using System.Text.RegularExpressions;

namespace MatrixImageEditor;

internal static partial class ImagePathRules
{
    public static string ValidateExistingImage(string imagePath)
    {
        var fullPath = ValidateImageNameAndDirectory(imagePath);
        if (!File.Exists(fullPath)) throw new FileNotFoundException("镜像文件不存在", fullPath);
        if (Directory.Exists(fullPath + ".sha256")) throw new IOException("同名 SHA-256 摘要路径被文件夹占用");
        return fullPath;
    }

    public static string ValidateNewDestination(string sourcePath, string destinationPath)
    {
        var source = ValidateExistingImage(sourcePath);
        var destination = ValidateImageNameAndDirectory(destinationPath);
        if (destination.Equals(source, StringComparison.OrdinalIgnoreCase)) throw new ArgumentException("另存为必须使用与原镜像不同的文件名");
        if (File.Exists(destination) || Directory.Exists(destination)) throw new IOException("目标镜像已经存在，请使用新的文件名");

        var sidecar = destination + ".sha256";
        if (File.Exists(sidecar) || Directory.Exists(sidecar)) throw new IOException("目标镜像的同名 SHA-256 摘要已经存在，请使用新的文件名");
        return destination;
    }

    public static string? CleanupNewDestination(string destinationPath)
    {
        List<string>? failures = null;
        foreach (var target in new[] { destinationPath + ".sha256", destinationPath })
        {
            try
            {
                if (File.Exists(target)) File.Delete(target);
            }
            catch (Exception exception)
            {
                failures ??= new List<string>();
                failures.Add($"{Path.GetFileName(target)}：{exception.Message}");
            }
        }
        return failures is null ? null : string.Join("；", failures);
    }

    private static string ValidateImageNameAndDirectory(string imagePath)
    {
        if (string.IsNullOrWhiteSpace(imagePath)) throw new ArgumentException("镜像路径不能为空");

        string fullPath;
        try
        {
            fullPath = Path.GetFullPath(imagePath);
        }
        catch (Exception exception) when (exception is ArgumentException or NotSupportedException or PathTooLongException)
        {
            throw new ArgumentException("镜像路径格式无效", exception);
        }

        var fileName = Path.GetFileName(fullPath);
        if (string.IsNullOrWhiteSpace(fileName)) throw new ArgumentException("镜像文件名不能为空");
        if (fileName.IndexOfAny(Path.GetInvalidFileNameChars()) >= 0 || fileName != fileName.TrimEnd(' ', '.'))
        {
            throw new ArgumentException("镜像文件名包含 Windows 不允许的字符，或以空格、句点结尾");
        }
        if (!Path.GetExtension(fileName).Equals(".img", StringComparison.OrdinalIgnoreCase)) throw new ArgumentException("镜像文件名必须以 .img 结尾");
        if (ReservedWindowsName().IsMatch(Path.GetFileNameWithoutExtension(fileName))) throw new ArgumentException("镜像文件名使用了 Windows 保留名称，请更换名称");

        var directory = Path.GetDirectoryName(fullPath);
        if (string.IsNullOrEmpty(directory) || !Directory.Exists(directory)) throw new DirectoryNotFoundException("镜像目标文件夹不存在");
        return fullPath;
    }

    [GeneratedRegex("^(CON|PRN|AUX|NUL|COM[1-9]|LPT[1-9])(?:\\..*)?$", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex ReservedWindowsName();
}