using System.Net;
using Aliyun.OSS;

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>打开文件流供读取（OSS 模式下用于私有桶代理访问），不存在返回 null</summary>
    Task<(Stream Stream, string ContentType)?> OpenReadAsync(string key);

    /// <summary>生成临时访问 URL（仅 OSS 模式支持），本地存储返回 null</summary>
    string? GeneratePresignedUrl(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;
    }

    public Task<(Stream Stream, string ContentType)?> OpenReadAsync(string key)
    {
        if (string.IsNullOrWhiteSpace(key) || !key.StartsWith("/uploads/"))
            return Task.FromResult<(Stream, string)?>(null);
        var full = Path.Combine(_root, key.TrimStart('/').Replace('/', Path.DirectorySeparatorChar));
        if (!File.Exists(full)) return Task.FromResult<(Stream, string)?>(null);
        var contentType = _contentTypes[Path.GetExtension(full)] ?? "application/octet-stream";
        return Task.FromResult<(Stream, string)?>((File.OpenRead(full), contentType));
    }

    /// <summary>本地存储无公开 URL，返回 null（OCR 会回退 base64 方式）</summary>
    public string? GeneratePresignedUrl(string key) => null;

    private static readonly Dictionary<string, string> _contentTypes = new(StringComparer.OrdinalIgnoreCase)
    {
        [".jpg"] = "image/jpeg", [".jpeg"] = "image/jpeg", [".png"] = "image/png",
        [".gif"] = "image/gif", [".webp"] = "image/webp", [".bmp"] = "image/bmp",
    };
}

/// <summary>
/// 阿里云 OSS 存储。配置见 appsettings.json 的 Oss 节点（AccessKeyId / AccessKeySecret / Endpoint / Bucket）；
/// 未配置时调用会抛出 InvalidOperationException，由接口统一转为友好提示。
/// </summary>
public sealed class OssFileStorage(IConfiguration cfg) : IFileStorage
{
    private readonly OssClient? _client = CreateClient(cfg);
    private readonly string? _bucket = cfg["Oss:Bucket"];

    /// <summary>配置完整（AccessKeyId / AccessKeySecret / Endpoint / Bucket 均非空）时才能创建客户端</summary>
    private static OssClient? CreateClient(IConfiguration cfg)
    {
        var id = cfg["Oss:AccessKeyId"];
        var secret = cfg["Oss:AccessKeySecret"];
        var endpoint = cfg["Oss:Endpoint"];
        var bucket = cfg["Oss:Bucket"];
        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(secret)
            || string.IsNullOrWhiteSpace(endpoint) || string.IsNullOrWhiteSpace(bucket))
            return null;
        return new OssClient(endpoint, id, secret);
    }

    public bool IsConfigured => _client != null;

    /// <summary>
    /// 上传到 OSS，返回 StoredFile。
    /// Key 使用 "uploads/{subDir}/{yyyyMM}/{guid}{ext}"（OSS 对象键不带前导斜杠）。
    /// URL 返回后端代理相对路径 /api/files/{key}，由 FilesController 实时从私有桶拉流返回，
    /// 保证 Bucket 可保持私有（身份证等敏感信息不暴露公网）。
    /// </summary>
    public Task<StoredFile> SaveAsync(string subDir, Stream stream, string fileName, string contentType)
    {
        if (_client is null || string.IsNullOrWhiteSpace(_bucket))
            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");

        var dateDir = DateTime.Now.ToString("yyyyMM");
        var ext = Path.GetExtension(fileName);
        if (string.IsNullOrWhiteSpace(ext) || ext.Length > 10) ext = ".jpg";
        var key = $"uploads/{subDir}/{dateDir}/{Guid.NewGuid():N}{ext}";

        var metadata = new ObjectMetadata { ContentType = contentType };
        _client.PutObject(_bucket, key, stream, metadata);

        return Task.FromResult(new StoredFile(key, $"/api/files/{key}"));
    }

    /// <summary>按 key 删除 OSS 对象（兼容本地存储带前导斜杠的 key 格式）</summary>
    public Task DeleteAsync(string key)
    {
        if (_client is null || string.IsNullOrWhiteSpace(_bucket)) return Task.CompletedTask;
        if (string.IsNullOrWhiteSpace(key)) return Task.CompletedTask;
        try
        {
            var objectKey = key.StartsWith('/') ? key.TrimStart('/') : key;
            if (objectKey.StartsWith("uploads/"))
                _client.DeleteObject(_bucket, objectKey);
        }
        catch
        {
            // 忽略删除失败
        }
        return Task.CompletedTask;
    }

    /// <summary>从私有桶拉取对象流（供代理接口使用），不存在返回 null</summary>
    public Task<(Stream Stream, string ContentType)?> OpenReadAsync(string key)
    {
        if (_client is null || string.IsNullOrWhiteSpace(_bucket)) return Task.FromResult<(Stream, string)?>(null);
        var objectKey = key.StartsWith('/') ? key.TrimStart('/') : key;
        if (!objectKey.StartsWith("uploads/")) return Task.FromResult<(Stream, string)?>(null);
        try
        {
            var obj = _client.GetObject(_bucket, objectKey);
            var contentType = obj.Metadata.ContentType ?? "application/octet-stream";
            return Task.FromResult<(Stream, string)?>((obj.Content, contentType));
        }
        catch (Exception ex) when (ex is Aliyun.OSS.Common.OssException or WebException or System.Net.Http.HttpRequestException)
        {
            return Task.FromResult<(Stream, string)?>(null);
        }
    }

    /// <summary>生成 10 分钟有效的私有桶临时访问 URL（供 OCR 等第三方服务拉取图片），失败返回 null</summary>
    public string? GeneratePresignedUrl(string key)
    {
        if (_client is null || string.IsNullOrWhiteSpace(_bucket)) return null;
        var objectKey = key.StartsWith('/') ? key.TrimStart('/') : key;
        if (!objectKey.StartsWith("uploads/")) return null;
        try
        {
            return _client.GeneratePresignedUri(_bucket, objectKey, DateTime.Now.AddMinutes(10)).ToString();
        }
        catch
        {
            return null;
        }
    }
}