using System;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.Networking;

namespace tysdk
{
    public interface IPaymentVerifier
    {
        Task<VerifyResult> Verify(PaymentInfo info);
        void Consume(string token);
    }

    public class VerifyResult
    {
        public bool success;
        public string msg;
    }

    public static class PaymentVerifierFactory
    {
        public static IPaymentVerifier GetVerifier()
        {
            return ChannelConfig.Channel switch
            {
                "Flexion" => new RetryablePaymentVerifier(new FlexionPaymentVerifier()),
                "Dummy" => new RetryablePaymentVerifier(new DummyPaymentVerifier()),
                _ => null
            };
        }
    }

    public class RetryablePaymentVerifier : IPaymentVerifier
    {
        private readonly IPaymentVerifier _inner;
        private const int MaxRetries = 2;
        private static readonly TimeSpan RetryInterval = TimeSpan.FromSeconds(2);

        public RetryablePaymentVerifier(IPaymentVerifier inner)
        {
            _inner = inner;
        }

        public async Task<VerifyResult> Verify(PaymentInfo info)
        {
            VerifyResult lastResult = null;
            for (int attempt = 0; attempt <= MaxRetries; attempt++)
            {
                if (attempt > 0)
                {
                    Debug.Log($"[RetryableVerifier] Flow retry {attempt}/{MaxRetries}, waiting {RetryInterval.TotalSeconds}s");
                    await Task.Delay(RetryInterval);
                }
                lastResult = await _inner.Verify(info);
                if (lastResult.success) return lastResult;
                Debug.LogWarning($"[RetryableVerifier] Flow attempt {attempt + 1} failed: {lastResult.msg}");
            }
            return lastResult;
        }

        public void Consume(string token) => _inner.Consume(token);
    }

    public class FlexionPaymentVerifier : IPaymentVerifier
    {
        // TODO: 替换为实际游戏服务端验签 URL
        private const string VERIFY_URL = "https://YOUR_GAME_SERVER/api/pay/verify";
        private static readonly TimeSpan Timeout = TimeSpan.FromSeconds(30);
        private const int MaxRetries = 2;
        private static readonly TimeSpan RetryBackoff = TimeSpan.FromSeconds(2);

#if UNITY_EDITOR
        public async Task<VerifyResult> Verify(PaymentInfo info)
        {
            Debug.LogWarning("[FlexionPaymentVerifier] Editor placeholder: auto success");
            await Task.Yield();
            return new VerifyResult { success = true, msg = "editor_placeholder" };
        }
#else
        public async Task<VerifyResult> Verify(PaymentInfo info)
        {
            VerifyResult lastResult = null;
            for (int attempt = 0; attempt <= MaxRetries; attempt++)
            {
                if (attempt > 0)
                {
                    var delay = TimeSpan.FromSeconds(RetryBackoff.TotalSeconds * attempt);
                    Debug.Log($"[FlexionPaymentVerifier] HTTP retry {attempt}/{MaxRetries}, waiting {delay.TotalSeconds}s");
                    await Task.Delay(delay);
                }
                lastResult = await SendVerifyRequest(BuildRequestBody(info));
                if (lastResult.success) return lastResult;
                Debug.LogWarning($"[FlexionPaymentVerifier] HTTP attempt {attempt + 1} failed: {lastResult.msg}");
            }
            return lastResult;
        }

        private async Task<VerifyResult> SendVerifyRequest(string body)
        {
            var cts = new CancellationTokenSource(Timeout);
            try
            {
                Debug.Log("[FlexionPaymentVerifier] Sending verification request");

                using var req = new UnityWebRequest(VERIFY_URL, "POST");
                req.uploadHandler = new UploadHandlerRaw(Encoding.UTF8.GetBytes(body));
                req.downloadHandler = new DownloadHandlerBuffer();
                req.SetRequestHeader("Content-Type", "application/json");

                var tcs = new TaskCompletionSource<VerifyResult>(TaskCreationOptions.RunContinuationsAsynchronously);
                cts.Token.Register(() => tcs.TrySetResult(new VerifyResult { success = false, msg = "timeout" }));

                req.SendWebRequest().completed += _ =>
                {
                    if (req.result == UnityWebRequest.Result.Success)
                    {
                        Debug.Log("[FlexionPaymentVerifier] Response: " + req.downloadHandler.text);
                        // TODO: 按实际服务端响应格式解析
                        tcs.TrySetResult(new VerifyResult { success = true, msg = "ok" });
                    }
                    else
                    {
                        Debug.LogWarning("[FlexionPaymentVerifier] Failed: " + req.error);
                        tcs.TrySetResult(new VerifyResult { success = false, msg = req.error });
                    }
                };

                return await tcs.Task;
            }
            catch (Exception e)
            {
                Debug.LogError("[FlexionPaymentVerifier] Exception: " + e.Message);
                return new VerifyResult { success = false, msg = e.Message };
            }
            finally
            {
                cts.Dispose();
            }
        }

        private static string BuildRequestBody(PaymentInfo info)
        {
            var body = new StringBuilder();
            body.Append('{');
            body.Append("\"purchaseJson\":").Append(Escape(info.purchaseJson)).Append(',');
            body.Append("\"signature\":").Append(Escape(info.signature)).Append(',');
            body.Append("\"orderId\":").Append(Escape(info.orderId)).Append(',');
            body.Append("\"productId\":").Append(Escape(info.productId)).Append(',');
            body.Append("\"purchaseToken\":").Append(Escape(info.purchaseToken));
            body.Append('}');
            return body.ToString();
        }
#endif

        private static string Escape(string s)
        {
            if (s == null) return "null";
            return '"' + s.Replace("\\", "\\\\").Replace("\"", "\\\"") + '"';
        }

#if UNITY_EDITOR
        public void Consume(string token) { }
#elif UNITY_ANDROID
        public void Consume(string token)
        {
            if (string.IsNullOrEmpty(token)) return;
            using var sdkManager = new AndroidJavaClass("com.unity3d.player.SDKManager");
            sdkManager.CallStatic("ConsumeFlexionPurchase", token);
        }
#endif
    }

    public class DummyPaymentVerifier : IPaymentVerifier
    {
        public async Task<VerifyResult> Verify(PaymentInfo info)
        {
            Debug.Log("[DummyPaymentVerifier] Verifying purchase: " + info.orderId);
            await Task.Delay(500);
            return new VerifyResult { success = true, msg = "dummy_ok" };
        }

        public void Consume(string token)
        {
            Debug.Log("[DummyPaymentVerifier] Consume: " + token);
        }
    }
}