#include "piezoresistive_a_protocol.h"

#include <QDateTime>
#include <qcontainerfwd.h>
#include <qtypes.h>

namespace {
constexpr quint8 kReplyStart0 = 0x55; // 0x55AA little-endian
constexpr quint8 kReplyStart1 = 0xAA;
constexpr quint8 kReplyStartAlt0 = 0xAA;
constexpr quint8 kReplyStartAlt1 = 0x55;
constexpr quint8 kRequestStart0 = 0x55; // 0x55AA little-endian
constexpr quint8 kRequestStart1 = 0xAA;

quint16 readLe16(const QByteArray& data, int offset) {
    const quint8 b0 = static_cast<quint8>(data[offset]);
    const quint8 b1 = static_cast<quint8>(data[offset + 1]);
    return static_cast<quint16>(b0 | (b1 << 8));
}

quint32 readLe32(const QByteArray& data, int offset) {
    const quint8 b0 = static_cast<quint8>(data[offset]);
    const quint8 b1 = static_cast<quint8>(data[offset + 1]);
    const quint8 b2 = static_cast<quint8>(data[offset + 2]);
    const quint8 b3 = static_cast<quint8>(data[offset + 3]);
    return static_cast<quint32>(b0 | (b1 << 8) | (b2 << 16) | (b3 << 24));
}

void appendLe16(QByteArray& data, quint16 v) {
    data.append(static_cast<char>(v & 0xFF));
    data.append(static_cast<char>((v >> 8) & 0xFF));
}

void appendLe32(QByteArray& data, quint32 v) {
    data.append(static_cast<char>(v & 0xFF));
    data.append(static_cast<char>((v >> 8) & 0xFF));
    data.append(static_cast<char>((v >> 16) & 0xFF));
    data.append(static_cast<char>((v >> 24) & 0xFF));
}
}

quint8 PiezoresistiveAFormat::crc8ITU(const QByteArray& data, int length) {
    quint8 crc = 0x00;
    const int limit = qMin(length, data.size());
    for (int i = 0; i < limit; ++i) {
        crc ^= static_cast<quint8>(data[i]);
        for (int bit = 0; bit < 8; ++bit) {
            if (crc & 0x80)
                crc = static_cast<quint8>((crc << 1) ^ 0x07);
            else
                crc = static_cast<quint8>(crc << 1);
        }
    }
    return static_cast<quint8>(crc ^ 0x55);
}

ISerialFormat::ParseResult PiezoresistiveAFormat::tryParse(QByteArray* buffer, QByteArray* packet, QString* error) {
    if (!buffer || buffer->isEmpty())
        return ParseResult::NeedMore;

    int startIndex = -1;
    for (int i = 0; i + 1 < buffer->size(); ++i) {
        if (static_cast<quint8>((*buffer)[i]) == kReplyStart0 &&
            static_cast<quint8>((*buffer)[i + 1]) == kReplyStart1) {
            startIndex = i;
            break;
        }
        if (static_cast<quint8>((*buffer)[i]) == kReplyStartAlt0 &&
            static_cast<quint8>((*buffer)[i + 1]) == kReplyStartAlt1) {
            startIndex = i;
            break;
        }
    }

    if (startIndex < 0) {
        const quint8 tail = static_cast<quint8>(buffer->back());
        buffer->clear();
        if (tail == kReplyStart0 || tail == kReplyStart1)
            buffer->append(static_cast<char>(tail));
        return ParseResult::NeedMore;
    }

    if (startIndex > 0)
        buffer->remove(0, startIndex);

    if (buffer->size() < 5)
        return ParseResult::NeedMore;

    const quint16 payloadLen = readLe16(*buffer, 2);
    const int totalLen = 4 + payloadLen + 1;
    if (buffer->size() < totalLen)
        return ParseResult::NeedMore;

    QByteArray candidate = buffer->left(totalLen);
    buffer->remove(0, totalLen);

    const quint8 crc = static_cast<quint8>(candidate.at(candidate.size() - 1));
    const quint8 calc = crc8ITU(candidate, candidate.size() - 1);
    if (crc != calc) {
        if (error)
            *error = QStringLiteral("CRC mismatch");
        return ParseResult::Invalid;
    }

    if (packet)
        *packet = candidate;
    if (error)
        error->clear();
    return ParseResult::Ok;
}

QByteArray PiezoresistiveACodec::buildRequest(const SerialConfig& config, const SensorRequest& request) {
    QByteArray packet;
    packet.reserve(15);

    packet.append(static_cast<char>(kRequestStart0));
    packet.append(static_cast<char>(kRequestStart1));

    const quint16 payloadLen = 9;
    appendLe16(packet, payloadLen);

    packet.append(static_cast<char>(config.deviceAddress));
    packet.append(static_cast<char>(0x00));
    packet.append(static_cast<char>(0x80 | request.functionCode));

    appendLe32(packet, request.startAddress);
    appendLe16(packet, request.dataLength);

    const quint8 crc = PiezoresistiveAFormat::crc8ITU(packet, packet.size());
    packet.append(static_cast<char>(crc));

    return packet;
}

QByteArray PiezoresistiveACodec::buildGetVersionRequest(const SerialConfig& config) {
    // TODO:待实现内容(压阻 A 型版本号查询请求帧)
    Q_UNUSED(config)
    return QByteArray();
}

QByteArray PiezoresistiveACodec::buildGetSpecRequest(const SerialConfig& config) {
    // TODO:待实现内容(压阻 A 型规格查询请求帧)
    Q_UNUSED(config)
    return QByteArray();
}

bool PiezoresistiveADecoder::decodeFrame(const QByteArray& packet, DataFrame* frame, QString* error) {
    if (!frame) {
        if (error)
            *error = QStringLiteral("Null frame output");
        return false;
    }

    if (packet.size() < 15) {
        if (error)
            *error = QStringLiteral("Packet too short");
        return false;
    }

    const quint8 start0 = static_cast<quint8>(packet[0]);
    const quint8 start1 = static_cast<quint8>(packet[1]);
    const bool startOk = (start0 == kReplyStart0 && start1 == kReplyStart1) ||
        (start0 == kReplyStartAlt0 && start1 == kReplyStartAlt1);
    if (!startOk) {
        if (error)
            *error = QStringLiteral("Bad start bytes");
        return false;
    }

    const quint16 payloadLen = readLe16(packet, 2);
    const int totalLen = 4 + payloadLen + 1;
    if (packet.size() != totalLen) {
        if (error)
            *error = QStringLiteral("Length mismatch");
        return false;
    }

    const quint8 crc = static_cast<quint8>(packet.at(packet.size() - 1));
    const quint8 calc = PiezoresistiveAFormat::crc8ITU(packet, packet.size() - 1);
    if (crc != calc) {
        if (error)
            *error = QStringLiteral("CRC mismatch");
        return false;
    }

    const quint8 funcRaw = static_cast<quint8>(packet[6]);
    const quint16 dataLen = readLe16(packet, 11);
    const quint8 status = static_cast<quint8>(packet[13]);

    if (payloadLen != static_cast<quint16>(10 + dataLen)) {
        if (error)
            *error = QStringLiteral("Payload length mismatch");
        return false;
    }

    if (status != 0) {
        if (error)
            *error = QStringLiteral("Device status error");
        return false;
    }

    if (packet.size() < 15 + dataLen) {
        if (error)
            *error = QStringLiteral("Data length mismatch");
        return false;
    }

    if ((dataLen % 2) != 0) {
        if (error)
            *error = QStringLiteral("Odd data length");
        return false;
    }

    const int sampleCount = dataLen / 2;
    QVector<float> values;
    values.reserve(sampleCount);

    const int dataOffset = 14;
    for (int i = 0; i < sampleCount; ++i) {
        const int offset = dataOffset + i * 2;
        const quint16 raw = readLe16(packet, offset);
        values.push_back(static_cast<float>(raw));
    }

    frame->pts = DataFrame::makePts(QDateTime::currentDateTime());
    frame->functionCode = (funcRaw >= 0x80) ? static_cast<quint8>(funcRaw - 0x80) : funcRaw;
    frame->data = values;

    if (error)
        error->clear();
    return true;
}

bool PiezoresistiveADecoder::decodeSpec(const QByteArray& packet, SensorSpec* spec, QString* error) {
    // TODO:待实现内容(解析压阻 A 型规格回复并写入 SensorSpec)
    Q_UNUSED(packet)
    Q_UNUSED(spec)
    if (error)
        *error = QStringLiteral("Not implemented");
    return false;
}