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|
package schedule
import (
"bufio"
"encoding/xml"
"fmt"
"net/http"
"sync"
"time"
)
type Service interface {
GetSchedule() (*Schedule, time.Time, error)
GetEventByID(id int32) *Event
}
type service struct {
pentabarfUrl string
schedule *Schedule
eventsById map[int32]Event
lastUpdated time.Time
accessLock sync.RWMutex
updateLock sync.Mutex
}
// TODO: Create a service implementation that persists to DB
// and isn't in memory
func NewService(pentabarfUrl string) (Service, error) {
service := &service{
pentabarfUrl: pentabarfUrl,
lastUpdated: time.Unix(0, 0),
}
err := service.updateSchedule()
if err != nil {
return nil, fmt.Errorf("could not read schedule from '%s' (is it a valid pentabarf XML file?): %w", pentabarfUrl, err)
}
return service, nil
}
func (s *service) GetSchedule() (*Schedule, time.Time, error) {
err := s.updateSchedule()
if err != nil {
return nil, time.Time{}, err
}
s.accessLock.RLock()
defer s.accessLock.RUnlock()
return s.schedule, s.lastUpdated, nil
}
func (s *service) GetEventByID(id int32) *Event {
s.accessLock.RLock()
defer s.accessLock.RUnlock()
event := s.eventsById[id]
return &event
}
func (s *service) hasScheduleExpired() bool {
expire := s.lastUpdated.Add(15 * time.Minute)
return time.Now().After(expire)
}
func (s *service) updateSchedule() error {
if !s.hasScheduleExpired() {
return nil
}
if !s.updateLock.TryLock() {
// don't block if another goroutine is already fetching
return nil
}
defer s.updateLock.Unlock()
res, err := http.Get(s.pentabarfUrl)
if err != nil {
return err
}
reader := bufio.NewReader(res.Body)
var schedule schedule
decoder := xml.NewDecoder(reader)
if err := decoder.Decode(&schedule); err != nil {
return fmt.Errorf("failed to decode XML: %w", err)
}
var newSchedule Schedule
err = newSchedule.Scan(schedule)
if err != nil {
return fmt.Errorf("failed to scan schedule: %w", err)
}
s.accessLock.Lock()
defer s.accessLock.Unlock()
s.schedule = &newSchedule
s.lastUpdated = time.Now()
s.eventsById = make(map[int32]Event)
for _, day := range newSchedule.Days {
for _, room := range day.Rooms {
for _, event := range room.Events {
s.eventsById[event.ID] = event
}
}
}
return nil
}
|
