Implement coffee machine core for MIL-002

Add the menu, coin values, starting resources and message texts to
constants.py. Implement report, is_resource_sufficient, process_coins,
is_transaction_successful, make_coffee and the main loop. Money is
counted in whole cents. The smoke test now feeds "off" so the loop
exits.

Closes #6
Closes #7
Closes #8
Closes #9
Closes #10
Closes #11
Closes #12

Task: MIL-002#1
Task: MIL-002#2
Task: MIL-002#3
Task: MIL-002#4
Task: MIL-002#5
Task: MIL-002#6
Task: MIL-002#7

README.md

@@ -1,2 +1,102 @@
-# 015-coffee_machine
+# Coffee Machine
 
+A console game from Udemy's *100 Days of Code: The Complete Python Pro Bootcamp*
+(day 15). A virtual coffee machine serves espresso, latte and cappuccino. Pay with
+US coins (quarters, dimes, nickels and pennies). The machine checks its water, milk
+and coffee before it serves, refunds you if you pay too little and gives change if
+you pay too much.
+
+```
+What would you like? (espresso/latte/cappuccino): latte
+Please insert coins.
+How many quarters?: 10
+How many dimes?: 0
+How many nickels?: 0
+How many pennies?: 0
+Here is your latte. Enjoy!
+```
+
+- Python 3.13 or newer, no runtime dependencies.
+- Type `report` to see the water, milk, coffee and money in the machine, and `off`
+  to switch the machine off.
+- The function names follow the assignment: `is_resource_sufficient`,
+  `process_coins`, `is_transaction_successful`, `make_coffee`.
+- Money is counted in whole cents inside the program, so change is never off by a
+  rounding error.
+
+## Requirements
+
+- [Python](https://www.python.org/downloads/) 3.13 or newer
+- Optional: [Doxygen](https://www.doxygen.nl/) to build the source documentation
+
+## Set up
+
+Create a local virtual environment in `.venv`, activate it, and upgrade `pip`.
+
+Windows (PowerShell):
+
+```powershell
+python -m venv .venv
+.venv\Scripts\Activate.ps1
+python -m pip install --upgrade pip
+```
+
+Windows (Git Bash), Linux and macOS:
+
+```bash
+python -m venv .venv
+source .venv/Scripts/activate   # Linux/macOS: source .venv/bin/activate
+python -m pip install --upgrade pip
+```
+
+The machine itself needs nothing more. To run the tests and the code checks, install
+the development tools:
+
+```bash
+python -m pip install -e ".[dev]"
+```
+
+## Run the coffee machine
+
+```bash
+python -m coffee_machine
+```
+
+Type `espresso`, `latte` or `cappuccino` and press Enter, then enter the coins.
+Type `report` for the machine's resources, or `off` to quit.
+
+## Run the tests
+
+```bash
+python -m pytest
+```
+
+Check the code style and types:
+
+```bash
+python -m ruff check src tests
+python -m ruff format --check src tests
+python -m mypy src tests
+```
+
+## Build the source documentation
+
+The source uses Doxygen comments. The HTML output goes to `docs/doxygen/html`.
+
+```bash
+doxygen Doxyfile
+```
+
+## Project layout
+
+| Path | Content |
+| --- | --- |
+| `src/coffee_machine/` | The machine: `main.py` (the loop), `constants.py` (menu, coins, starting resources) |
+| `tests/` | pytest tests |
+| `docs/` | Planning and review documents (business case, plan, milestones) |
+| `pyproject.toml` | Project configuration |
+| `Doxyfile` | Doxygen configuration |
+
+## License
+
+GNU Affero General Public License v3.0. See [LICENSE](LICENSE).

src/coffee_machine/constants.py

@@ -1,6 +1,54 @@
 """!
 @file constants.py
-@brief Constants for the coffee machine: menu, coins and starting resources.
+@brief Constants for the coffee machine: menu, coins, starting resources, texts.
 
-The values are added in MIL-002 ("Define constants").
+Money is stored in whole cents so that sums and change are exact.
 """
+
+from typing import TypedDict
+
+
+class Drink(TypedDict):
+    """!
+    @brief A menu entry: the ingredients it needs and its price.
+    """
+
+    ingredients: dict[str, int]
+    cost: int
+
+
+MENU: dict[str, Drink] = {
+    "espresso": {"ingredients": {"water": 50, "coffee": 18}, "cost": 150},
+    "latte": {
+        "ingredients": {"water": 200, "milk": 150, "coffee": 24},
+        "cost": 250,
+    },
+    "cappuccino": {
+        "ingredients": {"water": 250, "milk": 100, "coffee": 24},
+        "cost": 300,
+    },
+}
+
+## Value of each US coin in cents, in the order the machine asks for them.
+COIN_VALUES: dict[str, int] = {
+    "quarters": 25,
+    "dimes": 10,
+    "nickels": 5,
+    "pennies": 1,
+}
+
+INITIAL_RESOURCES: dict[str, int] = {"water": 300, "milk": 200, "coffee": 100}
+
+## Unit printed after each resource in the report.
+RESOURCE_UNITS: dict[str, str] = {"water": "ml", "milk": "ml", "coffee": "g"}
+
+CENTS_PER_DOLLAR = 100
+
+COMMAND_REPORT = "report"
+COMMAND_OFF = "off"
+
+PROMPT_ORDER = "What would you like? (espresso/latte/cappuccino): "
+MESSAGE_INSERT_COINS = "Please insert coins."
+MESSAGE_NOT_ENOUGH_MONEY = "Sorry that's not enough money. Money refunded."
+MESSAGE_UNKNOWN_DRINK = "Sorry, we do not serve that."
+MESSAGE_INVALID_NUMBER = "Please enter a whole number of coins, zero or more."

src/coffee_machine/main.py

@@ -1,12 +1,138 @@
 """!
 @file main.py
-@brief Entry point of the coffee machine.
+@brief Entry point and logic of the coffee machine.
 """
 
+from coffee_machine.constants import (
+    CENTS_PER_DOLLAR,
+    COIN_VALUES,
+    COMMAND_OFF,
+    COMMAND_REPORT,
+    INITIAL_RESOURCES,
+    MENU,
+    MESSAGE_INSERT_COINS,
+    MESSAGE_INVALID_NUMBER,
+    MESSAGE_NOT_ENOUGH_MONEY,
+    MESSAGE_UNKNOWN_DRINK,
+    PROMPT_ORDER,
+    RESOURCE_UNITS,
+)
+
+
+def format_money(cents: int) -> str:
+    """!
+    @brief Format an amount in cents as dollars.
+    @param cents Amount in whole cents.
+    @return The amount such as "$2.50".
+    """
+    return f"${cents / CENTS_PER_DOLLAR:.2f}"
+
+
+def report(resources: dict[str, int], profit: int) -> None:
+    """!
+    @brief Print the resources left in the machine and the money earned.
+    @param resources Remaining amount of each resource.
+    @param profit Money earned so far, in cents.
+    """
+    for name, amount in resources.items():
+        print(f"{name.capitalize()}: {amount}{RESOURCE_UNITS[name]}")
+    print(f"Money: {format_money(profit)}")
+
+
+def is_resource_sufficient(
+    order_ingredients: dict[str, int], resources: dict[str, int]
+) -> bool:
+    """!
+    @brief Check that the machine has enough of every ingredient for an order.
+    @param order_ingredients Amount of each ingredient the drink needs.
+    @param resources Remaining amount of each resource.
+    @return True if every ingredient is available, otherwise False after
+            printing the first missing one.
+    """
+    for name, needed in order_ingredients.items():
+        if needed > resources[name]:
+            print(f"Sorry there is not enough {name}.")
+            return False
+    return True
+
+
+def _ask_coin_count(coin_name: str) -> int:
+    """!
+    @brief Ask how many coins of one kind are inserted, until the answer is valid.
+    @param coin_name Plural coin name, such as "quarters".
+    @return The number of coins, zero or more.
+    """
+    while True:
+        answer = input(f"How many {coin_name}?: ")
+        try:
+            count = int(answer)
+        except ValueError:
+            count = -1
+        if count >= 0:
+            return count
+        print(MESSAGE_INVALID_NUMBER)
+
+
+def process_coins() -> int:
+    """!
+    @brief Ask for the coins and total their value.
+    @return The total inserted, in cents.
+    """
+    print(MESSAGE_INSERT_COINS)
+    return sum(
+        _ask_coin_count(coin_name) * value for coin_name, value in COIN_VALUES.items()
+    )
+
+
+def is_transaction_successful(money_received: int, drink_cost: int) -> bool:
+    """!
+    @brief Check the payment, refund it if too small, otherwise give change.
+    @param money_received Money inserted, in cents.
+    @param drink_cost Price of the drink, in cents.
+    @return True if the payment covers the price, otherwise False.
+    """
+    if money_received < drink_cost:
+        print(MESSAGE_NOT_ENOUGH_MONEY)
+        return False
+    change = money_received - drink_cost
+    if change > 0:
+        print(f"Here is {format_money(change)} in change.")
+    return True
+
+
+def make_coffee(
+    drink_name: str, order_ingredients: dict[str, int], resources: dict[str, int]
+) -> None:
+    """!
+    @brief Use up the drink's ingredients and serve it.
+    @param drink_name Name of the drink.
+    @param order_ingredients Amount of each ingredient the drink needs.
+    @param resources Remaining amount of each resource; updated in place.
+    """
+    for name, needed in order_ingredients.items():
+        resources[name] -= needed
+    print(f"Here is your {drink_name}. Enjoy!")
+
 
 def main() -> None:
     """!
-    @brief Run the coffee machine.
+    @brief Run the coffee machine until the user types "off".
-
-    The ordering loop is added in MIL-002 ("Implement main loop").
     """
+    resources = dict(INITIAL_RESOURCES)
+    profit = 0
+    while True:
+        choice = input(PROMPT_ORDER).strip().lower()
+        if choice == COMMAND_OFF:
+            return
+        if choice == COMMAND_REPORT:
+            report(resources, profit)
+        elif choice in MENU:
+            drink = MENU[choice]
+            if not is_resource_sufficient(drink["ingredients"], resources):
+                continue
+            payment = process_coins()
+            if is_transaction_successful(payment, drink["cost"]):
+                profit += drink["cost"]
+                make_coffee(choice, drink["ingredients"], resources)
+        else:
+            print(MESSAGE_UNKNOWN_DRINK)

tests/test_smoke.py

@@ -3,11 +3,14 @@
 @brief Smoke test that the package imports.
 """
 
+import pytest
+
 from coffee_machine import main as main_module
 
 
-def test_main_is_callable() -> None:
+def test_main_is_callable(monkeypatch: pytest.MonkeyPatch) -> None:
     """!
-    @brief The entry point runs without error.
+    @brief The entry point starts and stops on "off".
     """
+    monkeypatch.setattr("builtins.input", lambda _prompt: "off")
     main_module.main()