAsync()).ToList();
                }
                else
                {
                    libraries = (await _unitOfWork.LibraryRepository.GetLibraryForIdsAsync(dto.Libraries)).ToList();
                }

                foreach (var lib in libraries)
                {
                    lib.AppUsers ??= new List<AppUser>();
                    lib.AppUsers.Add(user);
                }

                await _unitOfWork.CommitAsync();


                var token = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                if (string.IsNullOrEmpty(token)) return BadRequest("There was an issue sending email");

                var emailLink = GenerateEmailLink(token, "confirm-email", dto.Email);
                _logger.LogCritical("[Invite User]: Email Link for {UserName}: {Link}", user.UserName, emailLink);
                if (dto.SendEmail)
                {
                    await _emailService.SendConfirmationEmail(new ConfirmationEmailDto()
                    {
                        EmailAddress = dto.Email,
                        InvitingUser = adminUser.UserName,
                        ServerConfirmationLink = emailLink
                    });
                }
                return Ok(emailLink);
            }
            catch (Exception)
            {
                _unitOfWork.UserRepository.Delete(user);
                await _unitOfWork.CommitAsync();
            }

            return BadRequest("There was an error setting up your account. Please check the logs");
        }

        [HttpPost("confirm-email")]
        public async Task<ActionResult<UserDto>> ConfirmEmail(ConfirmEmailDto dto)
        {
            var user = await _unitOfWork.UserRepository.GetUserByEmailAsync(dto.Email);

            // Validate Password and Username
            var validationErrors = new List<ApiException>();
            validationErrors.AddRange(await _accountService.ValidateUsername(dto.Username));
            validationErrors.AddRange(await _accountService.ValidatePassword(user, dto.Password));

            if (validationErrors.Any())
            {
                return BadRequest(validationErrors);
            }


            if (!await ConfirmEmailToken(dto.Token, user)) return BadRequest("Invalid Email Token");

            user.UserName = dto.Username;
            var errors = await _accountService.ChangeUserPassword(user, dto.Password);
            if (errors.Any())
            {
                return BadRequest(errors);
            }
            await _unitOfWork.CommitAsync();


            user = await _unitOfWork.UserRepository.GetUserByUsernameAsync(user.UserName,
                AppUserIncludes.UserPreferences);

            // Perform Login code
            return new UserDto
            {
                Username = user.UserName,
                Email = user.Email,
                Token = await _tokenService.CreateToken(user),
                RefreshToken = await _tokenService.CreateRefreshToken(user),
                ApiKey = user.ApiKey,
                Preferences = _mapper.Map<UserPreferencesDto>(user.UserPreferences)
            };
        }

        [AllowAnonymous]
        [HttpPost("confirm-password-reset")]
        public async Task<ActionResult<string>> ConfirmForgotPassword(ConfirmPasswordResetDto dto)
        {
            var user = await _unitOfWork.UserRepository.GetUserByEmailAsync(dto.Email);
            if (user == null)
            {
                return BadRequest("Invalid Details");
            }

            var result = await _userManager.VerifyUserTokenAsync(user, TokenOptions.DefaultProvider, "ResetPassword", dto.Token);
            if (!result) return BadRequest("Unable to reset password, your email token is not correct.");

            var errors = await _accountService.ChangeUserPassword(user, dto.Password);
            return errors.Any() ? BadRequest(errors) : Ok("Password updated");
        }


        /// <summary>
        /// Will send user a link to update their password to their email or prompt them if not accessible
        /// </summary>
        /// <param name="email"></param>
        /// <returns></returns>
        [AllowAnonymous]
        [HttpPost("forgot-password")]
        public async Task<ActionResult<string>> ForgotPassword([FromQuery] string email)
        {
            var user = await _unitOfWork.UserRepository.GetUserByEmailAsync(email);
            if (user == null)
            {
                _logger.LogError("There are no users with email: {Email} but user is requesting password reset", email);
                return Ok("An email will be sent to the email if it exists in our database");
            }

            var emailLink = GenerateEmailLink(await _userManager.GeneratePasswordResetTokenAsync(user), "confirm-reset-password", user.Email);
            _logger.LogCritical("[Forgot Password]: Email Link for {UserName}: {Link}", user.UserName, emailLink);
            var host = _environment.IsDevelopment() ? "localhost:4200" : Request.Host.ToString();
            if (await _emailService.CheckIfAccessible(host))
            {
                await _emailService.SendPasswordResetEmail(new PasswordResetEmailDto()
                {
                    EmailAddress = user.Email,
                    ServerConfirmationLink = emailLink,
                    InstallId = (await _unitOfWork.SettingsRepository.GetSettingAsync(ServerSettingKey.InstallId)).Value
                });
                return Ok("Email sent");
            }

            return Ok("Your server is not accessible. The Link to reset your password is in the logs.");
        }

        [AllowAnonymous]
        [HttpPost("confirm-migration-email")]
        public async Task<ActionResult<UserDto>> ConfirmMigrationEmail(ConfirmMigrationEmailDto dto)
        {
            var user = await _unitOfWork.UserRepository.GetUserByEmailAsync(dto.Email);
            if (user == null) return BadRequest("This email is not on system");

            if (!await ConfirmEmailToken(dto.Token, user)) return BadRequest("Invalid Email Token");

            await _unitOfWork.CommitAsync();

            user = await _unitOfWork.UserRepository.GetUserByUsernameAsync(user.UserName,
                AppUserIncludes.UserPreferences);

            // Perform Login code
            return new UserDto
            {
                Username = user.UserName,
                Email = user.Email,
                Token = await _tokenService.CreateToken(user),
                RefreshToken = await _tokenService.CreateRefreshToken(user),
                ApiKey = user.ApiKey,
                Preferences = _mapper.Map<UserPreferencesDto>(user.UserPreferences)
            };
        }

        [HttpPost("resend-confirmation-email")]
        public async Task<ActionResult<string>> ResendConfirmationSendEmail([FromQuery] int userId)
        {
            var user = await _unitOfWork.UserRepository.GetUserByIdAsync(userId);
            if (user == null) return BadRequest("User does not exist");

            if (string.IsNullOrEmpty(user.Email))
                return BadRequest(
                    "This user needs to migrate. Have them log out and login to trigger a migration flow");
            if (user.EmailConfirmed) return BadRequest("User already confirmed");

            var emailLink = GenerateEmailLink(await _userManager.GenerateEmailConfirmationTokenAsync(user), "confirm-email", user.Email);
            _logger.LogCritical("[Email Migration]: Email Link: {Link}", emailLink);
            await _emailService.SendMigrationEmail(new EmailMigrationDto()
            {
                EmailAddress = user.Email,
                Username = user.UserName,
                ServerConfirmationLink = emailLink,
                InstallId = (await _unitOfWork.SettingsRepository.GetSettingAsync(ServerSettingKey.InstallId)).Value
            });


            return Ok(emailLink);
        }

        private string GenerateEmailLink(string token, string routePart, string email)
        {
            var host = _environment.IsDevelopment() ? "localhost:4200" : Request.Host.ToString();
            var emailLink =
                $"{Request.Scheme}://{host}{Request.PathBase}/registration/{routePart}?token={HttpUtility.UrlEncode(token)}&email={HttpUtility.UrlEncode(email)}";
            return emailLink;
        }

        /// <summary>
        /// This is similar to invite. Essentially we authenticate the user's password then go through invite email flow
        /// </summary>
        /// <param name="dto"></param>
        /// <returns></returns>
        [AllowAnonymous]
        [HttpPost("migrate-email")]
        public async Task<ActionResult<string>> MigrateEmail(MigrateUserEmailDto dto)
        {
            // Check if there is an existing invite
            var emailValidationErrors = await _accountService.ValidateEmail(dto.Email);
            if (emailValidationErrors.Any())
            {
                var invitedUser = await _unitOfWork.UserRepository.GetUserByEmailAsync(dto.Email);
                if (await _userManager.IsEmailConfirmedAsync(invitedUser))
                    return BadRequest($"User is already registered as {invitedUser.UserName}");

                _logger.LogInformation("A user is attempting to login, but hasn't accepted email invite");
                return BadRequest("User is already invited under this email and has yet to accepted invite.");
            }


            var user = await _userManager.Users
                .Include(u => u.UserPreferences)
                .SingleOrDefaultAsync(x => x.NormalizedUserName == dto.Username.ToUpper());
            if (user == null) return BadRequest("Invalid username");

            var validPassword = await _signInManager.UserManager.CheckPasswordAsync(user, dto.Password);
            if (!validPassword) return BadRequest("Your credentials are not correct");

            try
            {
                var token = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                //if (string.IsNullOrEmpty(token)) return BadRequest("There was an issue sending email");
                user.Email = dto.Email;
                if (!await ConfirmEmailToken(token, user)) return BadRequest("There was a critical error during migration");
                _unitOfWork.UserRepository.Update(user);

                await _unitOfWork.CommitAsync();

                //var emailLink = GenerateEmailLink(await _userManager.GenerateEmailConfirmationTokenAsync(user), "confirm-migration-email", user.Email);
                // _logger.LogCritical("[Email Migration]: Email Link for {UserName}: {Link}", dto.Username, emailLink);
                // // Always send an email, even if the user can't click it just to get them conformable with the system
                // await _emailService.SendMigrationEmail(new EmailMigrationDto()
                // {
                //     EmailAddress = dto.Email,
                //     Username = user.UserName,
                //     ServerConfirmationLink = emailLink
                // });
                return Ok();
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "There was an issue during email migration. Contact support");
                _unitOfWork.UserRepository.Delete(user);
                await _unitOfWork.CommitAsync();
            }

            return BadRequest("There was an error setting up your account. Please check the logs");
        }

        private async Task<bool> ConfirmEmailToken(string token, AppUser user)
        {
            var result = await _userManager.ConfirmEmailAsync(user, token);
            if (!result.Succeeded)
            {
                _logger.LogCritical("Email validation failed");
                if (result.Errors.Any())
                {
                    foreach (var error in result.Errors)
                    {
                        _logger.LogCritical("Email validation error: {Message}", error.Description);
                    }
                }

                return false;
            }

            return true;
        }
    }
}