Tools/CronParser.ps1

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
function Get-CronFields
{
    return @(
        'Minute',
        'Hour',
        'DayOfMonth',
        'Month',
        'DayOfWeek'
    )
}

function Get-CronFieldConstraints
{
    return @{
        'MinMax' = @(
            @(0, 59),
            @(0, 23),
            @(1, 31),
            @(1, 12),
            @(0, 6)
        );
        'DaysInMonths' = @(
            31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
        );
        'Months' = @(
            'January', 'February', 'March', 'April', 'May', 'June', 'July',
            'August', 'September', 'October', 'November', 'December'
        );
    }
}

function Get-CronPredefined
{
    return @{
        # normal
        '@minutely' = '* * * * *';
        '@hourly' = '0 * * * *';
        '@daily' = '0 0 * * *';
        '@weekly' = '0 0 * * 0';
        '@monthly' = '0 0 1 * *';
        '@quaterly' = '0 0 1 1,4,8,7,10';
        '@yearly' = '0 0 1 1 *';
        '@annually' = '0 0 1 1 *';

        # twice
        '@twice-hourly' = '0,30 * * * *';
        '@twice-daily' = '0,12 0 * * *';
        '@twice-weekly' = '0 0 * * 0,4';
        '@twice-monthly' = '0 0 1,15 * *';
        '@twice-yearly' = '0 0 1 1,6 *';
        '@twice-annually' = '0 0 1 1,6 *';
    }
}

function Get-CronFieldAliases
{
    return @{
        'Month' = @{
            'Jan' = 1;
            'Feb' = 2;
            'Mar' = 3;
            'Apr' = 4;
            'May' = 5;
            'Jun' = 6;
            'Jul' = 7;
            'Aug' = 8;
            'Sep' = 9;
            'Oct' = 10;
            'Nov' = 11;
            'Dec' = 12;
        };
        'DayOfWeek' = @{
            'Sun' = 0;
            'Mon' = 1;
            'Tue' = 2;
            'Wed' = 3;
            'Thu' = 4;
            'Fri' = 5;
            'Sat' = 6;
        };
    }
}

function ConvertFrom-CronExpressions
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string[]]
        $Expressions
    )

    return @(@($Expressions) | ForEach-Object {
        ConvertFrom-CronExpression -Expression $_
    })
}

function ConvertFrom-CronExpression
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string]
        $Expression
    )

    $Expression = $Expression.Trim()

    # check predefineds
    $predef = Get-CronPredefined
    if (!(Test-Empty $predef[$Expression])) {
        $Expression = $predef[$Expression]
    }

    # split and check atoms length
    $atoms = @($Expression -isplit '\s+')
    if ($atoms.Length -ne 5) {
        throw "Cron expression should only consist of 5 parts: $($Expression)"
    }

    # basic variables
    $aliasRgx = '(?<tag>[a-z]{3})'

    # get cron obj and validate atoms
    $fields = Get-CronFields
    $constraints = Get-CronFieldConstraints
    $aliases = Get-CronFieldAliases
    $cron = @{}

    for ($i = 0; $i -lt $atoms.Length; $i++)
    {
        $_cronExp = @{
            'Range' = $null;
            'Values' = $null;
            'Constraints' = $null;
            'Random' = $false;
        }

        $_atom = $atoms[$i]
        $_field = $fields[$i]
        $_constraint = $constraints.MinMax[$i]
        $_aliases = $aliases[$_field]

        # replace day of week and months with numbers
        switch ($_field)
        {
            { $_field -ieq 'month' -or $_field -ieq 'dayofweek' }
                {
                    while ($_atom -imatch $aliasRgx) {
                        $_alias = $_aliases[$Matches['tag']]
                        if ($null -eq $_alias) {
                            throw "Invalid $($_field) alias found: $($Matches['tag'])"
                        }

                        $_atom = $_atom -ireplace $Matches['tag'], $_alias
                        $_atom -imatch $aliasRgx | Out-Null
                    }
                }
        }

        # ensure atom is a valid value
        if (!($_atom -imatch '^[\d|/|*|\-|,r]+$')) {
            throw "Invalid atom character: $($_atom)"
        }

        # replace * with min/max constraint
        $_atom = $_atom -ireplace '\*', ($_constraint -join '-')

        # parse the atom for either a literal, range, array, or interval
        # literal
        if ($_atom -imatch '^(\d+|r)$') {
            # check if it's random
            if ($_atom -ieq 'r') {
                $_cronExp.Values = @(Get-Random -Minimum $_constraint[0] -Maximum ($_constraint[1] + 1))
                $_cronExp.Random = $true
            }
            else {
                $_cronExp.Values = @([int]$_atom)
            }
        }

        # range
        elseif ($_atom -imatch '^(?<min>\d+)\-(?<max>\d+)$') {
            $_cronExp.Range = @{ 'Min' = [int]($Matches['min'].Trim()); 'Max' = [int]($Matches['max'].Trim()); }
        }

        # array
        elseif ($_atom -imatch '^[\d,]+$') {
            $_cronExp.Values = [int[]](@($_atom -split ',').Trim())
        }

        # interval
        elseif ($_atom -imatch '(?<start>(\d+|\*))\/(?<interval>(\d+|r))$') {
            $start = $Matches['start']
            $interval = $Matches['interval']

            if ($interval -ieq '0') {
                $interval = '1'
            }

            if ([string]::IsNullOrWhiteSpace($start) -or $start -ieq '*') {
                $start = '0'
            }

            # set the initial trigger value
            $_cronExp.Values = @([int]$start)

            # check if it's random
            if ($interval -ieq 'r') {
                $_cronExp.Random = $true
            }
            else {
                # loop to get all next values
                $next = [int]$start + [int]$interval
                while ($next -le $_constraint[1]) {
                    $_cronExp.Values += $next
                    $next += [int]$interval
                }
            }
        }

        # error
        else {
            throw "Invalid cron atom format found: $($_atom)"
        }

        # ensure cron expression values are valid
        if ($null -ne $_cronExp.Range) {
            if ($_cronExp.Range.Min -gt $_cronExp.Range.Max) {
                throw "Min value for $($_field) should not be greater than the max value"
            }

            if ($_cronExp.Range.Min -lt $_constraint[0]) {
                throw "Min value '$($_cronExp.Range.Min)' for $($_field) is invalid, should be greater than/equal to $($_constraint[0])"
            }

            if ($_cronExp.Range.Max -gt $_constraint[1]) {
                throw "Max value '$($_cronExp.Range.Max)' for $($_field) is invalid, should be less than/equal to $($_constraint[1])"
            }
        }

        if ($null -ne $_cronExp.Values) {
            $_cronExp.Values | ForEach-Object {
                if ($_ -lt $_constraint[0] -or $_ -gt $_constraint[1]) {
                    throw "Value '$($_)' for $($_field) is invalid, should be between $($_constraint[0]) and $($_constraint[1])"
                }
            }
        }

        # assign value
        $_cronExp.Constraints = $_constraint
        $cron[$_field] = $_cronExp
    }

    # post validation for month/days in month
    if ($null -ne $cron['Month'].Values -and $null -ne $cron['DayOfMonth'].Values)
    {
        foreach ($mon in $cron['Month'].Values) {
            foreach ($day in $cron['DayOfMonth'].Values) {
                if ($day -gt $constraints.DaysInMonths[$mon - 1]) {
                    throw "$($constraints.Months[$mon - 1]) only has $($constraints.DaysInMonths[$mon - 1]) days, but $($day) was supplied"
                }
            }
        }
    }

    # flag if this cron contains a random atom
    $cron['Random'] = (($cron.Values | Where-Object { $_.Random } | Measure-Object).Count -gt 0)

    # return the parsed cron expression
    return $cron
}

function Reset-RandomCronExpressions
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNull()]
        $Expressions
    )

    return @(@($Expressions) | ForEach-Object {
        Reset-RandomCronExpression -Expression $_
    })
}

function Reset-RandomCronExpression
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNull()]
        $Expression
    )

    function Reset-Atom($Atom) {
        if (!$Atom.Random) {
            return $Atom
        }

        if ($Atom.Random) {
            $Atom.Values = @(Get-Random -Minimum $Atom.Constraints[0] -Maximum ($Atom.Constraints[1] + 1))
        }

        return $Atom
    }

    if (!$Expression.Random) {
        return $Expression
    }

    $Expression.Minute = (Reset-Atom -Atom $Expression.Minute)
    $Expression.Hour = (Reset-Atom -Atom $Expression.Hour)
    $Expression.DayOfMonth = (Reset-Atom -Atom $Expression.DayOfMonth)
    $Expression.Month = (Reset-Atom -Atom $Expression.Month)
    $Expression.DayOfWeek = (Reset-Atom -Atom $Expression.DayOfWeek)

    return $Expression
}

function Test-CronExpressions
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNull()]
        $Expressions,

        [Parameter()]
        $DateTime = $null
    )

    return ((@($Expressions) | Where-Object {
        Test-CronExpression -Expression $_ -DateTime $DateTime
    } | Measure-Object).Count -gt 0)
}

function Test-CronExpression
{
    param (
        [Parameter(Mandatory=$true)]
        [ValidateNotNull()]
        $Expression,

        [Parameter()]
        $DateTime = $null
    )

    function Test-RangeAndValue($AtomContraint, $NowValue) {
        if ($null -ne $AtomContraint.Range) {
            if ($NowValue -lt $AtomContraint.Range.Min -or $NowValue -gt $AtomContraint.Range.Max) {
                return $false
            }
        }
        elseif ($AtomContraint.Values -inotcontains $NowValue) {
            return $false
        }

        return $true
    }

    # current time
    if ($null -eq $DateTime) {
        $DateTime = [datetime]::Now
    }

    # check day of week and day of month (both must fail)
    if (!(Test-RangeAndValue -AtomContraint $Expression.DayOfWeek -NowValue ([int]$DateTime.DayOfWeek)) -and
        !(Test-RangeAndValue -AtomContraint $Expression.DayOfMonth -NowValue $DateTime.Day)) {
        return $false
    }

    # check month
    if (!(Test-RangeAndValue -AtomContraint $Expression.Month -NowValue $DateTime.Month)) {
        return $false
    }

    # check hour
    if (!(Test-RangeAndValue -AtomContraint $Expression.Hour -NowValue $DateTime.Hour)) {
        return $false
    }

    # check minute
    if (!(Test-RangeAndValue -AtomContraint $Expression.Minute -NowValue $DateTime.Minute)) {
        return $false
    }

    # date is valid
    return $true
}