using HtmlAgilityPack;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Web;
using PhilExampleCrawler.Common.Models;

namespace PhilExampleCrawler.Core
{
    internal class BaseCrawler_HAP
    {
        #region HTML Tags & Selectors
        const string SELECTOR_INSERTION = "#srchrslt-adtable > .ad-listitem > article"; //reflects found insertions on the search result page

        internal const string SELECTOR_TOPAD = ".aditem-main .aditem-main--top .aditem-main--top--right i.icon-feature-topad";
        internal const string SELECTOR_HIGHLIGHT = ".aditem-main .aditem-main--top .aditem-main--top--right i.icon-feature-highlight";
        internal const string SELECTOR_BOTTOM_TAG = ".aditem-main .aditem-main--bottom p .simpletag.tag-small";

        internal const string SELECTOR_LOCATION = ".aditem-main .aditem-main--top .aditem-main--top--left";

        internal const string ATTR_DATA_HREF = "data-href";

        internal const string BOTTOM_TAG_GESUCH = "GESUCH";
        #endregion

        readonly HtmlWeb _web = new();
        List<string> _cachedHrefs = new(); 
        bool _firstCrawl = true;
        bool _crawling = false;

        internal event EventHandler<Insertion> OnNewInsertionFound;


        //TODO: crawl categories
        //TODO: crawl locations

        internal void StartCrawling(CrawlSearchParams searchParams, int intervalSec = 10)
        {

        }

        internal void Crawl(CrawlSearchParams searchParams, int timeout_ms)
        {
            var searchUrl = AsUrl(searchParams);
            var searchResultDoc = _web.Load(searchUrl, timeout_ms);

            if (searchResultDoc == null)
                return;

            var insNodes = GetInsertionNodes(searchResultDoc);
            CompareToFoundNodes(insNodes);
        }

        //TODO: Implement CancellationToken
        internal void StopCrawling()
        {
            _crawling = false;
            _firstCrawl = true;
            _cachedHrefs = new List<string>();
        }




        private void CompareToFoundNodes(IList<HtmlNode> insertionNodes)
        {
            List<(string href, HtmlNode srcNode)> insHrefNodes = GetInsertionHrefs(insertionNodes);

            if (_firstCrawl)
            {
                _cachedHrefs.AddRange(insHrefNodes.Select(x => x.href));
                _firstCrawl = false;
            }
            else
            {
                foreach ((string href, HtmlNode srcNode) in insHrefNodes)
                {
                    if (!_cachedHrefs.Any(x => x == href))
                    {
                        _cachedHrefs.Add(href);
                        OnNewInsertionFound?.Invoke(this, GetInsertion(srcNode));
                    }
                }
            }
        }


        #region Node Methods
        private static IList<HtmlNode> GetInsertionNodes(HtmlDocument doc)
        {
            IList<HtmlNode> insNodes = doc.QuerySelectorAll(SELECTOR_INSERTION);
            return insNodes.Where(n => n != null
                                    && n.HasAttributes
                                    && n.Attributes.Any(a => a.Name == ATTR_DATA_HREF)).ToList();
        }

        private static List<(string href, HtmlNode srcNode)> GetInsertionHrefs(IList<HtmlNode> insertionNodes)
             => insertionNodes.Select(x => (x.Attributes["data-href"].Value, x)).ToList();

        private static Insertion GetInsertion(HtmlNode insertionNode)
        {
            //var i = new Insertion
            //{
            //    Href = insertionNode.Attributes["data-href"].Value,
            //    IsTopAd = insertionNode.QuerySelector(SELECTOR_TOPAD) != null,
            //    IsHighlight = insertionNode.QuerySelector(SELECTOR_HIGHLIGHT) != null,
            //};

            //var plzLoc = GetInsertionLocation(insertionNode);
            //Console.WriteLine("Plz: " + plzLoc.plz + " --- " + "Loc: " + plzLoc.loc);


            //var reqNode = insertionNode.QuerySelector(SELECTOR_BOTTOM_TAG);
            //if (reqNode != null)
            //    i.IsRequest = reqNode.InnerHtml?.ToUpperInvariant() == BOTTOM_TAG_GESUCH;

            //return i;
            return null;
        }

        private static (int plz, string loc) GetInsertionLocation(HtmlNode insertionNode)
        {
            var locNode = insertionNode.QuerySelector(SELECTOR_LOCATION);
            string inner = locNode.InnerHtml;

            if (locNode != null && !string.IsNullOrEmpty(inner))
            {
                if (inner.IndexOf(">") > -1)
                    inner = inner.Substring(inner.LastIndexOf(">") + 1).Trim();

                if(inner.Length >= 5 && int.TryParse(inner.Substring(0, 5), out int plz))
                {
                    return (plz, inner.Substring(5).Trim());
                }
            }
            return (-1, null);
        } 

        const string nums = "0123456789";

        private static List<Insertion> GetInsertions(IList<HtmlNode> insertionNodes)
             => insertionNodes.Select(x => GetInsertion(x)).ToList();
        #endregion


        private string AsUrl(CrawlSearchParams searchParams)
        {
            return string.Format(Config.EXAMPLE_SEARCH_URL, HttpUtility.UrlEncode(searchParams.KeyWords),
                                                         HttpUtility.UrlEncode(searchParams.LocationStr),
                                                         searchParams.CategoryID,
                                                         searchParams.Radius);
        }
    }
}