implemented gumball machine state pattern

Author: dancergraham

chapter01_strategy/readme.md

@@ -2,7 +2,7 @@
 
 > **Strategy**: defines a family of algorithms, encapsulates each one and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
 
-<details><summary>Class Diagram</summary><p>
+<details><summary>Class Diagram (install mermaid to view)</summary><p>
 
 ```mermaid
 classDiagram

chapter10_state/gumballstate.py

@@ -0,0 +1,186 @@
+class GumballMachine:
+    def __init__(self, number_gumballs) -> None:
+        self.no_quarter_state = NoQuarterState(self)
+        self.sold_out_state = SoldOutState(self)
+        self.has_quarter_state = HasQuarterState(self)
+        self.sold_state = SoldState(self)
+        self.count = number_gumballs
+        if number_gumballs > 0:
+            self.state = self.no_quarter_state
+        else:
+            self.state = self.sold_out_state
+
+    def insert_quarter(self):
+        self.state.insert_quarter()
+
+    def eject_quarter(self):
+        self.state.eject_quarter()
+
+    def turn_crank(self):
+        self.state.turn_crank()
+        self.state.dispense()
+
+    def release_ball(self):
+        print("A gumball comes rolling out the slot...")
+        if self.count > 0:
+            self.count -= 1
+
+    def refill(self, count):
+        self.count += count
+        print(f"The gumball machine was just refilled; its new count is: {self.count}")
+        self.state.refill()
+
+    def set_state(self, state):
+        self.state = state
+
+    def __str__(self) -> str:
+        result = []
+        result.append("\nMighty Gumball, Inc.")
+        result.append("\nJava-enabled Standing Gumball Model #2004")
+        result.append(f"\nInventory: {self.count} gumball")
+        if self.count != 1:
+            result.append("s")
+
+        result.append("\n")
+        result.append(f"Machine is {self.state}\n")
+        return "".join(result)
+
+
+class State:
+    def insert_quarter(self):
+        raise NotImplementedError
+
+    def eject_quarter(self):
+        raise NotImplementedError
+
+    def turn_crank(self):
+        raise NotImplementedError
+
+    def dispense(self):
+        raise NotImplementedError
+
+    def refill(self):
+        raise NotImplementedError
+
+
+class NoQuarterState(State):
+    def __init__(self, gumball_machine: GumballMachine) -> None:
+        self.gumball_machine = gumball_machine
+
+    def insert_quarter(self):
+        print("You inserted a quarter")
+        self.gumball_machine.set_state(self.gumball_machine.has_quarter_state)
+
+    def eject_quarter(self):
+        print("You haven't inserted a quarter")
+
+    def turn_crank(self):
+        print("You turned, but there's no quarter")
+
+    def dispense(self):
+        print("You need to pay first")
+
+    def refill(self):
+        raise NotImplementedError
+
+    def __str__(self):
+        return "waiting for quarter"
+
+
+class SoldOutState(State):
+    def __init__(self, gumball_machine: GumballMachine) -> None:
+        self.gumball_machine = gumball_machine
+
+    def insert_quarter(self):
+        print("You can't insert a quarter, the machine is sold out")
+
+    def eject_quarter(self):
+        print("You can't eject, you haven't inserted a quarter yet")
+
+    def turn_crank(self):
+        print("You turned, but there are no gumballs")
+
+    def dispense(self):
+        print("No gumball dispensed")
+
+    def refill(self):
+        self.gumball_machine.set_state(self.gumball_machine.no_quarter_state)
+
+    def __str__(self):
+        return "sold out"
+
+
+class HasQuarterState(State):
+    def __init__(self, gumball_machine: GumballMachine) -> None:
+        self.gumball_machine = gumball_machine
+
+    def insert_quarter(self):
+        print("You can't insert another quarter")
+
+    def eject_quarter(self):
+        print("Quarter returned")
+        self.gumball_machine.set_state(self.gumball_machine.no_quarter_state)
+
+    def turn_crank(self):
+        print("You turned...")
+        self.gumball_machine.set_state(self.gumball_machine.sold_state)
+
+    def dispense(self):
+        print("No gumball dispensed")
+
+    def refill(self):
+        raise NotImplementedError
+
+    def __str__(self):
+        return "waiting for turn of crank"
+
+
+class SoldState(State):
+    def __init__(self, gumball_machine: GumballMachine) -> None:
+        self.gumball_machine = gumball_machine
+
+    def insert_quarter(self):
+        print("Please wait, we're already giving you a gumball")
+
+    def eject_quarter(self):
+        print("Sorry, you already turned the crank")
+
+    def turn_crank(self):
+        print("Turning twice doesn't get you another gumball!")
+
+    def dispense(self):
+        self.gumball_machine.release_ball()
+        if self.gumball_machine.count > 0:
+            self.gumball_machine.set_state(self.gumball_machine.no_quarter_state)
+        else:
+            self.gumball_machine.set_state(self.gumball_machine.sold_out_state)
+
+    def refill(self):
+        raise NotImplementedError
+
+    def __str__(self):
+        return "dispensing a gumball"
+
+
+def gumball_machine_test_drive():
+    gumball_machine = GumballMachine(2)
+    print(gumball_machine)
+    gumball_machine.insert_quarter()
+    gumball_machine.turn_crank()
+
+    print(gumball_machine)
+
+    gumball_machine.insert_quarter()
+    gumball_machine.turn_crank()
+    gumball_machine.insert_quarter()
+    gumball_machine.turn_crank()
+
+    gumball_machine.refill(5)
+    gumball_machine.insert_quarter()
+    gumball_machine.turn_crank()
+
+    print(gumball_machine)
+
+
+if __name__ == "__main__":
+    gumball_machine_test_drive()