using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using ICSharpCode.Decompiler.TypeSystem.Implementation;
using Mono.Cecil;

namespace ICSharpCode.Decompiler
{
	public static class DotNetCorePathFinderExtensions
	{
		static readonly string RefPathPattern =
			@"(Reference Assemblies[/\\]Microsoft[/\\]Framework[/\\](?<1>.NETFramework)[/\\]v(?<2>[^/\\]+)[/\\])" +
			@"|(NuGetFallbackFolder[/\\](?<1>[^/\\]+)\\(?<2>[^/\\]+)([/\\].*)?[/\\]ref[/\\])";

		public static string DetectTargetFrameworkId(this AssemblyDefinition assembly, string assemblyPath = null)
		{
			if (assembly == null)
				throw new ArgumentNullException(nameof(assembly));

			const string TargetFrameworkAttributeName = "System.Runtime.Versioning.TargetFrameworkAttribute";

			foreach (var attribute in assembly.CustomAttributes) {
				if (attribute.AttributeType.FullName != TargetFrameworkAttributeName)
					continue;
				var blobReader = new BlobReader(attribute.GetBlob(), null);
				if (blobReader.ReadUInt16() == 0x0001) {
					return blobReader.ReadSerString();
				}
			}

			// Optionally try to detect target version through assembly path as a fallback (use case: reference assemblies)
			if (assemblyPath != null) {
				/*
				 * Detected path patterns (examples):
				 * 
				 * - .NETFramework -> C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\mscorlib.dll
				 * - .NETCore      -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.netcore.app\2.1.0\ref\netcoreapp2.1\System.Console.dll
				 * - .NETStandard  -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\netstandard.library\2.0.3\build\netstandard2.0\ref\netstandard.dll
				 */
				var pathMatch = Regex.Match(assemblyPath, RefPathPattern, 
					RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.ExplicitCapture);
				if (pathMatch.Success) {
					var type = pathMatch.Groups[1].Value;
					var version = pathMatch.Groups[2].Value;

					if (type == ".NETFramework") {
						return $".NETFramework,Version=v{version}";
					} else if (type.Contains("netcore")) {
						return $".NETCoreApp,Version=v{version}";
					} else if (type.Contains("netstandard")) {
						return $".NETStandard,Version=v{version}";
					}
				}
			}

			return string.Empty;
		}
	}

	public class ReferenceLoadInfo
	{
		readonly Dictionary<string, UnresolvedAssemblyNameReference> loadedAssemblyReferences = new Dictionary<string, UnresolvedAssemblyNameReference>();

		public void AddMessage(string fullName, MessageKind kind, string message)
		{
			lock (loadedAssemblyReferences) {
				if (!loadedAssemblyReferences.TryGetValue(fullName, out var referenceInfo)) {
					referenceInfo = new UnresolvedAssemblyNameReference(fullName);
					loadedAssemblyReferences.Add(fullName, referenceInfo);
				}
				referenceInfo.Messages.Add((kind, message));
			}
		}

		public void AddMessageOnce(string fullName, MessageKind kind, string message)
		{
			lock (loadedAssemblyReferences) {
				if (!loadedAssemblyReferences.TryGetValue(fullName, out var referenceInfo)) {
					referenceInfo = new UnresolvedAssemblyNameReference(fullName);
					loadedAssemblyReferences.Add(fullName, referenceInfo);
					referenceInfo.Messages.Add((kind, message));
				} else {
					var lastMsg = referenceInfo.Messages.LastOrDefault();
					if (kind != lastMsg.Item1 && message != lastMsg.Item2)
						referenceInfo.Messages.Add((kind, message));
				}
			}
		}

		public bool TryGetInfo(string fullName, out UnresolvedAssemblyNameReference info)
		{
			lock (loadedAssemblyReferences) {
				return loadedAssemblyReferences.TryGetValue(fullName, out info);
			}
		}

		public bool HasErrors {
			get {
				lock (loadedAssemblyReferences) {
					return loadedAssemblyReferences.Any(i => i.Value.HasErrors);
				}
			}
		}
	}
}