using Dpz.Core.Infrastructure;

namespace Dpz.Core.Service.ObjectStorage;

/// <summary>
/// COS/S3 对象存储配置
/// </summary>
public class S3ObjectStorageOptions
{
    /// <summary>
    /// 腾讯云 COS 的 S3 兼容访问端点，例如：https://cos.ap-guangzhou.myqcloud.com
    /// </summary>
    public string? Endpoint { get; set; }

    /// <summary>
    /// 腾讯云访问密钥 SecretId
    /// </summary>
    public string? SecretId { get; set; }

    /// <summary>
    /// 腾讯云访问密钥 SecretKey
    /// </summary>
    public string? SecretKey { get; set; }

    /// <summary>
    /// COS 存储桶完整名称，格式通常为 bucket-name-appid
    /// </summary>
    public string? Bucket { get; set; }

    /// <summary>
    /// 文件对外访问域名，可配置为 CDN 域名或 COS 公开访问域名
    /// </summary>
    public string? CdnHost { get; set; }

    /// <summary>
    /// COS 地域，例如 ap-guangzhou；未配置时会从 <see cref="Endpoint"/> 中推断
    /// </summary>
    public string? Region { get; set; }

    /// <summary>
    /// 获取已经校验并补齐默认值的配置
    /// </summary>
    /// <exception cref="InvalidConfigurationException">配置缺失或格式无效</exception>
    public S3ObjectStorageOptions Validate()
    {
        Endpoint = Require(Endpoint, nameof(Endpoint)).TrimEnd('/');
        SecretId = Require(SecretId, nameof(SecretId));
        SecretKey = Require(SecretKey, nameof(SecretKey));
        Bucket = Require(Bucket, nameof(Bucket));
        CdnHost = Require(CdnHost, nameof(CdnHost)).TrimEnd('/');
        Region = string.IsNullOrWhiteSpace(Region) ? InferRegion(Endpoint) : Region.Trim();

        return this;
    }

    private static string Require(string? value, string name)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            throw new InvalidConfigurationException($"S3:{name} configuration is missing");
        }

        return value.Trim();
    }

    private static string InferRegion(string endpoint)
    {
        if (!Uri.TryCreate(endpoint, UriKind.Absolute, out var uri))
        {
            throw new InvalidConfigurationException("S3:Endpoint configuration is invalid");
        }

        var parts = uri.Host.Split('.', StringSplitOptions.RemoveEmptyEntries);
        var cosIndex = Array.FindIndex(
            parts,
            x => x.Equals("cos", StringComparison.OrdinalIgnoreCase)
        );
        if (cosIndex < 0 || cosIndex + 1 >= parts.Length)
        {
            throw new InvalidConfigurationException("S3:Region configuration is missing");
        }

        return parts[cosIndex + 1];
    }
}