using Godot;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;

public partial class PackManager : Node
{
	public record PackManifest(int schema, string id, string name, string version, int priority);

	private readonly List<(string Root, PackManifest Manifest)> _packs = new();

	public override void _EnterTree()
	{
		LoadPacks("res://packs");
		GD.Print($"Loaded packs: {string.Join(", ", _packs.Select(p => $"{p.Manifest.id}(prio={p.Manifest.priority})"))}");
	}

	public override void _Ready()
	{/*
		LoadPacks("res://packs");
		GD.Print($"Loaded packs: {string.Join(", ", _packs.Select(p => $"{p.Manifest.id}(prio={p.Manifest.priority})"))}");*/
	}

	public void LoadPacks(string packsRoot)
	{
		_packs.Clear();

		if (!DirAccess.DirExistsAbsolute(packsRoot))
		{
			GD.PrintErr($"Packs root missing: {packsRoot}");
			return;
		}

		using var dir = DirAccess.Open(packsRoot);
		dir.ListDirBegin();
		while (true)
		{
			var entry = dir.GetNext();
			if (entry == "") break;
			if (entry.StartsWith(".")) continue;

			var packPath = $"{packsRoot}/{entry}";
			if (!dir.CurrentIsDir()) continue;

			var manifestPath = $"{packPath}/pack.json";
			if (!FileAccess.FileExists(manifestPath))
				continue;

			var json = FileAccess.GetFileAsString(manifestPath);
			var manifest = JsonSerializer.Deserialize<PackManifest>(json);
			if (manifest == null)
			{
				GD.PrintErr($"Invalid pack.json: {manifestPath}");
				continue;
			}

			_packs.Add((packPath, manifest));
		}
		dir.ListDirEnd();

		// Sort bottom->top by priority (low first, high last)
		_packs.Sort((a, b) => a.Manifest.priority.CompareTo(b.Manifest.priority));
	}

	/// Returns the best (topmost) existing file path for a relative path inside a pack.
	public string? Resolve(string relativePath)
	{
		relativePath = relativePath.TrimStart('/');

		// Highest priority pack wins -> iterate from end
		for (int i = _packs.Count - 1; i >= 0; i--)
		{
			var candidate = $"{_packs[i].Root}/{relativePath}";
			if (FileAccess.FileExists(candidate))
				return candidate;
		}
		return null;
	}
}