using Aliyun.OSS;

namespace WenChuanyi.Api.Services;

/// <summary>OSS 存储服务：对象键构造、流式上传/下载/删除（后端中转，前端不接触凭据）</summary>
public class OssStorageService
{
    private readonly OssClient _client;
    private readonly string _bucket;
    private readonly string _baseKey;
    private readonly ILogger<OssStorageService> _logger;

    public OssStorageService(IConfiguration cfg, ILogger<OssStorageService> logger)
    {
        var endpoint = cfg["Oss:Endpoint"] ?? throw new InvalidOperationException("缺少配置 Oss:Endpoint");
        var ak = cfg["Oss:AccessKeyId"] ?? throw new InvalidOperationException("缺少配置 Oss:AccessKeyId");
        var sk = cfg["Oss:AccessKeySecret"] ?? throw new InvalidOperationException("缺少配置 Oss:AccessKeySecret");
        _bucket = cfg["Oss:Bucket"] ?? throw new InvalidOperationException("缺少配置 Oss:Bucket");
        _baseKey = cfg["Oss:BaseKey"] ?? "文传易2026";
        _client = new OssClient(endpoint, ak, sk);
        _logger = logger;
    }

    /// <summary>构造对象键：文传易2026/{yyyyMM}/{Guid}{ext}（按上传月份建子目录）</summary>
    public string BuildObjectKey(string originalName)
    {
        var month = DateTime.Now.ToString("yyyyMM");
        var ext = Path.GetExtension(originalName).ToLowerInvariant();
        return $"{_baseKey}/{month}/{Guid.NewGuid():N}{ext}";
    }

    /// <summary>流式上传（不落本地、不整体读内存）。ContentType 会去除参数部分（如 ";charset=utf-8"），
    /// 因为 OSS SDK 对带参数的 Content-Type 签名会与服务端校验不一致，导致 403 签名不匹配。</summary>
    public async Task UploadAsync(string objectKey, Stream stream, string contentType)
    {
        var safeContentType = (contentType ?? "application/octet-stream").Split(';')[0].Trim();
        if (string.IsNullOrEmpty(safeContentType)) safeContentType = "application/octet-stream";
        var req = new PutObjectRequest(_bucket, objectKey, stream);
        req.Metadata = new ObjectMetadata { ContentType = safeContentType };
        await Task.Run(() => _client.PutObject(req)).ConfigureAwait(false);
    }

    /// <summary>获取对象（支持 Range；end 为 -1 表示到文件末尾）</summary>
    public OssObject GetObject(string objectKey, long? start = null, long? end = null)
    {
        var req = new GetObjectRequest(_bucket, objectKey);
        if (start.HasValue || end.HasValue)
        {
            req.SetRange(start ?? 0, end ?? -1);
        }
        return _client.GetObject(req);
    }

    /// <summary>删除对象（失败不抛出，由调用方记录日志）</summary>
    public bool TryDeleteObject(string objectKey)
    {
        try
        {
            _client.DeleteObject(_bucket, objectKey);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "OSS 对象删除失败：{ObjectKey}", objectKey);
            return false;
        }
    }
}