using System.ComponentModel;
using System.Text;

namespace MAF1.Tools;

/// <summary>
/// 给 LLM 调用的本地读文件工具。Description 属性会进工具 schema，模型据此决定何时调用。
/// 路径解析会试当前目录、exe 目录、以及 MAF1_CONTENT_ROOT（插件进程由宿主注入）。
/// </summary>
public static class FileTools
{
    [Description("Read the full UTF-8 text of a local file. Always call this before judging city names.")]
    public static string ReadTextFile([Description("Absolute or relative path of the file to read.")] string path)
    {
        if (string.IsNullOrWhiteSpace(path))
        {
            return "未提供文件路径。";
        }

        string? resolved = Resolve(path.Trim().Trim('"'));
        if (resolved is null)
        {
            return $"找不到文件：{path}";
        }

        FileInfo info = new(resolved);
        if (info.Length > 64 * 1024)
        {
            return $"文件过大（{info.Length} 字节），请换一个不超过 64KB 的文本文件。";
        }

        return File.ReadAllText(resolved, Encoding.UTF8);
    }

    /// <summary>相对路径时依次试 cwd、exe 目录、内容根、再往上两级父目录（适配 bin/Debug/netX）。</summary>
    private static string? Resolve(string path)
    {
        if (Path.IsPathRooted(path) && File.Exists(path))
        {
            return Path.GetFullPath(path);
        }

        string fromCwd = Path.GetFullPath(path);
        if (File.Exists(fromCwd))
        {
            return fromCwd;
        }

        foreach (string root in SearchRoots())
        {
            string candidate = Path.GetFullPath(Path.Combine(root, path));
            if (File.Exists(candidate))
            {
                return candidate;
            }
        }

        return null;
    }

    private static IEnumerable<string> SearchRoots()
    {
        yield return AppContext.BaseDirectory;
        string? contentRoot = Environment.GetEnvironmentVariable("MAF1_CONTENT_ROOT");
        if (!string.IsNullOrWhiteSpace(contentRoot))
        {
            yield return contentRoot;
        }

        DirectoryInfo? parent = Directory.GetParent(AppContext.BaseDirectory.TrimEnd(Path.DirectorySeparatorChar));
        if (parent is not null)
        {
            yield return parent.FullName;
            if (parent.Parent is not null)
            {
                yield return parent.Parent.FullName;
            }
        }
    }
}