using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Security.AccessControl;
using System.Security.Principal;
using WebDAVSharp.Server.Exceptions;

namespace WebDAVSharp.Server.Stores.DiskStore {
	/// <summary>
	/// This class implements a disk-based <see cref="IWebDavStore" /> that maps to a folder on disk.
	/// </summary>
	[DebuggerDisplay("Directory ({Name})")]
	public sealed class WebDavDiskStoreCollection : WebDavDiskStoreItem, IWebDavStoreCollection {
		private readonly Dictionary<string, WeakReference> _items = new Dictionary<string, WeakReference>();

		/// <summary>
		/// Initializes a new instance of the <see cref="WebDavDiskStoreCollection" /> class.
		/// </summary>
		/// <param name="parentCollection">The parent <see cref="WebDavDiskStoreCollection" /> that contains this <see cref="WebDavDiskStoreCollection" />.</param>
		/// <param name="path">The path to the folder on this that this <see cref="WebDavDiskStoreCollection" /> maps to.</param>
		public WebDavDiskStoreCollection(WebDavDiskStoreCollection parentCollection, string path)
				: base(parentCollection, path) {

		}

		#region IWebDAVStoreCollection Members

		/// <summary>
		/// Gets a collection of all the items in this <see cref="IWebDavStoreCollection" />.
		/// </summary>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">If the user is unauthorized or doesn't have access</exception>
		public IEnumerable<IWebDavStoreItem> Items {
			get {
				HashSet<WeakReference> toDelete = new HashSet<WeakReference>(_items.Values);
				List<IWebDavStoreItem> items = new List<IWebDavStoreItem>();

				// TODO: Refactor to get rid of duplicate loop code
				List<string> directories = new List<string>();
				try {
					// Impersonate the current user and get all the directories
					using (Identity.Impersonate()) {
						foreach (string dirName in Directory.GetDirectories(ItemPath)) {
							try {
								bool canread = CanReadDirectory(Path.Combine(ItemPath, dirName));
								if (canread) {
									directories.Add(dirName);
								}
							}
							catch (Exception) {
								// do nothing
							}
						}
					}
				}
				catch {
					throw new WebDavUnauthorizedException();
				}
				foreach (string subDirectoryPath in directories) {
					string name = Path.GetFileName(subDirectoryPath);
					WebDavDiskStoreCollection collection = null;

					WeakReference wr;
					if (_items.TryGetValue(name, out wr)) {
						collection = wr.Target as WebDavDiskStoreCollection;
						if (collection == null)
							toDelete.Remove(wr);
					}

					if (collection == null) {
						collection = new WebDavDiskStoreCollection(this, subDirectoryPath);
						_items[name] = new WeakReference(collection);
					}

					items.Add(collection);
				}
				List<string> files = new List<string>();
				try {
					// Impersonate the current user and get all the files
					using (Identity.Impersonate()) {
						files.AddRange(Directory.GetFiles(ItemPath).Where(fileName => CanReadFile(Path.Combine(ItemPath, fileName))));
					}
				}
				catch {
					throw new WebDavUnauthorizedException();
				}
				foreach (string filePath in files) {
					string name = Path.GetFileName(filePath);
					WebDavDiskStoreDocument document = null;

					WeakReference wr;
					if (_items.TryGetValue(name, out wr)) {
						document = wr.Target as WebDavDiskStoreDocument;
						if (document == null)
							toDelete.Remove(wr);
					}

					if (document == null) {
						document = new WebDavDiskStoreDocument(this, filePath);
						_items[name] = new WeakReference(document);
					}
					items.Add(document);
				}
				return items.ToArray();
			}
		}

		/// <summary>
		/// Checks if the user has access to the path
		/// </summary>
		/// <param name="path">The path.</param>
		/// <returns>
		/// True if access, false if not
		/// </returns>
		private bool CanRead(string path) {
			if (File.Exists(path))
				return CanReadFile(path);
			return Directory.Exists(path) && CanReadDirectory(path);
		}

		/// <summary>
		/// Checks if access to the file is granted.
		/// </summary>
		/// <param name="path">The path to the file as a <see cref="string" /></param>
		/// <returns>
		/// The <see cref="bool" /> true if the user has access, else false
		/// </returns>
		/// <remarks>
		/// Source: <see href="http://stackoverflow.com/questions/17318585/check-if-file-can-be-read" />
		/// </remarks>
		private static bool CanReadFile(string path) {
			try {
				File.Open(path, FileMode.Open, FileAccess.Read).Dispose();
				return true;
			}
			catch (Exception) {
				return false;
			}
		}

		/// <summary>
		/// Checks if access to the directory is granted.
		/// </summary>
		/// <param name="path">The path to the director as a <see cref="string" /></param>
		/// <returns>
		/// The <see cref="bool" /> true if the user has access, else false
		/// </returns>
		/// <remarks>
		/// Source: <see href="http://stackoverflow.com/questions/11709862/check-if-directory-is-accessible-in-c" />
		/// </remarks>
		private static bool CanReadDirectory(string path) {
			bool readAllow = false;
			bool readDeny = false;
			DirectorySecurity accessControlList = Directory.GetAccessControl(path);
			if (accessControlList == null)
				return false;
			AuthorizationRuleCollection accessRules = accessControlList.GetAccessRules(true, true, typeof(SecurityIdentifier));

			foreach (FileSystemAccessRule rule in accessRules.Cast<FileSystemAccessRule>().Where(rule => (FileSystemRights.Read & rule.FileSystemRights) == FileSystemRights.Read)) {
				switch (rule.AccessControlType) {
					case AccessControlType.Allow:
						readAllow = true;
						break;
					case AccessControlType.Deny:
						readDeny = true;
						break;
				}
			}

			return readAllow && !readDeny;
		}

		/// <summary>
		/// Retrieves a store item by its name.
		/// </summary>
		/// <param name="name">The name of the store item to retrieve.</param>
		/// <returns>
		/// The store item that has the specified 
		/// <paramref name="name" />;
		/// or 
		/// <c>null</c> if there is no store item with that name.
		/// </returns>
		public IWebDavStoreItem GetItemByName(string name) {
			string path = Path.Combine(ItemPath, name);

			using (Identity.Impersonate()) {
				if (File.Exists(path) && CanReadFile(path))
					return new WebDavDiskStoreDocument(this, path);
				if (Directory.Exists(path) && CanReadDirectory(path))
					return new WebDavDiskStoreCollection(this, path);
			}

			return null;
		}

		/// <summary>
		/// Creates a new collection with the specified name.
		/// </summary>
		/// <param name="name">The name of the new collection.</param>
		/// <returns>
		/// The created <see cref="IWebDavStoreCollection" /> instance.
		/// </returns>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">When the user is unauthorized or has no access</exception>
		public IWebDavStoreCollection CreateCollection(string name) {
			string path = Path.Combine(ItemPath, name);

			try {
				// Impersonate the current user and make file changes
				WindowsImpersonationContext wic = Identity.Impersonate();
				Directory.CreateDirectory(path);
				wic.Undo();
			}
			catch {
				throw new WebDavUnauthorizedException();
			}

			return GetItemByName(name) as IWebDavStoreCollection;
		}

		/// <summary>
		/// Deletes a store item by its name.
		/// </summary>
		/// <param name="item">The name of the store item to delete.</param>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavNotFoundException">If the item was not found.</exception>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">If the user is unauthorized or has no access.</exception>
		public void Delete(IWebDavStoreItem item) {
			WebDavDiskStoreItem diskItem = (WebDavDiskStoreItem)item;
			string itemPath = diskItem.ItemPath;
			if (item is WebDavDiskStoreDocument) {
				if (!File.Exists(itemPath))
					throw new WebDavNotFoundException();
				try {
					// Impersonate the current user and delete the file
					WindowsImpersonationContext wic = Identity.Impersonate();
					File.Delete(itemPath);
					wic.Undo();

				}
				catch {
					throw new WebDavUnauthorizedException();
				}
			}
			else {
				if (!Directory.Exists(itemPath))
					throw new WebDavNotFoundException();
				try {
					// Impersonate the current user and delete the directory
					WindowsImpersonationContext wic = Identity.Impersonate();
					Directory.Delete(diskItem.ItemPath);
					wic.Undo();
				}
				catch {
					throw new WebDavUnauthorizedException();
				}
			}
		}

		/// <summary>
		/// Creates a new document with the specified name.
		/// </summary>
		/// <param name="name">The name of the new document.</param>
		/// <returns>
		/// The created <see cref="IWebDavStoreDocument" /> instance.
		/// </returns>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavConflictException">If the item already exists</exception>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">If the user is unauthorized or has no access</exception>
		public IWebDavStoreDocument CreateDocument(string name) {
			string itemPath = Path.Combine(ItemPath, name);
			if (File.Exists(itemPath) || Directory.Exists(itemPath))
				throw new WebDavConflictException();

			try {
				// Impersonate the current user and delete the directory
				WindowsImpersonationContext wic = Identity.Impersonate();
				File.Create(itemPath).Dispose();
				wic.Undo();
			}
			catch {
				throw new WebDavUnauthorizedException();
			}

			WebDavDiskStoreDocument document = new WebDavDiskStoreDocument(this, itemPath);
			_items.Add(name, new WeakReference(document));
			return document;

		}

		/// <summary>
		/// Copies an existing store item into this collection, overwriting any existing items.
		/// </summary>
		/// <param name="source">The store item to copy from.</param>
		/// <param name="destinationName">The name of the copy to create of <paramref name="source" />.</param>
		/// <param name="includeContent">The boolean for copying the containing files/folders or not.</param>
		/// <returns>
		/// The created <see cref="IWebDavStoreItem" /> instance.
		/// </returns>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">If the user is unauthorized or has no access</exception>
		public IWebDavStoreItem CopyItemHere(IWebDavStoreItem source, string destinationName, bool includeContent) {
			// We get the path of
			string destinationItemPath = Path.Combine(ItemPath, destinationName);

			// the moving of the item
			if (source.IsCollection) {
				try {
					// Impersonate the current user and move the directory
					WindowsImpersonationContext wic = Identity.Impersonate();
					DirectoryCopy(source.ItemPath, destinationItemPath, true);
					wic.Undo();
				}
				catch {
					throw new WebDavUnauthorizedException();
				}

				// We return the moved file as a WebDAVDiskStoreDocument
				WebDavDiskStoreCollection collection = new WebDavDiskStoreCollection(this, destinationItemPath);
				_items.Add(destinationName, new WeakReference(collection));
				return collection;
			}


			// We copy the file with an override.
			try {
				// Impersonate the current user and copy the file
				WindowsImpersonationContext wic = Identity.Impersonate();
				File.Copy(source.ItemPath, destinationItemPath, true);
				wic.Undo();
			}
			catch {
				throw new WebDavUnauthorizedException();
			}

			// We return the moved file as a WebDAVDiskStoreDocument
			WebDavDiskStoreDocument document = new WebDavDiskStoreDocument(this, destinationItemPath);
			_items.Add(destinationName, new WeakReference(document));
			return document;

		}

		/// <summary>
		/// Directories the copy.
		/// </summary>
		/// <param name="sourceDirName">Name of the source dir.</param>
		/// <param name="destDirName">Name of the dest dir.</param>
		/// <param name="copySubDirs">if set to <c>true</c> [copy sub dirs].</param>
		/// <exception cref="System.IO.DirectoryNotFoundException">Source directory does not exist or could not be found: 
		///                     + sourceDirName</exception>
		private static void DirectoryCopy(string sourceDirName, string destDirName, bool copySubDirs) {
			// Get the subdirectories for the specified directory.
			DirectoryInfo dir = new DirectoryInfo(sourceDirName);
			DirectoryInfo[] dirs = dir.GetDirectories();

			if (!dir.Exists) {
				throw new DirectoryNotFoundException(
						"Source directory does not exist or could not be found: "
						+ sourceDirName);
			}

			// If the destination directory doesn't exist, create it. 
			if (!Directory.Exists(destDirName)) {
				Directory.CreateDirectory(destDirName);
			}

			// If copying subdirectories, copy them and their contents to new location. 
			if (!copySubDirs) return;
			// Get the files in the directory and copy them to the new location.
			FileInfo[] files = dir.GetFiles();
			foreach (FileInfo file in files)
				file.CopyTo(Path.Combine(destDirName, file.Name), false);

			foreach (DirectoryInfo subdir in dirs)
				DirectoryCopy(subdir.FullName, Path.Combine(destDirName, subdir.Name), copySubDirs);
		}

		/// <summary>
		/// Moves an existing store item into this collection, overwriting any existing items.
		/// </summary>
		/// <param name="source">The store item to move.</param>
		/// <param name="destinationName">The
		/// <see cref="IWebDavStoreItem" /> that refers to the item that was moved,
		/// in its new location.</param>
		/// <returns>
		/// The moved <see cref="IWebDavStoreItem" /> instance.
		/// </returns>
		/// <exception cref="System.Exception">Path to the source item not defined.</exception>
		/// <exception cref="WebDAVSharp.Server.Exceptions.WebDavUnauthorizedException">If the user is unauthorized or has no access</exception>
		/// <remarks>
		/// Note that the method should fail without creating or overwriting content in the
		/// target collection if the move cannot go through.
		/// </remarks>
		public IWebDavStoreItem MoveItemHere(IWebDavStoreItem source, string destinationName) {
			// try to get the path of the source item
			string sourceItemPath = "";
			WebDavDiskStoreItem sourceItem = (WebDavDiskStoreItem)source;
			sourceItemPath = sourceItem.ItemPath;

			if (sourceItemPath.Equals("")) {
				throw new Exception("Path to the source item not defined.");
			}

			// We get the path of
			string destinationItemPath = Path.Combine(ItemPath, destinationName);

			// the moving of the item
			if (source.IsCollection) {
				try {
					// Impersonate the current user and move the directory
					WindowsImpersonationContext wic = Identity.Impersonate();
					Directory.Move(sourceItemPath, destinationItemPath);
					wic.Undo();
				}
				catch {
					throw new WebDavUnauthorizedException();
				}

				// We return the moved file as a WebDAVDiskStoreDocument
				var collection = new WebDavDiskStoreCollection(this, destinationItemPath);
				_items.Add(destinationName, new WeakReference(collection));
				return collection;
			}

			try {
				// Impersonate the current user and move the file
				WindowsImpersonationContext wic = Identity.Impersonate();
				File.Move(sourceItemPath, destinationItemPath);
				wic.Undo();
			}
			catch {
				throw new WebDavUnauthorizedException();
			}

			// We return the moved file as a WebDAVDiskStoreDocument
			WebDavDiskStoreDocument document = new WebDavDiskStoreDocument(this, destinationItemPath);
			_items.Add(destinationName, new WeakReference(document));
			return document;

		}

		#endregion
	}
}