using System;
using System.IO;
using UnityEngine;

namespace OnDeviceAgent.Inference
{
    // Returns a readable ABSOLUTE directory for a "Model/<X>" root so the sentis packages can File.* it.
    // Non-Android (Editor & Standalone): ModelPathResolver already gives a real readable directory - the
    // owning package's Models~ in the Editor, streamingAssetsPath/<sub> in a player.
    // Android: StreamingAssets lives inside the APK and File.* can't read it, so the tree is staged once into
    // persistentDataPath (idempotent, like LiteRtModelProvisioner) from the build-generated files_manifest.txt.
    public static class ModelRootProvisioner
    {
        const string ManifestFile = "files_manifest.txt";

        public static string EnsureModelRoot(string subRelative)
        {
            var sub = (subRelative ?? string.Empty).Replace('\\', '/').TrimEnd('/');

            if (Application.platform != RuntimePlatform.Android)
                return ModelPathResolver.GetModelFilePath(sub);

            return StageToPersistentData(sub);
        }

        static string StageToPersistentData(string sub)
        {
            var destRoot = Path.Combine(Application.persistentDataPath, sub.Replace('/', Path.DirectorySeparatorChar));

            var manifest = StreamingAssetsModelLoader.LoadText(sub + "/" + ManifestFile, "[ModelRoot]");
            var lines = manifest.Split(new[] { '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries);

            foreach (var raw in lines)
            {
                var rel = raw.Trim().Replace('\\', '/');
                if (rel.Length == 0 || rel[0] == '#')
                    continue;

                var dest = Path.Combine(destRoot, rel.Replace('/', Path.DirectorySeparatorChar));
                if (File.Exists(dest) && new FileInfo(dest).Length > 0)
                    continue;

                try
                {
                    var bytes = StreamingAssetsModelLoader.LoadBytes(sub + "/" + rel, "[ModelRoot]");
                    var destDir = Path.GetDirectoryName(dest);
                    if (!string.IsNullOrEmpty(destDir))
                        Directory.CreateDirectory(destDir);
                    File.WriteAllBytes(dest, bytes);
                }
                catch (Exception exception)
                {
                    Debug.LogWarning($"[ModelRoot] skipped staging '{rel}' under {sub}: {exception.Message}");
                }
            }

            return destRoot;
        }
    }
}