git.giacomolli.uk - onechat/blob - schedule.go

   1 package main
   2
   3 import (
   4         "cmp"
   5         "context"
   6         "encoding/json"
   7         "errors"
   8         "fmt"
   9         "log"
  10         "os"
  11         "slices"
  12         "strconv"
  13         "strings"
  14         "sync"
  15         "time"
  16 )
  17
  18 const (
  19         // scheduleFileName is the file of the schedules in the directory of the
  20         // agent.
  21         scheduleFileName = "schedules.json"
  22
  23         // scheduleTextBytes is the most bytes of the text of a schedule.
  24         scheduleTextBytes = 4096
  25
  26         // scheduleAtLayout is the layout of the time of a one-time schedule.
  27         scheduleAtLayout = "2006-01-02 15:04"
  28
  29         // scheduleTimeLayout is the layout of the times in the answers of the
  30         // tools and in the log.
  31         scheduleTimeLayout = "Monday 2006-01-02 15:04 -07:00"
  32
  33         // scheduleSource is the source of the work events of the runs.
  34         scheduleSource = "schedule"
  35
  36         // scheduleCheck is the longest wait of Run before it looks at the times
  37         // again, so that it sees a suspend of the machine or a change of the
  38         // clock.
  39         scheduleCheck = time.Minute
  40
  41         // scheduleLate is how long after its time a run is late.
  42         scheduleLate = time.Minute
  43
  44         // scheduleEmptyReply is the last line of the message of a run.
  45         scheduleEmptyReply = "If nothing in this task needs the user, end your turn with an empty reply."
  46
  47         // scheduleLateLine tells the agent that a run is late.
  48         scheduleLateLine = "This run is late: the daemon was stopped at that time."
  49 )
  50
  51 // openSchedules reads the schedules of the file at path. A missing file holds
  52 // none. The clock gives the time and the time zone of the schedules, and logger
  53 // gets one line for each run.
  54 func openSchedules(path string, clock func() time.Time, logger *log.Logger) (*Schedules, error) {
  55         s := &Schedules{
  56                 path:    path,
  57                 clock:   clock,
  58                 logger:  logger,
  59                 check:   scheduleCheck,
  60                 changed: make(chan struct{}, 1),
  61         }
  62
  63         data, err := os.ReadFile(path)
  64         if errors.Is(err, os.ErrNotExist) {
  65                 return s, nil
  66         }
  67
  68         if err != nil {
  69                 return nil, fmt.Errorf("read schedules: %w", err)
  70         }
  71
  72         err = json.Unmarshal(data, &s.file)
  73         if err != nil {
  74                 return nil, fmt.Errorf("%s: %w", path, err)
  75         }
  76
  77         for _, schedule := range s.file.Schedules {
  78                 if schedule.Cron == "" {
  79                         continue
  80                 }
  81
  82                 _, err = scheduleParseCron(schedule.Cron)
  83                 if err != nil {
  84                         return nil, fmt.Errorf("%s: schedule %d: %w", path, schedule.ID, err)
  85                 }
  86         }
  87
  88         return s, nil
  89 }
  90
  91 // Schedules holds the schedules of the agent: tasks that start a turn at one
  92 // time or at the times of a cron expression. Each change writes the file whole
  93 // before it returns, so a schedule survives a restart. The mutex protects the
  94 // schedules, because the tools change them from a turn while Run reads them.
  95 // changed tells Run that a set or a remove changed the times.
  96 type Schedules struct {
  97         path    string
  98         clock   func() time.Time
  99         logger  *log.Logger
 100         check   time.Duration
 101         changed chan struct{}
 102
 103         mutex sync.Mutex
 104         file  ScheduleFile
 105 }
 106
 107 // Run starts the runs of the due schedules in l until ctx ends. It waits until
 108 // the first due time, at most check at a time, and also wakes at a set or a
 109 // remove. So a schedule that came due while the daemon was stopped runs at the
 110 // start. It returns the error of a write of the log or of the file.
 111 func (s *Schedules) Run(ctx context.Context, l *TurnLoop) error {
 112         for {
 113                 err := s.deliver(ctx, l)
 114                 if err != nil {
 115                         return err
 116                 }
 117
 118                 var timer *time.Timer
 119                 var timeout <-chan time.Time
 120                 wait, found := s.Wait(s.clock())
 121                 if found {
 122                         timer = time.NewTimer(min(wait, s.check))
 123                         timeout = timer.C
 124                 }
 125
 126                 select {
 127                 case <-ctx.Done():
 128                         return nil
 129                 case <-s.changed:
 130                 case <-timeout:
 131                 }
 132
 133                 if timer != nil {
 134                         timer.Stop()
 135                 }
 136         }
 137 }
 138
 139 // Set adds a schedule with text and returns the answer of the tool. Exactly one
 140 // of at and cron is not nil. at is a local time in scheduleAtLayout after now,
 141 // and it goes through scheduleWallTime, so a time in the hour that the clock
 142 // repeats is its first occurrence. cron is an expression of scheduleParseCron.
 143 func (s *Schedules) Set(text string, at, cron *string) (string, error) {
 144         text = strings.TrimSpace(text)
 145         if text == "" || len(text) > scheduleTextBytes {
 146                 return "", fmt.Errorf("the text must have 1 to %d bytes", scheduleTextBytes)
 147         }
 148
 149         now := s.clock()
 150         schedule := Schedule{
 151                 Text: text,
 152         }
 153
 154         switch {
 155         case (at == nil) == (cron == nil):
 156                 return "", errors.New("give either at or cron, and null for the other")
 157         case at != nil:
 158                 parsed, err := time.Parse(scheduleAtLayout, *at)
 159                 if err != nil {
 160                         return "", fmt.Errorf("at must be a local time such as %s", now.Format(scheduleAtLayout))
 161                 }
 162
 163                 schedule.Due = scheduleWallTime(parsed.Year(), parsed.Month(), parsed.Day(), parsed.Hour(), parsed.Minute(), now.Location())
 164                 if !schedule.Due.After(now) {
 165                         return "", fmt.Errorf("the time %s is not after now, %s", schedule.Due.Format(scheduleTimeLayout), now.Format(scheduleTimeLayout))
 166                 }
 167         default:
 168                 parsed, err := scheduleParseCron(*cron)
 169                 if err != nil {
 170                         return "", err
 171                 }
 172
 173                 next, found := parsed.Next(now)
 174                 if !found {
 175                         return "", fmt.Errorf("the cron expression %q matches no time in %d years", *cron, scheduleCronYears)
 176                 }
 177
 178                 schedule.Cron = parsed.String()
 179                 schedule.Due = next
 180         }
 181
 182         s.mutex.Lock()
 183         defer s.mutex.Unlock()
 184
 185         s.file.Next++
 186         schedule.ID = s.file.Next
 187         s.file.Schedules = append(s.file.Schedules, schedule)
 188         err := s.save()
 189         if err != nil {
 190                 return "", err
 191         }
 192
 193         s.change()
 194
 195         return fmt.Sprintf("Schedule %d set. Next: %s.", schedule.ID, schedule.Due.In(now.Location()).Format(scheduleTimeLayout)), nil
 196 }
 197
 198 // List returns the answer of the tool: one line for each schedule, by due time,
 199 // with its ID, its next time, its cron expression or once, and its text on one
 200 // line.
 201 func (s *Schedules) List() string {
 202         location := s.clock().Location()
 203         schedules := s.sorted()
 204         if len(schedules) == 0 {
 205                 return "No schedules."
 206         }
 207
 208         lines := make([]string, 0, len(schedules))
 209         for _, schedule := range schedules {
 210                 lines = append(lines, strconv.Itoa(schedule.ID)+" | "+schedule.Due.In(location).Format(scheduleTimeLayout)+" | "+cmp.Or(schedule.Cron, "once")+" | "+strings.Join(strings.Fields(schedule.Text), " "))
 211         }
 212
 213         return strings.Join(lines, "\n")
 214 }
 215
 216 // Len returns the number of schedules.
 217 func (s *Schedules) Len() int {
 218         s.mutex.Lock()
 219         defer s.mutex.Unlock()
 220
 221         return len(s.file.Schedules)
 222 }
 223
 224 // Remove removes the schedule id and returns the answer of the tool.
 225 func (s *Schedules) Remove(id int) (string, error) {
 226         s.mutex.Lock()
 227         defer s.mutex.Unlock()
 228
 229         index := slices.IndexFunc(s.file.Schedules, func(schedule Schedule) bool {
 230                 return schedule.ID == id
 231         })
 232
 233         if index < 0 {
 234                 return "", fmt.Errorf("no schedule %d", id)
 235         }
 236
 237         s.file.Schedules = slices.Delete(s.file.Schedules, index, index+1)
 238         err := s.save()
 239         if err != nil {
 240                 return "", err
 241         }
 242
 243         s.change()
 244
 245         return fmt.Sprintf("Schedule %d removed.", id), nil
 246 }
 247
 248 // deliver logs the message of each due schedule in l, in due order, as a work
 249 // message of scheduleSource, and wakes the loop once with all of them. A
 250 // schedule ends its run with Done after its message is durable in the log. A
 251 // crash between the two makes the run repeat once. Each run logs one line with
 252 // the ID of the schedule and, for a late run, how late it is. The line holds no
 253 // text of the schedule.
 254 func (s *Schedules) deliver(ctx context.Context, l *TurnLoop) error {
 255         now := s.clock()
 256         var turns []Message
 257         for _, schedule := range s.Due(now) {
 258                 message, err := l.Work(scheduleSource, schedule.Message(now), "")
 259                 if err != nil {
 260                         return fmt.Errorf("log a schedule: %w", err)
 261                 }
 262
 263                 // A stop of the daemon during the flush is no failure: the
 264                 // schedule stays due and runs at the next start.
 265                 err = l.Flush(ctx)
 266                 if ctx.Err() != nil {
 267                         return nil
 268                 }
 269
 270                 if err != nil {
 271                         return fmt.Errorf("log a schedule: %w", err)
 272                 }
 273
 274                 err = s.Done(schedule, now)
 275                 if err != nil {
 276                         return err
 277                 }
 278
 279                 if schedule.late(now) {
 280                         s.logger.Printf("schedule %d ran %s late", schedule.ID, durationText(now.Sub(schedule.Due)))
 281                 } else {
 282                         s.logger.Printf("schedule %d ran", schedule.ID)
 283                 }
 284
 285                 turns = append(turns, message)
 286         }
 287
 288         l.Wake(turns...)
 289
 290         return nil
 291 }
 292
 293 // Due returns the schedules whose time is not after now, by due time.
 294 func (s *Schedules) Due(now time.Time) []Schedule {
 295         var due []Schedule
 296         for _, schedule := range s.sorted() {
 297                 if !schedule.Due.After(now) {
 298                         due = append(due, schedule)
 299                 }
 300         }
 301
 302         return due
 303 }
 304
 305 // Done ends the run of schedule at now: a one-time schedule goes, and a
 306 // repeating schedule gets the next time after now. So a repeating schedule that
 307 // missed several times runs once. When a remove took the schedule first, Done
 308 // changes nothing.
 309 func (s *Schedules) Done(schedule Schedule, now time.Time) error {
 310         s.mutex.Lock()
 311         defer s.mutex.Unlock()
 312
 313         index := slices.IndexFunc(s.file.Schedules, func(held Schedule) bool {
 314                 return held.ID == schedule.ID
 315         })
 316
 317         if index < 0 {
 318                 return nil
 319         }
 320
 321         if schedule.Cron == "" {
 322                 s.file.Schedules = slices.Delete(s.file.Schedules, index, index+1)
 323
 324                 return s.save()
 325         }
 326
 327         cron, err := scheduleParseCron(schedule.Cron)
 328         if err != nil {
 329                 return fmt.Errorf("schedule %d: %w", schedule.ID, err)
 330         }
 331
 332         next, found := cron.Next(now)
 333         if !found {
 334                 s.file.Schedules = slices.Delete(s.file.Schedules, index, index+1)
 335
 336                 return s.save()
 337         }
 338
 339         s.file.Schedules[index].Due = next
 340
 341         return s.save()
 342 }
 343
 344 // Wait returns how long after now the first schedule is due, or false when
 345 // there is no schedule.
 346 func (s *Schedules) Wait(now time.Time) (time.Duration, bool) {
 347         schedules := s.sorted()
 348         if len(schedules) == 0 {
 349                 return 0, false
 350         }
 351
 352         return max(schedules[0].Due.Sub(now), 0), true
 353 }
 354
 355 // change wakes Run after a set or a remove.
 356 func (s *Schedules) change() {
 357         select {
 358         case s.changed <- struct{}{}:
 359         default:
 360         }
 361 }
 362
 363 // sorted returns a copy of the schedules by due time, then by ID.
 364 func (s *Schedules) sorted() []Schedule {
 365         s.mutex.Lock()
 366         schedules := slices.Clone(s.file.Schedules)
 367         s.mutex.Unlock()
 368
 369         slices.SortFunc(schedules, func(a, b Schedule) int {
 370                 return cmp.Or(a.Due.Compare(b.Due), cmp.Compare(a.ID, b.ID))
 371         })
 372
 373         return schedules
 374 }
 375
 376 // save writes the file whole, with mode 0600. The caller holds the mutex.
 377 func (s *Schedules) save() error {
 378         data, err := json.Marshal(s.file)
 379         if err == nil {
 380                 err = writeFileAtomic(s.path, append(data, '\n'))
 381         }
 382
 383         if err != nil {
 384                 return fmt.Errorf("save schedules: %w", err)
 385         }
 386
 387         return nil
 388 }
 389
 390 // ScheduleFile is the content of the file of the schedules: the ID of the last
 391 // schedule, so that an ID is never used again, and the schedules.
 392 type ScheduleFile struct {
 393         Next      int        `json:"next"`
 394         Schedules []Schedule `json:"schedules"`
 395 }
 396
 397 // Schedule is one schedule: its ID, the task for the agent, the cron expression
 398 // of a repeating schedule, empty for a one-time schedule, and its next time.
 399 type Schedule struct {
 400         ID   int       `json:"id"`
 401         Text string    `json:"text"`
 402         Cron string    `json:"cron"`
 403         Due  time.Time `json:"due"`
 404 }
 405
 406 // Message returns the text of a run at now for the log, with the times in the
 407 // location of now. The first line starts with [Schedule ID] and gives the due
 408 // time and once or the cron expression. Then come the text, the line about a
 409 // late run when now is more than scheduleLate after the due time, and the line
 410 // about the empty reply.
 411 func (s Schedule) Message(now time.Time) string {
 412         lines := []string{
 413                 "[Schedule " + strconv.Itoa(s.ID) + "] " + s.Due.In(now.Location()).Format(scheduleTimeLayout) + ", " + s.repeats(),
 414                 s.Text,
 415         }
 416
 417         if s.late(now) {
 418                 lines = append(lines, scheduleLateLine)
 419         }
 420
 421         return strings.Join(append(lines, scheduleEmptyReply), "\n")
 422 }
 423
 424 // late tells if a run at now is late: more than scheduleLate after the due
 425 // time.
 426 func (s Schedule) late(now time.Time) bool {
 427         return now.Sub(s.Due) > scheduleLate
 428 }
 429
 430 // repeats returns once for a one-time schedule, or else repeats and the cron
 431 // expression.
 432 func (s Schedule) repeats() string {
 433         if s.Cron == "" {
 434                 return "once"
 435         }
 436
 437         return "repeats " + s.Cron
 438 }