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// SPDX-License-Identifier: ISC
// Copyright © 2020 rsiddharth <rsiddharth@ninthfloor.org>
package main
import (
"encoding/json"
"encoding/xml"
"flag"
"fmt"
"io"
"net/http"
"os"
"os/exec"
"path"
"strings"
)
type Link struct {
XMLName xml.Name `xml:"link"`
Href string `xml:"href,attr"`
}
type Entry struct {
XMLName xml.Name `xml:"entry"`
Id string `xml:"id"`
Title string `xml:"title"`
Link Link
}
type Feed struct {
XMLName xml.Name `xml:"feed"`
Entry []Entry `xml:"entry"`
}
type Ids []string
const sendmail string = "/usr/sbin/sendmail"
var emailTo string
func init() {
flag.StringVar(&emailTo, "t", "", "Email address for sending emails to")
}
func newsFeed() ([]byte, error) {
// Init feed.
feed := make([]byte, 0)
resp, err := http.Get("https://fsf.org.in/news/feed.atom")
if err != nil {
return feed, err
}
// Read feed.
chunk := make([]byte, 100)
for {
c, err := resp.Body.Read(chunk)
if c < 1 {
break
}
if err != nil && err != io.EOF {
return feed, err
}
feed = append(feed, chunk[0:c]...)
}
return feed, nil
}
func parseFeed(feed []byte) (Feed, error) {
f := Feed{}
err := xml.Unmarshal(feed, &f)
if err != nil {
return f, err
}
return f, nil
}
func readFile(f *os.File) ([]byte, error) {
bs, chunk := make([]byte, 0), make([]byte, 10)
for {
n, err := f.Read(chunk)
if err != nil && err != io.EOF {
return bs, err
}
bs = append(bs, chunk[0:n]...)
if err == io.EOF {
break
}
}
return bs, nil
}
func writeFile(f os.File, cache Ids) error {
bs, err := json.Marshal(cache)
if err != nil {
return err
}
n, err := f.Write(bs)
if n != len(bs) {
return err
}
return nil
}
func cacheFor(section string) (Ids, error) {
cache := make(Ids, 0)
h := os.Getenv("HOME")
d := path.Join(h, ".cedar")
err := os.MkdirAll(d, 0700)
if err != nil {
return cache, err
}
f, err := os.Open(path.Join(d, section+".json"))
if os.IsNotExist(err) {
return cache, nil
}
bs, err := readFile(f)
if len(bs) == 0 || err != nil {
return cache, err
}
err = json.Unmarshal(bs, &cache)
if err != nil {
return cache, err
}
return cache, nil
}
func (cache *Ids) add(entry Entry) {
n := len(*cache)
// Expand cache
c := make(Ids, n+1)
copy(c, *cache)
// Cache entry
c[n] = entry.Id
*cache = c
}
func (cache Ids) save(section string) error {
h, _ := os.UserHomeDir()
d := path.Join(h, ".cedar")
f, err := os.OpenFile(path.Join(d, section+".json"),
os.O_CREATE|os.O_WRONLY,
0600)
if err != nil {
return err
}
err = writeFile(*f, cache)
if err != nil {
return err
}
return nil
}
func (entry Entry) in(cache Ids) bool {
for i := 0; i < len(cache); i++ {
if entry.Id == cache[i] {
return true
}
}
return false
}
func (entry Entry) makeEmail(section string) string {
return fmt.Sprintf(`To: %s
Subject: FSF India - %s - %s
FSF India published "%s":
%s
`,
emailTo,
strings.Title(section),
entry.Title,
entry.Title,
entry.Link.Href)
}
func (entry Entry) email(section string) error {
cmd := exec.Command(sendmail, "-t")
stdin, err := cmd.StdinPipe()
if err != nil {
return err
}
io.WriteString(stdin, entry.makeEmail(section))
stdin.Close()
_, err = cmd.CombinedOutput()
if err != nil {
return err
}
fmt.Printf("Successfully sent %s to %s\n",
entry.Id, emailTo)
return nil
}
func processNews() error {
newsXML, err := newsFeed()
if err != nil {
return err
}
news, err := parseFeed(newsXML)
if err != nil {
return err
}
cache, err := cacheFor("news")
if err != nil {
return err
}
for i := 0; i < len(news.Entry); i++ {
if news.Entry[i].in(cache) {
continue
}
err := news.Entry[i].email("news")
if err != nil {
return err
}
cache.add(news.Entry[i])
}
err = cache.save("news")
if err != nil {
return err
}
return nil
}
func main() {
flag.Parse()
// Quit if emailTo is not set.
if flag.NFlag() != 1 {
flag.PrintDefaults()
return
}
err := processNews()
if err != nil {
fmt.Printf("Error: %v\n", err.Error())
}
}
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