using System.Xml.Linq;

namespace AnimeAnnouncer.Torrents
{
    public record NyaaRssItem(
        String Title,
        String Published,
        String Category,
        String CategoryID,
        String Size,
        String Link,
        String Description,
        String PostID);

    /// <summary>
    /// Reads Nyaa RSS feeds and downloads the .torrent files they link to.
    /// </summary>
    public class NyaaRssReader
    {
        private readonly HttpClient httpClient;

        public NyaaRssReader(HttpClient? httpClient = null)
        {
            this.httpClient = httpClient ?? new HttpClient();
        }

        /// <summary>
        /// Converts a Nyaa search URL into its RSS equivalent, if it isn't one already.
        /// </summary>
        public static String ToRssUrl(String url)
        {
            return url.Contains("rss") ? url : url + "&page=rss";
        }

        public async Task<List<NyaaRssItem>> ReadAsync(String url)
        {
            var response = await httpClient.GetStringAsync(ToRssUrl(url));
            return Parse(response);
        }

        public static List<NyaaRssItem> Parse(String rssXml)
        {
            XDocument doc = XDocument.Parse(rssXml);
            XNamespace nyaaNS = doc.Root!.GetNamespaceOfPrefix("nyaa") ?? XNamespace.None;
            return (from item in doc.Descendants("channel").Elements("item")
                    select new NyaaRssItem(
                        Title: item.Element("title")?.Value ?? String.Empty,
                        Published: item.Element("pubDate")?.Value ?? String.Empty,
                        Category: item.Element(nyaaNS + "category")?.Value ?? String.Empty,
                        CategoryID: item.Element(nyaaNS + "categoryId")?.Value ?? String.Empty,
                        Size: item.Element(nyaaNS + "size")?.Value ?? String.Empty,
                        Link: item.Element("link")?.Value ?? String.Empty,
                        Description: item.Element("description")?.Value ?? String.Empty,
                        PostID: item.Element("guid")?.Value ?? String.Empty
                    )).ToList();
        }

        public Task<byte[]> DownloadTorrentAsync(NyaaRssItem item)
        {
            return httpClient.GetByteArrayAsync(item.Link);
        }
    }
}