// Program.cs
builder.Services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
    .AddCookie(options =>
    {
        options.LoginPath = "/Account/Login";
        options.AccessDeniedPath = "/Account/AccessDenied";
    });

builder.Services.AddCascadingAuthenticationState();
builder.Services.AddAuthorization();

// Client Program.cs (WASM)
builder.Services.AddOidcAuthentication(options =>
{
    options.ProviderOptions.Authority = "https://login.example.com";
    options.ProviderOptions.ClientId = "blazor-wasm-client";
    options.ProviderOptions.ResponseType = "code";
    options.ProviderOptions.DefaultScopes.Add("api");
});

// Attach tokens to API calls using BaseAddressAuthorizationMessageHandler
// (auto-attaches tokens for requests to the app's base address)
builder.Services.AddHttpClient("API", client =>
    client.BaseAddress = new Uri("https://api.example.com"))
    .AddHttpMessageHandler(sp =>
        sp.GetRequiredService<AuthorizationMessageHandler>()
            .ConfigureHandler(
                authorizedUrls: ["https://api.example.com"],
                scopes: ["api"]));

builder.Services.AddScoped(sp =>
    sp.GetRequiredService<IHttpClientFactory>().CreateClient("API"));

// Server Program.cs
builder.Services.AddAuthentication()
    .AddCookie()
    .AddJwtBearer(); // For WASM API calls after transition

builder.Services.AddCascadingAuthenticationState();

// Register platform-specific auth
builder.Services.AddAuthorizationCore();
builder.Services.AddScoped<AuthenticationStateProvider, MauiAuthStateProvider>();

// Custom provider using secure storage
public class MauiAuthStateProvider : AuthenticationStateProvider
{
    public override async Task<AuthenticationState> GetAuthenticationStateAsync()
    {
        var token = await SecureStorage.Default.GetAsync("auth_token");
        if (string.IsNullOrEmpty(token))
        {
            return new AuthenticationState(new ClaimsPrincipal(new ClaimsIdentity()));
        }

        var claims = ParseClaimsFromJwt(token);
        var identity = new ClaimsIdentity(claims, "jwt");
        return new AuthenticationState(new ClaimsPrincipal(identity));
    }
}

<AuthorizeView>
    <Authorized>
        <p>Welcome, @context.User.Identity?.Name!</p>
        <a href="/Account/Logout">Log out</a>
    </Authorized>
    <NotAuthorized>
        <a href="/Account/Login">Log in</a>
    </NotAuthorized>
    <Authorizing>
        <p>Checking authentication...</p>
    </Authorizing>
</AuthorizeView>

<AuthorizeView Roles="Admin,Manager">
    <Authorized>
        <AdminDashboard />
    </Authorized>
    <NotAuthorized>
        <p>You do not have access to the admin dashboard.</p>
    </NotAuthorized>
</AuthorizeView>

<AuthorizeView Policy="CanEditProducts">
    <Authorized>
        <button @onclick="EditProduct">Edit</button>
    </Authorized>
</AuthorizeView>

// Register policy in Program.cs
builder.Services.AddAuthorizationBuilder()
    .AddPolicy("CanEditProducts", policy =>
        policy.RequireClaim("permission", "products.edit"));

// Program.cs -- register cascading auth state
builder.Services.AddCascadingAuthenticationState();

@code {
    [CascadingParameter]
    private Task<AuthenticationState>? AuthState { get; set; }

    private string? userName;

    protected override async Task OnInitializedAsync()
    {
        if (AuthState is not null)
        {
            var state = await AuthState;
            userName = state.User.Identity?.Name;
        }
    }
}

var state = await AuthState;
var user = state.User;

// Check authentication
if (user.Identity?.IsAuthenticated == true)
{
    var email = user.FindFirst(ClaimTypes.Email)?.Value;
    var roles = user.FindAll(ClaimTypes.Role).Select(c => c.Value);
    var isAdmin = user.IsInRole("Admin");
}

# Add Identity scaffolding
dotnet add package Microsoft.AspNetCore.Identity.EntityFrameworkCore
dotnet add package Microsoft.AspNetCore.Identity.UI

// Program.cs
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("Default")));

builder.Services.AddIdentity<ApplicationUser, IdentityRole>(options =>
{
    options.Password.RequireDigit = true;
    options.Password.RequiredLength = 8;
    options.Password.RequireNonAlphanumeric = true;
    options.SignIn.RequireConfirmedAccount = true;
})
.AddEntityFrameworkStores<ApplicationDbContext>()
.AddDefaultTokenProviders();

# Scaffold individual Identity pages for customization
dotnet aspnet-codegenerator identity -dc ApplicationDbContext --files "Account.Login;Account.Register;Account.Logout"

@page "/Account/Login"
@inject SignInManager<ApplicationUser> SignInManager
@inject NavigationManager Navigation

<EditForm Model="loginModel" OnValidSubmit="HandleLogin" FormName="login" Enhance>
    <DataAnnotationsValidator />
    <ValidationSummary />

    <div>
        <InputText @bind-Value="loginModel.Email" placeholder="Email" />
    </div>
    <div>
        <InputText @bind-Value="loginModel.Password" type="password" placeholder="Password" />
    </div>
    <div>
        <InputCheckbox @bind-Value="loginModel.RememberMe" /> Remember me
    </div>

    <button type="submit">Log in</button>
</EditForm>

@if (!string.IsNullOrEmpty(errorMessage))
{
    <p class="text-danger">@errorMessage</p>
}

@code {
    [SupplyParameterFromForm]
    private LoginModel loginModel { get; set; } = new();

    private string? errorMessage;

    private async Task HandleLogin()
    {
        var result = await SignInManager.PasswordSignInAsync(
            loginModel.Email, loginModel.Password,
            loginModel.RememberMe, lockoutOnFailure: true);

        if (result.Succeeded)
        {
            Navigation.NavigateTo("/", forceLoad: true);
        }
        else if (result.RequiresTwoFactor)
        {
            Navigation.NavigateTo("/Account/LoginWith2fa");
        }
        else if (result.IsLockedOut)
        {
            errorMessage = "Account is locked. Try again later.";
        }
        else
        {
            errorMessage = "Invalid login attempt.";
        }
    }
}

@page "/admin"
@attribute [Authorize(Roles = "Admin")]

<h1>Admin Panel</h1>

@page "/products/manage"
@attribute [Authorize(Policy = "ProductManager")]

<h1>Manage Products</h1>

builder.Services.AddAuthorizationBuilder()
    .AddPolicy("ProductManager", policy =>
        policy.RequireRole("Admin", "ProductManager"))
    .AddPolicy("CanDeleteOrders", policy =>
        policy.RequireClaim("permission", "orders.delete")
              .RequireAuthenticatedUser())
    .AddPolicy("MinimumAge", policy =>
        policy.AddRequirements(new MinimumAgeRequirement(18)));

public sealed class MinimumAgeRequirement(int minimumAge) : IAuthorizationRequirement
{
    public int MinimumAge { get; } = minimumAge;
}

public sealed class MinimumAgeHandler : AuthorizationHandler<MinimumAgeRequirement>
{
    protected override Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        MinimumAgeRequirement requirement)
    {
        var dateOfBirthClaim = context.User.FindFirst("date_of_birth");
        if (dateOfBirthClaim is not null
            && DateOnly.TryParse(dateOfBirthClaim.Value, out var dob))
        {
            var age = DateOnly.FromDateTime(DateTime.UtcNow).Year - dob.Year;
            if (age >= requirement.MinimumAge)
            {
                context.Succeed(requirement);
            }
        }
        return Task.CompletedTask;
    }
}

// Register
builder.Services.AddSingleton<IAuthorizationHandler, MinimumAgeHandler>();

@inject IAuthorizationService AuthorizationService

@code {
    [CascadingParameter]
    private Task<AuthenticationState>? AuthState { get; set; }

    private bool canEdit;

    protected override async Task OnInitializedAsync()
    {
        if (AuthState is not null)
        {
            var state = await AuthState;
            var result = await AuthorizationService.AuthorizeAsync(
                state.User, "CanEditProducts");
            canEdit = result.Succeeded;
        }
    }
}

builder.Services.AddAuthentication()
    .AddMicrosoftAccount(options =>
    {
        options.ClientId = builder.Configuration["Auth:Microsoft:ClientId"]!;
        options.ClientSecret = builder.Configuration["Auth:Microsoft:ClientSecret"]!;
    })
    .AddGoogle(options =>
    {
        options.ClientId = builder.Configuration["Auth:Google:ClientId"]!;
        options.ClientSecret = builder.Configuration["Auth:Google:ClientSecret"]!;
    });

// Client Program.cs
builder.Services.AddOidcAuthentication(options =>
{
    options.ProviderOptions.Authority = "https://login.microsoftonline.com/{tenant}";
    options.ProviderOptions.ClientId = "{client-id}";
    options.ProviderOptions.ResponseType = "code";
});

var result = await WebAuthenticator.Default.AuthenticateAsync(
    new Uri("https://login.example.com/authorize"),
    new Uri("myapp://callback"));
var token = result.AccessToken;