// Copyright 2017 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <vector>

#include "common/logging/log.h"
#include "common/swap.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/resource_limit.h"
#include "core/loader/nro.h"
#include "core/memory.h"

namespace Loader {

struct NroSegmentHeader {
    u32_le offset;
    u32_le size;
};
static_assert(sizeof(NroSegmentHeader) == 0x8, "NroSegmentHeader has incorrect size.");

struct NroHeader {
    INSERT_PADDING_BYTES(0x4);
    u32_le module_header_offset;
    INSERT_PADDING_BYTES(0x8);
    u32_le magic;
    INSERT_PADDING_BYTES(0x4);
    u32_le file_size;
    INSERT_PADDING_BYTES(0x4);
    std::array<NroSegmentHeader, 3> segments; // Text, RoData, Data (in that order)
    u32_le bss_size;
    INSERT_PADDING_BYTES(0x44);
};
static_assert(sizeof(NroHeader) == 0x80, "NroHeader has incorrect size.");

struct ModHeader {
    u32_le magic;
    u32_le dynamic_offset;
    u32_le bss_start_offset;
    u32_le bss_end_offset;
    u32_le unwind_start_offset;
    u32_le unwind_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.");

FileType AppLoader_NRO::IdentifyType(FileUtil::IOFile& file) {
    // Read NSO header
    NroHeader nro_header{};
    file.Seek(0, SEEK_SET);
    if (sizeof(NroHeader) != file.ReadBytes(&nro_header, sizeof(NroHeader))) {
        return FileType::Error;
    }
    if (nro_header.magic == MakeMagic('N', 'R', 'O', '0')) {
        return FileType::NRO;
    }
    return FileType::Error;
}

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

static std::vector<u8> ReadSegment(FileUtil::IOFile& file, const NroSegmentHeader& header) {
    std::vector<u8> data;
    data.resize(header.size);

    file.Seek(header.offset + sizeof(NroHeader), SEEK_SET);
    size_t bytes_read{file.ReadBytes(data.data(), header.size)};
    if (header.size != PageAlignSize(static_cast<u32>(bytes_read))) {
        LOG_CRITICAL(Loader, "Failed to read NRO segment bytes", header.size);
        return {};
    }

    return data;
}

bool AppLoader_NRO::LoadNro(const std::string& path, VAddr load_base) {
    FileUtil::IOFile file(path, "rb");
    if (!file.IsOpen()) {
        return {};
    }

    // Read NSO header
    NroHeader nro_header{};
    file.Seek(0, SEEK_SET);
    if (sizeof(NroHeader) != file.ReadBytes(&nro_header, sizeof(NroHeader))) {
        return {};
    }
    if (nro_header.magic != MakeMagic('N', 'R', 'O', '0')) {
        return {};
    }

    // Build program image
    Kernel::SharedPtr<Kernel::CodeSet> codeset = Kernel::CodeSet::Create("", 0);
    std::vector<u8> program_image;
    program_image.resize(PageAlignSize(nro_header.file_size + nro_header.bss_size));
    file.Seek(0, SEEK_SET);
    file.ReadBytes(program_image.data(), nro_header.file_size);

    for (int i = 0; i < nro_header.segments.size(); ++i) {
        codeset->segments[i].addr = nro_header.segments[i].offset;
        codeset->segments[i].offset = nro_header.segments[i].offset;
        codeset->segments[i].size = PageAlignSize(nro_header.segments[i].size);
    }

    // Read MOD header
    ModHeader mod_header{};
    u32 bss_size{Memory::PAGE_SIZE}; // Default .bss to page size if MOD0 section doesn't exist
    std::memcpy(&mod_header, program_image.data() + nro_header.module_header_offset,
                sizeof(ModHeader));
    const bool has_mod_header{mod_header.magic == 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->data.size += bss_size;
    }
    program_image.resize(PageAlignSize(static_cast<u32>(program_image.size()) + bss_size));

    // Relocate symbols if there was a proper MOD header - This must happen after the image has been
    // loaded into memory
    if (has_mod_header) {
        Relocate(program_image, nro_header.module_header_offset + mod_header.dynamic_offset,
                 load_base);
    }

    // Load codeset for current process
    codeset->name = path;
    codeset->memory = std::make_shared<std::vector<u8>>(std::move(program_image));
    Kernel::g_current_process->LoadModule(codeset, load_base);

    return true;
}

ResultStatus AppLoader_NRO::Load(Kernel::SharedPtr<Kernel::Process>& process) {
    if (is_loaded) {
        return ResultStatus::ErrorAlreadyLoaded;
    }
    if (!file.IsOpen()) {
        return ResultStatus::Error;
    }

    // Load and relocate "main" and "sdk" NSO
    static constexpr VAddr base_addr{Memory::PROCESS_IMAGE_VADDR};
    process = Kernel::Process::Create("main");
    if (!LoadNro(filepath, base_addr)) {
        return ResultStatus::ErrorInvalidFormat;
    }

    process->svc_access_mask.set();
    process->address_mappings = default_address_mappings;
    process->resource_limit =
        Kernel::ResourceLimit::GetForCategory(Kernel::ResourceLimitCategory::APPLICATION);
    process->Run(base_addr, 48, Kernel::DEFAULT_STACK_SIZE);

    ResolveImports();

    is_loaded = true;
    return ResultStatus::Success;
}

} // namespace Loader
