300 lines
8.0 KiB
Go
300 lines
8.0 KiB
Go
/*!
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* Copyright 2013 Raymond Hill
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*
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* Project: github.com/gorhill/cronexpr
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* File: cronexpr.go
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* Version: 1.0
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* License: pick the one which suits you :
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* GPL v3 see <https://www.gnu.org/licenses/gpl.html>
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* APL v2 see <http://www.apache.org/licenses/LICENSE-2.0>
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*
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*/
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// Package cronexpr parses cron time expressions.
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package cronexpr
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/******************************************************************************/
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import (
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"fmt"
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"sort"
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"time"
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)
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/******************************************************************************/
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// A Expression represents a specific cron time expression as defined at
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// <https://github.com/gorhill/cronexpr#implementation>
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type Expression struct {
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expression string
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options Options
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secondList []int
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minuteList []int
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hourList []int
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daysOfMonth map[int]bool
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workdaysOfMonth map[int]bool
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lastDayOfMonth bool
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lastWorkdayOfMonth bool
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daysOfMonthRestricted bool
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actualDaysOfMonthList []int
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monthList []int
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daysOfWeek map[int]bool
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specificWeekDaysOfWeek map[int]bool
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lastWeekDaysOfWeek map[int]bool
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daysOfWeekRestricted bool
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yearList []int
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// indicates an instance of a expression used internally
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// for rounding a time
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rounding bool
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}
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type DSTFlags uint
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const (
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// DSTLeapUnskip indicates the parser to not skip times that would have been
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// been skipped when the clock moves forward on a DST change.
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DSTLeapUnskip = 1 << iota
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// DSTFallFireEarly indicates the parser to return the earliest time
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// when a time is repeated due to a DST fall.
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DSTFallFireEarly
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// DSTFallFireLate indicates the parser to return the latest time
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// when a time is repeated due to a DST fall.
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DSTFallFireLate
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)
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type Options struct {
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DSTFlags DSTFlags
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}
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/******************************************************************************/
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// MustParse returns a new Expression pointer. It expects a well-formed cron
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// expression. If a malformed cron expression is supplied, it will `panic`.
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// See <https://github.com/gorhill/cronexpr#implementation> for documentation
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// about what is a well-formed cron expression from this library's point of
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// view.
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func MustParse(cronLine string) *Expression {
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expr, err := Parse(cronLine)
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if err != nil {
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panic(err)
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}
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return expr
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}
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/******************************************************************************/
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// Parse returns a new Expression pointer. An error is returned if a malformed
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// cron expression is supplied.
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// See <https://github.com/gorhill/cronexpr#implementation> for documentation
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// about what is a well-formed cron expression from this library's point of
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// view.
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func Parse(cronLine string) (*Expression, error) {
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return ParseWithOptions(cronLine, Options{DSTFlags: DSTLeapUnskip | DSTFallFireEarly})
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}
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// ParseWithOptions is used to build a Expression pointer with custom options.
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func ParseWithOptions(cronLine string, options Options) (*Expression, error) {
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if options.DSTFlags == 0 {
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return nil, fmt.Errorf("missing DST flags")
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}
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// Maybe one of the built-in aliases is being used
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cron := cronNormalizer.Replace(cronLine)
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indices := fieldFinder.FindAllStringIndex(cron, -1)
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fieldCount := len(indices)
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if fieldCount < 5 {
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return nil, fmt.Errorf("missing field(s)")
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}
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// ignore fields beyond 7th
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if fieldCount > 7 {
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fieldCount = 7
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}
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var expr = Expression{options: options}
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var field = 0
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var err error
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// second field (optional)
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if fieldCount == 7 {
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err = expr.secondFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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} else {
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expr.secondList = []int{0}
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}
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// minute field
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err = expr.minuteFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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// hour field
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err = expr.hourFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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// day of month field
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err = expr.domFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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// month field
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err = expr.monthFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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// day of week field
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err = expr.dowFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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field += 1
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// year field
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if field < fieldCount {
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err = expr.yearFieldHandler(cron[indices[field][0]:indices[field][1]])
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if err != nil {
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return nil, err
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}
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} else {
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expr.yearList = yearDescriptor.defaultList
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}
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return &expr, nil
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}
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/******************************************************************************/
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// Next returns the closest time instant immediately following `fromTime` which
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// matches the cron expression `expr`.
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//
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// The `time.Location` of the returned time instant is the same as that of
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// `fromTime`.
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//
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// The zero value of time.Time is returned if no matching time instant exists
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// or if a `fromTime` is itself a zero value.
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func (expr *Expression) Next(fromTime time.Time) time.Time {
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// Special case
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if fromTime.IsZero() {
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return fromTime
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}
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// Since expr.nextSecond()-expr.nextMonth() expects that the
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// supplied time stamp is a perfect match to the underlying cron
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// expression, and since this function is an entry point where `fromTime`
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// does not necessarily matches the underlying cron expression,
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// we first need to ensure supplied time stamp matches
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// the cron expression. If not, this means the supplied time
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// stamp falls in between matching time stamps, thus we move
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// to closest future matching immediately upon encountering a mismatching
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// time stamp.
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// year
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v := fromTime.Year()
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i := sort.SearchInts(expr.yearList, v)
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if i == len(expr.yearList) {
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return time.Time{}
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}
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if v != expr.yearList[i] {
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return expr.nextYear(fromTime)
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}
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// month
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v = int(fromTime.Month())
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i = sort.SearchInts(expr.monthList, v)
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if i == len(expr.monthList) {
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return expr.nextYear(fromTime)
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}
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if v != expr.monthList[i] {
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return expr.nextMonth(fromTime)
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}
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expr.actualDaysOfMonthList = expr.calculateActualDaysOfMonth(fromTime.Year(), int(fromTime.Month()))
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if len(expr.actualDaysOfMonthList) == 0 {
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return expr.nextMonth(fromTime)
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}
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// day of month
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v = fromTime.Day()
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i = sort.SearchInts(expr.actualDaysOfMonthList, v)
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if i == len(expr.actualDaysOfMonthList) {
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return expr.nextMonth(fromTime)
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}
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if v != expr.actualDaysOfMonthList[i] {
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return expr.nextDayOfMonth(fromTime)
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}
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// hour
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v = fromTime.Hour()
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i = sort.SearchInts(expr.hourList, v)
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if i == len(expr.hourList) {
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return expr.nextDayOfMonth(fromTime)
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}
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if v != expr.hourList[i] {
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return expr.nextHour(fromTime)
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}
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// minute
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v = fromTime.Minute()
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i = sort.SearchInts(expr.minuteList, v)
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if i == len(expr.minuteList) {
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return expr.nextHour(fromTime)
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}
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if v != expr.minuteList[i] {
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return expr.nextMinute(fromTime)
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}
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// second
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v = fromTime.Second()
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i = sort.SearchInts(expr.secondList, v)
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if i == len(expr.secondList) {
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return expr.nextMinute(fromTime)
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}
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// If we reach this point, there is nothing better to do
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// than to move to the next second
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return expr.nextSecond(fromTime)
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}
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/******************************************************************************/
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// NextN returns a slice of `n` closest time instants immediately following
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// `fromTime` which match the cron expression `expr`.
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//
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// The time instants in the returned slice are in chronological ascending order.
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// The `time.Location` of the returned time instants is the same as that of
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// `fromTime`.
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//
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// A slice with len between [0-`n`] is returned, that is, if not enough existing
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// matching time instants exist, the number of returned entries will be less
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// than `n`.
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func (expr *Expression) NextN(fromTime time.Time, n uint) []time.Time {
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nextTimes := make([]time.Time, 0, n)
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if n > 0 {
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fromTime = expr.Next(fromTime)
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for {
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if fromTime.IsZero() {
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break
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}
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nextTimes = append(nextTimes, fromTime)
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n -= 1
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if n == 0 {
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break
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}
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fromTime = expr.nextSecond(fromTime)
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}
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}
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return nextTimes
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}
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