B/timet: Time Template.
 
@Purpose: Support for parsing and printing times of day.
 
@-------------------------------------------------------------------------------

@p Rounding.
The following rounds a numerical value |t1| to the nearest unit of |t2|;
for instance, if |t2| is 5 then it rounds to the nearest 5.

@c
[ RoundOffTime t1 t2; return ((t1+t2/2)/t2)*t2; ];

@p Square Root.
This is an old algorithm for extracting binary square roots, taking 2 bits
at a time. We start out with |one| at the highest bit which isn't the sign
bit; that used to be worked out as |WORD_HIGHBIT/2|, but this caused unexpected
portability problems (exposing a minor bug in Inform and also glulxe) because
of differences in how C compilers handle signed division of constants in the
case where the dividend is $-2^{31}$, the unique number which cannot be negated
in 32-bit twos complement arithmetic.

@c
[ SquareRoot num
	op res one;
	op = num;
	if (num < 0) { RunTimeProblem(RTP_NEGATIVEROOT); return 1; }
	! "one" starts at the highest power of four <= the argument.
	for (one = WORD_NEXTTOHIGHBIT: one > op: one = one/4) ;

	while (one ~= 0) {
		!print "Round: op = ", op, " res = ", res, ", res**2 = ", res*res, " one = ", one, "^";
		if (op >= res + one) {
			op = op - res - one;
			res = res + one*2;
		}
		res = res/2;
		one = one/4;
	}
	!print "Res is ", res, "^";
	return res;
];

@p Cube Root.
The following is an iterative scheme for finding cube roots by
Newton-Raphson approximation, not a great method but which, on the narrow
ranges of integers we deal with, is good enough. The square root is used
only as a sighting shot.

@c
[ CubeRoot num x y n;
	if (num < 0) x = -SquareRoot(-num); else x = SquareRoot(num);
	for (n=0: (y ~= x) && (n++ < 100): y = x, x = (2*x + num/x/x)/3) ;
	return x;
];

@p Digital Printing.
For instance, ``2:06 am''.

@c
[ PrintTimeOfDay t h aop;
	if (t<0) { print "<no time>"; return; }
	if (t >= TWELVE_HOURS) { aop = "pm"; t = t - TWELVE_HOURS; } else aop = "am";
	h = t/ONE_HOUR; if (h==0) h=12;
	print h, ":";
	if (t%ONE_HOUR < 10) print "0"; print t%ONE_HOUR, " ", (string) aop;
];

@p Analogue Printing.
For instance, ``six minutes past two''.

@c
[ PrintTimeOfDayEnglish t h m dir aop;
	h = (t/ONE_HOUR) % 12; m = t%ONE_HOUR; if (h==0) h=12;
	if (m==0) { print (number) h, " o'clock"; return; }
	dir = "past";
	if (m > HALF_HOUR) { m = ONE_HOUR-m; h = (h+1)%12; if (h==0) h=12; dir = "to"; }
	switch(m) {
		QUARTER_HOUR: print "quarter"; HALF_HOUR: print "half";
		default: print (number) m;
		    if (m%5 ~= 0) {
				if (m == 1) print " minute"; else print " minutes";
		    }
	}
	print " ", (string) dir, " ", (number) h;
];

@p Understanding.
This I6 grammar token converts words in the player's command to a valid
I7 time, and is heavily based on the one presented as a solution to an
exercise in the DM4.

@c
[ TIME_TOKEN first_word second_word at length flag
	illegal_char offhour hr mn i original_wn;
	original_wn = wn;
{-call:Plugins::Parsing::Tokens::Values::time}
	wn = original_wn;
	first_word = NextWordStopped();
	switch (first_word) {
		'midnight': parsed_number = 0; return GPR_NUMBER;
		'midday', 'noon': parsed_number = TWELVE_HOURS;
		return GPR_NUMBER;
	}
	! Next try the format 12:02
	at = WordAddress(wn-1); length = WordLength(wn-1);
	for (i=0: i<length: i++) {
		switch (at->i) {
			':': if (flag == false && i>0 && i<length-1) flag = true;
			else illegal_char = true;
			'0', '1', '2', '3', '4', '5', '6', '7', '8', '9': ;
			default: illegal_char = true;
		}
	}
	if (length < 3 || length > 5 || illegal_char) flag = false;
	if (flag) {
		for (i=0: at->i~=':': i++, hr=hr*10) hr = hr + at->i - '0';
		hr = hr/10;
		for (i++: i<length: i++, mn=mn*10) mn = mn + at->i - '0';
		mn = mn/10;
		second_word = NextWordStopped();
		parsed_number = HoursMinsWordToTime(hr, mn, second_word);
		if (parsed_number == -1) return GPR_FAIL;
		if (second_word ~= 'pm' or 'am') wn--;
		return GPR_NUMBER;
	}
	! Lastly the wordy format
	offhour = -1;
	if (first_word == 'half') offhour = HALF_HOUR;
	if (first_word == 'quarter') offhour = QUARTER_HOUR;
	if (offhour < 0) offhour = TryNumber(wn-1);
	if (offhour < 0 || offhour >= ONE_HOUR) return GPR_FAIL;
	second_word = NextWordStopped();
	switch (second_word) {
		! "six o'clock", "six"
		'o^clock', 'am', 'pm', -1:
			hr = offhour; if (hr > 12) return GPR_FAIL;
		! "quarter to six", "twenty past midnight"
		'to', 'past':
			mn = offhour; hr = TryNumber(wn);
			if (hr <= 0) {
				switch (NextWordStopped()) {
					'noon', 'midday': hr = 12;
					'midnight': hr = 0;
					default: return GPR_FAIL;
				}
			}
			if (hr >= 13) return GPR_FAIL;
			if (second_word == 'to') {
				mn = ONE_HOUR-mn; hr--; if (hr<0) hr=23;
			}
			wn++; second_word = NextWordStopped();
		! "six thirty"
		default:
			hr = offhour; mn = TryNumber(--wn);
			if (mn < 0 || mn >= ONE_HOUR) return GPR_FAIL;
			wn++; second_word = NextWordStopped();
	}
	parsed_number = HoursMinsWordToTime(hr, mn, second_word);
	if (parsed_number < 0) return GPR_FAIL;
	if (second_word ~= 'pm' or 'am' or 'o^clock') wn--;
	return GPR_NUMBER;
];

[ HoursMinsWordToTime hour minute word x;
	if (hour >= 24) return -1;
	if (minute >= ONE_HOUR) return -1;
	x = hour*ONE_HOUR + minute; if (hour >= 13) return x;
	x = x % TWELVE_HOURS; if (word == 'pm') x = x + TWELVE_HOURS;
	if (word ~= 'am' or 'pm' && hour == 12) x = x + TWELVE_HOURS;
	return x;
];

@p Relative Time Token.
``Time'' is an interesting kind of value since it can hold two conceptually
different ways of thinking about time: absolute times, such as ``12:03 PM'',
and also relative times, like ``ten minutes''. For parsing purposes, these
are completely different from each other, and the time token above handles
only absolute times; we need the following for relative ones.

@c
[ RELATIVE_TIME_TOKEN first_word second_word offhour mult mn original_wn;
	original_wn = wn;
	wn = original_wn;
	
	first_word = NextWordStopped(); wn--;
	if (first_word == 'an' or 'a//') mn=1; else mn=TryNumber(wn);
	
    if (mn == -1000) {
		first_word = NextWordStopped();
		if (first_word == 'half') offhour = HALF_HOUR;
		if (first_word == 'quarter') offhour = QUARTER_HOUR;
		if (offhour > 0) {
			second_word = NextWordStopped();
			if (second_word == 'of') second_word = NextWordStopped();
			if (second_word == 'an') second_word = NextWordStopped();
			if (second_word == 'hour') {
				parsed_number = offhour;
				return GPR_NUMBER;
			}
		}
		return GPR_FAIL;
    }
	wn++;
	
	first_word = NextWordStopped();
	switch (first_word) {
		'minutes', 'minute': mult = 1;
		'hours', 'hour': mult = 60;
		default: return GPR_FAIL;
	}
	parsed_number = mn*mult;
	if (mult == 60) {
		mn=TryNumber(wn);
		if (mn ~= -1000) {
			wn++;
			first_word = NextWordStopped();
			if (first_word == 'minutes' or 'minute')
				parsed_number = parsed_number + mn;
			else wn = wn - 2;
		}
	}
	return GPR_NUMBER;
];

@p During Scene Matching.

@c
[ DuringSceneMatching prop sc;
	for (sc=0: sc<NUMBER_SCENES_CREATED: sc++)
		if ((scene_status-->sc == 1) && (prop(sc+1))) rtrue;
	rfalse;
];

@p Scene Questions.

@c
[ SceneUtility sc task;
	if (sc <= 0) return 0;
	if (task == 1 or 2) {
		if (scene_endings-->(sc-1) == 0) return RunTimeProblem(RTP_SCENEHASNTSTARTED, sc);
	} else {
		if (scene_endings-->(sc-1) <= 1) return RunTimeProblem(RTP_SCENEHASNTENDED, sc);
	}
	switch (task) {
		1: return (the_time - scene_started-->(sc-1))%(TWENTY_FOUR_HOURS);
		2: return scene_started-->(sc-1);
		3: return (the_time - scene_ended-->(sc-1))%(TWENTY_FOUR_HOURS);
		4: return scene_ended-->(sc-1);
	}
];