#include "GdbRspDebugServer.hpp"

#include <sys/socket.h>
#include <unistd.h>

#include "src/Logger/Logger.hpp"

#include "Exceptions/ClientDisconnected.hpp"
#include "Exceptions/ClientNotSupported.hpp"
#include "Exceptions/ClientCommunicationError.hpp"
#include "Exceptions/DebugSessionAborted.hpp"

#include "src/Exceptions/Exception.hpp"
#include "src/Exceptions/InvalidConfig.hpp"
#include "src/Exceptions/DebugServerInterrupted.hpp"

// Command packets
#include "CommandPackets/CommandPacket.hpp"
#include "CommandPackets/SupportedFeaturesQuery.hpp"
#include "CommandPackets/InterruptExecution.hpp"
#include "CommandPackets/ContinueExecution.hpp"
#include "CommandPackets/StepExecution.hpp"
#include "CommandPackets/ReadRegisters.hpp"
#include "CommandPackets/WriteRegister.hpp"
#include "CommandPackets/SetBreakpoint.hpp"
#include "CommandPackets/RemoveBreakpoint.hpp"
#include "CommandPackets/Monitor.hpp"
#include "CommandPackets/ResetTarget.hpp"

// Response packets
#include "ResponsePackets/TargetStopped.hpp"

namespace Bloom::DebugServer::Gdb
{
    using namespace Exceptions;
    using namespace Bloom::Exceptions;

    using CommandPackets::CommandPacket;

    using TargetController::TargetControllerState;

    GdbRspDebugServer::GdbRspDebugServer(
        const DebugServerConfig& debugServerConfig,
        EventListener& eventListener,
        EventFdNotifier& eventNotifier
    )
        : debugServerConfig(GdbDebugServerConfig(debugServerConfig))
        , eventListener(eventListener)
        , interruptEventNotifier(eventNotifier)
    {}

    void GdbRspDebugServer::init() {
        this->socketAddress.sin_family = AF_INET;
        this->socketAddress.sin_port = htons(this->debugServerConfig.listeningPortNumber);

        if (::inet_pton(
                AF_INET,
                this->debugServerConfig.listeningAddress.c_str(),
                &(this->socketAddress.sin_addr)
            ) == 0
        ) {
            // Invalid IP address
            throw InvalidConfig(
                "Invalid IP address provided in config file: (\"" + this->debugServerConfig.listeningAddress
                    + "\")"
            );
        }

        int socketFileDescriptor = 0;

        if ((socketFileDescriptor = ::socket(AF_INET, SOCK_STREAM, 0)) == 0) {
            throw Exception("Failed to create socket file descriptor.");
        }

        const auto enableReuseAddressSocketOption = 1;

        if (::setsockopt(
                socketFileDescriptor,
                SOL_SOCKET,
                SO_REUSEADDR,
                &(enableReuseAddressSocketOption),
                sizeof(enableReuseAddressSocketOption)
            ) < 0
        ) {
            Logger::error("Failed to set socket SO_REUSEADDR option.");
        }

        if (::bind(
                socketFileDescriptor,
                reinterpret_cast<const sockaddr*>(&(this->socketAddress)),
                sizeof(this->socketAddress)
            ) < 0
        ) {
            throw Exception("Failed to bind address. The selected port number ("
                + std::to_string(this->debugServerConfig.listeningPortNumber) + ") may be in use.");
        }

        this->serverSocketFileDescriptor = socketFileDescriptor;

        this->epollInstance.addEntry(
            this->serverSocketFileDescriptor.value(),
            static_cast<std::uint16_t>(EpollEvent::READ_READY)
        );

        this->epollInstance.addEntry(
            this->interruptEventNotifier.getFileDescriptor(),
            static_cast<std::uint16_t>(EpollEvent::READ_READY)
        );

        Logger::info("GDB RSP address: " + this->debugServerConfig.listeningAddress);
        Logger::info("GDB RSP port: " + std::to_string(this->debugServerConfig.listeningPortNumber));

        this->eventListener.registerCallbackForEventType<Events::TargetControllerStateChanged>(
            std::bind(&GdbRspDebugServer::onTargetControllerStateChanged, this, std::placeholders::_1)
        );

        this->eventListener.registerCallbackForEventType<Events::TargetExecutionStopped>(
            std::bind(&GdbRspDebugServer::onTargetExecutionStopped, this, std::placeholders::_1)
        );
    }

    void GdbRspDebugServer::close() {
        this->terminateActiveDebugSession();

        if (this->serverSocketFileDescriptor.has_value()) {
            ::close(this->serverSocketFileDescriptor.value());
        }
    }

    void GdbRspDebugServer::run() {
        try {
            if (!this->activeDebugSession.has_value()) {
                Logger::info("Waiting for GDB RSP connection");

                auto connection = this->waitForConnection();

                if (!connection.has_value()) {
                    // Likely an interrupt - return control to DebugServerComponent::run() so it can process any events
                    return;
                }

                Logger::info("Accepted GDP RSP connection from " + connection->getIpAddress());

                this->activeDebugSession.emplace(
                    DebugSession(std::move(connection.value()), this->getGdbTargetDescriptor())
                );

                EventManager::triggerEvent(std::make_shared<Events::DebugSessionStarted>());

                /*
                 * Before proceeding with a new debug session, we must ensure that the TargetController is able to
                 * service it.
                 */
                if (!this->targetControllerConsole.isTargetControllerInService()) {
                    // The TargetController is suspended - allow it some time to wake up

                    /*
                     * At first, it may seem like there is a possibility that we may miss the
                     * TargetControllerStateChanged event here. But this is nothing to worry about because
                     * this->eventListener is already listening for TargetControllerStateChanged events, so if an event
                     * does fire in between the call to isTargetControllerInService() (above) and waitForEvent() (below),
                     * then waitForEvent() will return immediately with the event.
                     */
                    const auto targetControllerStateChangedEvent = this->eventListener.waitForEvent<
                        Events::TargetControllerStateChanged
                    >(std::chrono::milliseconds(10000));

                    if (
                        !targetControllerStateChangedEvent.has_value()
                        || targetControllerStateChangedEvent->get()->state != TargetControllerState::ACTIVE
                    ) {
                        this->terminateActiveDebugSession();
                        throw DebugSessionAborted("TargetController not in service");
                    }
                }

                this->targetControllerConsole.stopTargetExecution();
                this->targetControllerConsole.resetTarget();
            }

            auto commandPacket = this->waitForCommandPacket();

            if (commandPacket == nullptr) {
                // Likely an interrupt
                return;
            }

            commandPacket->handle(this->activeDebugSession.value(), this->targetControllerConsole);

        } catch (const ClientDisconnected&) {
            Logger::info("GDB RSP client disconnected");
            this->terminateActiveDebugSession();
            return;

        } catch (const ClientCommunicationError& exception) {
            Logger::error(
                "GDB RSP client communication error - " + exception.getMessage() + " - closing connection"
            );
            this->terminateActiveDebugSession();
            return;

        } catch (const ClientNotSupported& exception) {
            Logger::error("Invalid GDB RSP client - " + exception.getMessage() + " - closing connection");
            this->terminateActiveDebugSession();
            return;

        } catch (const DebugSessionAborted& exception) {
            Logger::warning("GDB debug session aborted - " + exception.getMessage());
            this->terminateActiveDebugSession();
            return;

        } catch (const DebugServerInterrupted&) {
            // Server was interrupted
            Logger::debug("GDB RSP interrupted");
            return;
        }
    }

    std::optional<Connection> GdbRspDebugServer::waitForConnection() {
        if (::listen(this->serverSocketFileDescriptor.value(), 3) != 0) {
            throw Exception("Failed to listen on server socket");
        }

        const auto eventFileDescriptor = this->epollInstance.waitForEvent();

        if (
            !eventFileDescriptor.has_value()
            || eventFileDescriptor.value() == this->interruptEventNotifier.getFileDescriptor()
        ) {
            this->interruptEventNotifier.clear();
            return std::nullopt;
        }

        return std::make_optional<Connection>(
            this->serverSocketFileDescriptor.value(),
            this->interruptEventNotifier
        );
    }

    std::unique_ptr<CommandPacket> GdbRspDebugServer::waitForCommandPacket() {
        const auto rawPackets = this->activeDebugSession->connection.readRawPackets();

        if (rawPackets.empty()) {
            // The wait was interrupted
            return nullptr;
        }

        // We only process the last packet - any others will probably be duplicates from an impatient client.
        return this->resolveCommandPacket(rawPackets.back());
    }

    std::unique_ptr<CommandPacket> GdbRspDebugServer::resolveCommandPacket(const RawPacketType& rawPacket) {
        if (rawPacket.size() == 5 && rawPacket[1] == 0x03) {
            // Interrupt request
            return std::make_unique<CommandPackets::InterruptExecution>(rawPacket);
        }

        const auto rawPacketString = std::string(rawPacket.begin(), rawPacket.end());

        if (rawPacketString.size() >= 2) {
            /*
             * First byte of the raw packet will be 0x24 ('$'), so find() should return 1, not 0, when
             * looking for a command identifier string.
             */
            if (rawPacketString.find("qSupported") == 1) {
                return std::make_unique<CommandPackets::SupportedFeaturesQuery>(rawPacket);
            }

            if (rawPacketString[1] == 'g' || rawPacketString[1] == 'p') {
                return std::make_unique<CommandPackets::ReadRegisters>(rawPacket);
            }

            if (rawPacketString[1] == 'P') {
                return std::make_unique<CommandPackets::WriteRegister>(rawPacket);
            }

            if (rawPacketString[1] == 'c') {
                return std::make_unique<CommandPackets::ContinueExecution>(rawPacket);
            }

            if (rawPacketString[1] == 's') {
                return std::make_unique<CommandPackets::StepExecution>(rawPacket);
            }

            if (rawPacketString[1] == 'Z') {
                return std::make_unique<CommandPackets::SetBreakpoint>(rawPacket);
            }

            if (rawPacketString[1] == 'z') {
                return std::make_unique<CommandPackets::RemoveBreakpoint>(rawPacket);
            }

            if (rawPacketString.find("qRcmd") == 1) {
                // This is a monitor packet
                auto monitorCommand = std::make_unique<CommandPackets::Monitor>(rawPacket);

                if (monitorCommand->command == "reset") {
                    return std::make_unique<CommandPackets::ResetTarget>(std::move(*(monitorCommand.get())));
                }

                return monitorCommand;
            }
        }

        return std::make_unique<CommandPacket>(rawPacket);
    }

    void GdbRspDebugServer::terminateActiveDebugSession() {
        if (!this->activeDebugSession.has_value()) {
            return;
        }

        this->activeDebugSession->terminate();
        this->activeDebugSession = std::nullopt;

        EventManager::triggerEvent(std::make_shared<Events::DebugSessionFinished>());
    }

    void GdbRspDebugServer::onTargetControllerStateChanged(const Events::TargetControllerStateChanged& event) {
        if (event.state == TargetControllerState::SUSPENDED && this->activeDebugSession.has_value()) {
            Logger::warning("TargetController suspended unexpectedly - terminating debug session");
            this->terminateActiveDebugSession();
        }
    }

    void GdbRspDebugServer::onTargetExecutionStopped(const Events::TargetExecutionStopped&) {
        try {
            if (this->activeDebugSession.has_value() && this->activeDebugSession->waitingForBreak) {
                this->activeDebugSession->connection.writePacket(
                    ResponsePackets::TargetStopped(Signal::TRAP)
                );
                this->activeDebugSession->waitingForBreak = false;
            }

        } catch (const ClientDisconnected&) {
            Logger::info("GDB RSP client disconnected");
            this->terminateActiveDebugSession();
            return;

        } catch (const ClientCommunicationError& exception) {
            Logger::error(
                "GDB RSP client communication error - " + exception.getMessage() + " - closing connection"
            );
            this->terminateActiveDebugSession();
            return;

        } catch (const DebugServerInterrupted&) {
            // Server was interrupted
            Logger::debug("GDB RSP interrupted");
            return;
        }
    }
}