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net/adc_netserver.h

@@ -0,0 +1,169 @@
+#pragma once
+
+/*
+
+ABSTRACT DEVICE COMPONENTS LIBRARY
+
+*/
+
+#include <filesystem>
+#if __has_include(<unistd.h>)  // POSIX
+#define FORK_EXISTS 1
+#include <sys/stat.h>
+#include <unistd.h>
+#include <cerrno>
+#endif
+
+#include <memory>
+
+
+namespace adc
+{
+
+
+/*  Server session and its abstract decorator  */
+
+template <typename ImplT>
+class AdcNetServerSession : std::enable_shared_from_this<AdcNetServerSession<ImplT>>
+{
+public:
+    using shared_ptr_t = std::shared_ptr<AdcNetServerSession>;
+    using weak_ptr_t = std::weak_ptr<AdcNetServerSession>;
+
+    template <typename... ImplCtorArgTs>
+    AdcNetServerSession(ImplCtorArgTs&&... ctor_args) : _implUptr(std::forward<ImplCtorArgTs>(ctor_args)...)
+    {
+    }
+
+
+    virtual ~AdcNetServerSession() = default;
+
+
+    auto sessionIdent() const
+    {
+        //
+        return _implUptr->_sessionIdent();
+    }
+
+
+    virtual void start()
+    {
+        //
+        _implUptr->start();
+    }
+
+    virtual void stop()
+    {
+        //
+        _implUptr->stop();
+    }
+
+protected:
+    std::unique_ptr<ImplT> _implUptr;
+};
+
+
+template <typename ImplT, std::derived_from<AdcNetServerSession<ImplT>> SessionT>
+class AdcNetServerSessionDecorator : public SessionT
+{
+public:
+    using SessionT::sessionIdent;
+
+    template <typename... ImplCtorArgTs>
+    AdcNetServerSessionDecorator(ImplCtorArgTs&&... ctor_args) : SessionT(std::forward<ImplCtorArgTs>(ctor_args)...)
+    {
+    }
+
+    virtual ~AdcNetServerSessionDecorator() = default;
+
+    virtual std::invoke_result_t<decltype(sessionIdent)> sessionIdent() const = 0;
+
+    virtual void start() = 0;
+
+    virtual void stop() = 0;
+};
+
+
+
+/*  Server  */
+
+template <typename ImplT>
+class AdcNetServer
+{
+protected:
+    std::unique_ptr<ImplT> _implUptr;
+
+public:
+    template <typename... ImplCtorArgTs>
+    AdcNetServer(ImplCtorArgTs&&... ctor_args) : _implUptr(std::make_unique<ImplT>(ctor_args)...)
+    {
+    }
+
+
+    virtual ~AdcNetServer() = default;
+
+
+    virtual void start() = 0;
+
+    virtual void stop() = 0;
+
+    template <typename SessionT>
+    void start() {};
+
+    template <typename SessionT>
+    void stop() {};
+
+    // run server as daemon (still only on POSIX OSes)
+    void daemonize()
+    {
+        daemonizePrepare();
+
+#ifdef FORK_EXISTS
+        // get TEMP directory in OS
+
+        auto tmp_path = std::filesystem::temp_directory_path();
+        if (tmp_path.empty()) {
+            tmp_path = std::filesystem::current_path().root_path();
+        }
+
+        // _ioContext.notify_fork(asio::execution_context::fork_prepare);
+
+        if (pid_t pid = fork()) {
+            if (pid > 0) {
+                exit(0);
+            } else {
+                throw std::system_error(errno, std::generic_category(), "CANNOT FORK 1-STAGE");
+            }
+        }
+
+        if (setsid() == -1) {
+            throw std::system_error(errno, std::generic_category(), "CANNOT FORK SETSID");
+        }
+
+        std::filesystem::current_path(tmp_path);
+
+        umask(0);
+
+        if (pid_t pid = fork()) {
+            if (pid > 0) {
+                exit(0);
+            } else {
+                throw std::system_error(errno, std::generic_category(), "CANNOT FORK 2-STAGE");
+            }
+        }
+
+        close(0);
+        close(1);
+        close(2);
+
+        // _ioContext.notify_fork(asio::io_context::fork_child);
+#endif
+        daemonizeFinalize();
+    }
+
+    virtual void daemonizePrepare() = 0;
+
+    virtual void daemonizeFinalize() = 0;
+};
+
+}  // namespace adc