using System.Globalization;
using System.IO;

namespace EmbyToolbox.Services;

/// <summary>Единый каталог <c>extract\audio|subtitles|attachments</c> и имена без молчаливого перезаписывания.</summary>
public static class TrackExtractOutputPaths
{
    /// <returns>Абсолютный путь к каталогу <c>…\extract</c> или null.</returns>
    public static string? TryPrepareExtractDirectories(string destinationRootFolder)
    {
        if (string.IsNullOrWhiteSpace(destinationRootFolder))
        {
            return null;
        }

        try
        {
            var root = Path.GetFullPath(destinationRootFolder.Trim());
            var extractRoot = Path.Combine(root, "extract");
            Directory.CreateDirectory(Path.Combine(extractRoot, "audio"));
            Directory.CreateDirectory(Path.Combine(extractRoot, "subtitles"));
            Directory.CreateDirectory(Path.Combine(extractRoot, "attachments"));
            return extractRoot;
        }
        catch (ArgumentException)
        {
            return null;
        }
        catch (IOException)
        {
            return null;
        }
        catch (UnauthorizedAccessException)
        {
            return null;
        }
    }

    /// <summary>Если в <paramref name="parentDirectory"/> уже есть файл с таким именем — добавляет <c>_1</c>, <c>_2</c>… перед расширением.</summary>
    public static string AllocateUniqueFilename(string parentDirectory, string desiredFileNameOnly)
    {
        var safe = Path.GetFileName(desiredFileNameOnly);
        if (string.IsNullOrEmpty(safe))
        {
            safe = "output.bin";
        }

        if (!Exists(parentDirectory, safe))
        {
            return safe;
        }

        var stem = Path.GetFileNameWithoutExtension(safe);
        var ext = Path.GetExtension(safe);

        if (string.IsNullOrEmpty(stem))
        {
            stem = "file";
        }

        for (var i = 1; i < 10_000; i++)
        {
            var candidate = $"{stem}_{i.ToString(CultureInfo.InvariantCulture)}{ext}";
            if (!Exists(parentDirectory, candidate))
            {
                return candidate;
            }
        }

        return $"{stem}_{Guid.NewGuid():N}{ext}";
    }

    private static bool Exists(string parentDirectory, string fileNameOnly) =>
        File.Exists(Path.Combine(parentDirectory, fileNameOnly));
}