using System.Security.Claims;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Identity;
using PlotLine.Data;
using PlotLine.Models;
using PlotLine.ViewModels;

namespace PlotLine.Services;

public sealed class PasswordService : IPasswordService
{
    private readonly PasswordHasher<AppUser> _passwordHasher = new();

    public string HashPassword(string password)
    {
        return _passwordHasher.HashPassword(new AppUser(), password);
    }

    public bool VerifyPassword(string password, string passwordHash)
    {
        var result = _passwordHasher.VerifyHashedPassword(new AppUser(), passwordHash, password);
        return result is PasswordVerificationResult.Success or PasswordVerificationResult.SuccessRehashNeeded;
    }
}

public sealed class CurrentUserService(IHttpContextAccessor httpContextAccessor) : ICurrentUserService
{
    private ClaimsPrincipal? User => httpContextAccessor.HttpContext?.User;

    public int? UserId
    {
        get
        {
            var value = User?.FindFirstValue(ClaimTypes.NameIdentifier);
            return int.TryParse(value, out var userId) ? userId : null;
        }
    }

    public string? Email => User?.FindFirstValue(ClaimTypes.Email);

    public string? DisplayName => User?.FindFirstValue(ClaimTypes.Name);

    public bool IsAuthenticated => User?.Identity?.IsAuthenticated == true;
}

public sealed class AuthService(
    IUserRepository users,
    IAuthenticationRepository authentication,
    IPasswordService passwords,
    IHttpContextAccessor httpContextAccessor,
    ILogger<AuthService> logger) : IAuthService
{
    public async Task<RegistrationResult> RegisterAsync(RegisterViewModel model)
    {
        var email = Clean(model.Email);
        var displayName = Clean(model.DisplayName);

        var existingUser = await users.GetByEmailAsync(email);
        if (existingUser is not null)
        {
            return RegistrationResult.Failed("An account already exists for that email address.");
        }

        var passwordHash = passwords.HashPassword(model.Password);
        var created = await users.CreateAsync(email, displayName, passwordHash, emailConfirmed: true);
        logger.LogInformation("User {UserID} registered with email confirmation temporarily enabled for Phase 4B.", created.UserID);

        return RegistrationResult.Succeeded(created.UserID);
    }

    public async Task<AuthenticationResult> LoginAsync(LoginViewModel model)
    {
        var email = Clean(model.Email);
        var user = await users.GetByEmailAsync(email);
        if (user is null)
        {
            await InsertLoginAuditAsync(null, email, false, "User not found");
            return AuthenticationResult.Failed("The email address or password was not recognised.");
        }

        if (!passwords.VerifyPassword(model.Password, user.PasswordHash))
        {
            await users.UpdateFailedLoginAsync(user.UserID, lockoutEndUtc: null);
            await InsertLoginAuditAsync(user.UserID, email, false, "Invalid password");
            return AuthenticationResult.Failed("The email address or password was not recognised.");
        }

        var updatedUser = await users.UpdateLoginSuccessAsync(user.UserID) ?? user;
        await InsertLoginAuditAsync(user.UserID, email, true, "Login successful");
        await SignInAsync(updatedUser, model.RememberMe);

        return AuthenticationResult.Succeeded();
    }

    public async Task LogoutAsync()
    {
        var httpContext = httpContextAccessor.HttpContext;
        if (httpContext is not null)
        {
            await httpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
        }
    }

    public Task<AuthenticationResult> CompleteTwoFactorLoginAsync(TwoFactorViewModel model)
        => throw new NotImplementedException("Two-factor login will be implemented in a later phase.");

    public Task<AuthenticationResult> VerifyEmailAsync(Guid token)
        => throw new NotImplementedException("Email verification will be implemented in a later phase.");

    public Task<AuthenticationResult> ForgotPasswordAsync(ForgotPasswordViewModel model)
        => throw new NotImplementedException("Forgotten password handling will be implemented in a later phase.");

    public Task<AuthenticationResult> ResetPasswordAsync(ResetPasswordViewModel model)
        => throw new NotImplementedException("Password reset handling will be implemented in a later phase.");

    public Task<AuthenticationResult> ChangePasswordAsync(ChangePasswordViewModel model)
        => throw new NotImplementedException("Password changes will be implemented in a later phase.");

    public Task<AuthenticationResult> EnableTwoFactorAsync(int userId)
        => throw new NotImplementedException("Two-factor setup will be implemented in a later phase.");

    public Task<AuthenticationResult> DisableTwoFactorAsync(int userId)
        => throw new NotImplementedException("Two-factor setup will be implemented in a later phase.");

    public Task<IReadOnlyList<string>> GenerateRecoveryCodesAsync(int userId)
        => throw new NotImplementedException("Recovery codes will be implemented in a later phase.");

    private async Task SignInAsync(AppUser user, bool rememberMe)
    {
        var claims = new List<Claim>
        {
            new(ClaimTypes.NameIdentifier, user.UserID.ToString()),
            new(ClaimTypes.Name, user.DisplayName),
            new(ClaimTypes.Email, user.Email)
        };

        var identity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);
        var principal = new ClaimsPrincipal(identity);
        var properties = new AuthenticationProperties
        {
            IsPersistent = rememberMe,
            AllowRefresh = true
        };

        var httpContext = httpContextAccessor.HttpContext ?? throw new InvalidOperationException("No active HTTP context is available.");
        await httpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal, properties);
    }

    private async Task InsertLoginAuditAsync(int? userId, string emailAttempted, bool wasSuccessful, string reason)
    {
        var httpContext = httpContextAccessor.HttpContext;
        await authentication.InsertLoginAuditAsync(new UserLoginAudit
        {
            UserID = userId,
            EmailAttempted = emailAttempted,
            IpAddress = httpContext?.Connection.RemoteIpAddress?.ToString(),
            UserAgent = httpContext?.Request.Headers.UserAgent.ToString(),
            WasSuccessful = wasSuccessful,
            Reason = reason
        });
    }

    private static string Clean(string value) => value.Trim();
}