docs/plan.md

@@ -28,8 +28,8 @@ Work on ONE milestone at a time. Each milestone is one branch (`milestone/NN-nam
 
 ## Milestone 3 - CLI program (`milestone/03-cli`)
 
-- [ ] `main.py`: prompt name and numeric bid (re-prompt on invalid), bids dict kept outside the loop, "other bidders? yes/no", clear screen with newlines between bidders, announce the winner
-- [ ] `tests/test_main.py` with monkeypatched `input`
+- [x] `main.py`: prompt name and numeric bid (re-prompt on invalid), bids dict kept outside the loop, "other bidders? yes/no", clear screen with newlines between bidders, announce the winner
+- [x] `tests/test_main.py` with monkeypatched `input`
 - Verify: `pytest`; scripted run `python -m secret_auction.main` with two bidders
 
 ## Milestone 4 - Documentation (`milestone/04-docs`)

src/secret_auction/main.py

@@ -0,0 +1,60 @@
+"""! @file main.py
+@brief Command line interface for the secret auction program.
+"""
+
+import math
+
+from secret_auction import constants
+from secret_auction.auction import add_bid, find_winner
+
+
+def clear_screen() -> None:
+    """! @brief Hide previous entries by printing blank lines."""
+    print("\n" * constants.CLEAR_SCREEN_LINES)
+
+
+def ask_bid() -> float:
+    """! @brief Ask for a bid until a valid, non-negative number is entered.
+    @return The bid amount.
+    """
+    while True:
+        try:
+            amount = float(input(constants.PROMPT_BID))
+        except ValueError:
+            print(constants.MSG_INVALID_BID)
+            continue
+        if math.isfinite(amount) and amount >= 0:
+            return amount
+        print(constants.MSG_INVALID_BID)
+
+
+def ask_more_bidders() -> bool:
+    """! @brief Ask whether there are more bidders until yes/no is answered.
+    @return True if more bidders exist, False otherwise.
+    """
+    while True:
+        answer = input(constants.PROMPT_MORE_BIDDERS).strip().lower()
+        if answer in constants.YES_ANSWERS:
+            return True
+        if answer in constants.NO_ANSWERS:
+            return False
+        print(constants.MSG_INVALID_ANSWER)
+
+
+def main() -> None:
+    """! @brief Run the blind auction: collect bids, then announce the winner."""
+    print(constants.MSG_WELCOME)
+    bids: dict[str, float] = {}  # kept outside the loop so bids are not lost
+    more_bidders = True
+    while more_bidders:
+        name = input(constants.PROMPT_NAME).strip()
+        add_bid(bids, name, ask_bid())
+        more_bidders = ask_more_bidders()
+        if more_bidders:
+            clear_screen()
+    winner, amount = find_winner(bids)
+    print(constants.MSG_WINNER.format(name=winner, amount=amount))
+
+
+if __name__ == "__main__":
+    main()

tests/test_main.py

@@ -0,0 +1,35 @@
+from secret_auction import constants
+from secret_auction.main import ask_bid, ask_more_bidders, main
+
+
+def feed(monkeypatch, answers):
+    it = iter(answers)
+    monkeypatch.setattr("builtins.input", lambda _prompt="": next(it))
+
+
+def test_ask_bid_reprompts_on_invalid(monkeypatch, capsys):
+    feed(monkeypatch, ["abc", "-5", "nan", "12.5"])
+    assert ask_bid() == 12.5
+    assert capsys.readouterr().out.count(constants.MSG_INVALID_BID) == 3
+
+
+def test_ask_more_bidders(monkeypatch, capsys):
+    feed(monkeypatch, ["maybe", "Y"])
+    assert ask_more_bidders() is True
+    assert constants.MSG_INVALID_ANSWER in capsys.readouterr().out
+    feed(monkeypatch, ["no"])
+    assert ask_more_bidders() is False
+
+
+def test_main_announces_highest_bidder_and_clears_screen(monkeypatch, capsys):
+    feed(monkeypatch, ["Ann", "10", "yes", "Bob", "25.5", "yes", "Cy", "3", "no"])
+    main()
+    out = capsys.readouterr().out
+    assert "The winner is Bob with a bid of $25.50." in out
+    assert out.count("\n" * constants.CLEAR_SCREEN_LINES) == 2
+
+
+def test_main_single_bidder(monkeypatch, capsys):
+    feed(monkeypatch, ["Ann", "7", "n"])
+    main()
+    assert "The winner is Ann with a bid of $7.00." in capsys.readouterr().out