movetosubdir

package main

import (
    "flag"
    "io/ioutil"
    "log"
    "os"
    "path"
    "path/filepath"
    "sort"
    "strconv"
    "strings"
    "time"
)

var (
    // flags
    root  string
    limit int
    pad   int
    order string
    // operation vars
    folder = 1
)

type fileInfo struct {
    path    string
    modTime time.Time
}

func initFlags() {
    rootPtr := flag.String("root", ".", "Root directory")
    limitPtr := flag.Int("limit", 100, "Max files per folder")
    padPtr := flag.Int("pad", 4, "Pad zeroes until length")
    orderPtr := flag.String("order", "date", "How to order files, possible values: date, name")
    flag.Parse()
    root = *rootPtr
    limit = *limitPtr
    order = *orderPtr
    pad = *padPtr
}

func getFiles(limit int) []fileInfo {
    ret := []fileInfo{}
    // filepath.
    fi, err := ioutil.ReadDir(root)
    check(err)
    for _, info := range fi {
        if info.IsDir() {
            continue
        }
        curInfo := fileInfo{
            path:    path.Join(root, info.Name()),
            modTime: info.ModTime(),
        }
        ret = append(ret, curInfo)
    }
    if len(ret) == 0 {
        return ret
    }
    sort.SliceStable(ret, func(i, j int) bool {
        if order == "name" {
            return strings.Compare(ret[i].path, ret[j].path) < 0
        }
        return ret[i].modTime.Unix() < ret[j].modTime.Unix()
    })
    return ret[:min(len(ret), limit)]
}

func check(err error) {
    if err != nil {
        panic(err)
    }
}

func min(a ...int) int {
    if len(a) == 0 {
        return 0
    }
    ret := a[0]
    for _, v := range a[1:] {
        if v < ret {
            ret = v
        }
    }
    return ret
}

func padZero(num, length int) string {
    numStr := strconv.Itoa(num)
    for length > len(numStr) {
        numStr = "0" + numStr
    }
    return numStr
}

func main() {
    initFlags()
    files := getFiles(limit)
    for len(files) > 0 {
        for _, fi := range files {
            dir, _ := filepath.Abs(filepath.Dir(fi.path))
            targetDir := filepath.Join(dir, padZero(folder, pad))
            log.Println("Creating target:", targetDir)
            _ = os.Mkdir(targetDir, 0644)
            target := filepath.Join(targetDir, filepath.Base(fi.path))
            log.Println("Moving file", fi.path, "to", target)
            check(os.Rename(fi.path, target))
        }
        folder++
        files = getFiles(limit)
    }
}