components/LiteCharms.Features/Api/TokenService.cs

using LiteCharms.Features.Api.Configuration;
using LiteCharms.Features.Api.Models;
using LiteCharms.Features.Api.Sdk;

namespace LiteCharms.Features.Api;

public sealed class TokenService(IConnectApi connectApi, IOptions<LiteCharmsClientSettings> clientOptions)
{
    private readonly LiteCharmsClientSettings clientSettings = clientOptions.Value;

    public async Task<Result<TokenResponse>> GenerateAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var request = new TokenRequest
            {
                ClientId = clientSettings.ClientId,
                ClientSecret = clientSettings.ClientSecret,
                GrantType = clientSettings.GrantType,
                Scope = clientSettings.Scope,
            };

            using var response = await connectApi.GetToken(request, cancellationToken);

            var contentRaw = await response.Content.ReadAsStringAsync(cancellationToken);

            if (string.IsNullOrWhiteSpace(contentRaw))
                return Result.Fail(new Error($"The authentication endpoint returned an empty payload. Status code: {response.StatusCode}"));

            if (response.IsSuccessStatusCode)
            {
                var tokenResponse = JsonSerializer.Deserialize<TokenResponse>(contentRaw);

                return !string.IsNullOrWhiteSpace(tokenResponse?.AccessToken)
                    ? Result.Ok(tokenResponse)
                    : Result.Fail<TokenResponse>(new Error("Authentication succeeded, but no access token was found in the response payload."));
            }

            try
            {
                var errorResult = JsonSerializer.Deserialize<TokenErrorResponse>(contentRaw);

                if (errorResult != null)
                {
                    string summary = $"{errorResult.Error}: {errorResult.ErrorDescription}";

                    return Result.Fail(new Error(summary));
                }
            }
            catch
            {
                return Result.Fail(new Error($"Authentication failed: {contentRaw}"));
            }

            return Result.Fail(new Error($"Authentication failed with status code: {response.StatusCode}"));
        }
        catch (OperationCanceledException ex)
        {
            return Result.Fail(new Error("The token generation request was canceled.").CausedBy(ex));
        }
        catch (Exception ex)
        {
            return Result.Fail(new Error(ex.Message).CausedBy(ex));
        }
    }
}