using System.Security.Claims;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Authentication;
using Microsoft.Extensions.Options;

namespace BackendStarter.Api.Security;

public sealed class HeaderTokenAuthHandler : AuthenticationHandler<AuthenticationSchemeOptions>
{
    public const string SchemeName = "BackendStarterHeader";
    public const string HeaderName = "X-Demo-Token";

    private readonly IConfiguration _configuration;

    public HeaderTokenAuthHandler(
        IOptionsMonitor<AuthenticationSchemeOptions> options,
        ILoggerFactory logger,
        UrlEncoder encoder,
        IConfiguration configuration)
        : base(options, logger, encoder)
    {
        _configuration = configuration;
    }

    protected override Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        if (!Request.Headers.TryGetValue(HeaderName, out var headerValue))
        {
            return Task.FromResult(AuthenticateResult.NoResult());
        }

        var expectedToken = _configuration["DemoAuth:Token"];
        if (string.IsNullOrWhiteSpace(expectedToken) || headerValue.ToString() != expectedToken)
        {
            return Task.FromResult(AuthenticateResult.Fail("Invalid demo token."));
        }

        var claims = new[]
        {
            new Claim(ClaimTypes.NameIdentifier, "tutorial-user"),
            new Claim(ClaimTypes.Name, "tutorial-user")
        };
        var identity = new ClaimsIdentity(claims, SchemeName);
        var principal = new ClaimsPrincipal(identity);
        var ticket = new AuthenticationTicket(principal, SchemeName);

        return Task.FromResult(AuthenticateResult.Success(ticket));
    }
}