using System;
using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;

namespace AOT.Patch
{
    public sealed class VersionClient
    {
        readonly string _url;
        readonly bool _allowStreamingFallback;

        public VersionClient(string url, bool allowStreamingFallback)
        {
            _url = url;
            _allowStreamingFallback = allowStreamingFallback;
        }

        public IEnumerator Fetch(Action<VersionInfo, string> onDone)
        {
            string error = null;
            VersionInfo info = null;

            if (!string.IsNullOrEmpty(_url))
            {
                using (var req = UnityWebRequest.Get(_url))
                {
                    req.timeout = 15;
                    yield return req.SendWebRequest();
#if UNITY_2020_2_OR_NEWER
                    bool failed = req.result != UnityWebRequest.Result.Success;
#else
                    bool failed = req.isNetworkError || req.isHttpError;
#endif
                    if (!failed)
                    {
                        info = VersionInfo.FromJson(req.downloadHandler.text);
                        if (info == null)
                            error = "version.json parse failed";
                    }
                    else
                    {
                        error = req.error;
                    }
                }
            }

            if (info == null && _allowStreamingFallback)
            {
                var localPath = Path.Combine(Application.streamingAssetsPath, "cdn", "version.json");
                yield return ReadLocalText(localPath, text =>
                {
                    if (!string.IsNullOrEmpty(text))
                    {
                        info = VersionInfo.FromJson(text);
                        if (info != null)
                            error = null;
                    }
                });
            }

            onDone?.Invoke(info, error);
        }

        static IEnumerator ReadLocalText(string path, Action<string> onDone)
        {
#if UNITY_ANDROID && !UNITY_EDITOR
            using (var req = UnityWebRequest.Get(path))
            {
                yield return req.SendWebRequest();
#if UNITY_2020_2_OR_NEWER
                bool failed = req.result != UnityWebRequest.Result.Success;
#else
                bool failed = req.isNetworkError || req.isHttpError;
#endif
                onDone?.Invoke(failed ? null : req.downloadHandler.text);
            }
#else
            if (File.Exists(path))
                onDone?.Invoke(File.ReadAllText(path));
            else
                onDone?.Invoke(null);
            yield break;
#endif
        }
    }
}