package oss

import (
	"bytes"
	"context"
	"fmt"
	"sync"
	"time"

	"goalfymax-admin/internal/config"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/credentials"
	"github.com/aws/aws-sdk-go-v2/service/s3"
)

type s3Client struct {
	client  *s3.Client
	presign *s3.PresignClient
	cfg     config.OssConfig
}

var (
	clientOnce sync.Once
	c          *s3Client
)

func initClient() error {
	var initErr error
	clientOnce.Do(func() {
		cfg := config.GetConfig().Oss
		if cfg.Region == "" || cfg.Bucket == "" || cfg.AccessKeyID == "" || cfg.AccessKeySecret == "" {
			initErr = fmt.Errorf("OSS未配置: region/bucket/ak/sk 不能为空")
			return
		}

		awsCfg := aws.Config{
			Region:      cfg.Region,
			Credentials: credentials.NewStaticCredentialsProvider(cfg.AccessKeyID, cfg.AccessKeySecret, ""),
		}

		// 如果配置了自定义 endpoint (如阿里云 OSS),则设置 endpoint resolver
		if cfg.Endpoint != "" {
			awsCfg.BaseEndpoint = aws.String("https://" + cfg.Endpoint)
		}

		// 创建 S3 客户端,使用虚拟主机样式(阿里云 OSS 要求)
		s3c := s3.NewFromConfig(awsCfg, func(o *s3.Options) {
			// 阿里云 OSS 使用虚拟主机样式: bucket.endpoint/key
			// AWS S3 默认也是虚拟主机样式,所以保持 UsePathStyle = false (默认值)
			o.UsePathStyle = false
		})

		c = &s3Client{
			client:  s3c,
			presign: s3.NewPresignClient(s3c),
			cfg:     cfg,
		}
	})
	return initErr
}

// GetPresignedGetURL 生成S3对象的预签名下载URL
func GetPresignedGetURL(ctx context.Context, key string) (string, error) {
	if err := initClient(); err != nil {
		return "", err
	}
	expire := c.cfg.PresignUrlExpire
	if expire <= 0 {
		expire = 10 * time.Minute
	}
	req, err := c.presign.PresignGetObject(ctx, &s3.GetObjectInput{
		Bucket: aws.String(c.cfg.Bucket),
		Key:    aws.String(key),
	}, func(po *s3.PresignOptions) {
		po.Expires = expire
	})
	if err != nil {
		return "", fmt.Errorf("生成预签名URL失败: %w", err)
	}
	return req.URL, nil
}

// DownloadFileContent 从S3下载文件内容和MIME类型
func DownloadFileContent(ctx context.Context, key string) ([]byte, string, error) {
	if err := initClient(); err != nil {
		return nil, "", err
	}

	resp, err := c.client.GetObject(ctx, &s3.GetObjectInput{
		Bucket: aws.String(c.cfg.Bucket),
		Key:    aws.String(key),
	})
	if err != nil {
		return nil, "", fmt.Errorf("从S3下载文件失败: %w", err)
	}
	defer resp.Body.Close()

	buf := new(bytes.Buffer)
	_, err = buf.ReadFrom(resp.Body)
	if err != nil {
		return nil, "", fmt.Errorf("读取文件内容失败: %w", err)
	}

	mimeType := "application/octet-stream" // 默认MIME类型
	if resp.ContentType != nil && *resp.ContentType != "" {
		mimeType = *resp.ContentType
	}

	return buf.Bytes(), mimeType, nil
}