///bin/sh -c true; exec /usr/bin/env go run "$0" "$@"
package main

import (
	"encoding/json"
	"io/ioutil"
	"net/url"
	"os"
	"os/exec"
	"path"
	"strings"
	"text/template"
	"time"

	"github.com/russross/blackfriday/v2"
)

const (
	CACHE_FOLDER = "cache"
)

const RSS_TEMPLATE string = `<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/">
<channel>
<title><![CDATA[ {{.ID}} ]]></title>
<link><![CDATA[ {{.Server}}/{{.ID}} ]]></link>
<description><![CDATA[ {{.ID}} ]]></description>

    <item>
      <title><![CDATA[ {{.Server}}/{{.ID}} ]]></title>
      <content:encoded><![CDATA[ {{.Content}} ]]></content:encoded>
      <guid><![CDATA[ {{.Server}}/{{.ID}}/{{.Modified.Format "20060102-150405"}} ]]></guid>
      <link><![CDATA[ {{.Server}}/{{.ID}} ]]></link>
      <pubDate>{{.Modified.Format "Mon, 02 Jan 2006 15:04:05 -0700"}}</pubDate>
    </item>

</channel>
</rss>
`

func optPanic(err error) {
	if err != nil {
		panic(err)
	}
}

func (n *Note) filename() string {
	return path.Join(CACHE_FOLDER, n.ID)
}

func (n *Note) setContent() {
	cmd := exec.Command("hedgedoc", "export", "--md", n.ID)
	cmd.Env = os.Environ()
	cmd.Env = append(cmd.Env, "HEDGEDOC_SERVER="+n.Server)
	if n.CookiesFile != "" {
		cmd.Env = append(cmd.Env, "HEDGEDOC_COOKIES_FILE="+n.CookiesFile)
	}
	filename, err := cmd.Output()
	optPanic(err)
	b, err := ioutil.ReadFile(strings.TrimSpace(string(filename)))
	optPanic(err)
	n.Content = string(blackfriday.Run(b))
	n.Modified = time.Now()
}

func unmarshalNoteObject(filename string) Note {
	bytes, err := ioutil.ReadFile(filename)
	if err != nil {
		bytes = []byte{}
	}
	var noteObject Note
	err = json.Unmarshal(bytes, &noteObject)
	if err != nil {
		noteObject = Note{}
	}
	return noteObject
}

func marshalNoteObject(filename string, note Note) {
	bytes, err := json.MarshalIndent(note, "", "  ")
	optPanic(err)
	err = ioutil.WriteFile(filename, bytes, 0644)
	optPanic(err)
}

func (newNote *Note) genRSS() {
	var chosen Note
	oldNote := unmarshalNoteObject(newNote.filename())
	if oldNote.Content != newNote.Content {
		chosen = *newNote
	} else {
		chosen = oldNote
	}
	err := rssTemplate.Execute(os.Stdout, chosen)
	optPanic(err)
	marshalNoteObject(newNote.filename(), chosen)
}

type Note struct {
	Server      string
	ID          string
	Content     string
	Modified    time.Time
	CookiesFile string
}

func NewNote(server string, ID string) *Note {
	n := &Note{Server: server, ID: ID}
	n.setContent()
	return n
}

var rssTemplate *template.Template

func rssify(noteURL string) {
	u, err := url.Parse(noteURL)
	optPanic(err)
	NewNote(u.Scheme+"://"+u.Host, u.Path[1:]).genRSS()
}

func main() {
	rssTemplate = template.Must(template.New("rss").Parse(RSS_TEMPLATE))
	os.Mkdir(CACHE_FOLDER, 0755)
	// todo: Cookie-file flag
	rssify(os.Args[1])
}