package main

/*
This is a minimal sample application, demonstrating how to set up an RSS feed
for regular polling of new channels/items.

Build & run with:

 $ go run example.go

*/

import (
	"errors"
	"fmt"
	"io"
	"os"
	"time"

	rss "github.com/jteeuwen/go-pkg-rss"
	"github.com/jteeuwen/go-pkg-xmlx"
)

func main() {
	// This sets up a new feed and polls it for new channels/items.
	// Invoking it with 'go PollFeed(...)' to have the polling performed in a
	// separate goroutine, so we can poll mutiple feeds.
	go PollFeed("http://blog.case.edu/news/feed.atom", 5, nil)

	// Poll with a custom charset reader. This is to avoid the following error:
	// ... xml: encoding "ISO-8859-1" declared but Decoder.CharsetReader is nil.
	PollFeed("https://status.rackspace.com/index/rss", 5, charsetReader)
}

func PollFeed(uri string, timeout int, cr xmlx.CharsetFunc) {
	feed := rss.New(timeout, true, chanHandler, itemHandler)

	for {
		if err := feed.Fetch(uri, cr); err != nil {
			fmt.Fprintf(os.Stderr, "[e] %s: %s\n", uri, err)
			return
		}

		<-time.After(time.Duration(feed.SecondsTillUpdate() * 1e9))
	}
}

func chanHandler(feed *rss.Feed, newchannels []*rss.Channel) {
	fmt.Printf("%d new channel(s) in %s\n", len(newchannels), feed.Url)
}

func itemHandler(feed *rss.Feed, ch *rss.Channel, newitems []*rss.Item) {
	fmt.Printf("%d new item(s) in %s\n", len(newitems), feed.Url)
}

func charsetReader(charset string, r io.Reader) (io.Reader, error) {
	if charset == "ISO-8859-1" || charset == "iso-8859-1" {
		return r, nil
	}
	return nil, errors.New("Unsupported character set encoding: " + charset)
}