proposal-system/api/src/ProposalSystem.Api/Controllers/AuthController.cs

using System.IdentityModel.Tokens.Jwt;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Text.Json;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using ProposalSystem.Domain.Entities;
using ProposalSystem.Infrastructure.Data;

namespace ProposalSystem.Api.Controllers;

[ApiController]
[Route("api/[controller]")]
public class AuthController : ControllerBase
{
    private readonly ProposalDbContext _db;
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IConfiguration _config;

    public AuthController(ProposalDbContext db, IHttpClientFactory httpClientFactory, IConfiguration config)
    {
        _db = db;
        _httpClientFactory = httpClientFactory;
        _config = config;
    }

    [HttpPost("callback")]
    public async Task<ActionResult<AuthResponse>> Callback([FromBody] AuthCallbackRequest request, CancellationToken ct)
    {
        var domain = _config["Auth:CognitoDomain"];
        var clientId = _config["Auth:ClientId"];

        if (string.IsNullOrEmpty(domain) || string.IsNullOrEmpty(clientId))
            return StatusCode(500, new { message = "Auth not configured" });

        var tokenResponse = await ExchangeCodeAsync(domain, clientId, request.Code, request.RedirectUri, ct);
        if (tokenResponse == null)
            return BadRequest(new { message = "Failed to exchange authorization code" });

        var handler = new JwtSecurityTokenHandler();
        var idToken = handler.ReadJwtToken(tokenResponse.IdToken);

        var sub = idToken.Claims.FirstOrDefault(c => c.Type == "sub")?.Value
            ?? throw new InvalidOperationException("No sub claim in ID token");
        var email = idToken.Claims.FirstOrDefault(c => c.Type == "email")?.Value ?? "";
        var name = idToken.Claims.FirstOrDefault(c => c.Type == "name")?.Value
            ?? idToken.Claims.FirstOrDefault(c => c.Type == "cognito:username")?.Value
            ?? email.Split('@')[0];
        var groups = idToken.Claims.Where(c => c.Type == "cognito:groups").Select(c => c.Value).ToList();

        var role = groups.Contains("sysadmins") ? UserRole.SysAdmin
            : groups.Contains("admins") ? UserRole.Admin
            : UserRole.Dispatcher;

        var user = await _db.Users.FirstOrDefaultAsync(u => u.CognitoSub == sub, ct);
        if (user == null)
        {
            user = new User
            {
                Id = Guid.NewGuid(),
                CognitoSub = sub,
                Email = email,
                DisplayName = name,
                Role = role,
                IsActive = true,
                CreatedAt = DateTime.UtcNow,
                UpdatedAt = DateTime.UtcNow,
            };
            _db.Users.Add(user);
            await _db.SaveChangesAsync(ct);
        }
        else if (user.Email != email || user.DisplayName != name)
        {
            user.Email = email;
            user.DisplayName = name;
            user.UpdatedAt = DateTime.UtcNow;
            await _db.SaveChangesAsync(ct);
        }

        return Ok(new AuthResponse(
            user.Id.ToString(),
            user.Email,
            user.DisplayName,
            user.Role.ToString(),
            tokenResponse.AccessToken
        ));
    }

    private async Task<CognitoTokenResponse?> ExchangeCodeAsync(
        string domain, string clientId, string code, string redirectUri, CancellationToken ct)
    {
        var client = _httpClientFactory.CreateClient();
        var tokenUrl = $"https://{domain}/oauth2/token";

        var content = new FormUrlEncodedContent(new Dictionary<string, string>
        {
            ["grant_type"] = "authorization_code",
            ["client_id"] = clientId,
            ["code"] = code,
            ["redirect_uri"] = redirectUri,
        });

        var response = await client.PostAsync(tokenUrl, content, ct);
        if (!response.IsSuccessStatusCode) return null;

        var json = await response.Content.ReadAsStringAsync(ct);
        return JsonSerializer.Deserialize<CognitoTokenResponse>(json);
    }
}

public record AuthCallbackRequest(string Code, string RedirectUri);

public record AuthResponse(string Id, string Email, string DisplayName, string Role, string Token);

internal class CognitoTokenResponse
{
    [System.Text.Json.Serialization.JsonPropertyName("access_token")]
    public string AccessToken { get; set; } = "";

    [System.Text.Json.Serialization.JsonPropertyName("id_token")]
    public string IdToken { get; set; } = "";

    [System.Text.Json.Serialization.JsonPropertyName("refresh_token")]
    public string RefreshToken { get; set; } = "";

    [System.Text.Json.Serialization.JsonPropertyName("token_type")]
    public string TokenType { get; set; } = "";

    [System.Text.Json.Serialization.JsonPropertyName("expires_in")]
    public int ExpiresIn { get; set; }
}