package spc

import (
	"encoding/xml"
	"fmt"
	"strings"
	"time"
)

// RSSFeed is a minimal view of the optional SPC RSS feed.
type RSSFeed struct {
	Title         string
	Link          string
	Description   string
	LastBuildDate *time.Time
	Items         []RSSItem
}

// RSSItem is a minimal view of one optional SPC RSS item.
type RSSItem struct {
	Title       string
	Link        string
	Description string
	PubDate     string
	GUID        string
}

// ParseRSSFeed decodes supplemental SPC RSS metadata.
func ParseRSSFeed(raw string) (RSSFeed, error) {
	var doc struct {
		Channel struct {
			Title         string `xml:"title"`
			Link          string `xml:"link"`
			Description   string `xml:"description"`
			LastBuildDate string `xml:"lastBuildDate"`
			Items         []struct {
				Title       string `xml:"title"`
				Link        string `xml:"link"`
				Description string `xml:"description"`
				PubDate     string `xml:"pubDate"`
				GUID        string `xml:"guid"`
			} `xml:"item"`
		} `xml:"channel"`
	}
	if err := xml.Unmarshal([]byte(raw), &doc); err != nil {
		return RSSFeed{}, fmt.Errorf("decode rss: %w", err)
	}

	feed := RSSFeed{
		Title:         strings.TrimSpace(doc.Channel.Title),
		Link:          strings.TrimSpace(doc.Channel.Link),
		Description:   strings.TrimSpace(doc.Channel.Description),
		LastBuildDate: parseRSSDate(doc.Channel.LastBuildDate),
		Items:         make([]RSSItem, 0, len(doc.Channel.Items)),
	}
	for _, item := range doc.Channel.Items {
		feed.Items = append(feed.Items, RSSItem{
			Title:       strings.TrimSpace(item.Title),
			Link:        strings.TrimSpace(item.Link),
			Description: strings.TrimSpace(item.Description),
			PubDate:     strings.TrimSpace(item.PubDate),
			GUID:        strings.TrimSpace(item.GUID),
		})
	}
	return feed, nil
}

func parseRSSDate(value string) *time.Time {
	value = strings.TrimSpace(value)
	if value == "" {
		return nil
	}
	for _, layout := range []string{time.RFC1123Z, time.RFC1123} {
		t, err := time.Parse(layout, value)
		if err == nil {
			tt := t.UTC()
			return &tt
		}
	}
	return nil
}