using System;
using System.IO;
using Unity.InferenceEngine;
using UnityEngine;
using UnityEngine.Networking;

namespace OnDeviceAgent.Inference
{
public static class StreamingAssetsModelLoader
{
    public static Model LoadModel(string relativePath, string logPrefix)
    {
        var path = GetStreamingAssetPath(relativePath);
        if (CanReadStreamingAssetsWithFileApi() && File.Exists(path))
            return ModelLoader.Load(path);

        var bytes = LoadBytesFromStreamingAssets(path, logPrefix);
        using (var stream = new MemoryStream(bytes))
            return ModelLoader.Load(stream);
    }

    public static string LoadText(string relativePath, string logPrefix)
    {
        var path = GetStreamingAssetPath(relativePath);
        if (CanReadStreamingAssetsWithFileApi() && File.Exists(path))
            return File.ReadAllText(path);

        return System.Text.Encoding.UTF8.GetString(LoadBytesFromStreamingAssets(path, logPrefix));
    }

    public static byte[] LoadBytes(string relativePath, string logPrefix)
    {
        var path = GetStreamingAssetPath(relativePath);
        if (CanReadStreamingAssetsWithFileApi() && File.Exists(path))
            return File.ReadAllBytes(path);

        return LoadBytesFromStreamingAssets(path, logPrefix);
    }

    static string GetStreamingAssetPath(string relativePath)
    {
        return ModelPathResolver.GetModelFilePath(relativePath);
    }

    static bool CanReadStreamingAssetsWithFileApi()
    {
        return Application.platform != RuntimePlatform.Android &&
               Application.platform != RuntimePlatform.WebGLPlayer;
    }

    static byte[] LoadBytesFromStreamingAssets(string path, string logPrefix)
    {
        using (var request = UnityWebRequest.Get(ToStreamingAssetUri(path)))
            {
                var operation = request.SendWebRequest();
                // Blocks calling thread (Android/WebGL only); Sleep(1) avoids spin.
                while (!operation.isDone)
                    System.Threading.Thread.Sleep(1);

                if (request.result != UnityWebRequest.Result.Success)
                    throw new FileNotFoundException($"{logPrefix} Missing StreamingAssets file: {path} ({request.error})", path);

                return request.downloadHandler.data;
            }
        }

        static string ToStreamingAssetUri(string path)
        {
            if (path.StartsWith("jar:", StringComparison.OrdinalIgnoreCase) ||
                path.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ||
                path.StartsWith("https://", StringComparison.OrdinalIgnoreCase) ||
                path.StartsWith("file://", StringComparison.OrdinalIgnoreCase))
                return path;

            return "file://" + path;
        }
    }
}