/* SPDX-License-Identifier: Unlicense
 */

#include "gdbremote_parser.hpp"
#include "utils.hpp"

#include <cctype>
#include <cassert>
#include <cstring>

using namespace GDBRemote;

enum class TokenType: uint8_t {
    kUnknown = 0,
    kSeparatorComma,
    kSeparatorColon,
    kSeparatorSemicolon,
    kSeparatorEquals,
    kHexNumeric,
    kArbitrary,
};

static inline bool isseparator(uint8_t byte)
{
    return ':' == byte || ';' == byte || ',' == byte || '=' == byte;
}

static inline TokenType separatorTypeFromByte(uint8_t byte)
{
    if (':' == byte) return TokenType::kSeparatorColon;
    if (';' == byte) return TokenType::kSeparatorSemicolon;
    if ('=' == byte) return TokenType::kSeparatorEquals;
    return TokenType::kSeparatorComma;
}

struct Token {
    TokenType type{};
    std::string data{};

    static std::vector<Token> Tokenize(
            const std::string& packet_data, const std::string& command)
    {
        if (packet_data.length() == 0) return std::vector<Token>{};
        std::vector<Token> tokens{};
        const size_t cmdlen = command.length();
        if (cmdlen > 0) {
            tokens.push_back(Token{TokenType::kArbitrary, command});
        }
        TokenType type{};
        size_t i{command.length()}, offset{command.length()};
        for (; i < packet_data.length(); i++) {
            assert(type != TokenType::kSeparatorColon);
            assert(type != TokenType::kSeparatorSemicolon);
            assert(type != TokenType::kSeparatorEquals);
            assert(type != TokenType::kSeparatorComma);
            const uint8_t byte = packet_data[i];
            if (isseparator(byte)) {
                if (i > offset) {
                    assert(type != TokenType::kUnknown);
                    tokens.push_back(Token{type, packet_data.substr(offset, i - offset)});
                    offset = i;
                }
                tokens.push_back(Token{
                        separatorTypeFromByte(byte),
                        packet_data.substr(offset, 1),
                        });
                offset++;
                type = TokenType::kUnknown;
            } else if (isxdigit(byte)) {
                if (type != TokenType::kArbitrary) {
                    type = TokenType::kHexNumeric;
                }
            } else {
                type = TokenType::kArbitrary;
            }
        }
        if (i > offset) {
            assert(type != TokenType::kUnknown);
            tokens.push_back(Token{type, packet_data.substr(offset, i - offset)});
        }
        return tokens;
    }
};

static std::string DecodeBinaryHex(const std::string& data_hex)
{
    std::string data(data_hex.size()/2, '\0');
    for (size_t i = 0; i < data.size(); i++) {
        data[i] = Utils::ParseByteFromHexChars(data_hex[i * 2], data_hex[i * 2 + 1]);
    }
    return data;
}

struct Command {
    std::string name;
    Packet (*parse)(std::vector<Token>&&);
    static Packet parseNone(std::vector<Token>&&)
    {
        return Packet::None();
    }
    static Packet parseQuerySupported(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kQuerySupported};
    }
    static Packet parseQueryHaltReason(std::vector<Token>&&)
    {
        return Packet{PacketType::kQueryHaltReason};
    }
    static Packet parseQueryC(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kQueryC};
    }
    static Packet parseQueryFThreadInfo(std::vector<Token>&&)
    {
        return Packet{PacketType::kQueryFThreadInfo};
    }
    static Packet parseQuerySThreadInfo(std::vector<Token>&&)
    {
        return Packet{PacketType::kQuerySThreadInfo};
    }
    static Packet parseQueryRTOSThreadInfo(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kQueryRTOSThreadInfo};
    }
    static Packet parseQueryAttached(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kQueryAttached};
    }
    static Packet parseQueryTraceStatus(std::vector<Token>&&)
    {
        return Packet{PacketType::kQueryTraceStatus};
    }
    static Packet parseQueryRcmd(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 3)
            return Packet::None();
        if (tokens[1].type != TokenType::kSeparatorComma)
            return Packet::None();
        if (tokens[2].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& data_encoded = tokens[2].data;
        return Packet{
            PacketType::kQueryRcmd,
            std::make_unique<const PacketDataRcmd>(std::move(DecodeBinaryHex(data_encoded))),
        };
    }
    static Packet parseQStartNoAckMode(std::vector<Token>&&)
    {
        return Packet{PacketType::kQStartNoAckMode};
    }
    static Packet parseSetThreadForCont(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kSetThreadForCont};
    }
    static Packet parseSetThreadForOps(std::vector<Token>&&)
    {
        // TODO arguments
        return Packet{PacketType::kSetThreadForOps};
    }
    static Packet parseMustReplyEmpty(std::vector<Token>&&)
    {
        return Packet{PacketType::kVMustReplyEmpty};
    }
    static Packet parseEnableExtendedMode(std::vector<Token>&&)
    {
        return Packet{PacketType::kEnableExtendedMode};
    }
    static Packet parseInterrupt(std::vector<Token>&&)
    {
        return Packet{PacketType::kInterrupt};
    }
    static Packet parseContinueVCont(std::vector<Token>&& tokens)
    {
        const std::string first_arg = tokens.size() > 1 ? tokens[1].data : "";
        // Check if it is "vCont?" command
        if (first_arg == "?") {
            return Packet{PacketType::kContinueAskSupported};
        }
        // TODO arguments
        return Packet{PacketType::kContinue};
    }
    static Packet parseContinue(std::vector<Token>&&)
    {
        return Packet{PacketType::kContinue};
    }
    static Packet parseReadMemory(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 4)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        if (tokens[2].type != TokenType::kSeparatorComma)
            return Packet::None();
        if (tokens[3].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& first = tokens[1].data;
        const std::string& second = tokens[3].data;
        // TODO handle number parsing error (ERANGE)
        const uint32_t offset = strtol(first.c_str(), nullptr, 16);
        const uint32_t lenght = strtol(second.c_str(), nullptr, 16);
        return Packet{
            PacketType::kReadMemory,
            std::make_unique<const PacketDataReadMemory>(offset, lenght),
        };
    }
    static Packet parseWriteMemory(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 6)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        if (tokens[2].type != TokenType::kSeparatorComma)
            return Packet::None();
        if (tokens[3].type != TokenType::kHexNumeric)
            return Packet::None();
        // XXX Is data parameter always present or is it optional?
        if (tokens[4].type != TokenType::kSeparatorColon)
            return Packet::None();
        if (tokens[5].type != TokenType::kHexNumeric)
            return Packet::None();
        // TODO handle number parsing error (ERANGE)
        const std::string& first = tokens[1].data;
        const std::string& second = tokens[3].data;
        const std::string& data_raw = tokens[5].data;
        const size_t data_len = data_raw.length()/2;
        std::vector<uint8_t> data(data_len);
        assert(data.size() == data_len);
        for (size_t i = 0; i < data_len; i++) {
            data[i] = Utils::ParseByteFromHexChars(data_raw[i*2], data_raw[i*2+1]);
        }
        const uint32_t offset = strtol(first.c_str(), nullptr, 16);
        const uint32_t lenght = strtol(second.c_str(), nullptr, 16);
        return Packet{
            PacketType::kWriteMemory,
            std::make_unique<const PacketDataWriteMemory>(offset, lenght, std::move(data)),
        };
    }
    static Packet parseReadGeneralRegisters(std::vector<Token>&&)
    {
        return Packet{PacketType::kReadGeneralRegisters};
    }
    static Packet parseWriteGeneralRegisters(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 2)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& first = tokens[1].data;
        constexpr size_t value_str_size = std::string_view("12345678").length();
        std::vector<uint32_t> registers(first.length()/value_str_size);
        for (size_t i = 0; i < first.length()/value_str_size; i++) {
            const std::string value_str(first.substr(i * value_str_size, value_str_size));
            registers[i] = strtol(value_str.c_str(), nullptr, 16);
        }
        return Packet{
            PacketType::kWriteGeneralRegisters,
            std::make_unique<const PacketDataWriteGeneralRegisters>(std::move(registers)),
        };
    }
    static Packet parseReadRegister(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 2)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& first = tokens[1].data;
        const uint32_t reg_id = strtol(first.c_str(), nullptr, 16);
        return Packet{
            PacketType::kReadRegister,
            std::make_unique<const PacketDataReadRegister>(reg_id),
        };
    }
    static Packet parseWriteRegister(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 4)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        if (tokens[2].type != TokenType::kSeparatorEquals)
            return Packet::None();
        if (tokens[3].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& first = tokens[1].data;
        const std::string& second = tokens[3].data;
        const uint32_t reg_id = strtol(first.c_str(), nullptr, 16);
        const uint32_t value = strtol(second.c_str(), nullptr, 16);
        return Packet{
            PacketType::kWriteRegister,
            std::make_unique<const PacketDataWriteRegister>(reg_id, value),
        };
    }
    static Packet parseStep(std::vector<Token>&&)
    {
        return Packet{PacketType::kStep};
    }
    static Packet parseSetOrDeleteBreakpoint(std::vector<Token>&& tokens)
    {
        if (tokens.size() < 6)
            return Packet::None();
        if (tokens[1].type != TokenType::kHexNumeric)
            return Packet::None();
        if (tokens[2].type != TokenType::kSeparatorComma)
            return Packet::None();
        if (tokens[3].type != TokenType::kHexNumeric)
            return Packet::None();
        // XXX Is third parameter always present or is it optional?
        if (tokens[4].type != TokenType::kSeparatorComma)
            return Packet::None();
        if (tokens[5].type != TokenType::kHexNumeric)
            return Packet::None();
        const std::string& first = tokens[1].data;
        const std::string& second = tokens[3].data;
        const std::string& third = tokens[5].data;
        const uint32_t type_num = strtol(first.c_str(), nullptr, 16);
        const auto type =
            (type_num >= static_cast<uint32_t>(BreakpointType::kMin) &&
             type_num < static_cast<uint32_t>(BreakpointType::kUnsupported))
                ? static_cast<BreakpointType>(type_num)
                : BreakpointType::kMin;
        const uint32_t offset = strtol(second.c_str(), nullptr, 16);
        const uint32_t length = strtol(third.c_str(), nullptr, 16);
        return Packet{
            tokens[0].data[0] == 'Z' ? PacketType::kSetBreakpoint : PacketType::kDeleteBreakpoint,
            std::make_unique<const PacketDataBreakpoint>(type, offset, length),
        };
    }
};

static const Command commands[] = {
    { "qSupported",         Command::parseQuerySupported },
    { "?",                  Command::parseQueryHaltReason },
    { "qC",                 Command::parseQueryC },
    { "qfThreadInfo",       Command::parseQueryFThreadInfo },
    { "qsThreadInfo",       Command::parseQuerySThreadInfo },
    { "qL",                 Command::parseQueryRTOSThreadInfo },
    { "qAttached",          Command::parseQueryAttached },
    { "qTStatus",           Command::parseQueryTraceStatus },
    { "qRcmd",              Command::parseQueryRcmd },
    { "QStartNoAckMode",    Command::parseQStartNoAckMode },
    { "Hc",                 Command::parseSetThreadForCont },
    { "Hg",                 Command::parseSetThreadForOps },
    { "vMustReplyEmpty",    Command::parseMustReplyEmpty },
    { "!",                  Command::parseEnableExtendedMode },
    { "\x03",               Command::parseInterrupt },
    { "vCtrlC",             Command::parseInterrupt },
    { "vCont",              Command::parseContinueVCont },
    { "c",                  Command::parseContinue },
    { "m",                  Command::parseReadMemory },
    { "M",                  Command::parseWriteMemory },
    { "g",                  Command::parseReadGeneralRegisters },
    { "G",                  Command::parseWriteGeneralRegisters },
    { "p",                  Command::parseReadRegister },
    { "P",                  Command::parseWriteRegister },
    { "s",                  Command::parseStep },
    { "Z",                  Command::parseSetOrDeleteBreakpoint },
    { "z",                  Command::parseSetOrDeleteBreakpoint },
};

Packet Packet::Parse(std::string packet_data)
{
    for (const auto& command: commands) {
        const auto cmdlen = command.name.length();
        const auto packetlen = packet_data.length();
        if (cmdlen <= packetlen && 0 == memcmp(&command.name[0], &packet_data[0], cmdlen)) {
            return command.parse(std::move(Token::Tokenize(packet_data, command.name)));
        }
    }
    return Packet::None();
}

std::unique_ptr<ExchangeResult> ExchangeContext::Consume(uint8_t byte)
{
    _last_packet += byte;
    switch (_parsing_state) {
    case ParsingState::kIdle:
        if (byte == '$') {
            transit(ParsingState::kPacketData);
        } else if (byte == 0x03) {
            _last_packet = std::string(1, 0x03);
            return ExchangeResult::Ack(_last_packet);
        }
        break;
    case ParsingState::kPacketData:
        if (byte == '#') {
            transit(ParsingState::kChecksum1);
        } else {
            _checksum = (_checksum + byte) & 0xff;
            _packet_data += byte;
        }
        break;
    case ParsingState::kPacketDataBinSecond:
        // TODO escaped and binary data
        break;
    case ParsingState::kChecksum1:
        if (isxdigit(byte)) {
            transit(ParsingState::kChecksum2);
            _given_checksum_first_byte = byte;
        } else {
            transit(ParsingState::kIdle);
            return ExchangeResult::Nak();
        }
        break;
    case ParsingState::kChecksum2:
        const uint8_t checksum = _checksum;
        std::string packet_data(std::move(_packet_data));
        transit(ParsingState::kIdle);
        if (isxdigit(byte)) {
            const uint8_t given_checksum =
                Utils::ParseByteFromHexChars(_given_checksum_first_byte, byte);
            if (given_checksum == checksum) {
                return ExchangeResult::Ack(packet_data);
            } else {
                printf(
                        "Checksum mismatch: received=%02x, expected=%02x\n",
                        given_checksum, checksum);
                printf("Packet data: \"%s\"\n", packet_data.c_str());
                return ExchangeResult::Nak();
            }
        } else {
            return ExchangeResult::Nak();
        }
        break;
    }
    return nullptr;
}

static inline uint8_t CalcPacketDataChecksum(std::string packet) {
    uint8_t checksum{};
    for (const auto c: packet) {
        checksum = (checksum + c) & 0xff;
    }
    return checksum;
}

std::string ExchangeContext::WrapDataToSend(std::string packet)
{
    const uint8_t checksum = CalcPacketDataChecksum(packet);
    const uint8_t c1 = (checksum >> 4) & 0x0f;
    const uint8_t c2 = checksum& 0x0f;
    const char checksum_str[2] = {
        static_cast<char>(c1 < 0xa ? c1 + '0' : c1 + ('a' - 0xa)),
        static_cast<char>(c2 < 0xa ? c2 + '0' : c2 + ('a' - 0xa)),
    };
    return "$" + packet + "#" + std::string(checksum_str, 2);
}

void ExchangeContext::transit(ParsingState new_state)
{
    if (0) {
        printf(
                "GDBRemote ParsingState: %s -> %s\n",
                parsingStateToString(_parsing_state),
                parsingStateToString(new_state));
    }
    switch (new_state) {
    case ParsingState::kIdle:
        _checksum = 0;
        _packet_data.clear();
        break;
    case ParsingState::kPacketData:
        _last_packet = "$";
        break;
    case ParsingState::kPacketDataBinSecond:
        break;
    case ParsingState::kChecksum1:
        break;
    case ParsingState::kChecksum2:
        break;
    }
    _parsing_state = new_state;
}

const char* ExchangeContext::parsingStateToString(ParsingState state)
{
    switch (state) {
    case ParsingState::kIdle:
        return "Idle";
    case ParsingState::kPacketData:
        return "PacketData";
    case ParsingState::kPacketDataBinSecond:
        return "PacketDataBinSecond";
    case ParsingState::kChecksum1:
        return "Checksum1";
    case ParsingState::kChecksum2:
        return "Checksum2";
    }
    return "<unknown>";
}