From 4a7993cf353ebffacf5e26a7fa56e5b2277871e7 Mon Sep 17 00:00:00 2001
From: Fabian Posch <fabian@posch.tech>
Date: Mon, 8 Jan 2024 17:11:58 -0500
Subject: [PATCH] implement worker threads and download thread skelleton

---
 include/actsim_agent/actsim_agent.hpp |  5 ++
 src/actsim_agent/actsim_agent.cpp     | 99 ++++++++++++++++++++++++++-
 2 files changed, 102 insertions(+), 2 deletions(-)

diff --git a/include/actsim_agent/actsim_agent.hpp b/include/actsim_agent/actsim_agent.hpp
index 658ca1b..e919477 100644
--- a/include/actsim_agent/actsim_agent.hpp
+++ b/include/actsim_agent/actsim_agent.hpp
@@ -1,3 +1,4 @@
+
 /*************************************************************************
  *
  *  This file is part of the ACT library
@@ -27,6 +28,10 @@
 
 #include <db_types.hpp>
 
+#define DATABASE_VERSION 2
+
 int start_agent(db::db_credentials_t db_cred, size_t worker_processes);
 
+void sigint_handler(int signal);
+
 #endif
diff --git a/src/actsim_agent/actsim_agent.cpp b/src/actsim_agent/actsim_agent.cpp
index 4618cc9..45790af 100644
--- a/src/actsim_agent/actsim_agent.cpp
+++ b/src/actsim_agent/actsim_agent.cpp
@@ -23,9 +23,104 @@
  */
 
 #include <iostream>
+#include <thread>
+#include <csignal>
+#include <atomic>
+#include <db_types.hpp>
+#include <db_client.hpp>
+#include "worker.hpp"
+#include "util.h"
 #include "actsim_agent.hpp"
 
+// flag indicating program stop to the worker threads
+volatile std::atomic_bool stop_requested(false);
+volatile std::atomic_bool immediate_stop(false);
+
 int start_agent(db::db_credentials_t db_cred, size_t worker_processes) {
-    std::cout << "Hello world from the agent." << std::endl;
+
+    DEBUG_PRINT("Agent asked to start with " + std::to_string(worker_processes) + " worker threads.");
+
+    // this will hold the ID of the task a given thread is currently working on
+    db::uuid_t worker_tasks[worker_processes];
+
+    // inform the database about which database version we are implementing
+    db_cred.version = DATABASE_VERSION;
+
+    // First we check that we can talk to the database. No reason to spin up if there is no one to talk to.
+    auto con = std::make_unique<db::Connection>(db_cred);
+    if (!con->connect()) {
+        std::cerr << "Could not connect to database. Aborting." << std::endl;
+        return 1;
+    }
+
+    // register the abort signal to stop the program
+    std::signal(SIGINT, sigint_handler);
+
+    // now we create the worker threads which will host our worker processes
+    std::vector<std::unique_ptr<Worker>> workers;
+
+    DEBUG_PRINT("Starting workers...");
+
+    for (size_t i = 0; i < worker_processes; i++) {
+        auto worker = std::make_unique<Worker>(stop_requested);
+        worker->start();
+        workers.emplace_back(std::move(worker));
+    }
+
+    // Spawn the upload thread
+    auto upload_thread = std::make_unique<std::thread>(run_upload);
+
+    // Run loop feeding the threads
+    while (!stop_requested.load(std::memory_order_relaxed)) {
+        //fill_queue();
+
+        // make sure the tasks the workers are performing haven't been halted
+        for (auto& worker : workers) {
+            if (task_halted(worker->get_current_task())) {
+                worker->cancel_current();
+            }
+        }
+    }
+
+    if (immediate_stop.load(std::memory_order_relaxed)) {
+        for (auto& worker : workers) {
+            worker->cancel_current();
+        }
+    }
+
+    DEBUG_PRINT("Control thread is finished, waiting for workers to stop...");
+
+    // wait for the workers to finish
+    for (auto& worker : workers) {
+        worker->join();
+    }
+
+    // wait for the upload to finish
+    upload_thread->join();
+
     return 0;
-}
\ No newline at end of file
+}
+
+void sigint_handler(int signal) {
+
+    if (signal != SIGINT) return;
+
+    if (stop_requested) {
+        immediate_stop.store(true, std::memory_order_relaxed);
+
+        std::cout << "Stopping all workers immediately and closing open tasks." << std::endl;
+    } else {
+        stop_requested.store(true, std::memory_order_relaxed);
+
+        std::cout << "Finishing all running simulations, then closing the agent." << std::endl;
+        std::cout << "To stop immediately instead, press Ctrl+C again." << std::endl;
+    }
+}
+
+bool task_halted(db::uuid_t task) {
+    return false;
+}
+
+void run_upload() {
+
+}