/*
    Copyright 2017 Perfare - https://github.com/Perfare/Il2CppDumper
    Copyright 2017-2021 Katy Coe - http://www.djkaty.com - https://github.com/djkaty

    All rights reserved.
*/

using System.Collections.Immutable;
using System.Runtime.CompilerServices;
using Il2CppInspector.Next;
using Il2CppInspector.Next.Metadata;
using VersionedSerialization;

namespace Il2CppInspector
{
    public class Metadata : BinaryObjectStreamReader
    {
        public Il2CppGlobalMetadataHeader Header { get; set; }

        public ImmutableArray<Il2CppAssemblyDefinition> Assemblies { get; set; }
        public ImmutableArray<Il2CppImageDefinition> Images { get; set; }
        public ImmutableArray<Il2CppTypeDefinition> Types { get; set; }
        public ImmutableArray<Il2CppMethodDefinition> Methods { get; set; }
        public ImmutableArray<Il2CppParameterDefinition> Params { get; set; }
        public ImmutableArray<Il2CppFieldDefinition> Fields { get; set; }
        public ImmutableArray<Il2CppFieldDefaultValue> FieldDefaultValues { get; set; }
        public ImmutableArray<Il2CppParameterDefaultValue> ParameterDefaultValues { get; set; }
        public ImmutableArray<Il2CppPropertyDefinition> Properties { get; set; }
        public ImmutableArray<Il2CppEventDefinition> Events { get; set; }
        public ImmutableArray<Il2CppGenericContainer> GenericContainers { get; set; }
        public ImmutableArray<Il2CppGenericParameter> GenericParameters { get; set; }
        public ImmutableArray<Il2CppCustomAttributeTypeRange> AttributeTypeRanges { get; set; }
        public ImmutableArray<Il2CppCustomAttributeDataRange> AttributeDataRanges { get; set; }
        public ImmutableArray<Il2CppInterfaceOffsetPair> InterfaceOffsets { get; set; }
        public ImmutableArray<Il2CppMetadataUsageList> MetadataUsageLists { get; set; }
        public ImmutableArray<Il2CppMetadataUsagePair> MetadataUsagePairs { get; set; }
        public ImmutableArray<Il2CppFieldRef> FieldRefs { get; set; }

        public ImmutableArray<int> InterfaceUsageIndices { get; set; }
        public ImmutableArray<int> NestedTypeIndices { get; set; }
        public ImmutableArray<int> AttributeTypeIndices { get; set; }
        public ImmutableArray<int> GenericConstraintIndices { get; set; }
        public ImmutableArray<uint> VTableMethodIndices { get; set; }
        public string[] StringLiterals { get; set; }

        public int FieldAndParameterDefaultValueDataOffset => Version >= MetadataVersions.V380
            ? Header.FieldAndParameterDefaultValueData.Offset
            : Header.FieldAndParameterDefaultValueDataOffset;

        public int AttributeDataOffset => Version >= MetadataVersions.V380
            ? Header.AttributeData.Offset
            : Header.AttributeDataOffset;

        public Dictionary<int, string> Strings { get; private set; } = [];

        // Set if something in the metadata has been modified / decrypted
        public bool IsModified { get; private set; } = false;

        // Status update callback
        private EventHandler<string> OnStatusUpdate { get; set; }
        private void StatusUpdate(string status) => OnStatusUpdate?.Invoke(this, status);

        // Initialize metadata object from a stream
        public static Metadata FromStream(MemoryStream stream, EventHandler<string> statusCallback = null) {
            // TODO: This should really be placed before the Metadata object is created,
            // but for now this ensures it is called regardless of which client is in use
            PluginHooks.LoadPipelineStarting();

            var metadata = new Metadata(statusCallback);
            stream.Position = 0;
            stream.CopyTo(metadata);
            metadata.Position = 0;
            metadata.Initialize();
            return metadata;
        }

        private Metadata(EventHandler<string> statusCallback = null) : base() => OnStatusUpdate = statusCallback;

        private void Initialize()
        {
            // Pre-processing hook
            var pluginResult = PluginHooks.PreProcessMetadata(this);
            IsModified = pluginResult.IsStreamModified;

            StatusUpdate("Processing metadata");

            // Read metadata header
            Header = ReadVersionedObject<Il2CppGlobalMetadataHeader>(0);

            // Check for correct magic bytes
            if (!Header.SanityValid) {
                throw new InvalidOperationException("The supplied metadata file is not valid.");
            }

            // Set object versioning for Bin2Object from metadata version
            Version = new StructVersion(Header.Version);

            if (Version < MetadataVersions.V160 || Version > MetadataVersions.V380) {
                throw new InvalidOperationException($"The supplied metadata file is not of a supported version ({Header.Version}).");
            }

            // Rewind and read metadata header with the correct version settings
            Header = ReadVersionedObject<Il2CppGlobalMetadataHeader>(0);

            // Setup the proper index sizes for metadata v38+
            if (Version >= MetadataVersions.V380) 
            {
                static int GetIndexSize(int elementCount)
                {
                    return elementCount switch
                    {
                        <= byte.MaxValue => sizeof(byte),
                        <= ushort.MaxValue => sizeof(ushort),
                        _ => sizeof(int)
                    };
                }

                var typeDefinitionIndexSize = GetIndexSize(Header.TypeDefinitions.Count);
                var genericContainerIndexSize = GetIndexSize(Header.GenericContainers.Count);

                var tag = $"{TypeDefinitionIndex.TagPrefix}{typeDefinitionIndexSize}"
                          + $"_{GenericContainerIndex.TagPrefix}{genericContainerIndexSize}";

                var tempVersion = new StructVersion(Version.Major, Version.Minor, tag);

                // now we need to derive the size for TypeIndex.
                // this is normally done through s_Il2CppMetadataRegistration->typesCount, but we don't want to use the binary for this
                // as we do not have it available at this point.
                // thankfully, we can just guess the size based off the three available options and the known total size of
                // a type entry that uses TypeIndex.
                var expectedEventDefinitionSize = Header.Events.SectionSize / Header.Events.Count;
                var maxEventDefinitionSize = Il2CppEventDefinition.Size(tempVersion);

                int typeIndexSize;
                if (expectedEventDefinitionSize == maxEventDefinitionSize)
                    typeIndexSize = sizeof(int);
                else if (expectedEventDefinitionSize == maxEventDefinitionSize - 2)
                    typeIndexSize = sizeof(ushort);
                else if (expectedEventDefinitionSize == maxEventDefinitionSize - 3)
                    typeIndexSize = sizeof(byte);
                else
                    throw new InvalidOperationException("Could not determine TypeIndex size based on the metadata header");

                var fullTag = $"{tag}_{TypeIndex.TagPrefix}{typeIndexSize}";
                Version = new StructVersion(Version.Major, Version.Minor, fullTag);
            }

            // Sanity checking
            // Unity.IL2CPP.MetadataCacheWriter.WriteLibIl2CppMetadata always writes the metadata information in the same order it appears in the header,
            // with each block always coming directly after the previous block, 4-byte aligned. We can use this to check the integrity of the data and
            // detect sub-versions.

            // For metadata v24.0, the header can either be either 0x110 (24.0, 24.1) or 0x108 (24.2) bytes long. Since 'stringLiteralOffset' is the first thing
            // in the header after the sanity and version fields, and since it will always point directly to the first byte after the end of the header,
            // we can use this value to determine the actual header length and therefore narrow down the metadata version to 24.0/24.1 or 24.2.

            if (!pluginResult.SkipValidation) {
                var realHeaderLength = Header.StringLiteralOffset;

                if (realHeaderLength != Sizeof<Il2CppGlobalMetadataHeader>()) {
                    if (Version == MetadataVersions.V240) {
                        Version = MetadataVersions.V242;
                        Header = ReadVersionedObject<Il2CppGlobalMetadataHeader>(0);
                    }
                }

                if (realHeaderLength != Sizeof<Il2CppGlobalMetadataHeader>()) {
                    throw new InvalidOperationException("Could not verify the integrity of the metadata file or accurately identify the metadata sub-version");
                }
            }

            // Load all the relevant metadata using offsets provided in the header
            if (Version >= MetadataVersions.V160)
                Images = ReadMetadataArray<Il2CppImageDefinition>(Header.ImagesOffset, Header.ImagesSize, Header.Images);

            // As an additional sanity check, all images in the metadata should have Mono.Cecil.MetadataToken == 1
            // In metadata v24.1, two extra fields were added which will cause the below test to fail.
            // In that case, we can then adjust the version number and reload
            // Tokens were introduced in v19 - we don't bother testing earlier versions
            if (Version >= MetadataVersions.V190 && Images.Any(x => x.Token != 1))
                if (Version == MetadataVersions.V240) {
                    Version = MetadataVersions.V241;

                    // No need to re-read the header, it's the same for both sub-versions
                    Images = ReadMetadataArray<Il2CppImageDefinition>(Header.ImagesOffset, Header.ImagesSize, Header.Images);

                    if (Images.Any(x => x.Token != 1))
                        throw new InvalidOperationException("Could not verify the integrity of the metadata file image list");
                }

            Types = ReadMetadataArray<Il2CppTypeDefinition>(Header.TypeDefinitionsOffset, Header.TypeDefinitionsSize, Header.TypeDefinitions);
            Methods = ReadMetadataArray<Il2CppMethodDefinition>(Header.MethodsOffset, Header.MethodsSize, Header.Methods);
            Params = ReadMetadataArray<Il2CppParameterDefinition>(Header.ParametersOffset, Header.ParametersSize, Header.Parameters);
            Fields = ReadMetadataArray<Il2CppFieldDefinition>(Header.FieldsOffset, Header.FieldsSize, Header.Fields);
            FieldDefaultValues = ReadMetadataArray<Il2CppFieldDefaultValue>(Header.FieldDefaultValuesOffset, Header.FieldDefaultValuesSize, Header.FieldDefaultValues);
            Properties = ReadMetadataArray<Il2CppPropertyDefinition>(Header.PropertiesOffset, Header.PropertiesSize, Header.Properties);
            Events = ReadMetadataArray<Il2CppEventDefinition>(Header.EventsOffset, Header.EventsSize, Header.Events);
            InterfaceUsageIndices = ReadMetadataPrimitiveArray<int>(Header.InterfacesOffset, Header.InterfacesSize, Header.Interfaces);
            NestedTypeIndices = ReadMetadataPrimitiveArray<int>(Header.NestedTypesOffset, Header.NestedTypesSize, Header.NestedTypes);
            GenericContainers = ReadMetadataArray<Il2CppGenericContainer>(Header.GenericContainersOffset, Header.GenericContainersSize, Header.GenericContainers);
            GenericParameters = ReadMetadataArray<Il2CppGenericParameter>(Header.GenericParametersOffset, Header.GenericParametersSize, Header.GenericParameters);
            GenericConstraintIndices = ReadMetadataPrimitiveArray<int>(Header.GenericParameterConstraintsOffset, Header.GenericParameterConstraintsSize, Header.GenericParameterConstraints);
            InterfaceOffsets = ReadMetadataArray<Il2CppInterfaceOffsetPair>(Header.InterfaceOffsetsOffset, Header.InterfaceOffsetsSize, Header.InterfaceOffsets);
            VTableMethodIndices = ReadMetadataPrimitiveArray<uint>(Header.VTableMethodsOffset, Header.VTableMethodsSize, Header.VtableMethods);

            if (Version >= MetadataVersions.V160) 
            {
                // In v24.4 hashValueIndex was removed from Il2CppAssemblyNameDefinition, which is a field in Il2CppAssemblyDefinition
                // The number of images and assemblies should be the same. If they are not, we deduce that we are using v24.4
                // Note the version comparison matches both 24.2 and 24.3 here since 24.3 is tested for during binary loading
                var assemblyCount = Header.AssembliesSize / Sizeof<Il2CppAssemblyDefinition>();
                var changedAssemblyDefStruct = false;
                if ((Version == MetadataVersions.V241 || Version == MetadataVersions.V242 || Version == MetadataVersions.V243) && assemblyCount < Images.Length)
                {
                    if (Version == MetadataVersions.V241)
                        changedAssemblyDefStruct = true;

                    Version = MetadataVersions.V244;
                }

                Assemblies = ReadMetadataArray<Il2CppAssemblyDefinition>(Header.AssembliesOffset, Header.AssembliesSize, Header.Assemblies);

                if (changedAssemblyDefStruct)
                    Version = MetadataVersions.V241;

                ParameterDefaultValues = ReadMetadataArray<Il2CppParameterDefaultValue>(Header.ParameterDefaultValuesOffset, Header.ParameterDefaultValuesSize, Header.ParameterDefaultValues);
            }

            if (Version >= MetadataVersions.V190 && Version < MetadataVersions.V270) 
            {
                MetadataUsageLists = ReadMetadataArray<Il2CppMetadataUsageList>(Header.MetadataUsageListsOffset, Header.MetadataUsageListsCount, default);
                MetadataUsagePairs = ReadMetadataArray<Il2CppMetadataUsagePair>(Header.MetadataUsagePairsOffset, Header.MetadataUsagePairsCount, default);
            }

            if (Version >= MetadataVersions.V190) 
            {
                FieldRefs = ReadMetadataArray<Il2CppFieldRef>(Header.FieldRefsOffset, Header.FieldRefsSize, Header.FieldRefs);
            }

            if (Version >= MetadataVersions.V210 && Version < MetadataVersions.V290) 
            {
                AttributeTypeIndices = ReadMetadataPrimitiveArray<int>(Header.AttributesTypesOffset, Header.AttributesTypesCount, default);
                AttributeTypeRanges = ReadMetadataArray<Il2CppCustomAttributeTypeRange>(Header.AttributesInfoOffset, Header.AttributesInfoCount, default);
            }

            if (Version >= MetadataVersions.V290)
            {
                AttributeDataRanges = ReadMetadataArray<Il2CppCustomAttributeDataRange>(Header.AttributeDataRangeOffset,
                    Header.AttributeDataRangeSize, Header.AttributeDataRanges);
            }

            // Get all metadata strings
            var pluginGetStringsResult = PluginHooks.GetStrings(this);
            if (pluginGetStringsResult.IsDataModified && !pluginGetStringsResult.IsInvalid)
                Strings = pluginGetStringsResult.Strings;

            else {
                Position = Header.StringOffset;

                while (Position < Header.StringOffset + Header.StringSize)
                    Strings.Add((int) Position - Header.StringOffset, ReadNullTerminatedString());
            }

            // Get all string literals
            var pluginGetStringLiteralsResult = PluginHooks.GetStringLiterals(this);
            if (pluginGetStringLiteralsResult.IsDataModified)
                StringLiterals = pluginGetStringLiteralsResult.StringLiterals.ToArray();

            else
            {
                var stringLiteralList = ReadMetadataArray<Il2CppStringLiteral>(Header.StringLiteralOffset,
                    Header.StringLiteralSize, Header.StringLiterals);

                var dataOffset = Version >= MetadataVersions.V380
                    ? Header.StringLiteralData.Offset
                    : Header.StringLiteralDataOffset;

                if (Version >= MetadataVersions.V350)
                {
                    StringLiterals = new string[stringLiteralList.Length - 1];
                    for (var i = 0; i < stringLiteralList.Length; i++)
                    {
                        var currentStringDataIndex = stringLiteralList[i].DataIndex;
                        var nextStringDataIndex = stringLiteralList[i + 1].DataIndex;
                        var stringLength = nextStringDataIndex - currentStringDataIndex;

                        StringLiterals[i] = ReadFixedLengthString(dataOffset + currentStringDataIndex, stringLength);
                    }
                }
                else
                {
                    StringLiterals = new string[stringLiteralList.Length];
                    for (var i = 0; i < stringLiteralList.Length; i++)
                        StringLiterals[i] = ReadFixedLengthString(dataOffset + stringLiteralList[i].DataIndex, 
                            (int)stringLiteralList[i].Length);

                }
            }

            // Post-processing hook
            IsModified |= PluginHooks.PostProcessMetadata(this).IsStreamModified;
            return;
        }

        public ImmutableArray<T> ReadMetadataPrimitiveArray<T>(int oldOffset, int oldSize, Il2CppSectionMetadata newMetadata)
            where T : unmanaged
        {
            return Version >= MetadataVersions.V380
                ? ReadPrimitiveArray<T>(newMetadata.Offset, newMetadata.Count)
                : ReadPrimitiveArray<T>(oldOffset, oldSize / Unsafe.SizeOf<T>());
        }

        public ImmutableArray<T> ReadMetadataArray<T>(int oldOffset, int oldSize, Il2CppSectionMetadata newMetadata)
            where T : IReadable, new()
        {
            return Version >= MetadataVersions.V380
                ? ReadVersionedObjectArray<T>(newMetadata.Offset, newMetadata.Count)
                : ReadVersionedObjectArray<T>(oldOffset, oldSize / Sizeof<T>());
        }

        // Save metadata to file, overwriting if necessary
        public void SaveToFile(string pathname) {
            Position = 0;
            using var outFile = new FileStream(pathname, FileMode.Create, FileAccess.Write);
            CopyTo(outFile);
        }

        public int Sizeof<T>() where T : IReadable => T.Size(Version, Is32Bit);
    }
}