using System.IO;
using System.Net.Http;
using System.Text;

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace Szmedi.RvKits.LLMScript
{
    public class OpenAiProvider : ILLMProvider
    {
        private static readonly HttpClient _client = new HttpClient();
        private readonly string _endpoint;
        private readonly string _apiKey;
        private readonly string _model;

        public OpenAiProvider(string endpoint, string apiKey, string model)
        {
            _endpoint = endpoint;
            _apiKey = apiKey;
            _model = model;

            _client.DefaultRequestHeaders.Clear();
            _client.DefaultRequestHeaders.Add("Authorization", $"Bearer {_apiKey}");
        }

        public async Task GenerateStreamAsync(
            string systemPrompt,
            string userPrompt,
            Action<string> onTokenReceived)
        {
            var payload = new
            {
                model = _model,
                messages = new[]
                {
                new { role = "system", content = systemPrompt },
                new { role = "user", content = userPrompt }
            },
                temperature = 0,
                stream = true
            };

            string json = JsonConvert.SerializeObject(payload);

            var request = new HttpRequestMessage(HttpMethod.Post, _endpoint);
            request.Content = new StringContent(json, Encoding.UTF8, "application/json");

            var response = await _client.SendAsync(
                request,
                HttpCompletionOption.ResponseHeadersRead);

            response.EnsureSuccessStatusCode();

            using (var stream = await response.Content.ReadAsStreamAsync())
            using (var reader = new StreamReader(stream))
            {
                while (!reader.EndOfStream)
                {
                    string line = await reader.ReadLineAsync();

                    if (string.IsNullOrWhiteSpace(line))
                        continue;

                    if (!line.StartsWith("data:"))
                        continue;

                    string data = line.Substring(5).Trim();

                    if (data == "[DONE]")
                        break;

                    JObject obj = JObject.Parse(data);
                    var delta = obj["choices"]?[0]?["delta"]?["content"];

                    if (delta != null)
                    {
                        onTokenReceived(delta.ToString());
                    }
                }
            }
        }
    }
}