// Copyright Epic Games, Inc. All Rights Reserved.

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace EpicGames.Core
{
	/// <summary>
	/// Representation of an absolute file path. Allows fast hashing and comparisons.
	/// </summary>
	[Serializable]
	public class FileReference : FileSystemReference, IEquatable<FileReference>, IComparable<FileReference>
	{
		/// <summary>
		/// Dummy enum to allow invoking the constructor which takes a sanitized full path
		/// </summary>
		public enum Sanitize
		{
			None
		}

		/// <summary>
		/// Default constructor.
		/// </summary>
		/// <param name="inPath">Path to this file</param>
		public FileReference(string inPath)
			: base(Path.GetFullPath(inPath))
		{
			if(FullName[^1] == '\\' || FullName[^1] == '/')
			{
				throw new ArgumentException("File names may not be terminated by a path separator character");
			}
		}

		/// <summary>
		/// Construct a FileReference from a FileInfo object.
		/// </summary>
		/// <param name="inInfo">Path to this file</param>
		public FileReference(FileInfo inInfo)
			: base(inInfo.FullName)
		{
		}

		/// <summary>
		/// Default constructor.
		/// </summary>
		/// <param name="fullName">The full sanitized path</param>
		public FileReference(string fullName, Sanitize _)
			: base(fullName)
		{
		}

		/// <summary>
		/// Create a FileReference from a string. If the string is null, returns a null FileReference.
		/// </summary>
		/// <param name="fileName">FileName for the string</param>
		/// <returns>Returns a FileReference representing the given string, or null.</returns>
		[return: NotNullIfNotNull("fileName")]
		public static FileReference? FromString(string? fileName)
		{
			if(String.IsNullOrEmpty(fileName))
			{
				return null;
			}
			else
			{
				return new FileReference(fileName);
			}
		}

		/// <summary>
		/// Gets the file name without path information
		/// </summary>
		/// <returns>A string containing the file name</returns>
		public string GetFileName()
		{
			return Path.GetFileName(FullName);
		}

		/// <summary>
		/// Gets the file name without path information or an extension
		/// </summary>
		/// <returns>A string containing the file name without an extension</returns>
		public string GetFileNameWithoutExtension()
		{
			return Path.GetFileNameWithoutExtension(FullName);
		}

		/// <summary>
		/// Gets the file name without path or any extensions
		/// </summary>
		/// <returns>A string containing the file name without an extension</returns>
		public string GetFileNameWithoutAnyExtensions()
		{
			int startIdx = FullName.LastIndexOf(Path.DirectorySeparatorChar) + 1;

			int endIdx = FullName.IndexOf('.', startIdx);
			if (endIdx < startIdx)
			{
				return FullName.Substring(startIdx);
			}
			else
			{
				return FullName.Substring(startIdx, endIdx - startIdx);
			}
		}

		/// <summary>
		/// Gets the extension for this filename
		/// </summary>
		/// <returns>A string containing the extension of this filename</returns>
		public string GetExtension()
		{
			return Path.GetExtension(FullName);
		}

		/// <summary>
		/// Change the file's extension to something else
		/// </summary>
		/// <param name="extension">The new extension</param>
		/// <returns>A FileReference with the same path and name, but with the new extension</returns>
		public FileReference ChangeExtension(string? extension)
		{
			string newFullName = Path.ChangeExtension(FullName, extension);
			return new FileReference(newFullName, Sanitize.None);
		}

		/// <summary>
		/// Gets the directory containing this file
		/// </summary>
		/// <returns>A new directory object representing the directory containing this object</returns>
		public DirectoryReference Directory
		{
			get
			{
				int parentLength = FullName.LastIndexOf(Path.DirectorySeparatorChar);

				if (parentLength == 2 && FullName[1] == ':')
				{
					// windows root detected (C:)
					parentLength++;
				}

				if (parentLength == 0 && FullName[0] == Path.DirectorySeparatorChar)
				{
					// nix style root (/) detected
					parentLength = 1;
				}

				return new DirectoryReference(FullName.Substring(0, parentLength), DirectoryReference.Sanitize.None);
			}
		}

		/// <summary>
		/// Combine several fragments with a base directory, to form a new filename
		/// </summary>
		/// <param name="baseDirectory">The base directory</param>
		/// <param name="fragments">Fragments to combine with the base directory</param>
		/// <returns>The new file name</returns>
		public static FileReference Combine(DirectoryReference baseDirectory, params string[] fragments)
		{
			string fullName = FileSystemReference.CombineStrings(baseDirectory, fragments);
			return new FileReference(fullName, Sanitize.None);
		}

		/// <summary>
		/// Append a string to the end of a filename
		/// </summary>
		/// <param name="a">The base file reference</param>
		/// <param name="b">Suffix to be appended</param>
		/// <returns>The new file reference</returns>
		public static FileReference operator +(FileReference a, string b)
		{
			return new FileReference(a.FullName + b, Sanitize.None);
		}

		/// <summary>
		/// Compares two filesystem object names for equality. Uses the canonical name representation, not the display name representation.
		/// </summary>
		/// <param name="a">First object to compare.</param>
		/// <param name="b">Second object to compare.</param>
		/// <returns>True if the names represent the same object, false otherwise</returns>
		public static bool operator ==(FileReference? a, FileReference? b)
		{
			if (a is null)
			{
				return b is null;
			}
			else if (b is null)
			{
				return false;
			}
			else
			{
				return a.FullName.Equals(b.FullName, Comparison);
			}
		}

		/// <summary>
		/// Compares two filesystem object names for inequality. Uses the canonical name representation, not the display name representation.
		/// </summary>
		/// <param name="a">First object to compare.</param>
		/// <param name="b">Second object to compare.</param>
		/// <returns>False if the names represent the same object, true otherwise</returns>
		public static bool operator !=(FileReference? a, FileReference? b)
		{
			return !(a == b);
		}

		/// <summary>
		/// Compares against another object for equality.
		/// </summary>
		/// <param name="obj">other instance to compare.</param>
		/// <returns>True if the names represent the same object, false otherwise</returns>
		public override bool Equals(object? obj) => obj is FileReference file && file == this;

		/// <summary>
		/// Compares against another object for equality.
		/// </summary>
		/// <param name="obj">other instance to compare.</param>
		/// <returns>True if the names represent the same object, false otherwise</returns>
		public bool Equals(FileReference? obj)
		{
			return obj == this;
		}

		/// <summary>
		/// Returns a hash code for this object
		/// </summary>
		/// <returns></returns>
		public override int GetHashCode()
		{
			return Comparer.GetHashCode(FullName);
		}

		/// <inheritdoc/>
		public int CompareTo(FileReference? other) => Comparer.Compare(FullName, other?.FullName);

		/// <summary>
		/// Helper function to create a remote file reference. Unlike normal FileReference objects, these aren't converted to a full path in the local filesystem, but are
		/// left as they are passed in.
		/// </summary>
		/// <param name="absolutePath">The absolute path in the remote file system</param>
		/// <returns>New file reference</returns>
		public static FileReference MakeRemote(string absolutePath)
		{
			return new FileReference(absolutePath, Sanitize.None);
		}

		/// <summary>
		/// Makes a file location writeable; 
		/// </summary>
		/// <param name="location">Location of the file</param>
		public static void MakeWriteable(FileReference location)
		{
			if(Exists(location))
			{
				FileAttributes attributes = GetAttributes(location);
				if((attributes & FileAttributes.ReadOnly) != 0)
				{
					SetAttributes(location, attributes & ~FileAttributes.ReadOnly);
				}
			}
		}

		/// <summary>
		/// Finds the correct case to match the location of this file on disk. Uses the given case for parts of the path that do not exist.
		/// </summary>
		/// <param name="location">The path to find the correct case for</param>
		/// <returns>Location of the file with the correct case</returns>
		public static FileReference FindCorrectCase(FileReference location)
		{
			return new FileReference(FileUtils.FindCorrectCase(location.ToFileInfo()));
		}

		/// <summary>
		/// Constructs a FileInfo object from this reference
		/// </summary>
		/// <returns>New FileInfo object</returns>
		public FileInfo ToFileInfo()
		{
			return new FileInfo(FullName);
		}

		#region System.IO.File methods

		/// <summary>
		/// Copies a file from one location to another
		/// </summary>
		/// <param name="sourceLocation">Location of the source file</param>
		/// <param name="targetLocation">Location of the target file</param>
		public static void Copy(FileReference sourceLocation, FileReference targetLocation)
		{
			File.Copy(sourceLocation.FullName, targetLocation.FullName);
		}

		/// <summary>
		/// Copies a file from one location to another
		/// </summary>
		/// <param name="sourceLocation">Location of the source file</param>
		/// <param name="targetLocation">Location of the target file</param>
		/// <param name="bOverwrite">Whether to overwrite the file in the target location</param>
		public static void Copy(FileReference sourceLocation, FileReference targetLocation, bool bOverwrite)
		{
			File.Copy(sourceLocation.FullName, targetLocation.FullName, bOverwrite);
		}

		/// <summary>
		/// Deletes this file
		/// </summary>
		public static void Delete(FileReference location)
		{
			File.Delete(location.FullName);
		}

		/// <summary>
		/// Determines whether the given filename exists
		/// </summary>
		/// <returns>True if it exists, false otherwise</returns>
		public static bool Exists(FileReference location)
		{
			return File.Exists(location.FullName);
		}

		/// <summary>
		/// Gets the attributes for a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Attributes for the file</returns>
		public static FileAttributes GetAttributes(FileReference location)
		{
			return File.GetAttributes(location.FullName);
		}

		/// <summary>
		/// Gets the time that the file was last written to
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Last write time, in local time</returns>
		public static DateTime GetLastWriteTime(FileReference location)
		{
			return File.GetLastWriteTime(location.FullName);
		}

		/// <summary>
		/// Gets the time that the file was last written to
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Last write time, in UTC time</returns>
		public static DateTime GetLastWriteTimeUtc(FileReference location)
		{
			return File.GetLastWriteTimeUtc(location.FullName);
		}

		/// <summary>
		/// Moves a file from one location to another
		/// </summary>
		/// <param name="sourceLocation">Location of the source file</param>
		/// <param name="targetLocation">Location of the target file</param>
		public static void Move(FileReference sourceLocation, FileReference targetLocation)
		{
			File.Move(sourceLocation.FullName, targetLocation.FullName);
		}

		/// <summary>
		/// Moves a file from one location to another
		/// </summary>
		/// <param name="sourceLocation">Location of the source file</param>
		/// <param name="targetLocation">Location of the target file</param>
		/// <param name="overwrite">Whether to overwrite the file in the target location</param>
		public static void Move(FileReference sourceLocation, FileReference targetLocation, bool overwrite)
		{
			File.Move(sourceLocation.FullName, targetLocation.FullName, overwrite);
		}

		/// <summary>
		/// Opens a FileStream on the specified path with read/write access
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="mode">Mode to use when opening the file</param>
		/// <returns>New filestream for the given file</returns>
		public static FileStream Open(FileReference location, FileMode mode)
		{
			return File.Open(location.FullName, mode);
		}

		/// <summary>
		/// Opens a FileStream on the specified path
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="mode">Mode to use when opening the file</param>
		/// <param name="access">Sharing mode for the new file</param>
		/// <returns>New filestream for the given file</returns>
		public static FileStream Open(FileReference location, FileMode mode, FileAccess access)
		{
			return File.Open(location.FullName, mode, access);
		}

		/// <summary>
		/// Opens a FileStream on the specified path
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="mode">Mode to use when opening the file</param>
		/// <param name="access">Access mode for the new file</param>
		/// <param name="share">Sharing mode for the open file</param>
		/// <returns>New filestream for the given file</returns>
		public static FileStream Open(FileReference location, FileMode mode, FileAccess access, FileShare share)
		{
			return File.Open(location.FullName, mode, access, share);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Byte array containing the contents of the file</returns>
		public static byte[] ReadAllBytes(FileReference location)
		{
			return File.ReadAllBytes(location.FullName);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Byte array containing the contents of the file</returns>
		public static Task<byte[]> ReadAllBytesAsync(FileReference location, CancellationToken cancellationToken = default)
		{
			return File.ReadAllBytesAsync(location.FullName, cancellationToken);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Contents of the file as a single string</returns>
		public static string ReadAllText(FileReference location)
		{
			using (FileStream fs = new FileStream(location.FullName, FileMode.Open, FileAccess.Read, FileShare.Read, 4 * 1024, FileOptions.SequentialScan))
			{
				using (StreamReader sr = new StreamReader(fs, Encoding.UTF8, true))
				{

					// Try to read the whole file into a buffer created by hand.  This avoids a LOT of memory allocations which in turn reduces the
					// GC stress on the system.  Removing the StreamReader would be nice in the future.
					long RawFileLength = fs.Length;
					char[] InitialBuffer = new char[RawFileLength];
					int ReadLength = sr.Read(InitialBuffer, 0, (int)RawFileLength);
					if (sr.EndOfStream)
					{
						return new String(InitialBuffer, 0, ReadLength);
					}
					else
					{
						string Remaining = sr.ReadToEnd();
						return String.Concat(new ReadOnlySpan<char>(InitialBuffer, 0, ReadLength), Remaining);
					}
				}
			}
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="encoding">Encoding of the file</param>
		/// <returns>Contents of the file as a single string</returns>
		public static string ReadAllText(FileReference location, Encoding encoding)
		{
			return File.ReadAllText(location.FullName, encoding);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>Contents of the file as a single string</returns>
		public static Task<string> ReadAllTextAsync(FileReference location, CancellationToken cancellationToken = default)
		{
			return File.ReadAllTextAsync(location.FullName, cancellationToken);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="encoding">Encoding of the file</param>
		/// <returns>Contents of the file as a single string</returns>
		public static Task<string> ReadAllTextAsync(FileReference location, Encoding encoding, CancellationToken cancellationToken = default)
		{
			return File.ReadAllTextAsync(location.FullName, encoding, cancellationToken);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>String array containing the contents of the file</returns>
		public static string[] ReadAllLines(FileReference location)
		{
			return File.ReadAllLines(location.FullName);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		/// <returns>String array containing the contents of the file</returns>
		public static string[] ReadAllLines(FileReference location, Encoding encoding)
		{
			return File.ReadAllLines(location.FullName, encoding);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <returns>String array containing the contents of the file</returns>
		public static Task<string[]> ReadAllLinesAsync(FileReference location, CancellationToken cancellationToken = default)
		{
			return File.ReadAllLinesAsync(location.FullName, cancellationToken);
		}

		/// <summary>
		/// Reads the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		/// <returns>String array containing the contents of the file</returns>
		public static Task<string[]> ReadAllLinesAsync(FileReference location, Encoding encoding, CancellationToken cancellationToken = default)
		{
			return File.ReadAllLinesAsync(location.FullName, encoding, cancellationToken);
		}

		/// <summary>
		/// Sets the attributes for a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="attributes">New attributes for the file</param>
		public static void SetAttributes(FileReference location, FileAttributes attributes)
		{
			File.SetAttributes(location.FullName, attributes);
		}

		/// <summary>
		/// Sets the time that the file was last written to
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="lastWriteTime">Last write time, in local time</param>
		public static void SetLastWriteTime(FileReference location, DateTime lastWriteTime)
		{
			File.SetLastWriteTime(location.FullName, lastWriteTime);
		}

		/// <summary>
		/// Sets the time that the file was last written to
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="lastWriteTimeUtc">Last write time, in UTC time</param>
		public static void SetLastWriteTimeUtc(FileReference location, DateTime lastWriteTimeUtc)
		{
			File.SetLastWriteTimeUtc(location.FullName, lastWriteTimeUtc);
		}

		/// <summary>
		/// Sets the time that the file was last accessed.
		/// </summary>
		/// <param name="location">Location of the file.</param>
		/// <param name="lastWriteTime">Last access time, in local time.</param>
		public static void SetLastAccessTime(FileReference location, DateTime lastWriteTime)
		{
			File.SetLastWriteTime(location.FullName, lastWriteTime);
		}

		/// <summary>
		/// Sets the time that the file was last accessed.
		/// </summary>
		/// <param name="location">Location of the file.</param>
		/// <param name="LastWriteTime">Last access time, in UTC time.</param>
		public static void SetLastAccessTimeUtc(FileReference location, DateTime lastWriteTimeUtc)
		{
			File.SetLastWriteTimeUtc(location.FullName, lastWriteTimeUtc);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static void WriteAllBytes(FileReference location, byte[] contents)
		{
			File.WriteAllBytes(location.FullName, contents);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static Task WriteAllBytesAsync(FileReference location, byte[] contents, CancellationToken cancellationToken = default)
		{
			return File.WriteAllBytesAsync(location.FullName, contents, cancellationToken);
		}

		/// <summary>
		/// Writes the data to the given file, if it's different from what's there already.
		/// Returns true if contents were written.
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static bool WriteAllBytesIfDifferent(FileReference location, byte[] contents)
		{
			if(FileReference.Exists(location))
			{
				byte[] currentContents = FileReference.ReadAllBytes(location);
				if(contents.AsSpan().SequenceEqual(currentContents))
				{
					return false;
				}
			}
			WriteAllBytes(location, contents);
			return true;
		}

		/// <summary>
		/// Writes the string to the given file, if it's different from what's there already.
		/// Returns true if contents were written.
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static bool WriteAllTextIfDifferent(FileReference location, string contents)
		{
			if(FileReference.Exists(location))
			{
				string currentContents = FileReference.ReadAllText(location);
				if (String.Equals(contents, currentContents))
				{
					return false;
				}
			}
			WriteAllText(location, contents);
			return true;
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static void WriteAllLines(FileReference location, IEnumerable<string> contents)
		{
			File.WriteAllLines(location.FullName, contents);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void WriteAllLines(FileReference location, IEnumerable<string> contents, Encoding encoding)
		{
			File.WriteAllLines(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static void WriteAllLines(FileReference location, string[] contents)
		{
			File.WriteAllLines(location.FullName, contents);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void WriteAllLines(FileReference location, string[] contents, Encoding encoding)
		{
			File.WriteAllLines(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static Task WriteAllLinesAsync(FileReference location, IEnumerable<string> contents, CancellationToken cancellationToken = default)
		{
			return File.WriteAllLinesAsync(location.FullName, contents, cancellationToken);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task WriteAllLinesAsync(FileReference location, IEnumerable<string> contents, Encoding encoding, CancellationToken cancellationToken = default)
		{
			return File.WriteAllLinesAsync(location.FullName, contents, encoding, cancellationToken);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static Task WriteAllLinesAsync(FileReference location, string[] contents, CancellationToken cancellationToken = default)
		{
			return File.WriteAllLinesAsync(location.FullName, contents, cancellationToken);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task WriteAllLinesAsync(FileReference location, string[] contents, Encoding encoding, CancellationToken cancellationToken = default)
		{
			return File.WriteAllLinesAsync(location.FullName, contents, encoding, cancellationToken);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static void WriteAllText(FileReference location, string contents)
		{
			File.WriteAllText(location.FullName, contents);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void WriteAllText(FileReference location, string contents, Encoding encoding)
		{
			File.WriteAllText(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		public static Task WriteAllTextAsync(FileReference location, string contents)
		{
			return File.WriteAllTextAsync(location.FullName, contents);
		}

		/// <summary>
		/// Writes the contents of a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents of the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task WriteAllTextAsync(FileReference location, string contents, Encoding encoding)
		{
			return File.WriteAllTextAsync(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static void AppendAllLines(FileReference location, IEnumerable<string> contents)
		{
			File.AppendAllLines(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static Task AppendAllLinesAsync(FileReference location, IEnumerable<string> contents)
		{
			return File.AppendAllLinesAsync(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void AppendAllLines(FileReference location, IEnumerable<string> contents, Encoding encoding)
		{
			File.AppendAllLines(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task AppendAllLinesAsync(FileReference location, IEnumerable<string> contents, Encoding encoding)
		{
			return File.AppendAllLinesAsync(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static void AppendAllLines(FileReference location, string[] contents)
		{
			File.AppendAllLines(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static Task AppendAllLinesAsync(FileReference location, string[] contents)
		{
			return File.AppendAllLinesAsync(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void AppendAllLines(FileReference location, string[] contents, Encoding encoding)
		{
			File.AppendAllLines(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task AppendAllLinesAsync(FileReference location, string[] contents, Encoding encoding)
		{
			return File.AppendAllLinesAsync(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static void AppendAllText(FileReference location, string contents)
		{
			File.AppendAllText(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		public static Task AppendAllTextAsync(FileReference location, string contents)
		{
			return File.AppendAllTextAsync(location.FullName, contents);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static void AppendAllText(FileReference location, string contents, Encoding encoding)
		{
			File.AppendAllText(location.FullName, contents, encoding);
		}

		/// <summary>
		/// Appends the contents to a file
		/// </summary>
		/// <param name="location">Location of the file</param>
		/// <param name="contents">Contents to append to the file</param>
		/// <param name="encoding">The encoding to use when parsing the file</param>
		public static Task AppendAllTextAsync(FileReference location, string contents, Encoding encoding)
		{
			return File.AppendAllTextAsync(location.FullName, contents, encoding);
		}

		#endregion
	}

	/// <summary>
	/// Extension methods for FileReference functionality
	/// </summary>
	public static class FileReferenceExtensionMethods
	{
		/// <summary>
		/// Manually serialize a file reference to a binary stream.
		/// </summary>
		/// <param name="writer">Binary writer to write to</param>
		/// <param name="file">The file reference to write</param>
		public static void Write(this BinaryWriter writer, FileReference file)
		{
			writer.Write((file == null) ? String.Empty : file.FullName);
		}

		/// <summary>
		/// Serializes a file reference, using a lookup table to avoid serializing the same name more than once.
		/// </summary>
		/// <param name="writer">The writer to save this reference to</param>
		/// <param name="file">A file reference to output; may be null</param>
		/// <param name="fileToUniqueId">A lookup table that caches previous files that have been output, and maps them to unique id's.</param>
		public static void Write(this BinaryWriter writer, FileReference file, Dictionary<FileReference, int> fileToUniqueId)
		{
			int uniqueId;
			if (file == null)
			{
				writer.Write(-1);
			}
			else if (fileToUniqueId.TryGetValue(file, out uniqueId))
			{
				writer.Write(uniqueId);
			}
			else
			{
				writer.Write(fileToUniqueId.Count);
				writer.Write(file);
				fileToUniqueId.Add(file, fileToUniqueId.Count);
			}
		}

		/// <summary>
		/// Manually deserialize a file reference from a binary stream.
		/// </summary>
		/// <param name="reader">Binary reader to read from</param>
		/// <returns>New FileReference object</returns>
		public static FileReference ReadFileReference(this BinaryReader reader)
		{
			return BinaryArchiveReader.NotNull(ReadFileReferenceOrNull(reader));
		}

		/// <summary>
		/// Manually deserialize a file reference from a binary stream.
		/// </summary>
		/// <param name="reader">Binary reader to read from</param>
		/// <returns>New FileReference object</returns>
		public static FileReference? ReadFileReferenceOrNull(this BinaryReader reader)
		{
			string fullName = reader.ReadString();
			return (fullName.Length == 0) ? null : new FileReference(fullName, FileReference.Sanitize.None);
		}

		/// <summary>
		/// Deserializes a file reference, using a lookup table to avoid writing the same name more than once.
		/// </summary>
		/// <param name="reader">The source to read from</param>
		/// <param name="uniqueFiles">List of previously read file references. The index into this array is used in place of subsequent ocurrences of the file.</param>
		/// <returns>The file reference that was read</returns>
		public static FileReference ReadFileReference(this BinaryReader reader, List<FileReference> uniqueFiles)
		{
			return BinaryArchiveReader.NotNull(ReadFileReferenceOrNull(reader, uniqueFiles));
		}

		/// <summary>
		/// Deserializes a file reference, using a lookup table to avoid writing the same name more than once.
		/// </summary>
		/// <param name="reader">The source to read from</param>
		/// <param name="uniqueFiles">List of previously read file references. The index into this array is used in place of subsequent ocurrences of the file.</param>
		/// <returns>The file reference that was read</returns>
		public static FileReference? ReadFileReferenceOrNull(this BinaryReader reader, List<FileReference> uniqueFiles)
		{
			int uniqueId = reader.ReadInt32();
			if (uniqueId == -1)
			{
				return null;
			}
			else if (uniqueId < uniqueFiles.Count)
			{
				return uniqueFiles[uniqueId];
			}
			else
			{
				FileReference result = reader.ReadFileReference();
				uniqueFiles.Add(result);
				return result;
			}
		}

		/// <summary>
		/// Writes a FileReference to a binary archive
		/// </summary>
		/// <param name="writer">The writer to output data to</param>
		/// <param name="file">The file reference to write</param>
		public static void WriteFileReference(this BinaryArchiveWriter writer, FileReference? file)
		{
			if(file == null)
			{
				writer.WriteString(null);
			}
			else
			{
				writer.WriteString(file.FullName);
			}
		}

		/// <summary>
		/// Reads a FileReference from a binary archive
		/// </summary>
		/// <param name="reader">Reader to serialize data from</param>
		/// <returns>New file reference instance</returns>
		public static FileReference ReadFileReference(this BinaryArchiveReader reader)
		{
			return BinaryArchiveReader.NotNull(ReadFileReferenceOrNull(reader));
		}

		/// <summary>
		/// Reads a FileReference from a binary archive
		/// </summary>
		/// <param name="reader">Reader to serialize data from</param>
		/// <returns>New file reference instance</returns>
		public static FileReference? ReadFileReferenceOrNull(this BinaryArchiveReader reader)
		{
			string? fullName = reader.ReadString();
			if(fullName == null)
			{
				return null;
			}
			else
			{
				return new FileReference(fullName, FileReference.Sanitize.None);
			}
		}
	}
}