From 42c6b111c8353c723ac4fb67779cf9018745e522 Mon Sep 17 00:00:00 2001
From: "Tristan B. Velloza Kildaire" <deavmi@redxen.eu>
Date: Sun, 1 Oct 2023 20:51:08 +0200
Subject: [PATCH] Migrate from libsnooze (#8)

* Dub

- Removed `libsnooze` dependency

* Queue

- Removed `libsnooze` imports

* Queue

- Added mutex+condition variable

* Queue

- Removed old `ensure()` call

* Queue

- Switched one thing over to mutex+condvar

* Queue

- Switched to using condition variable
- Added configurable slumber interval
---
 dub.json                   |   3 +-
 source/tristanable/queue.d | 117 +++++++++++++++++++++----------------
 2 files changed, 67 insertions(+), 53 deletions(-)

diff --git a/dub.json b/dub.json
index fd61123..1f2fe98 100644
--- a/dub.json
+++ b/dub.json
@@ -4,8 +4,7 @@
 	],
 	"copyright": "Copyright © 2023, Tristan B. Kildaire",
 	"dependencies": {
-		"bformat": ">=4.1.1",
-		"libsnooze": ">=1.3.0-beta"
+		"bformat": ">=4.1.1"
 	},
 	"description": "Tristanable network message queuing framework",
 	"homepage": "https://deavmi.assigned.network/projects/tristanable",
diff --git a/source/tristanable/queue.d b/source/tristanable/queue.d
index 0271934..00cddd9 100644
--- a/source/tristanable/queue.d
+++ b/source/tristanable/queue.d
@@ -3,14 +3,12 @@
  */
 module tristanable.queue;
 
-// TODO: Examine the below import which seemingly fixes stuff for libsnooze
-import libsnooze.clib;
-import libsnooze;
-
 import core.sync.mutex : Mutex;
+import core.sync.condition : Condition;
+import core.sync.exception : SyncError;
 import std.container.slist : SList;
 import tristanable.encoding;
-import core.thread : dur;
+import core.time : Duration, dur;
 import tristanable.exceptions;
 
 version(unittest)
@@ -27,10 +25,15 @@ version(unittest)
 public class Queue
 {
     /** 
-     * The libsnooze event used to sleep/wake
-     * on queue events
+     * Mutex for the condition variable
+     */
+    private Mutex mutex;
+
+    /** 
+     * The condition variable used to sleep/wake
+     * on queue of events
      */
-    private Event event;
+    private Condition signal;
 
     /** 
      * The queue of messages
@@ -47,6 +50,15 @@ public class Queue
      */
     private ulong queueID;
 
+    /** 
+     * If a message is enqueued prior
+     * to us sleeping then we won't
+     * wake up and return for it.
+     *
+     * Therefore a periodic wakeup
+     * is required.
+     */
+    private Duration wakeInterval;
 
     /** 
      * Constructs a new Queue and immediately sets up the notification
@@ -62,14 +74,37 @@ public class Queue
         /* Initialize the queue lock */
         this.queueLock = new Mutex();
 
-        /* Initialize the event */
-        this.event = new Event();
+        /* Initialize the condition variable */
+        this.mutex = new Mutex();
+        this.signal = new Condition(this.mutex);
 
         /* Set the queue id */
         this.queueID = queueID;
 
-        /* Ensure pipe existence (see https://deavmi.assigned.network/git/deavmi/tristanable/issues/5) */
-        event.wait(dur!("seconds")(0));
+        /* Set the slumber interval */
+        this.wakeInterval = dur!("msecs")(50); // TODO: Decide on value
+    }
+
+    /** 
+     * Returns the current wake interval
+     * for the queue checker
+     *
+     * Returns: the `Duration`
+     */
+    public Duration getWakeInterval()
+    {
+        return this.wakeInterval;
+    }
+
+    /** 
+     * Sets the wake up interval
+     *
+     * Params:
+     *   interval = the new interval
+     */
+    public void setWakeInterval(Duration interval)
+    {
+        this.wakeInterval = interval;
     }
 
     /** 
@@ -111,9 +146,9 @@ public class Queue
         try
         {
             // TODO: Make us wait on the event (optional with a time-out)
-            event.notifyAll();
+            signal.notifyAll();
         }
-        catch(FatalException snozErr)
+        catch(SyncError snozErr)
         {
             // Throw an exception on a fatal exception
             throw new TristanableException(ErrorType.ENQUEUE_FAILED);
@@ -151,45 +186,25 @@ public class Queue
         /* Block till we dequeue a message successfully */
         while(dequeuedMessage is null)
         {
-            /**
-             * Call `wait()` and catch any interrupts
-             * in which case loop back and call `wait()`
-             * again
-             */
-            while(true)
+            scope(exit)
             {
-                try
-                {
-                    // TODO: Make us wait on the event (optional with a time-out)
-                    event.wait();
-                }
-                catch(InterruptedException e)
-                {
-                    version(unittest)
-                    {
-                        import std.stdio;
-                        writeln("dequeue() had libsnooze wait() get interrupted!");
-                    }
-
-                    // Retry the wait()
-                    continue;
-                }
-                catch(FatalException fatalErr)
-                {
-                    version(unittest)
-                    {
-                        import std.stdio;
-                        writeln("dequeue() had libsnooze wait() get FATALLY fail! Exception will now throw...");
-                    }
-
-                    // Throw an exception on a fatal exception
-                    throw new TristanableException(ErrorType.DEQUEUE_FAILED);
-                }
-
-                // On successful wait() wake-up exit this wait()-retry loop
-                break;
+                // Unlock the mutex
+                this.mutex.unlock();
             }
-            
+
+            // Lock the mutex
+            this.mutex.lock();
+
+            try
+            {
+                this.signal.wait(this.wakeInterval);
+            }
+            catch(SyncError e)
+            {
+                // Throw an exception on a fatal exception
+                throw new TristanableException(ErrorType.DEQUEUE_FAILED);
+            }
+
 
             /* Lock the item queue */
             queueLock.lock();