From 26114aad5f9d95e0b945ca0bb862729ae6ee2766 Mon Sep 17 00:00:00 2001
From: blue <blue@macaw.me>
Date: Sun, 31 Dec 2023 14:10:04 -0300
Subject: [PATCH] beginning of the scheduler

---
 server/server.cpp          | 23 ++++++++++++
 server/server.h            |  2 +
 taskmanager/CMakeLists.txt |  2 +
 taskmanager/scheduler.cpp  | 75 ++++++++++++++++++++++++++++++++++++++
 taskmanager/scheduler.h    | 48 ++++++++++++++++++++++++
 utils/helpers.h            |  7 ++++
 6 files changed, 157 insertions(+)
 create mode 100644 taskmanager/scheduler.cpp
 create mode 100644 taskmanager/scheduler.h

diff --git a/server/server.cpp b/server/server.cpp
index dbb99f1..c4a2f60 100644
--- a/server/server.cpp
+++ b/server/server.cpp
@@ -38,6 +38,7 @@ Server::Server():
     router(std::make_shared<Router>()),
     pool(DB::Pool::create()),
     taskManager(std::make_shared<TM::Manager>()),
+    scheduler(std::make_shared<TM::Scheduler>(taskManager)),
     sessions()
 {
     std::cout << "Startig pica..." << std::endl;
@@ -65,6 +66,28 @@ void Server::run(int socketDescriptor) {
     router->addRoute(std::make_unique<Handler::Login>(shared_from_this()));
 
     taskManager->start();
+    scheduler->start();
+
+    scheduler->schedule([]() {
+        std::cout << "5000" << std::endl;
+    }, TM::Scheduler::Delay(5000));
+    scheduler->schedule([]() {
+        std::cout << "2000" << std::endl;
+    }, TM::Scheduler::Delay(2000));
+    scheduler->schedule([]() {
+        std::cout << "6000" << std::endl;
+    }, TM::Scheduler::Delay(6000));
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(500));
+
+    scheduler->schedule([]() {
+        std::cout << "2000 + 500" << std::endl;
+    }, TM::Scheduler::Delay(2000));
+    std::this_thread::sleep_for(std::chrono::milliseconds(100));
+
+    scheduler->schedule([]() {
+        std::cout << "1000 + 600" << std::endl;
+    }, TM::Scheduler::Delay(1000));
 
     while (!terminating) {
         std::unique_ptr<Request> request = std::make_unique<Request>();
diff --git a/server/server.h b/server/server.h
index 72f7fe6..4402cfb 100644
--- a/server/server.h
+++ b/server/server.h
@@ -26,6 +26,7 @@
 #include "utils/helpers.h"
 #include "config.h"
 #include "taskmanager/manager.h"
+#include "taskmanager/scheduler.h"
 
 class Server : public std::enable_shared_from_this<Server> {
 public:
@@ -52,5 +53,6 @@ private:
     std::shared_ptr<Router> router;
     std::shared_ptr<DB::Pool> pool;
     std::shared_ptr<TM::Manager> taskManager;
+    std::shared_ptr<TM::Scheduler> scheduler;
     Sessions sessions;
 };
diff --git a/taskmanager/CMakeLists.txt b/taskmanager/CMakeLists.txt
index 2149fd4..7a8c2c3 100644
--- a/taskmanager/CMakeLists.txt
+++ b/taskmanager/CMakeLists.txt
@@ -5,12 +5,14 @@ set(HEADERS
     manager.h
     job.h
     route.h
+    scheduler.h
 )
 
 set(SOURCES
     manager.cpp
     job.cpp
     route.cpp
+    scheduler.cpp
 )
 
 target_sources(${PROJECT_NAME} PRIVATE ${SOURCES})
diff --git a/taskmanager/scheduler.cpp b/taskmanager/scheduler.cpp
new file mode 100644
index 0000000..45a8dc0
--- /dev/null
+++ b/taskmanager/scheduler.cpp
@@ -0,0 +1,75 @@
+//SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
+//SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "scheduler.h"
+
+TM::Scheduler::Scheduler (std::weak_ptr<Manager> manager):
+    manager(manager),
+    queue(),
+    mutex(),
+    cond(),
+    thread(nullptr),
+    running(false)
+{}
+
+TM::Scheduler::~Scheduler () {
+    stop();
+}
+
+void TM::Scheduler::start () {
+    std::unique_lock lock(mutex);
+    if (running)
+        return;
+
+    running = true;
+    thread = std::make_unique<std::thread>(&Scheduler::loop, this);
+}
+
+void TM::Scheduler::stop () {
+    std::unique_lock lock(mutex);
+    if (!running)
+        return;
+
+    running = false;
+
+    lock.unlock();
+    cond.notify_all();
+    thread->join();
+
+    lock.lock();
+    thread.reset();
+}
+
+void TM::Scheduler::loop () {
+    while (running) {
+        std::unique_lock<std::mutex> lock(mutex);
+        if (queue.empty()) {
+            cond.wait(lock);
+            continue;
+        }
+
+        Time currentTime = std::chrono::steady_clock::now();
+        while (!queue.empty()) {
+            Time nextScheduledTime = queue.top().first;
+            if (nextScheduledTime > currentTime) {
+                cond.wait_until(lock, nextScheduledTime);
+                break;
+            }
+
+            Task task = queue.top().second;
+            queue.pop();
+            lock.unlock();
+            task();
+            lock.lock();
+        }
+    }
+}
+
+void TM::Scheduler::schedule (Task task, Delay delay) {
+    std::unique_lock lock(mutex);
+    Time time = std::chrono::steady_clock::now() + delay;
+    queue.emplace(time, task);
+
+    lock.unlock();
+    cond.notify_one();
+}
diff --git a/taskmanager/scheduler.h b/taskmanager/scheduler.h
new file mode 100644
index 0000000..40a0093
--- /dev/null
+++ b/taskmanager/scheduler.h
@@ -0,0 +1,48 @@
+//SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
+//SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <memory>
+#include <thread>
+#include <queue>
+#include <chrono>
+#include <functional>
+#include <mutex>
+#include <condition_variable>
+
+#include "manager.h"
+#include "utils/helpers.h"
+
+namespace TM {
+class Scheduler {
+public:
+    using Delay = std::chrono::milliseconds;
+    using Task = std::function<void()>;
+
+    Scheduler (std::weak_ptr<Manager> manager);
+    ~Scheduler ();
+
+    void start();
+    void stop();
+    void schedule(Task task, Delay delay);
+
+private:
+    void loop();
+
+private:
+    using Time = std::chrono::time_point<std::chrono::steady_clock>;
+    using Record = std::pair<Time, Task>;
+
+    std::weak_ptr<Manager> manager;
+    std::priority_queue<
+        Record,
+        std::vector<Record>,
+        FirstGreater<Record>
+    > queue;
+    std::mutex mutex;
+    std::condition_variable cond;
+    std::unique_ptr<std::thread> thread;
+    bool running;
+};
+}
diff --git a/utils/helpers.h b/utils/helpers.h
index 2c00151..7991346 100644
--- a/utils/helpers.h
+++ b/utils/helpers.h
@@ -15,3 +15,10 @@ void ltrim(std::string& string);
 void rtrim(std::string& string);
 void trim(std::string& string);
 std::string extract(std::string& string, std::string::size_type begin, std::string::size_type end);
+
+template <class T>
+struct FirstGreater {
+    bool operator () (T left, T right) {
+        return std::get<0>(left) > std::get<0>(right);
+    }
+};