Encapsulate individual/group handling differences

This cleans up the PluginBridge significantly by getting rid of all
fields and handling that was only needed for connecting to plugin
groups. This was also the last thing I wanted to refactor before
releasing the plugin groups feature with yabridge 1.2.

src/plugin/plugin-bridge.h

@@ -20,14 +20,12 @@
 
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
-#include <boost/asio/streambuf.hpp>
-#include <boost/process/child.hpp>
 #include <mutex>
 #include <thread>
 
 #include "../common/logging.h"
 #include "configuration.h"
-#include "utils.h"
+#include "host-process.h"
 
 /**
  * This handles the communication between the Linux native VST plugin and the
@@ -86,16 +84,6 @@ class PluginBridge {
      * The path to the .dll being loaded in the Wine VST host.
      */
     const boost::filesystem::path vst_plugin_path;
-    /**
-     * Whether the plugin is 64-bit or 32-bit.
-     */
-    const PluginArchitecture vst_plugin_arch;
-    /**
-     * The path to the host application (i.e. a path to either
-     * `yabridge-host.exe` or `yabridge-host-32.exe`). The host application will
-     * be chosen depending on the architecture of the VST plugin .dll file.
-     */
-    const boost::filesystem::path vst_host_path;
 
     /**
      * This AEffect struct will be populated using the data passed by the Wine
@@ -105,31 +93,6 @@ class PluginBridge {
     AEffect plugin;
 
    private:
-    /**
-     * Write output from an async pipe to the log on a line by line basis.
-     * Useful for logging the Wine process's STDOUT and STDERR streams.
-     *
-     * @param pipe The pipe to read from.
-     * @param buffer The stream buffer to write to.
-     * @param prefix Text to prepend to the line before writing to the log.
-     */
-    void async_log_pipe_lines(patched_async_pipe& pipe,
-                              boost::asio::streambuf& buffer,
-                              std::string prefix = "");
-
-    /**
-     * Launch the Wine VST host to host the plugin. When using plugin groups,
-     * this will first try to connect to the plugin group's socket (determined
-     * based on group name, Wine prefix and architecture). If that fails, it
-     * will launch a new, detached group host process. This will likely outlive
-     * this plugin instance if multiple instances of yabridge using the same
-     * plugin group are in use. In the event that two yabridge instances are
-     * initialized at the same time and both instances spawn their own group
-     * host process, then the later one will simply terminate gracefully after
-     * it fails to listen on the socket.
-     */
-    void launch_vst_host();
-
     /**
      * Format and log all relevant debug information during initialization.
      */
@@ -212,49 +175,17 @@ class PluginBridge {
      */
     const std::string wine_version;
 
-    boost::asio::streambuf wine_stdout_buffer;
-    boost::asio::streambuf wine_stderr_buffer;
-    /**
-     * The STDOUT stream of the Wine process we can forward to the logger.
-     */
-    patched_async_pipe wine_stdout;
-    /**
-     * The STDERR stream of the Wine process we can forward to the logger.
-     */
-    patched_async_pipe wine_stderr;
-    /**
-     * Runs the Boost.Asio `io_context` thread for logging the Wine process
-     * STDOUT and STDERR messages.
-     */
-    std::thread wine_io_handler;
-
     /**
      * The Wine process hosting the Windows VST plugin.
      *
      * @see launch_vst_host
      */
-    boost::process::child vst_host;
+    std::unique_ptr<HostProcess> vst_host;
     /**
-     * The PID of the vst host process. Needed for checking whether the group
-     * host is still active if we are connecting to an already running group
-     * host instance.
-     *
-     * TODO: Remove this after encapsulating the minor differences in individual
-     *       and group host handling
+     * Runs the Boost.Asio `io_context` thread for logging the Wine process
+     * STDOUT and STDERR messages.
      */
-    pid_t vst_host_pid;
-    /**
-     * A thread that waits for the group host to have started and then ask it to
-     * host our plugin. This is used to defer the request since it may take a
-     * little while until the group host process is up and running. This way we
-     * don't have to delay the rest of the initialization process.
-     *
-     * TODO: Remove this after encapsulating the minor differences in individual
-     *       and group host handling
-     * TODO: Replace this with inotify to prevent delays and to reduce wasting
-     *       resources
-     */
-    std::thread group_host_connect_handler;
+    std::thread wine_io_handler;
 
     /**
      * A scratch buffer for sending and receiving data during `process` and