using FeedCenter.Xml;
using Serilog;
using System;
using System.Xml;

namespace FeedCenter.FeedParsers;

internal class RssParser : FeedParserBase
{
    public RssParser(Feed feed) : base(feed) { }

    public override FeedReadResult ParseFeed(string feedText)
    {
        try
        {
            // Create the XML document
            var document = new XmlDocument { XmlResolver = null };

            // Load the XML document from the text
            document.LoadXml(feedText);

            // Create the namespace manager
            var namespaceManager = document.GetAllNamespaces();

            // Get the root node
            XmlNode rootNode = document.DocumentElement;

            // If we didn't find a root node then bail
            if (rootNode == null)
                return FeedReadResult.UnknownError;

            // Get the channel node
            var channelNode = rootNode.SelectSingleNode("default:channel", namespaceManager) ??
                              rootNode.SelectSingleNode("channel", namespaceManager);

            if (channelNode == null)
                return FeedReadResult.InvalidXml;

            // Initialize the sequence number for items
            var sequence = 0;

            // Loop over all nodes in the channel node
            foreach (XmlNode node in channelNode.ChildNodes)
            {
                // Handle each node that we find
                switch (node.Name)
                {
                    case "title":
                        Feed.Title = System.Net.WebUtility.HtmlDecode(node.InnerText).Trim();
                        break;

                    case "link":
                        Feed.Link = node.InnerText.Trim();
                        break;

                    case "description":
                        Feed.Description = node.InnerText;
                        break;

                    case "item":
                        HandleFeedItem(node, ref sequence);
                        break;
                }
            }

            return FeedReadResult.Success;
        }
        catch (XmlException xmlException)
        {
            Log.Logger.Error(xmlException, "Exception: {0}", feedText);

            return FeedReadResult.InvalidXml;
        }
    }

    protected override FeedItem ParseFeedItem(XmlNode node)
    {
        // Create a new feed item
        var feedItem = FeedItem.Create();

        // Loop over all nodes in the feed node
        foreach (XmlNode childNode in node.ChildNodes)
        {
            // Handle each node that we find
            switch (childNode.Name.ToLower())
            {
                case "title":
                    feedItem.Title = System.Net.WebUtility.HtmlDecode(childNode.InnerText).Trim();
                    break;

                case "link":
                    feedItem.Link = childNode.InnerText.Trim();
                    break;

                case "guid":
                    feedItem.Guid = childNode.InnerText.Trim();

                    var permaLink = true;

                    if (childNode.Attributes != null)
                    {
                        var permaLinkNode = childNode.Attributes.GetNamedItem("isPermaLink");
                        permaLink = permaLinkNode == null || permaLinkNode.Value == "true";
                    }

                    if (permaLink && Uri.IsWellFormedUriString(feedItem.Guid, UriKind.Absolute))
                        feedItem.Link = feedItem.Guid;

                    break;

                case "description":
                    feedItem.Description = System.Net.WebUtility.HtmlDecode(childNode.InnerText);
                    break;
            }
        }

        if (string.IsNullOrWhiteSpace(feedItem.Guid))
            feedItem.Guid = feedItem.Link;

        return feedItem;
    }
}