/*
    Copyright 2017-2021 Katy Coe - http://www.djkaty.com - https://github.com/djkaty

    All rights reserved.
*/

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

namespace Il2CppInspector.Reflection
{
    // See: https://docs.microsoft.com/en-us/dotnet/api/system.reflection.customattributedata?view=netframework-4.8
    public class CustomAttributeData
    {
        // IL2CPP-specific data
        public TypeModel Model => AttributeType.Assembly.Model;
        public int Index { get; set; }

        // The type of the attribute
        public TypeInfo AttributeType { get; set; }

        public (ulong Start, ulong End) VirtualAddress =>
            // The last one will be wrong but there is no way to calculate it
            (Model.Package.CustomAttributeGenerators[Index], Model.Package.FunctionAddresses[Model.Package.CustomAttributeGenerators[Index]]);

        // C++ method names
        // TODO: Known issue here where we should be using CppDeclarationGenerator.TypeNamer to ensure uniqueness
        public string Name => $"{AttributeType.Name.ToCIdentifier()}_CustomAttributesCacheGenerator";

        // C++ method signature
        public string Signature => $"void {Name}(CustomAttributesCache *)";

        public override string ToString() => "[" + AttributeType.FullName + "]";

        // Get the machine code of the C++ function
        public byte[] GetMethodBody() => Model.Package.BinaryImage.ReadMappedBytes(VirtualAddress.Start, (int) (VirtualAddress.End - VirtualAddress.Start));

        // Get all the custom attributes for a given assembly, type, member or parameter
        private static IEnumerable<CustomAttributeData> getCustomAttributes(Assembly asm, int customAttributeIndex) {
            if (customAttributeIndex < 0)
                yield break;

            var pkg = asm.Model.Package;

            // Attribute type ranges weren't included before v21 (customASttributeGenerators was though)
            if (pkg.Version < 21)
                yield break;

            var range = pkg.AttributeTypeRanges[customAttributeIndex];
            for (var i = range.start; i < range.start + range.count; i++) {
                var typeIndex = pkg.AttributeTypeIndices[i];

                if (asm.Model.AttributesByIndices.TryGetValue(i, out var attribute)) {
                    yield return attribute;
                    continue;
                }

                attribute = new CustomAttributeData { Index = customAttributeIndex, AttributeType = asm.Model.TypesByReferenceIndex[typeIndex] };

                asm.Model.AttributesByIndices.TryAdd(i, attribute);
                yield return attribute;
            }
        }

        private static IList<CustomAttributeData> getCustomAttributes(Assembly asm, uint token, int customAttributeIndex) =>
                getCustomAttributes(asm, asm.Model.GetCustomAttributeIndex(asm, token, customAttributeIndex)).ToList();
            
        public static IList<CustomAttributeData> GetCustomAttributes(Assembly asm) => getCustomAttributes(asm, asm.AssemblyDefinition.token, asm.AssemblyDefinition.customAttributeIndex);
        public static IList<CustomAttributeData> GetCustomAttributes(EventInfo evt) => getCustomAttributes(evt.Assembly, evt.Definition.token, evt.Definition.customAttributeIndex);
        public static IList<CustomAttributeData> GetCustomAttributes(FieldInfo field) => getCustomAttributes(field.Assembly, field.Definition.token, field.Definition.customAttributeIndex);
        public static IList<CustomAttributeData> GetCustomAttributes(MethodBase method) => getCustomAttributes(method.Assembly, method.Definition.token, method.Definition.customAttributeIndex);
        public static IList<CustomAttributeData> GetCustomAttributes(ParameterInfo param) => getCustomAttributes(param.DeclaringMethod.Assembly, param.Definition.token, param.Definition.customAttributeIndex);
        public static IList<CustomAttributeData> GetCustomAttributes(PropertyInfo prop)
            => prop.Definition != null ? getCustomAttributes(prop.Assembly, prop.Definition.token, prop.Definition.customAttributeIndex) : new List<CustomAttributeData>();
        public static IList<CustomAttributeData> GetCustomAttributes(TypeInfo type) => type.Definition != null? getCustomAttributes(type.Assembly, type.Definition.token, type.Definition.customAttributeIndex) : new List<CustomAttributeData>();
    }
}