#include <stdio.h>
#include <curses.h>
#include <term.h>

/*	menu - show a menu, allowing selection by cursor movement or
	inputting a number

	menu title item [ item ]...

	If there are more than 9 items and a number 1 is input, wait for
	either a second digit or Enter

	Cater for showing in two columns if there are too many items for one

	Compiling with cc:
	cc -lcurses -o menu menu.c

*/

#define	TITLE_ROW 3
#define	TOP_ROW   5

int entries, first_x, first_y, menurows, menucols, colwidth;

int main(int argc, char *argv[])
{

	WINDOW *mywin;

	if (argc < 3) {
		printf("No menu entries supplied - should be title, entries");
		return 1;
	}

	int maxlen;
	int ch, numch, count, in_num;
	int rows, cols, x, y, key_x, key_y, curr;
	char msg[80];
	bool valid_in;
	attr_t currattr;

/*	Initialise screen */

	mywin = initscr();
	keypad( mywin, TRUE );
	start_color();
	noecho();

/*	Number of menu entries not including title */

	entries = argc - 2;

/*	Check screen size & whether we need 1, 2, or 3 cols */

	getmaxyx( mywin, rows, cols );

	if (entries > ((rows - (TOP_ROW + 2)) * 3)) {
		printf("Too many menu entries");
		return 1;
	}

	if (entries > (rows - (TOP_ROW + 2)) * 2) {
		menucols = 3;
		menurows = (entries + 2) / 3;
	}
	else if (entries > (rows - (TOP_ROW + 2))) {
		menucols = 2;
		menurows = (entries + 1) / 2;
	}
	else {
		menucols = 1;
		menurows = entries;
	}

/*	If we have colour handling, use that, otherwise underline */

	if ( ! can_change_color() ) {
		currattr = A_UNDERLINE;
	}
	else {
		init_pair(1, COLOR_CYAN, COLOR_BLACK);
		currattr = COLOR_PAIR(1);
	}

/*	What's the longest menu title? */

	colwidth = cols / menucols;
	maxlen = 0;

	for ( count = 2; count < argc; count++ ) {
		if ( strlen(argv[count]) > maxlen ) {
			maxlen = strlen(argv[count]);
		}
	}

/*	x and y for the start of the first menu entry */

/*	Allow for line no */

	first_x = (((cols / menucols) - maxlen) / 2) - 4;
	first_y = TOP_ROW - 1;

	if ( first_x < 0 ) {
		first_x = 0;
	}

/*	Write title */

	x = ((cols - strlen(argv[1])) / 2) - 1;
	y = TITLE_ROW - 1;

	wmove( mywin, y, x);

	wattron( mywin, A_REVERSE );
	wprintw( mywin, argv[1]);
	wattroff( mywin, A_REVERSE );

/*	Show all menu items */

	for ( count = 2; count < argc; count++ ) {
		curr = count - 1;
		x = get_x_for( curr );
		y = get_y_for( curr );
		mvwprintw( mywin, y++, x, "%d - %s", curr, argv[count], x );
	}

/*	Show instruction line */

	sprintf( msg, "1 - %d - choose option, Esc or Q - quit", entries );
	x = ((cols - strlen( msg )) / 2) - 1;
	y = first_y + menurows + 1;

	mvwprintw( mywin, y, x, msg );
	refresh();

/*	Position for first keypress, initialise values */

	key_x = x + strlen( msg ) + 1;
	key_y = y;

	valid_in = FALSE;
	curr = 1;
	in_num = 0;

	do {
		x = get_x_for( curr );		/* Position for menu item */
		y = get_y_for( curr );
		wattron( mywin, currattr );	/* Print curr line highlight */
		mvwprintw( mywin, y, x, "%d - %s", curr, argv[curr + 1], x );
		wattroff( mywin, currattr );
		refresh();
		ch = wgetch( mywin );
		numch = ch - '0';		/* Actual number input */
		if ( numch >= 0 && numch <= 9 ) {
			if ( in_num > 0 ) {	/* Digit already input */
				numch = numch + ( in_num * 10 );
				if ( numch <= entries ) {
					valid_in = TRUE;
					break;
				}
				else {
					mvwprintw( mywin, key_y, key_x,
						   "%d - not entry", numch );
					in_num = 0;
					continue;
				}
			}
			else {		/* Could this be first of 2 digits? */
				if ( numch <= ( entries / 10 ) ) {
					in_num = numch;
					mvwprintw( mywin, key_y, key_x,
						   "%d ", numch );
					continue;
				}
				if ( numch > 0 && numch <= entries ) {
					valid_in = TRUE;
					break;
				}
			}
		}
		mvwprintw( mywin, key_y, key_x, "              " );
		switch( ch ) {
		case 'Q' :
		case 'q' :
		case 27 :
			valid_in = TRUE;
			numch = 0;
			break;
		case 10 :			/* Enter key */
			if ( in_num > 0 ) {	/* Number's been input */
				numch = in_num;
				in_num = 0;
				if ( numch > entries ) {
					continue;
				}
			}
			else {			/* Select current line */
				numch = curr;
			}
			ch = '0' + numch;	/* Convert to ASCII number */
			valid_in = TRUE;
			break;
		case KEY_DOWN :
			if ( curr < entries ) {
				mvwprintw( mywin, y, x, "%d - %s", curr,
					argv[curr + 1] );
				curr++;
			}
			break;
		case KEY_UP :
			if ( curr > 1 ) {
				mvwprintw( mywin, y, x, "%d - %s", curr,
					argv[curr + 1] );
				curr--;
			}
			break;
		case KEY_LEFT :
			if ( menucols > 1 && curr > menurows ) {
				mvwprintw( mywin, y, x, "%d - %s", curr,
					argv[curr + 1] );
				curr = curr - menurows;
			}
			break;
		case KEY_RIGHT :
			if ( menucols > 1 && ( curr + menurows <= entries ) ) {
				mvwprintw( mywin, y, x, "%d - %s", curr,
					argv[curr + 1] );
				curr = curr + menurows;
			}
			break;
/*		default :
			mvwprintw( mywin, 23, 10, "%d", ch );
*/
		}
	} while ( ! valid_in );

	wclear( mywin );

	refresh();
	endwin();
	return numch;
}

int get_x_for ( int entry )
{

	int x, col;

	col = (entry - 1) / menurows;	/* col starts at 0 for simplicity */

	if ( entries > 9 && entry < 10 ) {
		x = first_x + 1;	/* Offset right if 1 digit */
	}
	else {
		x = first_x;
	}

	x = x + (col * colwidth);

	return x;
}

int get_y_for ( int entry )
{

	int y, col;

	col = (entry - 1) / menurows;	/* col starts at 0 for simplicity */

	y = (first_y - 1) + entry;

	y = y - (col * menurows);

	return y;
}