// 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 "communication.h"

#include <random>

#include "utils.h"

namespace fs = boost::filesystem;

/**
 * Used for generating random identifiers.
 */
constexpr char alphanumeric_characters[] =
    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

EventPayload DefaultDataConverter::read(const int /*opcode*/,
                                        const int /*index*/,
                                        const intptr_t /*value*/,
                                        const void* data) const {
    if (!data) {
        return nullptr;
    }

    // This is a simple fallback that will work in almost every case.
    // Because some plugins don't zero out their string buffers when sending
    // host callbacks, we will explicitely list all callbacks that expect a
    // string in `DispatchDataConverter` adn `HostCallbackDataConverter`.
    const char* c_string = static_cast<const char*>(data);
    if (c_string[0] != 0) {
        return std::string(c_string);
    } else {
        return WantsString{};
    }
}

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

void DefaultDataConverter::write(const int /*opcode*/,
                                 void* data,
                                 const EventResult& response) const {
    // The default behavior is to handle this as a null terminated C-style
    // string
    std::visit(overload{[&](const auto&) {},
                        [&](const std::string& s) {
                            char* output = static_cast<char*>(data);

                            // We use std::string for easy transport but in
                            // practice we're always writing null terminated
                            // C-style strings
                            std::copy(s.begin(), s.end(), output);
                            output[s.size()] = 0;
                        }},
               response.payload);
}

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

intptr_t DefaultDataConverter::return_value(const int /*opcode*/,
                                            const intptr_t original) const {
    return original;
}

EventHandler::EventHandler(
    boost::asio::io_context& io_context,
    boost::asio::local::stream_protocol::endpoint endpoint,
    bool listen)
    : io_context(io_context), endpoint(endpoint), socket(io_context) {
    if (listen) {
        fs::create_directories(fs::path(endpoint.path()).parent_path());
        acceptor.emplace(io_context, endpoint);
    }
}

void EventHandler::connect() {
    if (acceptor) {
        acceptor->accept(socket);

        // As mentioned in `acceptor's` docstring, this acceptor will be
        // recreated in `receive()` on another context, and potentially on the
        // other side of the connection in the case of `vst_host_callback`
        acceptor.reset();
        fs::remove(endpoint.path());
    } else {
        socket.connect(endpoint);
    }
}

void EventHandler::close() {
    socket.shutdown(boost::asio::local::stream_protocol::socket::shutdown_both);
    socket.close();
}

Sockets::Sockets(boost::asio::io_context& io_context,
                 const boost::filesystem::path& endpoint_base_dir,
                 bool listen)
    : base_dir(endpoint_base_dir),
      host_vst_dispatch(io_context,
                        (base_dir / "host_vst_dispatch.sock").string(),
                        listen),
      host_vst_dispatch_midi_events(
          io_context,
          (base_dir / "host_vst_dispatch_midi_events.sock").string(),
          listen),
      vst_host_callback(io_context,
                        (base_dir / "vst_host_callback.sock").string(),
                        listen),
      host_vst_parameters(io_context),
      host_vst_process_replacing(io_context),
      host_vst_control(io_context),
      host_vst_parameters_endpoint(
          (base_dir / "host_vst_parameters.sock").string()),
      host_vst_process_replacing_endpoint(
          (base_dir / "host_vst_process_replacing.sock").string()),
      host_vst_control_endpoint((base_dir / "host_vst_control.sock").string()) {
    if (listen) {
        fs::create_directories(base_dir);

        acceptors = Acceptors{
            .host_vst_parameters{io_context, host_vst_parameters_endpoint},
            .host_vst_process_replacing{io_context,
                                        host_vst_process_replacing_endpoint},
            .host_vst_control{io_context, host_vst_control_endpoint},
        };
    }
}

Sockets::~Sockets() {
    // Only clean if we're the ones who have created these files, although it
    // should not cause any harm to also do this on the Wine side
    if (acceptors) {
        try {
            fs::remove_all(base_dir);
        } catch (const fs::filesystem_error&) {
            // There should not be any filesystem errors since only one side
            // removes the files, but if we somehow can't delete the file then
            // we can just silently ignore this
        }
    }
}

void Sockets::connect() {
    host_vst_dispatch.connect();
    host_vst_dispatch_midi_events.connect();
    vst_host_callback.connect();
    if (acceptors) {
        acceptors->host_vst_parameters.accept(host_vst_parameters);
        acceptors->host_vst_process_replacing.accept(
            host_vst_process_replacing);
        acceptors->host_vst_control.accept(host_vst_control);
    } else {
        host_vst_parameters.connect(host_vst_parameters_endpoint);
        host_vst_process_replacing.connect(host_vst_process_replacing_endpoint);
        host_vst_control.connect(host_vst_control_endpoint);
    }
}

boost::filesystem::path generate_endpoint_base(const std::string& plugin_name) {
    fs::path temp_directory = get_temporary_directory();

    std::random_device random_device;
    std::mt19937 rng(random_device());
    fs::path candidate_endpoint;
    do {
        std::string random_id;
        std::sample(
            alphanumeric_characters,
            alphanumeric_characters + strlen(alphanumeric_characters) - 1,
            std::back_inserter(random_id), 8, rng);

        // We'll get rid of the file descriptors immediately after accepting the
        // sockets, so putting them inside of a subdirectory would only leave
        // behind an empty directory
        std::ostringstream socket_name;
        socket_name << "yabridge-" << plugin_name << "-" << random_id;

        candidate_endpoint = temp_directory / socket_name.str();
    } while (fs::exists(candidate_endpoint));

    return candidate_endpoint;
}