// Copyright 2022, FOSS-VG Developers and Contributers
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, version 3.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// version 3 along with this program.
// If not, see https://www.gnu.org/licenses/agpl-3.0.en.html

#include <bit>
#include <cstdint>
#include <vector>

#include "nbt.h++"
#include "error.h++"

#include "../../.endianness"
#ifdef FOSSVG_ENDIAN_BIG_WORD
    #error "Honeywell-316-style endianness is not supported. If you feel like it should, feel free to participate in the project to maintain it."
#endif
#ifdef FOSSVG_ENDIAN_LITTLE_WORD
    #error "PDP-11-style endianness is not supported. If you feel like it should, feel free to participate in the project to maintain it."
#endif
#ifdef FOSSVG_ENDIAN_UNKNOWN
    #error "The endianness of your system could not be determined. Please set it manually. FOSS-VG is currently implemented using some endian-specific functions."
#endif

namespace NBT {
    namespace helper {
        ErrorOr<int8_t> readInt8(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            if (dataSize<currentPosition+1) return ErrorOr<int8_t>(true, ErrorCodes::RANGE_ERROR);
            return ErrorOr<int8_t>((int8_t) data[currentPosition]);
        }

        ErrorOr<int16_t> readInt16(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            if (dataSize<currentPosition+2) return ErrorOr<int16_t>(true, ErrorCodes::RANGE_ERROR);
            return ErrorOr<int16_t>((int16_t) ((static_cast<int16_t>(data[currentPosition]) << 8) | static_cast<int16_t>(data[currentPosition+1])));
        }

        ErrorOr<int32_t> readInt32(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            if (dataSize<currentPosition+4) return ErrorOr<int32_t>(true, ErrorCodes::RANGE_ERROR);
            return ErrorOr<int32_t>((int32_t) (
                (static_cast<int32_t>(data[currentPosition  ]) << 24) |
                (static_cast<int32_t>(data[currentPosition+1]) << 16) |
                (static_cast<int32_t>(data[currentPosition+2]) <<  8) |
                 static_cast<int32_t>(data[currentPosition+3])
            ));
        }

        ErrorOr<int64_t> readInt64(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            if (dataSize<currentPosition+8) return ErrorOr<int64_t>(true, ErrorCodes::RANGE_ERROR);
            return ErrorOr<int64_t>((int64_t) (
                (static_cast<int64_t>(data[currentPosition  ]) << 56) |
                (static_cast<int64_t>(data[currentPosition+1]) << 48) |
                (static_cast<int64_t>(data[currentPosition+2]) << 40) |
                (static_cast<int64_t>(data[currentPosition+3]) << 32) |
                (static_cast<int64_t>(data[currentPosition+4]) << 24) |
                (static_cast<int64_t>(data[currentPosition+5]) << 16) |
                (static_cast<int64_t>(data[currentPosition+6]) <<  8) |
                 static_cast<int64_t>(data[currentPosition+7])
            ));
        }

        //FIXME: we just assume that float is a single-precision IEEE754
        // floating point number, also we are using endian-dependent
        // implementations
        ErrorOr<float> readFloat32(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            float* value = new float;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            if (dataSize<=currentPosition) return ErrorOr<float>(true, ErrorCodes::RANGE_ERROR);
            if (dataSize<currentPosition+4) return ErrorOr<float>(true, ErrorCodes::OVERRUN_ERROR);
            #ifdef FOSSVG_BIG_ENDIAN
                *valueAsBytes   =   data[currentPosition];
                *(valueAsBytes+1) = data[currentPosition+1];
                *(valueAsBytes+2) = data[currentPosition+2];
                *(valueAsBytes+3) = data[currentPosition+3];
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    *valueAsBytes   =   data[currentPosition+3];
                    *(valueAsBytes+1) = data[currentPosition+2];
                    *(valueAsBytes+2) = data[currentPosition+1];
                    *(valueAsBytes+3) = data[currentPosition];
                #else
                    #error "NBT::helper::readFloat32: An implementation for your endianness is unavailable."
                #endif
            #endif
            float dereferencedValue = *value;
            delete value;
            return ErrorOr<float>(dereferencedValue);
        }

        //FIXME: we just assume that double is a double-precision IEEE754
        // floating point number, also we are using endian-dependent
        // implementations
        ErrorOr<double> readFloat64(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            double* value = new double;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            if (dataSize<=currentPosition) return ErrorOr<double>(true, ErrorCodes::RANGE_ERROR);
            if (dataSize<currentPosition+8) return ErrorOr<double>(true, ErrorCodes::OVERRUN_ERROR);
            #ifdef FOSSVG_BIG_ENDIAN
                *valueAsBytes   =   data[currentPosition];
                *(valueAsBytes+1) = data[currentPosition+1];
                *(valueAsBytes+2) = data[currentPosition+2];
                *(valueAsBytes+3) = data[currentPosition+3];
                *(valueAsBytes+4) = data[currentPosition+4];
                *(valueAsBytes+5) = data[currentPosition+5];
                *(valueAsBytes+6) = data[currentPosition+6];
                *(valueAsBytes+7) = data[currentPosition+7];
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    *valueAsBytes   =   data[currentPosition+7];
                    *(valueAsBytes+1) = data[currentPosition+6];
                    *(valueAsBytes+2) = data[currentPosition+5];
                    *(valueAsBytes+3) = data[currentPosition+4];
                    *(valueAsBytes+4) = data[currentPosition+3];
                    *(valueAsBytes+5) = data[currentPosition+2];
                    *(valueAsBytes+6) = data[currentPosition+1];
                    *(valueAsBytes+7) = data[currentPosition];
                #else
                    #error "NBT::helper::readFloat64: An implementation for your endianness is unavailable."
                #endif
            #endif
            double dereferencedValue = *value;
            delete value;
            return ErrorOr<double>(dereferencedValue);
        }

        ErrorOr<std::vector<int8_t>> readInt8Array(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            // get size prefix
            ErrorOr<int32_t> size = readInt32(data, dataSize, currentPosition);
            if (size.isError) return ErrorOr<std::vector<int8_t>>(true, size.errorCode);

            // get content
            if (currentPosition+4+size.value > dataSize) return ErrorOr<std::vector<int8_t>>(true, ErrorCodes::OVERRUN_ERROR);
            std::vector<int8_t> result = std::vector<int8_t>();
            for (int i=0; i<size.value; i++) {
                result.push_back(data[currentPosition+4+i]);
            }
            return ErrorOr<std::vector<int8_t>>(result);
        }

        // Maybe use a struct that holds decoded (de-Java-fied) string
        // data, decoded size, and original size? Original size is needed
        // so the parser knows where to continue.
        //ErrorOr<> readString(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            //TODO: implement
            // return ErrorOr<>("");
        //}

        ErrorOr<std::vector<int32_t>> readInt32Array(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            // get size prefix
            ErrorOr<int32_t> size = readInt32(data, dataSize, currentPosition);
            if (size.isError) return ErrorOr<std::vector<int32_t>>(true, size.errorCode);

            // get content
            if (currentPosition+4+(size.value*4) > dataSize) return ErrorOr<std::vector<int32_t>>(true, ErrorCodes::OVERRUN_ERROR);
            std::vector<int32_t> result = std::vector<int32_t>();
            for (int i=0; i<size.value; i++) {
                ErrorOr<int32_t> nextInt32 = readInt32(data, dataSize, currentPosition+4+(i*4));
                if (nextInt32.isError) return ErrorOr<std::vector<int32_t>>(true, nextInt32.errorCode);
                result.push_back(nextInt32.value);
            }
            return ErrorOr<std::vector<int32_t>>(result);
        }

        ErrorOr<std::vector<int64_t>> readInt64Array(uint8_t data[], uint64_t dataSize, uint64_t currentPosition) {
            // get size prefix
            ErrorOr<int32_t> size = readInt32(data, dataSize, currentPosition);
            if (size.isError) return ErrorOr<std::vector<int64_t>>(true, size.errorCode);

            // get content
            if (currentPosition+4+(size.value*8) > dataSize) return ErrorOr<std::vector<int64_t>>(true, ErrorCodes::OVERRUN_ERROR);
            std::vector<int64_t> result = std::vector<int64_t>();
            for (int i=0; i<size.value; i++) {
                ErrorOr<int64_t> nextInt64 = readInt64(data, dataSize, currentPosition+4+(i*8));
                if (nextInt64.isError) return ErrorOr<std::vector<int64_t>>(true, nextInt64.errorCode);
                result.push_back(nextInt64.value);
            }
            return ErrorOr<std::vector<int64_t>>(result);
        }

        void writeInt8(std::vector<uint8_t>* destination, int8_t data) {
            destination->push_back((uint8_t) data);
        }

        //FIXME: endian dependent implementation
        void writeInt16(std::vector<uint8_t>* destination, int16_t data) {
            int16_t* value = new int16_t;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            *value = data;
            #ifdef FOSSVG_BIG_ENDIAN
                destination->push_back(*valueAsBytes);
                destination->push_back(*(valueAsBytes+1));
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    destination->push_back(*(valueAsBytes+1));
                    destination->push_back(*valueAsBytes);
                #else
                    #error "NBT::helper::writeInt16: An implementation for your endianness is unavailable."
                #endif
            #endif
            delete value;
        }

        //FIXME: endian dependent implementation
        void writeInt32(std::vector<uint8_t>* destination, int32_t data) {
            int32_t* value = new int32_t;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            *value = data;
            #ifdef FOSSVG_BIG_ENDIAN
                destination->push_back(*valueAsBytes);
                destination->push_back(*(valueAsBytes+1));
                destination->push_back(*(valueAsBytes+2));
                destination->push_back(*(valueAsBytes+3));
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    destination->push_back(*(valueAsBytes+3));
                    destination->push_back(*(valueAsBytes+2));
                    destination->push_back(*(valueAsBytes+1));
                    destination->push_back(*valueAsBytes);
                #else
                    #error "NBT::helper::writeInt16: An implementation for your endianness is unavailable."
                #endif
            #endif
            delete value;
        }

        //FIXME: endian dependent implementation
        void writeInt64(std::vector<uint8_t>* destination, int64_t data) {
            int64_t* value = new int64_t;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            *value = data;
            #ifdef FOSSVG_BIG_ENDIAN
                destination->push_back(*valueAsBytes);
                destination->push_back(*(valueAsBytes+1));
                destination->push_back(*(valueAsBytes+2));
                destination->push_back(*(valueAsBytes+3));
                destination->push_back(*(valueAsBytes+4));
                destination->push_back(*(valueAsBytes+5));
                destination->push_back(*(valueAsBytes+6));
                destination->push_back(*(valueAsBytes+7));
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    destination->push_back(*(valueAsBytes+7));
                    destination->push_back(*(valueAsBytes+6));
                    destination->push_back(*(valueAsBytes+5));
                    destination->push_back(*(valueAsBytes+4));
                    destination->push_back(*(valueAsBytes+3));
                    destination->push_back(*(valueAsBytes+2));
                    destination->push_back(*(valueAsBytes+1));
                    destination->push_back(*valueAsBytes);
                #else
                    #error "NBT::helper::writeInt16: An implementation for your endianness is unavailable."
                #endif
            #endif
            delete value;
        }

        //FIXME: we just assume that float is a single-precision IEEE754
        // floating point number, also endian specific implementation
        void writeFloat32(std::vector<uint8_t>* destination, float data) {
            float* value = new float;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            *value = data;
            #ifdef FOSSVG_BIG_ENDIAN
                destination->push_back(*valueAsBytes);
                destination->push_back(*(valueAsBytes+1));
                destination->push_back(*(valueAsBytes+2));
                destination->push_back(*(valueAsBytes+3));
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    destination->push_back(*(valueAsBytes+3));
                    destination->push_back(*(valueAsBytes+2));
                    destination->push_back(*(valueAsBytes+1));
                    destination->push_back(*valueAsBytes);
                #else
                    #error "NBT::helper::writeInt16: An implementation for your endianness is unavailable."
                #endif
            #endif
            delete value;
        }

        //FIXME: we just assume that double is a single-precision IEEE754
        // floating point number, also endian specific implementation
        void writeFloat64(std::vector<uint8_t>* destination, double data) {
            double* value = new double;
            uint8_t* valueAsBytes = reinterpret_cast<uint8_t*>(value);
            *value = data;
            #ifdef FOSSVG_BIG_ENDIAN
                destination->push_back(*valueAsBytes);
                destination->push_back(*(valueAsBytes+1));
                destination->push_back(*(valueAsBytes+2));
                destination->push_back(*(valueAsBytes+3));
                destination->push_back(*(valueAsBytes+4));
                destination->push_back(*(valueAsBytes+5));
                destination->push_back(*(valueAsBytes+6));
                destination->push_back(*(valueAsBytes+7));
            #else
                #ifdef FOSSVG_LITTLE_ENDIAN
                    destination->push_back(*(valueAsBytes+7));
                    destination->push_back(*(valueAsBytes+6));
                    destination->push_back(*(valueAsBytes+5));
                    destination->push_back(*(valueAsBytes+4));
                    destination->push_back(*(valueAsBytes+3));
                    destination->push_back(*(valueAsBytes+2));
                    destination->push_back(*(valueAsBytes+1));
                    destination->push_back(*valueAsBytes);
                #else
                    #error "NBT::helper::writeInt16: An implementation for your endianness is unavailable."
                #endif
            #endif
            delete value;
        }

        void writeInt8Array(std::vector<uint8_t>* destination, std::vector<int8_t> data) {
        }

        void writeInt8Array(std::vector<uint8_t>* destination, int8_t data[], uint64_t dataSize) {
        }

        //void writeString(std::vector<uint8_t>* destination, <string type> data) {
        //}

        void writeInt32Array(std::vector<uint8_t>* destination, std::vector<int32_t> data) {
        }

        void writeInt32Array(std::vector<uint8_t>* destination, int32_t data[], uint64_t dataSize) {
        }

        void writeInt64Array(std::vector<uint8_t>* destination, std::vector<int64_t> data) {
        }

        void writeInt64Array(std::vector<uint8_t>* destination, int64_t data[], uint64_t dataSize) {
        }
    }

    bool validateRawNBTData(uint8_t data[], uint64_t dataSize){
        //state machine?
        //TODO: implement
        return false;
    }
}