feed/feed.go

package main

import (
	"encoding/xml"
	"log"
	"strings"
	"time"

	"github.com/timshannon/bolthold"
	"go.etcd.io/bbolt"
)

const (
	rssPre = `<?xml version="1.0" encoding="UTF-8" ?>
`
	rfc2822 = "Mon, 02 Jan 2006 15:04:05 +0700"
)

type queueItem struct {
	URL   string `boltholdKey:"URL"`
	Date  time.Time
	Votes int
}

type feedItem struct {
	Date      time.Time `boltholdKey:"date"`
	URL       string    `boltholdIndex:"URL"`
	Title     string
	Excerpt   string
	Authors   []string
	WordCount int
	ImageURL  string
}

type feed struct {
	db      *bolthold.Store
	fetcher contentFetcher
}

func newFeed(dbPath string, fetcher contentFetcher) (*feed, error) {
	db, err := bolthold.Open(dbPath, 0660, nil)
	if err != nil {
		return nil, err
	}
	f := feed{
		db:      db,
		fetcher: fetcher,
	}
	go f.feeder()
	return &f, nil
}

func (f *feed) close() error {
	return f.db.Close()
}

func (f *feed) feeder() {
	for {
		last4Hours := time.Now().Add(time.Hour * -4)
		items4Hours, err := f.db.Count(&feedItem{}, bolthold.Where("Date").Gt(last4Hours))
		if err != nil {
			log.Printf("Error getting last update: %v", err)
		} else if items4Hours == 0 {
			f.publish()
		}
		time.Sleep(time.Minute * 10)
	}
}

func (f *feed) publish() {
	var item queueItem
	err := f.db.FindOne(&item, bolthold.Where("Votes").Ge(1).SortBy("Votes", "Date").Limit(1))
	if err != nil {
		if err != bolthold.ErrNotFound {
			log.Printf("Error fetching an item to publish from the queue: %v", err)
		}
		return
	}

	content, err := f.fetcher.fetchContent(item.URL)
	if err != nil {
		log.Printf("Error fetching content from pocket: %v", err)
		return
	}
	publishItem := feedItem{
		Date:     time.Now(),
		URL:      item.URL,
		Title:    content.title,
		Excerpt:  content.excerpt,
		Authors:  content.authors,
		ImageURL: content.imageURL,
	}
	err = f.db.Insert(publishItem.Date, &publishItem)
	if err != nil {
		log.Printf("Error inserting %s: %v", item.URL, err)
		return
	}
	err = f.db.Delete(item.URL, &item)
	if err != nil {
		log.Printf("Error deleting %s from queue: %v", item.URL, err)
	}
}

func (f *feed) add(url string) error {
	published, err := f.db.Count(&feedItem{}, bolthold.Where("URL").Eq(url))
	if err != nil {
		log.Printf("Error checking if already published %s: %v", url, err)
	}
	if published != 0 {
		log.Printf("Already published %s", url)
		return nil
	}

	return f.db.Bolt().Update(func(tx *bbolt.Tx) error {
		var item queueItem
		err := f.db.TxGet(tx, url, &item)
		if err != nil {
			if err != bolthold.ErrNotFound {
				return err
			}

			item.URL = url
			item.Date = time.Now()
		}
		item.Votes++
		return f.db.TxUpsert(tx, url, &item)
	})
}

type rss struct {
	Channel Channel `xml:"channel"`
	Version string  `xml:"version,attr"`
	DC      string  `xml:"xmlns:dc,attr"`
}

type Channel struct {
	Title         string       `xml:"title"`
	Link          string       `xml:"link"`
	Description   string       `xml:"description"`
	LastBuildDate string       `xml:"lastBuildDate"`
	Image         ChannelImage `xml:"image"`
	Item          []Item       `xml:"item"`
}

type ChannelImage struct {
	URL   string `xml:"url"`
	Title string `xml:"title"`
	Link  string `xml:"link"`
}

type Item struct {
	Title       string   `xml:"title"`
	DCCreator   []string `xml:"dc:creator"`
	Description string   `xml:"description"`
	Link        string   `xml:"link"`
	PubDate     string   `xml:"pubDate"`
	GUID        string   `xml:"guid"`
}

func (f feed) items() []feedItem {
	var items []feedItem
	err := f.db.Find(&items, bolthold.Where("Date").Gt(time.Unix(0, 0)).SortBy("Date").Reverse())
	if err != nil {
		log.Printf("Error reading feed db bucket: %v", err)
	}
	return items
}

func (f feed) rss() string {
	channel := Channel{
		Title:       "Farenheit 2577",
		Link:        "https://sindominio.net/2577",
		Description: "News from the distopian present",
		Image: ChannelImage{
			URL:   "https://sindominio.net/2577/2577.png",
			Title: "Farenheit 2577",
			Link:  "https://sindominio.net/2577",
		},
		LastBuildDate: time.Now().Format(rfc2822),
	}
	err := f.db.ForEach(bolthold.Where("Date").Gt(time.Unix(0, 0)).SortBy("Date").Reverse(),
		func(item *feedItem) error {
			description := ""
			if item.ImageURL != "" {
				description = "<img src=\"" + item.ImageURL + "\" alt=\"header\">"
			}
			description += "<p>" + strings.Replace(item.Excerpt, "\n", "</p><p>", -1) + "</p>"
			channel.Item = append(channel.Item, Item{
				Title:       item.Title,
				DCCreator:   item.Authors,
				Description: description,
				Link:        item.URL,
				GUID:        item.URL,
				PubDate:     item.Date.Format(rfc2822),
			})
			return nil
		})
	if err != nil {
		log.Printf("Can't read the feed database: %v", err)
		return ""
	}
	buff, err := xml.MarshalIndent(rss{channel, "2.0", "http://purl.org/dc/elements/1.1/"}, "", "  ")
	if err != nil {
		log.Printf("Can't marshal rss: %v", err)
		return ""
	}
	return rssPre + string(buff)
}