namespace System.Web.Mvc {
    using System;
    using System.Collections.Generic;
    using System.Diagnostics.CodeAnalysis;
    using System.Globalization;
    using System.Linq;
    using System.Web;
    using System.Web.Hosting;
    using System.Web.Mvc.Resources;

    public abstract class VirtualPathProviderViewEngine : IViewEngine {
        // format is ":ViewCacheEntry:{cacheType}:{prefix}:{name}:{controllerName}:{areaName}:"
        private const string _cacheKeyFormat = ":ViewCacheEntry:{0}:{1}:{2}:{3}:{4}:";
        private const string _cacheKeyPrefix_Master = "Master";
        private const string _cacheKeyPrefix_Partial = "Partial";
        private const string _cacheKeyPrefix_View = "View";
        private static readonly string[] _emptyLocations = new string[0];

        private VirtualPathProvider _vpp;
        internal Func<string, string> GetExtensionThunk = VirtualPathUtility.GetExtension;

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] AreaMasterLocationFormats {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] AreaPartialViewLocationFormats {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] AreaViewLocationFormats {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] FileExtensions {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] MasterLocationFormats {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] PartialViewLocationFormats {
            get;
            set;
        }

        public IViewLocationCache ViewLocationCache {
            get;
            set;
        }

        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] ViewLocationFormats {
            get;
            set;
        }

        protected VirtualPathProvider VirtualPathProvider {
            get {
                if (_vpp == null) {
                    _vpp = HostingEnvironment.VirtualPathProvider;
                }
                return _vpp;
            }
            set {
                _vpp = value;
            }
        }

        protected VirtualPathProviderViewEngine() {
            if (HttpContext.Current == null || HttpContext.Current.IsDebuggingEnabled) {
                ViewLocationCache = DefaultViewLocationCache.Null;
            }
            else {
                ViewLocationCache = new DefaultViewLocationCache();
            }
        }

        private string CreateCacheKey(string prefix, string name, string controllerName, string areaName) {
            return String.Format(CultureInfo.InvariantCulture, _cacheKeyFormat,
                GetType().AssemblyQualifiedName, prefix, name, controllerName, areaName);
        }

        protected abstract IView CreatePartialView(ControllerContext controllerContext, string partialPath);

        protected abstract IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath);

        protected virtual bool FileExists(ControllerContext controllerContext, string virtualPath) {
            return VirtualPathProvider.FileExists(virtualPath);
        }

        public virtual ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache) {
            if (controllerContext == null) {
                throw new ArgumentNullException("controllerContext");
            }
            if (String.IsNullOrEmpty(partialViewName)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "partialViewName");
            }

            string[] searched;
            string controllerName = controllerContext.RouteData.GetRequiredString("controller");
            string partialPath = GetPath(controllerContext, PartialViewLocationFormats, AreaPartialViewLocationFormats, "PartialViewLocationFormats", partialViewName, controllerName, _cacheKeyPrefix_Partial, useCache, out searched);

            if (String.IsNullOrEmpty(partialPath)) {
                return new ViewEngineResult(searched);
            }

            return new ViewEngineResult(CreatePartialView(controllerContext, partialPath), this);
        }

        public virtual ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache) {
            if (controllerContext == null) {
                throw new ArgumentNullException("controllerContext");
            }
            if (String.IsNullOrEmpty(viewName)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "viewName");
            }

            string[] viewLocationsSearched;
            string[] masterLocationsSearched;

            string controllerName = controllerContext.RouteData.GetRequiredString("controller");
            string viewPath = GetPath(controllerContext, ViewLocationFormats, AreaViewLocationFormats, "ViewLocationFormats", viewName, controllerName, _cacheKeyPrefix_View, useCache, out viewLocationsSearched);
            string masterPath = GetPath(controllerContext, MasterLocationFormats, AreaMasterLocationFormats, "MasterLocationFormats", masterName, controllerName, _cacheKeyPrefix_Master, useCache, out masterLocationsSearched);

            if (String.IsNullOrEmpty(viewPath) || (String.IsNullOrEmpty(masterPath) && !String.IsNullOrEmpty(masterName))) {
                return new ViewEngineResult(viewLocationsSearched.Union(masterLocationsSearched));
            }

            return new ViewEngineResult(CreateView(controllerContext, viewPath, masterPath), this);
        }

        private string GetPath(ControllerContext controllerContext, string[] locations, string[] areaLocations, string locationsPropertyName, string name, string controllerName, string cacheKeyPrefix, bool useCache, out string[] searchedLocations) {
            searchedLocations = _emptyLocations;

            if (String.IsNullOrEmpty(name)) {
                return String.Empty;
            }

            string areaName = AreaHelpers.GetAreaName(controllerContext.RouteData);
            bool usingAreas = !String.IsNullOrEmpty(areaName);
            List<ViewLocation> viewLocations = GetViewLocations(locations, (usingAreas) ? areaLocations : null);

            if (viewLocations.Count == 0) {
                throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture,
                    MvcResources.Common_PropertyCannotBeNullOrEmpty, locationsPropertyName));
            }

            bool nameRepresentsPath = IsSpecificPath(name);
            string cacheKey = CreateCacheKey(cacheKeyPrefix, name, (nameRepresentsPath) ? String.Empty : controllerName, areaName);

            if (useCache) {
                return ViewLocationCache.GetViewLocation(controllerContext.HttpContext, cacheKey);
            }

            return (nameRepresentsPath) ?
                GetPathFromSpecificName(controllerContext, name, cacheKey, ref searchedLocations) :
                GetPathFromGeneralName(controllerContext, viewLocations, name, controllerName, areaName, cacheKey, ref searchedLocations);
        }

        private string GetPathFromGeneralName(ControllerContext controllerContext, List<ViewLocation> locations, string name, string controllerName, string areaName, string cacheKey, ref string[] searchedLocations) {
            string result = String.Empty;
            searchedLocations = new string[locations.Count];

            for (int i = 0; i < locations.Count; i++) {
                ViewLocation location = locations[i];
                string virtualPath = location.Format(name, controllerName, areaName);

                if (FileExists(controllerContext, virtualPath)) {
                    searchedLocations = _emptyLocations;
                    result = virtualPath;
                    ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
                    break;
                }

                searchedLocations[i] = virtualPath;
            }

            return result;
        }

        private string GetPathFromSpecificName(ControllerContext controllerContext, string name, string cacheKey, ref string[] searchedLocations) {
            string result = name;

            if (!(FilePathIsSupported(name) && FileExists(controllerContext, name))) {
                result = String.Empty;
                searchedLocations = new[] { name };
            }

            ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
            return result;
        }

        private bool FilePathIsSupported(string virtualPath) {
            if (FileExtensions == null) {
                // legacy behavior for custom ViewEngine that might not set the FileExtensions property
                return true;
            }
            else {
                // get rid of the '.' because the FileExtensions property expects extensions withouth a dot.
                string extension = GetExtensionThunk(virtualPath).TrimStart('.');
                return FileExtensions.Contains(extension, StringComparer.OrdinalIgnoreCase);
            }
        }

        private static List<ViewLocation> GetViewLocations(string[] viewLocationFormats, string[] areaViewLocationFormats) {
            List<ViewLocation> allLocations = new List<ViewLocation>();

            if (areaViewLocationFormats != null) {
                foreach (string areaViewLocationFormat in areaViewLocationFormats) {
                    allLocations.Add(new AreaAwareViewLocation(areaViewLocationFormat));
                }
            }

            if (viewLocationFormats != null) {
                foreach (string viewLocationFormat in viewLocationFormats) {
                    allLocations.Add(new ViewLocation(viewLocationFormat));
                }
            }

            return allLocations;
        }

        private static bool IsSpecificPath(string name) {
            char c = name[0];
            return (c == '~' || c == '/');
        }

        public virtual void ReleaseView(ControllerContext controllerContext, IView view) {
            IDisposable disposable = view as IDisposable;
            if (disposable != null) {
                disposable.Dispose();
            }
        }

        private class ViewLocation {

            protected string _virtualPathFormatString;

            public ViewLocation(string virtualPathFormatString) {
                _virtualPathFormatString = virtualPathFormatString;
            }

            public virtual string Format(string viewName, string controllerName, string areaName) {
                return String.Format(CultureInfo.InvariantCulture, _virtualPathFormatString, viewName, controllerName);
            }

        }

        private class AreaAwareViewLocation : ViewLocation {

            public AreaAwareViewLocation(string virtualPathFormatString)
                : base(virtualPathFormatString) {
            }

            public override string Format(string viewName, string controllerName, string areaName) {
                return String.Format(CultureInfo.InvariantCulture, _virtualPathFormatString, viewName, controllerName, areaName);
            }

        }
    }
}