// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

using ICSharpCode.Core;
using ICSharpCode.SharpDevelop.Dom;
using Mono.Cecil;

namespace ICSharpCode.ILSpyAddIn.LaunchILSpy
{
	class ILSpyAssemblyResolver : IAssemblyResolver
	{
		readonly DirectoryInfo directoryInfo;
		readonly IDictionary<string, AssemblyDefinition> cache;
		readonly IDictionary<string, AssemblyDefinition> localAssembliesCache;
		
		public ILSpyAssemblyResolver(string decompiledAssemblyFolder)
		{
			if (string.IsNullOrEmpty(decompiledAssemblyFolder))
				throw new ArgumentException("Invalid working folder");
			
			FolderPath = decompiledAssemblyFolder;
			this.directoryInfo = new DirectoryInfo(decompiledAssemblyFolder);
			this.cache = new Dictionary<string, AssemblyDefinition> ();
			this.localAssembliesCache = new Dictionary<string, AssemblyDefinition>();
			
			ReadLocalAssemblies();
		}
		
		public string FolderPath {
			get; private set;
		}
		
		public AssemblyDefinition Resolve(AssemblyNameReference name)
		{
			return this.Resolve(name, new ReaderParameters());
		}
		
		public AssemblyDefinition Resolve(AssemblyNameReference name, ReaderParameters parameters)
		{
			if (name == null)
				throw new ArgumentNullException("name");
			
			if (parameters == null)
				throw new ArgumentNullException("parameters");
			
			try {
				AssemblyDefinition assembly = null;
				if (cache.TryGetValue(name.FullName, out assembly))
					return assembly;

				// search into assemblyDecompiledFolder
				if (localAssembliesCache.ContainsKey(name.FullName)) {
					assembly = localAssembliesCache[name.FullName];
				}
				
				if (assembly == null) {
					// search using ILSpy's GacInterop.FindAssemblyInNetGac()
					string fileInGac = FindAssemblyInNetGac(name);
					if (!string.IsNullOrEmpty(fileInGac)) {
						assembly = AssemblyDefinition.ReadAssembly(fileInGac, parameters);
					}
				}
				
				// update caches
				if (assembly != null) {
					this.cache.Add(assembly.FullName, assembly);
				}
				return assembly;
			} catch (Exception ex) {
				LoggingService.Error("Exception (ILSpyAssemblyResolver): " + ex.Message);
				return null;
			}
		}
		
		public AssemblyDefinition Resolve(string fullName)
		{
			return this.Resolve(fullName, new ReaderParameters());
		}
		
		public AssemblyDefinition Resolve(string fullName, ReaderParameters parameters)
		{
			if (string.IsNullOrEmpty(fullName))
				throw new ArgumentException("fullName is null or empty");

			return Resolve(AssemblyNameReference.Parse(fullName), parameters);
		}
		
		void ReadLocalAssemblies()
		{
			// read local assemblies
			foreach (var file in this.directoryInfo.GetFiles()) {
				try {
					var localAssembly = AssemblyDefinition.ReadAssembly(file.FullName);
					localAssembliesCache.Add(localAssembly.FullName, localAssembly);
				} catch {
					// unable to read assembly file
				}
			}
		}
		
		#region FindAssemblyInGac
		// This region is based on code from Mono.Cecil:
		
		// Author:
		//   Jb Evain (jbevain@gmail.com)
		//
		// Copyright (c) 2008 - 2010 Jb Evain
		//
		// Permission is hereby granted, free of charge, to any person obtaining
		// a copy of this software and associated documentation files (the
		// "Software"), to deal in the Software without restriction, including
		// without limitation the rights to use, copy, modify, merge, publish,
		// distribute, sublicense, and/or sell copies of the Software, and to
		// permit persons to whom the Software is furnished to do so, subject to
		// the following conditions:
		//
		// The above copyright notice and this permission notice shall be
		// included in all copies or substantial portions of the Software.
		//
		// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
		// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
		// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
		// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
		// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
		// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
		// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
		//

		static readonly string[] gac_paths = { GacInterop.GacRootPathV2, GacInterop.GacRootPathV4 };
		static readonly string[] gacs = { "GAC_MSIL", "GAC_32", "GAC" };
		static readonly string[] prefixes = { string.Empty, "v4.0_" };
		
		/// <summary>
		/// Gets the file name for an assembly stored in the GAC.
		/// </summary>
		public static string FindAssemblyInNetGac (AssemblyNameReference reference)
		{
			// without public key, it can't be in the GAC
			if (reference.PublicKeyToken == null)
				return null;
			
			for (int i = 0; i < 2; i++) {
				for (int j = 0; j < gacs.Length; j++) {
					var gac = Path.Combine (gac_paths [i], gacs [j]);
					var file = GetAssemblyFile (reference, prefixes [i], gac);
					if (File.Exists (file))
						return file;
				}
			}

			return null;
		}
		
		static string GetAssemblyFile (AssemblyNameReference reference, string prefix, string gac)
		{
			var gac_folder = new StringBuilder ()
				.Append (prefix)
				.Append (reference.Version)
				.Append ("__");

			for (int i = 0; i < reference.PublicKeyToken.Length; i++)
				gac_folder.Append (reference.PublicKeyToken [i].ToString ("x2"));

			return Path.Combine (
				Path.Combine (
					Path.Combine (gac, reference.Name), gac_folder.ToString ()),
				reference.Name + ".dll");
		}
		#endregion
	}
}