using System;
using System.Collections.Generic;
using System.IO;
using CecilTool;
using Mono.Cecil;

namespace CecilTool
{
    /// <summary>
    /// Simple tool using Mono.Cecil to dump the list of usage of internals methods/fields
    /// referencing another assembly from a specified assembly.
    ///
    /// Usage: ApiVerifier.DumpUsageOfInternalsFromExternalAssemblies(@"C:\Path\To\My\Assembly.dll")
    ///
    /// </summary>
    public static class ApiVerifier
    {
        public static void DumpUsageOfInternalsFromExternalAssemblies(string assemblyPath)
        {
            if (assemblyPath == null) throw new ArgumentNullException(nameof(assemblyPath));
            DumpUsageOfInternalsFromExternalAssemblies(new List<string>() {assemblyPath});
        }

        public static void DumpUsageOfInternalsFromExternalAssemblies(List<string> assemblyPaths)
        {
            if (assemblyPaths == null) throw new ArgumentNullException(nameof(assemblyPaths));
            var assemblyFullPaths = new List<string>();
            var assemblyResolver = new DefaultAssemblyResolver();
            foreach (var assemblyPath in assemblyPaths)
            {
                var fullPath = Path.Combine(Environment.CurrentDirectory, assemblyPath);
                assemblyFullPaths.Add(fullPath);
                assemblyResolver.AddSearchDirectory(Path.GetDirectoryName(fullPath));
            }

            for (var i = 0; i < assemblyFullPaths.Count; i++)
            {
                var fullPath = assemblyFullPaths[i];
                var assembly = AssemblyDefinition.ReadAssembly(fullPath, new ReaderParameters(ReadingMode.Immediate)
                {
                    AssemblyResolver = assemblyResolver
                });
                if (i > 0) Console.WriteLine();
                DumpUsageOfInternalsFromExternalAssemblies(assembly);
            }
        }

        public static void DumpUsageOfInternalsFromExternalAssemblies(AssemblyDefinition assembly)
        {
            if (assembly == null) throw new ArgumentNullException(nameof(assembly));
            const int mdCountMax = 1 << 24;
            bool dumpAssemblyName = true;
            foreach (var module in assembly.Modules)
            {
                for (int i = 1; i < mdCountMax; i++)
                {
                    var item = module.LookupToken(new MetadataToken(TokenType.MemberRef, i));
                    if (item == null)
                    {
                        break;
                    }

                    if (item is MemberReference memberRef)
                    {
                        var memberDef = memberRef.Resolve();
                        bool isInternal = CheckIsInternal(memberDef);
                        if (isInternal && !assembly.Modules.Contains(memberDef.DeclaringType.Module))
                        {
                            if (dumpAssemblyName)
                            {
                                Console.WriteLine($"Internals used in Assembly: {assembly.Name} ({assembly.MainModule.FileName})");
                                Console.WriteLine("---------------------------------------------------------------------------------------");
                                dumpAssemblyName = false;
                            }

                            Console.WriteLine($"{memberDef.GetType().Name}: {memberRef} => Assembly: {memberDef.DeclaringType.Module.FileName}");
                        }
                    }
                }
            }
        }
        private static bool CheckIsInternal(IMemberDefinition memberDef)
        {
            if (memberDef == null)
            {
                return false;
            }

            bool isInternal = false;
            switch (memberDef)
            {
                case MethodDefinition methodDef:
                    isInternal = methodDef.IsAssembly;
                    break;
                case FieldDefinition fieldDef:
                    isInternal = fieldDef.IsAssembly;
                    break;
                case TypeDefinition typeDef:
                    isInternal = !(typeDef.IsPublic || typeDef.IsNestedPublic);
                    break;
            }

            // Check also the declaring type
            return isInternal || CheckIsInternal(memberDef.DeclaringType);
        }
    }
}