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package conference
import (
"bufio"
"context"
"encoding/xml"
"errors"
"fmt"
"net/http"
"sync"
"time"
"github.com/LMBishop/confplanner/pkg/database/sqlc"
"github.com/jackc/pgx/v5/pgtype"
"github.com/jackc/pgx/v5/pgxpool"
)
type Service interface {
CreateConference(url string) (*sqlc.Conference, error)
DeleteConference(id int32) error
GetConferences() ([]sqlc.Conference, error)
GetSchedule(id int32) (*Schedule, time.Time, error)
GetEventByID(conferenceID, eventID int32) (*Event, error)
}
type loadedConference struct {
pentabarfUrl string
schedule *Schedule
eventsById map[int32]Event
lastUpdated time.Time
lock sync.RWMutex
}
var (
ErrConferenceNotFound = errors.New("conference not found")
ErrScheduleFetch = errors.New("could not fetch schedule")
)
type service struct {
conferences map[int32]*loadedConference
lock sync.RWMutex
pool *pgxpool.Pool
}
// TODO: Create a service implementation that persists to DB
// and isn't in memory
func NewService(pool *pgxpool.Pool) (Service, error) {
service := &service{
pool: pool,
conferences: make(map[int32]*loadedConference),
}
queries := sqlc.New(pool)
conferences, err := queries.GetConferences(context.Background())
if err != nil {
return nil, err
}
for _, conference := range conferences {
c := &loadedConference{
pentabarfUrl: conference.Url,
lastUpdated: time.Unix(0, 0),
}
service.conferences[conference.ID] = c
}
return service, nil
}
func (s *service) CreateConference(url string) (*sqlc.Conference, error) {
s.lock.Lock()
defer s.lock.Unlock()
c := &loadedConference{
pentabarfUrl: url,
lastUpdated: time.Unix(0, 0),
}
err := c.updateSchedule()
if err != nil {
return nil, errors.Join(ErrScheduleFetch, err)
}
queries := sqlc.New(s.pool)
conference, err := queries.CreateConference(context.Background(), sqlc.CreateConferenceParams{
Url: url,
Title: pgtype.Text{String: c.schedule.Conference.Title, Valid: true},
Venue: pgtype.Text{String: c.schedule.Conference.Venue, Valid: true},
City: pgtype.Text{String: c.schedule.Conference.City, Valid: true},
})
if err != nil {
return nil, fmt.Errorf("could not create conference: %w", err)
}
s.conferences[conference.ID] = c
return &conference, nil
}
func (s *service) DeleteConference(id int32) error {
s.lock.Lock()
defer s.lock.Unlock()
queries := sqlc.New(s.pool)
err := queries.DeleteConference(context.Background(), id)
if err != nil {
return fmt.Errorf("could not delete conference: %w", err)
}
delete(s.conferences, id)
return nil
}
func (s *service) GetConferences() ([]sqlc.Conference, error) {
s.lock.RLock()
defer s.lock.RUnlock()
queries := sqlc.New(s.pool)
return queries.GetConferences(context.Background())
}
func (s *service) GetSchedule(id int32) (*Schedule, time.Time, error) {
s.lock.RLock()
defer s.lock.RUnlock()
c, ok := s.conferences[id]
if !ok {
return nil, time.Time{}, ErrConferenceNotFound
}
if err := c.updateSchedule(); err != nil {
return nil, time.Time{}, err
}
c.lock.RLock()
defer c.lock.RUnlock()
queries := sqlc.New(s.pool)
if _, err := queries.UpdateConferenceDetails(context.Background(), sqlc.UpdateConferenceDetailsParams{
ID: id,
Title: pgtype.Text{String: c.schedule.Conference.Title, Valid: true},
Venue: pgtype.Text{String: c.schedule.Conference.Venue, Valid: true},
City: pgtype.Text{String: c.schedule.Conference.City, Valid: true},
}); err != nil {
return nil, time.Time{}, fmt.Errorf("failed to update cached conference details: %w", err)
}
return c.schedule, c.lastUpdated, nil
}
func (s *service) GetEventByID(conferenceID, eventID int32) (*Event, error) {
s.lock.RLock()
defer s.lock.RUnlock()
c, ok := s.conferences[conferenceID]
if !ok {
return nil, ErrConferenceNotFound
}
c.lock.RLock()
defer c.lock.RUnlock()
event := c.eventsById[eventID]
return &event, nil
}
func (c *loadedConference) hasScheduleExpired() bool {
expire := c.lastUpdated.Add(15 * time.Minute)
return time.Now().After(expire)
}
func (c *loadedConference) updateSchedule() error {
if !c.hasScheduleExpired() {
return nil
}
if !c.lock.TryLock() {
// don't block if another goroutine is already fetching
return nil
}
defer c.lock.Unlock()
res, err := http.Get(c.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)
}
c.schedule = &newSchedule
c.lastUpdated = time.Now()
c.eventsById = make(map[int32]Event)
for _, day := range newSchedule.Days {
for _, room := range day.Rooms {
for _, event := range room.Events {
c.eventsById[event.ID] = event
}
}
}
return nil
}
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