온프레미스 폐쇄망과 클라우드를 잇는 인텔리전트 브릿지: ZeliDesk.Core AiService의 SSE 스트리밍 토큰 디코더 및 OpenAI 호환 엔드포인트 거버넌스 아키텍처

using var response = await _http.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, token);
response.EnsureSuccessStatusCode();

var sb = new StringBuilder();
using var stream = await response.Content.ReadAsStreamAsync(token);
using var reader = new StreamReader(stream);

while (!reader.EndOfStream && !token.IsCancellationRequested)
{
    var line = await reader.ReadLineAsync();
    if (string.IsNullOrEmpty(line)) continue;
    if (!line.StartsWith("data: ")) continue;

    var data = line.Substring(6);
    if (data == "[DONE]") break; // 스트리밍 정상 종료 플래그

    try
    {
        using var doc = JsonDocument.Parse(data);
        var choices = doc.RootElement.GetProperty("choices");
        if (choices.GetArrayLength() > 0)
        {
            var delta = choices[0].GetProperty("delta");
            if (delta.TryGetProperty("content", out var content))
            {
                string chunk = content.GetString();
                if (!string.IsNullOrEmpty(chunk))
                {
                    sb.Append(chunk);
                    onChunk?.Invoke(chunk); // UI 스레드로 0ms 즉시 디스패치
                }
            }
        }
    }
    catch { /* 부분 파손된 SSE 청크 무시 */ }
}

private static readonly string _settingsPath = Path.Combine(
    Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
    "ZeliDesk", "ai_settings.json");

public static void SaveSettings()
{
    try
    {
        Directory.CreateDirectory(Path.GetDirectoryName(_settingsPath));
        var obj = new Dictionary<string, object>
        {
            ["api_key"] = ApiKey ?? "",
            ["model"] = Model,
            ["base_url"] = BaseUrl,
            ["max_tokens"] = MaxTokens,
            ["temperature"] = Temperature
        };
        File.WriteAllText(_settingsPath, 
            JsonSerializer.Serialize(obj, new JsonSerializerOptions { WriteIndented = true }));
    }
    catch (Exception ex)
    {
        Debug.WriteLine($"[AiService] Settings save error: {ex.Message}");
    }
}

public class ChatMessage
{
    public string Role { get; set; } // "user", "assistant", "system"
    public string Content { get; set; }
    public DateTime Timestamp { get; set; } = DateTime.Now;
}

public static async Task<string> ChatAsync(
    List<ChatMessage> messages,
    string systemPrompt = null,
    CancellationToken token = default)
{
    if (!IsConfigured)
        throw new InvalidOperationException("OpenAI API 키 또는 엔드포인트가 설정되지 않았습니다.");

    var msgList = new List<object>();
    if (!string.IsNullOrEmpty(systemPrompt))
        msgList.Add(new { role = "system", content = systemPrompt });
    foreach (var msg in messages)
        msgList.Add(new { role = msg.Role, content = msg.Content });

    var requestBody = new
    {
        model = Model,
        messages = msgList,
        max_tokens = MaxTokens,
        temperature = Temperature,
        stream = false
    };

    var jsonBody = JsonSerializer.Serialize(requestBody);
    using var request = new HttpRequestMessage(HttpMethod.Post, $"{BaseUrl}/chat/completions");
    request.Headers.Add("Authorization", $"Bearer {ApiKey}");
    request.Content = new StringContent(jsonBody, Encoding.UTF8, "application/json");

    using var response = await _http.SendAsync(request, token);
    response.EnsureSuccessStatusCode();

    var responseJson = await response.Content.ReadAsStringAsync(token);
    using var doc = JsonDocument.Parse(responseJson);
    return doc.RootElement
        .GetProperty("choices")[0]
        .GetProperty("message")
        .GetProperty("content")
        .GetString();
}