// Feedget scrapes RSS feeds (and other sources)
// and spits the latest headline from each onto a static web page.
package main

import (
	"context"
	"fmt"
	"log"
	"sort"
	"sync"
	"time"

	"github.com/mmcdole/gofeed"
)

func main() {
	var sources = []*FeedSource{ // TODO: interface Source
		NewFeed("https://tilde.team/~dozens/dreams/rss.xml"),
		NewFeed("https://tilde.town/~magical/xkcd.xml"), // "https://xkcd.com/atom.xml",
	}

	var wg sync.WaitGroup
	wg.Add(len(sources))
	for i := range sources {
		src := sources[i]
		go func() {
			src.update()
			wg.Done()
		}()
	}
	wg.Wait()

	for _, src := range sources {
		fmt.Println(src.Title, src.Error)
	}
}

type Source interface {
	Title() string
	Link() string
	Error() error
	Update(context.Context)
}

// want to keep track of:
// - whether the most recent update suceeded
// - when the last successful update was
// - how many of the last N updates succeeded
// - status codes for the last N updates
// - response time for the last N updates
// - how frequently items are posted

type Cache struct {
}

type FeedSource struct {
	Items     []*gofeed.Item
	Title     string
	URL       string
	LastFetch time.Time
	Error     error

	mu sync.Mutex
}

func NewFeed(url string) *FeedSource {
	return &FeedSource{
		URL: url,
	}
}

func (src *FeedSource) update() {
	src.mu.Lock()
	defer src.mu.Unlock()
	fp := gofeed.NewParser()
	feed, err := fp.ParseURL(src.URL)
	if err != nil {
		err := fmt.Errorf("error parsing %q: %v", src.URL, err)
		log.Println(err)
		src.Error = err
		return // return err?
	}
	items := feed.Items
	sort.Slice(items, func(i, j int) bool {
		return items[i].Updated >= items[j].Updated
	})
	src.Title = feed.Title
	src.Items = items
	src.LastFetch = time.Now()
}