EMPTY = "."
LETTERS = "abcdefgh"
NAMES = {"b": "Black", "r": "Red"}
EXAMPLES = {"b": "b6 a5", "r": "a3 b4"}


def new_board():
    board = []
    for r in range(8):
        row = []
        for c in range(8):
            if (r + c) % 2 == 1 and r < 3:
                row.append("b")
            elif (r + c) % 2 == 1 and r > 4:
                row.append("r")
            else:
                row.append(EMPTY)
        board.append(row)
    return board


def print_board(board):
    print()
    print("    a b c d e f g h")
    for r in range(8):
        print(f" {8 - r}  " + " ".join(board[r]) + f"  {8 - r}")
    print("    a b c d e f g h")
    print()


def opponent(player):
    if player == "r":
        return "b"
    return "r"


def directions(piece):
    if piece.isupper():
        return [(-1, -1), (-1, 1), (1, -1), (1, 1)]
    if piece == "r":
        return [(-1, -1), (-1, 1)]
    return [(1, -1), (1, 1)]


def on_board(r, c):
    return 0 <= r < 8 and 0 <= c < 8


def piece_moves(board, r, c):
    steps = []
    jumps = []
    piece = board[r][c]
    enemy = opponent(piece.lower())
    for dr, dc in directions(piece):
        r1, c1 = r + dr, c + dc
        r2, c2 = r + 2 * dr, c + 2 * dc
        if not on_board(r1, c1):
            continue
        if board[r1][c1] == EMPTY:
            steps.append((r, c, r1, c1))
        elif board[r1][c1].lower() == enemy and on_board(r2, c2) and board[r2][c2] == EMPTY:
            jumps.append((r, c, r2, c2))
    return steps, jumps


def all_moves(board, player):
    steps = []
    jumps = []
    for r in range(8):
        for c in range(8):
            if board[r][c].lower() == player:
                s, j = piece_moves(board, r, c)
                steps += s
                jumps += j
    if jumps:
        return jumps
    return steps


def make_move(board, move):
    r1, c1, r2, c2 = move
    piece = board[r1][c1]
    board[r1][c1] = EMPTY
    board[r2][c2] = piece
    jumped = abs(r2 - r1) == 2
    if jumped:
        board[(r1 + r2) // 2][(c1 + c2) // 2] = EMPTY
    crowned = False
    if (piece == "r" and r2 == 0) or (piece == "b" and r2 == 7):
        board[r2][c2] = piece.upper()
        crowned = True
    return jumped, crowned


def parse_square(text):
    if len(text) != 2 or text[0] not in LETTERS or text[1] not in "12345678":
        return None
    return 8 - int(text[1]), LETTERS.index(text[0])


def parse_move(text):
    parts = text.split()
    if len(parts) != 2:
        return None
    start = parse_square(parts[0])
    end = parse_square(parts[1])
    if start is None or end is None:
        return None
    return start + end


def ask_move(player, moves):
    while True:
        text = input(f"{NAMES[player]}'s move (example: {EXAMPLES[player]}) or q to quit: ").strip().lower()
        if text == "q":
            return None
        move = parse_move(text)
        if move in moves:
            return move
        if abs(moves[0][2] - moves[0][0]) == 2:
            print("Invalid move. You have a jump available and must take it.")
        else:
            print("Invalid move. Try again.")


def count_pieces(board, player):
    total = 0
    for row in board:
        for square in row:
            if square.lower() == player:
                total += 1
    return total


def main():
    print("=== Terminal Checkers ===")
    print("Black (b) starts at the top, Red (r) at the bottom. Kings are capital letters.")
    board = new_board()
    player = "b"

    while True:
        print_board(board)
        print(f"Black pieces: {count_pieces(board, 'b')}   Red pieces: {count_pieces(board, 'r')}")
        moves = all_moves(board, player)
        if not moves:
            print(f"{NAMES[player]} has no moves left. {NAMES[opponent(player)]} wins!")
            break

        move = ask_move(player, moves)
        if move is None:
            print("Game ended.")
            break
        jumped, crowned = make_move(board, move)

        while jumped and not crowned:
            jumps = piece_moves(board, move[2], move[3])[1]
            if not jumps:
                break
            print_board(board)
            print("Another jump is available, keep going!")
            move = ask_move(player, jumps)
            if move is None:
                print("Game ended.")
                return
            jumped, crowned = make_move(board, move)

        if crowned:
            print(f"{NAMES[player]} got a king!")
        player = opponent(player)


if __name__ == "__main__":
    main()