using System.Text.Json;
using System.Text.Json.Nodes;

namespace CVRManager.Services;

public static class CacheGuardService
{
    const string AssemblyName = "CVRCacheGuard";
    const string AssemblyFile = AssemblyName + ".dll";
    const int UserAssemblyType = 16;

    static string Source => Path.Combine(AppContext.BaseDirectory, "CacheGuard");

    static string Managed(string gameDir) => Path.Combine(gameDir, "ChilloutVR_Data", "Managed");

    public static void Deploy(string gameDir, Action<string> log, string? source = null)
    {
        var managed = Managed(gameDir);
        var scripting = Path.Combine(gameDir, "ChilloutVR_Data", "ScriptingAssemblies.json");
        var init = Path.Combine(gameDir, "ChilloutVR_Data", "RuntimeInitializeOnLoads.json");
        source ??= Source;
        if (!Directory.Exists(source) || !Directory.Exists(managed) || !File.Exists(scripting) || !File.Exists(init)) return;

        var changed = false;
        var deps = Path.Combine(managed, AssemblyName);
        Directory.CreateDirectory(deps);
        foreach (var file in Directory.EnumerateFiles(source, "*.dll"))
        {
            var name = Path.GetFileName(file);
            var target = name == AssemblyFile ? Path.Combine(managed, name) : Path.Combine(deps, name);
            changed |= CopyIfDifferent(file, target);
        }

        var scriptingJson = JsonNode.Parse(File.ReadAllText(scripting))!.AsObject();
        var names = scriptingJson["names"]!.AsArray();
        var types = scriptingJson["types"]!.AsArray();
        if (!names.Any(n => n?.GetValue<string>() == AssemblyFile))
        {
            names.Add(AssemblyFile);
            types.Add(UserAssemblyType);
            WriteJson(scripting, scriptingJson);
            changed = true;
        }

        var initJson = JsonNode.Parse(File.ReadAllText(init))!.AsObject();
        var root = initJson["root"]!.AsArray();
        if (!root.Any(e => e?["assemblyName"]?.GetValue<string>() == AssemblyName))
        {
            root.Add(new JsonObject
            {
                ["assemblyName"] = AssemblyName,
                ["nameSpace"] = AssemblyName,
                ["className"] = "Entry",
                ["methodName"] = "Init",
                ["loadTypes"] = 2,
                ["isUnityClass"] = false,
            });
            WriteJson(init, initJson);
            changed = true;
        }
        if (changed) log("Multi-instance cache guard added to this install.");
    }

    public static void Remove(string gameDir, Action<string> log)
    {
        var data = Path.Combine(gameDir, "ChilloutVR_Data");
        var scripting = Path.Combine(data, "ScriptingAssemblies.json");
        var init = Path.Combine(data, "RuntimeInitializeOnLoads.json");
        var changed = false;

        if (File.Exists(scripting))
        {
            var json = JsonNode.Parse(File.ReadAllText(scripting))!.AsObject();
            var names = json["names"]!.AsArray();
            var types = json["types"]!.AsArray();
            for (var i = names.Count - 1; i >= 0; i--)
                if (names[i]?.GetValue<string>() == AssemblyFile)
                {
                    names.RemoveAt(i);
                    if (i < types.Count) types.RemoveAt(i);
                    changed = true;
                }
            if (changed) WriteJson(scripting, json);
        }
        if (File.Exists(init))
        {
            var json = JsonNode.Parse(File.ReadAllText(init))!.AsObject();
            var root = json["root"]!.AsArray();
            var before = root.Count;
            for (var i = root.Count - 1; i >= 0; i--)
                if (root[i]?["assemblyName"]?.GetValue<string>() == AssemblyName) root.RemoveAt(i);
            if (root.Count != before)
            {
                WriteJson(init, json);
                changed = true;
            }
        }

        var managed = Managed(gameDir);
        try
        {
            File.Delete(Path.Combine(managed, AssemblyFile));
            var deps = Path.Combine(managed, AssemblyName);
            if (Directory.Exists(deps)) Directory.Delete(deps, true);
        }
        catch (Exception e) when (e is IOException or UnauthorizedAccessException) { }
        if (changed) log("Multi-instance cache guard removed from this install.");
    }

    static bool CopyIfDifferent(string source, string target)
    {
        var s = new FileInfo(source);
        var t = new FileInfo(target);
        if (t.Exists && t.Length == s.Length && t.LastWriteTimeUtc == s.LastWriteTimeUtc) return false;
        try
        {
            File.Copy(source, target, true);
            File.SetLastWriteTimeUtc(target, s.LastWriteTimeUtc);
            return true;
        }
        catch (IOException) when (t.Exists)
        {
            return false;
        }
    }

    static void WriteJson(string path, JsonNode node) =>
        File.WriteAllText(path, node.ToJsonString(new JsonSerializerOptions { WriteIndented = false }), new System.Text.UTF8Encoding(false));
}