// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <algorithm>
#include <cstring>
#include <memory>

#include "common/logging/log.h"
#include "common/string_util.h"
#include "common/swap.h"

#include "core/hle/kernel/process.h"
#include "core/hle/kernel/resource_limit.h"
#include "core/loader/ncch.h"
#include "core/memory.h"

////////////////////////////////////////////////////////////////////////////////////////////////////
// Loader namespace

namespace Loader {

static const int kMaxSections = 8;        ///< Maximum number of sections (files) in an ExeFs
static const int kBlockSize   = 0x200;    ///< Size of ExeFS blocks (in bytes)

/**
 * Get the decompressed size of an LZSS compressed ExeFS file
 * @param buffer Buffer of compressed file
 * @param size Size of compressed buffer
 * @return Size of decompressed buffer
 */
static u32 LZSS_GetDecompressedSize(const u8* buffer, u32 size) {
    u32 offset_size = *(u32*)(buffer + size - 4);
    return offset_size + size;
}

/**
 * Decompress ExeFS file (compressed with LZSS)
 * @param compressed Compressed buffer
 * @param compressed_size Size of compressed buffer
 * @param decompressed Decompressed buffer
 * @param decompressed_size Size of decompressed buffer
 * @return True on success, otherwise false
 */
static bool LZSS_Decompress(const u8* compressed, u32 compressed_size, u8* decompressed, u32 decompressed_size) {
    const u8* footer = compressed + compressed_size - 8;
    u32 buffer_top_and_bottom = *reinterpret_cast<const u32*>(footer);
    u32 out = decompressed_size;
    u32 index = compressed_size - ((buffer_top_and_bottom >> 24) & 0xFF);
    u32 stop_index = compressed_size - (buffer_top_and_bottom & 0xFFFFFF);

    memset(decompressed, 0, decompressed_size);
    memcpy(decompressed, compressed, compressed_size);

    while (index > stop_index) {
       u8 control = compressed[--index];

        for (unsigned i = 0; i < 8; i++) {
            if (index <= stop_index)
                break;
            if (index <= 0)
                break;
            if (out <= 0)
                break;

            if (control & 0x80) {
                // Check if compression is out of bounds
                if (index < 2)
                    return false;
                index -= 2;

                u32 segment_offset = compressed[index] | (compressed[index + 1] << 8);
                u32 segment_size = ((segment_offset >> 12) & 15) + 3;
                segment_offset &= 0x0FFF;
                segment_offset += 2;

                // Check if compression is out of bounds
                if (out < segment_size)
                    return false;

                for (unsigned j = 0; j < segment_size; j++) {
                    // Check if compression is out of bounds
                    if (out + segment_offset >= decompressed_size)
                        return false;

                    u8 data = decompressed[out + segment_offset];
                    decompressed[--out] = data;
                }
            } else {
                // Check if compression is out of bounds
                if (out < 1)
                    return false;
                decompressed[--out] = compressed[--index];
            }
            control <<= 1;
        }
    }
    return true;
}

////////////////////////////////////////////////////////////////////////////////////////////////////
// AppLoader_NCCH class

FileType AppLoader_NCCH::IdentifyType(FileUtil::IOFile& file) {
    u32 magic;
    file.Seek(0x100, SEEK_SET);
    if (1 != file.ReadArray<u32>(&magic, 1))
        return FileType::Error;

    if (MakeMagic('N', 'C', 'S', 'D') == magic)
        return FileType::CCI;

    if (MakeMagic('N', 'C', 'C', 'H') == magic)
        return FileType::CXI;

    return FileType::Error;
}

ResultStatus AppLoader_NCCH::LoadExec() {
    using Kernel::SharedPtr;
    using Kernel::CodeSet;

    if (!is_loaded)
        return ResultStatus::ErrorNotLoaded;

    std::vector<u8> code;
    if (ResultStatus::Success == ReadCode(code)) {
        std::string process_name = Common::StringFromFixedZeroTerminatedBuffer(
                (const char*)exheader_header.codeset_info.name, 8);

        SharedPtr<CodeSet> codeset = CodeSet::Create(process_name, ncch_header.program_id);

        codeset->code.offset = 0;
        codeset->code.addr = exheader_header.codeset_info.text.address;
        codeset->code.size = exheader_header.codeset_info.text.num_max_pages * Memory::PAGE_SIZE;

        codeset->rodata.offset = codeset->code.offset + codeset->code.size;
        codeset->rodata.addr = exheader_header.codeset_info.ro.address;
        codeset->rodata.size = exheader_header.codeset_info.ro.num_max_pages * Memory::PAGE_SIZE;

        // TODO(yuriks): Not sure if the bss size is added to the page-aligned .data size or just
        //               to the regular size. Playing it safe for now.
        u32 bss_page_size = (exheader_header.codeset_info.bss_size + 0xFFF) & ~0xFFF;
        code.resize(code.size() + bss_page_size, 0);

        codeset->data.offset = codeset->rodata.offset + codeset->rodata.size;
        codeset->data.addr = exheader_header.codeset_info.data.address;
        codeset->data.size = exheader_header.codeset_info.data.num_max_pages * Memory::PAGE_SIZE + bss_page_size;

        codeset->entrypoint = codeset->code.addr;
        codeset->memory = std::make_shared<std::vector<u8>>(std::move(code));

        Kernel::g_current_process = Kernel::Process::Create(std::move(codeset));

        // Attach a resource limit to the process based on the resource limit category
        Kernel::g_current_process->resource_limit = Kernel::ResourceLimit::GetForCategory(
            static_cast<Kernel::ResourceLimitCategory>(exheader_header.arm11_system_local_caps.resource_limit_category));

        // Copy data while converting endianess
        std::array<u32, ARRAY_SIZE(exheader_header.arm11_kernel_caps.descriptors)> kernel_caps;
        std::copy_n(exheader_header.arm11_kernel_caps.descriptors, kernel_caps.size(), begin(kernel_caps));
        Kernel::g_current_process->ParseKernelCaps(kernel_caps.data(), kernel_caps.size());

        s32 priority = exheader_header.arm11_system_local_caps.priority;
        u32 stack_size = exheader_header.codeset_info.stack_size;
        Kernel::g_current_process->Run(priority, stack_size);
        return ResultStatus::Success;
    }
    return ResultStatus::Error;
}

ResultStatus AppLoader_NCCH::LoadSectionExeFS(const char* name, std::vector<u8>& buffer) {
    if (!file.IsOpen())
        return ResultStatus::Error;

    LOG_DEBUG(Loader, "%d sections:", kMaxSections);
    // Iterate through the ExeFs archive until we find a section with the specified name...
    for (unsigned section_number = 0; section_number < kMaxSections; section_number++) {
        const auto& section = exefs_header.section[section_number];

        // Load the specified section...
        if (strcmp(section.name, name) == 0) {
            LOG_DEBUG(Loader, "%d - offset: 0x%08X, size: 0x%08X, name: %s", section_number,
                      section.offset, section.size, section.name);

            s64 section_offset = (section.offset + exefs_offset + sizeof(ExeFs_Header) + ncch_offset);
            file.Seek(section_offset, SEEK_SET);

            if (strcmp(section.name, ".code") == 0 && is_compressed) {
                // Section is compressed, read compressed .code section...
                std::unique_ptr<u8[]> temp_buffer;
                try {
                    temp_buffer.reset(new u8[section.size]);
                } catch (std::bad_alloc&) {
                    return ResultStatus::ErrorMemoryAllocationFailed;
                }

                if (file.ReadBytes(&temp_buffer[0], section.size) != section.size)
                    return ResultStatus::Error;

                // Decompress .code section...
                u32 decompressed_size = LZSS_GetDecompressedSize(&temp_buffer[0], section.size);
                buffer.resize(decompressed_size);
                if (!LZSS_Decompress(&temp_buffer[0], section.size, &buffer[0], decompressed_size))
                    return ResultStatus::ErrorInvalidFormat;
            } else {
                // Section is uncompressed...
                buffer.resize(section.size);
                if (file.ReadBytes(&buffer[0], section.size) != section.size)
                    return ResultStatus::Error;
            }
            return ResultStatus::Success;
        }
    }
    return ResultStatus::ErrorNotUsed;
}

ResultStatus AppLoader_NCCH::Load() {
    if (is_loaded)
        return ResultStatus::ErrorAlreadyLoaded;

    if (!file.IsOpen())
        return ResultStatus::Error;

    // Reset read pointer in case this file has been read before.
    file.Seek(0, SEEK_SET);

    if (file.ReadBytes(&ncch_header, sizeof(NCCH_Header)) != sizeof(NCCH_Header))
        return ResultStatus::Error;

    // Skip NCSD header and load first NCCH (NCSD is just a container of NCCH files)...
    if (MakeMagic('N', 'C', 'S', 'D') == ncch_header.magic) {
        LOG_WARNING(Loader, "Only loading the first (bootable) NCCH within the NCSD file!");
        ncch_offset = 0x4000;
        file.Seek(ncch_offset, SEEK_SET);
        file.ReadBytes(&ncch_header, sizeof(NCCH_Header));
    }

    // Verify we are loading the correct file type...
    if (MakeMagic('N', 'C', 'C', 'H') != ncch_header.magic)
        return ResultStatus::ErrorInvalidFormat;

    // Read ExHeader...

    if (file.ReadBytes(&exheader_header, sizeof(ExHeader_Header)) != sizeof(ExHeader_Header))
        return ResultStatus::Error;

    is_compressed           = (exheader_header.codeset_info.flags.flag & 1) == 1;
    entry_point             = exheader_header.codeset_info.text.address;
    code_size               = exheader_header.codeset_info.text.code_size;
    stack_size              = exheader_header.codeset_info.stack_size;
    bss_size                = exheader_header.codeset_info.bss_size;
    core_version            = exheader_header.arm11_system_local_caps.core_version;
    priority                = exheader_header.arm11_system_local_caps.priority;
    resource_limit_category = exheader_header.arm11_system_local_caps.resource_limit_category;

    LOG_INFO(Loader,  "Name:                        %s"    , exheader_header.codeset_info.name);
    LOG_INFO(Loader,  "Program ID:                  %016llX" , ncch_header.program_id);
    LOG_DEBUG(Loader, "Code compressed:             %s"    , is_compressed ? "yes" : "no");
    LOG_DEBUG(Loader, "Entry point:                 0x%08X", entry_point);
    LOG_DEBUG(Loader, "Code size:                   0x%08X", code_size);
    LOG_DEBUG(Loader, "Stack size:                  0x%08X", stack_size);
    LOG_DEBUG(Loader, "Bss size:                    0x%08X", bss_size);
    LOG_DEBUG(Loader, "Core version:                %d"    , core_version);
    LOG_DEBUG(Loader, "Thread priority:             0x%X"  , priority);
    LOG_DEBUG(Loader, "Resource limit category:     %d"    , resource_limit_category);

    if (exheader_header.arm11_system_local_caps.program_id != ncch_header.program_id) {
        LOG_ERROR(Loader, "ExHeader Program ID mismatch: the ROM is probably encrypted.");
        return ResultStatus::ErrorEncrypted;
    }

    // Read ExeFS...

    exefs_offset = ncch_header.exefs_offset * kBlockSize;
    u32 exefs_size = ncch_header.exefs_size * kBlockSize;

    LOG_DEBUG(Loader, "ExeFS offset:                0x%08X", exefs_offset);
    LOG_DEBUG(Loader, "ExeFS size:                  0x%08X", exefs_size);

    file.Seek(exefs_offset + ncch_offset, SEEK_SET);
    if (file.ReadBytes(&exefs_header, sizeof(ExeFs_Header)) != sizeof(ExeFs_Header))
        return ResultStatus::Error;

    is_loaded = true; // Set state to loaded

    return LoadExec(); // Load the executable into memory for booting
}

ResultStatus AppLoader_NCCH::ReadCode(std::vector<u8>& buffer) {
    return LoadSectionExeFS(".code", buffer);
}

ResultStatus AppLoader_NCCH::ReadIcon(std::vector<u8>& buffer) {
    return LoadSectionExeFS("icon", buffer);
}

ResultStatus AppLoader_NCCH::ReadBanner(std::vector<u8>& buffer) {
    return LoadSectionExeFS("banner", buffer);
}

ResultStatus AppLoader_NCCH::ReadLogo(std::vector<u8>& buffer) {
    return LoadSectionExeFS("logo", buffer);
}

ResultStatus AppLoader_NCCH::ReadRomFS(std::shared_ptr<FileUtil::IOFile>& romfs_file, u64& offset, u64& size) {
    if (!file.IsOpen())
        return ResultStatus::Error;

    // Check if the NCCH has a RomFS...
    if (ncch_header.romfs_offset != 0 && ncch_header.romfs_size != 0) {
        u32 romfs_offset = ncch_offset + (ncch_header.romfs_offset * kBlockSize) + 0x1000;
        u32 romfs_size = (ncch_header.romfs_size * kBlockSize) - 0x1000;

        LOG_DEBUG(Loader, "RomFS offset:           0x%08X", romfs_offset);
        LOG_DEBUG(Loader, "RomFS size:             0x%08X", romfs_size);

        if (file.GetSize () < romfs_offset + romfs_size)
            return ResultStatus::Error;

        // We reopen the file, to allow its position to be independent from file's
        romfs_file = std::make_shared<FileUtil::IOFile>(filepath, "rb");
        if (!romfs_file->IsOpen())
            return ResultStatus::Error;

        offset = romfs_offset;
        size = romfs_size;

        return ResultStatus::Success;
    }
    LOG_DEBUG(Loader, "NCCH has no RomFS");
    return ResultStatus::ErrorNotUsed;
}

} // namespace Loader
