Program.cs

using AuthService.API.Services;
using AuthService.API.Interfaces;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;
using System.Text;
//to register DB context if using a real database
using Microsoft.EntityFrameworkCore;
using AuthService.API.Data;   //the folder where dbcontext is in
using AuthService.API.Models;


var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();

//jwt authentication configuration:
builder.Services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
    .AddJwtBearer(options =>
{
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuer = true,
        ValidateAudience = true,
        ValidateLifetime = true,
        ValidateIssuerSigningKey = true,
        ValidIssuer = builder.Configuration["JwtSettings:Issuer"],
        ValidAudience = builder.Configuration["JwtSettings:Audience"],
        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(builder.Configuration["JwtSettings:Key"]))
    };
});

//add authorization services - this enables autherization so we can protect endpoints with [Authorize] attribute
builder.Services.AddAuthorization(); 

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();



//Register AuthService for dependency injection
//builder.Services.AddSingleton <IAuthService,AuthenticationService>(); (while using in memory list)
builder.Services.AddScoped<IAuthService, AuthenticationService>(); //when using a real database, use scoped lifetime
//register db context for dependency injection
builder.Services.AddDbContext<AuthDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));
var app = builder.Build();

//admin seeding logic
using(var scope=app.Services.CreateScope())
{
    var context = scope.ServiceProvider.GetRequiredService<AuthDbContext>();
    if(!context.Users.Any(u=>u.Role=="Admin"))
    {
        var admin = new User
        {
            Username = "admin",
            Email = "admin@ecom.com",
            PasswordHash = BCrypt.Net.BCrypt.HashPassword("Admin@123"), //hash the password
            Role = "Admin",
            CreatedAt = DateTime.UtcNow,
            IsActive = true
        };
        context.Users.Add(admin);
        context.SaveChanges();
    }
}

//enable authentication in pipeline - order matters: authentication first, then authorization
app.UseAuthentication();
app.UseAuthorization();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{    
    app.UseSwagger();
    app.UseSwaggerUI();
}
app.UseHttpsRedirection();

app.MapControllers();

app.Run();