/*
    Copyright 2017-2019 Katy Coe - http://www.hearthcode.org - http://www.djkaty.com

    All rights reserved.
*/

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Text;

namespace Il2CppInspector.Reflection
{
    public abstract class MethodBase : MemberInfo
    {
        // IL2CPP-specific data
        public Il2CppMethodDefinition Definition { get; }
        public int Index { get; }
        public ulong VirtualAddress { get; }

        // Information/flags about the method
        public MethodAttributes Attributes { get; protected set; }

        // True if the type contains unresolved generic type parameters
        public bool ContainsGenericParameters => throw new NotImplementedException();

        // TODO: Custom attribute stuff

        public List<ParameterInfo> DeclaredParameters { get; } = new List<ParameterInfo>();

        public bool IsAbstract => (Attributes & MethodAttributes.Abstract) == MethodAttributes.Abstract;
        public bool IsAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Assembly;
        public bool IsConstructor => MemberType == MemberTypes.Constructor;
        public bool IsFamily => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Family;
        public bool IsFamilyAndAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamANDAssem;
        public bool IsFamilyOrAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamORAssem;
        public bool IsFinal => (Attributes & MethodAttributes.Final) == MethodAttributes.Final;
        public bool IsGenericMethod => throw new NotImplementedException();
        public bool IsGenericMethodDefinition => throw new NotImplementedException();
        public bool IsHideBySig => (Attributes & MethodAttributes.HideBySig) == MethodAttributes.HideBySig;
        public bool IsPrivate => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Private;
        public bool IsPublic => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;
        public bool IsSpecialName => (Attributes & MethodAttributes.SpecialName) == MethodAttributes.SpecialName;
        public bool IsStatic => (Attributes & MethodAttributes.Static) == MethodAttributes.Static;
        public bool IsVirtual => (Attributes & MethodAttributes.Virtual) == MethodAttributes.Virtual;

        // TODO: GetMethodBody()

        protected MethodBase(Il2CppInspector pkg, int methodIndex, TypeInfo declaringType) : base(declaringType) {
            Definition = pkg.Methods[methodIndex];
            Index = methodIndex;
            Name = pkg.Strings[Definition.nameIndex];

            // Find method pointer
            if (Definition.methodIndex >= 0) {

                // Global method pointer array
                if (pkg.Version <= 24.1) {
                    VirtualAddress = pkg.GlobalMethodPointers[Definition.methodIndex];
                }

                // Per-module method pointer array uses the bottom 24 bits of the method's metadata token
                // Derived from il2cpp::vm::MetadataCache::GetMethodPointer
                else {
                    var method = (Definition.token & 0xffffff);
                    if (method != 0) {
                        // In the event of an exception, the method pointer is not set in the file
                        // This probably means it has been optimized away by the compiler, or is an unused generic method
                        try {
                            pkg.BinaryImage.Position = pkg.BinaryImage.MapVATR(Assembly.Module.methodPointers + (ulong)((method - 1) * (pkg.BinaryImage.Bits / 8)));
                            VirtualAddress = (ulong)pkg.BinaryImage.ReadWord();
                        }
                        catch (Exception) { }
                    }
                }

                // Remove ARM Thumb marker LSB if necessary
                VirtualAddress &= 0xffff_ffff_ffff_fffe;
            }

            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_PRIVATE)
                Attributes |= MethodAttributes.Private;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_PUBLIC)
                Attributes |= MethodAttributes.Public;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_FAM_AND_ASSEM)
                Attributes |= MethodAttributes.FamANDAssem;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_ASSEM)
                Attributes |= MethodAttributes.Assembly;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_FAMILY)
                Attributes |= MethodAttributes.Family;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_MEMBER_ACCESS_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_FAM_OR_ASSEM)
                Attributes |= MethodAttributes.FamORAssem;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_VIRTUAL) != 0)
                Attributes |= MethodAttributes.Virtual;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_ABSTRACT) != 0)
                Attributes |= MethodAttributes.Abstract;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_STATIC) != 0)
                Attributes |= MethodAttributes.Static;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_FINAL) != 0)
                Attributes |= MethodAttributes.Final;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_HIDE_BY_SIG) != 0)
                Attributes |= MethodAttributes.HideBySig;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_VTABLE_LAYOUT_MASK) == Il2CppConstants.METHOD_ATTRIBUTE_NEW_SLOT)
                Attributes |= MethodAttributes.NewSlot;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_PINVOKE_IMPL) != 0)
                Attributes |= MethodAttributes.PinvokeImpl;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_SPECIAL_NAME) != 0)
                Attributes |= MethodAttributes.SpecialName;
            if ((Definition.flags & Il2CppConstants.METHOD_ATTRIBUTE_UNMANAGED_EXPORT) != 0)
                Attributes |= MethodAttributes.UnmanagedExport;

            // Add arguments
            for (var p = Definition.parameterStart; p < Definition.parameterStart + Definition.parameterCount; p++)
                DeclaredParameters.Add(new ParameterInfo(pkg, p, this));
        }

        public string GetModifierString() {
            // Interface methods and properties have no visible modifiers (they are always declared 'public abstract')
            if (DeclaringType.IsInterface)
                return string.Empty;

            StringBuilder modifiers = new StringBuilder();

            if (IsPrivate)
                modifiers.Append("private ");
            if (IsPublic)
                modifiers.Append("public ");
            if (IsFamily)
                modifiers.Append("protected ");
            if (IsAssembly)
                modifiers.Append("internal ");
            if (IsFamilyOrAssembly)
                modifiers.Append("protected internal ");
            if (IsFamilyAndAssembly)
                modifiers.Append("[family and assembly] ");

            if (IsAbstract)
                modifiers.Append("abstract ");
            // Methods that implement interfaces are IsVirtual && IsFinal with MethodAttributes.NewSlot (don't show 'virtual sealed' for these)
            if (IsFinal && (Attributes & MethodAttributes.VtableLayoutMask) == MethodAttributes.ReuseSlot)
                modifiers.Append("sealed override ");
            // All abstract, override and sealed methods are also virtual by nature
            if (IsVirtual && !IsAbstract && !IsFinal)
                modifiers.Append((Attributes & MethodAttributes.VtableLayoutMask) == MethodAttributes.NewSlot ? "virtual " : "override ");
            if (IsStatic)
                modifiers.Append("static ");
            if ((Attributes & MethodAttributes.PinvokeImpl) != 0)
                modifiers.Append("extern ");

            // Will include a trailing space
            return modifiers.ToString();
        }
    }
}