Connect Four game engine with win detection

Implement a two-player game of Connect Four.

The board has rows rows and cols columns (default 6 x 7). Players "A" and "B" alternate turns, and "A" moves first. On a turn, a player picks a column and drops a disc into it. The disc falls to the lowest empty cell in that column. A player wins by getting k (default 4) of their discs in an unbroken line: horizontal, vertical, or along either diagonal. If every cell is filled and nobody has won, the game is a draw.

Implement the class:

• ConnectFour(rows: int = 6, cols: int = 7, k: int = 4) creates an empty board.
• move(player: str, column: int) -> str drops player's disc into column (0-indexed, left to right) and returns the game state after the move:
  • "A" or "B" if that move wins the game,
  • "draw" if the board is now full with no winner,
  • "in_progress" otherwise.

move must raise ValueError, and leave the game unchanged, when:

• the game has already ended,
• it is not player's turn,
• column is outside 0 .. cols - 1, or
• the column is already full.

Aim for each move to take time proportional to k, not to the board size.

Example 1

g = ConnectFour()
g.move("A", 2)  # "in_progress"
g.move("B", 2)  # "in_progress"  (B's disc lands on top of A's)
g.move("A", 3)  # "in_progress"
g.move("B", 3)  # "in_progress"
g.move("A", 5)  # "in_progress"
g.move("B", 5)  # "in_progress"
g.move("A", 4)  # "A"  -> bottom row now holds A in columns 2, 3, 4, 5
g.move("B", 0)  # raises ValueError (game is over)

Example 2

g = ConnectFour(rows=2, cols=2, k=3)
g.move("A", 0)  # "in_progress"
g.move("B", 1)  # "in_progress"
g.move("A", 1)  # "in_progress"
g.move("B", 0)  # "draw"  (no line of 3 fits on a 2 x 2 board)

Constraints

• 1 <= rows, cols <= 100, 1 <= k <= max(rows, cols)
• At most rows * cols successful calls to move.