namespace System.Web.Mvc {
    using System;
    using System.Diagnostics.CodeAnalysis;
    using System.Web;
    using System.Web.Routing;
    using System.Web.Mvc.Html;

    // Though many of the properties on ControllerContext and its subclassed types are virtual, there are still sealed
    // properties (like ControllerContext.RequestContext, ActionExecutingContext.Result, etc.). If these properties
    // were virtual, a mocking framework might override them with incorrect behavior (property getters would return
    // null, property setters would be no-ops). By sealing these properties, we are forcing them to have the default
    // "get or store a value" semantics that they were intended to have.

    public class ControllerContext {

        private HttpContextBase _httpContext;
        private RequestContext _requestContext;
        private RouteData _routeData;

        internal const string PARENT_ACTION_VIEWCONTEXT = "ParentActionViewContext";

        // parameterless constructor used for mocking
        public ControllerContext() {
        }

        // copy constructor - allows for subclassed types to take an existing ControllerContext as a parameter
        // and we'll automatically set the appropriate properties
        [SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors", Justification = "The virtual property setters are only to support mocking frameworks, in which case this constructor shouldn't be called anyway.")]
        protected ControllerContext(ControllerContext controllerContext) {
            if (controllerContext == null) {
                throw new ArgumentNullException("controllerContext");
            }

            Controller = controllerContext.Controller;
            RequestContext = controllerContext.RequestContext;
        }

        public ControllerContext(HttpContextBase httpContext, RouteData routeData, ControllerBase controller)
            : this(new RequestContext(httpContext, routeData), controller) {
        }

        [SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors", Justification = "The virtual property setters are only to support mocking frameworks, in which case this constructor shouldn't be called anyway.")]
        public ControllerContext(RequestContext requestContext, ControllerBase controller) {
            if (requestContext == null) {
                throw new ArgumentNullException("requestContext");
            }
            if (controller == null) {
                throw new ArgumentNullException("controller");
            }

            RequestContext = requestContext;
            Controller = controller;
        }

        public virtual ControllerBase Controller {
            get;
            set;
        }

        public virtual HttpContextBase HttpContext {
            get {
                if (_httpContext == null) {
                    _httpContext = (_requestContext != null) ? _requestContext.HttpContext : new EmptyHttpContext();
                }
                return _httpContext;
            }
            set {
                _httpContext = value;
            }
        }

        public virtual bool IsChildAction {
            get {
                RouteData routeData = RouteData;
                if (routeData == null) {
                    return false;
                }
                return routeData.DataTokens.ContainsKey(PARENT_ACTION_VIEWCONTEXT);
            }
        }

        public ViewContext ParentActionViewContext {
            get {
                return RouteData.DataTokens[PARENT_ACTION_VIEWCONTEXT] as ViewContext;
            }
        }

        public RequestContext RequestContext {
            get {
                if (_requestContext == null) {
                    // still need explicit calls to constructors since the property getters are virtual and might return null
                    HttpContextBase httpContext = HttpContext ?? new EmptyHttpContext();
                    RouteData routeData = RouteData ?? new RouteData();

                    _requestContext = new RequestContext(httpContext, routeData);
                }
                return _requestContext;
            }
            set {
                _requestContext = value;
            }
        }

        public virtual RouteData RouteData {
            get {
                if (_routeData == null) {
                    _routeData = (_requestContext != null) ? _requestContext.RouteData : new RouteData();
                }
                return _routeData;
            }
            set {
                _routeData = value;
            }
        }

        private sealed class EmptyHttpContext : HttpContextBase {
        }

    }
}