using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using ReClassNET.AddressParser;
using ReClassNET.Symbols;
using ReClassNET.Util;

namespace ReClassNET.Memory
{
	public class RemoteProcess
	{
		private readonly NativeHelper nativeHelper;
		public NativeHelper NativeHelper => nativeHelper;

		private ProcessInfo process;
		public ProcessInfo Process
		{
			get { return process; }
			set { if (process != value) { process = value; rttiCache.Clear(); ProcessChanged?.Invoke(this); } }
		}

		public delegate void RemoteProcessChangedEvent(RemoteProcess sender);
		public event RemoteProcessChangedEvent ProcessChanged;

		private readonly Dictionary<IntPtr, string> rttiCache = new Dictionary<IntPtr, string>();

		public class Module
		{
			public IntPtr Start;
			public IntPtr End;
			public string Name;
			public string Path;
		}

		public enum SectionCategory
		{
			Unknown,
			Code,
			Data
		}

		public class Section
		{
			public IntPtr Start;
			public IntPtr End;
			public string Name;
			public SectionCategory Category;
			public NativeMethods.StateEnum State;
			public NativeMethods.AllocationProtectEnum Protection;
			public NativeMethods.TypeEnum Type;
			public string ModuleName;
			public string ModulePath;
		}

		private readonly List<Module> modules = new List<Module>();

		private readonly List<Section> sections = new List<Section>();

		private readonly SymbolStore symbols = new SymbolStore();
		public SymbolStore Symbols => symbols;

		public bool IsValid => process != null && nativeHelper.IsProcessValid(process.Handle);

		public RemoteProcess(NativeHelper nativeHelper)
		{
			Contract.Requires(nativeHelper != null);

			this.nativeHelper = nativeHelper;
		}

		#region ReadMemory

		/// <summary>Reads remote memory from the address into the buffer.</summary>
		/// <param name="address">The address to read from.</param>
		/// <param name="data">[out] The data buffer to fill. If the remote process is not valid, the buffer will get filled with zeros.</param>
		public void ReadRemoteMemoryIntoBuffer(IntPtr address, ref byte[] data)
		{
			Contract.Requires(data != null);

			if (!IsValid)
			{
				Process = null;

				data.FillWithZero();

				return;
			}

			nativeHelper.ReadRemoteMemory(Process.Handle, address, data, (uint)data.Length);
		}

		/// <summary>Reads <paramref name="size"/> bytes from the address in the remote process.</summary>
		/// <param name="address">The address to read from.</param>
		/// <param name="size">The size in bytes to read.</param>
		/// <returns>An array of bytes.</returns>
		public byte[] ReadRemoteMemory(IntPtr address, int size)
		{
			Contract.Requires(size >= 0);
			Contract.Ensures(Contract.Result<byte[]>() != null);

			var data = new byte[size];
			ReadRemoteMemoryIntoBuffer(address, ref data);
			return data;
		}

		/// <summary>Reads the object from the address in the remote process.</summary>
		/// <typeparam name="T">Type of the value to read.</typeparam>
		/// <param name="address">The address to read from.</param>
		/// <returns>The remote object.</returns>
		public T ReadRemoteObject<T>(IntPtr address) where T : struct
		{
			var data = ReadRemoteMemory(address, Marshal.SizeOf<T>());

			var handle = GCHandle.Alloc(data, GCHandleType.Pinned);
			var obj = (T)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(T));
			handle.Free();

			return obj;
		}

		/// <summary>Reads a string from the address in the remote process with the given length using the provided encoding.</summary>
		/// <param name="encoding">The encoding used by the string.</param>
		/// <param name="address">The address of the string.</param>
		/// <param name="length">The length of the string.</param>
		/// <returns>The string.</returns>
		public string ReadRemoteString(Encoding encoding, IntPtr address, int length)
		{
			Contract.Requires(encoding != null);
			Contract.Requires(length >= 0);
			Contract.Ensures(Contract.Result<string>() != null);

			var data = ReadRemoteMemory(address, length);

			try
			{
				var sb = new StringBuilder(encoding.GetString(data));
				for (var i = 0; i < sb.Length; ++i)
				{
					if (sb[i] == 0)
					{
						sb.Length = i;
						break;
					}
					if (!sb[i].IsPrintable())
					{
						sb[i] = '.';
					}
				}
				return sb.ToString();
			}
			catch
			{
				return string.Empty;
			}
		}

		/// <summary>Reads a string from the address in the remote process with the given length using UTF8 encoding. The string gets truncated at the first zero character.</summary>
		/// <param name="address">The address of the string.</param>
		/// <param name="length">The length of the string.</param>
		/// <returns>The string.</returns>
		public string ReadRemoteUTF8StringUntilFirstNullCharacter(IntPtr address, int length)
		{
			Contract.Requires(length >= 0);

			var data = ReadRemoteMemory(address, length);

			int index = 0;
			for (; index < data.Length; ++index)
			{
				if (data[index] == 0)
				{
					break;
				}
			}

			try
			{
				return Encoding.UTF8.GetString(data, 0, Math.Min(index, data.Length));
			}
			catch
			{
				return string.Empty;
			}
		}

		/// <summary>Reads remote runtime type information for the given address from the remote process.</summary>
		/// <param name="address">The address.</param>
		/// <returns>A string containing the runtime type information or null if no information could get found.</returns>
		public string ReadRemoteRuntimeTypeInformation(IntPtr address)
		{
			if (address.MayBeValid())
			{
				string rtti = null;
				if (!rttiCache.TryGetValue(address, out rtti))
				{
					var objectLocatorPtr = ReadRemoteObject<IntPtr>(address - IntPtr.Size);
					if (objectLocatorPtr.MayBeValid())
					{
					
#if WIN64
						rtti = ReadRemoteRuntimeTypeInformation64(objectLocatorPtr);
#else
						rtti = ReadRemoteRuntimeTypeInformation32(objectLocatorPtr);
#endif

						rttiCache[address] = rtti;
					}
				}
				return rtti;
			}

			return null;
		}

		private string ReadRemoteRuntimeTypeInformation32(IntPtr address)
		{
			var classHierarchyDescriptorPtr = ReadRemoteObject<IntPtr>(address + 0x10);
			if (classHierarchyDescriptorPtr.MayBeValid())
			{
				var baseClassCount = ReadRemoteObject<int>(classHierarchyDescriptorPtr + 8);
				if (baseClassCount > 0 && baseClassCount < 25)
				{
					var baseClassArrayPtr = ReadRemoteObject<IntPtr>(classHierarchyDescriptorPtr + 0xC);
					if (baseClassArrayPtr.MayBeValid())
					{
						var sb = new StringBuilder();
						for (var i = 0; i < baseClassCount; ++i)
						{
							var baseClassDescriptorPtr = ReadRemoteObject<IntPtr>(baseClassArrayPtr + (4 * i));
							if (baseClassDescriptorPtr.MayBeValid())
							{
								var typeDescriptorPtr = ReadRemoteObject<IntPtr>(baseClassDescriptorPtr);
								if (typeDescriptorPtr.MayBeValid())
								{
									var name = ReadRemoteUTF8StringUntilFirstNullCharacter(typeDescriptorPtr + 0x0C, 60);
									if (name.EndsWith("@@"))
									{
										name = NativeMethods.UnDecorateSymbolName("?" + name);
									}

									sb.Append(name);
									sb.Append(" : ");

									continue;
								}
							}

							break;
						}

						if (sb.Length != 0)
						{
							sb.Length -= 3;

							return sb.ToString();
						}
					}
				}
			}

			return null;
		}

		private string ReadRemoteRuntimeTypeInformation64(IntPtr address)
		{
			int baseOffset = ReadRemoteObject<int>(address + 0x14);
			if (baseOffset != 0)
			{
				var baseAddress = address - baseOffset;

				var classHierarchyDescriptorOffset = ReadRemoteObject<int>(address + 0x10);
				if (classHierarchyDescriptorOffset != 0)
				{
					var classHierarchyDescriptorPtr = baseAddress + classHierarchyDescriptorOffset;

					var baseClassCount = ReadRemoteObject<int>(classHierarchyDescriptorPtr + 0x08);
					if (baseClassCount > 0 && baseClassCount < 25)
					{
						var baseClassArrayOffset = ReadRemoteObject<int>(classHierarchyDescriptorPtr + 0x0C);
						if (baseClassArrayOffset != 0)
						{
							var baseClassArrayPtr = baseAddress + baseClassArrayOffset;

							var sb = new StringBuilder();
							for (var i = 0; i < baseClassCount; ++i)
							{
								var baseClassDescriptorOffset = ReadRemoteObject<int>(baseClassArrayPtr + (4 * i));
								if (baseClassDescriptorOffset != 0)
								{
									var baseClassDescriptorPtr = baseAddress + baseClassDescriptorOffset;

									var typeDescriptorOffset = ReadRemoteObject<int>(baseClassDescriptorPtr);
									if (typeDescriptorOffset != 0)
									{
										var typeDescriptorPtr = baseAddress + typeDescriptorOffset;

										var name = ReadRemoteUTF8StringUntilFirstNullCharacter(typeDescriptorPtr + 0x14, 60);
										if (string.IsNullOrEmpty(name))
										{
											break;
										}

										if (name.EndsWith("@@"))
										{
											name = NativeMethods.UnDecorateSymbolName("?" + name);
										}

										sb.Append(name);
										sb.Append(" : ");

										continue;
									}
								}

								break;
							}

							if (sb.Length != 0)
							{
								sb.Length -= 3;

								return sb.ToString();
							}
						}
					}
				}
			}

			return null;
		}

		#endregion

		#region WriteMemory

		/// <summary>Writes the given <paramref name="data"/> to the <paramref name="address"/> in the remote process.</summary>
		/// <param name="address">The address to write to.</param>
		/// <param name="data">The data to write.</param>
		/// <returns>True if it succeeds, false if it fails.</returns>
		public bool WriteRemoteMemory(IntPtr address, byte[] data)
		{
			Contract.Requires(data != null);

			if (!IsValid)
			{
				return false;
			}

			return nativeHelper.WriteRemoteMemory(Process.Handle, address, data, (uint)data.Length);
		}

		/// <summary>Writes the given <paramref name="value"/> to the <paramref name="address"/> in the remote process.</summary>
		/// <typeparam name="T">Type of the value to write.</typeparam>
		/// <param name="address">The address to write to.</param>
		/// <param name="value">The value to write.</param>
		/// <returns>True if it succeeds, false if it fails.</returns>
		public bool WriteRemoteMemory<T>(IntPtr address, T value) where T : struct
		{
			var data = new byte[Marshal.SizeOf<T>()];

			var handle = GCHandle.Alloc(data, GCHandleType.Pinned);
			Marshal.StructureToPtr(value, handle.AddrOfPinnedObject(), false);
			handle.Free();

			return WriteRemoteMemory(address, data);
		}

		#endregion

		public Section GetSectionToPointer(IntPtr address)
		{
			lock (sections)
			{
				return sections
					.Where(s => s.Category != SectionCategory.Unknown)
					.Where(s => address.InRange(s.Start, s.End))
					.FirstOrDefault();
			}
		}

		public Module GetModuleToPointer(IntPtr address)
		{
			lock (modules)
			{
				return modules
					.Where(m => address.InRange(m.Start, m.End))
					.FirstOrDefault();
			}
		}

		public Module GetModuleByName(string name)
		{
			lock (modules)
			{
				return modules
					.Where(m => m.Name.Equals(name, StringComparison.InvariantCultureIgnoreCase))
					.FirstOrDefault();
			}
		}

		/// <summary>Tries to map the given address to a section or a module of the process.</summary>
		/// <param name="address">The address to map.</param>
		/// <returns>The named address or null if no mapping exists.</returns>
		public string GetNamedAddress(IntPtr address)
		{
			var section = GetSectionToPointer(address);
			if (section != null)
			{
				return $"<{section.Category}>{section.ModuleName}.{address.ToString("X")}";
			}
			var module = GetModuleToPointer(address);
			if (module != null)
			{
				return $"{module.Name}.{address.ToString("X")}";
			}
			return null;
		}

		/// <summary>Updates the process informations.</summary>
		public void UpdateProcessInformations()
		{
			UpdateProcessInformationsAsync().Wait();
		}

		/// <summary>Updates the process informations asynchronous.</summary>
		/// <returns>The Task.</returns>
		public Task UpdateProcessInformationsAsync()
		{
			if (!IsValid)
			{
				lock(modules)
				{
					modules.Clear();
				}
				lock(sections)
				{
					sections.Clear();
				}

				return Task.CompletedTask;
			}

			return Task.Run(() =>
			{
				var newModules = new List<Module>();
				var newSections = new List<Section>();

				nativeHelper.EnumerateRemoteSectionsAndModules(
					process.Handle,
					delegate (IntPtr baseAddress, IntPtr regionSize, string name, NativeMethods.StateEnum state, NativeMethods.AllocationProtectEnum protection, NativeMethods.TypeEnum type, string modulePath)
					{
						var section = new Section
						{
							Start = baseAddress,
							End = baseAddress.Add(regionSize),
							Name = name,
							State = state,
							Protection = protection,
							Type = type,
							ModulePath = modulePath,
							ModuleName = Path.GetFileName(modulePath)
						};
						switch (section.Name)
						{
							case ".text":
							case "code":
								section.Category = SectionCategory.Code;
								break;
							case ".data":
							case "data":
							case ".rdata":
							case ".idata":
								section.Category = SectionCategory.Data;
								break;
						}
						newSections.Add(section);
					},
					delegate (IntPtr baseAddress, IntPtr regionSize, string modulePath)
					{
						newModules.Add(new Module
						{
							Start = baseAddress,
							End = baseAddress.Add(regionSize),
							Path = modulePath,
							Name = Path.GetFileName(modulePath)
						});
					}
				);

				lock (modules)
				{
					modules.Clear();
					modules.AddRange(newModules);
				}
				lock (sections)
				{
					sections.Clear();
					sections.AddRange(newSections);
				}
			});
		}

		/// <summary>Parse the address formula.</summary>
		/// <param name="addressFormula">The address formula.</param>
		/// <returns>The result of the parsed address or <see cref="IntPtr.Zero"/>.</returns>
		public IntPtr ParseAddress(string addressFormula)
		{
			Contract.Requires(addressFormula != null);

			var reader = new TokenReader();
			var tokens = reader.Read(addressFormula);

			var astBuilder = new AstBuilder();
			var operation = astBuilder.Build(tokens);

			if (operation == null)
			{
				return IntPtr.Zero;
			}

			var interpreter = new Interpreter();
			return interpreter.Execute(operation, this);
		}

		/// <summary>Loads all symbols asynchronous.</summary>
		/// <param name="progress">The progress reporter is called for every module. Can be null.</param>
		/// <param name="token">The token used to cancel the task.</param>
		/// <returns>The task.</returns>
		public Task LoadAllSymbolsAsync(IProgress<Tuple<Module, IEnumerable<Module>>> progress, CancellationToken token)
		{
			var copy = modules.ToList();

			// Try to resolve all symbols in a background thread. This can take a long time because symbols are downloaded from the internet.
			// The COM objects can only be used in the thread they were created so we can't use them.
			// Thats why an other task loads the real symbols afterwards in the UI thread context.
			return Task.Run(
				() =>
				{
					foreach (var module in copy)
					{
						token.ThrowIfCancellationRequested();

						progress?.Report(Tuple.Create<Module, IEnumerable<Module>>(module, copy));

						Symbols.TryResolveSymbolsForModule(module);
					}
				},
				token
			)
			.ContinueWith(
				_ =>
				{
					foreach (var module in copy)
					{
						token.ThrowIfCancellationRequested();

						try
						{
							Symbols.LoadSymbolsForModule(module);
						}
						catch
						{
							//ignore
						}
					}
				},
				token,
				TaskContinuationOptions.None,
				TaskScheduler.FromCurrentSynchronizationContext()
			);
		}
	}
}