using Data.SeaHavenIndustries;
using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Configuration;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;

namespace SeaHaven.Services.Implementation
{
    public class AuthenticationService : IAuthenticationService
    {
        private readonly UserManager<ApplicationUser> _userManager;
        private readonly JwtOptions _jwtOptions;
        private readonly IUserDataService _userDataService;
        private readonly IForgetPasswordDataService _forgetPasswordDataService;
        private readonly IPasswordResetEmailQueue _resetEmails;
        private readonly IPasswordResetThrottle _resetThrottle;
        private readonly TimeProvider _timeProvider;
        private byte[]? _resetCodeKey;

        public static readonly TimeSpan ResetCodeLifetime = TimeSpan.FromMinutes(15);
        public const int MaxCodeAttempts = 5;

        /// <summary>Longest address stored for a reset request; Identity caps emails at 256.</summary>
        public const int MaxResetEmailLength = 256;

        public AuthenticationService(
            UserManager<ApplicationUser> userManager,
            IOptions<JwtOptions> jwtOptions,
            IUserDataService userDataService,
            IForgetPasswordDataService forgetPasswordDataService,
            IPasswordResetEmailQueue resetEmails,
            IPasswordResetThrottle resetThrottle,
            TimeProvider timeProvider)
        {
            _userManager = userManager;
            _jwtOptions = jwtOptions.Value;
            _userDataService = userDataService;
            _forgetPasswordDataService = forgetPasswordDataService;
            _resetEmails = resetEmails;
            _resetThrottle = resetThrottle;
            _timeProvider = timeProvider;
        }

        private byte[] ResetCodeKey => _resetCodeKey ??= PasswordResetCodeSecrets.DeriveKey(_jwtOptions.Secret);

        public async Task<LoginResultDTO?> LoginAsync(string? username, string? password, CancellationToken cancellationToken)
        {
            var user = await _userManager.FindByNameAsync(username ?? "");
            if (user != null && user.IsDeleted != true && await _userManager.CheckPasswordAsync(user, password ?? ""))
            {
                var userRoles = await _userManager.GetRolesAsync(user);
                var authClaims = new List<Claim>
                {
                    new Claim(ClaimTypes.Name, user.UserName ?? ""),
                    new Claim(ClaimTypes.NameIdentifier, user.Id),
                    new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString())
                };
                foreach (var userRole in userRoles)
                {
                    authClaims.Add(new Claim(ClaimTypes.Role, userRole));
                }
                if (user.AccountId.HasValue)
                {
                    authClaims.Add(new Claim(
                        SeaHavenClaimTypes.AccountId,
                        user.AccountId.Value.ToString()));
                }
                else if (userRoles.Contains("Admin"))
                {
                    // Explicit signed org-wide elevation — never elevate via absence of account_id.
                    authClaims.Add(new Claim(
                        SeaHavenClaimTypes.OrgScope,
                        SeaHavenClaimTypes.OrgScopeAll));
                }
                var token = GetToken(authClaims);
                return new LoginResultDTO
                {
                    Token = new JwtSecurityTokenHandler().WriteToken(token),
                    Expiration = token.ValidTo,
                    Email = user.Email,
                    UserRole = userRoles.FirstOrDefault(),
                    PhoneNumber = user.PhoneNumber,
                    Fullname = user.FirstName + " " + user.LastName,
                    Id = user.Id
                };
            }

            return null;
        }

        public async Task<ChangePasswordResultDTO> ChangePasswordAsync(string userId, string? currentPassword, string? newPassword, CancellationToken cancellationToken)
        {
            cancellationToken.ThrowIfCancellationRequested();
            var user = await _userManager.FindByIdAsync(userId);
            if (user == null || user.IsDeleted == true)
                return ChangePasswordResult(ChangePasswordStatus.CurrentPasswordIncorrect);

            // The current password is verified before the new one is evaluated, so a
            // caller without it learns nothing about the policy outcome.
            if (!await _userManager.CheckPasswordAsync(user, currentPassword ?? ""))
                return ChangePasswordResult(ChangePasswordStatus.CurrentPasswordIncorrect);

            var result = await _userManager.ChangePasswordAsync(user, currentPassword ?? "", newPassword ?? "");
            if (result.Succeeded)
                return ChangePasswordResult(ChangePasswordStatus.Succeeded);

            return ChangePasswordResult(IdentityPasswordPolicy.IsPolicyRejection(result)
                ? ChangePasswordStatus.PasswordRejected
                : ChangePasswordStatus.Failed);
        }

        private static ChangePasswordResultDTO ChangePasswordResult(ChangePasswordStatus status) =>
            new() { Status = status };

        public async Task<UserProfileDTO?> UpdateProfileAsync(string userId, UpdateProfileRequestDTO dto, CancellationToken cancellationToken)
        {
            var exists = await _userDataService.UpdateProfileAsync(
                userId,
                dto.Name,
                dto.Email,
                dto.Contact,
                cancellationToken);
            if (!exists)
                return null;

            var updated = await _userDataService.GetProfileAsync(userId, cancellationToken);
            if (updated == null) return null;
            return new UserProfileDTO
            {
                FirstName = updated.FirstName,
                Email = updated.Email,
                Contact = updated.Contact
            };
        }

        public async Task ForgetPasswordAsync(string? email, CancellationToken cancellationToken)
        {
            // Registered and unregistered addresses do the same work: one user lookup,
            // one code generated and hashed, and the same replace in the database. An
            // unregistered address gets a row no code can match. The email itself is
            // queued, so the response never waits on the mail provider.
            var requested = email?.Trim() ?? string.Empty;
            if (requested.Length == 0 || requested.Length > MaxResetEmailLength)
                return;

            var user = await _userDataService.GetByEmailNormalizedAsync(requested, cancellationToken);
            var nowUtc = _timeProvider.GetUtcNow().UtcDateTime;
            if (!_resetThrottle.TryAcceptCodeRequest(requested))
            {
                // Over the per-email limit: keep the current code and send nothing.
                await _forgetPasswordDataService.PurgeExpiredAsync(nowUtc, cancellationToken);
                return;
            }

            var code = PasswordResetCodeSecrets.NewCode();
            var salt = PasswordResetCodeSecrets.NewSalt();
            var hash = PasswordResetCodeSecrets.Hash(ResetCodeKey, salt, code);
            var active = user != null && user.IsDeleted != true && !string.IsNullOrWhiteSpace(user.Email);

            var queued = false;
            if (active)
            {
                var body = $"Your Password Reset Code is: {code}. It expires in {(int)ResetCodeLifetime.TotalMinutes} minutes.";
                queued = _resetEmails.TryEnqueue(user!.Email!, "Forget Password Request.", body);

                // A code that cannot be emailed is stored unmatchable and the request is not counted.
                if (!queued)
                    _resetThrottle.ReleaseCodeRequest(requested);
            }

            await _forgetPasswordDataService.ReplaceCodeAsync(
                active ? user!.Email! : requested,
                active ? user!.Id : string.Empty,
                queued ? hash : PasswordResetCodeSecrets.NewUnmatchableHash(),
                salt,
                nowUtc.Add(ResetCodeLifetime),
                nowUtc,
                cancellationToken);
        }

        public async Task<bool> VerifyCodeAsync(string? email, string? code, CancellationToken cancellationToken)
        {
            var pending = await CheckCodeAsync(email, code, cancellationToken);
            if (pending == null)
                return false;

            // Verifying is a preview step; a correct code keeps all of its attempts.
            await _forgetPasswordDataService.RefundAttemptAsync(pending.Id, cancellationToken);
            return true;
        }

        public async Task<bool> ResetPasswordAsync(string? email, string? code, string? password, CancellationToken cancellationToken)
        {
            if (string.IsNullOrWhiteSpace(password))
                return false;

            var pending = await CheckCodeAsync(email, code, cancellationToken);
            if (pending == null)
                return false;

            var user = await _userManager.FindByIdAsync(pending.UserId);
            if (user == null || user.IsDeleted == true)
            {
                await _forgetPasswordDataService.RemoveByEmailAsync(pending.Email, cancellationToken);
                return false;
            }

            var token = await _userManager.GeneratePasswordResetTokenAsync(user);
            var result = await _userManager.ResetPasswordAsync(user, token, password);
            if (!result.Succeeded)
            {
                // The code was right and the new password was rejected: the user can
                // try another password without spending an attempt.
                await _forgetPasswordDataService.RefundAttemptAsync(pending.Id, cancellationToken);
                return false;
            }

            await _forgetPasswordDataService.RemoveByEmailAsync(pending.Email, cancellationToken);
            return true;
        }

        /// <summary>
        /// Returns the pending code record when <paramref name="code"/> matches the one
        /// issued to <paramref name="email"/>. Every check consumes an attempt before
        /// comparing; a check that uses the last attempt without matching deletes the code.
        /// </summary>
        private async Task<ForgetPasswordCode?> CheckCodeAsync(string? email, string? code, CancellationToken cancellationToken)
        {
            if (string.IsNullOrWhiteSpace(email) || string.IsNullOrWhiteSpace(code))
                return null;

            // The per-account budget spans every code the account is sent, so asking for
            // new codes does not buy more guesses. A slot is reserved before comparing and
            // given back when the code matches or there is no live code to guess at.
            if (!_resetThrottle.TryReserveCheck(email))
                return null;

            var pending = await _forgetPasswordDataService.GetByEmailAsync(email, cancellationToken);
            if (pending == null)
            {
                _resetThrottle.ReleaseCheck(email);
                return null;
            }

            var nowUtc = _timeProvider.GetUtcNow().UtcDateTime;
            if (!await _forgetPasswordDataService.TryConsumeAttemptAsync(pending.Id, MaxCodeAttempts, nowUtc, cancellationToken))
            {
                // Expired or out of attempts: nothing was compared, so no guess is counted.
                _resetThrottle.ReleaseCheck(email);
                await _forgetPasswordDataService.RemoveByEmailAsync(pending.Email, cancellationToken);
                return null;
            }

            if (PasswordResetCodeSecrets.Matches(ResetCodeKey, pending.CodeSalt, code, pending.CodeHash))
            {
                _resetThrottle.ReleaseCheck(email);
                return pending;
            }

            if (pending.FailedAttempts + 1 >= MaxCodeAttempts)
                await _forgetPasswordDataService.RemoveByEmailAsync(pending.Email, cancellationToken);
            return null;
        }

        private JwtSecurityToken GetToken(List<Claim> authClaims)
        {
            var authSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_jwtOptions.Secret));
            var token = new JwtSecurityToken(
                issuer: _jwtOptions.ValidIssuer,
                audience: _jwtOptions.ValidAudience,
                expires: DateTime.Now.AddDays(10),
                claims: authClaims,
                signingCredentials: new SigningCredentials(authSigningKey, SecurityAlgorithms.HmacSha256)
                );
            return token;
        }
    }
}