using System;
using System.IO;
using UnityEngine;
using OnDeviceAgent.Inference;
namespace OnDeviceAgent.AgentCore
{

    public static class StreamingDbInstaller
    {
        const string ManifestFile = "db_manifest.txt";

        public static string Install(string subdir, Action<string> log)
        {
            var dest = Path.Combine(Application.persistentDataPath, subdir);
            var destManifest = Path.Combine(dest, ManifestFile);

            string srcManifest;
            try
            {
                srcManifest = StreamingAssetsModelLoader.LoadText(subdir + "/" + ManifestFile, "[RAG]");
            }
            catch (Exception e)
            {
                log?.Invoke("[RAG] no DB manifest in StreamingAssets/" + subdir + " (" + e.Message +
                            "), run OnDeviceAgent ▸ RAG ▸ Ingest Knowledge to DB first.");
                Directory.CreateDirectory(dest);
                return dest;
            }

            // WriteManifest stamps an ISO timestamp so any new ingest changes the manifest text - stale installs are detected automatically.
            if (File.Exists(destManifest))
            {
                try
                {
                    var destText = File.ReadAllText(destManifest);
                    if (string.Equals(destText, srcManifest, StringComparison.Ordinal))
                    {
                        log?.Invoke("[RAG] DB already up-to-date at " + dest + ".");
                        return dest;
                    }
                    log?.Invoke("[RAG] DB stale at " + dest + ", refreshing from StreamingAssets/" + subdir + ".");
                }
                catch (Exception e)
                {
                    log?.Invoke("[RAG] stale-check failed (" + e.Message + "), refreshing.");
                }

                try { Directory.Delete(dest, true); }
                catch (Exception e) { log?.Invoke("[RAG] couldn't clear stale DB: " + e.Message); }
            }

            Directory.CreateDirectory(dest);

            var copied = 0;
            foreach (var raw in srcManifest.Replace("\r", string.Empty).Split('\n'))
            {
                var rel = raw.Trim();
                if (rel.Length == 0 || rel.StartsWith("#")) continue;
                try
                {
                    var content = StreamingAssetsModelLoader.LoadText(subdir + "/" + rel, "[RAG]");
                    var outPath = Path.Combine(dest, rel.Replace('/', Path.DirectorySeparatorChar));
                    Directory.CreateDirectory(Path.GetDirectoryName(outPath));
                    File.WriteAllText(outPath, content);
                    copied++;
                }
                catch (Exception e)
                {
                    log?.Invoke("[RAG] DB copy failed for " + rel + ": " + e.Message);
                }
            }

            // Write manifest last so a partial copy isn't mistaken for a complete install on next launch.
            try { File.WriteAllText(destManifest, srcManifest); } catch (Exception e) { log?.Invoke("[RAG] manifest write failed: " + e.Message); }
            log?.Invoke("[RAG] installed DB to " + dest + " (" + copied + " files).");
            return dest;
        }
    }
}