package service

import (
	"context"
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strings"
)

// rssFeed is the minimal RSS subset we need to decode.
type rssFeed struct {
	XMLName xml.Name `xml:"rss"`
	Channel struct {
		Items []rssItem `xml:"item"`
	} `xml:"channel"`
}

type rssItem struct {
	Title       string `xml:"title"`
	Link        string `xml:"link"`
	GUID        string `xml:"guid"`
	Description string `xml:"description"`
	Enclosure   struct {
		URL string `xml:"url,attr"`
	} `xml:"enclosure"`
}

func (s *SubscriptionService) fetch(ctx context.Context, feedURL string) (*rssFeed, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, feedURL, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("User-Agent", "MediaStationGo/0.1")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 400 {
		return nil, fmt.Errorf("rss %s: %d", feedURL, resp.StatusCode)
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	var f rssFeed
	if err := xml.Unmarshal(body, &f); err != nil {
		return nil, err
	}
	return &f, nil
}

func compileFilter(pat string) *regexp.Regexp {
	pat = strings.TrimSpace(pat)
	if pat == "" {
		return nil
	}
	if r, err := regexp.Compile("(?i)" + pat); err == nil {
		return r
	}
	return nil
}

func splitNonEmpty(s string) []string {
	if s == "" {
		return nil
	}
	out := make([]string, 0)
	for _, p := range strings.Split(s, "\n") {
		p = strings.TrimSpace(p)
		if p != "" {
			out = append(out, p)
		}
	}
	return out
}