using Rac.Common;
using Rac.Entities;
using Rac.Models;
using Rac.Tools;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace Rac
{
    //TODO: CHECK AFFECT OF `Error loading type Typespec 0x1b000044 from  due to Could not resolve typespec token 1b000044'

    public class Crawler : BaseService
    {
        private readonly DataAccess _db;
        private Thread _runner;

        public bool IsRunning { get; private set; }

        public Crawler(string dbFilePath)
        {
            _db = new DataAccess(dbFilePath);
        }

        public override void Start()
        {
            LogInfo("Starting...");
            IsRunning = true;
            _runner = new Thread(RunInternal) { IsBackground = true };
            _runner.Start();
            LogInfo("Started.");
        }

        public override void Stop()
        {
            IsRunning = false;
            _runner.Join();
            LogInfo("Stopped.");
        }

        private void RunInternal()
        {
            LogDebug("Loading configs...");
            var conf = new ConfigAdapter(_db.GetConfigs());
            if (string.IsNullOrEmpty(conf.HomeUrl))
            {
                LogFatal($"The config <{nameof(conf.HomeUrl)}> is required! HALT");
                return;
            }

            var excludeUrlPrefix = conf.UrlPrefixExclude;

            var hostsInclude = new HashSet<string>(conf.HostsInclude);
            var homeUri = new Uri(conf.HomeUrl);
            var homeHost = homeUri.Host.ToLower();

            string[] ProcessLinkFilters(Uri pageUri, params string[] links)
            {
                var linkUris = links.Select(p =>
                {
                    try
                    {
                        var uri = new Uri(pageUri, p);
                        if (string.IsNullOrEmpty(uri.Fragment)) return uri;

                        //remove hash
                        var uos = uri.ToString();
                        uos = uos.Substring(0, uos.IndexOf("#", StringComparison.Ordinal));
                        return new Uri(uos);
                    }
                    catch (Exception e)
                    {
                        LogWarning($"{e.Message} {p}");
                        return null;
                    }
                }).Where(p => null != p).Distinct().ToArray();

                var lstExPfx = new List<Uri>();
                var lstInHome = new List<Uri>();
                var lstInHosts = new List<Uri>();
                var lstExNon = new List<Uri>();

                foreach (var linkUri in linkUris)
                {
                    if (excludeUrlPrefix.Any(p => linkUri.ToString().StartsWith(p)))
                    {
                        lstExPfx.Add(linkUri);
                        continue;
                    }

                    if (linkUri.Host == homeHost)
                    {
                        lstInHome.Add(linkUri);
                        continue;
                    }

                    if (hostsInclude.Contains(linkUri.Host))
                    {
                        lstInHosts.Add(linkUri);
                        continue;
                    }

                    lstExNon.Add(linkUri);
                }

                var pageUrl = pageUri.ToString();
                void AddLinks(List<Uri> items, bool included, string remark)
                {
                    if (items.Any()) _db.BulkAddResourceLink(pageUrl, included, remark, items.Select(p => p.ToString()).ToArray());
                }

                AddLinks(lstExPfx, false, "Exclude by url prefix");
                AddLinks(lstExNon, false, "Exclude by non matched rulers");

                AddLinks(lstInHome, true, "Include by home host");
                AddLinks(lstInHosts, true, "Include by [HostsInclude]");

                return lstInHome.Union(lstInHosts).Select(p => p.ToString()).ToArray();
            }

            _db.CreateArchiveEntryIfNotExist(conf.HomeUrl);

            while (IsRunning)
            {
                var urls = _db.GetNonDumpedUrls(conf.Parallel);
                LogInfo($"Gets {urls.Length} url from db.");
                if (urls.Length == 0) break;

                var hssExtractedLinks = new HashSet<string>();

                ArchiveEntry PageProc(string url)
                {
                    ArchiveEntry entry;
                    Response resp;

                    var uri = new Uri(url);

                    LogTrace($"GET {uri}");

                    var referer = _db.GetReferer(url);
                    LogTrace($" -> Referer: {referer}");

                    try
                    {
                        resp = Requester.GetHttp(url, referer);

                        entry = new ArchiveEntry
                        {
                            Url = url,
                            StatusCode = (int)resp.StatusCode,
                            StatusDescription = resp.StatusDescription,
                            Content = resp.Body,
                        };
                    }
                    catch (Exception e)
                    {
                        LogTrace($"GET {url} -- {e.Message}");

                        entry = new ArchiveEntry
                        {
                            Url = url,
                            StatusCode = 544,
                            StatusDescription = "ArchiverError",
                            Headers = "content-type: text/plain; charset=utf-8",
                            Content = Encoding.UTF8.GetBytes(e.ToString())
                        };
                        return entry;
                    }

                    LogTrace($"GET {url} -- {entry.StatusCode}|{resp.ContentType}|{entry.Content.Length}");

                    var listHeaders = new List<HttpHeader> { new HttpHeader("content-type", resp.ContentType) };
                    listHeaders.AddRange(resp.GetServerTimeHeaders());

                    if (resp.GetRedirect(out var redirectUrl))
                    {
                        hssExtractedLinks.AddRange(ProcessLinkFilters(uri, redirectUrl));
                        listHeaders.Add(new HttpHeader("location", redirectUrl));
                    }
                    else
                    {
                        var linksOnPage = new HashSet<string>();

                        if (resp.GetHtmlDocument(out var doc)) linksOnPage.AddRange(LinkProcessor.ExtractLinks(doc).Distinct());
                        else if (resp.GetCss(out var css)) linksOnPage.AddRange(LinkProcessor.FromCss(css).Distinct());

                        linksOnPage.Remove("//");

                        hssExtractedLinks.AddRange(ProcessLinkFilters(uri, linksOnPage.ToArray()));
                    }

                    entry.Headers = listHeaders.ToStringLines();
                    return entry;
                }

                var results = urls
                    .AsParallel().WithDegreeOfParallelism(conf.Parallel)
                    .Select(PageProc)
                    .ToArray();

                LogInfo($"Saving extracted {hssExtractedLinks.Count} new link...");
                var n = _db.BulkAddNewArchiveEntry(hssExtractedLinks);
                LogInfo($"Saved new {n} link...");

                LogInfo($"Updating {results.Length} entry...");
                var u = _db.BulkUpdateArchiveEntry(results);
                LogInfo($"Updated  {u} entry...");
            }

            IsRunning = false;
            LogInfo("Finished!");
        }
    }
}