reaper/reaper.go
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package reaper
import (
"fmt"
"sort"
"sync"
"time"
"git.j3s.sh/vore/rss"
"git.j3s.sh/vore/sqlite"
)
type Reaper struct {
// internal list of all rss feeds where the map
// key represents the primary id of the key in the db
feeds []rss.Feed
// this mutex is used for locking writes to Feeds
mu sync.Mutex
db *sqlite.DB
}
func Summon(db *sqlite.DB) *Reaper {
reaper := Reaper{
feeds: []rss.Feed{},
mu: sync.Mutex{},
db: db,
}
return &reaper
}
// Start initializes the reaper by populating the feeds list from the database
// and periodically refreshes all feeds every 15 minutes, as needed.
func (r *Reaper) Start() {
// Make initial url list
urls := r.db.GetAllFeedURLs()
for _, url := range urls {
// Setting UpdateURL lets us defer fetching
feed := rss.Feed{
UpdateURL: url,
}
r.feeds = append(r.feeds, feed)
}
for {
r.refreshAllFeeds()
time.Sleep(15 * time.Minute)
}
}
// Add the given rss feed to Reaper for maintenance.
// If the given feed is already in reaper.Feeds, Add does nothing.
func (r *Reaper) addFeed(f rss.Feed) {
if !r.HasFeed(f.UpdateURL) {
r.mu.Lock()
r.feeds = append(r.feeds, f)
r.mu.Unlock()
}
}
// UpdateAll fetches every feed & attempts updating them
// asynchronously, then prints the duration of the sync
func (r *Reaper) refreshAllFeeds() {
start := time.Now()
var wg sync.WaitGroup
for i := range r.feeds {
if r.feeds[i].Stale() {
wg.Add(1)
go func(f *rss.Feed) {
defer wg.Done()
r.refreshFeed(f)
}(&r.feeds[i])
}
}
wg.Wait()
fmt.Printf("reaper: refresh complete in %s\n", time.Since(start))
}
// refreshFeed triggers a fetch on the given feed,
// and sets a fetch error in the db if there is one.
func (r *Reaper) refreshFeed(f *rss.Feed) {
err := f.Update()
if err != nil {
r.handleFeedFetchFailure(f.UpdateURL, err)
}
}
func (r *Reaper) handleFeedFetchFailure(url string, err error) {
fmt.Printf("[err] reaper: fetch failure '%s': %s\n", url, err)
err = r.db.SetFeedFetchError(url, err.Error())
if err != nil {
fmt.Printf("[err] reaper: could not set feed fetch error '%s'\n", err)
}
}
// Have checks whether a given url is represented
// in the reaper cache.
func (r *Reaper) HasFeed(url string) bool {
for _, f := range r.feeds {
if f.UpdateURL == url {
return true
}
}
return false
}
// GetUserFeeds returns a list of feeds
func (r *Reaper) GetUserFeeds(username string) []rss.Feed {
urls := r.db.GetUserFeedURLs(username)
var result []rss.Feed
for i := range r.feeds {
for _, url := range urls {
if r.feeds[i].UpdateURL == url {
result = append(result, r.feeds[i])
}
}
}
r.SortFeeds(result)
return result
}
func (r *Reaper) SortFeeds(f []rss.Feed) {
sort.Slice(f, func(i, j int) bool {
return f[i].UpdateURL < f[j].UpdateURL
})
}
func (r *Reaper) SortFeedItemsByDate(feeds []rss.Feed) []rss.Item {
var posts []rss.Item
for _, f := range feeds {
for _, i := range f.Items {
posts = append(posts, *i)
}
}
sort.Slice(posts, func(i, j int) bool {
return posts[i].Date.After(posts[j].Date)
})
return posts
}
// FetchFeed attempts to fetch a feed from a given url, marshal
// it into a feed object, and add it to Reaper.
func (r *Reaper) Fetch(url string) error {
feed, err := rss.Fetch(url)
if err != nil {
return err
}
r.addFeed(*feed)
return nil
}