/* --------------------------------------------------------------------------------------------*/

/* PRINT BOARD FUNCTIONS */
show_board(board(X)):- write("+---+---+---+---+---+---+---+"), nl,
					   show(X,0),
					   print_columns_number.

/* Start at row 0 to 5 */
show(_,6).
show(A,N):- write("| "), print_row(A,B),
			nl,
			M is N + 1,
			show(B, M).

/* Print the first element of every column */
print_row([],_) :- nl, write("+---+---+---+---+---+---+---+").
print_row([[A|B]|C],[B|D]):- print_square(A), write(' | '), print_row(C,D).

print_square(A) :- (A == '-') -> write(" "); write(A).

/* Show number of the columns */
print_columns_number :- write('| 1 | 2 | 3 | 4 | 5 | 6 | 7 |').

/* -----------------------------------------------------------------------------------------*/

/* OPERATIONS */
/*  Validate player entry */
column(1).
column(2).
column(3).
column(4).
column(5).
column(6).
column(7).
column(_) :- write('Invalid column number.'), nl, nl, enter_column_number(_).
enter_column_number(X) :- nl,
						  write("*---------------------------*"), nl, write("|                           |"), nl,
						  write('| Enter a column number :   |'), nl,
						  read(N),
						  write("|                           |"), nl,
						  write("*---------------------------*"), nl,
						  nl, column(N), X is N.