feat(cmat): pass hints to Ex42 observers

Extend the Ex42 observer pattern with Hint objects so each
observer receives the reason for the update instead of
querying the subject:

- Subject::notify() and Observer::update() now take a
  const Hint& argument.
- Add LightHint and WaitHint carrying the traffic light
  state and WAIT button state, defined in Pelican.h.
- Pole dispatches on hint type using dynamic_cast.
- The Pole constructor sets its initial lights directly
  from the Pelican's current state, since no notification
  is sent at startup. Stopgap until the initial update
  is handled properly.

Co-authored-by: Qwen 3.8 27B <qwen3.8_27b-q3_k_xl@lmstudio.local>

cmat/Ex42/Observer.h

@@ -2,9 +2,11 @@
 #ifndef OBSERVER_H
 #define OBSERVER_H
 
+class Hint;
+
 class Observer {
   public:
-    virtual void update() = 0;
+    virtual void update(const Hint&) = 0;
 };
 
 #endif

cmat/Ex42/Pelican.cpp

@@ -2,6 +2,7 @@
 
 #include "Pelican.h"
 #include "PelicanTimer.h"
+#include "Subject.h"
 
 Pelican::Pelican() : pressed(false), RED_TIME(4), YELLOW_TIME(2), GREEN_TIME(3), FLASH_TIME(5), state(GREEN_IDLE) {
     myTimer = new PelicanTimer(*this, &Pelican::timerExpired);
@@ -12,11 +13,11 @@ void Pelican::press(void) {
         state = YELLOW_STATE;
         myTimer->timeoutRequest(YELLOW_TIME);
         pressed = true;
-        notify();
     } else if (state != RED_STATE) {
         pressed = true;
-        notify();
     }
+    notify(LightHint(state));
+    notify(WaitHint(pressed));
 }
 
 void Pelican::timerExpired(void) {
@@ -51,5 +52,6 @@ void Pelican::timerExpired(void) {
         break;
     }
 
-    notify();
+    notify(LightHint(state));
+    notify(WaitHint(pressed));
 }

cmat/Ex42/Pelican.h

@@ -48,4 +48,16 @@ class Pelican : public Subject {
     Pelican &operator=(const Pelican &);
 };
 
+class LightHint : public Hint {
+  public:
+    LightHint(Pelican::PelicanState s) : state(s) { }
+    Pelican::PelicanState state;
+};
+
+class WaitHint : public Hint {
+  public:
+    WaitHint (bool p) : pressed(p) {}
+    bool pressed;
+};
+
 #endif

cmat/Ex42/Pole.cpp

@@ -1,6 +1,9 @@
 #include "Pole.h"
+#include "Pelican.h"
 #include "Screen.h"
 
+#include <typeinfo>
+
 Pole::Pole(int x, int y, Pelican &p) : waitLight(new Light("WAIT", x + 6, y + 12, Screen::WHITE)), myPelican(p) {
     myPelican.attach(*this);
 
@@ -36,7 +39,8 @@ Pole::Pole(int x, int y, Pelican &p) : waitLight(new Light("WAIT", x + 6, y + 12
     write("_ /_________ /_      ", x, ++y, GRAY);
     write("/          /         ", x, ++y, GRAY);
 
-    update();
+    setTrafficLights(myPelican.getState());
+    setWaitLight(myPelican.isPressed());
 }
 
 Pole::~Pole() {
@@ -62,7 +66,15 @@ void Pole::setTrafficLights(Pelican::PelicanState state) {
 
 void Pole::setWaitLight(bool pressed) { waitLight->set(pressed ? Light::ON : Light::OFF); }
 
-void Pole::update() {
+void Pole::update(const Hint& hint) {
-    setTrafficLights(myPelican.getState());
+    const WaitHint* waitHintPtr;
-    setWaitLight(myPelican.isPressed());
+    waitHintPtr = dynamic_cast<const WaitHint*>(&hint);
+    const LightHint* lightHintPtr;
+    lightHintPtr = dynamic_cast<const LightHint*>(&hint);
+    if (waitHintPtr != nullptr) {
+        setWaitLight(waitHintPtr->pressed);
+    }
+    if (lightHintPtr != nullptr) {
+        setTrafficLights(lightHintPtr->state);
+    }
 }

cmat/Ex42/Pole.h

@@ -14,7 +14,7 @@ class Pole : public Observer {
     void setTrafficLights(Pelican::PelicanState state);
     void setWaitLight(bool pressed);
 
-    void update();
+    void update(const Hint& hint);
 
   private:
     Pelican &myPelican;

cmat/Ex42/Subject.cpp

@@ -5,8 +5,8 @@
 
 void Subject::attach(Observer &obs) { myObservers.insert(&obs); }
 
-void Subject::notify() const {
+void Subject::notify(const Hint& hint) const {
     for (ObsList::const_iterator iter = myObservers.begin(); iter != myObservers.end(); ++iter) {
-        (*iter)->update();
+        (*iter)->update(hint);
     }
 }

cmat/Ex42/Subject.h

@@ -7,11 +7,16 @@ class Observer;
 
 #include <set>
 
+class Hint {
+  public:
+    virtual ~Hint() = default;
+};
+
 class Subject {
   public:
     typedef std::set<Observer *> ObsList;
     void attach(Observer &obs);
-    void notify() const;
+    void notify(const Hint&) const;
 
   private:
     ObsList myObservers;