// yabridge: a Wine VST bridge
// Copyright (C) 2020  Robbert van der Helm
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

#include "wine-bridge.h"

#include <iostream>

#include <boost/filesystem.hpp>

#include "../common/communication.h"
#include "../common/events.h"

namespace fs = boost::filesystem;

/**
 * A function pointer to what should be the entry point of a VST plugin.
 */
using VstEntryPoint = AEffect*(VST_CALL_CONV*)(audioMasterCallback);

/**
 * This ugly global is needed so we can get the instance of a `Brdige` class
 * from an `AEffect` when it performs a host callback during its initialization.
 */
WineBridge* current_bridge_instance = nullptr;

intptr_t VST_CALL_CONV
host_callback_proxy(AEffect*, int, int, intptr_t, void*, float);

// We need to use the `CreateThread` WinAPI functions instead of `std::thread`
// to use the correct calling conventions within threads. Otherwise we'll get
// some rare and impossible to debug data races in some particular plugins.
uint32_t WINAPI handle_dispatch_midi_events_proxy(void*);
uint32_t WINAPI handle_parameters_proxy(void*);
uint32_t WINAPI handle_process_replacing_proxy(void*);

/**
 * Fetch the WineBridge instance stored in one of the two pointers reserved
 * for the host of the hosted VST plugin. This is sadly needed as a workaround
 * to avoid using globals since we need free function pointers to interface with
 * the VST C API.
 */
WineBridge& get_bridge_instance(const AEffect* plugin) {
    // This is needed during the initialization of the plugin since we can only
    // add our own pointer after it's done initializing
    if (current_bridge_instance != nullptr) {
        // This should only be used during initialization
        assert(plugin == nullptr || plugin->ptr1 == nullptr);
        return *current_bridge_instance;
    }

    return *static_cast<WineBridge*>(plugin->ptr1);
}

WineBridge::WineBridge(std::string plugin_dll_path,
                       std::string socket_endpoint_path)
    : plugin_handle(LoadLibrary(plugin_dll_path.c_str()), FreeLibrary),
      io_context(),
      socket_endpoint(socket_endpoint_path),
      host_vst_dispatch(io_context),
      host_vst_dispatch_midi_events(io_context),
      vst_host_callback(io_context),
      host_vst_parameters(io_context),
      host_vst_process_replacing(io_context),
      vst_host_aeffect(io_context) {
    // Got to love these C APIs
    if (plugin_handle == nullptr) {
        throw std::runtime_error("Could not load the Windows .dll file at '" +
                                 plugin_dll_path + "'");
    }

    // VST plugin entry point functions should be called `VSTPluginMain`, but
    // there are some older deprecated names that legacy plugins may still use
    VstEntryPoint vst_entry_point = nullptr;
    for (auto name : {"VSTPluginMain", "main_plugin", "main"}) {
        vst_entry_point =
            reinterpret_cast<VstEntryPoint>(reinterpret_cast<size_t>(
                GetProcAddress(plugin_handle.get(), name)));

        if (vst_entry_point != nullptr) {
            break;
        }
    }
    if (vst_entry_point == nullptr) {
        throw std::runtime_error(
            "Could not find a valid VST entry point for '" + plugin_dll_path +
            "'.");
    }

    // It's very important that these sockets are accepted to in the same order
    // in the Linux plugin
    host_vst_dispatch.connect(socket_endpoint);
    host_vst_dispatch_midi_events.connect(socket_endpoint);
    vst_host_callback.connect(socket_endpoint);
    host_vst_parameters.connect(socket_endpoint);
    host_vst_process_replacing.connect(socket_endpoint);
    vst_host_aeffect.connect(socket_endpoint);

    // Initialize after communication has been set up
    // We'll try to do the same `get_bridge_isntance` trick as in
    // `plugin/plugin.cpp`, but since the plugin will probably call the host
    // callback while it's initializing we sadly have to use a global here.
    current_bridge_instance = this;
    plugin = vst_entry_point(host_callback_proxy);
    if (plugin == nullptr) {
        throw std::runtime_error("VST plugin at '" + plugin_dll_path +
                                 "' failed to initialize.");
    }

    // We only needed this little hack during initialization
    current_bridge_instance = nullptr;
    plugin->ptr1 = this;

    // Send the plugin's information to the Linux VST plugin. Any updates during
    // runtime are handled using the `audioMasterIOChanged` host callback.
    write_object(vst_host_aeffect, *plugin);

    // This works functionally identically to the `handle_dispatch()` function
    // below, but this socket will only handle MIDI events. This is needed
    // because of Win32 API limitations.
    dispatch_midi_events_handler =
        Win32Thread(handle_dispatch_midi_events_proxy, this);

    parameters_handler = Win32Thread(handle_parameters_proxy, this);

    process_replacing_handler =
        Win32Thread(handle_process_replacing_proxy, this);
}

void WineBridge::handle_dispatch() {
    using namespace std::placeholders;

    // For our communication we use simple threads and blocking operations
    // instead of asynchronous IO since communication has to be handled in
    // lockstep anyway
    try {
        while (true) {
            receive_event(host_vst_dispatch, std::nullopt,
                          passthrough_event(
                              plugin, std::bind(&WineBridge::dispatch_wrapper,
                                                this, _1, _2, _3, _4, _5, _6)));

            // Because of the way the Win32 API works we have to process events
            // on the same thread as the one the window was created on, and that
            // thread is the thread that's handling dispatcher calls.
            if (editor.has_value()) {
                // This will handle Win32 events similar to the loop below, and
                // it will also handle any X11 events.
                editor->handle_events();
            } else {
                MSG msg;

                // Since some plugins rely on the Win32 message API even for
                // non-editor related tasks (such as deferring the loading of
                // presets using a timer), we have to run a message loop even
                // when the editor is closed.
                while (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE)) {
                    TranslateMessage(&msg);
                    DispatchMessage(&msg);
                }
            }
        }
    } catch (const boost::system::system_error&) {
        // The plugin has cut off communications, so we can shut down this host
        // application
    }
}

[[noreturn]] void WineBridge::handle_dispatch_midi_events() {
    while (true) {
        receive_event(
            host_vst_dispatch_midi_events, std::nullopt, [&](Event& event) {
                if (BOOST_LIKELY(event.opcode == effProcessEvents)) {
                    // For 99% of the plugins we can just call
                    // `effProcessReplacing()` and be done with it, but a select
                    // few plugins (I could only find Kontakt that does this)
                    // don't actually make copies of the events they receive and
                    // only store pointers, meaning that they have to live at
                    // least until the next audio buffer gets processed. We're
                    // not using `passhtourhg_events()` here directly because we
                    // need to store a copy of the `DynamicVstEvents` struct
                    // before passing the generated `VstEvents` object to the
                    // plugin.
                    std::lock_guard lock(next_buffer_midi_events_mutex);

                    next_audio_buffer_midi_events.push_back(
                        std::get<DynamicVstEvents>(event.payload));
                    DynamicVstEvents& events =
                        next_audio_buffer_midi_events.back();

                    // Exact same handling as in `passthrough_event`, apart from
                    // making a copy of the events first
                    const intptr_t return_value = plugin->dispatcher(
                        plugin, event.opcode, event.index, event.value,
                        &events.as_c_events(), event.option);

                    EventResult response{return_value, nullptr, std::nullopt};

                    return response;
                } else {
                    using namespace std::placeholders;

                    std::cerr << "[Warning] Received non-MIDI "
                                 "event on MIDI processing thread"
                              << std::endl;

                    // Maybe this should just be a hard error instead, since it
                    // should never happen
                    return passthrough_event(
                        plugin, std::bind(&WineBridge::dispatch_wrapper, this,
                                          _1, _2, _3, _4, _5, _6))(event);
                }
            });
    }
}

[[noreturn]] void WineBridge::handle_parameters() {
    while (true) {
        // Both `getParameter` and `setParameter` functions are passed
        // through on this socket since they have a lot of overlap. The
        // presence of the `value` field tells us which one we're dealing
        // with.
        auto request = read_object<Parameter>(host_vst_parameters);
        if (request.value.has_value()) {
            // `setParameter`
            plugin->setParameter(plugin, request.index, request.value.value());

            ParameterResult response{std::nullopt};
            write_object(host_vst_parameters, response);
        } else {
            // `getParameter`
            float value = plugin->getParameter(plugin, request.index);

            ParameterResult response{value};
            write_object(host_vst_parameters, response);
        }
    }
}

[[noreturn]] void WineBridge::handle_process_replacing() {
    std::vector<std::vector<float>> output_buffers(plugin->numOutputs);

    while (true) {
        auto request = read_object<AudioBuffers>(host_vst_process_replacing,
                                                 process_buffer);

        // The process functions expect a `float**` for their inputs and
        // their outputs
        std::vector<float*> inputs;
        for (auto& buffer : request.buffers) {
            inputs.push_back(buffer.data());
        }

        // We reuse the buffers to avoid some unnecessary heap allocations,
        // so we need to make sure the buffers are large enough since
        // plugins can change their output configuration
        std::vector<float*> outputs;
        output_buffers.resize(plugin->numOutputs);
        for (auto& buffer : output_buffers) {
            buffer.resize(request.sample_frames);
            outputs.push_back(buffer.data());
        }

        // Let the plugin process the MIDI events that were received since the
        // last buffer, and then clean up those events. This approach should not
        // be needed but Kontakt only stores pointers to rather than copies of
        // the events.
        {
            std::lock_guard lock(next_buffer_midi_events_mutex);

            // Any plugin made in the last fifteen years or so should support
            // `processReplacing`. In the off chance it does not we can just
            // emulate this behavior ourselves.
            if (plugin->processReplacing != nullptr) {
                plugin->processReplacing(plugin, inputs.data(), outputs.data(),
                                         request.sample_frames);
            } else {
                // If we zero out this buffer then the behavior is the same as
                // `processReplacing``
                for (std::vector<float>& buffer : output_buffers) {
                    std::fill(buffer.begin(), buffer.end(), 0.0);
                }

                plugin->process(plugin, inputs.data(), outputs.data(),
                                request.sample_frames);
            }

            next_audio_buffer_midi_events.clear();
        }

        AudioBuffers response{output_buffers, request.sample_frames};
        write_object(host_vst_process_replacing, response, process_buffer);
    }
}

intptr_t WineBridge::dispatch_wrapper(AEffect* plugin,
                                      int opcode,
                                      int index,
                                      intptr_t value,
                                      void* data,
                                      float option) {
    // We have to intercept GUI open calls since we can't use
    // the X11 window handle passed by the host
    switch (opcode) {
        case effEditOpen: {
            // Create a Win32 window through Wine, embed it into the window
            // provided by the host, and let the plugin embed itself into the
            // Wine window
            const auto x11_handle = reinterpret_cast<size_t>(data);
            editor.emplace("yabridge plugin", plugin, x11_handle);

            return plugin->dispatcher(plugin, opcode, index, value,
                                      editor->win32_handle.get(), option);
        } break;
        case effEditClose: {
            const intptr_t return_value =
                plugin->dispatcher(plugin, opcode, index, value, data, option);

            // Cleanup is handled through RAII
            editor = std::nullopt;

            return return_value;
        } break;
        default:
            return plugin->dispatcher(plugin, opcode, index, value, data,
                                      option);
            break;
    }
}

class HostCallbackDataConverter : DefaultDataConverter {
   public:
    HostCallbackDataConverter(AEffect* plugin,
                              std::optional<VstTimeInfo>& time_info)
        : plugin(plugin), time_info(time_info) {}

    EventPayload read(const int opcode,
                      const int index,
                      const intptr_t value,
                      const void* data) {
        switch (opcode) {
            case audioMasterGetTime:
                return WantsVstTimeInfo{};
                break;
            case audioMasterIOChanged:
                // This is a helpful event that indicates that the VST plugin's
                // `AEffect` struct has changed. Writing these results back is
                // done inside of `passthrough_event`.
                return AEffect(*plugin);
                break;
            case audioMasterProcessEvents:
                return DynamicVstEvents(*static_cast<const VstEvents*>(data));
                break;
            // We detect whether an opcode should return a string by checking
            // whether there's a zeroed out buffer behind the void pointer. This
            // works for any host, but not all plugins zero out their buffers.
            case audioMasterGetVendorString:
            case audioMasterGetProductString:
                return WantsString{};
                break;
            default:
                return DefaultDataConverter::read(opcode, index, value, data);
                break;
        }
    }

    std::optional<EventPayload> read_value(const int opcode,
                                           const intptr_t value) {
        return DefaultDataConverter::read_value(opcode, value);
    }

    void write(const int opcode, void* data, const EventResult& response) {
        switch (opcode) {
            case audioMasterGetTime:
                // Write the returned `VstTimeInfo` struct into a field and make
                // the function return a poitner to it in the function below.
                // Depending on whether the host supported the requested time
                // information this operations returns either a null pointer or
                // a pointer to a `VstTimeInfo` object.
                if (std::holds_alternative<std::nullptr_t>(response.payload)) {
                    time_info = std::nullopt;
                } else {
                    time_info = std::get<VstTimeInfo>(response.payload);
                }
                break;
            default:
                DefaultDataConverter::write(opcode, data, response);
                break;
        }
    }

    intptr_t return_value(const int opcode, const intptr_t original) {
        switch (opcode) {
            case audioMasterGetTime: {
                // Return a pointer to the `VstTimeInfo` object written in the
                // function above
                VstTimeInfo* time_info_pointer = nullptr;
                if (time_info.has_value()) {
                    time_info_pointer = &time_info.value();
                }

                return reinterpret_cast<intptr_t>(time_info_pointer);
            } break;
            default:
                return DefaultDataConverter::return_value(opcode, original);
                break;
        }
    }

    void write_value(const int opcode,
                     intptr_t value,
                     const EventResult& response) {
        return DefaultDataConverter::write_value(opcode, value, response);
    }

   private:
    AEffect* plugin;
    std::optional<VstTimeInfo>& time_info;
};

intptr_t WineBridge::host_callback(AEffect* effect,
                                   int opcode,
                                   int index,
                                   intptr_t value,
                                   void* data,
                                   float option) {
    HostCallbackDataConverter converter(effect, time_info);
    return send_event(vst_host_callback, host_callback_mutex, converter,
                      std::nullopt, opcode, index, value, data, option);
}

intptr_t VST_CALL_CONV host_callback_proxy(AEffect* effect,
                                           int opcode,
                                           int index,
                                           intptr_t value,
                                           void* data,
                                           float option) {
    return get_bridge_instance(effect).host_callback(effect, opcode, index,
                                                     value, data, option);
}

uint32_t WINAPI handle_dispatch_midi_events_proxy(void* instance) {
    static_cast<WineBridge*>(instance)->handle_dispatch_midi_events();
}

uint32_t WINAPI handle_parameters_proxy(void* instance) {
    static_cast<WineBridge*>(instance)->handle_parameters();
}

uint32_t WINAPI handle_process_replacing_proxy(void* instance) {
    static_cast<WineBridge*>(instance)->handle_process_replacing();
}