media/service/video/concat_service.go

package video

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	dao "media/dao/video"
	dto "media/model/dto/video"
	entity "media/model/entity/video"

	"gitea.com/red-future/common/beans"
	commonHttp "gitea.com/red-future/common/http"

	"github.com/gogf/gf/v2/frame/g"
	"github.com/gogf/gf/v2/os/glog"
	"github.com/gogf/gf/v2/util/guid"
)

type concatService struct{}

// Concat 视频拼接服务单例
var Concat = new(concatService)

// ConcatReq 视频拼接请求
type ConcatReq struct {
	VideoPaths []string // 视频文件路径列表（按此顺序拼接）
	OutputPath string   // 输出视频文件路径，空则自动生成
	Method     string   // 拼接方式: auto/fast/reencode，默认 auto
	Upload     bool     // 是否上传到MinIO
}

// ConcatRes 视频拼接响应
type ConcatRes struct {
	OutputPath  string  `json:"outputPath"`  // 输出文件路径
	FileSize    int64   `json:"fileSize"`    // 文件大小(bytes)
	Duration    float64 `json:"duration"`    // 拼接后总时长(秒)
	DurationStr string  `json:"durationStr"` // 可读时长
	MethodUsed  string  `json:"methodUsed"`  // 实际使用的拼接方式
	InputFiles  int     `json:"inputFiles"`  // 输入文件数
	FileURL     string  `json:"fileURL"`     // MinIO访问地址（上传后返回）
}

// Concat 拼接多个视频为一个
func (s *concatService) Concat(ctx context.Context, req *ConcatReq) (res *ConcatRes, err error) {
	g.Log().Infof(ctx, "[Concat] 服务层收到请求: videoPaths=%v, method=%s, upload=%v",
		req.VideoPaths, req.Method, req.Upload)

	if len(req.VideoPaths) < 2 {
		return nil, fmt.Errorf("至少需要2个视频才能拼接")
	}

	// 校验所有视频文件存在
	for i, p := range req.VideoPaths {
		if _, err := os.Stat(p); os.IsNotExist(err) {
			return nil, fmt.Errorf("第%d个视频文件不存在: %s", i+1, p)
		}
	}

	ffmpegPath, err := s.getFFmpegPath()
	if err != nil {
		return nil, err
	}

	// 生成输出路径
	outputPath := req.OutputPath
	if outputPath == "" {
		outputDir := filepath.Dir(req.VideoPaths[0])
		// 用第一个输入文件名 + 拼接数 + 时间戳，溯源更清晰
		baseName := filepath.Base(req.VideoPaths[0])
		ext := filepath.Ext(baseName)
		stem := strings.TrimSuffix(baseName, ext)
		stemRunes := []rune(stem)
		if len(stemRunes) > 20 {
			stemRunes = stemRunes[:20]
		}
		outputPath = filepath.Join(outputDir,
			fmt.Sprintf("concat_%s_x%d_%s%s", string(stemRunes), len(req.VideoPaths), time.Now().Format("150405"), ext))
	}

	method := req.Method
	if method == "" {
		method = "auto"
	}

	var methodUsed string

	switch method {
	case "fast":
		// 无损拼接（要求同编码参数，速度快但可能黑屏）
		err = s.concatByDemuxer(ctx, ffmpegPath, req.VideoPaths, outputPath)
		methodUsed = "concat demuxer (无损)"
	default:
		// 重编码拼接（自动归一化分辨率/音频，兼容所有视频）
		err = s.concatByFilter(ctx, ffmpegPath, req.VideoPaths, outputPath)
		methodUsed = "concat filter (重编码)"
	}

	if err != nil {
		return nil, fmt.Errorf("视频拼接失败: %v", err)
	}

	// 获取输出文件信息
	stat, statErr := os.Stat(outputPath)
	if statErr != nil {
		return nil, fmt.Errorf("输出文件异常: %v", statErr)
	}

	// 获取时长
	duration, _ := s.getVideoDuration(ctx, ffmpegPath, outputPath)

	res = &ConcatRes{
		OutputPath:  outputPath,
		FileSize:    stat.Size(),
		Duration:    duration,
		DurationStr: formatDuration(duration),
		MethodUsed:  methodUsed,
		InputFiles:  len(req.VideoPaths),
	}

	// 如果需要上传到 MinIO（用独立 context，避免 HTTP 断开后 ctx 被取消）
	if req.Upload {
		uploadCtx := context.Background()
		uploadRes, uploadErr := s.UploadToMinIO(uploadCtx, outputPath)
		if uploadErr != nil {
			return nil, fmt.Errorf("上传到MinIO失败: %v", uploadErr)
		}
		res.FileURL = uploadRes.FileURL
	}

	return
}

// concatByDemuxer 使用 concat demuxer 无损拼接（要求同编码参数）
func (s *concatService) concatByDemuxer(ctx context.Context, ffmpegPath string, inputs []string, output string) error {
	// 创建文件列表
	fileListPath := filepath.Join(filepath.Dir(output), "concat_list.txt")
	var lines []string
	for _, p := range inputs {
		lines = append(lines, fmt.Sprintf("file '%s'", p))
	}
	if err := os.WriteFile(fileListPath, []byte(strings.Join(lines, "\n")+"\n"), 0644); err != nil {
		return fmt.Errorf("创建文件列表失败: %v", err)
	}
	defer os.Remove(fileListPath)

	args := []string{
		"-f", "concat",
		"-safe", "0",
		"-i", fileListPath,
		"-c", "copy", // 直接复制流，不重编码
		"-y",
		output,
	}

	// 使用独立 context，避免 HTTP 请求超时导致 ffmpeg 被 SIGKILL
	bgCtx := context.Background()
	cmd := exec.CommandContext(bgCtx, ffmpegPath, args...)
	outputBytes, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("ffmpeg demuxer 失败: %v\n%s", err, string(outputBytes))
	}
	return nil
}

// concatByFilter 使用 concat filter 重编码拼接（自动归一化分辨率/音频参数）
func (s *concatService) concatByFilter(ctx context.Context, ffmpegPath string, inputs []string, output string) error {
	n := len(inputs)

	// 1. 获取所有视频的分辨率，确定统一输出尺寸
	maxW, maxH := 0, 0
	var inputMeta []struct{ w, h int }
	for _, p := range inputs {
		w, h, _ := s.getVideoResolution(ctx, ffmpegPath, p)
		inputMeta = append(inputMeta, struct{ w, h int }{w, h})
		if w > maxW {
			maxW = w
		}
		if h > maxH {
			maxH = h
		}
	}
	// 保底
	if maxW == 0 {
		maxW = 1920
	}
	if maxH == 0 {
		maxH = 1080
	}

	// 2. 构建输入参数
	var inputArgs []string
	for _, p := range inputs {
		inputArgs = append(inputArgs, "-i", p)
	}

	// 3. 构建 filter_complex：每个视频 scale+pad 到统一尺寸，然后 concat
	var filterParts []string
	for i := 0; i < n; i++ {
		filterParts = append(filterParts, fmt.Sprintf(
			"[%d:v]scale=%d:%d:force_original_aspect_ratio=decrease,pad=%d:%d:(ow-iw)/2:(oh-ih)/2,setsar=1,fps=30[v%d]",
			i, maxW, maxH, maxW, maxH, i,
		))
		filterParts = append(filterParts, fmt.Sprintf(
			"[%d:a]aresample=44100[a%d]",
			i, i,
		))
	}
	// 收集归一化后的流
	var concatInputs []string
	for i := 0; i < n; i++ {
		concatInputs = append(concatInputs, fmt.Sprintf("[v%d][a%d]", i, i))
	}
	filterStr := fmt.Sprintf("%s;%sconcat=n=%d:v=1:a=1[outv][outa]",
		strings.Join(filterParts, ";"),
		strings.Join(concatInputs, ""), n)

	outputDir := filepath.Dir(output)
	args := append(inputArgs,
		"-filter_complex", filterStr,
		"-map", "[outv]",
		"-map", "[outa]",
		"-preset", "fast",
		"-crf", "23",
		"-y",
		output,
	)

	// 调试：记录完整命令
	g.Log().Debugf(ctx, "concat filter 命令: %s %v", ffmpegPath, args)

	// 保存 filter graph 用于调试
	filterFile := filepath.Join(outputDir, "concat_filter.txt")
	os.WriteFile(filterFile, []byte(filterStr), 0644)
	defer os.Remove(filterFile)

	// 使用独立 context，避免 HTTP 请求超时导致 ffmpeg 被 SIGKILL
	bgCtx := context.Background()
	cmd := exec.CommandContext(bgCtx, ffmpegPath, args...)
	outputBytes, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("ffmpeg filter 失败: %v\n日志:\n%s", err, string(outputBytes))
	}
	return nil
}

// getVideoResolution 获取视频分辨率
func (s *concatService) getVideoResolution(ctx context.Context, ffmpegPath, videoPath string) (width, height int, err error) {
	ffprobePath := filepath.Join(filepath.Dir(ffmpegPath), "ffprobe")
	if _, err := os.Stat(ffprobePath); os.IsNotExist(err) {
		ffprobePath = "ffprobe"
	}

	cmd := exec.CommandContext(ctx, ffprobePath,
		"-v", "error",
		"-select_streams", "v:0",
		"-show_entries", "stream=width,height",
		"-of", "csv=p=0",
		videoPath,
	)
	output, err := cmd.Output()
	if err != nil {
		return 0, 0, err
	}
	fmt.Sscanf(strings.TrimSpace(string(output)), "%d,%d", &width, &height)
	return
}

// getVideoDuration 获取视频时长
func (s *concatService) getVideoDuration(ctx context.Context, ffmpegPath, videoPath string) (float64, error) {
	ffprobePath := filepath.Join(filepath.Dir(ffmpegPath), "ffprobe")
	if _, err := os.Stat(ffprobePath); os.IsNotExist(err) {
		ffprobePath = "ffprobe"
	}

	cmd := exec.CommandContext(ctx, ffprobePath,
		"-v", "error",
		"-show_entries", "format=duration",
		"-of", "default=noprint_wrappers=1:nokey=1",
		videoPath,
	)

	output, err := cmd.Output()
	if err != nil {
		return 0, err
	}

	var duration float64
	fmt.Sscanf(strings.TrimSpace(string(output)), "%f", &duration)
	return duration, nil
}

func (s *concatService) getFFmpegPath() (string, error) {
	ffmpegPath := g.Cfg().MustGet(context.Background(), "ffmpeg.path", "").String()
	if ffmpegPath != "" {
		if _, err := os.Stat(ffmpegPath); err == nil {
			return ffmpegPath, nil
		}
	}
	path, err := exec.LookPath("ffmpeg")
	if err != nil {
		return "", fmt.Errorf("未找到 ffmpeg")
	}
	return path, nil
}

func formatDuration(seconds float64) string {
	h := int(seconds) / 3600
	m := (int(seconds) % 3600) / 60
	s := int(seconds) % 60
	return fmt.Sprintf("%02d:%02d:%02d", h, m, s)
}

// uploadFileRes 上传文件响应
type uploadFileRes struct {
	FileURL           string `json:"fileURL" dc:"上传地址"`
	FileSize          int    `json:"fileSize" dc:"文件大小"`
	FileName          string `json:"fileName" dc:"文件名称"`
	FileFormat        string `json:"fileFormat" dc:"文件格式"`
	FileAddressPrefix string `json:"fileAddressPrefix"`
}

// UploadToMinIO 通过 OSS 微服务的 uploadFile 接口上传到 MinIO（multipart/form-data）
func (s *concatService) UploadToMinIO(ctx context.Context, localFilePath string) (*uploadFileRes, error) {
	// 构建 multipart/form-data 表单
	var buf bytes.Buffer
	mw := multipart.NewWriter(&buf)

	file, err := os.Open(localFilePath)
	if err != nil {
		return nil, fmt.Errorf("打开文件失败: %v", err)
	}
	defer file.Close()

	fw, err := mw.CreateFormFile("file", filepath.Base(localFilePath))
	if err != nil {
		return nil, fmt.Errorf("创建表单文件字段失败: %v", err)
	}
	if _, err = io.Copy(fw, file); err != nil {
		return nil, fmt.Errorf("写入文件内容失败: %v", err)
	}
	mw.Close()

	// 使用 commonHttp 的客户端（含 Consul 服务发现），大文件上传设置长超时
	client := commonHttp.Httpclient.Clone()
	// 必须单独设置 Transport.ResponseHeaderTimeout，SetTimeout 只设 Client.Timeout
	newTransport := http.DefaultTransport.(*http.Transport).Clone()
	newTransport.ResponseHeaderTimeout = 5 * time.Minute
	client.Transport = newTransport
	client.SetTimeout(10 * time.Minute)

	// 透传认证 headers
	hasAuthHeader := false
	if r := g.RequestFromCtx(ctx); r != nil {
		for k, v := range r.Header {
			client.SetHeader(k, v[0])
			if strings.EqualFold(k, "Authorization") || strings.EqualFold(k, "X-User-Info") {
				hasAuthHeader = true
			}
		}
	}
	// 原始请求无认证信息时，注入默认用户上下文
	if !hasAuthHeader {
		userJSON, _ := json.Marshal(beans.User{UserName: "admin", TenantId: 1})
		client.SetHeader("X-User-Info", string(userJSON))
	}

	// 设置 multipart Content-Type（含 boundary）
	contentType := mw.FormDataContentType()
	client.SetHeader("Content-Type", contentType)

	g.Log().Debugf(ctx, "[UploadToMinIO] 请求URL: oss/file/uploadFile, 文件: %s, Body大小: %d bytes",
		localFilePath, buf.Len())

	// 发送 multipart 请求（原始字节流）
	response, err := client.Post(ctx, "oss/file/uploadFile", buf.Bytes())
	if err != nil {
		glog.Error(ctx, err)
		return nil, fmt.Errorf("调用OSS上传服务失败: %v", err)
	}
	defer response.Close()

	body := response.ReadAll()

	// 调试：打印原始响应
	g.Log().Debugf(ctx, "[UploadToMinIO] OSS原始响应: %s", string(body))

	// 解析标准 GoFrame 响应格式 {code, message, data}
	var apiResp struct {
		Code    int            `json:"code"`
		Message string         `json:"message"`
		Data    *uploadFileRes `json:"data"`
	}
	if err = json.Unmarshal(body, &apiResp); err != nil {
		return nil, fmt.Errorf("响应解析失败: %v", err)
	}

	if apiResp.Code != 200 && apiResp.Code != 0 {
		return nil, fmt.Errorf("OSS上传失败: %s", apiResp.Message)
	}

	g.Log().Infof(ctx, "[UploadToMinIO] 上传成功 fileURL=%s size=%d", apiResp.Data.FileURL, apiResp.Data.FileSize)
	return apiResp.Data, nil
}

// CleanupConcat 清理输入视频文件
func CleanupConcat(paths []string) {
	for _, p := range paths {
		os.Remove(p)
	}
}

// ---------- 异步拼接任务管理 ----------

// CreateAsyncTask 创建异步拼接任务（URL模式），返回 taskId，后台处理
func (s *concatService) CreateAsyncTask(ctx context.Context, videoURLs []string, method string, upload bool, callbackURL string) (string, error) {
	if len(videoURLs) < 2 {
		return "", fmt.Errorf("至少需要2个视频才能拼接")
	}

	taskID := "concat_" + guid.S()
	task := &entity.ConcatTask{
		TaskID:     taskID,
		Status:     "pending",
		MethodUsed: method,
	}
	if _, err := dao.ConcatTask.Insert(ctx, task); err != nil {
		return "", fmt.Errorf("创建任务失败: %v", err)
	}

	g.Log().Infof(ctx, "[异步拼接] 创建任务 %s, 视频数=%d, 回调=%s", taskID, len(videoURLs), callbackURL)

	// 异步处理：先下载再拼接
	go s.processAsyncTask(taskID, videoURLs, method, upload, callbackURL)

	return taskID, nil
}

// CreateAsyncTaskWithFiles 创建异步拼接任务（文件上传模式），直接处理本地文件
func (s *concatService) CreateAsyncTaskWithFiles(ctx context.Context, filePaths []string, method string, upload bool, callbackURL string) (string, error) {
	if len(filePaths) < 2 {
		return "", fmt.Errorf("至少需要2个视频才能拼接")
	}

	taskID := "concat_" + guid.S()
	task := &entity.ConcatTask{
		TaskID:     taskID,
		Status:     "pending",
		MethodUsed: method,
	}
	if _, err := dao.ConcatTask.Insert(ctx, task); err != nil {
		return "", fmt.Errorf("创建任务失败: %v", err)
	}

	g.Log().Infof(ctx, "[异步拼接-文件] 创建任务 %s, 文件数=%d, 回调=%s", taskID, len(filePaths), callbackURL)

	// 异步处理：已有本地文件，直接拼接
	go s.processAsyncTaskWithFiles(taskID, filePaths, method, upload, callbackURL)

	return taskID, nil
}

// GetTaskResult 查询异步任务结果
func (s *concatService) GetTaskResult(ctx context.Context, taskID string) (*dto.GetConcatTaskRes, error) {
	task, err := dao.ConcatTask.GetByTaskID(ctx, taskID)
	if err != nil {
		return nil, fmt.Errorf("查询任务失败: %v", err)
	}
	if task == nil {
		return nil, fmt.Errorf("任务不存在: %s", taskID)
	}

	return dao.EntityToTaskRes(task), nil
}

// processAsyncTaskWithFiles 后台处理异步拼接任务（文件上传模式，文件已在本地）
func (s *concatService) processAsyncTaskWithFiles(taskID string, filePaths []string, method string, upload bool, callbackURL string) {
	bgCtx := context.Background()
	bgCtx = context.WithValue(bgCtx, "user", &beans.User{UserName: "admin", TenantId: 1})

	dao.ConcatTask.UpdateRunning(bgCtx, taskID)

	defer func() {
		if r := recover(); r != nil {
			errMsg := fmt.Sprintf("异步拼接异常: %v", r)
			g.Log().Errorf(bgCtx, "[异步拼接 %s] %s", taskID, errMsg)
			dao.ConcatTask.UpdateError(bgCtx, taskID, errMsg)
			s.concatCallback(bgCtx, taskID, callbackURL)
		}
	}()

	concatErr := s.executeConcat(bgCtx, taskID, filePaths, method, upload)
	if concatErr != nil {
		dao.ConcatTask.UpdateError(bgCtx, taskID, concatErr.Error())
		s.concatCallback(bgCtx, taskID, callbackURL)
		return
	}

	g.Log().Infof(bgCtx, "[异步拼接 %s] 完成", taskID)

	if callbackURL != "" {
		s.concatCallback(bgCtx, taskID, callbackURL)
	}
}

// processAsyncTask 后台处理异步拼接任务（URL模式，需要先下载）
func (s *concatService) processAsyncTask(taskID string, videoURLs []string, method string, upload bool, callbackURL string) {
	bgCtx := context.Background()
	bgCtx = context.WithValue(bgCtx, "user", &beans.User{UserName: "admin", TenantId: 1})

	dao.ConcatTask.UpdateRunning(bgCtx, taskID)

	defer func() {
		if r := recover(); r != nil {
			errMsg := fmt.Sprintf("异步拼接异常: %v", r)
			g.Log().Errorf(bgCtx, "[异步拼接 %s] %s", taskID, errMsg)
			dao.ConcatTask.UpdateError(bgCtx, taskID, errMsg)
			s.concatCallback(bgCtx, taskID, callbackURL)
		}
	}()

	// 下载视频
	var savePaths []string
	tempDir := g.Cfg().MustGet(bgCtx, "ffmpeg.temp_dir", "resource/temp").String()
	os.MkdirAll(tempDir, 0755)

	for _, videoURL := range videoURLs {
		savePath, dlErr := downloadFile(bgCtx, videoURL, tempDir)
		if dlErr != nil {
			g.Log().Warningf(bgCtx, "[异步拼接 %s] 下载失败 %s: %v", taskID, videoURL, dlErr)
			continue
		}
		savePaths = append(savePaths, savePath)
	}

	if len(savePaths) < 2 {
		errMsg := fmt.Sprintf("成功下载的视频不足2个(共%d)", len(videoURLs))
		dao.ConcatTask.UpdateError(bgCtx, taskID, errMsg)
		CleanupConcat(savePaths)
		s.concatCallback(bgCtx, taskID, callbackURL)
		return
	}

	// 执行拼接
	concatErr := s.executeConcat(bgCtx, taskID, savePaths, method, upload)
	CleanupConcat(savePaths)

	if concatErr != nil {
		dao.ConcatTask.UpdateError(bgCtx, taskID, concatErr.Error())
		s.concatCallback(bgCtx, taskID, callbackURL)
		return
	}

	g.Log().Infof(bgCtx, "[异步拼接 %s] 完成", taskID)

	if callbackURL != "" {
		s.concatCallback(bgCtx, taskID, callbackURL)
	}
}

// executeConcat 执行拼接并更新任务状态，返回输出路径
func (s *concatService) executeConcat(ctx context.Context, taskID string, filePaths []string, method string, upload bool) error {
	tempDir := filepath.Dir(filePaths[0])
	outputPath := filepath.Join(tempDir,
		fmt.Sprintf("concat_%s_x%d_%s.mp4", taskID, len(filePaths), time.Now().Format("150405")))

	res, concatErr := s.Concat(ctx, &ConcatReq{
		VideoPaths: filePaths,
		OutputPath: outputPath,
		Method:     method,
		Upload:     upload,
	})
	if concatErr != nil {
		os.Remove(outputPath)
		return concatErr
	}

	// 更新数据库为成功
	fileName := filepath.Base(outputPath)
	fileFormat := ""
	if idx := strings.LastIndex(fileName, "."); idx > 0 {
		fileFormat = fileName[idx+1:]
	}
	dao.ConcatTask.UpdateSuccess(ctx, taskID,
		res.FileURL, res.FileSize, fileName, fileFormat,
		"", res.MethodUsed, res.DurationStr)

	os.Remove(outputPath)
	return nil
}

// concatCallback 回调通知（从数据库读取任务结果发送）
func (s *concatService) concatCallback(ctx context.Context, taskID, callbackURL string) {
	if callbackURL == "" {
		return
	}

	task, err := dao.ConcatTask.GetByTaskID(ctx, taskID)
	if err != nil || task == nil {
		g.Log().Errorf(ctx, "[异步拼接回调 %s] 查询任务失败: %v", taskID, err)
		return
	}

	payload := map[string]interface{}{
		"taskId": task.TaskID,
		"status": task.Status,
	}
	if task.Status == "success" {
		payload["fileURL"] = task.FileURL
		payload["fileSize"] = task.FileSize
	}
	if task.Status == "failed" {
		payload["errorMessage"] = task.ErrorMessage
	}

	body, _ := json.Marshal(payload)
	g.Log().Infof(ctx, "[异步拼接回调 %s] 状态=%s, 目标=%s", taskID, task.Status, callbackURL)

	req, _ := http.NewRequest("POST", callbackURL, bytes.NewReader(body))
	req.Header.Set("Content-Type", "application/json")
	userJSON, _ := json.Marshal(beans.User{UserName: "admin", TenantId: 1})
	req.Header.Set("X-User-Info", string(userJSON))

	client := &http.Client{Timeout: 30 * time.Second}
	resp, reqErr := client.Do(req)
	if reqErr != nil {
		g.Log().Errorf(ctx, "[异步拼接回调 %s] 请求失败: %v", taskID, reqErr)
		return
	}
	defer resp.Body.Close()
	respBody, _ := io.ReadAll(resp.Body)
	g.Log().Infof(ctx, "[异步拼接回调 %s] 响应 status=%d, body=%s", taskID, resp.StatusCode, string(respBody))
}

// downloadFile 下载文件到临时目录
func downloadFile(ctx context.Context, rawURL, tempDir string) (string, error) {
	parsedURL, err := url.Parse(rawURL)
	if err != nil {
		return "", err
	}
	segments := strings.Split(parsedURL.Path, "/")
	fileName := segments[len(segments)-1]
	if fileName == "" {
		fileName = fmt.Sprintf("video_%d.mp4", time.Now().UnixMilli())
	}
	savePath := filepath.Join(tempDir, fmt.Sprintf("%d_%s", time.Now().UnixMilli(), fileName))

	client := &http.Client{Timeout: 10 * time.Minute}
	resp, err := client.Get(rawURL)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	out, err := os.Create(savePath)
	if err != nil {
		return "", err
	}
	defer out.Close()

	_, err = io.Copy(out, resp.Body)
	if err != nil {
		os.Remove(savePath)
		return "", err
	}
	return savePath, nil
}