using System;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text.Json;
using System.Threading.Tasks;

namespace Gott.Services
{
    public class OpenAiCheckResult
    {
        public string Status { get; set; }     // "ok", "invalid", "rate_limited", "quota_exceeded", "error"
        public string Message { get; set; }
        public string Organization { get; set; }
        public string[] Models { get; set; }
        public int? RateLimitRpm { get; set; }
        public int? RateLimitTpm { get; set; }
    }

    public static class OpenAiKeyChecker
    {
        public static async Task<OpenAiCheckResult> CheckKeyAsync(IHttpClientFactory httpFactory, string apiKey)
        {
            try
            {
                var client = httpFactory.CreateClient();
                client.Timeout = TimeSpan.FromSeconds(30);

                var request = new HttpRequestMessage(HttpMethod.Get, "https://api.openai.com/v1/models");
                request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);

                var resp = await client.SendAsync(request);
                var statusCode = (int)resp.StatusCode;

                if (statusCode == 401)
                    return new OpenAiCheckResult { Status = "invalid", Message = "Ungültig oder abgelaufen (401)" };

                if (statusCode == 403)
                    return new OpenAiCheckResult { Status = "quota_exceeded", Message = "Keine Berechtigung / Quota erschöpft (403)" };

                if (statusCode == 429)
                {
                    // 429 kann Rate-Limit ODER Quota-Exceeded sein → Body prüfen
                    try
                    {
                        var errBody = await resp.Content.ReadAsStringAsync();
                        var errDoc = JsonDocument.Parse(errBody);
                        if (errDoc.RootElement.TryGetProperty("error", out var errObj)
                            && errObj.TryGetProperty("code", out var codeProp))
                        {
                            var code = codeProp.GetString();
                            if (code == "insufficient_quota")
                                return new OpenAiCheckResult { Status = "quota_exceeded", Message = "Kein Guthaben / Quota erschöpft (429)" };
                        }
                    }
                    catch { /* Body nicht parsbar → als Rate-Limit behandeln */ }

                    return new OpenAiCheckResult { Status = "rate_limited", Message = "Rate Limited (429)" };
                }

                if (statusCode >= 400)
                    return new OpenAiCheckResult { Status = "error", Message = "API-Fehler (" + statusCode + ")" };

                // 200 OK → Key existiert, Modelle extrahieren
                var body = await resp.Content.ReadAsStringAsync();
                var doc = JsonDocument.Parse(body);

                // Organisation aus Header
                string org = null;
                if (resp.Headers.TryGetValues("openai-organization", out var orgValues))
                    org = orgValues.FirstOrDefault();

                // Modell-Liste extrahieren (nur die interessantesten)
                string[] models = Array.Empty<string>();
                if (doc.RootElement.TryGetProperty("data", out var data))
                {
                    var interestingPrefixes = new[] { "gpt-5", "gpt-4", "gpt-3.5", "o1", "o3", "o4", "chatgpt" };
                    models = data.EnumerateArray()
                        .Select(m => m.GetProperty("id").GetString())
                        .Where(id => interestingPrefixes.Any(p => id.StartsWith(p, StringComparison.OrdinalIgnoreCase)))
                        .Distinct()
                        .OrderBy(x => x)
                        .ToArray();
                }

                // Plan-Erkennung anhand der Modelle
                string plan;
                if (models.Any(m => m.StartsWith("gpt-5", StringComparison.OrdinalIgnoreCase)
                                 || m.StartsWith("o3", StringComparison.OrdinalIgnoreCase)
                                 || m.StartsWith("o4", StringComparison.OrdinalIgnoreCase)))
                    plan = "Tier 5+";
                else if (models.Any(m => m.StartsWith("gpt-4o", StringComparison.OrdinalIgnoreCase)))
                    plan = "Tier 3+";
                else if (models.Any(m => m.StartsWith("gpt-4", StringComparison.OrdinalIgnoreCase)))
                    plan = "Tier 2+";
                else if (models.Any(m => m.StartsWith("gpt-3.5", StringComparison.OrdinalIgnoreCase)))
                    plan = "Tier 1";
                else
                    plan = "Free";

                // Schritt 2: Echten Chat-Call mit max_tokens=1 um Quota zu prüfen
                // /v1/models gibt 200 auch bei quota_exceeded Keys!
                var usable = await CheckQuotaAsync(client, apiKey);

                var msg = plan + " · Org: " + (org ?? "?") + " · " + models.Length + " Modelle";

                // Rate-Limits aus dem Chat-Call-Header (falls verfügbar)
                if (usable.Rpm.HasValue) msg += " · " + usable.Rpm.Value + " RPM";
                if (usable.Tpm.HasValue) msg += " · " + usable.Tpm.Value + " TPM";

                if (!usable.HasQuota)
                {
                    var reason = usable.QuotaError == "billing_not_active"
                        ? "Billing inaktiv"
                        : "Kein Guthaben";
                    return new OpenAiCheckResult
                    {
                        Status = "quota_exceeded",
                        Message = "⚠️ " + msg + " · " + reason,
                        Organization = org,
                        Models = models,
                        RateLimitRpm = usable.Rpm,
                        RateLimitTpm = usable.Tpm
                    };
                }

                return new OpenAiCheckResult
                {
                    Status = "ok",
                    Message = msg,
                    Organization = org,
                    Models = models,
                    RateLimitRpm = usable.Rpm,
                    RateLimitTpm = usable.Tpm
                };
            }
            catch (Exception ex)
            {
                return new OpenAiCheckResult { Status = "error", Message = ex.Message };
            }
        }

        private class QuotaResult
        {
            public bool HasQuota { get; set; }
            public string QuotaError { get; set; }
            public int? Rpm { get; set; }
            public int? Tpm { get; set; }
        }

        private static async Task<QuotaResult> CheckQuotaAsync(HttpClient client, string apiKey)
        {
            try
            {
                var chatReq = new HttpRequestMessage(HttpMethod.Post, "https://api.openai.com/v1/chat/completions");
                chatReq.Headers.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
                chatReq.Content = new StringContent(
                    "{\"model\":\"gpt-4o-mini\",\"messages\":[{\"role\":\"user\",\"content\":\"hi\"}],\"max_tokens\":1}",
                    System.Text.Encoding.UTF8, "application/json");

                var chatResp = await client.SendAsync(chatReq);
                var chatStatus = (int)chatResp.StatusCode;

                int? rpm = null;
                int? tpm = null;
                if (chatResp.Headers.TryGetValues("x-ratelimit-limit-requests", out var rpmVals)
                    && int.TryParse(rpmVals.FirstOrDefault(), out var rpmVal))
                    rpm = rpmVal;
                if (chatResp.Headers.TryGetValues("x-ratelimit-limit-tokens", out var tpmVals)
                    && int.TryParse(tpmVals.FirstOrDefault(), out var tpmVal))
                    tpm = tpmVal;

                if (chatStatus == 429)
                {
                    try
                    {
                        var errBody = await chatResp.Content.ReadAsStringAsync();
                        var errDoc = JsonDocument.Parse(errBody);
                        if (errDoc.RootElement.TryGetProperty("error", out var errObj)
                            && errObj.TryGetProperty("code", out var codeProp)
                            )
                        {
                            var code = codeProp.GetString();
                            if (code == "insufficient_quota" || code == "billing_not_active")
                            {
                                return new QuotaResult { HasQuota = false, QuotaError = code, Rpm = rpm, Tpm = tpm };
                            }
                        }
                    }
                    catch { }

                    // Echtes Rate-Limit → Key hat Quota, ist nur temporär blockiert
                    return new QuotaResult { HasQuota = true, Rpm = rpm, Tpm = tpm };
                }

                // 200 = funktioniert, alles andere = vermutlich trotzdem nutzbar
                return new QuotaResult { HasQuota = chatStatus < 400, Rpm = rpm, Tpm = tpm };
            }
            catch
            {
                // Bei Netzwerkfehler etc. → optimistisch annehmen
                return new QuotaResult { HasQuota = true };
            }
        }
    }
}