using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Mime;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Rac.Common;
using Rac.Tools;

namespace Rac
{
    public class Extractor : BaseService
    {
        private static readonly HashSet<char> invalidChars = new HashSet<char>(Path.GetInvalidFileNameChars());

        private readonly string _dbFilePath;

        private DataAccess _db;
        private Uri _homeUrl;
        private HashSet<string> _hostInclude;
        private string[] _excludeUrlPrefixes;

        private Encoding _defaultEncoding;
        private string _webRoot;

        public Extractor(string dbFilePath)
        {
            _dbFilePath = Path.GetFullPath(dbFilePath);

            if (false == File.Exists(_dbFilePath))
            {
                LogFatal($"Can not find database file:{_dbFilePath}");
                return;
            }

            _db = new DataAccess(_dbFilePath);
            var conf = new ConfigAdapter(_db.GetConfigs());

            _defaultEncoding = null != conf.DefaultCharset ? Encoding.GetEncoding(conf.DefaultCharset) : Encoding.UTF8;

            _hostInclude = new HashSet<string>(conf.HostsInclude);
            _excludeUrlPrefixes = conf.UrlPrefixExclude;

            _homeUrl = new Uri(conf.HomeUrl);
            _webRoot = conf.ExtractWebRoot;
        }

        private readonly Dictionary<string, bool> _eitCache = new Dictionary<string, bool>();

        private bool EntryIsTextHtml(string url)
        {
            if (_eitCache.TryGetValue(url, out var r)) return r;
            var entry = _db.GetEntry(url);

            if (entry == null || entry.StatusCode == 0) return _eitCache[url] = false;

            var headers = HttpHeaderUtility.ParseStringLines(entry.Headers);
            string contentType = null;

            foreach (var header in headers)
            {
                if (header.Name == "content-type")
                {
                    var ct = new ContentType(header.Value);
                    contentType = ct.MediaType;
                }
            }

            return _eitCache[url] = contentType == "text/html";
        }

        private string UrlTranscode(Uri uri, string link = null, bool includedOnly = false, bool isFs = false, bool appendHtml = false)
        {
            if (true == link?.ToLower().StartsWith("mailto:")) return link;
            if (true == link?.ToLower().StartsWith("data:")) return link;

            //       http://host:port/path.ext?query#hash
            // -->>    http/host/port/path!qquery#hash.ext
            if (false == string.IsNullOrEmpty(link)) uri = new Uri(uri, link);

            var url = uri.ToString();
            if (includedOnly)
            {
                if (_excludeUrlPrefixes.Any(p => url.StartsWith(p))) return link;

                var hos = uri.Host;
                if (hos != _homeUrl.Host && false == _hostInclude.Contains(hos)) return link;
            }

            var sbt = new StringBuilder();
            sbt.Append($"{uri.Scheme}/{uri.Host}/{uri.Port}");

            var lPath = uri.LocalPath;

            var fPath = Path.GetDirectoryName(lPath)?.Replace("\\", "/").TrimStart('/');
            if (string.IsNullOrWhiteSpace(fPath) == false)
            {
                var parts = fPath.Split('/');
                foreach (var part in parts)
                {
                    sbt.Append("/");
                    AppendEscape(part);
                    sbt.Append("!");
                }
            }
            var fName = Path.GetFileNameWithoutExtension(lPath);
            var fExt = Path.GetExtension(lPath);

            sbt.Append($"/{fName}");
            if (string.IsNullOrWhiteSpace(uri.Query) == false) AppendEscape(uri.Query);
            if (string.IsNullOrWhiteSpace(fExt) == false) AppendEscape(fExt);
            if (sbt[sbt.Length - 1] == '/') sbt.Append("!index.html");
            if (isFs == false && string.IsNullOrWhiteSpace(uri.Fragment) == false) sbt.Append(uri.Fragment);

            var fin = sbt.ToString();

            if (EntryIsTextHtml(url) && fin.EndsWith(".html") == false && fin.EndsWith(".htm") == false)
            {
                sbt.Append(".html");
                return sbt.ToString();
            }

            return fin;

            void AppendEscape(string input)
            {
                foreach (var c in input)
                {
                    switch (c)
                    {
                        case '?': sbt.Append("!q"); break;
                        case '*': sbt.Append("!s"); break;
                        case '!': sbt.Append("!e"); break;
                        default:
                            if (invalidChars.Contains(c)) sbt.Append($"!{(int)c:X2}");
                            else sbt.Append(c);
                            break;
                    }
                }
            }
        }

        private string UrlTranscodeR(Uri uri, string link, bool includedOnly = false)
        {
            if (true == link?.ToLower().StartsWith("mailto:")) return link;
            if (true == link?.ToLower().StartsWith("data:")) return link;

            if (includedOnly)
            {
                var url = (false == string.IsNullOrEmpty(link) ? new Uri(uri, link) : uri).ToString();
                if (_excludeUrlPrefixes.Any(p => url.StartsWith(p))) return link;

                var hos = uri.Host;
                if (hos != _homeUrl.Host && false == _hostInclude.Contains(hos)) return link;
            }

            var tUrl = UrlTranscode(uri, link);

            if (string.IsNullOrWhiteSpace(_webRoot))
            {
                var bStr = "file://fake/" + UrlTranscode(uri);
                var aStr = "file://fake/" + tUrl;

                var bU = new Uri(bStr);
                var aU = new Uri(aStr);
                var r = bU.MakeRelativeUri(aU);

                return r.ToString();
            }

            return _webRoot + tUrl;
        }

        public void RunExtract()
        {
            var outputDir = Path.Combine(Path.GetDirectoryName(_dbFilePath), "RacExtract");
            var allUrl = _db.GetAllUrl();
            foreach (var url in allUrl)
            {
                var uri = new Uri(url);
                var entry = _db.GetEntry(url);
                if (entry == null || entry.StatusCode == 0) continue;

                var headers = HttpHeaderUtility.ParseStringLines(entry.Headers);
                string contentType = null;
                var contentEncoding = _defaultEncoding;

                foreach (var header in headers)
                {
                    if (header.Name == "content-type")
                    {
                        var ct = new ContentType(header.Value);
                        contentType = ct.MediaType;
                        if (null != ct.CharSet) contentEncoding = Encoding.GetEncoding(ct.CharSet);
                    }
                }

                var fsPath = Path.GetFullPath(Path.Combine(outputDir, UrlTranscode(uri, isFs: true)));
                if (File.Exists(fsPath))
                {
                    LogInfo($"SKIP EXIST: {fsPath}");
                    continue;
                }

                string location = null;
                foreach (var header in headers)
                {
                    if (header.Name == "location") location = UrlTranscodeR(uri, header.Value);
                }

                var output = entry.Content;

                if (contentType == "text/html")
                {
                    var replaced = LinkProcessor.ReplaceHtmlLinks(entry.Content, p => UrlTranscodeR(uri, p, true), ref contentEncoding);
                    if (location != null) replaced += $"<br>Location:<a href=\"{location}\">{location}</a> <meta http-equiv=\"refresh\" content=\"1; url={location}\">";
                    output = contentEncoding.GetBytes(replaced);
                }
                else if (contentType == "text/css")
                {
                    var css = contentEncoding.GetString(entry.Content);
                    var replaced = LinkProcessor.ReplaceCssLinks(css, p => UrlTranscodeR(uri, p, true));
                    output = contentEncoding.GetBytes(replaced);
                }

                LogInfo($"Output: {fsPath}");
                {
                    var fsDir = Path.GetDirectoryName(fsPath);
                    if (Directory.Exists(fsDir) == false) Directory.CreateDirectory(fsDir);
                    File.WriteAllBytes(fsPath, output);
                }
            }
        }

        public override void Start()
        {
            throw new NotImplementedException();
        }

        public override void Stop()
        {
            throw new NotImplementedException();
        }
    }
}