From 3b5a291de9f4d82025b1a72574bef3668933fa3d Mon Sep 17 00:00:00 2001
From: Dominique FOURNIER <dominique.fournier@grenoble.cnrs.fr>
Date: Wed, 21 Jul 2021 16:11:43 +0200
Subject: [PATCH] Add StateMachine support

---
 src/StateMachine.php | 131 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 src/StateMachine.php

diff --git a/src/StateMachine.php b/src/StateMachine.php
new file mode 100644
index 0000000..2b67c37
--- /dev/null
+++ b/src/StateMachine.php
@@ -0,0 +1,131 @@
+<?php
+/** DomFramework
+  * @package domframework
+  * @author Dominique Fournier <dominique@fournier38.fr>
+  * @license BSD
+  */
+
+namespace Domframework;
+
+/**
+ * This class manage a state machine.
+ * Define the states and the associated transitions.
+ * The states and the transitions are methods
+ * The states are the actions.
+ * The transitions are tests : return false if the test do not match, or true
+ * if the test match. The state machine will skip the test if it doesn't match,
+ * and go to the define toStateName if the test return true.
+ * Officially, the transitions should not have priority. In practise, the
+ * transistions are tested in the added order.
+ */
+class StateMachine
+{
+    private $states = array();
+    private $transitions = array();
+    private $debug = false;
+
+    public function addState(string $stateName, callable $methodName): self
+    {
+        $this->states[$stateName] = new StateMachineState($methodName);
+        return $this;
+    }
+
+    public function addTransition(string $transitionName, string $fromStateName, string $toStateName, callable $methodName): self
+    {
+        if (! key_exists($fromStateName, $this->states))
+            throw new \Exception("StateMachine can not add Transition from '$fromStateName' : state not defined", 404);
+        if (! key_exists($toStateName, $this->states))
+            throw new \Exception("StateMachine can not add Transition to '$toStateName' : state not defined", 404);
+        if (key_exists($transitionName, $this->transitions))
+            throw new \Exception("StateMachine can not add Transition '$transitionName' : transition already defined", 406);
+        $this->transitions[$transitionName] = new StateMachineTransition($fromStateName, $toStateName, $methodName);
+        return $this;
+    }
+
+    /**
+     * Start the state machine at the provided state
+     * Will run until no transition match, then return
+     */
+    public function run(string $stateName)
+    {
+        if (! key_exists ($stateName, $this->states))
+            throw new \Exception("StateMachine can not runState '$stateName' : state not defined", 404);
+        while(1)
+        {
+            $this->debug("Start state '$stateName'");
+            $rc = $this->states[$stateName]->run();
+            $this->debug("End state '$stateName' with type '".gettype($rc)."'");
+            foreach($this->transitions as $transitionName => $transition)
+            {
+                if ($transition->getFromStateName() !== $stateName)
+                    continue;
+                if ($transition->run() === false)
+                {
+                    $this->debug("Look at transition '$transitionName' : Return FALSE (not match)");
+                    continue;
+                }
+                $this->debug("Look at transition '$transitionName' : Match");
+                $stateName = $transition->getToStateName();
+                continue 2;
+            }
+            break;
+        }
+        return $rc;
+    }
+
+    private function debug(string $msg)
+    {
+        if ($this->debug === false)
+            return;
+        echo "$msg\n";
+    }
+}
+
+class StateMachineState
+{
+    private $methodName;
+
+    public function __construct(callable $methodName)
+    {
+        $this->methodName = $methodName;
+    }
+
+    public function run()
+    {
+        return call_user_func($this->methodName);
+    }
+}
+
+class StateMachineTransition
+{
+    private $fromStateName;
+    private $toStateName;
+    private $methodName;
+
+    public function __construct(string $fromStateName, string $toStateName, callable $methodName)
+    {
+        $this->fromStateName = $fromStateName;
+        $this->toStateName = $toStateName;
+        $this->methodName = $methodName;
+    }
+
+    public function getFromStateName(): string
+    {
+        return $this->fromStateName;
+    }
+
+    public function getToStateName(): string
+    {
+        return $this->toStateName;
+    }
+
+    public function getMethodName(): callable
+    {
+        return $this->methodName;
+    }
+
+    public function run()
+    {
+        return call_user_func($this->methodName);
+    }
+}