///////////////////////////////////////////////////////////////////////////
//  Copyright (C) Wizardry and Steamworks 2017 - License: GNU GPLv3      //
//  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  //
//  rights of fair usage, the disclaimer and warranty conditions.        //
///////////////////////////////////////////////////////////////////////////

using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
using System.Xml.XPath;

namespace wasStitchNET.Patchers
{
    public static class XML
    {
        public static XDocument PatchXDocument(XDocument cfg, XDocument nfg, HashSet<string> forceXPaths,
            HashSet<string> excludeXPaths)
        {
            // Select all distinct paths in the new configuration without paths to exclude and with paths to force.
            foreach (var e in nfg
                .Descendants()
                .Where(e => !excludeXPaths.Any(o => e.GetAbsoluteXPath().Contains(o)))
                .Concat(
                    nfg
                        .Descendants()
                        .Where(e => forceXPaths.Any(o => e.GetAbsoluteXPath().Contains(o))))
                .Distinct())
            {
                // Get the XPath to this element.
                var xpath = e.GetAbsoluteXPath();
                // Select the element in the current configuration that is found in the default configuration.
                var cfgElement = cfg.XPathSelectElement(xpath);
                switch (cfgElement != null)
                {
                    // Element found in current configuration.
                    case true:
                        // Only set the element value if it has no descendants and it contained in the force paths.
                        if (!cfgElement.Descendants().Any() && forceXPaths.Any(o => xpath.Contains(o)))
                            cfgElement.Value = e.Value;
                        break;
                    // Element not found in the current configuration.
                    default:
                        // Find the first existing parent of the default configuration in the current configuration.
                        var parent = e;
                        do
                        {
                            var cfgParentElement = cfg.XPathSelectElement(parent.GetAbsoluteXPath());
                            if (cfgParentElement != null)
                            {
                                // Add the default configuration parent to the current configuration.
                                cfgParentElement.Add(
                                    nfg.XPathSelectElement(cfgParentElement.GetAbsoluteXPath()));
                                break;
                            }
                            parent = parent.Parent;
                        } while (parent != null);
                        break;
                }
            }
            return cfg;
        }
    }
}