namespace Dpz.Core.Service.ObjectStorage;

/// <summary>
/// COS 对象 Key 与公开访问 URL 的统一转换工具
/// </summary>
internal static class S3ObjectKeyHelper
{
    /// <summary>
    /// 根据目录段和文件名生成对象 Key
    /// </summary>
    public static string BuildKey(IEnumerable<string> path, string filename)
    {
        if (string.IsNullOrWhiteSpace(filename))
        {
            throw new ArgumentNullException(nameof(filename));
        }

        var segments = path.SelectMany(SplitPath).ToList();
        segments.AddRange(SplitPath(filename));
        return BuildKey(segments);
    }

    /// <summary>
    /// 根据已经包含文件名的路径段生成对象 Key
    /// </summary>
    public static string BuildKey(IEnumerable<string> pathToFile)
    {
        var segments = pathToFile.SelectMany(SplitPath).ToList();
        return segments.Count == 0
            ? throw new ArgumentException("对象路径不能为空", nameof(pathToFile))
            : string.Join("/", segments);
    }

    /// <summary>
    /// 从相对路径或完整 URL 中还原 COS 对象 Key
    /// </summary>
    public static string NormalizeKey(string pathToFile)
    {
        if (string.IsNullOrWhiteSpace(pathToFile))
        {
            throw new ArgumentNullException(nameof(pathToFile));
        }

        var path = pathToFile.Trim();
        if (Uri.TryCreate(path, UriKind.Absolute, out var uri))
        {
            path = uri.AbsolutePath;
        }

        path = path.TrimStart('/');
        path = Uri.UnescapeDataString(path);
        return BuildKey([path]);
    }

    /// <summary>
    /// 把目录路径转换成 ListObjectsV2 可用的 Prefix
    /// </summary>
    public static string NormalizeDirectoryPrefix(string path)
    {
        ArgumentNullException.ThrowIfNull(path);

        var value = path.Trim();
        if (value is "" or "/")
        {
            return string.Empty;
        }

        value = Uri.TryCreate(value, UriKind.Absolute, out var uri)
            ? Uri.UnescapeDataString(uri.AbsolutePath)
            : Uri.UnescapeDataString(value);

        value = value.Trim('/');
        return string.IsNullOrWhiteSpace(value) ? string.Empty : value + "/";
    }

    /// <summary>
    /// 生成对象的公开访问 URL
    /// </summary>
    public static string BuildAccessUrl(string cdnHost, string key)
    {
        if (string.IsNullOrWhiteSpace(cdnHost))
        {
            throw new ArgumentNullException(nameof(cdnHost));
        }

        var encodedKey = string.Join(
            "/",
            NormalizeKey(key).Split('/').Select(Uri.EscapeDataString)
        );
        return $"{cdnHost.TrimEnd('/')}/{encodedKey}";
    }

    /// <summary>
    /// 取指定 Prefix 下一级目录或文件的显示名称
    /// </summary>
    public static string GetDisplayName(string keyOrPrefix, string parentPrefix)
    {
        var value = keyOrPrefix;
        if (!string.IsNullOrEmpty(parentPrefix) && value.StartsWith(parentPrefix))
        {
            value = value[parentPrefix.Length..];
        }

        return value.Trim('/').Split('/').FirstOrDefault() ?? string.Empty;
    }

    /// <summary>
    /// 组合远程目录和相对文件路径
    /// </summary>
    public static string CombineRemotePath(string remoteDirectory, string relativeFilePath)
    {
        var prefix = NormalizeDirectoryPrefix(remoteDirectory);
        var key = NormalizeKey(relativeFilePath.Replace(Path.DirectorySeparatorChar, '/'));
        return prefix + key;
    }

    private static IEnumerable<string> SplitPath(string path)
    {
        if (string.IsNullOrWhiteSpace(path))
        {
            yield break;
        }

        foreach (
            var segment in path.Split(
                ['/', '\\'],
                StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries
            )
        )
        {
            yield return Uri.UnescapeDataString(segment);
        }
    }
}