From c8681ba96cd6853812cd28b15088cedfe145739f Mon Sep 17 00:00:00 2001
From: Jan-Lukas Else <mail@jlelse.de>
Date: Sun, 5 Apr 2020 21:28:18 +0200
Subject: [PATCH] Add initial version

---
 .gitignore            |  1 +
 Dockerfile            | 13 ++++++++
 Feed.go               | 35 +++++++++++++++++++++
 JsonFeedToTelegram.go | 73 +++++++++++++++++++++++++++++++++++++++++++
 Telegram.go           | 31 ++++++++++++++++++
 go.mod                |  3 ++
 6 files changed, 156 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Dockerfile
 create mode 100644 Feed.go
 create mode 100644 JsonFeedToTelegram.go
 create mode 100644 Telegram.go
 create mode 100644 go.mod

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..62c8935
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea/
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..33f8240
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,13 @@
+FROM golang:1.14-alpine as build
+ADD . /app
+WORKDIR /app
+RUN go build
+
+FROM alpine:3.11
+RUN apk add --no-cache tzdata ca-certificates
+COPY --from=build /app/JsonFeedToTelegram /bin/
+WORKDIR /app
+VOLUME /app/storage
+EXPOSE 8080
+ENV LAST_ARTICLE_FILE /app/storage/lastarticle
+CMD ["JsonFeedToTelegram"]
\ No newline at end of file
diff --git a/Feed.go b/Feed.go
new file mode 100644
index 0000000..7707462
--- /dev/null
+++ b/Feed.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+)
+
+type Article struct {
+	Title string `json:"title"`
+	Url   string `json:"url"`
+}
+
+func LatestArticle(url string) (*Article, error) {
+	jsonFeed := &struct {
+		Items []Article `json:"items"`
+	}{}
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return nil, errors.New("failed to create req to get json feed")
+	}
+	req.Header.Add("User-Agent", "JsonFeedToTelegram")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, errors.New("failed to get json feed")
+	}
+	err = json.NewDecoder(resp.Body).Decode(&jsonFeed)
+	if err != nil {
+		return nil, errors.New("failed to parse json feed")
+	}
+	if len(jsonFeed.Items) < 1 {
+		return nil, errors.New("no articles in feed")
+	}
+	return &jsonFeed.Items[0], nil
+}
diff --git a/JsonFeedToTelegram.go b/JsonFeedToTelegram.go
new file mode 100644
index 0000000..75291d6
--- /dev/null
+++ b/JsonFeedToTelegram.go
@@ -0,0 +1,73 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"time"
+)
+
+func main() {
+	lastArticleFile, lastArticleFileSet := os.LookupEnv("LAST_ARTICLE_FILE")
+	feed, feedSet := os.LookupEnv("FEED")
+	botToken, botTokenSet := os.LookupEnv("BOT_TOKEN")
+	channel, channelSet := os.LookupEnv("CHANNEL")
+	if lastArticleFileSet && feedSet && botTokenSet && channelSet {
+		telegram := Telegram{botToken: botToken, channel: channel}
+		http.HandleFunc("/hook", func(w http.ResponseWriter, r *http.Request) {
+			if r.Method != http.MethodPost {
+				http.Error(w, "Wrong HTTP method", http.StatusMethodNotAllowed)
+				return
+			}
+			fmt.Println("Fetch feed: ", time.Now().Format(time.RFC3339))
+			article, err := LatestArticle(feed)
+			if err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			if lastArticle := lastArticleUrl(lastArticleFile); lastArticle != article.Url {
+				err = telegram.Post(createMessage(article))
+				if err != nil {
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+				err = updateLastArticleUrl(lastArticleFile, article.Url)
+				if err != nil {
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+			} else {
+				http.Error(w, errors.New("no new article").Error(), http.StatusInternalServerError)
+				return
+			}
+		})
+		log.Fatal(http.ListenAndServe(":8080", nil))
+	} else {
+		log.Fatal("Not configured")
+	}
+}
+
+func lastArticleUrl(filename string) string {
+	fileContent, _ := ioutil.ReadFile(filename)
+	return string(fileContent)
+}
+
+func updateLastArticleUrl(filename, url string) error {
+	return ioutil.WriteFile(filename, []byte(url), 0644)
+}
+
+func createMessage(article *Article) string {
+	var message bytes.Buffer
+	message.WriteString("🔔 Something new was published")
+	message.WriteString("\n\n")
+	if article.Title != "" {
+		message.WriteString(article.Title)
+		message.WriteString("\n\n")
+	}
+	message.WriteString(article.Url)
+	return message.String()
+}
diff --git a/Telegram.go b/Telegram.go
new file mode 100644
index 0000000..63bfa74
--- /dev/null
+++ b/Telegram.go
@@ -0,0 +1,31 @@
+package main
+
+import (
+	"errors"
+	"net/http"
+	"net/url"
+)
+
+type Telegram struct {
+	channel  string
+	botToken string
+}
+
+var telegramBaseUrl = "https://api.telegram.org/bot"
+
+func (t *Telegram) Post(message string) error {
+	params := url.Values{}
+	params.Add("chat_id", t.channel)
+	params.Add("text", message)
+	tgUrl, err := url.Parse(telegramBaseUrl + t.botToken + "/sendMessage")
+	if err != nil {
+		return errors.New("failed to create Telegram request")
+	}
+	tgUrl.RawQuery = params.Encode()
+	req, _ := http.NewRequest(http.MethodPost, tgUrl.String(), nil)
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil || resp.StatusCode != 200 {
+		return errors.New("failed to send Telegram message")
+	}
+	return nil
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..655f63a
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.jlel.se/jlelse/JsonFeedToTelegram
+
+go 1.14