F8WebAI/backend/AgriculturalPlatform.Api/Services/FileStorage.cs

namespace AgriculturalPlatform.Api.Services;

/// <summary>已保存文件的存储 key 与访问地址</summary>
public record StoredFile(string Key, string Url);

/// <summary>
/// 附件文件存储抽象。
/// 当前默认实现为本地存储（wwwroot/uploads）；
/// 阿里云 OSS 授权验证配置好后（appsettings.json 的 Oss 节点），
/// 将 Storage:UseOss 设为 true 即可切换到 OSS。
/// </summary>
public interface IFileStorage
{
    /// <summary>保存文件，返回存储 key 与访问 URL</summary>
    Task<StoredFile> SaveAsync(string subDir, Stream stream, string fileName, string contentType);

    /// <summary>按 key 删除文件（本地/OSS 通用）</summary>
    Task DeleteAsync(string key);
}

/// <summary>本地磁盘存储（wwwroot/uploads），URL 即相对路径，由静态文件中间件直接访问</summary>
public sealed class LocalFileStorage(IWebHostEnvironment env) : IFileStorage
{
    private readonly string _root = Path.Combine(
        env.WebRootPath ?? Path.Combine(env.ContentRootPath, "wwwroot"), "uploads");

    public async Task<StoredFile> SaveAsync(string subDir, Stream stream, string fileName, string contentType)
    {
        var dateDir = DateTime.Now.ToString("yyyyMM");
        var dir = Path.Combine(_root, subDir, dateDir);
        Directory.CreateDirectory(dir);

        var ext = Path.GetExtension(fileName);
        if (string.IsNullOrWhiteSpace(ext)) ext = ".jpg";
        if (ext.Length > 10) ext = ".jpg";
        var name = $"{Guid.NewGuid():N}{ext}";
        var full = Path.Combine(dir, name);

        await using var fs = File.Create(full);
        await stream.CopyToAsync(fs);

        var key = $"/uploads/{subDir}/{dateDir}/{name}";
        return new StoredFile(key, key);
    }

    public Task DeleteAsync(string key)
    {
        if (string.IsNullOrWhiteSpace(key) || !key.StartsWith("/uploads/")) return Task.CompletedTask;
        try
        {
            var full = Path.Combine(_root, key.TrimStart('/').Replace('/', Path.DirectorySeparatorChar));
            if (File.Exists(full)) File.Delete(full);
        }
        catch
        {
            // 忽略删除失败
        }
        return Task.CompletedTask;
    }
}

/// <summary>
/// 阿里云 OSS 存储。授权验证（AccessKeyId/Secret、Endpoint、Bucket）后期配置提供；
/// 未配置前调用会抛出 InvalidOperationException，由接口统一转为友好提示。
/// </summary>
public sealed class OssFileStorage(IConfiguration cfg) : IFileStorage
{
    public bool IsConfigured =>
        !string.IsNullOrWhiteSpace(cfg["Oss:AccessKeyId"])
        && !string.IsNullOrWhiteSpace(cfg["Oss:AccessKeySecret"])
        && !string.IsNullOrWhiteSpace(cfg["Oss:Bucket"]);

    public Task<StoredFile> SaveAsync(string subDir, Stream stream, string fileName, string contentType)
        => throw new InvalidOperationException(
            "阿里云 OSS 尚未配置授权验证，请在 appsettings.json 的 Oss 节点填写 AccessKeyId / AccessKeySecret / Endpoint / Bucket 后重启服务");

    public Task DeleteAsync(string key)
        => throw new InvalidOperationException("阿里云 OSS 尚未配置授权验证，暂不支持删除");
}