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

#include <sstream>
#include "common/assert.h"
#include "common/hex_util.h"
#include "common/swap.h"
#include "core/file_sys/ips_layer.h"
#include "core/file_sys/vfs_vector.h"

namespace FileSys {

enum class IPSFileType {
    IPS,
    IPS32,
    Error,
};

static IPSFileType IdentifyMagic(const std::vector<u8>& magic) {
    if (magic.size() != 5)
        return IPSFileType::Error;
    if (magic == std::vector<u8>{'P', 'A', 'T', 'C', 'H'})
        return IPSFileType::IPS;
    if (magic == std::vector<u8>{'I', 'P', 'S', '3', '2'})
        return IPSFileType::IPS32;
    return IPSFileType::Error;
}

VirtualFile PatchIPS(const VirtualFile& in, const VirtualFile& ips) {
    if (in == nullptr || ips == nullptr)
        return nullptr;

    const auto type = IdentifyMagic(ips->ReadBytes(0x5));
    if (type == IPSFileType::Error)
        return nullptr;

    auto in_data = in->ReadAllBytes();

    std::vector<u8> temp(type == IPSFileType::IPS ? 3 : 4);
    u64 offset = 5; // After header
    while (ips->Read(temp.data(), temp.size(), offset) == temp.size()) {
        offset += temp.size();
        if (type == IPSFileType::IPS32 && temp == std::vector<u8>{'E', 'E', 'O', 'F'} ||
            type == IPSFileType::IPS && temp == std::vector<u8>{'E', 'O', 'F'}) {
            break;
        }

        u32 real_offset{};
        if (type == IPSFileType::IPS32)
            real_offset = (temp[0] << 24) | (temp[1] << 16) | (temp[2] << 8) | temp[3];
        else
            real_offset = (temp[0] << 16) | (temp[1] << 8) | temp[2];

        u16 data_size{};
        if (ips->ReadObject(&data_size, offset) != sizeof(u16))
            return nullptr;
        data_size = Common::swap16(data_size);
        offset += sizeof(u16);

        if (data_size == 0) { // RLE
            u16 rle_size{};
            if (ips->ReadObject(&rle_size, offset) != sizeof(u16))
                return nullptr;
            rle_size = Common::swap16(data_size);
            offset += sizeof(u16);

            const auto data = ips->ReadByte(offset++);
            if (data == boost::none)
                return nullptr;

            if (real_offset + rle_size > in_data.size())
                rle_size = in_data.size() - real_offset;
            std::memset(in_data.data() + real_offset, data.get(), rle_size);
        } else { // Standard Patch
            auto read = data_size;
            if (real_offset + read > in_data.size())
                read = in_data.size() - real_offset;
            if (ips->Read(in_data.data() + real_offset, read, offset) != data_size)
                return nullptr;
            offset += data_size;
        }
    }

    if (temp != std::vector<u8>{'E', 'E', 'O', 'F'} && temp != std::vector<u8>{'E', 'O', 'F'})
        return nullptr;
    return std::make_shared<VectorVfsFile>(in_data, in->GetName(), in->GetContainingDirectory());
}

IPSwitchCompiler::IPSwitchCompiler(VirtualFile patch_text_)
    : valid(false), patch_text(std::move(patch_text_)), nso_build_id{}, is_little_endian(false),
      offset_shift(0), print_values(false) {
    Parse();
}

std::array<u8, 32> IPSwitchCompiler::GetBuildID() const {
    return nso_build_id;
}

bool IPSwitchCompiler::IsValid() const {
    return valid;
}

static bool StartsWith(const std::string& base, const std::string& check) {
    return base.size() >= check.size() && base.substr(0, check.size()) == check;
}

void IPSwitchCompiler::Parse() {
    const auto bytes = patch_text->ReadAllBytes();
    std::stringstream s;
    s.write(reinterpret_cast<const char*>(bytes.data()), bytes.size());

    std::vector<std::string> lines;
    std::string line;
    while (std::getline(s, line)) {
        // Remove a trailing \r
        if (!line.empty() && line[line.size() - 1] == '\r')
            line = line.substr(0, line.size() - 1);
        lines.push_back(line);
    }

    for (std::size_t i = 0; i < lines.size(); ++i) {
        auto line = lines[i];
        if (StartsWith(line, "@stop")) {
            // Force stop
            break;
        } else if (StartsWith(line, "@nsobid-")) {
            // NSO Build ID Specifier
            auto raw_build_id = line.substr(8);
            if (raw_build_id.size() != 0x40)
                raw_build_id.resize(0x40, '0');
            nso_build_id = Common::HexStringToArray<0x20>(raw_build_id);
        } else if (StartsWith(line, "@flag offset_shift ")) {
            // Offset Shift Flag
            offset_shift = std::stoull(line.substr(19), nullptr, 0);
        } else if (StartsWith(line, "#")) {
            // Mandatory Comment
            LOG_INFO(Loader, "[IPSwitchCompiler ('{}')] Forced output comment: {}",
                     patch_text->GetName(), line.substr(1));
        } else if (StartsWith(line, "@little-endian")) {
            // Set values to read as little endian
            is_little_endian = true;
        } else if (StartsWith(line, "@big-endian")) {
            // Set values to read as big endian
            is_little_endian = false;
        } else if (StartsWith(line, "@flag print_values")) {
            // Force printing of applied values
            print_values = true;
        } else if (StartsWith(line, "@enabled") || StartsWith(line, "@disabled")) {
            // Start of patch
            const auto enabled = StartsWith(line, "@enabled");
            if (i == 0)
                return;
            const auto name = lines[i - 1].substr(3);
            LOG_INFO(Loader, "[IPSwitchCompiler ('{}')] Parsing patch '{}' ({})",
                     patch_text->GetName(), name, line.substr(1));

            IPSwitchPatch patch{name, enabled, {}};

            // Read rest of patch
            while (true) {
                if (i + 1 >= lines.size())
                    break;
                line = lines[++i];

                // 11 - 8 hex digit offset + space + minimum two digit overwrite val
                if (line.length() < 11)
                    break;
                auto offset = std::stoul(line.substr(0, 8), nullptr, 16);
                offset += offset_shift;

                std::vector<u8> replace;
                // 9 - first char of replacement val
                if (line[9] == '\"') {
                    // string replacement
                    const auto end_index = line.find_last_of('\"');
                    if (end_index == std::string::npos || end_index < 10)
                        return;
                    const auto value = line.substr(10, end_index - 10);
                    replace.reserve(value.size());
                    std::copy(value.begin(), value.end(), std::back_inserter(replace));
                } else {
                    // hex replacement
                    const auto value = line.substr(9);
                    replace.reserve(value.size() / 2);
                    replace = Common::HexStringToVector(value, is_little_endian);
                }

                if (print_values) {
                    LOG_INFO(Loader,
                             "[IPSwitchCompiler ('{}')]     - Patching value at offset 0x{:08X} "
                             "with byte string '{}'",
                             patch_text->GetName(), offset, Common::HexVectorToString(replace));
                }

                patch.records.emplace(offset, replace);
            }

            patches.push_back(std::move(patch));
        }
    }

    valid = true;
}

VirtualFile IPSwitchCompiler::Apply(const VirtualFile& in) const {
    if (in == nullptr || !valid)
        return nullptr;

    auto in_data = in->ReadAllBytes();

    for (const auto& patch : patches) {
        if (!patch.enabled)
            continue;

        for (const auto& record : patch.records) {
            if (record.first >= in_data.size())
                continue;
            auto replace_size = record.second.size();
            if (record.first + replace_size > in_data.size())
                replace_size = in_data.size() - record.first;
            for (std::size_t i = 0; i < replace_size; ++i)
                in_data[i + record.first] = record.second[i];
        }
    }

    return std::make_shared<VectorVfsFile>(in_data, in->GetName(), in->GetContainingDirectory());
}

} // namespace FileSys