130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
package main
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import (
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"fmt"
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"strconv"
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"strings"
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"time"
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)
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type cronSpec struct {
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min, hour, dom, mon, dow map[int]bool
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domAll, dowAll bool
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}
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func parseCron(spec string) (*cronSpec, error) {
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fields := strings.Fields(spec)
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if len(fields) != 5 {
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return nil, fmt.Errorf("cron 需要 5 个字段（分 时 日 月 周），收到 %d 个", len(fields))
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}
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c := &cronSpec{}
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var err error
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if c.min, err = parseCronField(fields[0], 0, 59); err != nil {
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return nil, fmt.Errorf("分钟字段: %w", err)
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}
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if c.hour, err = parseCronField(fields[1], 0, 23); err != nil {
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return nil, fmt.Errorf("小时字段: %w", err)
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}
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if c.dom, err = parseCronField(fields[2], 1, 31); err != nil {
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return nil, fmt.Errorf("日字段: %w", err)
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}
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if c.mon, err = parseCronField(fields[3], 1, 12); err != nil {
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return nil, fmt.Errorf("月字段: %w", err)
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}
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if c.dow, err = parseCronField(fields[4], 0, 7); err != nil {
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return nil, fmt.Errorf("星期字段: %w", err)
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}
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if c.dow[7] {
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c.dow[0] = true
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}
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c.domAll = len(c.dom) == 31
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c.dowAll = len(c.dow) == 8
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return c, nil
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}
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func parseCronField(f string, min, max int) (map[int]bool, error) {
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set := map[int]bool{}
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for _, part := range strings.Split(f, ",") {
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part = strings.TrimSpace(part)
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if part == "" {
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return nil, fmt.Errorf("存在空字段")
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}
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step := 1
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if i := strings.Index(part, "/"); i >= 0 {
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n, err := strconv.Atoi(part[i+1:])
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if err != nil || n <= 0 {
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return nil, fmt.Errorf("无效步长 %q", part)
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}
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step = n
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part = part[:i]
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if part == "" {
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part = "*"
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}
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}
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lo, hi := 0, 0
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if part == "*" {
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lo, hi = min, max
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} else if rng := strings.SplitN(part, "-", 2); len(rng) == 2 {
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var err error
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if lo, err = strconv.Atoi(rng[0]); err != nil {
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return nil, fmt.Errorf("无效值 %q", part)
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}
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if hi, err = strconv.Atoi(rng[1]); err != nil {
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return nil, fmt.Errorf("无效值 %q", part)
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}
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} else {
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v, err := strconv.Atoi(part)
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if err != nil {
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return nil, fmt.Errorf("无效值 %q", part)
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}
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lo, hi = v, v
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}
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if lo < min || hi > max || lo > hi {
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return nil, fmt.Errorf("值超出范围 [%d,%d]: %q", min, max, part)
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}
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for v := lo; v <= hi; v += step {
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set[v] = true
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}
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}
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return set, nil
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}
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func cronNextString(expr string) (string, error) {
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spec, err := parseCron(expr)
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if err != nil {
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return "", err
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}
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return cronNext(spec, time.Now()).Format("2006-01-02 15:04"), nil
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}
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func cronNext(spec *cronSpec, after time.Time) time.Time {
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t := after.Truncate(time.Minute).Add(time.Minute)
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limit := t.AddDate(1, 0, 0)
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for t.Before(limit) {
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if !spec.mon[int(t.Month())] {
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t = time.Date(t.Year(), t.Month(), 1, 0, 0, 0, 0, t.Location()).AddDate(0, 1, 0)
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continue
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}
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domOK := spec.dom[t.Day()]
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dowOK := spec.dow[int(t.Weekday())]
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dayOK := domOK && dowOK
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if !spec.domAll && !spec.dowAll {
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dayOK = domOK || dowOK
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}
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if !dayOK {
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t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location()).AddDate(0, 0, 1)
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continue
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}
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if !spec.hour[t.Hour()] {
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t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, t.Location()).Add(time.Hour)
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continue
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}
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if spec.min[t.Minute()] {
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return t
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}
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t = t.Add(time.Minute)
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}
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return limit
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}
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