Simple go application to build a RSS feed from a mastodon status URL

replyfetcher.go

package main

import (
	"encoding/json"
	"encoding/xml"
	"fmt"
	"log"
	"math"
	"net/http"
	"os"
	"time"
)

type Status struct {
	Descendants []struct {
		Account struct {
			Username    string
			DisplayName string \`json:"display_name"\`
		}
		CreatedAt time.Time \`json:"created_at"\`
		Content   string
		Url       string
	}
}

type Item struct {
	PubDate     time.Time \`xml:"pubDate"\`
	Title       string    \`xml:"title"\`
	Description string    \`xml:"description"\`
	Link        string    \`xml:"link"\`
}

type Channel struct {
	Title string \`xml:"title"\`
	Link  string \`xml:"link"\`
	Item  []Item \`xml:"item"\`
}

type Rss struct {
	XMLName xml.Name \`xml:"rss"\`
	Channel Channel  \`xml:"channel"\`
}

func main() {
	// application to generate a RSS feed from mastodon status URL like
	//
	// use like this in a crontab: replyfetcher https://social.tchncs.de/api/v1/statuses/113474228564749371/context > feed.rss

	if len(os.Args) < 2 {
		log.Fatalf("Usage: %s <url to status>", os.Args[0])
	}
	url := os.Args[1]
	resp, err := http.Get(url)
	if err != nil || resp.StatusCode >= 400 {
		log.Fatalf("Can not get status: %v %v", err, resp.Status)
	}
	var content Status
	err = json.NewDecoder(resp.Body).Decode(&content)
	if err != nil {
		log.Fatalf("Can not decode json: %v", err)
	}
	feed := Rss{
		Channel: Channel{
			Title: url,
			Link:  url,
		},
	}
	for _, descendant := range content.Descendants {
		user := descendant.Account.Username
		if descendant.Account.DisplayName != "" {
			user = descendant.Account.DisplayName
		}
		maxlength := int(math.Min(100, float64(len(descendant.Content))))
		title := descendant.Content[0:maxlength]
		feed.Channel.Item = append(feed.Channel.Item, Item{
			PubDate:     descendant.CreatedAt,
			Title:       fmt.Sprintf("%s: %s", user, title),
			Description: descendant.Content,
			Link:        descendant.Url,
		})
	}
	xmlContent, _ := xml.MarshalIndent(feed, "", "  ")
	fmt.Printf("<?xml version=\\"1.0\\" encoding=\\"utf-8\\"?>\\n%s", xmlContent)
}