using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Xml;
using System.Xml.XPath;
using Umbraco.Core;
using Umbraco.Core.Cache;
using Umbraco.Core.Configuration;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Core.Xml;
using Umbraco.Web.PublishedCache;
using Umbraco.Web.Routing;

namespace Umbraco.Tests.LegacyXmlPublishedCache
{
    internal class PublishedContentCache : PublishedCacheBase, IPublishedContentCache2
    {
        private readonly IAppCache _appCache;
        private readonly IGlobalSettings _globalSettings;
        private readonly RoutesCache _routesCache;
        private readonly IDomainCache _domainCache;
        private readonly PublishedContentTypeCache _contentTypeCache;

        // initialize a PublishedContentCache instance with
        // an XmlStore containing the master xml
        // an IAppCache that should be at request-level
        // a RoutesCache - need to cleanup that one
        // a preview token string (or null if not previewing)
        public PublishedContentCache(
            XmlStore xmlStore, // an XmlStore containing the master xml
            IDomainCache domainCache, // an IDomainCache implementation
            IAppCache appCache, // an IAppCache that should be at request-level
            IGlobalSettings globalSettings,
            PublishedContentTypeCache contentTypeCache, // a PublishedContentType cache
            RoutesCache routesCache, // a RoutesCache
            string previewToken) // a preview token string (or null if not previewing)
            : base(previewToken.IsNullOrWhiteSpace() == false)
        {
            _appCache = appCache;
            _globalSettings = globalSettings;
            _routesCache = routesCache; // may be null for unit-testing
            _contentTypeCache = contentTypeCache;
            _domainCache = domainCache;

            _xmlStore = xmlStore;
            _xml = _xmlStore.Xml; // capture - because the cache has to remain consistent

            if (previewToken.IsNullOrWhiteSpace() == false)
                _previewContent = new PreviewContent(_xmlStore, previewToken);
        }

        #region Unit Tests

        // for INTERNAL, UNIT TESTS use ONLY
        internal RoutesCache RoutesCache => _routesCache;

        // for INTERNAL, UNIT TESTS use ONLY
        internal XmlStore XmlStore => _xmlStore;

        #endregion

        #region Routes

        public virtual IPublishedContent GetByRoute(bool preview, string route, bool? hideTopLevelNode = null, string culture = null)
        {
            if (route == null) throw new ArgumentNullException(nameof(route));

            // try to get from cache if not previewing
            var contentId = preview || _routesCache == null ? 0 : _routesCache.GetNodeId(route);

            // if found id in cache then get corresponding content
            // and clear cache if not found - for whatever reason
            IPublishedContent content = null;
            if (contentId > 0)
            {
                content = GetById(preview, contentId);
                if (content == null)
                    _routesCache?.ClearNode(contentId);
            }

            // still have nothing? actually determine the id
            hideTopLevelNode = hideTopLevelNode ?? _globalSettings.HideTopLevelNodeFromPath; // default = settings
            content = content ?? DetermineIdByRoute(preview, route, hideTopLevelNode.Value);

            // cache if we have a content and not previewing
            if (content != null && preview == false && _routesCache != null)
                AddToCacheIfDeepestRoute(content, route);

            return content;
        }

        private void AddToCacheIfDeepestRoute(IPublishedContent content, string route)
        {
            var domainRootNodeId = route.StartsWith("/") ? -1 : int.Parse(route.Substring(0, route.IndexOf('/')));

            // so we have a route that maps to a content... say "1234/path/to/content" - however, there could be a
            // domain set on "to" and route "4567/content" would also map to the same content - and due to how
            // urls computing work (by walking the tree up to the first domain we find) it is that second route
            // that would be returned - the "deepest" route - and that is the route we want to cache, *not* the
            // longer one - so make sure we don't cache the wrong route

            var deepest = DomainUtilities.ExistsDomainInPath(_domainCache.GetAll(false), content.Path, domainRootNodeId) == false;

            if (deepest)
                _routesCache.Store(content.Id, route, true); // trusted route
        }

        public IPublishedContent GetByRoute(string route, bool? hideTopLevelNode = null, string culture = null)
        {
            return GetByRoute(PreviewDefault, route, hideTopLevelNode);
        }

        public virtual string GetRouteById(bool preview, int contentId, string culture = null)
        {
            // try to get from cache if not previewing
            var route = preview || _routesCache == null ? null : _routesCache.GetRoute(contentId);

            // if found in cache then return
            if (route != null)
                return route;

            // else actually determine the route
            route = DetermineRouteById(preview, contentId);

            // node not found
            if (route == null)
                return null;

            // cache the route BUT do NOT trust it as it can be a colliding route
            // meaning if we GetRouteById again, we'll get it from cache, but it
            // won't be used for inbound routing
            if (preview == false)
                _routesCache.Store(contentId, route, false);

            return route;
        }

        public string GetRouteById(int contentId, string culture = null)
        {
            return GetRouteById(PreviewDefault, contentId, culture);
        }

        IPublishedContent DetermineIdByRoute(bool preview, string route, bool hideTopLevelNode)
        {
            //the route always needs to be lower case because we only store the urlName attribute in lower case
            route = route?.ToLowerInvariant() ?? throw new ArgumentNullException(nameof(route));

            var pos = route.IndexOf('/');
            var path = pos == 0 ? route : route.Substring(pos);
            var startNodeId = pos == 0 ? 0 : int.Parse(route.Substring(0, pos));

            //check if we can find the node in our xml cache
            var id = NavigateRoute(preview, startNodeId, path, hideTopLevelNode);
            return id > 0 ? GetById(preview, id) : null;
        }

        private static XmlElement GetXmlElementChildWithLowestSortOrder(XmlNode element)
        {
            XmlElement elt = null;
            var min = int.MaxValue;
            foreach (var n in element.ChildNodes)
            {
                var e = n as XmlElement;
                if (e == null) continue;

                var sortOrder = int.Parse(e.GetAttribute("sortOrder"));
                if (sortOrder >= min) continue;

                min = sortOrder;
                elt = e;
            }
            return elt;
        }

        private int NavigateRoute(bool preview, int startNodeId, string path, bool hideTopLevelNode)
        {
            var xml = GetXml(preview);
            XmlElement elt;

            // empty path
            if (path == string.Empty || path == "/")
            {
                if (startNodeId > 0)
                {
                    elt = xml.GetElementById(startNodeId.ToString(CultureInfo.InvariantCulture));
                    return elt == null ? -1 : startNodeId;
                }

                elt = GetXmlElementChildWithLowestSortOrder(xml.DocumentElement);
                return elt == null ? -1 : int.Parse(elt.GetAttribute("id"));
            }

            // non-empty path
            elt = startNodeId <= 0
                ? xml.DocumentElement
                : xml.GetElementById(startNodeId.ToString(CultureInfo.InvariantCulture));
            if (elt == null) return -1;

            var urlParts = path.Split(SlashChar, StringSplitOptions.RemoveEmptyEntries);

            if (hideTopLevelNode && startNodeId <= 0)
            {
                //Don't use OfType<T> or Cast<T>, this is critical code, all ChildNodes are XmlElement so explicitly cast
                // https://gist.github.com/Shazwazza/04e2e5642a316f4a87e52dada2901198
                foreach (var n in elt.ChildNodes)
                {
                    var e = n as XmlElement;
                    if (e == null) continue;

                    var id = NavigateElementRoute(e, urlParts);
                    if (id > 0) return id;
                }

                if (urlParts.Length > 1)
                    return -1;
            }

            return NavigateElementRoute(elt, urlParts);
        }

        private static int NavigateElementRoute(XmlElement elt, string[] urlParts)
        {
            var found = true;
            var i = 0;
            while (found && i < urlParts.Length)
            {
                found = false;
                //Don't use OfType<T> or Cast<T>, this is critical code, all ChildNodes are XmlElement so explicitly cast
                // https://gist.github.com/Shazwazza/04e2e5642a316f4a87e52dada2901198
                var sortOrder = -1;
                foreach (var o in elt.ChildNodes)
                {
                    var child = o as XmlElement;
                    if (child == null) continue;

                    var noNode = child.GetAttributeNode("isDoc") == null;
                    if (noNode) continue;
                    if (child.GetAttribute("urlName") != urlParts[i]) continue;

                    found = true;

                    var so = int.Parse(child.GetAttribute("sortOrder"));
                    if (sortOrder >= 0 && so >= sortOrder) continue;

                    sortOrder = so;
                    elt = child;
                }
                i++;
            }
            return found ? int.Parse(elt.GetAttribute("id")) : -1;
        }

        string DetermineRouteById(bool preview, int contentId)
        {
            var node = GetById(preview, contentId);
            if (node == null) return null;

            // walk up from that node until we hit a node with a domain,
            // or we reach the content root, collecting urls in the way
            var pathParts = new List<string>();
            var n = node;
            var hasDomains = _domainCache.HasAssigned(n.Id);
            while (hasDomains == false && n != null) // n is null at root
            {
                // get the url
                var urlName = n.UrlSegment();
                pathParts.Add(urlName);

                // move to parent node
                n = n.Parent;
                hasDomains = n != null && _domainCache.HasAssigned(n.Id);
            }

            // no domain, respect HideTopLevelNodeFromPath for legacy purposes
            if (hasDomains == false && _globalSettings.HideTopLevelNodeFromPath)
            {
                if (node.Parent == null)
                {
                    var rootNode = GetByRoute(preview, "/", true);
                    if (rootNode == null)
                        throw new Exception("Failed to get node at /.");
                    if (rootNode.Id == node.Id) // remove only if we're the default node
                        pathParts.RemoveAt(pathParts.Count - 1);
                }
                else
                {
                    pathParts.RemoveAt(pathParts.Count - 1);
                }
            }

            // assemble the route
            pathParts.Reverse();
            var path = "/" + string.Join("/", pathParts); // will be "/" or "/foo" or "/foo/bar" etc
            var route = (n?.Id.ToString(CultureInfo.InvariantCulture) ?? "") + path;

            return route;
        }

        #endregion

        #region XPath Strings

        static class XPathStrings
        {
            public const string Root = "/root";
            public const string RootDocuments = "/root/* [@isDoc]";
        }

        #endregion

        #region Converters

        private IPublishedContent ConvertToDocument(XmlNode xmlNode, bool isPreviewing)
        {
            return xmlNode == null ? null : XmlPublishedContent.Get(xmlNode, isPreviewing, _appCache, _contentTypeCache);
        }

        private IEnumerable<IPublishedContent> ConvertToDocuments(XmlNodeList xmlNodes, bool isPreviewing)
        {
            return xmlNodes.Cast<XmlNode>()
                .Select(xmlNode => XmlPublishedContent.Get(xmlNode, isPreviewing, _appCache, _contentTypeCache));
        }

        #endregion

        #region Getters

        public override IPublishedContent GetById(bool preview, int nodeId)
        {
            return ConvertToDocument(GetXml(preview).GetElementById(nodeId.ToString(CultureInfo.InvariantCulture)), preview);
        }

        public override IPublishedContent GetById(bool preview, Guid nodeId)
        {
            // implement this, but in a more efficient way
            //const string xpath = "//* [@isDoc and @key=$guid]";
            //return GetSingleByXPath(preview, xpath, new[] { new XPathVariable("guid", nodeId.ToString()) });

            var keyMatch = nodeId.ToString();

            var nav = GetXml(preview).CreateNavigator();
            if (nav.MoveToFirstChild() == false) return null; // from / to /root
            if (nav.MoveToFirstChild() == false) return null; // from /root to /root/*

            while (true)
            {
                var isDoc = false;
                string key = null;

                if (nav.HasAttributes)
                {
                    nav.MoveToFirstAttribute();
                    do
                    {
                        if (nav.Name == "isDoc") isDoc = true;
                        if (nav.Name == "key") key = nav.Value;
                        if (isDoc && key != null) break;
                    } while (nav.MoveToNextAttribute());
                    nav.MoveToParent();
                }

                if (isDoc == false || key != keyMatch)
                {
                    if (isDoc && nav.MoveToFirstChild())
                        continue;
                    while (nav.MoveToNext(XPathNodeType.Element) == false)
                        if (nav.MoveToParent() == false || nav.NodeType == XPathNodeType.Root) return null;
                    continue;
                }

                var elt = nav.UnderlyingObject as XmlNode;
                return ConvertToDocument(elt, preview);
            }
        }

        public override IPublishedContent GetById(bool preview, Udi nodeId)
            => throw new NotSupportedException();

        public override bool HasById(bool preview, int contentId)
        {
            return GetXml(preview).CreateNavigator().MoveToId(contentId.ToString(CultureInfo.InvariantCulture));
        }

        public override IEnumerable<IPublishedContent> GetAtRoot(bool preview, string culture = null)
        {
            return ConvertToDocuments(GetXml(preview).SelectNodes(XPathStrings.RootDocuments), preview);
        }

        public override IPublishedContent GetSingleByXPath(bool preview, string xpath, XPathVariable[] vars)
        {
            if (xpath == null) throw new ArgumentNullException(nameof(xpath));
            if (string.IsNullOrWhiteSpace(xpath)) return null;

            var xml = GetXml(preview);
            var node = vars == null
                ? xml.SelectSingleNode(xpath)
                : xml.SelectSingleNode(xpath, vars);
            return ConvertToDocument(node, preview);
        }

        public override IPublishedContent GetSingleByXPath(bool preview, XPathExpression xpath, XPathVariable[] vars)
        {
            if (xpath == null) throw new ArgumentNullException(nameof(xpath));

            var xml = GetXml(preview);
            var node = vars == null
                ? xml.SelectSingleNode(xpath)
                : xml.SelectSingleNode(xpath, vars);
            return ConvertToDocument(node, preview);
        }

        public override IEnumerable<IPublishedContent> GetByXPath(bool preview, string xpath, XPathVariable[] vars)
        {
            if (xpath == null) throw new ArgumentNullException(nameof(xpath));
            if (string.IsNullOrWhiteSpace(xpath)) return Enumerable.Empty<IPublishedContent>();

            var xml = GetXml(preview);
            var nodes = vars == null
                ? xml.SelectNodes(xpath)
                : xml.SelectNodes(xpath, vars);
            return ConvertToDocuments(nodes, preview);
        }

        public override IEnumerable<IPublishedContent> GetByXPath(bool preview, XPathExpression xpath, XPathVariable[] vars)
        {
            if (xpath == null) throw new ArgumentNullException(nameof(xpath));

            var xml = GetXml(preview);
            var nodes = vars == null
                ? xml.SelectNodes(xpath)
                : xml.SelectNodes(xpath, vars);
            return ConvertToDocuments(nodes, preview);
        }

        public override bool HasContent(bool preview)
        {
            var xml = GetXml(preview);
            var node = xml?.SelectSingleNode(XPathStrings.RootDocuments);
            return node != null;
        }

        public override XPathNavigator CreateNavigator(bool preview)
        {
            var xml = GetXml(preview);
            return xml.CreateNavigator();
        }

        public override XPathNavigator CreateNodeNavigator(int id, bool preview)
        {
            // hackish - backward compatibility ;-(

            XPathNavigator navigator = null;

            if (preview)
            {
                var node = _xmlStore.GetPreviewXmlNode(id);
                if (node != null)
                {
                    navigator = node.CreateNavigator();
                }
            }
            else
            {
                var node = GetXml(false).GetElementById(id.ToInvariantString());
                if (node != null)
                {
                    var doc = new XmlDocument();
                    var clone = doc.ImportNode(node, false);
                    var props = node.SelectNodes("./* [not(@id)]");
                    if (props == null) throw new Exception("oops");
                    foreach (var n in props.Cast<XmlNode>())
                        clone.AppendChild(doc.ImportNode(n, true));
                    navigator = node.CreateNavigator();
                }
            }

            return navigator;
        }

        #endregion

        #region Legacy Xml

        private readonly XmlStore _xmlStore;
        private XmlDocument _xml;
        private readonly PreviewContent _previewContent;

        internal XmlDocument GetXml(bool preview)
        {
            // not trying to be thread-safe here, that's not the point

            if (preview == false)
            {
                // if there's a current enlisted reader/writer, use its xml
                var tempXml = _xmlStore.TempXml;
                if (tempXml != null) return tempXml;
                return _xml;
            }

            // Xml cache does not support retrieving preview content when not previewing
            if (_previewContent == null)
                throw new InvalidOperationException("Cannot retrieve preview content when not previewing.");

            // PreviewContent tries to load the Xml once and if it fails,
            // it invalidates itself and always return null for XmlContent.
            var previewXml = _previewContent.XmlContent;
            return previewXml ?? _xml;
        }

        internal void Resync(XmlDocument xml)
        {
            _xml = xml; // re-capture

            // note: we're not resyncing "preview" because that would mean re-building the whole
            // preview set which is costly, so basically when previewing, there will be no resync.

            // clear recursive properties cached by XmlPublishedContent.GetProperty
            // assume that nothing else is going to cache IPublishedProperty items (else would need to do ByKeySearch)
            // NOTE also clears all the media cache properties, which is OK (see media cache)
            _appCache.ClearOfType<IPublishedProperty>();
            //_appCache.ClearCacheByKeySearch("XmlPublishedCache.PublishedContentCache:RecursiveProperty-");
        }

        #endregion

        #region XPathQuery

        static readonly char[] SlashChar = { '/' };

        #endregion

        #region Content types

        public override IPublishedContentType GetContentType(int id) => _contentTypeCache.Get(PublishedItemType.Content, id);

        public override IPublishedContentType GetContentType(string alias) => _contentTypeCache.Get(PublishedItemType.Content, alias);

        public override IPublishedContentType GetContentType(Guid key) => _contentTypeCache.Get(PublishedItemType.Content, key);

        #endregion
    }
}