wflashcard

#!/bin/sh -e

minweight=0.01
penalty=1.75
quick=3
quickreward=4.0
review=0
reviewreward=1.05
reward=1.75

help() {
	cat - >&2 <<EOF
wflashcard - weighted flashcard viewer

wflashcard [-v] [-p penalty] [-r reward] [-q quickreward] [-s quick] [-m minweight] [-w reviewreward] files...

The file format is tab separated where the (optional) first field is the 
weight, the second field is the "front" of the flashcard (shown to the 
user), and the third field is the "back" of the flashcard (the expected 
answer). If the weight is omitted then it will be set to 1.0. Blank 
lines and comment lines are valid.

Incorrect answers will have their weight multiplied by "penalty", 
correct answers will have their weight divided by "reward", quick & 
correct (answered in <= "quick" seconds) answers will have their weight 
divided by "quickreward", and the minimum weight will be "minweight".

The -v flag enables review mode, which shows the front and back of each 
flashcard and ignores answers. A small reward is given upon review by 
default, this can be configured with the -w flag.

The defaults for these options are:
penalty=$penalty
reward=$reward
quickreward=$quickreward
quick=$quick
minweight=$minweight
reviewreward=$reviewreward
EOF
}

while getopts 'm:p:q:r:s:vw:h' o; do
	case "$o" in
		m) minweight="$OPTARG" ;;
		p) penalty="$OPTARG" ;;
		q) quickreward="$OPTARG" ;;
		r) reward="$OPTARG" ;;
		s) quick="$OPTARG" ;;
		v) review=1 ;;
		w) reviewreward="$OPTARG" ;;
		h) help; exit 0 ;;
		*) help; exit 1 ;;
	esac
done
shift $((OPTIND-1))

awk -F "$(printf '\t')" -v tty="$(tty)" \
	-v minweight="$minweight" \
	-v penalty="$penalty" \
	-v quick="$quick" \
	-v quickreward="$quickreward" \
	-v review="$review" \
	-v reviewreward="$reviewreward" \
	-v reward="$reward" \
'
function emphatic(s) { printf("\n----------------\n%s\n----------------\n\n", s) }
function basename(s) { sub("/$", "", s); gsub(".*/", "", s); return s; }

BEGIN { OFS = FS }

# skip comments and blank lines
/^$/ || /^#/ { rawline[NR] = $0; filename[NR] = FILENAME; next }

$1 == "" || $2 == "" {
	print "Invalid flashcard on line " NR > "/dev/stderr"
	rawline[NR] = $0; filename[NR] = FILENAME
	next
}

$3 == "" { $3 = $2; $2 = $1; $1 = 1; } # set missing weight to 1

{ sum += weight[NR] = $1; front[NR] = $2; back[NR] = $3; filename[NR] = FILENAME; }

END {
	if (sum == 0) {
		print "Sum of weights is zero" > "/dev/stderr"
		exit
	}

	if (review && tty != "not a tty")
		print "/quit to exit" > "/dev/stderr"

	srand()
	while (1) {
		target = rand() * sum
		isum = 0
		for (i = 1; i <= NR; i++)
			if (weight[i] && target <= (isum += weight[i]))
				break

		if (review)
			printf("%s: %s\t%s\n", basename(filename[i]), front[i], back[i])
		else
			printf("%s: %s\n", basename(filename[i]), front[i])

		if (tty != "not a tty")
			printf("> ")

		srand(); time = srand()
		response = ""; getline response < tty;
		srand(); response_time = srand() - time
		if (review) {
			new_weight = weight[i] / reviewreward
		} else if (response == "" || response == "/quit") {
			new_weight = weight[i]
			break
		} else if (response == back[i] && response_time <= quick) {
			new_weight = weight[i] / quickreward
			emphatic("Correct!")
		} else if (response == back[i]) {
			new_weight = weight[i] / reward
			emphatic("Correct!")
		} else {
			emphatic("The correct answer was " back[i] ". Were you correct? (y/N)")
			printf("> ")
			response = ""; getline response < tty;
			if (response == "y" || response == "Y")
				new_weight = weight[i] / reward
			else
				new_weight = weight[i] * penalty
		}
		if (new_weight < minweight)
			new_weight = minweight
		updatew = new_weight - weight[i]
		weight[i] = new_weight
		sum += updatew

		if (response == "/quit" || tty == "not a tty")
			break
	}

	for (i = 1; i <= NR; i++) {
		if (weight[i])
			print weight[i], front[i], back[i] > filename[i]
		else
			print rawline[i] > filename[i]
	}
}' "$@"