using System.Collections.Generic;
using System.Xml;

namespace Webserver.Permissions {
	public class AdminWebModules : AdminSectionAbs {
		public static AdminWebModules Instance { get; private set; }

		public AdminWebModules (AdminTools _parent) : base (_parent, "webmodules") {
			Instance = this;
		}

		private readonly Dictionary<string, WebModule> modules = new CaseInsensitiveStringDictionary<WebModule> ();


#region IO

		public override void Clear () {
			modules.Clear ();
		}

		protected override void ParseElement (XmlElement _childElement) {
			if (WebModule.TryParse (_childElement, out WebModule webModule)) {
				modules [webModule.Name] = webModule;
			}
		}

		public override void Save (XmlElement _root) {
			XmlElement modulesElement = _root.AddXmlElement (SectionTypeName);
			// modulesElement.AddXmlComment (" <module name=\"adminuser1\" secret=\"supersecrettoken\" permission_level=\"0\" /> ");

			foreach ((string _, WebModule module) in modules) {
				module.ToXml (modulesElement);
			}
		}

#endregion


#region Runtime interaction


		public void AddModule (string _module, int _permissionLevel) {
			WebModule p = new WebModule (_module, _permissionLevel, false);
			lock (this) {
				allModulesList.Clear ();
				
				modules [_module] = p;
				Parent.Save ();
			}
		}

		public bool RemoveModule (string _module) {
			lock (this) {
				allModulesList.Clear ();
				
				bool removed = modules.Remove (_module);
				if (removed) {
					Parent.Save ();
				}

				return removed;
			}
		}

		public List<WebModule> GetModules () {
			lock (this) {
				if (allModulesList.Count != 0) {
					return allModulesList;
				}

				foreach ((string moduleName, WebModule moduleDefaultPerm) in knownModules) {
					allModulesList.Add (modules.TryGetValue (moduleName, out WebModule modulePermission)
						? modulePermission
						: moduleDefaultPerm);
				}

				return allModulesList;
			}
		}

#endregion

		public readonly struct WebModule {
			public readonly string Name;
			public readonly int PermissionLevel;
			public readonly bool IsDefault;

			public WebModule (string _name, int _permissionLevel, bool _isDefault) {
				Name = _name;
				PermissionLevel = _permissionLevel;
				IsDefault = _isDefault;
			}
			
			public void ToXml (XmlElement _parent) {
				_parent.AddXmlElement ("module")
						.SetAttrib ("name", Name)
						.SetAttrib ("permission_level", PermissionLevel.ToString ());
			}

			public static bool TryParse (XmlElement _element, out WebModule _result) {
				_result = default;


				if (!_element.TryGetAttribute ("name", out string name)) {
					Log.Warning ($"[Web] [Perms] Ignoring module-entry because of missing 'name' attribute: {_element.OuterXml}");
					return false;
				}

				if (!_element.TryGetAttribute ("permission_level", out string permissionLevelString)) {
					Log.Warning ($"[Web] [Perms] Ignoring module-entry because of missing 'permission_level' attribute: {_element.OuterXml}");
					return false;
				}

				if (!int.TryParse (permissionLevelString, out int permissionLevel)) {
					Log.Warning (
						$"[Web] [Perms] Ignoring module-entry because of invalid (non-numeric) value for 'permission_level' attribute: {_element.OuterXml}");
					return false;
				}
				
				_result = new WebModule (name, permissionLevel, false);
				return true;
			}
		}


#region Specials

		/// <summary>
		/// Contains all registered modules and their default permission
		/// </summary>
		private readonly Dictionary<string, WebModule> knownModules = new CaseInsensitiveStringDictionary<WebModule> ();

		/// <summary>
		/// Public list of all modules, both those with custom permissions as well as those that do not with their default permission
		/// </summary>
		private readonly List<WebModule> allModulesList = new List<WebModule> ();

		public void AddKnownModule (string _module, int _defaultPermission) {
			if (string.IsNullOrEmpty (_module)) {
				return;
			}

			WebModule p = new WebModule (_module, _defaultPermission, true);

			lock (this) {
				allModulesList.Clear ();
				knownModules [_module] = p;
			}
		}

		public bool IsKnownModule (string _module) {
			if (string.IsNullOrEmpty (_module)) {
				return false;
			}

			lock (this) {
				return knownModules.ContainsKey (_module);
			}
		}

		public bool ModuleAllowedWithLevel (string _module, int _level) {
			WebModule permInfo = GetModule (_module)!.Value;
			return permInfo.PermissionLevel >= _level;
		}

		public WebModule? GetModule (string _module, bool _returnDefaults = true) {
			if (modules.TryGetValue (_module, out WebModule result)) {
				return result;
			}

			if (!_returnDefaults) {
				return null;
			}

			return knownModules.TryGetValue (_module, out result) ? result : defaultModulePermission;
		}

		private readonly WebModule defaultModulePermission = new WebModule ("", 0, true);
		
#endregion
	}
}