// Copyright 2013 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

// Originally written by Sven Peter <sven@fail0verflow.com> for anergistic.

#include <algorithm>
#include <atomic>
#include <climits>
#include <csignal>
#include <cstdarg>
#include <cstdio>
#include <cstring>
#include <map>
#include <numeric>
#include <fcntl.h>
#include <fmt/format.h>

#ifdef _WIN32
#include <winsock2.h>
// winsock2.h needs to be included first to prevent winsock.h being included by other includes
#include <io.h>
#include <iphlpapi.h>
#include <ws2tcpip.h>
#define SHUT_RDWR 2
#else
#include <netinet/in.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#endif

#include "common/logging/log.h"
#include "core/arm/arm_interface.h"
#include "core/core.h"
#include "core/gdbstub/gdbstub.h"
#include "core/hle/kernel/process.h"
#include "core/loader/loader.h"
#include "core/memory.h"

namespace GDBStub {
namespace {
constexpr int GDB_BUFFER_SIZE = 10000;

constexpr char GDB_STUB_START = '$';
constexpr char GDB_STUB_END = '#';
constexpr char GDB_STUB_ACK = '+';
constexpr char GDB_STUB_NACK = '-';

#ifndef SIGTRAP
constexpr u32 SIGTRAP = 5;
#endif

#ifndef SIGTERM
constexpr u32 SIGTERM = 15;
#endif

#ifndef MSG_WAITALL
constexpr u32 MSG_WAITALL = 8;
#endif

constexpr u32 SP_REGISTER = 13;
constexpr u32 LR_REGISTER = 14;
constexpr u32 PC_REGISTER = 15;
constexpr u32 CPSR_REGISTER = 25;
constexpr u32 D0_REGISTER = 26;
constexpr u32 FPSCR_REGISTER = 42;

// For sample XML files see the GDB source /gdb/features
// GDB also wants the l character at the start
// This XML defines what the registers are for this specific ARM device
constexpr char target_xml[] =
    R"(l<?xml version="1.0"?>
<!DOCTYPE target SYSTEM "gdb-target.dtd">
<target version="1.0">
  <feature name="org.gnu.gdb.arm.core">
    <reg name="r0" bitsize="32"/>
    <reg name="r1" bitsize="32"/>
    <reg name="r2" bitsize="32"/>
    <reg name="r3" bitsize="32"/>
    <reg name="r4" bitsize="32"/>
    <reg name="r5" bitsize="32"/>
    <reg name="r6" bitsize="32"/>
    <reg name="r7" bitsize="32"/>
    <reg name="r8" bitsize="32"/>
    <reg name="r9" bitsize="32"/>
    <reg name="r10" bitsize="32"/>
    <reg name="r11" bitsize="32"/>
    <reg name="r12" bitsize="32"/>
    <reg name="sp" bitsize="32" type="data_ptr"/>
    <reg name="lr" bitsize="32"/>
    <reg name="pc" bitsize="32" type="code_ptr"/>

    <!-- The CPSR is register 25, rather than register 16, because
         the FPA registers historically were placed between the PC
         and the CPSR in the "g" packet.  -->

    <reg name="cpsr" bitsize="32" regnum="25"/>
  </feature>
  <feature name="org.gnu.gdb.arm.vfp">
    <reg name="d0" bitsize="64" type="float"/>
    <reg name="d1" bitsize="64" type="float"/>
    <reg name="d2" bitsize="64" type="float"/>
    <reg name="d3" bitsize="64" type="float"/>
    <reg name="d4" bitsize="64" type="float"/>
    <reg name="d5" bitsize="64" type="float"/>
    <reg name="d6" bitsize="64" type="float"/>
    <reg name="d7" bitsize="64" type="float"/>
    <reg name="d8" bitsize="64" type="float"/>
    <reg name="d9" bitsize="64" type="float"/>
    <reg name="d10" bitsize="64" type="float"/>
    <reg name="d11" bitsize="64" type="float"/>
    <reg name="d12" bitsize="64" type="float"/>
    <reg name="d13" bitsize="64" type="float"/>
    <reg name="d14" bitsize="64" type="float"/>
    <reg name="d15" bitsize="64" type="float"/>
    <reg name="fpscr" bitsize="32" type="int" group="float"/>
  </feature>
</target>
)";

int gdbserver_socket = -1;

u8 command_buffer[GDB_BUFFER_SIZE];
u32 command_length;

u32 latest_signal = 0;
bool memory_break = false;

static Kernel::Thread* current_thread = nullptr;

// Binding to a port within the reserved ports range (0-1023) requires root permissions,
// so default to a port outside of that range.
u16 gdbstub_port = 24689;

bool halt_loop = true;
bool step_loop = false;
bool send_trap = false;

// If set to false, the server will never be started and no
// gdbstub-related functions will be executed.
std::atomic<bool> server_enabled(false);

#ifdef _WIN32
WSADATA InitData;
#endif

struct Breakpoint {
    bool active;
    VAddr addr;
    u32 len;
    std::array<u8, 4> inst;
};

using BreakpointMap = std::map<VAddr, Breakpoint>;
BreakpointMap breakpoints_execute;
BreakpointMap breakpoints_read;
BreakpointMap breakpoints_write;
} // Anonymous namespace

static Kernel::Thread* FindThreadById(int id) {
    const auto& threads = Core::System::GetInstance().Kernel().GetThreadManager().GetThreadList();
    for (auto& thread : threads) {
        if (thread->GetThreadId() == static_cast<u32>(id)) {
            return thread.get();
        }
    }
    return nullptr;
}

static u32 RegRead(std::size_t id, Kernel::Thread* thread = nullptr) {
    if (!thread) {
        return 0;
    }

    if (id <= PC_REGISTER) {
        return thread->context->GetCpuRegister(id);
    } else if (id == CPSR_REGISTER) {
        return thread->context->GetCpsr();
    } else {
        return 0;
    }
}

static void RegWrite(std::size_t id, u32 val, Kernel::Thread* thread = nullptr) {
    if (!thread) {
        return;
    }

    if (id <= PC_REGISTER) {
        return thread->context->SetCpuRegister(id, val);
    } else if (id == CPSR_REGISTER) {
        return thread->context->SetCpsr(val);
    }
}

static u64 FpuRead(std::size_t id, Kernel::Thread* thread = nullptr) {
    if (!thread) {
        return 0;
    }

    if (id >= D0_REGISTER && id < FPSCR_REGISTER) {
        u64 ret = thread->context->GetFpuRegister(2 * (id - D0_REGISTER));
        ret |= static_cast<u64>(thread->context->GetFpuRegister(2 * (id - D0_REGISTER) + 1)) << 32;
        return ret;
    } else if (id == FPSCR_REGISTER) {
        return thread->context->GetFpscr();
    } else {
        return 0;
    }
}

static void FpuWrite(std::size_t id, u64 val, Kernel::Thread* thread = nullptr) {
    if (!thread) {
        return;
    }

    if (id >= D0_REGISTER && id < FPSCR_REGISTER) {
        thread->context->SetFpuRegister(2 * (id - D0_REGISTER), static_cast<u32>(val));
        thread->context->SetFpuRegister(2 * (id - D0_REGISTER) + 1, static_cast<u32>(val >> 32));
    } else if (id == FPSCR_REGISTER) {
        return thread->context->SetFpscr(static_cast<u32>(val));
    }
}

/**
 * Turns hex string character into the equivalent byte.
 *
 * @param hex Input hex character to be turned into byte.
 */
static u8 HexCharToValue(u8 hex) {
    if (hex >= '0' && hex <= '9') {
        return hex - '0';
    } else if (hex >= 'a' && hex <= 'f') {
        return hex - 'a' + 0xA;
    } else if (hex >= 'A' && hex <= 'F') {
        return hex - 'A' + 0xA;
    }

    LOG_ERROR(Debug_GDBStub, "Invalid nibble: {:c} {:02x}\n", hex, hex);
    return 0;
}

/**
 * Turn nibble of byte into hex string character.
 *
 * @param n Nibble to be turned into hex character.
 */
static u8 NibbleToHex(u8 n) {
    n &= 0xF;
    if (n < 0xA) {
        return '0' + n;
    } else {
        return 'a' + n - 0xA;
    }
}

/**
 * Converts input hex string characters into an array of equivalent of u8 bytes.
 *
 * @param src Pointer to array of output hex string characters.
 * @param len Length of src array.
 */
static u32 HexToInt(const u8* src, std::size_t len) {
    u32 output = 0;
    while (len-- > 0) {
        output = (output << 4) | HexCharToValue(src[0]);
        src++;
    }
    return output;
}

/**
 * Converts input array of u8 bytes into their equivalent hex string characters.
 *
 * @param dest Pointer to buffer to store output hex string characters.
 * @param src Pointer to array of u8 bytes.
 * @param len Length of src array.
 */
static void MemToGdbHex(u8* dest, const u8* src, std::size_t len) {
    while (len-- > 0) {
        u8 tmp = *src++;
        *dest++ = NibbleToHex(tmp >> 4);
        *dest++ = NibbleToHex(tmp);
    }
}

/**
 * Converts input gdb-formatted hex string characters into an array of equivalent of u8 bytes.
 *
 * @param dest Pointer to buffer to store u8 bytes.
 * @param src Pointer to array of output hex string characters.
 * @param len Length of src array.
 */
static void GdbHexToMem(u8* dest, const u8* src, std::size_t len) {
    while (len-- > 0) {
        *dest++ = (HexCharToValue(src[0]) << 4) | HexCharToValue(src[1]);
        src += 2;
    }
}

/**
 * Convert a u32 into a gdb-formatted hex string.
 *
 * @param dest Pointer to buffer to store output hex string characters.
 * @param v    Value to convert.
 */
static void IntToGdbHex(u8* dest, u32 v) {
    for (int i = 0; i < 8; i += 2) {
        dest[i + 1] = NibbleToHex(v >> (4 * i));
        dest[i] = NibbleToHex(v >> (4 * (i + 1)));
    }
}

/**
 * Convert a gdb-formatted hex string into a u32.
 *
 * @param src Pointer to hex string.
 */
static u32 GdbHexToInt(const u8* src) {
    u32 output = 0;

    for (int i = 0; i < 8; i += 2) {
        output = (output << 4) | HexCharToValue(src[7 - i - 1]);
        output = (output << 4) | HexCharToValue(src[7 - i]);
    }

    return output;
}

/**
 * Convert a u64 into a gdb-formatted hex string.
 *
 * @param dest Pointer to buffer to store output hex string characters.
 * @param v    Value to convert.
 */
static void LongToGdbHex(u8* dest, u64 v) {
    for (int i = 0; i < 16; i += 2) {
        dest[i + 1] = NibbleToHex(static_cast<u8>(v >> (4 * i)));
        dest[i] = NibbleToHex(static_cast<u8>(v >> (4 * (i + 1))));
    }
}

/**
 * Convert a gdb-formatted hex string into a u64.
 *
 * @param src Pointer to hex string.
 */
static u64 GdbHexToLong(const u8* src) {
    u64 output = 0;

    for (int i = 0; i < 16; i += 2) {
        output = (output << 4) | HexCharToValue(src[15 - i - 1]);
        output = (output << 4) | HexCharToValue(src[15 - i]);
    }

    return output;
}

/// Read a byte from the gdb client.
static u8 ReadByte() {
    u8 c;
    std::size_t received_size = recv(gdbserver_socket, reinterpret_cast<char*>(&c), 1, MSG_WAITALL);
    if (received_size != 1) {
        LOG_ERROR(Debug_GDBStub, "recv failed : {}", received_size);
        Shutdown();
    }

    return c;
}

/// Calculate the checksum of the current command buffer.
static u8 CalculateChecksum(const u8* buffer, std::size_t length) {
    return static_cast<u8>(std::accumulate(buffer, buffer + length, 0, std::plus<u8>()));
}

/**
 * Get the map of breakpoints for a given breakpoint type.
 *
 * @param type Type of breakpoint map.
 */
static BreakpointMap& GetBreakpointMap(BreakpointType type) {
    switch (type) {
    case BreakpointType::Execute:
        return breakpoints_execute;
    case BreakpointType::Read:
        return breakpoints_read;
    case BreakpointType::Write:
        return breakpoints_write;
    default:
        return breakpoints_read;
    }
}

/**
 * Remove the breakpoint from the given address of the specified type.
 *
 * @param type Type of breakpoint.
 * @param addr Address of breakpoint.
 */
static void RemoveBreakpoint(BreakpointType type, VAddr addr) {
    BreakpointMap& p = GetBreakpointMap(type);

    const auto bp = p.find(addr);
    if (bp == p.end()) {
        return;
    }

    LOG_DEBUG(Debug_GDBStub, "gdb: removed a breakpoint: {:08x} bytes at {:08x} of type {}",
              bp->second.len, bp->second.addr, static_cast<int>(type));
    Memory::WriteBlock(*Core::System::GetInstance().Kernel().GetCurrentProcess(), bp->second.addr,
                       bp->second.inst.data(), bp->second.inst.size());
    Core::CPU().ClearInstructionCache();
    p.erase(addr);
}

BreakpointAddress GetNextBreakpointFromAddress(VAddr addr, BreakpointType type) {
    const BreakpointMap& p = GetBreakpointMap(type);
    const auto next_breakpoint = p.lower_bound(addr);
    BreakpointAddress breakpoint;

    if (next_breakpoint != p.end()) {
        breakpoint.address = next_breakpoint->first;
        breakpoint.type = type;
    } else {
        breakpoint.address = 0;
        breakpoint.type = BreakpointType::None;
    }

    return breakpoint;
}

bool CheckBreakpoint(VAddr addr, BreakpointType type) {
    if (!IsConnected()) {
        return false;
    }

    const BreakpointMap& p = GetBreakpointMap(type);
    const auto bp = p.find(addr);

    if (bp == p.end()) {
        return false;
    }

    u32 len = bp->second.len;

    // IDA Pro defaults to 4-byte breakpoints for all non-hardware breakpoints
    // no matter if it's a 4-byte or 2-byte instruction. When you execute a
    // Thumb instruction with a 4-byte breakpoint set, it will set a breakpoint on
    // two instructions instead of the single instruction you placed the breakpoint
    // on. So, as a way to make sure that execution breakpoints are only breaking
    // on the instruction that was specified, set the length of an execution
    // breakpoint to 1. This should be fine since the CPU should never begin executing
    // an instruction anywhere except the beginning of the instruction.
    if (type == BreakpointType::Execute) {
        len = 1;
    }

    if (bp->second.active && (addr >= bp->second.addr && addr < bp->second.addr + len)) {
        LOG_DEBUG(Debug_GDBStub,
                  "Found breakpoint type {} @ {:08x}, range: {:08x}"
                  " - {:08x} ({:x} bytes)",
                  static_cast<int>(type), addr, bp->second.addr, bp->second.addr + len, len);
        return true;
    }

    return false;
}

/**
 * Send packet to gdb client.
 *
 * @param packet Packet to be sent to client.
 */
static void SendPacket(const char packet) {
    std::size_t sent_size = send(gdbserver_socket, &packet, 1, 0);
    if (sent_size != 1) {
        LOG_ERROR(Debug_GDBStub, "send failed");
    }
}

/**
 * Send reply to gdb client.
 *
 * @param reply Reply to be sent to client.
 */
static void SendReply(const char* reply) {
    if (!IsConnected()) {
        return;
    }

    memset(command_buffer, 0, sizeof(command_buffer));

    command_length = static_cast<u32>(strlen(reply));
    if (command_length + 4 > sizeof(command_buffer)) {
        LOG_ERROR(Debug_GDBStub, "command_buffer overflow in SendReply");
        return;
    }

    memcpy(command_buffer + 1, reply, command_length);

    u8 checksum = CalculateChecksum(command_buffer, command_length + 1);
    command_buffer[0] = GDB_STUB_START;
    command_buffer[command_length + 1] = GDB_STUB_END;
    command_buffer[command_length + 2] = NibbleToHex(checksum >> 4);
    command_buffer[command_length + 3] = NibbleToHex(checksum);

    u8* ptr = command_buffer;
    u32 left = command_length + 4;
    while (left > 0) {
        int sent_size = send(gdbserver_socket, reinterpret_cast<char*>(ptr), left, 0);
        if (sent_size < 0) {
            LOG_ERROR(Debug_GDBStub, "gdb: send failed");
            return Shutdown();
        }

        left -= sent_size;
        ptr += sent_size;
    }
}

/// Handle query command from gdb client.
static void HandleQuery() {
    LOG_DEBUG(Debug_GDBStub, "gdb: query '{}'\n", command_buffer + 1);

    const char* query = reinterpret_cast<const char*>(command_buffer + 1);

    if (strcmp(query, "TStatus") == 0) {
        SendReply("T0");
    } else if (strncmp(query, "Supported", strlen("Supported")) == 0) {
        // PacketSize needs to be large enough for target xml
        SendReply("PacketSize=2000;qXfer:features:read+;qXfer:threads:read+");
    } else if (strncmp(query, "Xfer:features:read:target.xml:",
                       strlen("Xfer:features:read:target.xml:")) == 0) {
        SendReply(target_xml);
    } else if (strncmp(query, "fThreadInfo", strlen("fThreadInfo")) == 0) {
        std::string val = "m";
        const auto& threads =
            Core::System::GetInstance().Kernel().GetThreadManager().GetThreadList();
        for (const auto& thread : threads) {
            val += fmt::format("{:x},", thread->GetThreadId());
        }
        val.pop_back();
        SendReply(val.c_str());
    } else if (strncmp(query, "sThreadInfo", strlen("sThreadInfo")) == 0) {
        SendReply("l");
    } else if (strncmp(query, "Xfer:threads:read", strlen("Xfer:threads:read")) == 0) {
        std::string buffer;
        buffer += "l<?xml version=\"1.0\"?>";
        buffer += "<threads>";
        const auto& threads =
            Core::System::GetInstance().Kernel().GetThreadManager().GetThreadList();
        for (const auto& thread : threads) {
            buffer += fmt::format(R"*(<thread id="{:x}" name="Thread {:x}"></thread>)*",
                                  thread->GetThreadId(), thread->GetThreadId());
        }
        buffer += "</threads>";
        SendReply(buffer.c_str());
    } else {
        SendReply("");
    }
}

/// Handle set thread command from gdb client.
static void HandleSetThread() {
    int thread_id = -1;
    if (command_buffer[2] != '-') {
        thread_id = static_cast<int>(HexToInt(command_buffer + 2, command_length - 2));
    }
    if (thread_id >= 1) {
        current_thread = FindThreadById(thread_id);
    }
    if (!current_thread) {
        thread_id = 1;
        current_thread = FindThreadById(thread_id);
    }
    if (current_thread) {
        SendReply("OK");
        return;
    }
    SendReply("E01");
}

/// Handle thread alive command from gdb client.
static void HandleThreadAlive() {
    int thread_id = static_cast<int>(HexToInt(command_buffer + 1, command_length - 1));
    if (thread_id == 0) {
        thread_id = 1;
    }
    if (FindThreadById(thread_id)) {
        SendReply("OK");
        return;
    }
    SendReply("E01");
}

/**
 * Send signal packet to client.
 *
 * @param signal Signal to be sent to client.
 */
static void SendSignal(Kernel::Thread* thread, u32 signal, bool full = true) {
    if (gdbserver_socket == -1) {
        return;
    }

    latest_signal = signal;

    if (!thread) {
        full = false;
    }

    std::string buffer;
    if (full) {

        buffer = fmt::format("T{:02x}{:02x}:{:08x};{:02x}:{:08x};{:02x}:{:08x}", latest_signal,
                             PC_REGISTER, htonl(Core::CPU().GetPC()), SP_REGISTER,
                             htonl(Core::CPU().GetReg(SP_REGISTER)), LR_REGISTER,
                             htonl(Core::CPU().GetReg(LR_REGISTER)));
    } else {
        buffer = fmt::format("T{:02x}", latest_signal);
    }

    if (thread) {
        buffer += fmt::format(";thread:{:x};", thread->GetThreadId());
    }

    LOG_DEBUG(Debug_GDBStub, "Response: {}", buffer);
    SendReply(buffer.c_str());
}

/// Read command from gdb client.
static void ReadCommand() {
    command_length = 0;
    memset(command_buffer, 0, sizeof(command_buffer));

    u8 c = ReadByte();
    if (c == '+') {
        // ignore ack
        return;
    } else if (c == 0x03) {
        LOG_INFO(Debug_GDBStub, "gdb: found break command\n");
        halt_loop = true;
        SendSignal(current_thread, SIGTRAP);
        return;
    } else if (c != GDB_STUB_START) {
        LOG_DEBUG(Debug_GDBStub, "gdb: read invalid byte {:02x}\n", c);
        return;
    }

    while ((c = ReadByte()) != GDB_STUB_END) {
        if (command_length >= sizeof(command_buffer)) {
            LOG_ERROR(Debug_GDBStub, "gdb: command_buffer overflow\n");
            SendPacket(GDB_STUB_NACK);
            return;
        }
        command_buffer[command_length++] = c;
    }

    u8 checksum_received = HexCharToValue(ReadByte()) << 4;
    checksum_received |= HexCharToValue(ReadByte());

    u8 checksum_calculated = CalculateChecksum(command_buffer, command_length);

    if (checksum_received != checksum_calculated) {
        LOG_ERROR(
            Debug_GDBStub,
            "gdb: invalid checksum: calculated {:02x} and read {:02x} for ${}# (length: {})\n",
            checksum_calculated, checksum_received, command_buffer, command_length);

        command_length = 0;

        SendPacket(GDB_STUB_NACK);
        return;
    }

    SendPacket(GDB_STUB_ACK);
}

/// Check if there is data to be read from the gdb client.
static bool IsDataAvailable() {
    if (!IsConnected()) {
        return false;
    }

    fd_set fd_socket;

    FD_ZERO(&fd_socket);
    FD_SET(gdbserver_socket, &fd_socket);

    struct timeval t;
    t.tv_sec = 0;
    t.tv_usec = 0;

    if (select(gdbserver_socket + 1, &fd_socket, nullptr, nullptr, &t) < 0) {
        LOG_ERROR(Debug_GDBStub, "select failed");
        return false;
    }

    return FD_ISSET(gdbserver_socket, &fd_socket) != 0;
}

/// Send requested register to gdb client.
static void ReadRegister() {
    static u8 reply[64];
    memset(reply, 0, sizeof(reply));

    u32 id = HexCharToValue(command_buffer[1]);
    if (command_buffer[2] != '\0') {
        id <<= 4;
        id |= HexCharToValue(command_buffer[2]);
    }

    if (id <= PC_REGISTER) {
        IntToGdbHex(reply, RegRead(id, current_thread));
    } else if (id == CPSR_REGISTER) {
        IntToGdbHex(reply, RegRead(id, current_thread));
    } else if (id >= D0_REGISTER && id < FPSCR_REGISTER) {
        LongToGdbHex(reply, FpuRead(id, current_thread));
    } else if (id == FPSCR_REGISTER) {
        IntToGdbHex(reply, static_cast<u32>(FpuRead(id, current_thread)));
    } else {
        return SendReply("E01");
    }

    SendReply(reinterpret_cast<char*>(reply));
}

/// Send all registers to the gdb client.
static void ReadRegisters() {
    static u8 buffer[GDB_BUFFER_SIZE - 4];
    memset(buffer, 0, sizeof(buffer));

    u8* bufptr = buffer;

    for (u32 reg = 0; reg <= PC_REGISTER; reg++) {
        IntToGdbHex(bufptr + reg * 8, RegRead(reg, current_thread));
    }

    bufptr += 16 * 8;

    IntToGdbHex(bufptr, RegRead(CPSR_REGISTER, current_thread));

    bufptr += 8;

    for (u32 reg = D0_REGISTER; reg < FPSCR_REGISTER; reg++) {
        LongToGdbHex(bufptr + reg * 16, FpuRead(reg, current_thread));
    }

    bufptr += 16 * 16;

    IntToGdbHex(bufptr, static_cast<u32>(FpuRead(FPSCR_REGISTER, current_thread)));

    SendReply(reinterpret_cast<char*>(buffer));
}

/// Modify data of register specified by gdb client.
static void WriteRegister() {
    const u8* buffer_ptr = command_buffer + 3;

    u32 id = HexCharToValue(command_buffer[1]);
    if (command_buffer[2] != '=') {
        ++buffer_ptr;
        id <<= 4;
        id |= HexCharToValue(command_buffer[2]);
    }

    if (id <= PC_REGISTER) {
        RegWrite(id, GdbHexToInt(buffer_ptr), current_thread);
    } else if (id == CPSR_REGISTER) {
        RegWrite(id, GdbHexToInt(buffer_ptr), current_thread);
    } else if (id >= D0_REGISTER && id < FPSCR_REGISTER) {
        FpuWrite(id, GdbHexToLong(buffer_ptr), current_thread);
    } else if (id == FPSCR_REGISTER) {
        FpuWrite(id, GdbHexToInt(buffer_ptr), current_thread);
    } else {
        return SendReply("E01");
    }

    Core::CPU().LoadContext(current_thread->context);

    SendReply("OK");
}

/// Modify all registers with data received from the client.
static void WriteRegisters() {
    const u8* buffer_ptr = command_buffer + 1;

    if (command_buffer[0] != 'G')
        return SendReply("E01");

    for (u32 i = 0, reg = 0; reg <= FPSCR_REGISTER; i++, reg++) {
        if (reg <= PC_REGISTER) {
            RegWrite(reg, GdbHexToInt(buffer_ptr + i * 8));
        } else if (reg == CPSR_REGISTER) {
            RegWrite(reg, GdbHexToInt(buffer_ptr + i * 8));
        } else if (reg == CPSR_REGISTER - 1) {
            // Dummy FPA register, ignore
        } else if (reg < CPSR_REGISTER) {
            // Dummy FPA registers, ignore
            i += 2;
        } else if (reg >= D0_REGISTER && reg < FPSCR_REGISTER) {
            FpuWrite(reg, GdbHexToLong(buffer_ptr + i * 16));
            i++; // Skip padding
        } else if (reg == FPSCR_REGISTER) {
            FpuWrite(reg, GdbHexToInt(buffer_ptr + i * 8));
        }
    }

    Core::CPU().LoadContext(current_thread->context);

    SendReply("OK");
}

/// Read location in memory specified by gdb client.
static void ReadMemory() {
    static u8 reply[GDB_BUFFER_SIZE - 4];

    auto start_offset = command_buffer + 1;
    auto addr_pos = std::find(start_offset, command_buffer + command_length, ',');
    VAddr addr = HexToInt(start_offset, static_cast<u32>(addr_pos - start_offset));

    start_offset = addr_pos + 1;
    u32 len =
        HexToInt(start_offset, static_cast<u32>((command_buffer + command_length) - start_offset));

    LOG_DEBUG(Debug_GDBStub, "gdb: addr: {:08x} len: {:08x}\n", addr, len);

    if (len * 2 > sizeof(reply)) {
        SendReply("E01");
    }

    if (!Core::System::GetInstance().Memory().IsValidVirtualAddress(
            *Core::System::GetInstance().Kernel().GetCurrentProcess(), addr)) {
        return SendReply("E00");
    }

    std::vector<u8> data(len);
    Memory::ReadBlock(*Core::System::GetInstance().Kernel().GetCurrentProcess(), addr, data.data(),
                      len);

    MemToGdbHex(reply, data.data(), len);
    reply[len * 2] = '\0';
    SendReply(reinterpret_cast<char*>(reply));
}

/// Modify location in memory with data received from the gdb client.
static void WriteMemory() {
    auto start_offset = command_buffer + 1;
    auto addr_pos = std::find(start_offset, command_buffer + command_length, ',');
    VAddr addr = HexToInt(start_offset, static_cast<u32>(addr_pos - start_offset));

    start_offset = addr_pos + 1;
    auto len_pos = std::find(start_offset, command_buffer + command_length, ':');
    u32 len = HexToInt(start_offset, static_cast<u32>(len_pos - start_offset));

    if (!Core::System::GetInstance().Memory().IsValidVirtualAddress(
            *Core::System::GetInstance().Kernel().GetCurrentProcess(), addr)) {
        return SendReply("E00");
    }

    std::vector<u8> data(len);

    GdbHexToMem(data.data(), len_pos + 1, len);
    Memory::WriteBlock(*Core::System::GetInstance().Kernel().GetCurrentProcess(), addr, data.data(),
                       len);
    Core::CPU().ClearInstructionCache();
    SendReply("OK");
}

void Break(bool is_memory_break) {
    send_trap = true;

    memory_break = is_memory_break;
}

/// Tell the CPU that it should perform a single step.
static void Step() {
    if (command_length > 1) {
        RegWrite(PC_REGISTER, GdbHexToInt(command_buffer + 1), current_thread);
        Core::CPU().LoadContext(current_thread->context);
    }
    step_loop = true;
    halt_loop = true;
    send_trap = true;
    Core::CPU().ClearInstructionCache();
}

bool IsMemoryBreak() {
    if (IsConnected()) {
        return false;
    }

    return memory_break;
}

/// Tell the CPU to continue executing.
static void Continue() {
    memory_break = false;
    step_loop = false;
    halt_loop = false;
    Core::CPU().ClearInstructionCache();
}

/**
 * Commit breakpoint to list of breakpoints.
 *
 * @param type Type of breakpoint.
 * @param addr Address of breakpoint.
 * @param len Length of breakpoint.
 */
static bool CommitBreakpoint(BreakpointType type, VAddr addr, u32 len) {
    BreakpointMap& p = GetBreakpointMap(type);

    Breakpoint breakpoint;
    breakpoint.active = true;
    breakpoint.addr = addr;
    breakpoint.len = len;
    Memory::ReadBlock(*Core::System::GetInstance().Kernel().GetCurrentProcess(), addr,
                      breakpoint.inst.data(), breakpoint.inst.size());
    static constexpr std::array<u8, 4> btrap{0x70, 0x00, 0x20, 0xe1};
    Memory::WriteBlock(*Core::System::GetInstance().Kernel().GetCurrentProcess(), addr,
                       btrap.data(), btrap.size());
    Core::CPU().ClearInstructionCache();
    p.insert({addr, breakpoint});

    LOG_DEBUG(Debug_GDBStub, "gdb: added {} breakpoint: {:08x} bytes at {:08x}\n",
              static_cast<int>(type), breakpoint.len, breakpoint.addr);

    return true;
}

/// Handle add breakpoint command from gdb client.
static void AddBreakpoint() {
    BreakpointType type;

    u8 type_id = HexCharToValue(command_buffer[1]);
    switch (type_id) {
    case 0:
    case 1:
        type = BreakpointType::Execute;
        break;
    case 2:
        type = BreakpointType::Write;
        break;
    case 3:
        type = BreakpointType::Read;
        break;
    case 4:
        type = BreakpointType::Access;
        break;
    default:
        return SendReply("E01");
    }

    auto start_offset = command_buffer + 3;
    auto addr_pos = std::find(start_offset, command_buffer + command_length, ',');
    VAddr addr = HexToInt(start_offset, static_cast<u32>(addr_pos - start_offset));

    start_offset = addr_pos + 1;
    u32 len =
        HexToInt(start_offset, static_cast<u32>((command_buffer + command_length) - start_offset));

    if (type == BreakpointType::Access) {
        // Access is made up of Read and Write types, so add both breakpoints
        type = BreakpointType::Read;

        if (!CommitBreakpoint(type, addr, len)) {
            return SendReply("E02");
        }

        type = BreakpointType::Write;
    }

    if (!CommitBreakpoint(type, addr, len)) {
        return SendReply("E02");
    }

    SendReply("OK");
}

/// Handle remove breakpoint command from gdb client.
static void RemoveBreakpoint() {
    BreakpointType type;

    u8 type_id = HexCharToValue(command_buffer[1]);
    switch (type_id) {
    case 0:
    case 1:
        type = BreakpointType::Execute;
        break;
    case 2:
        type = BreakpointType::Write;
        break;
    case 3:
        type = BreakpointType::Read;
        break;
    case 4:
        type = BreakpointType::Access;
        break;
    default:
        return SendReply("E01");
    }

    auto start_offset = command_buffer + 3;
    auto addr_pos = std::find(start_offset, command_buffer + command_length, ',');
    VAddr addr = HexToInt(start_offset, static_cast<u32>(addr_pos - start_offset));

    if (type == BreakpointType::Access) {
        // Access is made up of Read and Write types, so add both breakpoints
        type = BreakpointType::Read;
        RemoveBreakpoint(type, addr);

        type = BreakpointType::Write;
    }

    RemoveBreakpoint(type, addr);
    SendReply("OK");
}

void HandlePacket() {
    if (!IsConnected()) {
        return;
    }

    if (!IsDataAvailable()) {
        return;
    }

    ReadCommand();
    if (command_length == 0) {
        return;
    }

    LOG_DEBUG(Debug_GDBStub, "Packet: {}", command_buffer);

    switch (command_buffer[0]) {
    case 'q':
        HandleQuery();
        break;
    case 'H':
        HandleSetThread();
        break;
    case '?':
        SendSignal(current_thread, latest_signal);
        break;
    case 'k':
        Shutdown();
        LOG_INFO(Debug_GDBStub, "killed by gdb");
        return;
    case 'g':
        ReadRegisters();
        break;
    case 'G':
        WriteRegisters();
        break;
    case 'p':
        ReadRegister();
        break;
    case 'P':
        WriteRegister();
        break;
    case 'm':
        ReadMemory();
        break;
    case 'M':
        WriteMemory();
        break;
    case 's':
        Step();
        return;
    case 'C':
    case 'c':
        Continue();
        return;
    case 'z':
        RemoveBreakpoint();
        break;
    case 'Z':
        AddBreakpoint();
        break;
    case 'T':
        HandleThreadAlive();
        break;
    default:
        SendReply("");
        break;
    }
}

void SetServerPort(u16 port) {
    gdbstub_port = port;
}

void ToggleServer(bool status) {
    if (status) {
        server_enabled = status;

        // Start server
        if (!IsConnected() && Core::System::GetInstance().IsPoweredOn()) {
            Init();
        }
    } else {
        // Stop server
        if (IsConnected()) {
            Shutdown();
        }

        server_enabled = status;
    }
}

static void Init(u16 port) {
    if (!server_enabled) {
        // Set the halt loop to false in case the user enabled the gdbstub mid-execution.
        // This way the CPU can still execute normally.
        halt_loop = false;
        step_loop = false;
        return;
    }

    // Setup initial gdbstub status
    halt_loop = true;
    step_loop = false;

    breakpoints_execute.clear();
    breakpoints_read.clear();
    breakpoints_write.clear();

    // Start gdb server
    LOG_INFO(Debug_GDBStub, "Starting GDB server on port {}...", port);

    sockaddr_in saddr_server = {};
    saddr_server.sin_family = AF_INET;
    saddr_server.sin_port = htons(port);
    saddr_server.sin_addr.s_addr = INADDR_ANY;

#ifdef _WIN32
    WSAStartup(MAKEWORD(2, 2), &InitData);
#endif

    int tmpsock = static_cast<int>(socket(PF_INET, SOCK_STREAM, 0));
    if (tmpsock == -1) {
        LOG_ERROR(Debug_GDBStub, "Failed to create gdb socket");
    }

    // Set socket to SO_REUSEADDR so it can always bind on the same port
    int reuse_enabled = 1;
    if (setsockopt(tmpsock, SOL_SOCKET, SO_REUSEADDR, (const char*)&reuse_enabled,
                   sizeof(reuse_enabled)) < 0) {
        LOG_ERROR(Debug_GDBStub, "Failed to set gdb socket option");
    }

    const sockaddr* server_addr = reinterpret_cast<const sockaddr*>(&saddr_server);
    socklen_t server_addrlen = sizeof(saddr_server);
    if (bind(tmpsock, server_addr, server_addrlen) < 0) {
        LOG_ERROR(Debug_GDBStub, "Failed to bind gdb socket");
    }

    if (listen(tmpsock, 1) < 0) {
        LOG_ERROR(Debug_GDBStub, "Failed to listen to gdb socket");
    }

    // Wait for gdb to connect
    LOG_INFO(Debug_GDBStub, "Waiting for gdb to connect...\n");
    sockaddr_in saddr_client;
    sockaddr* client_addr = reinterpret_cast<sockaddr*>(&saddr_client);
    socklen_t client_addrlen = sizeof(saddr_client);
    gdbserver_socket = static_cast<int>(accept(tmpsock, client_addr, &client_addrlen));
    if (gdbserver_socket < 0) {
        // In the case that we couldn't start the server for whatever reason, just start CPU
        // execution like normal.
        halt_loop = false;
        step_loop = false;

        LOG_ERROR(Debug_GDBStub, "Failed to accept gdb client");
    } else {
        LOG_INFO(Debug_GDBStub, "Client connected.\n");
        saddr_client.sin_addr.s_addr = ntohl(saddr_client.sin_addr.s_addr);
    }

    // Clean up temporary socket if it's still alive at this point.
    if (tmpsock != -1) {
        shutdown(tmpsock, SHUT_RDWR);
    }
}

void Init() {
    Init(gdbstub_port);
}

void Shutdown() {
    if (!server_enabled) {
        return;
    }

    LOG_INFO(Debug_GDBStub, "Stopping GDB ...");
    if (gdbserver_socket != -1) {
        shutdown(gdbserver_socket, SHUT_RDWR);
        gdbserver_socket = -1;
    }

#ifdef _WIN32
    WSACleanup();
#endif

    LOG_INFO(Debug_GDBStub, "GDB stopped.");
}

bool IsServerEnabled() {
    return server_enabled;
}

bool IsConnected() {
    return IsServerEnabled() && gdbserver_socket != -1;
}

bool GetCpuHaltFlag() {
    return halt_loop;
}

bool GetCpuStepFlag() {
    return step_loop;
}

void SetCpuStepFlag(bool is_step) {
    step_loop = is_step;
}

void SendTrap(Kernel::Thread* thread, int trap) {
    if (!send_trap) {
        return;
    }

    if (!halt_loop || current_thread == thread) {
        current_thread = thread;
        SendSignal(thread, trap);
    }
    halt_loop = true;
    send_trap = false;
}
}; // namespace GDBStub