// Copyright 2018 yuzu emulator team
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <cinttypes>
#include <vector>
#include <lz4.h>
#include "common/common_funcs.h"
#include "common/file_util.h"
#include "common/logging/log.h"
#include "common/swap.h"
#include "core/core.h"
#include "core/gdbstub/gdbstub.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/vm_manager.h"
#include "core/loader/nso.h"
#include "core/memory.h"

namespace Loader {

struct NsoSegmentHeader {
    u32_le offset;
    u32_le location;
    u32_le size;
    union {
        u32_le alignment;
        u32_le bss_size;
    };
};
static_assert(sizeof(NsoSegmentHeader) == 0x10, "NsoSegmentHeader has incorrect size.");

struct NsoHeader {
    u32_le magic;
    u32_le version;
    INSERT_PADDING_WORDS(1);
    u8 flags;
    std::array<NsoSegmentHeader, 3> segments; // Text, RoData, Data (in that order)
    u32_le bss_size;
    INSERT_PADDING_BYTES(0x1c);
    std::array<u32_le, 3> segments_compressed_size;

    bool IsSegmentCompressed(size_t segment_num) const {
        ASSERT_MSG(segment_num < 3, "Invalid segment {}", segment_num);
        return ((flags >> segment_num) & 1);
    }
};
static_assert(sizeof(NsoHeader) == 0x6c, "NsoHeader has incorrect size.");
static_assert(std::is_trivially_copyable_v<NsoHeader>, "NsoHeader isn't trivially copyable.");

struct ModHeader {
    u32_le magic;
    u32_le dynamic_offset;
    u32_le bss_start_offset;
    u32_le bss_end_offset;
    u32_le eh_frame_hdr_start_offset;
    u32_le eh_frame_hdr_end_offset;
    u32_le module_offset; // Offset to runtime-generated module object. typically equal to .bss base
};
static_assert(sizeof(ModHeader) == 0x1c, "ModHeader has incorrect size.");

AppLoader_NSO::AppLoader_NSO(FileSys::VirtualFile file) : AppLoader(std::move(file)) {}

FileType AppLoader_NSO::IdentifyType(const FileSys::VirtualFile& file) {
    u32 magic = 0;
    if (file->ReadObject(&magic) != sizeof(magic)) {
        return FileType::Error;
    }

    if (Common::MakeMagic('N', 'S', 'O', '0') != magic) {
        return FileType::Error;
    }

    return FileType::NSO;
}

static std::vector<u8> DecompressSegment(const std::vector<u8>& compressed_data,
                                         const NsoSegmentHeader& header) {
    std::vector<u8> uncompressed_data(header.size);
    const int bytes_uncompressed =
        LZ4_decompress_safe(reinterpret_cast<const char*>(compressed_data.data()),
                            reinterpret_cast<char*>(uncompressed_data.data()),
                            static_cast<int>(compressed_data.size()), header.size);

    ASSERT_MSG(bytes_uncompressed == static_cast<int>(header.size) &&
                   bytes_uncompressed == static_cast<int>(uncompressed_data.size()),
               "{} != {} != {}", bytes_uncompressed, header.size, uncompressed_data.size());

    return uncompressed_data;
}

static constexpr u32 PageAlignSize(u32 size) {
    return (size + Memory::PAGE_MASK) & ~Memory::PAGE_MASK;
}

VAddr AppLoader_NSO::LoadModule(FileSys::VirtualFile file, VAddr load_base) {
    if (file == nullptr)
        return {};

    if (file->GetSize() < sizeof(NsoHeader))
        return {};

    NsoHeader nso_header{};
    if (sizeof(NsoHeader) != file->ReadObject(&nso_header))
        return {};

    if (nso_header.magic != Common::MakeMagic('N', 'S', 'O', '0'))
        return {};

    // Build program image
    auto& kernel = Core::System::GetInstance().Kernel();
    Kernel::SharedPtr<Kernel::CodeSet> codeset = Kernel::CodeSet::Create(kernel, "");
    std::vector<u8> program_image;
    for (std::size_t i = 0; i < nso_header.segments.size(); ++i) {
        std::vector<u8> data =
            file->ReadBytes(nso_header.segments_compressed_size[i], nso_header.segments[i].offset);
        if (nso_header.IsSegmentCompressed(i)) {
            data = DecompressSegment(data, nso_header.segments[i]);
        }
        program_image.resize(nso_header.segments[i].location);
        program_image.insert(program_image.end(), data.begin(), data.end());
        codeset->segments[i].addr = nso_header.segments[i].location;
        codeset->segments[i].offset = nso_header.segments[i].location;
        codeset->segments[i].size = PageAlignSize(static_cast<u32>(data.size()));
    }

    // MOD header pointer is at .text offset + 4
    u32 module_offset;
    std::memcpy(&module_offset, program_image.data() + 4, sizeof(u32));

    // Read MOD header
    ModHeader mod_header{};
    // Default .bss to size in segment header if MOD0 section doesn't exist
    u32 bss_size{PageAlignSize(nso_header.segments[2].bss_size)};
    std::memcpy(&mod_header, program_image.data() + module_offset, sizeof(ModHeader));
    const bool has_mod_header{mod_header.magic == Common::MakeMagic('M', 'O', 'D', '0')};
    if (has_mod_header) {
        // Resize program image to include .bss section and page align each section
        bss_size = PageAlignSize(mod_header.bss_end_offset - mod_header.bss_start_offset);
    }
    codeset->DataSegment().size += bss_size;
    const u32 image_size{PageAlignSize(static_cast<u32>(program_image.size()) + bss_size)};
    program_image.resize(image_size);

    // Load codeset for current process
    codeset->name = file->GetName();
    codeset->memory = std::make_shared<std::vector<u8>>(std::move(program_image));
    Core::CurrentProcess()->LoadModule(codeset, load_base);

    // Register module with GDBStub
    GDBStub::RegisterModule(codeset->name, load_base, load_base);

    return load_base + image_size;
}

ResultStatus AppLoader_NSO::Load(Kernel::SharedPtr<Kernel::Process>& process) {
    if (is_loaded) {
        return ResultStatus::ErrorAlreadyLoaded;
    }

    // Load module
    const VAddr base_address = process->vm_manager.GetCodeRegionBaseAddress();
    LoadModule(file, base_address);
    LOG_DEBUG(Loader, "loaded module {} @ 0x{:X}", file->GetName(), base_address);

    process->Run(base_address, Kernel::THREADPRIO_DEFAULT, Memory::DEFAULT_STACK_SIZE);

    is_loaded = true;
    return ResultStatus::Success;
}

} // namespace Loader