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amfora/feeds/feeds.go
2020-08-28 19:33:37 -04:00

334 lines
6.9 KiB
Go

package feeds
import (
"crypto/sha256"
"encoding/json"
"errors"
"fmt"
"io"
"mime"
urlPkg "net/url"
"os"
"path"
"sort"
"strings"
"sync"
"time"
"github.com/makeworld-the-better-one/amfora/client"
"github.com/makeworld-the-better-one/amfora/config"
"github.com/makeworld-the-better-one/go-gemini"
"github.com/mmcdole/gofeed"
)
// TODO: Test for deadlocks and whether there should be more
// goroutines for file writing or other things.
var (
ErrSaving = errors.New("couldn't save JSON to disk")
ErrNotSuccess = errors.New("status 20 not returned")
ErrNotFeed = errors.New("not a valid feed")
)
var writeMu = sync.Mutex{} // Prevent concurrent writes to feeds.json file
// LastUpdated is the time when the in-memory data was last updated.
// It can be used to know if the feed page should be regenerated.
var LastUpdated time.Time
// Init should be called after config.Init.
func Init() error {
defer config.FeedJSON.Close()
dec := json.NewDecoder(config.FeedJSON)
err := dec.Decode(&data)
if err != nil && err != io.EOF {
return fmt.Errorf("feeds json is corrupted: %v", err) //nolint:goerr113
}
LastUpdated = time.Now()
go updateAll()
return nil
}
// IsTracked returns true if the feed/page URL is already being tracked.
func IsTracked(url string) bool {
data.feedMu.RLock()
for u := range data.Feeds {
if url == u {
data.feedMu.RUnlock()
return true
}
}
data.feedMu.RUnlock()
data.pageMu.RLock()
for u := range data.Pages {
if url == u {
data.pageMu.RUnlock()
return true
}
}
data.pageMu.RUnlock()
return false
}
// GetFeed returns a Feed object and a bool indicating whether the passed
// content was actually recognized as a feed.
func GetFeed(mediatype, filename string, r io.Reader) (*gofeed.Feed, bool) {
if r == nil {
return nil, false
}
// Check mediatype and filename
if mediatype != "application/atom+xml" && mediatype != "application/rss+xml" &&
filename != "atom.xml" && filename != "feed.xml" &&
!strings.HasSuffix(filename, ".atom") && !strings.HasSuffix(filename, ".rss") {
// No part of the above is true
return nil, false
}
feed, err := gofeed.NewParser().Parse(r)
if feed == nil {
return nil, false
}
return feed, err == nil
}
func writeJSON() error {
writeMu.Lock()
defer writeMu.Unlock()
f, err := os.OpenFile(config.FeedPath, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
return err
}
defer f.Close()
enc := json.NewEncoder(f)
enc.SetEscapeHTML(false)
enc.SetIndent("", " ")
data.Lock()
err = enc.Encode(&data)
data.Unlock()
return err
}
// AddFeed stores a feed.
// It can be used to update a feed for a URL, although the package
// will handle that on its own.
func AddFeed(url string, feed *gofeed.Feed) error {
if feed == nil {
panic("feed is nil")
}
// Remove any content to save memory and disk space
for _, item := range feed.Items {
item.Content = ""
}
data.feedMu.Lock()
data.Feeds[url] = feed
err := writeJSON()
if err != nil {
// Don't use in-memory if it couldn't be saved
delete(data.Feeds, url)
data.feedMu.Unlock()
return ErrSaving
}
data.feedMu.Unlock()
LastUpdated = time.Now()
return nil
}
// AddPage stores a page to track for changes.
// It can be used to update the page as well, although the package
// will handle that on its own.
func AddPage(url string, r io.Reader) error {
if r == nil {
return nil
}
h := sha256.New()
if _, err := io.Copy(h, r); err != nil {
return err
}
newHash := fmt.Sprintf("%x", h.Sum(nil))
data.pageMu.Lock()
_, ok := data.Pages[url]
if !ok || data.Pages[url].Hash != newHash {
// Page content is different, or it didn't exist
data.Pages[url] = &pageJSON{
Hash: newHash,
Changed: time.Now().UTC(),
}
}
err := writeJSON()
if err != nil {
// Don't use in-memory if it couldn't be saved
delete(data.Pages, url)
data.pageMu.Unlock()
return err
}
data.pageMu.Unlock()
LastUpdated = time.Now()
return nil
}
func updateFeed(url string) error {
res, err := client.Fetch(url)
if err != nil {
if res != nil {
res.Body.Close()
}
return err
}
defer res.Body.Close()
if res.Status != gemini.StatusSuccess {
return ErrNotSuccess
}
mediatype, _, err := mime.ParseMediaType(res.Meta)
if err != nil {
return err
}
filename := path.Base(url)
feed, ok := GetFeed(mediatype, filename, res.Body)
if !ok {
return ErrNotFeed
}
return AddFeed(url, feed)
}
func updatePage(url string) error {
res, err := client.Fetch(url)
if err != nil {
if res != nil {
res.Body.Close()
}
return err
}
defer res.Body.Close()
if res.Status != gemini.StatusSuccess {
return ErrNotSuccess
}
return AddPage(url, res.Body)
}
// updateAll updates all feeds and pages.
func updateAll() {
// TODO: Is two goroutines the right amount?
worker := func(jobs <-chan [2]string, wg *sync.WaitGroup) {
// Each job is: [2]string{<type>, "url"}
// where <type> is "feed" or "page"
defer wg.Done()
for j := range jobs {
if j[0] == "feed" {
updateFeed(j[1]) //nolint:errcheck
} else if j[0] == "page" {
updatePage(j[1]) //nolint:errcheck
}
}
}
var wg sync.WaitGroup
data.RLock()
numJobs := len(data.Feeds) + len(data.Pages)
jobs := make(chan [2]string, numJobs)
// Start 2 workers, waiting for jobs
for w := 0; w < 2; w++ {
wg.Add(1)
go worker(jobs, &wg)
}
// Get map keys in a slice
feedKeys := make([]string, len(data.Feeds))
i := 0
for k := range data.Feeds {
feedKeys[i] = k
i++
}
pageKeys := make([]string, len(data.Pages))
i = 0
for k := range data.Pages {
pageKeys[i] = k
i++
}
data.RUnlock()
for j := 0; j < numJobs; j++ {
if j < len(feedKeys) {
jobs <- [2]string{"feed", feedKeys[j]}
} else {
// In the Pages
jobs <- [2]string{"page", pageKeys[j-len(feedKeys)]}
}
}
wg.Wait()
}
// GetPageEntries returns the current list of PageEntries
// for use in rendering a page.
// The contents of the returned entries will never change,
// so this function needs to be called again to get updates.
// It always returns sorted entries - by post time, from newest to oldest.
func GetPageEntries() *PageEntries {
var pe PageEntries
data.RLock()
for _, feed := range data.Feeds {
for _, item := range feed.Items {
var pub time.Time
// Try to use updated time first, then published
if !item.UpdatedParsed.IsZero() {
pub = *item.UpdatedParsed
} else if !item.PublishedParsed.IsZero() {
pub = *item.PublishedParsed
} else {
// No time on the post
pub = time.Now()
}
pe.Entries = append(pe.Entries, &PageEntry{
Author: feed.Author.Name,
Title: item.Title,
URL: item.Link,
Published: pub,
})
}
}
for url, page := range data.Pages {
parsed, _ := urlPkg.Parse(url)
pe.Entries = append(pe.Entries, &PageEntry{
Author: parsed.Host, // Domain is author
Title: path.Base(parsed.Path), // Filename is title
URL: url,
Published: page.Changed,
})
}
data.RUnlock()
sort.Sort(&pe)
return &pe
}