main.go

package main

import (
	"github.com/nlopes/slack"
	"github.com/joho/godotenv"
	"log"
	"net/http"
	"io/ioutil"
	"os"
	"sync"
	"fmt"
	"flag"
	"time"
)

const folderName = "slack-downloads"

func main() {
	godotenv.Load()
	slackToken := flag.String("token", os.Getenv("SLACK_API_TOKEN"), "Set Slack API Token")
	fileType := flag.String("type", "all", "Set file type")
	beforeTimestamp := flag.Int64("before", time.Now().Unix(), "Set file timestamp (file older than this timestamp will be the target)")
	includePrivate := flag.Bool("private", false, "Download private files")
	doDelete := flag.Bool("delete", false, "Delete downloaded files from Slack")
	flag.Parse()

	api := slack.New(*slackToken)
	files, paging, err := getFiles(api, *fileType, *beforeTimestamp, 1)
	if err != nil {
		log.Fatal(err)
	}
	if _, err := os.Stat(folderName); err != nil {
		os.Mkdir(folderName, 0777)
	}

	slackFileDeleter := newInstance()
	go slackFileDeleter.run(api)

	waitGroup := sync.WaitGroup{}
	for paging.Page <= paging.Pages {
		for _, slackFile := range files {
			if !*includePrivate && !slackFile.IsPublic {
				continue
			}
			if _, err := os.Stat(getFileName(slackFile)); err == nil {
				if *doDelete {
					slackFileDeleter.delete(slackFile.ID)
				}
				continue
			}
			waitGroup.Add(1)
			go write(&waitGroup, slackFile, *slackToken, *doDelete, slackFileDeleter)
		}
		log.Printf("files size: %d, paging: %#v\n", len(files), paging)
		files, paging, err = getFiles(api, *fileType, *beforeTimestamp, paging.Page+1)
		if err != nil {
			log.Fatal(err)
		}
	}

	waitGroup.Wait()
	slackFileDeleter.stop()
}

func write(waitGroup *sync.WaitGroup, slackFile slack.File, slackToken string, doDelete bool, deleter SlackFileDeleter) {
	defer waitGroup.Done()
	req, err := http.NewRequest("GET", slackFile.URLPrivateDownload, nil)
	req.Header.Set("Authorization", "Bearer "+slackToken)
	client := new(http.Client)
	res, err := client.Do(req)
	if err != nil {
		log.Println(err)
		return
	}
	defer res.Body.Close()
	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		log.Println(err)
		return
	}
	file, err := os.OpenFile(getFileName(slackFile), os.O_CREATE|os.O_WRONLY, 0666, )
	if err != nil {
		log.Println(err)
		return
	}
	defer file.Close()
	_, err = file.Write(body)
	if err != nil {
		log.Println(err)
		return
	}
	log.Printf("Download finished: %s\n", slackFile.URLPrivateDownload)

	if doDelete {
		deleter.delete(slackFile.ID)
	}
}

func getFiles(api *slack.Client, fileType string, beforeTimestamp int64, page int) ([]slack.File, *slack.Paging, error) {
	return api.GetFiles(slack.GetFilesParameters{
		Types: fileType,
		Count: 1000,
		Page:  page,
		TimestampTo: slack.JSONTime(beforeTimestamp), 
	})
}

func getFileName(slackFile slack.File) string {
	return fmt.Sprintf("%s/%s-%s", folderName, slackFile.ID, slackFile.Name)
}