using System;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Text;
using System.Reflection;
using NUnit.Framework;

#if NET_CORE
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Emit;
using CS = Microsoft.CodeAnalysis.CSharp;
#endif

namespace Mono.Cecil.Tests {

	struct CompilationResult {
		internal DateTime source_write_time;
		internal string result_file;

		public CompilationResult (DateTime write_time, string result_file)
		{
			this.source_write_time = write_time;
			this.result_file = result_file;
		}
	}

	public static class Platform {

		public static bool OnMono {
			get { return TryGetType ("Mono.Runtime") != null; }
		}

		public static bool OnCoreClr {
			get { return TryGetType ("System.Runtime.Loader.AssemblyLoadContext, System.Runtime.Loader, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a") != null; }
		}

		public static bool OnWindows {
			get { return Environment.OSVersion.Platform == PlatformID.Win32NT; }
		}

		public static bool HasNativePdbSupport {
			get { return OnWindows && !OnMono; }
		}

		static Type TryGetType (string assemblyQualifiedName)
		{
			try {
				// Note that throwOnError=false only suppresses some exceptions, not all.
				return Type.GetType(assemblyQualifiedName, throwOnError: false);
			} catch {
				return null;
			}
		}
	}

	abstract class CompilationService {

		Dictionary<string, CompilationResult> files = new Dictionary<string, CompilationResult> ();

		bool TryGetResult (string name, out string file_result)
		{
			file_result = null;
			CompilationResult result;
			if (!files.TryGetValue (name, out result))
				return false;

			if (result.source_write_time != File.GetLastWriteTime (name))
				return false;

			file_result = result.result_file;
			return true;
		}

		public string Compile (string name)
		{
			string result_file;
			if (TryGetResult (name, out result_file))
				return result_file;

			result_file = CompileFile (name);
			RegisterFile (name, result_file);
			return result_file;
		}

		void RegisterFile (string name, string result_file)
		{
			files [name] = new CompilationResult (File.GetLastWriteTime (name), result_file);
		}

		protected abstract string CompileFile (string name);

		public static string CompileResource (string name)
		{
			var extension = Path.GetExtension (name);
			if (extension == ".il")
				return IlasmCompilationService.Instance.Compile (name);

			if (extension == ".cs")
#if NET_CORE
				return RoslynCompilationService.Instance.Compile (name);
#else
				return CodeDomCompilationService.Instance.Compile (name);
#endif
			throw new NotSupportedException (extension);
		}

		protected static string GetCompiledFilePath (string file_name)
		{
			var tmp_cecil = Path.Combine (Path.GetTempPath (), "cecil");
			if (!Directory.Exists (tmp_cecil))
				Directory.CreateDirectory (tmp_cecil);

			return Path.Combine (tmp_cecil, Path.GetFileName (file_name) + ".dll");
		}

		public static void Verify (string name)
		{
#if !NET_CORE
			var output = Platform.OnMono ? ShellService.PEDump (name) : ShellService.PEVerify (name);
			if (output.ExitCode != 0)
				Assert.Fail (output.ToString ());
#endif
		}
	}

	class IlasmCompilationService : CompilationService {

		public static readonly IlasmCompilationService Instance = new IlasmCompilationService ();

		protected override string CompileFile (string name)
		{
			string file = GetCompiledFilePath (name);

			var output = ShellService.ILAsm (name, file);

			AssertAssemblerResult (output);

			return file;
		}

		static void AssertAssemblerResult (ShellService.ProcessOutput output)
		{
			if (output.ExitCode != 0)
				Assert.Fail (output.ToString ());
		}
	}

#if NET_CORE

	class RoslynCompilationService : CompilationService {

		public static readonly RoslynCompilationService Instance = new RoslynCompilationService ();

		protected override string CompileFile (string name)
		{
			var compilation = GetCompilation (name);
			var outputName = GetCompiledFilePath (name);

			var result = compilation.Emit (outputName);
			Assert.IsTrue (result.Success, GetErrorMessage (result));

			return outputName;
		}

		static Compilation GetCompilation (string name)
		{
			var assemblyName = Path.GetFileNameWithoutExtension (name);
			var source = File.ReadAllText (name);

			var tpa = BaseAssemblyResolver.TrustedPlatformAssemblies.Value;
			
			var references = new [] 
			{
				MetadataReference.CreateFromFile (tpa ["netstandard"]),
				MetadataReference.CreateFromFile (tpa ["mscorlib"]),
				MetadataReference.CreateFromFile (tpa ["System.Private.CoreLib"]),
				MetadataReference.CreateFromFile (tpa ["System.Runtime"]),
				MetadataReference.CreateFromFile (tpa ["System.Console"]),
				MetadataReference.CreateFromFile (tpa ["System.Security.AccessControl"]),
			};

			var extension = Path.GetExtension (name);
			switch (extension) {
			case ".cs":
				return CS.CSharpCompilation.Create (
					assemblyName, 
					new [] { CS.SyntaxFactory.ParseSyntaxTree (source) },
					references, 
					new CS.CSharpCompilationOptions (OutputKind.DynamicallyLinkedLibrary, optimizationLevel: OptimizationLevel.Release));
			default:
				throw new NotSupportedException ();
			}
		}

		static string GetErrorMessage (EmitResult result)
		{
			if (result.Success)
				return string.Empty;

			var builder = new StringBuilder ();
			foreach (var diagnostic in result.Diagnostics)
				builder.AppendLine (diagnostic.ToString ());

			return builder.ToString ();
		}
	}

#else

	class CodeDomCompilationService : CompilationService {

		public static readonly CodeDomCompilationService Instance = new CodeDomCompilationService ();

		protected override string CompileFile (string name)
		{
			string file = GetCompiledFilePath (name);

			using (var provider = GetProvider (name)) {
				var parameters = GetDefaultParameters (name);
				parameters.IncludeDebugInformation = false;
				parameters.GenerateExecutable = false;
				parameters.OutputAssembly = file;

				var results = provider.CompileAssemblyFromFile (parameters, name);
				AssertCompilerResults (results);
			}

			return file;
		}

		static void AssertCompilerResults (CompilerResults results)
		{
			Assert.IsFalse (results.Errors.HasErrors, GetErrorMessage (results));
		}

		static string GetErrorMessage (CompilerResults results)
		{
			if (!results.Errors.HasErrors)
				return string.Empty;

			var builder = new StringBuilder ();
			foreach (CompilerError error in results.Errors)
				builder.AppendLine (error.ToString ());
			return builder.ToString ();
		}

		static CompilerParameters GetDefaultParameters (string name)
		{
			return GetCompilerInfo (name).CreateDefaultCompilerParameters ();
		}

		static CodeDomProvider GetProvider (string name)
		{
			return GetCompilerInfo (name).CreateProvider ();
		}

		static CompilerInfo GetCompilerInfo (string name)
		{
			return CodeDomProvider.GetCompilerInfo (
				CodeDomProvider.GetLanguageFromExtension (Path.GetExtension (name)));
		}
	}

#endif

	class ShellService {

		public class ProcessOutput {

			public int ExitCode;
			public string StdOut;
			public string StdErr;

			public ProcessOutput (int exitCode, string stdout, string stderr)
			{
				ExitCode = exitCode;
				StdOut = stdout;
				StdErr = stderr;
			}

			public override string ToString ()
			{
				return StdOut + StdErr;
			}
		}

		static ProcessOutput RunProcess (string target, params string [] arguments)
		{
			var stdout = new StringWriter ();
			var stderr = new StringWriter ();

			var process = new Process {
				StartInfo = new ProcessStartInfo {
					FileName = target,
					Arguments = string.Join (" ", arguments),
					CreateNoWindow = true,
					UseShellExecute = false,
					RedirectStandardError = true,
					RedirectStandardInput = true,
					RedirectStandardOutput = true,
				},
			};

			process.Start ();

			process.OutputDataReceived += (_, args) => stdout.Write (args.Data);
			process.ErrorDataReceived += (_, args) => stderr.Write (args.Data);

			process.BeginOutputReadLine ();
			process.BeginErrorReadLine ();

			process.WaitForExit ();

			return new ProcessOutput (process.ExitCode, stdout.ToString (), stderr.ToString ());
		}

		public static ProcessOutput ILAsm (string source, string output)
		{
			var ilasm = "ilasm";
			if (Platform.OnWindows)
				ilasm = NetFrameworkTool ("ilasm");

			return RunProcess (ilasm, "/nologo", "/dll", "/out:" + Quote (output), Quote (source));
		}

		static string Quote (string file)
		{
			return "\"" + file + "\"";
		}

		public static ProcessOutput PEVerify (string source)
		{
			return RunProcess (WinSdkTool ("peverify"), "/nologo", Quote (source));
		}

		public static ProcessOutput PEDump (string source)
		{
			return RunProcess ("pedump", "--verify code,metadata", Quote (source));
		}

		static string NetFrameworkTool (string tool)
		{
#if NET_CORE
			return Path.Combine (Environment.GetFolderPath (Environment.SpecialFolder.Windows), "Microsoft.NET", "Framework", "v4.0.30319", tool + ".exe");
#else
			return Path.Combine (
				Path.GetDirectoryName (typeof (object).Assembly.Location),
				tool + ".exe");
#endif
		}

		static string WinSdkTool (string tool)
		{
			var sdks = new [] {
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.2 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.1 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.2 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools",
				@"Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6 Tools",
				@"Microsoft SDKs\Windows\v8.1A\bin\NETFX 4.5.1 Tools",
				@"Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools",
				@"Microsoft SDKs\Windows\v7.0A\Bin",
			};

			foreach (var sdk in sdks) {
				var pgf = IntPtr.Size == 8
					? Environment.GetEnvironmentVariable("ProgramFiles(x86)")
					: Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles);

				var exe = Path.Combine (
					Path.Combine (pgf, sdk),
					tool + ".exe");

				if (File.Exists(exe))
					return exe;
			}

			return tool;
		}
	}
}